Electrons Rms Research Articles

IDeF-X HDBD: Low-Noise ASIC for Imaging Spectroscopy With Semiconductor Detectors in Space Science Applications

We present the IDeF-X HDBD integrated circuit, our latest 32-channel application specified integrated circuit devoted to semiconductor photon counting X-ray detectors, designed to read charges ranging from −40 to 40 fC. The chip reaches an equivalent noise charge (ENC) floor of 17 electrons rms and is optimized for low input capacitance (< 10 pF). Each channel is based on an optimized charge sensitive amplifier (CSA) followed by a CR-RC <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> filter and a peak detector with a power consumption of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$850 ~\mu \text{W}$ </tex-math></inline-formula> /channel. Gain and shaping times are tunable. This circuit has been designed with radiation mitigation techniques to meet space application requirements. This ASIC can read either cadmium telluride or silicon detectors for imaging-spectroscopy applications. An energy resolution of 230-eV FHWM at 6 keV and a low-level threshold of 1.2 keV were demonstrated with a single pixel silicon drift detector connected to one channel.

X–ᵞ-Ray Spectroscopy With a CdTe Pixel Detector and SIRIO Preamplifier at Deep Submicrosecond Signal-Processing Time

Advanced scientific and industrial applications based on Xand y-ray spectroscopic imaging need systems able to handle high incoming radiation flux (>1 Mcount/s) and, therefore, requiring processing of radiation detector signals in less than 1 μs. The design and realization of very fast systems with high spatial and energy resolution still presents a complex challenge and it is the objective of the most recent research worldwide. Since room-temperature operation and high absorption efficiency (up to 100 keV of photon energy) are required for many applications, in addition to high energy resolution, cadmium telluride (CdTe) or CdZnTe detectors are the main choice for the task. In this framework, we have developed a research-grade spectroscopic system based on a pixel CdTe detector coupled to an ultralow noise custom charge preamplifier. The detector is 1 mm thick with 0.75 mm × 0.75 mm pixels with Schottky junction; the front-end electronics is SIRIO-6, a CMOS charge preamplifier specifically designed to have ultralow noise and fast response. The goal of this work is to study the spectroscopic capability of a CdTe pixel detector, suitable for spectroscopic imaging, at very short signal-processing times. Deep submicrosecond X-y-ray spectroscopy has been successfully accomplished using a trapezoidal pulse shaping with a 50-ns flat top and peaking times ranging from 1 μs down to 50 ns. At room temperature, intrinsic energy resolutions [pulser full-width at half-maximum (FWHM)] from 205 eV (19.6 electrons rms) at 1 μs to 392 eV (37.6 electrons rms) at 50 ns have been obtained and the FWHMs of the <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">241</sup> Am 59.54 keV line from 472 eV at 1 μs to 617 eV at 50 ns peaking time have been measured, and, therefore, verifying the system capability to reach high energy resolution even at such short signal-processing times. The effects of very short signal-processing times on the electronic noise, ballistic deficit, and system linearity have been measured and discussed.

Predicting the effect of radiation damage on dark current in a space-qualified high performance CMOS image sensor

The CIS115 is a Teledyne-e2v CMOS image sensor with 1504 × 2000 pixels of 7 μm pitch. It has a high optical quantum efficiency owing to a multi-layer anti-reflective coating and its backside illuminated construction, and low dark current due to its pinned photodiode 4T pixel architecture. The sensor operates in rolling shutter mode with a frame rate of up to 7.5 fps (if using the whole array), and has a low readout noise of ∼5 electrons rms. The CIS115 has been selected for use within the JANUS instrument, which is a high resolution camera due to launch on board ESA's JUpiter ICy moons Explorer (JUICE) spacecraft in 2022. After an interplanetary transit time of over 7 years, JUICE will spend 3.5 years touring the Jovian system, studying three of the Galilean moons in particular: Ganymede, Callisto and Europa. During this latter part of the mission, the spacecraft and hence the CIS115 sensor will be subjected to the significant levels of trapped radiation surrounding Jupiter. Gamma and proton irradiation campaigns have therefore been undertaken in order to evaluate both ionising and non-ionising dose effects on the CIS115's dark current performance. Characterisations were carried out at expected mission operating temperatures (−35 ± 10̂C) both prior to and post-irradiation. Models of the resulting degradation in dark current behaviour will be combined with expected doses during the JUICE mission in order to predict the performance of the CIS115 at the mission end-of-life.

