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Fröjdh, Erik
Publications (10 of 27) Show all publications
Campbell, M., Alozy, J., Ballabriga, R., Fröjdh, E., Heijne, E., Llopart, X., . . . Wong, W. (2016). Towards a new generation of pixel detector readout chips. Paper presented at 17th International Workshop on Radiation Imaging Detectors, JUN 28-JUL 02, 2015, DESY, Hamburg, GERMANY. Journal of Instrumentation, 11(1), Article ID C01007.
Open this publication in new window or tab >>Towards a new generation of pixel detector readout chips
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2016 (English)In: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 11, no 1, article id C01007Article in journal (Refereed) Published
Abstract [en]

The Medipix3 Collaboration has broken new ground in spectroscopic X-ray imaging and in single particle detection and tracking. This paper will review briefly the performance and limitations of the present generation of pixel detector readout chips developed by the Collaboration. Through Silicon Via technology has the potential to provide a significant improvement in the tile-ability and more flexibility in the choice of readout architecture. This has been explored in the context of 3 projects with CEA-LETI using Medipix3 and Timepix3 wafers. The next generation of chips will aim to provide improved spectroscopic imaging performance at rates compatible with human CT. It will also aim to provide full spectroscopic images with unprecedented energy and spatial resolution. Some of the opportunities and challenges posed by moving to a more dense CMOS process will be discussed.

Keywords
Solid state detectors, Hybrid detectors, Electronic detector readout concepts (solid-state)
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:miun:diva-27820 (URN)10.1088/1748-0221/11/01/C01007 (DOI)000371469800007 ()2-s2.0-84956952310 (Scopus ID)STC (Local ID)STC (Archive number)STC (OAI)
Conference
17th International Workshop on Radiation Imaging Detectors, JUN 28-JUL 02, 2015, DESY, Hamburg, GERMANY
Available from: 2016-06-08 Created: 2016-06-07 Last updated: 2017-08-09Bibliographically approved
Fröjdh, E. (2015). Hybrid pixel detectors: Characterization and optimization. (Doctoral dissertation). Sundsvall: Mid Sweden University
Open this publication in new window or tab >>Hybrid pixel detectors: Characterization and optimization
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Place, publisher, year, edition, pages
Sundsvall: Mid Sweden University, 2015. p. 209
Series
Mid Sweden University doctoral thesis, ISSN 1652-893X ; 228
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:miun:diva-26794 (URN)STC (Local ID)978-91-88025-37-1 (ISBN)STC (Archive number)STC (OAI)
Public defence
2015-09-08, O102, Sundsvall, 13:00 (English)
Supervisors
Note

Vid tidpunkten för disputationen var följande delarbete opublicerat: delarbete 8 inskickat.

At the time of the doctoral defence the following paper was unpublished: paper 8 submitted.

Available from: 2016-01-04 Created: 2016-01-04 Last updated: 2018-09-10Bibliographically approved
George, S. P., Severino, C. T., Fröjdh, E., Murtas, F. & Silari, M. (2015). Measurement of an accelerator based mixed field with a Timepix detector. Journal of Instrumentation, 10, Article ID P03005.
Open this publication in new window or tab >>Measurement of an accelerator based mixed field with a Timepix detector
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2015 (English)In: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 10, article id P03005Article in journal (Refereed) Published
Abstract [en]

We present an analysis of a high energy mixed field taken with a Timepix chip at the CERF facility at CERN. The Timepix is an active array of 65K energy measuring pixels which allows visualization and energy measurement of the tracks created by individual particles. This allows characteristics of interest such as the LET and angular distributions of the incoming tracks to be calculated, as well as broad morphological track categories based on pattern recognition techniques. We compute and compare LET-like and angular information for different morphological track categories. Morphological track categories are found to possess overlapping LET and energy spectra, however the approaches are found to be complementary with morphological clustering yielding information which is indistinguishable on the basis of LET alone. The use of the Timepix as an indirect monitoring device outside of the primary beam at CERF is briefly discussed.

