P. Seller - Academia.edu (original) (raw)
Papers by P. Seller
Scientific reports, Jan 2, 2015
A new synchrotron-based technique for elemental imaging that combines radiography and fluorescenc... more A new synchrotron-based technique for elemental imaging that combines radiography and fluorescence spectroscopy has been developed and applied to study the spatial distribution of Ag, Zr and Mo in an Al alloy during heating and melting to 700, and then re-soldification. For the first time, multi-element distributions have been mapped independently and simultaneously, showing the dissolution of Ag- and Zr-rich particles during melting and the inter-dendritic segregation of Ag during re-solidification. The new technique is shown to have wide potential for metallurgical and materials science applications where the dynamics of elemental re-distribution and segregation in complex alloys is of importance.
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Radiation Physics and Chemistry, 2004
Because the Earth has a protective atmosphere that is opaque to many wavelengths, X-ray astronomy... more Because the Earth has a protective atmosphere that is opaque to many wavelengths, X-ray astronomy cannot be performed from the ground. It was not until the 1960s that astronomers had the technological capability to put their experiments at high enough altitudes to directly observe cosmic X-rays (Giacconi et al., 1962). Since that time a multitude of high-altitude balloons, rockets, and satellites have been launched to study the Universe in this wavelength region. Of the 108 missions flown, the majority of them concentrate on studying the Universe below 20 keV (Slavis, 2001). As a result, the hard X-ray region (20–100 keV) is still relatively unexplored. One instrument that will study the Universe in the hard X-ray region is the high energy replicated optics (HERO) balloon borne telescope being developed at Marshall Space Flight Center and the National Space Science and Technology Center. The HERO telescope consists of nested grazing incidence optics and several focal plane detectors. The full balloon payload will consist of 16 mirror modules each containing 15 nested shells (Ramsey et al., 2004). Each focal plane detector must exhibit a high photopeak quantum efficiency, good energy resolution, and good spatial resolution (B200mm). To sample the full mirror response the focal plane detector must have 128 128 pixels (Ramsey, 2001), although the sensitive portion of the mirrors’ response can be covered by 64 64 pixels. These focal plane requirements can be optimally met with a many-pixel cadmium–zinc–telluride (CdZnTe) array.
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Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1994
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Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1999
Abstract The techniques for calculating noise in electronic circuits are well known (P. Seller, N... more Abstract The techniques for calculating noise in electronic circuits are well known (P. Seller, Nucl. Instr. and Meth. A 408 (1998) 603). These have been used here to tabulate the output noise variance and the Equivalent input Noise Charge (ENC) for time-invariant filter circuits often used for reading out detector systems. This is followed by some comparisons of the performance of different filters.
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IEEE Transactions on Nuclear Science, 1995
A low-noise, low-power, 16-channel pre-amplifier/shaper IC designed at RAL in 1.5 μ CMOS is descr... more A low-noise, low-power, 16-channel pre-amplifier/shaper IC designed at RAL in 1.5 μ CMOS is described. The IC is designed to read out photodiodes which detect energy deposits in CsI scintillation bars. Each channel amplifies the input charge from a photodiode and shapes it with a 5-μs time constant (a requirement of the detectors). The peak of the shaped signal is
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Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment - NUCL INSTRUM METH PHYS RES A, 2001
Modules of a photon counting pixelated silicon X-ray detector have been built and tested. The mod... more Modules of a photon counting pixelated silicon X-ray detector have been built and tested. The modules have a uniform pixel size of 150×150μm over a silicon detector of 448×64pixels. The detector is solder bump bonded to readout chips and then onto a molybdenum cooling substrate. Several modules have been built and images obtained with X-rays sources. The detectors work at 200k photons per second per pixel giving a module counting rate of 6×109 photons per second. The modules are designed to be tiled to create larger arrays. The paper shows images obtained from the modules and describes a detector problem caused by adjacent pixels being shorted together.
