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  • 1.
    Abdalla, Munir A
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Fröjdh, Christer
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Petersson, Sture
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    A CMOS APS for dental X-ray imaging using scintillating sensors2001Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 460, nr 1, s. 197-203Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper we present an integrating CMOS Active Pixel Sensor (APS) circuit to be used with scintillator type X-ray sensors for intra oral dental X-ray imaging systems. Different pixel architectures were constructed to explore their performance characteristics and to study the feasibility of the development of such systems using the CMOS technology. A prototype 64×80 pixel array has been implemented in a CMOS 0.8 μm double poly n-well process with a pixel pitch of 50 μm. A spectral sensitivity measurement for the different pixels topologies, as well as measured X-ray direct absorption in the different APSs are presented. A measurement of the output signal showed a good linearity over a wide dynamic range. This chip showed that the very low sensitivity of the CMOS APSs to direct X-ray exposure adds a great advantage to the various CMOS advantages over CCD-based imaging systems.

  • 2.
    Abdalla, Munir A
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Fröjdh, Christer
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Petersson, Sture
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    An integrating CMOS APS for X-ray imaging with an in-pixel preamplifier2001Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 466, nr 1, s. 232-236Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present in this paper an integrating CMOS Active Pixel Sensor (APS) circuit coated with scintillator type sensors for intra-oral dental X-ray imaging systems. The photosensing element in the pixel is formed by the p-diffusion on the n-well diode. The advantage of this photosensor is its very low direct absorption of X-rays compared to the other available photosensing elements in the CMOS pixel. The pixel features an integrating capacitor in the feedback loop of a preamplifier of a finite gain in order to increase the optical sensitivity. To verify the effectiveness of this in-pixel preamplification, a prototype 32 x 80 element CMOS active pixel array was implemented in a 0.8 mum CMOS double poly, n-well process with a pixel pitch of 50 mum. Measured results confirmed the improved optical sensitivity performance of the APS. Various measurements on device performance are presented.

  • 3.
    Allahgholi, Aschkan
    et al.
    Deutsches Elektronensynchrotron - DESY, Hamburg, Germany.
    Becker, Julian
    Deutsches Elektronensynchrotron - DESY, Hamburg, Germany.
    Delfs, Annette
    Deutsches Elektronensynchrotron - DESY, Hamburg, Germany.
    Dinapoli, Roberto
    Paul Scherrer Institut - PSI, Villigen, Switzerland.
    Göttlicher, Peter
    Deutsches Elektronensynchrotron - DESY, Hamburg, Germany.
    Graafsma, Heinz
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion. Deutsches Elektronensynchrotron - DESY, Hamburg, Germany.
    Greiffenberg, Dominic
    Paul Scherrer Institut - PSI, Villigen, Switzerland.
    Hirsemann, Helmut
    Deutsches Elektronensynchrotron - DESY, Hamburg, Germany.
    Jack, Stefanie
    Deutsches Elektronensynchrotron - DESY, Hamburg, Germany.
    Klyuev, Alexander
    Deutsches Elektronensynchrotron - DESY, Hamburg, Germany.
    Krüger, Hans
    Universität Bonn, Bonn, Germany.
    Kuhn, Manuela
    Deutsches Elektronensynchrotron - DESY, Hamburg, Germany.
    Laurus, Torsten
    Deutsches Elektronensynchrotron - DESY, Hamburg, Germany.
    Marras, Alessandro
    Deutsches Elektronensynchrotron - DESY, Hamburg, Germany.
    Mezza, Davide
    Paul Scherrer Institut - PSI, Villigen, Switzerland.
    Mozzanica, Aldo
    Paul Scherrer Institut - PSI, Villigen, Switzerland.
    Poehlsen, Jennifer
    Deutsches Elektronensynchrotron - DESY, Hamburg, Germany.
    Shefer Shalev, Ofir
    Deutsches Elektronensynchrotron - DESY, Hamburg, Germany.
    Sheviakov, Igor
    Deutsches Elektronensynchrotron - DESY, Hamburg, Germany.
    Schmitt, Bernd
    Paul Scherrer Institut - PSI, Villigen, Switzerland.
    Schwandt, Jörn
    Universität Hamburg, Hamburg, Germany.
    Shi, Xintian
    Paul Scherrer Institut - PSI, Villigen, Switzerland.
    Smoljanin, Sergej
    Deutsches Elektronensynchrotron - DESY, Hamburg, Germany.
    Trunk, Ulrich
    Deutsches Elektronensynchrotron - DESY, Hamburg, Germany.
    Zhang, Jiaguo
    Paul Scherrer Institut - PSI, Villigen, Switzerland.
    Zimmer, Manfred
    Deutsches Elektronensynchrotron - DESY, Hamburg, Germany.
    Megapixels @ Megahertz – The AGIPD high-speed cameras for the European XFEL2019Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 942, artikel-id 162324Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    The European XFEL is an extremely brilliant Free Electron Laser Source with a very demanding pulse structure: trains of 2700 X-ray pulses are repeated at 10Hz. The pulses inside the train are spaced by 220ns and each one contains up to 1012photons of 12.4keV, while being ≤100fs in length. AGIPD, the Adaptive Gain Integrating Pixel Detector, is a hybrid pixel detector developed by DESY, PSI, and the Universities of Bonn and Hamburg to cope with these properties. It is a fast, low noise integrating detector, with single photon sensitivity (for Eγ⪆6keV) and a large dynamic range, up to 104 photons at 12.4keV. This is achieved with a charge sensitive amplifier with 3 adaptively selected gains per pixel. 352 images can be recorded at up to 6.5MHz and stored in the in-pixel analogue memory and read out between pulse trains. The core component of this detector is the AGIPD ASIC, which consists of 64 × 64 pixels of 200µm×200µm. Control of the ASIC's image acquisition and analogue readout is via a command based interface. FPGA based electronic boards, controlling ASIC operation, image digitisation and 10GE data transmission interface AGIPD detectors to DAQ and control systems. An AGIPD 1Mpixel detector has been installed at the SPB1 experimental station in August 2017, while a second one is currently commissioned for the MID 2 endstation. A larger (4Mpixel) AGIPD detector and one to employ Hi-Z sensor material to efficiently register photons up to Eγ≈25keV are currently under construction. 

  • 4.
    Andersson, Henrik
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Mattsson, Claes
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Thungström, Göran
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Lundgren, Anders
    SiTek Electro Optics.
    Nilsson, Hans-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    The effect of mechanical stress on lateral-effect position sensitive detector characteristics2006Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 563, nr 1, s. 150-154Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Position-sensitive detectors (PSDs) are widely used in noncontact measurement systems. In order to minimize the size of such systems, interest has increased in mounting the PSD chip directly onto printed circuit boards (PCBs). Stress may be induced in the PSD because of the large differences in thermal expansion coefficients, as well as the long-term geometrical stability of the chip packaging. Mechanical stress has previously been shown to have an effect on the performance of semiconductors. The accuracy, or linearity, of a lateral effect PSD is largely dependent on the homogeneity of the resistive layer. Variations of the resistivity over the active area of the PSD will result in an uneven distribution of photo-generated current, and hence an error in the readout position. In this work experiments were performed to investigate the influence of anisotropic mechanical stress in terms of nonlinearity. PSD chips of 60×3 mm active area were subjected, respectively, to different amounts of compressive and tensile stress to determine the influence on the linearity.

  • 5.
    Andersson, Henrik
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Thungström, Göran
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Lundgren, A.
    Nilsson, Hans-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Processing and characterization of a position sensitive lateral-effect metal oxide semiconductor detector2004Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 531, nr 1-2, s. 140-146Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Position sensingdetectors (PSDs) are useful in many applications, such as vibration, displacement, and triangulation measurements. In this paper we present a lateral-effect metal oxide semiconductor PSD with switchingcapability fabricated by our group. The detector can be switched off by the application of 0V on the substrate and 0.2V on the gate. A linear current-position behaviour is exhibited by the detector at a substrate bias of both 5 and 10V with the gate at 0V. There is no effect on the linearity when the substrate voltage is changed from 5 to 10V. The non-linearity is within 0.2% at a distance of 71.5mm from origin for 5, 10 and 15mm device length.