Keywords
Dosimetry concepts and apparatus, Particle tracking detectors (Solid-state detectors), Pattern recognition, cluster finding, calibration and fitting methods
National Category
Electrical Engineering, Electronic Engineering, Information Engineering Physical Sciences
Identifiers
urn:nbn:se:miun:diva-25654 (URN)10.1088/1748-0221/10/03/P03005 (DOI)000357944500055 ()2-s2.0-84924264777 (Scopus ID)
Available from: 2015-08-28 Created: 2015-08-18 Last updated: 2017-12-04Bibliographically approved
Norlin, B., Reza, S., Krapohl, D., Fröjdh, E. & Thungström, G. (2015). Readout cross-talk for alpha-particle measurements in a pixelated sensor system. Paper presented at 16th International Workshop on Radiation Imaging Detectors (IWORID2014). Journal of Instrumentation, 10, Article ID C05025.
Open this publication in new window or tab >>Readout cross-talk for alpha-particle measurements in a pixelated sensor system
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2015 (English)In: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 10, article id C05025Article in journal (Refereed) Published
Abstract [en]

Simulations in Medici are performed to quantify crosstalk and charge sharing in a hybrid pixelated silicon detector. Crosstalk and charge sharing degrades the spatial and spectral resolution of single photon processing X-ray imaging systems. For typical medical X-ray imaging applications, the process is dominated by charge sharing between the pixels in the sensor. For heavier particles each impact generates a large amount of charge and the simulation seems to over predict the charge collection efficiency. This indicates that some type of non modelled degradation of the charge transport efficiency exists, like the plasma effect where the plasma might shield the generated charges from the electric field and hence distorts the charge transport process. Based on the simulations it can be reasoned that saturation of the amplifiers in the Timepix system might generate crosstalk that increases the charge spread measured from ion impact on the sensor.

Keywords
Charge transport and multiplication in solid media; Hybrid detectors; X-ray detec- tors; Imaging spectroscopy
National Category
Physical Sciences Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:miun:diva-24977 (URN)10.1088/1748-0221/10/05/C05025 (DOI)000357993300025 ()2-s2.0-84930958451 (Scopus ID)STC (Local ID)STC (Archive number)STC (OAI)
Conference
16th International Workshop on Radiation Imaging Detectors (IWORID2014)
Available from: 2015-05-25 Created: 2015-05-25 Last updated: 2017-12-04Bibliographically approved
Fröjdh, E., Bisello, F., Campbell, M., Damet, J., Hamann, E., Koenig, T., . . . Zuber, M. (2015). Spectral response of the energy-binning Dosepix ASIC coupled to a 300 mu m silicon sensor under high fluxes of synchrotron radiation. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 804, 43-49
Open this publication in new window or tab >>Spectral response of the energy-binning Dosepix ASIC coupled to a 300 mu m silicon sensor under high fluxes of synchrotron radiation
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2015 (English)In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 804, p. 43-49Article in journal (Refereed) Published
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.

Keywords
Hybrid pixel detector, Time over threshold, Energy binning, X-ray dosimetry
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:miun:diva-26519 (URN)10.1016/j.nima.2015.09.018 (DOI)000364133700005 ()2-s2.0-84943514621 (Scopus ID)STC (Local ID)STC (Archive number)STC (OAI)
Available from: 2015-12-16 Created: 2015-12-16 Last updated: 2017-12-01Bibliographically approved
Fröjdh, E., Campbell, M., De Gaspari, M., Kulis, S., Llopart, X., Poikela, T. & Tlustos, L. (2015). Timepix3: first measurements and characterization of a hybrid-pixel detector working in event driven mode. Journal of Instrumentation, 10, Article ID C01039.
Open this publication in new window or tab >>Timepix3: first measurements and characterization of a hybrid-pixel detector working in event driven mode
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2015 (English)In: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 10, article id C01039Article in journal (Refereed) Published
Abstract [en]

Timepix3 is a hybrid pixel detector readout chip. It features a data driven readout mode where the chip sends out a data packet containing pixel coordinate, time over threshold and time of arrival immediately after the hit is processed by the pixel. The maximum hit rate is 40 Mhits/cm(2)/s with a minimum time step in the arrival time measurement of 1.56 ns. The pixel matrix consist of 256 x 256 square pixels at a 55 m m pitch and the pixel front end noise is 61 e(-) RMS. In this paper we present the first radiation measurements with Timepix3 bump bonded to a 300 m m thick silicon sensor. The chip is calibrated per pixel, using internal test pulses and the calibration is verified using X-ray fluorescence. The energy resolution, threshold dispersion and gain dispersion is measured. The energy resolution in time over threshold mode under normal operation conditions is 4.07 keV FWHM at 59.5 keV. At 10.5 keV an energy resolution of 0.72 keV FWHM was achieved in photon counting mode and in time over threshold mode, by optimizing the energy response, we achieved a 1.38 keV FWHM. We also investigate the time walk and present first results on using the time information for track reconstruction.