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In this work, we present the results of a microscale X-ray mapping of a 2 mm thick CZT pixel dete... more In this work, we present the results of a microscale X-ray mapping of a 2 mm thick CZT pixel detector, with pixel pitches of 500 µm and 250 µm, using collimated synchrotron X-ray sources at the Diamond Light source (U. K.). The detector is dc coupled to a fast and low noise ASIC (PIXIE ASIC), characterized only by the preamplifier stage. A custom 16-channel digital readout electronics was used, able to perform online fast pulse shape and height analysis (PSHA), with low dead time and reasonable energy resolution at both low and high fluxes. The detector allows high bias voltage operation (> 5000 V/cm) and good energy resolution at room temperature (5.3 %, 2.3 % and 2.1 % FWHM at 22.1, 59.5 and 122.1 keV, respectively) by using fast pulse shaping with low dead time (300 ns). Charge sharing investigations were performed by using uncollimated and collimated X-ray sources with energies above and below the K-shell absorption energy of the CZT material. Collimated 10 × 10 µm synchrotro...
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Journal of Instrumentation
CdZnTe is a promising material for the current generation of free electron laser light sources an... more CdZnTe is a promising material for the current generation of free electron laser light sources and future laser-driven γ-ray sources which require detectors capable of high flux imaging at X-ray and γ-ray energies (> 10 keV) . However, at high fluxes CdZnTe has been shown to polarise due to hole trapping, leading to poor performance. Novel Redlen CdZnTe material with improved hole transport properties has been designed for high flux applications. Small pixel CdZnTe detectors were fabricated by Redlen Technologies and flip-chip bonded to PIXIE ASICs. An XIA Digital Gamma Finder PIXIE-16 system was used to digitise each of the nine analogue signals with a timing resolution of 10 ns. Pulse shape analysis was used to extract the rise times and amplitude of signals. These were measured as a function of applied bias voltage and used to calculate the mobility (μ) and mobility-lifetime (μτ) of electrons and holes in the material for three identical detectors. The measured values of the transport properties of electrons in the high-flux-capable material was lower than previously reported for Redlen CdZnTe material (μeτe ~ 1 × 10−3 cm2V−1 and μe ~ 1000 cm2V−1s−1) while the hole transport properties were found to have improved (μhτh ~ 3 × 10−4 cm2V−1 and μh ~ 100 cm2V−1s−1).
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Synchrotron Radiation News
Over the last decade, the High-Energy X-ray Imaging Technology (HEXITEC) detector system for spec... more Over the last decade, the High-Energy X-ray Imaging Technology (HEXITEC) detector system for spectroscopic imaging of hard X-rays and γ-rays has been developed by the Science & Technology Facilitie...
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Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
A prototype X-ray imaging system, using the principle of Tomographic Energy Dispersive Diffractio... more A prototype X-ray imaging system, using the principle of Tomographic Energy Dispersive Diffraction Imaging (TEDDI) has been developed at the University of Manchester's School of Materials. The non-destructive 3D imaging system makes use of a state of the art collimator array and a pixellated Si energy resolving detector. The new rapid TEDDI system is limited to thin, low density materials
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Journal of Instrumentation
ABSTRACT
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Physics in medicine and biology, Jan 3, 2016
In mammography, the reduction of scattered x-rays is vital due to the low contrast or small dimen... more In mammography, the reduction of scattered x-rays is vital due to the low contrast or small dimension of the details that are searched for. The typical method of doing so in current conventional mammography is the anti-scatter grid. The disadvantage of this method is the absorption of a proportion of the primary beam and therefore an increase in dose is required to compensate for the loss of counts. An alternative method is proposed, using quasi-monochromatic beams and a pixellated spectroscopic detector. As Compton-scattered x-rays lose energy in the scattering process, they are detected at a lower energy in the spectrum. Therefore the spectrum can be windowed around the monochromatic energy peak, removing the scattered x-rays from the image. The work presented here shows contrast improvement of up to 50% and contrast to noise ratio improvements of around 20% for scatter free imaging in comparison to full spectrum imaging. Contrast improvements of around 45% were found when compari...