Toward fast, low-noise charge-coupled devices for Lynx

Lynx requires large-format x-ray imaging detectors with performance at least as good as the best current-generation devices but with much higher readout rates. We are investigating an advanced charge-coupled device (CCD) detector architecture under development at MIT Lincoln Laboratory for use in the Lynx high-definition x-ray imager and x-ray grating spectrometer instruments. This architecture features a CMOS-compatible detector integrated with parallel CMOS signal processing chains. Fast, low-noise amplifiers and highly parallel signal processing provide the high frame rates required. CMOS-compatibility of the CCD enables low-power charge transfer and signal processing. We report on the performance of CMOS-compatible test CCDs read at pixel rates up to 5.0 Mpix s − 1 (50 times faster than Chandra ACIS CCDs), with transfer clock swings as low as 1.0-V peak-to-peak (power/gate-area comparable to ACIS CCDs at 100 times the parallel transfer rate). We measure read noise of 4.6 electrons RMS at 2.5 MHz and x-ray spectral resolution better than 150-eV full-width at half maximum at 5.9 keV for single-pixel events. We report charge transfer efficiency measurements and demonstrate that buried channel trough implants as narrow as 0.8 μm are effective in improving charge transfer performance. We find that the charge transfer efficiency of these devices drops significantly as detector temperature is reduced from ∼ − 30 ° C to −60 ° C. We point out the potential of previously demonstrated curved-detector fabrication technology for simplifying the design of the Lynx high-definition imager. We discuss the expected detector radiation tolerance at these relatively high transfer rates. Finally, we note that the high pixel “aspect ratio” (depletion depth: pixel size ≈9 ∶ 1) of our test devices is similar to that expected for Lynx detectors and discuss implications of this geometry for x-ray performance and noise requirements.

Development of slew-rate-limited time-over-threshold (ToT) ASIC for a multi-channel silicon-based ion detector

High-resolution Elastic Recoil Detection Analysis (HERDA), which consists of a 90̂ sector magnetic spectrometer and a position-sensitive detector (PSD), is a method of quantitative hydrogen analysis. In order to increase sensitivity, a HERDA system using a multi-channel silicon-based ion detector has been developed. Here, as a parallel and fast readout circuit from a multi-channel silicon-based ion detector, a slew-rate-limited time-over-threshold (ToT) application-specific integrated circuit (ASIC) was designed, and a new slew-rate-limited ToT method is proposed. The designed ASIC has 48 channels and each channel consists of a preamplifier, a slew-rate-limited shaping amplifier, which makes ToT response linear, and a comparator. The measured equivalent noise charges (ENCs) of the preamplifier, the shaper, and the ToT on no detector capacitance were 253±21, 343±46, and 560±56 electrons RMS, respectively. The spectra from a 241Am source measured using a slew-rate-limited ToT ASIC are also reported.

Development of new CdZnTe detectors for room-temperature high-flux radiation measurements.

Recently, CdZnTe (CZT) detectors have been widely proposed and developed for room-temperature X-ray spectroscopy even at high fluxes, and great efforts have been made on both the device and the crystal growth technologies. In this work, the performance of new travelling-heater-method (THM)-grown CZT detectors, recently developed at IMEM-CNR Parma, Italy, is presented. Thick planar detectors (3 mm thick) with gold electroless contacts were realised, with a planar cathode covering the detector surface (4.1 mm × 4.1 mm) and a central anode (2 mm × 2 mm) surrounded by a guard-ring electrode. The detectors, characterized by low leakage currents at room temperature (4.7 nA cm-2 at 1000 V cm-1), allow good room-temperature operation even at high bias voltages (>7000 V cm-1). At low rates (200 counts s-1), the detectors exhibit an energy resolution around 4% FWHM at 59.5 keV (241Am source) up to 2200 V, by using commercial front-end electronics (A250F/NF charge-sensitive preamplifier, Amptek, USA; nominal equivalent noise charge of 100 electrons RMS). At high rates (1 Mcounts s-1), the detectors, coupled to a custom-designed digital pulse processing electronics developed at DiFC of University of Palermo (Italy), show low spectroscopic degradations: energy resolution values of 8% and 9.7% FWHM at 59.5 keV (241Am source) were measured, with throughputs of 0.4% and 60% at 1 Mcounts s-1, respectively. An energy resolution of 7.7% FWHM at 122.1 keV (57Co source) with a throughput of 50% was obtained at 550 kcounts s-1 (energy resolution of 3.2% at low rate). These activities are in the framework of an Italian research project on the development of energy-resolved photon-counting systems for high-flux energy-resolved X-ray imaging.

