Charge Sensitive Preamplifier Research Articles

Temperature dependence of commercial 4H-SiC UV Schottky photodiodes for X-ray detection and spectroscopy

Two commercial-off-the-shelf (COTS) 4H-SiC UV photodiodes have been investigated for their suitability as low-cost high temperature tolerant X-ray detectors. Electrical characterisation of the photodiodes which had different active areas (0.06mm2 and 0.5mm2) is reported over the temperature range 0°C to 140°C together with measurements of the X-ray photocurrents generated when the detectors were illuminated with an 55Fe radioisotope X-ray source. The 0.06mm2 photodiode was also investigated as a photon counting spectroscopic X-ray detector across the temperature range 0°C to 100°C. The depletion widths (at 120V reverse bias) of the two diodes were found to be 2.3µm and 4.5µm, for the 0.06mm2 and 0.5mm2 detectors respectively, at 140°C. Both devices had low leakage currents (<10 pA) at temperatures ≤40°C even at high electric field strengths (500kV/cm for 0.06mm2 diode; 267kV/cm for 0.5mm2 diode). At 140°C and similar field strengths (514kV/cm for 0.06mm2 diode; 269kV/cm for 0.5mm2 diode), the leakage currents of both diodes were <2nA (corresponding to leakage current densities of 2.4µA/cm2 and 0.3µA/cm2 for each diode respectively). The results demonstrated that both devices could function as current mode detectors of soft X-rays at the temperatures <80°C and that when coupled to a low noise charge sensitive preamplifier, the smaller diode functioned as a photon counting spectroscopic X-ray detector at temperatures ≤100°C with modest energy resolution (1.6keV FWHM at 5.9keV at 0°C; 2.6keV FWHM at 5.9keV at 100°C). Due to their temperature tolerance, wide commercial availability, and the radiation hardness of SiC, such detectors are expected to find utility in future low-cost nanosatellite (cubesat) missions and cost-sensitive industrial applications.

Development of cryogenic CMOS Readout ASICs for the Point-Contact HPGe Detectors for Dark Matter Search and Neutrino Experiments

The paper presents the developments of two cryogenic readout ASICs for the point-contact HPGe detectors for dark matter search and neutrino experiments. Extremely low noise readout electronics were demanded and the capability of working at cryogenic temperatures may bring great advantages. The first ASIC was a monolithic CMOS charge sensitive preamplifier with its noise optimized for ∼1 pF input capacitance. The second ASIC was a waveform recorder based on switched capacitor array. These two ASICs were fabricated in CMOS 350 nm and 180 nm processes respectively. The prototype chips were tested and showed promising results. Both ASICs worked well at low temperature. The preamplifier had achieved ENC of 10.3 electrons with 0.7 pF input capacitance and the SCA chip could run at 9 bit effective resolution and 25 MSPS sampling rate.

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.

Prototype of IGZO-TFT preamplifier and analog counter for pixel detector

IGZO-TFT (Indium Galium Zinc Oxide-Thin Film Transistor) is a promising technology for controlling large display areas and large area sensors because of its very low leakage current in the off state and relatively low cost. IGZO has been used as a switching gate for a large area flat-panel detector. The photon counting capability for X-ray medical imaging has been investigated and expected for low-dose exposure and material determination. Here the design and fabrication of a charge sensitive preamplifier and analog counter using IGZO-TFT processes and its performance are reported for the first time to be used for radiation photon counting applications.

Synchrotron beam test of a photon counting pixel prototype based on Double-SOI technology

The overall noise performances and first synchrotron beam measurement results of CPIXETEG3b, the first counting type Silicon-On-Insulator (SOI) pixel sensor prototype without crosstalk issue, are reported. The prototype includes a 64 × 64 pixel matrix with 50 μm pitch size. Each pixel consists of an N-in-P charge collection diode, a charge sensitive preamplifier, a shaper, a discriminator with thresholds adjustable by an in-pixel 4-bit DAC, and a 6-bit counter. The study was performed using the beam line 14A at KEK Photon Factory (KEK-PF) . The homogeneous response of the prototype, including charging-sharing effects between pixels were studied. 16 keV and 8 keV monochromatic small size (∼ 10 μm diameter) X-ray beams were used for the charge sharing study, and a flat-field was added for homogenous response investigation. The overall detector homogeneity and the influence of basic detector parameters on charge sharing between pixels has been investigated.