  • 6.
    Badel, X
    et al.
    KTH.
    Galeckas, A
    Linnros, Jan
    KTH.
    Kleimann, Pascal
    KTH.
    Fröjdh, Christer
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Petersson, Sture
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Improvement of an X-ray imaging detector based on a scintillating guides screen2002Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 487, nr 1-2, s. 129-135Artikel i tidskrift (Refereegranskat)
  • 7. Ballabriga, R.
    et al.
    Campbell, M.
    Heijne, E.
    Llopart, X.
    Tlustos, L.
    Wong, Winnie
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Medipix3: A 64 k pixel detector readout chip working in single photon counting mode with improved spectrometric performance2011Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 633, nr SUPPL. 1, s. S15-S18Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Medipix3 is a 256×256 channel hybrid pixel detector readout chip working in a single photon counting mode with a new inter-pixel architecture, which aims to improve the energy resolution in pixelated detectors by mitigating the effects of charge sharing between channels. Charges are summed in all 2×2 pixel clusters on the chip and a given hit is allocated locally to the pixel summing circuit with the biggest total charge on an event-by-event basis. Each pixel contains also two 12-bit binary counters with programmable depth and overflow control. The chip is configurable such that either the dimensions of each detector pixel match those of one readout pixel or detector pixels are four times greater in area than the readout pixels. In the latter case, event-by-event summing is still possible between the larger pixels. Each pixel has around 1600 transistors and the analog static power consumption is below 15 μW in the charge summing mode and 9 μW in the single pixel mode. The chip has been built in an 8-metal 0.13 μm CMOS technology. This paper describes the chip from the pixel to the periphery and first electrical results are summarized.

  • 8.
    Bertilsson, Kent
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Dubaric, Ervin
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Thungström, Göran
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Nilsson, Hans-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Petersson, Sture
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Simulation of a low atmospheric-noise modified four-quadrant position sensitive detector2001Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 466, nr 1, s. 183-187Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A modified four-quadrant position sensitive detector (PSD) is developed. This structure is less sensitive to atmospheric turbulence that is a major drawback with the traditional four-quadrant detector. The inter-electrode resistance is as high as for the four-quadrant detector, which is an advantage compared to the lateral effect PSD. The linearity for the modified four-quadrant detector is good in the whole active range of sensing. The structures are limited to small sensing areas with well focused beams and are suitable for use in detectors up to 1 mm in size.

  • 9. Campbell, M
    et al.
    Chefdeville, M
    Colas, P
    Colijn, A P
    Fornaini, A
    Giomataris, Y
    van der Graaf, H
    Heijne, E H M
    Kluit, P
    Llopart Cudié, Xavier
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Schmitz, J
    Timmermans, J
    Visschers, J L
    Detection of single electrons by means of a Micromegas-covered Medipix2 pixel CMOS readout circuit2005Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 540, nr 2-3, s. 295-304Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A small drift chamber was read out by means of a MediPix2 readout chip as a direct anode. A Micromegas foil was placed above the chip, and electron multiplication occurred in the gap. With a He/isobutane 80/20 mixture, gas multiplication factors up to tens of thousands were achieved, resulting in an efficiency for detecting single electrons of better than 90%. We recorded many frames containing 2D images with tracks from cosmic muons. Along these tracks, electron clusters were observed, as well as δ-rays.

  • 10. Colas, P
    et al.
    Colijn, A P
    Fornaini, A
    Giomataris, Y
    van der Graaf, H
    Heijne, E H M
    Llopart Cudié, Xavier
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Schmitz, J
    Timmermans, J
    Visschers, J L
    The readout of a GEM or Micromegas-equipped TPC by means of the Medipix2 CMOS sensor as direct anode2004Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 535, nr 1-2, s. 506-510Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We have applied the Medipix2 pixel CMOS chip as direct anode readout for a TPC. For the gas amplification two options have been investigated: (i) a three-stage GEM system and (ii) a Micromegas mesh. The structure of the cloud of primary electrons, left after interactions of 55Fe quanta with the gas is visible with unprecedented precision. This proof-of-principle is an essential step in our project to realize a monolithic pixel sensor with integrated Micromegas, to be developed specially for the readout of TPCs, and applicable for drift chambers in general.

  • 11.
    Davidsson, D. W.
    et al.
    Department of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ, UK.
    Fröjdh, Christer
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    O'Shea, V
    Nilsson, Hans-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Rahman, M
    Limitations to flat-field correction methods when using an X-ray spectrum2003Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, s. 146-150Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Flat-field correction methods are implemented in order to eliminate non-uniformities in X-ray imaging sensors. If the compensation is perfect, then the remaining variations result from noise over the detector area. The efficiency of the compensation is reduced when an object is placed in the beam. A principle cause of this effect is believed to be the spectrum hardening caused by the object. In a normal application the correction factors are calculated for a certain spectrum, meaning that the average of the correction for the individual photon energies are used. If the composition of the spectrum changes the correction factor will also change. In this paper, we present a theory for the sensitivity of the gain constants on X-ray spectra. The theory is supported by experimental data obtained with X-ray spectra and monochromatic X-rays.

  • 12.
    Dian, E.
    et al.
    Hungarian Acad Sci, Budapest, Hungary; European Spallat Source ESS ERIC, Lund; Budapest Univ Technol & Econ, Budapest, Hungary.
    Kanaki, K.
    European Spallat Source ESS ERIC, Lund.
    Ehlers, G.
    Oak Ridge Natl Lab, Oak Ridge, TN USA.
    Hall-Wilton, Richard
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för elektronikkonstruktion. European Spallat Source ESS ERIC, Lund.
    Khaplanov, A.
    European Spallat Source ESS ERIC, Lund.
    Kittelmann, T.
    European Spallat Source ESS ERIC, Lund.
    Zagyvai, P.
    Hungarian Acad Sci, Budapest, Hungary; Budapest Univ Technol & Econ, Budapest, Hungary.
    Scattered neutron background in thermal neutron detectors2018Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 902, s. 173-183Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Inelastic neutron scattering instruments require very low background; therefore the proper shielding for suppressing the scattered neutron background, both from elastic and inelastic scattering is essential. The detailed understanding of the background scattering sources is required for effective suppression. The Multi-Grid thermal neutron detector is an Ar/CO2 gas filled detector with a (B4C)-B-10 neutron converter coated on aluminium substrates. It is a large-area detector design that will equip inelastic neutron spectrometers at the European Spallation Source (ESS). To this end a parameterised Geant4 model is built for the Multi-Grid detector. This is the first time thermal neutron scattering background sources have been modelled in a detailed simulation of detector response. The model is validated via comparison with measured data of prototypes installed on the IN6 instrument at ILL and on the CNCS instrument at SNS. The effect of scattering originating in detector components is smaller than effects originating elsewhere.

  • 13.
    Dubaric, Ervin
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Fröjdh, Christer
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Nilsson, Hans-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Petersson, Sture
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Resolution and Noise Properties of Scintillator Coated X-ray Detectors2001Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 466, nr 1, s. 178-182Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The imaging properties of X-ray pixel detectors depend on the quantum efficiency of X-rays, the generated signal of each X-ray photon and the distribution of the generated signal between pixels. In a scintillator coated device the signal is generated both by X-ray photons captured in the scintillator and by X-ray photons captured directly in the semiconductor. The Signal-to-Noise Ratio in the image is then a function of the number of photons captured in each of these processes and the yield, in terms of electron-hole pairs produced in the semiconductor, of each process. The spatial resolution is primarily determined by the light spreading within the scintillator. In a pure semiconductor detector the signal is generated by one process only. The Signal-to-Noise Ratio in the image is proportional to the number of X-ray photons captured within the sensitive layer. The spatial resolution is affected by the initial charge cloud generated in the semiconductor and any diffusion of carriers between the point of interaction and the readout electrode. In this paper we discuss the theory underlying the imaging properties of scintillator coated X-ray imaging detectors. The model is verified by simulations using MCNP and by experimental results. The results from the two-layer detector are compared with those from a pure semiconductor X-ray detector.