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Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2009
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AIP Conference Proceedings, 1992
We describe the front end signal processing chip (HARP) being developed by the RD2 collaboration ... more We describe the front end signal processing chip (HARP) being developed by the RD2 collaboration for LHC detectors. The HARP chip, based around an analog memory, will provide data storage at LHC rates for 2 musec and allow stored data to be accessed for trigger rates of up to 50-100 KHz. We have tested two different prototypes of the final
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Journal of Instrumentation, 2014
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Journal of Instrumentation, 2014
ABSTRACT Semi-insulating wafers of GaAs material with a thickness of 500μm have been compensated ... more ABSTRACT Semi-insulating wafers of GaAs material with a thickness of 500μm have been compensated with chromium by Tomsk State University. Initial measurements have shown the material to have high resistivity (3 × 109Ωcm) and tests with pixel detectors on a 250 μm pitch produced uniform spectroscopic performance across an 80 × 80 pixel array. At present, there is a lack of detectors that are capable of operating at high X-ray fluxes (> 108 photons s-1 mm-2) in the energy range 5–50 keV. Under these conditions, the poor stopping power of silicon, as well as issues with radiation hardness, severely degrade the performance of traditional detectors. While high-Z materials such as CdTe and CdZnTe may have much greater stopping power, the formation of space charge within these detectors degrades detector performance. Initial measurements made with GaAs:Cr detectors suggest that many of its material properties make it suitable for these challenging conditions. In this paper the radiation hardness of the GaAs:Cr material has been measured on the B16 beam line at the Diamond Light Source synchrotron. Small pixel detectors were bonded to the STFC Hexitec ASIC and were irradiated with 3 × 108 photons s-1 mm-2 monochromatic 12 keV X-rays up to a maximum dose of 0.6 MGy. Measurements of the spectroscopic performance before and after irradiation have been used to assess the extent of the radiation damage.
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Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1994
Bookmarks Related papers MentionsView impact
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2011
... DS Judson a , Corresponding Author Contact Information , E-mail The Corresponding Author , AJ... more ... DS Judson a , Corresponding Author Contact Information , E-mail The Corresponding Author , AJ Boston a , PJ Coleman-Smith b , DM Cullen c , A. Hardie d , LJ Harkness a , LL Jones d , M. Jones a , I. Lazarus b , PJ Nolan a , V. Pucknell b , SV Rigby a , P ... [2] N. Luke, M. Amman ...
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Journal of Instrumentation, 2015
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Scientific reports, Jan 2, 2015
A new synchrotron-based technique for elemental imaging that combines radiography and fluorescenc... more A new synchrotron-based technique for elemental imaging that combines radiography and fluorescence spectroscopy has been developed and applied to study the spatial distribution of Ag, Zr and Mo in an Al alloy during heating and melting to 700, and then re-soldification. For the first time, multi-element distributions have been mapped independently and simultaneously, showing the dissolution of Ag- and Zr-rich particles during melting and the inter-dendritic segregation of Ag during re-solidification. The new technique is shown to have wide potential for metallurgical and materials science applications where the dynamics of elemental re-distribution and segregation in complex alloys is of importance.
Bookmarks Related papers MentionsView impact
Radiation Physics and Chemistry, 2004
Because the Earth has a protective atmosphere that is opaque to many wavelengths, X-ray astronomy... more Because the Earth has a protective atmosphere that is opaque to many wavelengths, X-ray astronomy cannot be performed from the ground. It was not until the 1960s that astronomers had the technological capability to put their experiments at high enough altitudes to directly observe cosmic X-rays (Giacconi et al., 1962). Since that time a multitude of high-altitude balloons, rockets, and satellites have been launched to study the Universe in this wavelength region. Of the 108 missions flown, the majority of them concentrate on studying the Universe below 20 keV (Slavis, 2001). As a result, the hard X-ray region (20–100 keV) is still relatively unexplored. One instrument that will study the Universe in the hard X-ray region is the high energy replicated optics (HERO) balloon borne telescope being developed at Marshall Space Flight Center and the National Space Science and Technology Center. The HERO telescope consists of nested grazing incidence optics and several focal plane detectors. The full balloon payload will consist of 16 mirror modules each containing 15 nested shells (Ramsey et al., 2004). Each focal plane detector must exhibit a high photopeak quantum efficiency, good energy resolution, and good spatial resolution (B200mm). To sample the full mirror response the focal plane detector must have 128 128 pixels (Ramsey, 2001), although the sensitive portion of the mirrors’ response can be covered by 64 64 pixels. These focal plane requirements can be optimally met with a many-pixel cadmium–zinc–telluride (CdZnTe) array.