Research and development of a high-performance differential-hybrid charge sensitive preamplifier

A differential-hybrid charge sensitive preamplifier (CSP) was designed by taking a monolithic dual N-Channel Junction Field-effect Transistor (JFET) and a high-speed, low-noise, operational amplifier as the core parts. Input-stage of the circuit employs low-noise differential dual JFET, which ensures high input impedance and low noise. The differential dual transistor makes the quiescent point of the first-stage differential output stable, which is convenient for connecting with the post stage high-speed operational amplifier. Broadband could be amplified by connecting to the double differential dual transistors through the folded cascode-bootstrap. The amplifying circuit which replaces the interstage and post stage discrete components of a traditional CSP with integrated operational amplifier is simpler and more reliable. It simplifies the design of the quiescent point, gives full play to advantages of releasing large open-loop gain, and improves charge-voltage conversion gain stability. Particularly, the charge-voltage conversion gain is larger under a smaller feedback capacitor, thus enabling to gain better signal-noise ratio. The designed CSP was tested, reporting 3.3×1013 V/C charge sensitivity, about 90ns rise time of signals, 35:1 signal-noise ratio to gamma-rays of 137Cs (662keV) and a 0.023 fC/pF noise slope. Gamma-rays of 241Am (59.5keV) were measured by the BPX66 detector and the designed CSP under room temperature, providing 1.97% energy resolution.

New calibration circuitry and concept for AGIPD

AGIPD (adaptive gain integrating pixel detector) is a detector system developed for the European XFEL (XFEL.EU), which is currently being constructed in Hamburg, Germany. The XFEL.EU will operate with bunch trains at a repetition rate of 10 Hz. Each train consists of 2700 bunches with a temporal separation of 220 ns corresponding to a rate of 4.5 MHz. Each photon pulse has a duration of < 100 fs (rms) and contains up to 1012 photons in an energy range between 0.25 and 25 keV . In order to cope with the large dynamic range, the first stage of each bump-bonded AGIPD ASIC is a charge sensitive preamplifier with three different gain settings that are dynamically switched during the charge integration. Dynamic gain switching allows single photon resolution in the high gain stage and can cover a dynamic range of 104 × 12.4 keV photons in the low gain stage. The burst structure of the bunch trains forces to have an intermediate in-pixel storage of the signals. The full scale chip has 352 in-pixel storage cells inside the pixel area of 200 × 200 μm2. This contribution will report on the measurements done with the new calibration circuitry of the AGIPD1.1 chip (without sensor). These results will be compared with the old version of the chip (AGIPD1.0). A new calibration method (that is not AGIPD specific) will also be shown.

Al0.2Ga0.8As X-ray photodiodes for X-ray spectroscopy

Three custom-made Al0.2Ga0.8As p-i-n mesa X-ray photodiodes (200µm diameter, 3µm i layer) were electrically characterised and investigated for their response to illumination with soft X-rays from an 55Fe radioisotope X-ray source (Mn Kα = 5.9keV; Mn Kβ = 6.49keV). The AlGaAs photodiodes were shown to be suitable for photon counting X-ray spectroscopy at room temperature. When coupled to a custom-made low-noise charge-sensitive preamplifier, a mean energy resolution (as quantified by the full width at half maximum of the 5.9keV photopeak) of 1.24keV was measured at room temperature. Parameters such as the depletion width (1.92µm at 10V), charge trapping noise (61.7 e−rms ENC at 5V, negligible at 10V) and the electronic noise components (known dielectric noise (63.4 e− rms), series white noise (27.7 e−rms), parallel white noise (9.5 e−rms) and 1/f series noise (2.2 e−rms) at 10V reverse bias) affecting the achieved energy resolution were computed. The estimated charge trapping noise and mean energy resolution were compared to similar materials (e.g. Al0.8Ga0.2As) previously reported, and discussed. These results are the first demonstration of photon counting X-ray spectroscopy with Al0.2Ga0.8As reported to date.