  • 14.
    Dubaric, Ervin
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Nilsson, Hans-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Fröjdh, Christer
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Norlin, Börje
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Monte Carlo simulation of the response of a pixellated 3D photodetector in silicon2002Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 487, nr 1-2, s. 136-141Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The charge transport and X-ray photon absorption in three-dimensional (3D) X-ray pixel detectors have been studied using numerical simulations. The charge transport has been modelled using the drift-diffusion simulator MEDICI, while photon absorption has been studied using MCNP. The response of the entire pixel detector system in terms of charge sharing, line spread function and modulation transfer function, has been simulated using a system level Monte Carlo simulation approach. A major part of the study is devoted to the effect of charge sharing on the energy resolution in 3D-pixel detectors. The 3D configuration was found to suppress charge sharing much better than conventional planar detectors.

  • 15.
    Fröjdh, Anna
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Fröjdh, Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Thungström, Göran
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Fröjdh, Christer
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Norlin, Börje
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Processing and characterization of a MEDIPIX2-compatible silicon sensor with 220 mu m pixel size2011Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 633, nr Suppl 1, s. S78-S80Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Pixellated silicon detectors with a pixel size of 220 um have been fabricated at Mid Sweden University. The detectors will be bonded to the MEDIPIX2 [1] readout chip. The purpose is to investigate the performance of an energy sensitive X-ray imaging sensor with reduced charge sharing.

    The detectors were fabricated on high purity silicon with a wafer thickness of 500 um and a resistivity of more than 15 kohmcm. One reason for the choice of material was to get experience for future work with very thick detectors requiring ultra high resistivity in order to be depleted. During the initial work in this project some issued were found concerning inter pixel resistance and the efficiency of the guard rings. This led to a study of existing papers on the subject [2,3,4,5] and to extensive simulations of the electric field and the charge transport in different parts of the device.

    A modified process has been developed using alternating p+ and n+ guard rings and an outer n+ doping. The results of the simulations and the process will be described as well as an outline for a process for fabrication of very thick detectors with limited guard ring extension.

    References[1] - X. Llopart, M. Campbell, R. Dinapoli, D. San Segundo and E. Pernigotti, IEEE Trans. Nucl. Sci., vol. 49, 2279-2283, October 2002.[2] – L. Evensen, A. Hanneborg, B Sundby Avset, M. Mese, Nuclear Instruments and Methods in Physics Research A 337 (1993) 44 – 52[3] – T. Pavalainen, T. Tuuva, K. Leinonen, Nuclear Instruments and Methods in Physics Research A 573 (2007) 277 – 279[4] – Z. Li, W. Huang, L. J. Zhao, IEEE Trans. Nucl. Sci., vol. 47, No. 3. 729 – 735 , June 2000.[5] – D. Han, C. Wang, G. Wang, S. Du, L. Shen, X. Tian, X. Zhang, IEEE Transactions on Electron devices, Vol. 50, No. 2, 537 – 540, February 2003

  • 16.
    Fröjdh, Christer
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Andersson, J
    Bates , R
    Heuken, M
    Irsigler, R
    Petersson, Sture
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    O'Shea, V
    Smith, K M
    Stamatakis, H
    Welander, U
    New sensors for dental X-ray imaging1999Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 434, nr 1, s. 24-29Artikel i tidskrift (Refereegranskat)
  • 17.
    Fröjdh, Christer
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Graafsma, Heinz
    Experimental Division, ESRF, BP2200 Avenue des Martyrs, 38043 Grenoble, Cedex, France.
    Norlin, Börje
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Nilsson, Hans-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Ponchut, Cyril
    Experimental Division, ESRF, BP2200 Avenue des Martyrs, 38043 Grenoble, Cedex, France.
    Characterization of a pixellated CdTe detector with single-photon processing readout2006Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 563, nr 563, s. 128-132Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A 1mm thick pixellated CdTe detector bonded to the MEDIPIX2 [1] readout chip has been characterized using a monoenergetic microbeam at the ESRF. This is an extension of the tests previously reported in [2]. The results show that a full energy peak can be obtained when a narrow beam is focused in the centre of the pixel. There is also evidence of significant charge diffusion and fluorescence. The results indicate that the charge sharing is the most important problem and will cause loss of the energy information in an imaging application. The second problem is the fluorescence which limits the number of counts in the full energy peak even for hits in the centre of the pixel.

  • 18.
    Fröjdh, Erik
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för elektronikkonstruktion. CERN, Geneva, Switzerland.
    Bisello, F.
    IBA Dosimetty GmbH, Schwarzenhatck, Germany.;FAU Univ Erlangen Nrnberg, Erlangen, Germany..
    Campbell, M.
    CERN, Geneva, Switzerland..
    Damet, J.
    CERN, Geneva, Switzerland.;Univ Lausanne Hosp, Inst Radiat Phys, Lausanne, Switzerland..
    Hamann, E.
    KIT, ANKA Synchrotron Radiat Facil, Karlsruhe, Germany..
    Koenig, T.
    KIT, ANKA Synchrotron Radiat Facil, Karlsruhe, Germany..
    Wong, Winnie S.
    CERN, Geneva, Switzerland.;Univ Lausanne Hosp, Inst Radiat Phys, Lausanne, Switzerland..
    Zuber, M.
    KIT, ANKA Synchrotron Radiat Facil, Karlsruhe, Germany..
    Spectral response of the energy-binning Dosepix ASIC coupled to a 300 mu m silicon sensor under high fluxes of synchrotron radiation2015Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 804, s. 43-49Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Dosepix hybrid pixel detector was designed for dosimetry and radiation monitoring applications. It has three programmable modes of operation: photon counting mode, energy integration mode, and dosimetry mode. The dosimetry mode measures the energy of individual X-ray photons and automatically sorts events into pre-defined energy bins. The output is a histogram representing the measured X-ray energy spectrum, permitting a dose reconstruction that accounts for the attenuation of photons at each energy bin. This presents a potential radiation protection and dosimetry instrument in medical radiodiagnostic practices, including high flux systems such as computed tomography (CT). In this paper, we characterise the Dosepix chip by investigating the energy response and count rate capabilities when coupled to a 300 pm silicon sensor under high fluxes of monochromatic synchrotron radiation. Under nominal settings, the Dosepix detector can detect photons down to 3.5 keV, with an energy resolution of 16.5% FWHM for 8.5 keV photons and 8% FWHM for 40 keV photons. The chip can count up to 1.67 Mcps/mm(2) of 40 keV photons whilst maintaining linear counting behaviour. This count rate range can be further increased by changing the programmable operating settings of the detector, making it suitable for a range of photon dosimetry applications.

  • 19.
    Fröjdh, Erik
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Fröjdh, Anna
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Norlin, Börje
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Fröjdh, Christer
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Spectral response of a silicon detector with 220 mu m pixel size bonded to MEDIPIX22011Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 633, nr Supplement 1, s. S125-S127Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The standard detector used with the MEDIPIX2 [1] readout chip suffers from severe charge sharing that reduces the spectral performance of the device. This problem is expected to be solved in the MEDIPIX3 [2] design. In order to significantly reduce the charge sharing and to make a detector which could be expected to have a similar response to MEDIPIX3 we have fabricated detectors with a pixel size of 220 um and bonded these detectors to the MEDIPIX2 chip using only a limited number of pixels on the readout chip. This makes the active area of the pixel comparable with the area covered by the charge summing in MEDIPIX3.