Bookmarks Related papers MentionsView impact
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1994
Bookmarks Related papers MentionsView impact
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1999
Abstract The techniques for calculating noise in electronic circuits are well known (P. Seller, N... more Abstract The techniques for calculating noise in electronic circuits are well known (P. Seller, Nucl. Instr. and Meth. A 408 (1998) 603). These have been used here to tabulate the output noise variance and the Equivalent input Noise Charge (ENC) for time-invariant filter circuits often used for reading out detector systems. This is followed by some comparisons of the performance of different filters.
Bookmarks Related papers MentionsView impact
IEEE Transactions on Nuclear Science, 1995
A low-noise, low-power, 16-channel pre-amplifier/shaper IC designed at RAL in 1.5 μ CMOS is descr... more A low-noise, low-power, 16-channel pre-amplifier/shaper IC designed at RAL in 1.5 μ CMOS is described. The IC is designed to read out photodiodes which detect energy deposits in CsI scintillation bars. Each channel amplifies the input charge from a photodiode and shapes it with a 5-μs time constant (a requirement of the detectors). The peak of the shaped signal is
Bookmarks Related papers MentionsView impact
Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment - NUCL INSTRUM METH PHYS RES A, 2001
Modules of a photon counting pixelated silicon X-ray detector have been built and tested. The mod... more Modules of a photon counting pixelated silicon X-ray detector have been built and tested. The modules have a uniform pixel size of 150×150μm over a silicon detector of 448×64pixels. The detector is solder bump bonded to readout chips and then onto a molybdenum cooling substrate. Several modules have been built and images obtained with X-rays sources. The detectors work at 200k photons per second per pixel giving a module counting rate of 6×109 photons per second. The modules are designed to be tiled to create larger arrays. The paper shows images obtained from the modules and describes a detector problem caused by adjacent pixels being shorted together.
Bookmarks Related papers MentionsView impact
In this work, we present the results of a microscale X-ray mapping of a 2 mm thick CZT pixel dete... more In this work, we present the results of a microscale X-ray mapping of a 2 mm thick CZT pixel detector, with pixel pitches of 500 µm and 250 µm, using collimated synchrotron X-ray sources at the Diamond Light source (U. K.). The detector is dc coupled to a fast and low noise ASIC (PIXIE ASIC), characterized only by the preamplifier stage. A custom 16-channel digital readout electronics was used, able to perform online fast pulse shape and height analysis (PSHA), with low dead time and reasonable energy resolution at both low and high fluxes. The detector allows high bias voltage operation (> 5000 V/cm) and good energy resolution at room temperature (5.3 %, 2.3 % and 2.1 % FWHM at 22.1, 59.5 and 122.1 keV, respectively) by using fast pulse shaping with low dead time (300 ns). Charge sharing investigations were performed by using uncollimated and collimated X-ray sources with energies above and below the K-shell absorption energy of the CZT material. Collimated 10 × 10 µm synchrotro...
Bookmarks Related papers MentionsView impact
Journal of Instrumentation
CdZnTe is a promising material for the current generation of free electron laser light sources an... more CdZnTe is a promising material for the current generation of free electron laser light sources and future laser-driven γ-ray sources which require detectors capable of high flux imaging at X-ray and γ-ray energies (> 10 keV) . However, at high fluxes CdZnTe has been shown to polarise due to hole trapping, leading to poor performance. Novel Redlen CdZnTe material with improved hole transport properties has been designed for high flux applications. Small pixel CdZnTe detectors were fabricated by Redlen Technologies and flip-chip bonded to PIXIE ASICs. An XIA Digital Gamma Finder PIXIE-16 system was used to digitise each of the nine analogue signals with a timing resolution of 10 ns. Pulse shape analysis was used to extract the rise times and amplitude of signals. These were measured as a function of applied bias voltage and used to calculate the mobility (μ) and mobility-lifetime (μτ) of electrons and holes in the material for three identical detectors. The measured values of the transport properties of electrons in the high-flux-capable material was lower than previously reported for Redlen CdZnTe material (μeτe ~ 1 × 10−3 cm2V−1 and μe ~ 1000 cm2V−1s−1) while the hole transport properties were found to have improved (μhτh ~ 3 × 10−4 cm2V−1 and μh ~ 100 cm2V−1s−1).
Bookmarks Related papers MentionsView impact
Synchrotron Radiation News
Over the last decade, the High-Energy X-ray Imaging Technology (HEXITEC) detector system for spec... more Over the last decade, the High-Energy X-ray Imaging Technology (HEXITEC) detector system for spectroscopic imaging of hard X-rays and γ-rays has been developed by the Science & Technology Facilitie...