New analog electronics for the new challenges in the synthesis of superheavy elements

A new series of experiments aimed at the synthesis and study of decay properties of the most neutron-deficient isotopes of element Fl (Z = 114) and of the heaviest isotopes of 118 element is planned at the DGFRS (FLNR JINR). An appropriate registering system is to be implemented to transfer spectrometric data from double-sided silicon strip detector (DSSD). New analog modules were designed that allow to simplify existing multi-channel measurement system and to improve the real-time method of “active correlations” in search for the rare events of SHE formation and decay. The main features of the new modules the 16-channel charge-sensitive preamplifier, the 16-channel analog multiplexer and the 1.25 MSPS 12-bit Parallel ADC are presented.

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.

Development of a dedicated front-end electronics for straw tube trackers in the P̄ANDA experiment

The design and tests of front-end electronics for straw tube trackers in the P̄ANDA experiment at FAIR are presented. The challenges for the front-end electronics, comprising operation at high counting rate up to 1 MHz per straw tube, are discussed and the proposed architecture comprising a switched gain charge sensitive preamplifier (CSP), a pole-zero cancellation circuit (PZC), a second order variable peaking time shaper, a trimming ion tail cancellation circuit, and a baseline holder (BLH), is described. The front-end provides an analogue output and a discriminator with LVDS differential driver for the Time-of-Arrival (ToA) and Time-over-Threshold (ToT) measurements. A prototype readout ASIC featuring four channels was fabricated in 0.35 μm CMOS technology consuming 15.5 mW (analog part) and 12 mW (LVDS) per channel. The results of measurements of peaking time (25–67 ns), gain, noise (ENC 800–2500 el. for various gains), time walk and jitter are presented as well as the first results obtained with prototype straw tubes connected.

The experimental set-up of the RIB in-flight facility EXOTIC

We describe the experimental set-up of the Radioactive Ion Beam (RIB) in-flight facility EXOTIC consisting of: (a) two position-sensitive Parallel Plate Avalanche Counters (PPACs), dedicated to the event-by-event tracking of the produced RIBs and to time of flight measurements and (b) the new high-granularity compact telescope array EXPADES (EXotic PArticle DEtection System), designed for nuclear physics and nuclear astrophysics experiments employing low-energy light RIBs. EXPADES consists of eight ΔE–Eres telescopes arranged in a cylindrical configuration around the target. Each telescope is made up of two Double Sided Silicon Strip Detectors (DSSSDs) with a thickness of 40/60μm and 300μm for the ΔE and Eres layer, respectively. Additionally, eight ionization chambers were constructed to be used as an alternative ΔE stage or, in conjunction with the entire DSSSD array, to build up more complex triple telescopes. New low-noise multi-channel charge-sensitive preamplifiers and spectroscopy amplifiers, associated with constant fraction discriminators, peak-and-hold and Time to Amplitude Converter circuits were developed for the electronic readout of the ΔE stage. Application Specific Integrated Circuit-based electronics was employed for the treatment of the Eres signals. An 8-channel, 12-bit multi-sampling 50MHz Analog to Digital Converter, a Trigger Supervisor Board for handling the trigger signals of the whole experimental set-up and an ad hoc data acquisition system were also developed. The performance of the PPACs, EXPADES and of the associated electronics was obtained offline with standard α calibration sources and in-beam by measuring the scattering process for the systems 17O+58Ni and 17O+208Pb at incident energies around their respective Coulomb barriers and, successively, during the first experimental runs with the RIBs of the EXOTIC facility.

Soft X-ray detection and photon counting spectroscopy with commercial 4H-SiC Schottky photodiodes

The results of electrical characterisation and X-ray detection measurements of two different active area (0.06mm2 and 0.5mm2) commercial 4H-SiC Schottky photodiodes at room temperature are reported. The devices exhibited low dark currents (less than 10pA) even at a high electric field strengths (403kV/cm for 0.06mm2 diodes; 227kV/cm for 0.5mm2 diodes). The results of the X-ray measurements indicate that the diodes can be used as photon counting spectroscopic X-ray detectors with modest energy resolutions: FWHM at 5.9keV of 1.8keV and 3.3keV, for the 0.06mm2 and 0.5mm2 devices, respectively. Noise analysis of the photodiodes coupled to a custom low noise charge sensitive preamplifier is also presented.