    The charge collection properties of the device have been tested by scanning a narrow beam over a pixel. The spectral response has been measured by taking a flood exposure at different tube voltages and comparing the result with the spectrum obtained from exposing the centre of the pixel with a narrow beam thus eliminating the charge sharing. This work represents an improved characterisation as compared to [3].

    Some initial images of different objects have been taken by placing the device in an X-ray microscope with a nanofocus X-ray tube imaging objects with magnification to simulate the original pixel size of 55 um.

    References[1] - X. Llopart, M. Campbell, R. Dinapoli, D. San Segundo and E. Pernigotti, IEEE Trans. Nucl. Sci., vol. 49, 2279-2283, October 2002.[2] - R. Ballabriga, M. Campbell, E. H. M. Heijne, X. Llopart, L. Tlustos, IEEE Trans. Nucl. Sci., Vol. 54, No. 5, October 2007.[3] – B. Norlin, C. Fröjdh, G. Thungström, D. Greiffenberg, NSS Conference record,19-25 Oct. 2008, Pages:3464 – 3469, Digital Object Identifier 10.1109/NSSMIC.2008.4775083

  • 20.
    Hjelm, Mats
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Norlin, Börje
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Nilsson, Hans-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Fröjdh, Christer
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Badel, X
    Monte Carlo simulation of the imaging properties of scintillator-coated X-ray pixel detetectors2003Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 509, nr 1-3, s. 76-85Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The spatial resolution of scintillator-coated X-ray pixel detectors is usually limited by the isotropic light spread in the scintillator. One way to overcome this limitation is to use a pixellated scintillating layer on top of the semiconductor pixel detector. Using advanced etching and filling techniques, arrays of CsI columns have been successfully fabricated and characterized. Each CsI waveguide matches one pixel of the semiconductor detector, limiting the spatial spread of light. Another concept considered in this study is to detect the light emitted from the scintillator by diodes formed in the silicon pore walls. There is so far no knowledge regarding the theoretical limits for these two approaches, which makes the evaluation of the fabrication process difficult. In this work we present numerical calculations of the signal-to-noise ratio (SNR) for detector designs based on scintillator-filled pores in silicon. The calculations are based on separate Monte Carlo (MC) simulations of X-ray absorption and light transport in scintillator waveguides. The resulting data are used in global MC simulations of flood exposures of the detector array, from which the SNR values are obtained. Results are presented for two scintillator materials, namely CsI(Tl) and GADOX.

  • 21. Irsigler, R
    et al.
    Andersson, J
    Alverbro, J
    Borglind, J
    Fröjdh, Christer
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Helander, P
    Manolopoulos, S
    O'Shea, V
    Smith, K M
    Evaluation of 320 x 240 pixel LEC GaAs Schottky barrier X-ray imaging arrays, hybridized to CMOS readout circuit based on charge integration1999Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 434, nr 1, s. 24-29Artikel i tidskrift (Refereegranskat)
  • 22. Irsigler, R
    et al.
    Andersson, J
    Alverbro, J
    Fakoor-Biniaz, Z
    Fröjdh, Christer
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Helander, P
    Martijn, H
    Meikele, D
    Östlund, M
    O'Shea, V
    Smith, K M
    320x240 GaAs pixel detectors with improved X-ray imaging quality2001Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 460, nr 1, s. 67-71Artikel i tidskrift (Refereegranskat)
  • 23.
    Jebali, R.
    et al.
    Arktis Radiat Detectors Ltd, CH-8045 Zurich, Switzerland.
    Scherzinger, J.
    Lund Univ, Div Nucl Phys, SE-22100 Lund, Sweden.
    Annand, J. R. M.
    Univ Glasgow, Glasgow G12 8QQ, Lanark, Scotland.
    Chandra, R.
    Arktis Radiat Detectors Ltd, CH-8045 Zurich, Switzerland.
    Davatz, G.
    Arktis Radiat Detectors Ltd, CH-8045 Zurich, Switzerland.
    Fissum, K. G.
    Lund Univ, Div Nucl Phys, SE-22100 Lund, Sweden.
    Friederich, H.
    Arktis Radiat Detectors Ltd, CH-8045 Zurich, Switzerland.
    Gendotti, U.
    Arktis Radiat Detectors Ltd, CH-8045 Zurich, Switzerland.
    Hall-Wilton, Richard
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för elektronikkonstruktion. European Spallat Source ESS AB, Detector Grp, SE-22100 Lund, Sweden.
    Hakansson, E.
    Lund Univ, Div Nucl Phys, SE-22100 Lund, Sweden.
    Kanaki, K.
    European Spallat Source ESS AB, Detector Grp, SE-22100 Lund, Sweden.
    Lundin, M.
    Lund Univ, MAX Lab 4, SE-22100 Lund, Sweden.
    Murer, D.
    Arktis Radiat Detectors Ltd, CH-8045 Zurich, Switzerland.
    Nilsson, B.
    European Spallat Source ESS AB, Detector Grp, SE-22100 Lund, Sweden.
    Rosborg, A.
    Lund Univ, MAX Lab 4, SE-22100 Lund, Sweden.
    Svensson, H.
    Lund Univ, MAX Lab 4, SE-22100 Lund, Sweden.
    A first comparison of the responses of a He-4-based fast-neutron detector and a NE-213 liquid-scintillator reference detector2015Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 794, s. 102-108Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A first comparison has been made between the pulse-shape discrimination characteristics of a novel He-4-based pressurized scintillation detector and a NE-213 liquicl-scintillator reference detector using an Am/Be mixed-field neutron and gamma-ray source and a high-resolution scintillation-pulse digitizer. In particular, the capabilities of the two fast neutron detectors to discriminate between neutrons and gamma-rays were investigated. The NE-213 liquicl-scintillator reference cell produced a wide range of scintillation-light yields in response to he gamma-ray field of the source. In stark contrast, clue to the size and pressure of the He-4 gas volume, the He-4-based detector registered a maximum scintillation-light yield of 750 keV(ee) to the same gamma-ray field. Pulse-shape discrimination for particles with scintillation-light yields of more than 750 keV(ee) was excellent in the case of the He-4-based detector. Above 750 keV(ee) its signal was unambiguously neutron, enabling particle identification based entirely upon the amount of scintillation light produced. (C) 2015 The Authors. Published by Elsevier B.V.

  • 24.
    Kleimann, Pascal
    et al.
    KTH.
    Linnros, Jan
    KTH.
    Fröjdh, Christer
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Petersson, Sture
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    An X-ray imaging pixel detector based on scintillator filled pores in a silicon matrix2001Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 460, nr 1, s. 15-19Artikel i tidskrift (Refereegranskat)
  • 25.
    Kostamo, Pasi
    et al.
    Helsinki University of Technology.
    Nenonen, Seppo
    Oxford Instruments Analythical Oy.
    Vähänen, Sami
    VTT.
    Tlustos, Lukas
    CERN.
    Fröjdh, Christer
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Campbell, Michael
    CERN.
    Zhilyaev, Yuri
    Yoffe Institute.
    Lipsanen, Harri
    Helsinki University of Technology.
    GaAs Medipix2 hybrid pixel detector2008Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 591, nr 1, s. 174-177Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A GaAs Medipix2 hybrid pixel detector based on high purity epitaxial GaAs material was successfully fabricated. The mesa type GaAs sensor with 256×256 pixels and total area of 1.4×1.4 cm2 was made of a 140-μm-thick epitaxial p–i–n structure utilizing reactive ion etching. A final thickness of approximately 110 μm for the all-epitaxial sensor element is achieved by back-thinning procedure. The sensor element is bump bonded to a Medipix2 read-out ASIC. The detector is capable of room temperature spectroscopic operation and it demonstrates the potential of GaAs for high resolution X-ray imaging systems operating at room temperature. This work describes the manufacturing process and electrical properties of the GaAs Medipix2 hybrid detector.