Measurements with MÖNCH, a 25 μm pixel pitch hybrid pixel detector

MÖNCH is a hybrid silicon pixel detector based on charge integration and with analog readout, featuring a pixel size of 25×25 μm2. The latest working prototype consists of an array of 400×400 identical pixels for a total active area of 1×1 cm2. Its design is optimized for the single photon regime. An exhaustive characterization of this large area prototype has been carried out in the past months, and it confirms an ENC in the order of 35 electrons RMS and a dynamic range of ∼4×12 keV photons in high gain mode, which increases to ∼100×12 keV photons with the lowest gain setting. The low noise levels of MÖNCH make it a suitable candidate for X-ray detection at energies around 1 keV and below. Imaging applications in particular can benefit significantly from the use of MÖNCH: due to its extremely small pixel pitch, the detector intrinsically offers excellent position resolution. Moreover, in low flux conditions, charge sharing between neighboring pixels allows the use of position interpolation algorithms which grant a resolution at the micrometer-level. Its energy reconstruction and imaging capabilities have been tested for the first time at a low energy beamline at PSI, with photon energies between 1.75 keV and 3.5 keV, and results will be shown.

X-ray response of CdZnTe detectors grown by the vertical Bridgman technique: Energy, temperature and high flux effects

Nowadays, CdZnTe (CZT) is one of the key materials for the development of room temperature X-ray and gamma ray detectors and great efforts have been made on both the device and the crystal growth technologies. In this work, we present the results of spectroscopic investigations on new boron oxide encapsulated vertical Bridgman (B-VB) grown CZT detectors, recently developed at IMEM-CNR Parma, Italy. Several detectors, with the same electrode layout (gold electroless contacts) and different thicknesses (1 and 2.5mm), were realized: the cathode is a planar electrode covering the detector surface (4.1×4.1mm2), while the anode is a central electrode (2×2mm2) surrounded by a guard-ring electrode. The detectors are characterized by electron mobility-lifetime product (µeτe) values ranging between 0.6 and 1·10−3cm2/V and by low leakage currents at room temperature and at high bias voltages (38nA/cm2 at 10000V/cm). The spectroscopic response of the detectors to monochromatic X-ray and gamma ray sources (109Cd, 241Am and 57Co), at different temperatures and fluxes (up to 1 Mcps), was measured taking into account the mitigation of the effects of incomplete charge collection, pile-up and high flux radiation induced polarization phenomena. A custom-designed digital readout electronics, developed at DiFC of University of Palermo (Italy), able to perform a fine pulse shape and height analysis even at high fluxes, was used. At low rates (200cps) and at room temperature (T=25°C), the detectors exhibit an energy resolution FWHM around 4% at 59.5keV, for comparison an energy resolution of 3% was measured with Al/CdTe/Pt detectors by using the same electronics (A250F/NF charge sensitive preamplifier, Amptek, USA; nominal ENC of 100 electrons RMS). At high rates (750 kcps), energy resolution values of 7% and 9% were measured, with throughputs of 2% and 60% respectively. No radiation polarization phenomena were observed at room temperature up to 1 Mcps (241Am source, 60keV), while a detector collapse characterizes the samples at T<10°C.Comparison with two traveling heater method (THM) grown CZT detectors (REDLEN, Canada), fabricated with the same electrode layout, is also presented.These activities are in the framework of an Italian research project on the development of energy-resolved photon counting (ERPC) systems for high flux energy-resolved X-ray imaging.

