2,858 research outputs found
Towards a single-photon energy-sensitive pixel readout chip: pixel level ADCs and digital readout circuitry
Unlike conventional CMOS imaging, a single\ud
photon imager detects each individual photon impinging on\ud
a detector, accumulating the number of photons during a\ud
certain time window and not the charge generated by the all\ud
the photons hitting the detector during said time window.\ud
The latest developments in the semiconductor industry\ud
are allowing faster and more complex chips to be designed\ud
and manufactured. With these developments in mind we are\ud
working towards the next step in single photon X-ray imaging:\ud
energy sensitive pixel readout chips. The goal is not only\ud
to detect and count individual photons, but also to measure\ud
the charge deposited in the detector by each photon, and\ud
consequently determine its energy. Basically, we are aiming\ud
at a spectrometer-in-a-pixel, or a âcolor X-ray cameraâ.\ud
The approach we have followed towards this goal is the\ud
design of small analog-to-digital-converters at the pixel level,\ud
together with a very fast digital readout from the pixels to\ud
the periphery of the chip, where the data will be transmitted\ud
off-chip.\ud
We will present here the design and measurement on prototype\ud
chips of two different 4-bit pixel level ADCs. The\ud
ADCs are optimized for very small area and low power, with\ud
a resolution of 4-bits and a sample rate of 1 Msample/s. The\ud
readout architecture is based around current-mode sense\ud
amplifiers and asynchronous token-passing between the pixels.\ud
This is done in order to achieve event-by-event readout\ud
and, consequently, on-line imaging. We need to read eventby-\ud
event (photon-by-photon), because we cannot have memory\ud
on the pixels due to obvious size constraints. We use\ud
current-mode sense amplifiers because they perform very\ud
well in similar applications as very fast static-RAM readout
Design of pixel-level ADCs for energy-sensitive hybrid pixel detectors
Single-photon counting hybrid pixel detectors have shown\ud
to be a valid alternative to other types of X-ray imaging\ud
devices due to their high sensitivity, low noise, linear behavior\ud
and wide dynamic range. One important advantage of these\ud
devices is the fact that detector and readout electronics are\ud
manufactured separately. This allows the use of industrial\ud
state-of-the-art CMOS processes to make the readout\ud
electronics, combined with a free choice of detector material\ud
(high resistivity Silicon, GaAs or other). By measuring not\ud
only the number of X-ray photons but also their energies (or\ud
wavelengths), the information content of the image increases,\ud
given the same X-ray dose. We have studied several\ud
possibilities of adding energy sensitivity to the single photon\ud
counting capability of hybrid pixel detectors, by means of\ud
pixel-level analog-to-digital converters. We show the results of\ud
simulating different kinds of analog-to-digital converters in\ud
terms of power, area and speed
Recent X-ray hybrid CMOS detector developments and measurements
The Penn State X-ray detector lab, in collaboration with Teledyne Imaging
Sensors (TIS), have progressed their efforts to improve soft X-ray Hybrid CMOS
detector (HCD) technology on multiple fronts. Having newly acquired a Teledyne
cryogenic SIDECAR ASIC for use with HxRG devices, measurements were performed
with an H2RG HCD and the cooled SIDECAR. We report new energy resolution and
read noise measurements, which show a significant improvement over room
temperature SIDECAR operation. Further, in order to meet the demands of future
high-throughput and high spatial resolution X-ray observatories, detectors with
fast readout and small pixel sizes are being developed. We report on
characteristics of new X-ray HCDs with 12.5 micron pitch that include in-pixel
CDS circuitry and crosstalk-eliminating CTIA amplifiers. In addition, PSU and
TIS are developing a new large-scale array Speedster-EXD device. The original
64 x 64 pixel Speedster-EXD prototype used comparators in each pixel to enable
event driven readout with order of magnitude higher effective readout rates,
which will now be implemented in a 550 x 550 pixel device. Finally, the
detector lab is involved in a sounding rocket mission that is slated to fly in
2018 with an off-plane reflection grating array and an H2RG X-ray HCD. We
report on the planned detector configuration for this mission, which will
increase the NASA technology readiness level of X-ray HCDs to TRL 9.Comment: 12 pages, 11 figures, appears in Proc. SPIE 2017. error in reported
detector thickness, changed from 200 microns to 100 micron
Pixel Detectors
Pixel detectors for precise particle tracking in high energy physics have
been developed to a level of maturity during the past decade. Three of the LHC
detectors will use vertex detectors close to the interaction point based on the
hybrid pixel technology which can be considered the state of the art in this
field of instrumentation. A development period of almost 10 years has resulted
in pixel detector modules which can stand the extreme rate and timing
requirements as well as the very harsh radiation environment at the LHC without
severe compromises in performance. From these developments a number of
different applications have spun off, most notably for biomedical imaging.