  • 26.
    Lars, Herrnsdorf
    et al.
    RTI electronics.
    Björk, M
    RTI electronics.
    Cederquist, Björn
    RTI electronics.
    Mattsson, Claes
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Thungström, Göran
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Fröjdh, Christer
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Point Dose Profile Measurments using Solid State Detectors in Characterization of Computed Tomograhy Systems2009Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 607, nr 1, s. 223-225Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Existing solid-state detectors for point dose measurements are typically mounted in a package with a high Z material acting as the back contact causing unsymmetrical response. In the Computed Tomography (CT) dose profile application this is a major drawback. A new silicon detector has been constructed without this disturbing element. The new detector has been mounted in a cylindrical tube and its characteristics are presented in this paper. The conclusion is that this new detector design is a major improvement for correct dose and dose profile measurements in CT systems.

     

     

  • 27.
    Llopart Cudié, Xavier
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    First test measurements of a 64k pixel redout chip working in single photon counting mode2003Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 509, nr 1-3, s. 157-163Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Medipix2 chip is a pixel detector readout chip consisting of 256×256 identical elements, each working in single photon counting mode for positive or negative input charge signals. The chip is designed and manufactured in a six-metal 0.25 μm CMOS technology. This paper describes several electrical measurements which have been carried out on the chip prior to detector bump bonding using a dedicated readout system. Threshold linearity and variation has been measured for both electron and hole collection. The noise is 100e RMS and the threshold can be adjusted to 120e RMS for both polarities. The minimum operating threshold is 1000e.

  • 28.
    Llopart Cudié, Xavier
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Ballabriga, R
    Campbell, M
    Tlustos, L
    Wong, Winnie
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Timepix, a 65k programmable pixel readout chip for arrival time, energy and/or photon counting measurements2007Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 581, nr 1-2, s. 485-494Artikel i tidskrift (Refereegranskat)
  • 29.
    Lundgren, Jan
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Abdalla, Suliman
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    O'Nils, Mattias
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Oelmann, Bengt
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Evaluation of Mixed-Signal Noise Effects in Photon Counting X-Ray Image Sensor Readout Circuits2006Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 563, nr 1, s. 88-91Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In readout electronics for photon counting pixel detectors, the tight integration between analog and digital blocks causes the readout electronics to be sensitive to on-chip noise coupling. This noise coupling can result in faulty luminance values in grayscale X-ray images, or as color distortions in a color X-ray imaging system. An exploration of simulating noise coupling in readout circuits is presented which enables the discovery of sensitive blocks at as early a stage as possible, in order to avoid costly design iterations. The photon counting readout system has been simulated for noise coupling in order to highlight the existing problems of noise coupling in X-ray imaging systems. The simulation results suggest that on-chip noise coupling should be considered and simulated in future readout electronics systems for X-ray detectors.

  • 30.
    Lundgren, Jan
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Abdalla, Suliman
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    O'Nils, Mattias
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Oelmann, Bengt
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Power Distribution and Substrate Noise Coupling Investigations on the Behavioral Level for Photon Counting Imaging Readout Circuits2007Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 576, nr 1, s. 113-117Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In modern mixed-signal system design, there are increasing problems associated with noise coupling caused by switching digital parts to sensitive analog parts. As a consequence, there is a growing necessity to understand these problems. In order to avoid costly design iterations, noise coupling simulations should be initiated as early as possible in the design chain. The problems associated with on-chip noise coupling have been discovered in photon counting pixel detector readout systems, where the level of integration of analog and digital circuits is very high on a very small area, and it would appear that these problems will continue to increase for future system designs in this field. This paper deals with the functionality of utilizing behavioral level models for simulating noise coupling in these readout systems. The methods and models are described and simulation results are shown for a photon counting pixel detector readout system.

  • 31.
    Lundgren, Jan
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    O'Nils, Mattias
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Oelmann, Bengt
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Norlin, Börje
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Abdalla, Suliman
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    An Area Efficient Readout Architecture for Photon Counting Color Imaging2007Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 576, nr 1, s. 132-136Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The introduction of several energy levels, namely color imaging, in photon counting X-ray image sensors is a trade-off between circuit complexity and spatial resolution. In this paper we propose a pixel architecture that has full resolution for the intensity and uses sub-sampling for the energy spectrum. The results show that this sub-sampling pixel architecture produces images with an image quality which is, on average, 2.4 dB (PSNR) higher than those for a single energy range architecture and with half the circuit complexity of that for a full sampling architecture.

  • 32.
    Manuilskiy, Anatoily
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Norlin, Börje
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Nilsson, Hans-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Fröjdh, Christer
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Spectroscopy applications for the Medipix photon counting X-ray system2004Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 531, nr 1-2, s. 251-257Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Since the Medipix system is a photon counting system, it is possible to use it as a spectroscopic device, which is sensitive to the energy of the incoming photons. The system can, for example, be used to achieve the spectrum of an unknown source. Since it is an imaging system, it can be useful for energy dependent scattering experiments. The factors limiting the spectroscopic resolution are source and channel noise and detector non-uniformity. A well-known method for correction non-uniformity is to use mono energetic source and a threshold adjustment. However, since the threshold calibration is energy dependent, its use for sources with wider energy range is limited. We have shown an easy method to create threshold calibration masks for different thresholds that include both detector and channel stationary influences with analysis of histograms of series of images. The model for histograms was created assuming a standard dental X-ray source, which allows finding mask-creating parameters like threshold range (Vth and Vthadj). This procedure can be performed for each energy of interest. Based on these arrays, mask files that narrowed the threshold distribution close to the theoretical limit, were prepared. The limit of the spectroscopic resolution for the system was measured by analysing histograms for series of flat images under identical conditions.

  • 33.
    Marchal, J
    et al.
    University of Glasgow.
    Passmore, M S
    Abdalla, Munir
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    van den Berg, J
    Nejim, A
    Fröjdh, Christer
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    O'Shea, V
    Smith, K M
    Rahman, M
    Active pixel detector for ion beam profiling2002Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 487, nr 1-2, s. 224-231Artikel i tidskrift (Refereegranskat)
  • 34.
    Marras, A.
    et al.
    Deutsches Elektronen-Synchrotron, Hamburg, Germany .
    Trunk, U.
    Deutsches Elektronen-Synchrotron, Hamburg, Germany .
    Klyuev, A.
    Deutsches Elektronen-Synchrotron, Hamburg, Germany .
    Becker, J.
    Deutsches Elektronen-Synchrotron, Hamburg, Germany .
    Graafsma, Heinz
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för elektronikkonstruktion. Deutsches Elektronen-Synchrotron, Hamburg, Germany .
    Shi, X.
    Paul Schrerrer Institute, Villigen, Switzerland .
    Greiffenberg, D.
    Paul Schrerrer Institute, Villigen, Switzerland .
    Schmitt, B.
    Paul Schrerrer Institute, Villigen, Switzerland .
    Front end electronics for European XFEL sensor: The AGIPD project2013Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 731, s. 79-82Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The AGIPD (Adaptive Gain Integrating Pixel Detector) is a detector under development, to be used in the European X-ray Free-Electron Laser (XFEL). The constraints imposed by the XFEL source are discussed, and the solutions implemented to cope with them are explained. The present status of the project is reported, along with results achieved in terms of noise, memory depth, and radiation tolerance. © 2013 Elsevier B.V.