Bookmarks Related papers MentionsView impact
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
A prototype X-ray imaging system, using the principle of Tomographic Energy Dispersive Diffractio... more A prototype X-ray imaging system, using the principle of Tomographic Energy Dispersive Diffraction Imaging (TEDDI) has been developed at the University of Manchester's School of Materials. The non-destructive 3D imaging system makes use of a state of the art collimator array and a pixellated Si energy resolving detector. The new rapid TEDDI system is limited to thin, low density materials
Bookmarks Related papers MentionsView impact
Journal of Instrumentation
ABSTRACT
Bookmarks Related papers MentionsView impact
Physics in medicine and biology, Jan 3, 2016
In mammography, the reduction of scattered x-rays is vital due to the low contrast or small dimen... more In mammography, the reduction of scattered x-rays is vital due to the low contrast or small dimension of the details that are searched for. The typical method of doing so in current conventional mammography is the anti-scatter grid. The disadvantage of this method is the absorption of a proportion of the primary beam and therefore an increase in dose is required to compensate for the loss of counts. An alternative method is proposed, using quasi-monochromatic beams and a pixellated spectroscopic detector. As Compton-scattered x-rays lose energy in the scattering process, they are detected at a lower energy in the spectrum. Therefore the spectrum can be windowed around the monochromatic energy peak, removing the scattered x-rays from the image. The work presented here shows contrast improvement of up to 50% and contrast to noise ratio improvements of around 20% for scatter free imaging in comparison to full spectrum imaging. Contrast improvements of around 45% were found when compari...
Bookmarks Related papers MentionsView impact
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2009
Bookmarks Related papers MentionsView impact
AIP Conference Proceedings, 1992
We describe the front end signal processing chip (HARP) being developed by the RD2 collaboration ... more We describe the front end signal processing chip (HARP) being developed by the RD2 collaboration for LHC detectors. The HARP chip, based around an analog memory, will provide data storage at LHC rates for 2 musec and allow stored data to be accessed for trigger rates of up to 50-100 KHz. We have tested two different prototypes of the final
Bookmarks Related papers MentionsView impact
Journal of Instrumentation, 2014
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
Journal of Instrumentation, 2014
ABSTRACT Semi-insulating wafers of GaAs material with a thickness of 500μm have been compensated ... more ABSTRACT Semi-insulating wafers of GaAs material with a thickness of 500μm have been compensated with chromium by Tomsk State University. Initial measurements have shown the material to have high resistivity (3 × 109Ωcm) and tests with pixel detectors on a 250 μm pitch produced uniform spectroscopic performance across an 80 × 80 pixel array. At present, there is a lack of detectors that are capable of operating at high X-ray fluxes (> 108 photons s-1 mm-2) in the energy range 5–50 keV. Under these conditions, the poor stopping power of silicon, as well as issues with radiation hardness, severely degrade the performance of traditional detectors. While high-Z materials such as CdTe and CdZnTe may have much greater stopping power, the formation of space charge within these detectors degrades detector performance. Initial measurements made with GaAs:Cr detectors suggest that many of its material properties make it suitable for these challenging conditions. In this paper the radiation hardness of the GaAs:Cr material has been measured on the B16 beam line at the Diamond Light Source synchrotron. Small pixel detectors were bonded to the STFC Hexitec ASIC and were irradiated with 3 × 108 photons s-1 mm-2 monochromatic 12 keV X-rays up to a maximum dose of 0.6 MGy. Measurements of the spectroscopic performance before and after irradiation have been used to assess the extent of the radiation damage.
Bookmarks Related papers MentionsView impact
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1994
Bookmarks Related papers MentionsView impact
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2011
... DS Judson a , Corresponding Author Contact Information , E-mail The Corresponding Author , AJ... more ... DS Judson a , Corresponding Author Contact Information , E-mail The Corresponding Author , AJ Boston a , PJ Coleman-Smith b , DM Cullen c , A. Hardie d , LJ Harkness a , LL Jones d , M. Jones a , I. Lazarus b , PJ Nolan a , V. Pucknell b , SV Rigby a , P ... [2] N. Luke, M. Amman ...
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Journal of Instrumentation, 2015
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