Trimming the threshold dispersion below 10 e-rms in a large area readout IC working in a single photon counting mode

We present a new method of an in-pixel threshold dispersion correction implemented in a prototype readout integrated circuit (IC) operating in a single photon counting mode. The new threshold correction method was implemented in a readout IC of area 9.6× 14.9 mm2 containing 23552 square pixels with the pitch of 75 μm designed and fabricated in CMOS 130 nm technology. Each pixel of the IC consists of a charge sensitive amplifier, a shaper, two discriminators, two 14-bit counters and a low-area trim DACs for threshold correction. The user can either control the range of the trim DAC globally for all the pixels in the integrated circuit or modify the trim DACs characteristics locally in each pixel independently. Using a simulation tool based on the Monte-Carlo methods, we estimated how much we could improve the offset trimming by increasing the number of bits in the trim DACs or implementing additional bits in a pixel to modify the characteristics of the trim DACs. The measurements of our IC prototype show that it is possible to reduce the effective threshold dispersion in large-area single-photon counting chips below 10 electrons rms.

Non-linear responsivity characterisation of a CMOS Active Pixel Sensor for high resolution imaging of the Jovian system

The Jovian system is the subject of study for the Jupiter Icy Moon Explorer (JUICE), an ESA mission which is planned to launch in 2022. The scientific payload is designed for both characterisation of the magnetosphere and radiation environment local to the spacecraft, as well as remote characterisation of Jupiter and its satellites. A key instrument on JUICE is the high resolution and wide angle camera, JANUS, whose main science goals include detailed characterisation and study phases of three of the Galilean satellites, Ganymede, Callisto and Europa, as well as studies of other moons, the ring system, and irregular satellites.The CIS115 is a CMOS Active Pixel Sensor from e2v technologies selected for the JANUS camera. It is fabricated using 0.18 μ m CMOS imaging sensor process, with an imaging area of 2000 × 1504 pixels, each 7 μ m square. A 4T pixel architecture allows for efficient correlated double sampling, improving the readout noise to better than 8 electrons rms, whilst the sensor is operated in a rolling shutter mode, sampling at up to 10 Mpixel/s at each of the four parallel outputs.A primary parameter to characterise for an imaging device is the relationship that converts the sensor's voltage output back to the corresponding number of electrons that were detected in a pixel, known as the Charge to Voltage Factor (CVF). In modern CMOS sensors with small feature sizes, the CVF is known to be non-linear with signal level, therefore a signal-dependent measurement of the CIS115's CVF has been undertaken and is presented here. The CVF is well modelled as a quadratic function leading to a measurement of the maximum charge handling capacity of the CIS115 to be 3.4 × 104 electrons. If the CIS115's response is assumed linear, its CVF is 21.1 electrons per mV (1/47.5 μ V per electron).

Tests With Soft X-rays of an Improved Monolithic SOI Active Pixel Sensor

We have been developing monolithic active pixel sensors with 0.2 μm Silicon-On-Insulator (SOI) CMOS technology, called SOIPIX, for high-speed wide-band X-ray imaging spectroscopy on future astronomical satellites. In this work, we investigate a revised chip (XRPIX1b) for soft X-rays used in frontside illumination. The Al Kα line at 1.5 keV is successfully detected and energy resolution of 188 eV (FWHM) is achieved from a single pixel at this energy. The responsivity is improved to 6 μV/electron and the readout noise is 18 electrons rms. Data from 3 ×3 pixels irradiated with 6.4 keV (Fe Kα) X-rays demonstrates that the circuitry crosstalk between adjacent pixels is less than 0.5%.

Performance of RPCs and diamond detectors using a new very fast low noise preamplifier

The new high energy high luminosity experiments require an improvement in both the counting rate and the space resolution for the detectors. This improvement can be achieved by reducing the charge per count, however this implies a need for a better signal to noise ratio in the signal processing. In this article we will show the performances of diamond detectors and RPCs using a new preamplifier with low noise (500–1000 electrons RMS), fast shaping (about 10 ns) and large input capacitance.

A Low-Noise Dual-Stage a-Si:H Active Pixel Sensor

This paper presents a low-noise and low-current autozeroed (AZ) dual-stage active-pixel-sensor circuit with a noise figure of 830 input-referred rms electrons and compares its performance with the conventional pixel with a figure of 1950 electrons. Through the analysis, we show how the dual stage can increase the photoinduced signal transconductance gain while keeping the relative output-referred noise low by using lower bias currents. From the analysis and verified-via-noise measurements, we report a 55% reduction in the input-referred noise using the optimized readout. The new design performs reset autozeroing, which stabilizes the gain every reset period. Using a subthreshold-mode a-Si:H TFT photodetector, the designed AZ dual stage provided the maximum gain with transient light. The dual stage is also less sensitive to electrical degradation induced by stressing but increases the overall pixel size.