Beyond hybrid pixels, a number of monolithic or semi-monolithic developments,
which do not require complicated hybridization but come as single sensor/IC
entities, have appeared and are currently developed to greater maturity. Most
advanced in terms of maturity are so called CMOS active pixels and DEPFET
pixels. The present state in the construction of the hybrid pixel detectors for
the LHC experiments together with some hybrid pixel detector spin-off is
reviewed. In addition, new developments in monolithic or semi-monolithic pixel
devices are summarized.Comment: 14 pages, 38 drawings/photographs in 21 figure
Trends in Pixel Detectors: Tracking and Imaging
For large scale applications, hybrid pixel detectors, in which sensor and
read-out IC are separate entities, constitute the state of the art in pixel
detector technology to date. They have been developed and start to be used as
tracking detectors and also imaging devices in radiography, autoradiography,
protein crystallography and in X-ray astronomy. A number of trends and
possibilities for future applications in these fields with improved
performance, less material, high read-out speed, large radiation tolerance, and
potential off-the-shelf availability have appeared and are momentarily matured.
Among them are monolithic or semi-monolithic approaches which do not require
complicated hybridization but come as single sensor/IC entities. Most of these
are presently still in the development phase waiting to be used as detectors in
experiments. The present state in pixel detector development including hybrid
and (semi-)monolithic pixel techniques and their suitability for particle
detection and for imaging, is reviewed.Comment: 10 pages, 15 figures, Invited Review given at IEEE2003, Portland,
Oct, 200
X-ray analog pixel array detector for single synchrotron bunch time-resolved imaging
Dynamic x-ray studies may reach temporal resolutions limited by only the
x-ray pulse duration if the detector is fast enough to segregate synchrotron
pulses. An analog integrating pixel array detector with in-pixel storage and
temporal resolution of around 150 ns, sufficient to isolate pulses, is
presented. Analog integration minimizes count-rate limitations and in-pixel
storage captures successive pulses. Fundamental tests of noise and linearity as
well as high-speed laser measurements are shown. The detector resolved
individual bunch trains at the Cornell High Energy Synchrotron Source (CHESS)
at levels of up to 3.7x10^3 x-rays/pixel/train. When applied to turn-by-turn
x-ray beam characterization single-shot intensity measurements were made with a
repeatability of 0.4% and horizontal oscillations of the positron cloud were
detected. This device is appropriate for time-resolved Bragg spot single
crystal experiments.Comment: 9 pages, 11 figure
2D Detectors for Particle Physics and for Imaging Applications
The demands on detectors for particle detection as well as for medical and
astronomical X-ray imaging are continuously pushing the development of novel
pixel detectors. The state of the art in pixel detector technology to date are
hybrid pixel detectors in which sensor and read-out integrated circuits are
processed on different substrates and connected via high density interconnect
structures. While these detectors are technologically mastered such that large
scale particle detectors can be and are being built, the demands for improved
performance for the next generation particle detectors ask for the development
of monolithic or semi-monolithic approaches. Given the fact that the demands
for medical imaging are different in some key aspects, developments for these
applications, which started as particle physics spin-off, are becomming rather
independent. New approaches are leading to novel signal processing concepts and
interconnect technologies to satisfy the need for very high dynamic range and
large area detectors. The present state in hybrid and (semi-)monolithic pixel
detector development and their different approaches for particle physics and
imaging application is reviewed
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