  • 35.
    Mattsson, Claes
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Bertilsson, Kent
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Thungström, Göran
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Nilsson, Hans-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Manufacturing and characterization of a modified four-quadrant position sensitive detector for out-door applications2004Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 531, nr 1-2, s. 134-139Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Position sensing detectors (PSDs) are useful in many applications such as vibration, displacement and triangulation measurements. In this paper we have constructed a novel structure, which has higher inter-electrode resistance than a lateral effect PSD and is more robust to atmospheric turbulence than a conventional four-quadrant PSD (Nuclear Instruments and Methods in Physics Research A 466 (2001) 183). The detector structure is useful for applications with detector windows less than 0.5 x 0.5 mm(2), but the nonlinearity is the main concern for a detector of that size. Without any corrections for non-linearity the standard deviation of the error is 9 mum (2.2%). Using a simple analytical expression and a 2-d correction-function stored in a look-up table the positioning error is reduced to 6 (1.5%) and 2 (0.5%) mum, respectively.

  • 36.
    Mezza, D.
    et al.
    Paul-Scherrer-Institute (PSI), Villigen, Switzerland.
    Allahgholi, A.
    Deutsches Elektronensynchrotron DESY, Hamburg, Germany.
    Arino-Estrada, G.
    Deutsches Elektronensynchrotron DESY, Hamburg, Germany.
    Bianco, L.
    Deutsches Elektronensynchrotron DESY, Hamburg, Germany.
    Delfs, A.
    Deutsches Elektronensynchrotron DESY, Hamburg, Germany.
    Dinapoli, R.
    Paul-Scherrer-Institute (PSI), Villigen, Switzerland.
    Goettlicher, P.
    Deutsches Elektronensynchrotron DESY, Hamburg, Germany.
    Graafsma, Heinz
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för elektronikkonstruktion. Deutsches Elektronensynchrotron DESY, Hamburg, Germany.
    Greiffenberg, D.
    Paul-Scherrer-Institute (PSI), Villigen, Switzerland.
    Hirsemann, H.
    Deutsches Elektronensynchrotron DESY, Hamburg, Germany.
    Jack, S.
    Deutsches Elektronensynchrotron DESY, Hamburg, Germany.
    Klanner, R.
    University of Hamburg, Hamburg, Germany.
    Klyuev, A.
    Deutsches Elektronensynchrotron DESY, Hamburg, Germany.
    Krueger, H.
    University of Bonn, Bonn, Germany.
    Marras, A.
    Deutsches Elektronensynchrotron DESY, Hamburg, Germany.
    Mozzanica, A.
    Paul-Scherrer-Institute (PSI), Villigen, Switzerland.
    Poehlsen, J.
    Deutsches Elektronensynchrotron DESY, Hamburg, Germany.
    Schmitt, B.
    Paul-Scherrer-Institute (PSI), Villigen, Switzerland.
    Schwandt, J.
    University of Hamburg, Hamburg, Germany.
    Sheviakov, I.
    Deutsches Elektronensynchrotron DESY, Hamburg, Germany.
    Shi, X.
    Paul-Scherrer-Institute (PSI), Villigen, Switzerland.
    Trunk, U.
    Deutsches Elektronensynchrotron DESY, Hamburg, Germany.
    Xia, Q.
    Deutsches Elektronensynchrotron DESY, Hamburg, Germany.
    Zhang, J.
    Paul-Scherrer-Institute (PSI), Villigen, Switzerland.
    Zimmer, M.
    Deutsches Elektronensynchrotron DESY, Hamburg, Germany.
    Characterization of AGIPD1.0: The full scale chip2016Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 838, s. 39-46Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The AGIPD (adaptive gain integrating pixel detector) detector is a high frame rate (4.5 MHz) and high dynamic range (up to 104 ·12.4 keV photons) detector with single photon resolution (down to 4 keV taking 5σ as limit and lowest noise settings) developed for the European XFEL (XFEL.EU). This work is focused on the characterization of AGIPD1.0, which is the first full scale version of the chip. The chip is 64×64 pixels and each pixel has a size of 200×200 μm2. Each pixel can store up to 352 images at a rate of 4.5 MHz (corresponding to 220 ns). A detailed characterization of the AGIPD1.0 chip has been performed in order to assess the main performance of the ASIC in terms of gain, noise, speed and dynamic range. From the measurements presented in this paper a good uniformity of the gain, a noise around 320 e− (rms) in standard mode and around 240 e− (rms) in high gain mode has been measured. Furthermore a detailed discussion about the non-linear behavior after the gain switching is presented with both experimental results and simulations.

  • 37.
    Mezza, D.
    et al.
    Paul-Scherrer-Institute (PSI), Villigen, Switzerland.
    Allahgholi, A.
    Deutsches Elektronensynchrotron DESY, Hamburg, Germany.
    Becker, J.
    Deutsches Elektronensynchrotron DESY, Hamburg, Germany.
    Delfs, A.
    Deutsches Elektronensynchrotron DESY, Hamburg, Germany.
    Dinapoli, R.
    Paul-Scherrer-Institute (PSI), Villigen, Switzerland.
    Goettlicher, P.
    Deutsches Elektronensynchrotron DESY, Hamburg, Germany.
    Graafsma, Heinz
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion. Deutsches Elektronensynchrotron DESY, Hamburg, Germany.
    Greiffenberg, D.
    Paul-Scherrer-Institute (PSI), Villigen, Switzerland.
    Hirsemann, H.
    Deutsches Elektronensynchrotron DESY, Hamburg, Germany.
    Klyuev, A.
    Deutsches Elektronensynchrotron DESY, Hamburg, Germany.
    Kuhn, M.
    Deutsches Elektronensynchrotron DESY, Hamburg, Germany.
    Lange, S.
    Deutsches Elektronensynchrotron DESY, Hamburg, Germany.
    Laurus, T.
    Deutsches Elektronensynchrotron DESY, Hamburg, Germany.
    Marras, A.
    Deutsches Elektronensynchrotron DESY, Hamburg, Germany.
    Mozzanica, A.
    Paul-Scherrer-Institute (PSI), Villigen, Switzerland.
    Poehlsen, J.
    Deutsches Elektronensynchrotron DESY, Hamburg, Germany.
    Ruder, C.
    Paul-Scherrer-Institute (PSI), Villigen, Switzerland.
    Schmitt, B.
    Paul-Scherrer-Institute (PSI), Villigen, Switzerland.
    Schwandt, J.
    University of Hamburg, Hamburg, Germany.
    Sheviakov, I.
    Deutsches Elektronensynchrotron DESY, Hamburg, Germany.
    Shi, X.
    Paul-Scherrer-Institute (PSI), Villigen, Switzerland.
    Trunk, U.
    Deutsches Elektronensynchrotron DESY, Hamburg, Germany.
    Zhang, J.
    Paul-Scherrer-Institute (PSI), Villigen, Switzerland.
    Zimmer, M.
    Deutsches Elektronensynchrotron DESY, Hamburg, Germany.
    Characterization of the AGIPD1.1 readout chip and improvements with respect to AGIPD1.02019Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 945, artikel-id 162606Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    AGIPD, the Adaptive Gain Integrating Pixel Detector, is a hybrid detector with a frame rate of 4.5 MHz, a dynamic range up to 104⋅ 12.4 keV photons, as well as single photon resolution, developed for the European XFEL (Eu.XFEL). The final 1 Mpixel detector system consists of 16 tiled modules each one with 16 readout chips. The single ASIC is 64 x 64 pixels, each with a size of 200 x 200 μm2. Each pixel can store up to 352 images. This work is focused on the characterization of AGIPD1.1, the second version of the full scale ASIC, and the improvements with respect to AGIPD1.0. From the measurements presented in this paper we show that the flaws observed in AGIPD1.0 (i.e. ghosting, crosstalk, slow readout speed) have been fixed in AGIPD1.1. In addition the main performance parameters such as noise, dynamic range and so on were measured for the new version of the ASIC and will be summarized. 