Keywords
Solid state detectors, X-ray detectors, Hybrid detectors
National Category
Engineering and Technology
Identifiers
urn:nbn:se:miun:diva-26550 (URN)10.1088/1748-0221/10/01/C01039 (DOI)000362261900026 ()2-s2.0-84943415877 (Scopus ID)STC (Local ID)STC (Archive number)STC (OAI)
Available from: 2015-12-16 Created: 2015-12-16 Last updated: 2017-12-01Bibliographically approved
Schübel, A., Krapohl, D., Fröjdh, E., Fröjdh, C. & Thungström, G. (2014). A Geant4 based framework for pixel detector simulation. Paper presented at 16th International Workshop on Radiation Imaging Detectors. Journal of Instrumentation, 9(12), Article ID C12018.
Open this publication in new window or tab >>A Geant4 based framework for pixel detector simulation
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2014 (English)In: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 9, no 12, article id C12018Article in journal (Refereed) Published
Abstract [en]

The output from a hybrid pixel detector depends on the interaction of the radiation with the sensor material, the transport of the resulting charge in the sensor, the pulse processing in the readout circuit and processing of the resulting signal. In order to understand the full behaviour of the device and to predict the performance of future devices it is important to have a framework that can simulate the entire process in the detector system.Geant4 is a Monte Carlo based toolkit for simulation of particle interaction with matter which is developed and actively used for CERN experiments and detector development [1]. By extending the Monte Carlo code in Geant4 with a charge carrier transport model of the sensor material and basic amplifier functionality as well as read out logic, a simulation of the complete detector system is possible.The MEDIPIX is a state of the art hybrid pixel detector that allows bonding of a wide range of sensor materials [2,3]. Simulation models have been developed and tested for different chips from the MEDIPIX family. The simulation is defined using configuration files to set the geometry, sensor material properties, number of pixels, pixel pitch and chip properties. Source properties as well as filters and objects in the beam can be added for different experimental set-ups. The interaction of radiation with the sensor is taken into account in the transport of the charge carriers in the sensor material and a current induced in the pixel electrode that triggers an amplifier response. Simulation results have been verified with X-ray fluorescence and radioactive sources using MEDIPIX family chips. In this paper we present the developed simulation framework and first results.

Keywords
Performance of high energy physics detectors, Simulation methods and programs, Software architectures (event data models, frameworks and databases)
National Category
Accelerator Physics and Instrumentation
Identifiers
urn:nbn:se:miun:diva-23708 (URN)10.1088/1748-0221/9/12/C12018 (DOI)000351342900002 ()2-s2.0-84918823479 (Scopus ID)STC (Local ID)STC (Archive number)STC (OAI)
Conference
16th International Workshop on Radiation Imaging Detectors
Available from: 2014-12-12 Created: 2014-12-12 Last updated: 2017-12-05Bibliographically approved
Fröjdh, E., Ballabriga, R., Campbell, M., Fiederle, M., Hamann, E., Koenig, T., . . . Zuber, M. (2014). Count rate linearity and spectral response of the Medipix3RX chip coupled to a 300μm silicon sensor under high flux conditions. Journal of Instrumentation, 9(4), Art. no. C04028
Open this publication in new window or tab >>Count rate linearity and spectral response of the Medipix3RX chip coupled to a 300μm silicon sensor under high flux conditions
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2014 (English)In: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 9, no 4, p. Art. no. C04028-Article in journal (Refereed) Published
Abstract [en]

For clinical X-ray imaging, the detector performance under high flux conditions is very important, with typical flux rates for modern CT systems reaching 109 photons s-1 mm-2 in the direct beam. In addition, for spectral imaging a good energy resolution under these conditions is needed. This poses difficulties, since pulse pileup in the pixel electronics does not only affect the count rate, leading to a deviation from the otherwise linear behavior, but also degrades the spectral response of the detector, making k-edge subtraction and other contrast enhancement techniques less efficient. In this paper, we investigate the count rate capabilities and the energy response of the Medipix3RX chip under high flux conditions using 10 keV monochromatic photons. © CERN 2014.