A fast and low noise charge sensitive preamplifier in 90 nm CMOS technology

A fast charge sensitive preamplifier was designed and built in a 90 nm CMOS technology. The work is part of the R&D effort towards the read out of pixel or small strip sensors in next generation HEP experiments. The preamplifier features outstanding noise performance given its wide bandwidth, with a ENC (equivalent noise charge) of about 350 electrons RMS with a detector of 1 pF capacitance. With proper filtering, the ENC drops to less than 200 electrons RMS. Power consumption is 5 mW for one channel, and the closed loop bandwith is about 180 MHz, for a risetime down to 2 ns in the fastest operation mode. Thanks to some freedom left to the user in setting the open loop gain, detectors with larger source capacitance can be read out without significant loss in bandwidth, being the rise time still 5.5 ns for a 5.6 pF detector. The output can drive a 50 Ω terminated transmission line.

TU‐C‐211‐02: Characterizing the Dynamic Range and Noise Performance of a High‐Resolution EMCCD‐Based X‐Ray Detector Having Large Variable Electronic Gain Enabling Use in Both Fluoroscopy and Angiography

Purpose: To quantitatively characterize the dynamic range and noise performance of a new custom‐built, 1k by 1k, 26.4 micron square pixel, high‐resolution, solid‐state EMCCD‐based x‐ray detector. Methods: We performed two sets of experiments: higher‐exposure angiographic imaging with lower gain (&lt; 200), and lower‐exposure fluoroscopic imaging with higher gain (&gt; 200). For each experiment, 150 flat‐field images are acquired over the range of exposures for each multiplication gain. Average signal digital number (DN) versus exposure, and average variance (DN) versus exposure or signal are plotted and linearly fitted to quantitatively characterize the electronic gain, background or dark noise equivalent rms electrons, and instrumentation noise equivalent exposure (INEE), respectively. Results: For the low gain measurements, the noise electron rms value and INEE decreases with increasing gain virtually eliminating the effect of read‐noise, which is the main source of noise for conventional detectors. When the gain is increased for the low exposure measurements, dark noise from dark current and clock induced charge (CIC), which are constant with gain, become dominant and set the detection limit. With the same procedure, an additional experiment is performed to evaluate the dark noise and INEE at high gain with cooling. At room temperature, the dark noise is 1.03 e‐ rms and the INEE is 1.46 microR. Cooling the sensor effectively reduces the noise electrons (0.66 e‐ rms at 200mA pelticooler current and 0.50 e‐ rms at 400mA pelticooler current) and INEE (0.52 microR at 200mA pelticooler current and 0.33 microR at 400mA pelticooler current). Conclusions: The EMCCD‐based x‐ray detector with large variable gain has linear performance over a wide range of exposures with a low noise floor that can be further decreased by moderate cooling. The INEE for this unique detector is substantially less than the 2 to 3 microR of conventional flat panels.Support: NIH Grants R01‐EB008425, R01‐EB002873

Focus on lasers and imaging

Focus on lasers and imaging

Hard x-ray response of pixellated CdZnTe detectors

In recent years, the development of cadmium zinc telluride (CdZnTe) detectors for x-ray and gamma ray spectrometry has grown rapidly. The good room temperature performance and the high spatial resolution of pixellated CdZnTe detectors make them very attractive in space-borne x-ray astronomy, mainly as focal plane detectors for the new generation of hard x-ray focusing telescopes. In this work, we investigated on the spectroscopic performance of two pixellated CdZnTe detectors coupled with a custom low noise and low power readout application specific integrated circuit (ASIC). The detectors (10×10×1 and 10×10×2 mm3 single crystals) have an anode layout based on an array of 256 pixels with a geometric pitch of 0.5 mm. The ASIC, fabricated in 0.8 μm BiCMOS technology, is equipped with eight independent channels (preamplifier and shaper) and characterized by low power consumption (0.5 mW/channel) and low noise (150–500 electrons rms). The spectroscopic results point out the good energy resolution of both detectors at room temperature [5.8% full width at half maximum (FWHM) at 59.5 keV for the 1 mm thick detector; 5.5% FWHM at 59.5 keV for the 2 mm thick detector) and low tailing in the measured spectra, confirming the single charge carrier sensing properties of the CdZnTe detectors equipped with a pixellated anode layout. Temperature measurements show optimum performance of the system (detector and electronics) at T=10 °C and performance degradation at lower temperatures. The detectors and the ASIC were developed by our collaboration as two small focal plane detector prototypes for hard x-ray multilayer telescopes operating in the 20–70 keV energy range.