  • 38. Mikuec, B
    et al.
    Campbell, M
    Heijne, E
    Llopart Cudié, Xavier
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    X-ray imaging using single photon processing with semiconductor pixel detectors2003Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 511, nr 1-2, s. 282-286Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    More than 10 years experience with semiconductor pixel detectors for vertex detection in high-energy physics experiments together with the steady progress in CMOS technology opened the way for the development of single photon processing pixel detectors for various applications including medical X-ray imaging. The state of the art of such pixel devices consists of pixel dimensions as small as 55×55 μm2, electronic noise per pixel <100 e− rms, signal-to-noise discrimination levels around 1000 e− with a spread <50 e− and a dynamic range up to 32 bits/pixel. Moreover, the high granularity of hybrid pixel detectors makes it possible to probe inhomogeneities of the attached semiconductor sensor.

     

     

  • 39.
    Nilsson, Hans-Erik
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Dubaric, Ervin
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Hjelm, Mats
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Bertilsson, Kent
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Simulation of photon and charge transport in X-ray imaging semiconductor sensors2002Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 487, nr 1-2, s. 151-162Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A fully stochastic model for the imaging properties of X-ray silicon pixel detectors is presented. Both integrating and photon counting configurations have been considered, as well as scintillator-coated structures. The model is based on three levels of Monte Carlo simulations; photon transport and absorption using MCNP, full band Monte Carlo simulation of charge transport and system level Monte Carlo simulation of the imaging performance of the detector system. In the case of scintillator-coated detectors, the light scattering in the detector layers has been simulated using a Monte Carlo method. The image resolution was found to be much lower in scintillator-coated systems due to large light spread in thick scintillator layers. A comparison between integrating and photon counting readout methods shows that the image resolution can be slightly enhanced using a photon-counting readout. In addition, the proposed model has been used to study charge-sharing effects on the energy resolution in photon counting detectors. The simulation shows that charge-sharing effects are pronounced in pixel detectors with a pixel size below 170 * 170 mu m2. A pixel size of 50 * 50 mu m2 gives a highly distorted energy spectrum due to charge sharing. This negative effect can only be resolved by introducing advanced counting schemes, where neighbouring pixels communicate in order to resolve the charge sharing.

  • 40.
    Nilsson, Hans-Erik
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Mattsson, Claes
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Norlin, Börje
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Fröjdh, Christer
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Bethke, K
    PANalytical B.V, Netherlands.
    De Vries, R
    PANalytical B.V, Netherlands.
    Evaluation of the charge sharing effects on spot intensity in XRD setup using photon counting pixel detectors2005Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 563, nr 1, s. 182-186Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this study we examine how charge loss due to charge sharing in photon counting pixel detectors affects the recording of spot intensity in an X-ray Diffraction (XRD) setup. In the photon counting configuration the charge from photons that are absorbed at the boarder of a pixel will be shared between two pixels. If the threshold is high enough these photons will not be counted. However, if the threshold is low enough these photons will be counted twice. In an XRD setup the intensity and position of various spots should be recorded. Thus, the intensity measure will be affected by the setting of the threshold. In this study we used a system level Monte Carlo simulator to evaluate the variations in the intensity signals for different threshold settings and spot sizes. The simulated setup included an 8keV monochromatic source (providing a Gaussian shaped spot) and the MEDIPIX2 photon counting pixel detector (55 µm x 55 µm pixel size with 300µm silicon) at various detector biases. Our study shows that the charge sharing distortion can be compensated by numerical post processing and high resolution in both charge (charge distribution?) and position can be achieved.

  • 41.
    Nilsson, Hans-Erik
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Norlin, Börje
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Fröjdh, Christer
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Tlustos, Lukas
    CERN, Switzerland.
    Charge sharing suppression using pixel-to-pixel communication in photon counting X-ray imaging systems2007Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 576, nr 1, s. 243-247Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In planar silicon detector structures the charge sharing between pixels is one limiting factor for colour X-ray imaging using integrated photon counting pixel detectors. 3D detector structures have been proposed as one solution to this problem. However, there are also readout system solutions to the problem i.e. introducing pixel to pixel communication and distributed charge summing in the readout electronics. In this work different charge summing schemes are evaluated using Monte Carlo simulation techniques. The increase in electronic noise introduced by the charge summing is one of the most severe problems. A proper selection of summing scheme is necessary to obtain an efficient system.

  • 42.
    Norlin, Börje
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Fröjdh, Christer
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Characterisation of spectral performance of pixellated X-ray imaging detectors in a microscopy setup2009Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 607, nr 1, s. 199-201Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In order to achieve energy resolved X-ray imaging with small pixel resolution, physical processes in the detector material such as fluorescence and charge sharing must be considered. This paper presents characterisation measurements performed with an X-ray microscopy setup for energy resolved imaging. The microscopy setup consists of a nanofocus X-ray source capable of 160 kV anode voltage, ESRF-type collimating slits and Medipix2 detectors. The detector systems developed in the Medipix collaboration are capable of energy resolved imaging. The measurements were performed by scanning an energy window through the spectrum. In this paper we have considered detectors made of Si, GaAs and CdTe for use in the microscopy setup. Both measurements and theoretical simulations are considered. For high X-ray energies, it is essential to consider fluorescence from the shielding and Compton scattering in silicon detectors.

  • 43.
    Norlin, Börje
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Fröjdh, Christer
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Energy dependence in dental imaging with Medipix22005Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 546, nr 1-2, s. 19-23Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The possibility to achieve better contrast in dental images by selecting specific X-ray energies is investigated. By applying both the low and the high photon counting energy threshold of the Medipix2 chip only a narrow interval of the spectrum of a 60 keV standard dental source used is selected. The relative contrast between the parts of the tooth with the highest respectively lowest absorption increases 18 % when the energy spread of the X-rays is narrowed from the full spectrum to a 4 keV window centered around 36 keV. The small tail of high energy photons from the full source spectrum lowers the achieved relative contrast significantly. This result can be used in development of X-ray sources or in consideration of energy weighting.

  • 44.
    Norlin, Börje
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Fröjdh, Christer
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Nilsson, Hans-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Spectral performance of a pixellated X-ray imaging detector with suppressed charge sharing2007Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. A 576, nr 1, s. 248-250Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The ability to do X-ray imaging with energy resolution on a small pixel detector is severely limited by the charge sharing in the detector. Different schemes to overcome the problem have been proposed. Previous studies using synchrotron radiation have shown that, for a 300 µm thick Si detector, almost no charge sharing occurs for photons hitting the centre of each pixel. In this study we have used slits to focus the beam from a standard X-ray unit on the centre of a pixel on a MEDIPIX detector. The attenuation of the spectrum were measured for a number of samples of different materials with K-edge energy in the range of 30 to 50 keV. The measurements were done by scanning an energy window through the spectrum. Requirements for new X-ray imaging systems with true energy resolution are discussed based on these measurements.

  • 45.
    Norlin, Börje
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Fröjdh, Christer
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Nilsson, Hans-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Graafsma, Heinz
    Experimental Division, ESRF, Avenue des Martyrs, 38043 Grenoble Cedex, France.
    Vonk, Vederan
    Experimental Division, ESRF, Avenue des Martyrs, 38043 Grenoble Cedex, France.
    Ponchut, Cyril
    Experimental Division, ESRF, Avenue des Martyrs, 38043 Grenoble Cedex, France.
    Characterisation of the charge sharing in pixellated Si detectors with single-photon processing readout2006Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. A 563, nr 1, s. 133-136Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Pixellated silicon detectors with a thickness of 300 µm and 700 µm bonded to the MEDIPIX2 readout chip have been characterised using a monoenergetic microbeam at the ESRF. The spectral response when a 10 x 10 µm2 wide 40 keV beam is centred on a single pixel is achieved. When the beam is scanned over the pixel, the charge sharing will increase when the beam approaches the border of the pixel. The experimental results have been verified by charge transport simulations and X-ray scattering simulations. Agreement between measurements and simulations can be achieved if a wider beam is assumed in the simulations. Widening of the absorption profile can to a large extent be explained by backscattering of lower energy photons by the tin/led bump-bounds below the detector. Widening of the detected beam is also an effect of angular alignment problems, especially on the 700 µm detector. Since the angel between the depth and a half pixel is only 2.2º, alignment of thick pixellated silicon detectors will be a problem to consider when designing X-ray imaging setups.