Keywords
Hybrid detectors, X-ray detectors
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:miun:diva-22044 (URN)10.1088/1748-0221/9/04/C04028 (DOI)000336123800028 ()2-s2.0-84899579747 (Scopus ID)STC (Local ID)STC (Archive number)STC (OAI)
Note

Language of Original Document: English

Available from: 2014-06-02 Created: 2014-05-30 Last updated: 2017-12-05Bibliographically approved
De Gaspari, M., Alozy, J., Ballabriga, R., Campbell, M., Fröjdh, E., Idarraga, J., . . . Wong, W. (2014). Design of the analog front-end for the Timepix3 and Smallpix hybrid pixel detectors in 130 nm CMOS technology. Journal of Instrumentation, 9, Art. no. C01037
Open this publication in new window or tab >>Design of the analog front-end for the Timepix3 and Smallpix hybrid pixel detectors in 130 nm CMOS technology
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2014 (English)In: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 9, p. Art. no. C01037-Article in journal (Refereed) Published
Abstract [en]

This paper describes a front-end for hybrid pixel readout chips, which was developed for the Timepix3 and Smallpix ASICs. The front-end contains a single-ended preamplifier with a structure for leakage current compensation which can handle both signal polarities, and a single-threshold discriminator with compensation for pixel-to-pixel mismatch. Preamplifier and discriminator are required to be fast, to allow a Time-Of-Arrival (TOA) measurement with a resolution of 1.56 ns. Time-Over-Threshold (TOT) is also measured; the monotonicity of TOT with respect to the input charge is greatly improved as compared to the previous Timepix chip. The analog area is only 55 μm × 13.5 μm. Timepix3 has already been fabricated and the first test results are also presented in this paper.

Keywords
Front-end electronics for detector readout Electronic detector readout concepts (solid-state) Analogue electronic circuits Pixilated detectors and associated VLSI electronics
National Category
Engineering and Technology
Identifiers
urn:nbn:se:miun:diva-21131 (URN)10.1088/1748-0221/9/01/C01037 (DOI)000332307000037 ()2-s2.0-84893070480 (Scopus ID)STC (Local ID)STC (Archive number)STC (OAI)
Available from: 2014-01-23 Created: 2014-01-23 Last updated: 2017-08-15Bibliographically approved
Krapohl, D., Fröjdh, C., Fröjdh, E., Maneuski, D. & Nilsson, H.-E. (2013). Investigation of charge collection in a CdTe-Timepix detector. Paper presented at 14th International Workshop on Radiation Imaging Detectors (iWoRID 2012); 20-25 June 2012; Figueira da Foz, Portugal.. Journal of Instrumentation, 8(May), Art. no. C05003
Open this publication in new window or tab >>Investigation of charge collection in a CdTe-Timepix detector
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2013 (English)In: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 8, no May, p. Art. no. C05003-Article in journal (Refereed) Published
Abstract [en]

Energy calibration of CdTe detectors is usually done using known reference sources disregarding the exact amount of charge that is collected in the pixels. However, to compare detector and detector model the quantity of charge collected is needed. We characterize the charge collection in a CdTe detector comparing test pulses, measured data and an improved TCAD simulation model [1]. The 1 mm thick detector is bump-bonded to a TIMEPIX chip and operating in Time-over-Threshold (ToT) mode. The resistivity in the simulation was adjusted to match the detector properties setting a deep intrinsic donor level [2]. This way it is possible to adjust properties like trap concentration, electron/hole lifetime and mobility in the simulation characterizing the detector close to measured data cite [3].

Keywords
Charge induction; solid state detectors; x-ray detectors; models and simulations
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:miun:diva-18946 (URN)10.1088/1748-0221/8/05/C05003 (DOI)000320726000003 ()2-s2.0-84878342633 (Scopus ID)STC (Local ID)STC (Archive number)STC (OAI)
Conference
14th International Workshop on Radiation Imaging Detectors (iWoRID 2012); 20-25 June 2012; Figueira da Foz, Portugal.
Available from: 2013-05-16 Created: 2013-05-16 Last updated: 2017-12-06Bibliographically approved
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