Integrated Sensors for Charged-Particle Imaging Using Per-Pixel Correlated Double Sampling

Monolithic CMOS cameras for direct imaging in electron microscopy and other radiation imaging applications have been developed and have been used to capture images with high signal to noise and resolution. Based on CMOS Active Pixel Sensor (APS) technology, the arrays use an 8 to 20 mum epitaxial layer that acts as a thicker sensitive region for the liberation and collection of ionization electrons resulting from impinging charged particles. This results in a 100% fill factor and a far larger signal per incident charged particle than a typical CMOS photodiode could provide. The per-pixel CDS scheme discussed in this paper has demonstrated reductions in <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">kT</i> / <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</i> noise by a factor of four, to 11 electrons RMS at room temperature. The CDS scheme requires only one read instead of the two reads plus pre- and post-integration subtraction required by traditional CDS, and is hence faster than alternate schemes. In addition, the test device was used in the observation of Random Telegraph Signal noise (RTS) in small-capacitance pixels under different <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">gs</sub> conditions.

Evaluation of Silicon Detectors With Integrated JFET for Biomedical Applications

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> This paper presents initial results from electrical, spectroscopic and ion beam induced charge (IBIC) characterisation of a novel silicon PIN detector, featuring an on-chip <formula formulatype="inline"><tex Notation="TeX">$n$</tex> </formula>-channel JFET and matched feedback capacitor integrated on its <formula formulatype="inline"><tex Notation="TeX">$p$</tex></formula>-side (frontside). This structure reduces electronic noise by minimising stray capacitance and enables highly efficient optical coupling between the detector back-side and scintillator, providing a fill factor of close to 100%. The detector is specifically designed for use in high resolution gamma cameras, where a pixellated scintillator crystal is directly coupled to an array of silicon photodetectors. The on-chip JFET is matched with the photodiode capacitance and forms the input stage of an external charge sensitive preamplifier (CSA). The integrated monolithic feedback capacitor eliminates the need for an external feedback capacitor in the external electronic readout circuit, improving the system performance by eliminating uncontrolled parasitic capacitances. An optimised noise figure of 152 electrons RMS was obtained with a shaping time of 2 <formula formulatype="inline"> <tex Notation="TeX">$\mu$</tex></formula>s and a total detector capacitance of 2pF. The energy resolution obtained at room temperature (21<formula formulatype="inline"> <tex Notation="TeX">$^{\circ}$</tex></formula>C) at 27 keV (direct interaction of I-125 gamma rays) was 5.09%, measured at full width at half maximum (FWHM). The effectiveness of the guard ring in minimising the detector leakage current and its influence on the total charge collection volume is clearly demonstrated by the IBIC images. </para>

HEXITEC ASIC—a pixellated readout chip for CZT detectors

HEXITEC is a collaborative project with the aim of developing a new range of detectors for high-energy X-ray imaging. High-energy X-ray imaging has major advantages over current lower energy imaging for the life and physical sciences, including improved phase-contrast images on larger, higher density samples and with lower accumulated doses. However, at these energies conventional silicon-based devices cannot be used, hence, the requirement for a new range of high Z-detector materials. Underpinning the HEXITEC programme are the development of a pixellated Cadmium Zinc Telluride (CZT) detectors and a pixellated readout ASIC which will be bump-bonded to the detector. The HEXITEC ASIC is required to have low noise (20 electrons rms) and tolerate detector leakage currents. A prototype 20×20 pixel ASIC has been developed and manufactured on a standard 0.35 μm CMOS process.