  • 46.
    Norlin, Börje
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Manuilskiy, Anatoliy
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Nilsson, Hans-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Fröjdh, Christer
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Material recognition with the Medipix photon counting colour X-ray system.2004Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 531, nr 1-2, s. 265-269Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An energy sensitive imaging system like Medipixl has proved to be promising in distinguishing different materials in an X-ray image of an object. We propose a general method utilising X-ray energy information for materialrecognition. For objects where the thickness of the materials is unknown, a convenient material parameter to identify is K = α12, which is the ratio of the logarithms of the measured transmissions In(t1)/In(t2). If a database of the parameter K for different materials and energies is created, this method can be used for material recognition independent of the thickness of the materials. Series of images of an object consisting of aluminium and silicon were taken with different energy thresholds. The X-ray absorption for silicon and aluminium is very similar for the range 40-60 keV and only differs for lower energies. The results show that it is possible to distinguish between aluminium and silicon on images achieved by Medipixl using a standard dental source. By decreasing the spatial resolution a better contrast between the materials was achieved. The resolution of contrasts shown by the histograms was close to the limit of the system due to the statistical noise of the signal.

  • 47.
    O'Nils, Mattias
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Thim, Jan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Norlin, Börje
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Oelmann, Bengt
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Threshold Modulation for Continuous Energy Resolution with Two Channels per Pixel in a Photon Counting X-ray Image Detector2009Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 607, nr 1, s. 236-239Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The introduction of energy resolution in X-ray image detectors will lead to tradeoffs between circuit complexity and spatial/energy resolution in the pixel design. The proposed method provides continuous energy resolution with only two energy channels per pixel, which is a comparable complexity to that of a window discriminator pixel like Medipix2. The paper illustrates the method and validates the method through analytical analysis and through simulation of real and synthetic data.

  • 48.
    Rofors, E.
    et al.
    Lund Univ, Lund.
    Perrey, H.
    Lund Univ, Lund; European Spallat Source ERIC, Lund.
    Al Jebali, R.
    European Spallat Source ERIC, Lund; Univ Glasgow, Glasgow, Lanark, Scotland.
    Armand, J. R. M.
    Univ Glasgow, Glasgow, Lanark, Scotland.
    Boyd, L.
    Univ Glasgow, Glasgow, Lanark, Scotland.
    Clemens, U.
    Forschungszentrum Julich, Julich, Germany.
    Desert, S.
    Univ Paris Saclay, Gif Sur Yvette, France.
    Engels, R.
    Forschungszentrum Julich, Julich, Germany.
    Fissum, K. G.
    Lund Univ, Lund; European Spallat Source ERIC, Lund.
    Frielinghaus, H.
    Forschungszentrum Julich, Julich, Germany.
    Gheorghe, C.
    Integrated Detector Elect AS, Oslo, Norway.
    Hall-Wilton, Richard
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion. European Spallat Source ERIC, Lund.
    Jaksch, S.
    Forschungszentrum Julich, Julich, Germany.
    Jalgen, A.
    Lund Univ, Lund.
    Kanaki, K.
    European Spallat Source ERIC, Lund.
    Kemmerling, G.
    Forschungszentrum Julich, Julich, Germany.
    Maulerova, V
    Lund Univ, Div Nucl Phys, Lund.
    Mauritzson, N.
    Lund Univ, Lund.
    Montgomery, R.
    Univ Glasgow, Glasgow, Lanark, Scotland.
    Scherzinger, J.
    Lund Univ, Lund; European Spallat Source ERIC, Lund; Univ Pisa, Pisa, Italy; INFN, Pisa, Italy.
    Seitz, B.
    Univ Glasgow, Glasgow, Lanark, Scotland.
    Response of a Li-glass/multi-anode photomultiplier detector to alpha-particles from Am-2412019Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 929, s. 90-96Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The response of a position-sensitive Li-glass scintillator detector to alpha-particles from a collimated Am-241 source scanned across the face of the detector has been measured. Scintillation light was read out by an 8 x 8 pixel multi-anode photomultiplier and the signal amplitude for each pixel has been recorded for every position on a scan. The pixel signal is strongly dependent on position and in general several pixels will register a signal (a hit) above a given threshold. The effect of this threshold on hit multiplicity is studied, with a view to optimize the single-hit efficiency of the detector.

  • 49.
    Scherzinger, J.
    et al.
    Division of Nuclear Physics, Lund University; Detector Group, European Spallation Source ERIC, SE-221 00 Lund.
    Al Jebali, R.
    SUPA School of Physics and Astronomy, University of Glasgow, Scotland.
    Annand, J. R. M.
    SUPA School of Physics and Astronomy, University of Glasgow, Scotland.
    Fissum, K. G.
    Division of Nuclear Physics, Lund University; Detector Group, European Spallation Source ERIC, SE-221 00 Lund.
    Hall-Wilton, Richard J.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för elektronikkonstruktion. Detector Group, European Spallation Source ERIC, SE-221 00 Lund.
    Kanaki, K.
    Detector Group, European Spallation Source ERIC, SE-221 00 Lund.
    Lundin, M.
    MAX IV Laboratory, Lund University.
    Nilsson, B.
    MAX IV Laboratory, Lund University; Detector Group, European Spallation Source ERIC, SE-221 00 Lund.
    Perrey, H.
    Detector Group, European Spallation Source ERIC, SE-221 00 Lund; Division of Nuclear Physics, Lund University.
    Rosborg, A.
    MAX IV Laboratory, Lund University.
    Svensson, H.
    MAX IV Laboratory, Lund University; Sweflo Engineering.
    The light-yield response of a NE-213 liquid-scintillator detector measured using 2–6 MeV tagged neutrons2016Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 840, s. 121-127Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The response of a NE-213 liquid-scintillator detector has been measured using tagged neutrons from 2 to 6 MeV originating from an Am/Be neutron source. The neutron energies were determined using the time-of-flight technique. Pulse-shape discrimination was employed to discern between gamma-rays and neutrons. The behavior of both the fast (35 ns) and the combined fast and slow (475 ns) components of the neutron scintillation-light pulses were studied. Three different prescriptions were used to relate the neutron maximum energy-transfer edges to the corresponding recoil-proton scintillation-light yields, and the results were compared to simulations. The overall normalizations of parametrizations which predict the fast or total light yield of the scintillation pulses were also tested. Our results agree with both existing data and existing parametrizations. We observe a clear sensitivity to the portion and length of the neutron scintillation-light pulse considered.

  • 50.
    Thim, Jan
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Norlin, Börje
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    O'Nils, Matthias
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Abdalla, Suliman
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Oelmann, Bengt
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Realizing increased sub-pixel spatial resolution in X-ray imaging using displaced multiple images2011Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 633, nr Suppl 1, s. S247-S249Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A method, generally called oversampling, to reach sub-pixel resolution by taking slightly displaced images of an object is investigated for X-ray applications. By mounting the sensor on a high precision step motor table it is possible to increase the spatial resolution from 55 ÎŒm×55 ÎŒm to at least 20 ÎŒm×20 ÎŒm, which is required for quality assurance measurements in several industry processes. The performance compared to physically smaller pixels is shown, and the effects of charge sharing on the method are investigated. The suggested method is relatively cost effective compared to using X-ray microscopy. © 2010 Elsevier B.V. All rights reserved.

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