A High-Gain 1.75-GHz Dual-Inductor Transimpedance Amplifier With Gate Noise Suppression for Fast Radiation Detection

High-speed pulse-shape analysis can allow one to extract the physical parameters that govern radiation interaction. This brief presents a transimpedance preamplifier that can replace conventional configurations that contain a charge-sensitive preamplifier and shaping amplifier chain, particularly for high-speed radiation measurement systems. A transimpedance amplifier is a primary circuit of the preamplifier design based on a feedback structure with cascade inverting amplifiers and a feedback resistor, but it incorporates a bandwidth and gain enhancement technique that utilizes a series $LC$ circuit at the input of the amplifier. This configuration is designed to reduce the size, power consumption, and complexity of the front-end circuitry traditionally used in radiation measurements while enhancing pulse-shape analyses by preserving the temporal information of the carriers following radiation impingement. The preamplifier implemented in the 180-nm CMOS process exhibits an 83- $\mbox{dB}\Omega$ transimpedance gain and a 1.75-GHz bandwidth while consuming 48.6 mW using a 1.8-V supply.

A low cost X-ray imaging device based on BPW-34 Si-PIN photodiode

A low cost X-ray imaging device based on BPW-34 silicon PIN photodiode was designed and produced. X-rays were produced from a CEI OX/70-P dental tube using a custom made ±30kV power supply. A charge sensitive preamplifier and a shaping amplifier were built for the amplification of small signals produced by photons in the depletion layer of Si-PIN photodiode. A two dimensional position control unit was used for moving the detector in small steps to measure the intensity of X-rays absorbed in the object to be imaged. An Aessent AES220B FPGA module was used for transferring the image data to a computer via USB. Images of various samples were obtained with acceptable image quality despite of the low cost of the device.

Low-Noise Preamplifier Design Considerations for Large Area High Capacitance Solid-State Neutron Detectors

In this paper, the design of a low noise charge sensitive preamplifier, suitable for high capacitance solid-state neutron detector arrays, is described. Noise considerations related to arraying multiple detectors in either series or parallel are also presented. Using the designed preamplifier, an energy resolution of 12 keV FWHM in Si is achieved with 1 nF equivalent detector capacitance and $10~\mu\hbox{S} $ shaping time. Additionally, a novel preamplifier topology, which utilizes a capacitance canceling input stage, is presented. Detailed analysis of the capacitance cancelling stage is discussed with special consideration given to its use with a charge sensitive preamplifier. Up to a 15% decrease in noise is demonstrated using the capacitance cancelling technique.

X-Ray Silicon Drift Detector–CMOS Front-End System with High Energy Resolution at Room Temperature

We present a spectroscopic system constituted by a Silicon Drift Detector (SDD) coupled to a CMOS charge sensitive preamplifier, named SIRIO, specifically designed to reach ultimate low noise levels. The SDD, with an active area of 13 mm , has been manufactured by optimizing the production processes in order to reduce the anode current, successfully reaching current densities between 17 pA/cm and 25 pA/cm at 20 for drift fields ranging from 100 V/cm to 500 V/cm. The preamplifier shows minimum intrinsic noise levels of 1.27 and 1.0 electrons r.m.s. at 20 and 30 , respectively. At room temperature ( ) the 5.9 keV and the pulser lines have 136 eV and 64 eV FWHM, respectively, corresponding to an equivalent noise charge of 7.4 electrons r.m.s.; the noise threshold is at 165 eV. The energy resolution, as measured on the pulser line, ranges from 82 eV FWHM (9.4 electrons r.m.s.) at 30C down to 29 eV FWHM (3.3 electrons r.m.s.) at 30C .

65 nm CMOS analog front-end for pixel detectors at the HL-LHC

This work is concerned with the design and the experimental characterization of analog front-end electronics conceived for experiments with unprecedented particle rates and radiation levels at future high-energy physics colliders. A prototype chip integrating different test structures has been submitted in the framework of the CHIPIX65 project. These structures are standalone channels for the readout of hybrid pixels, featuring a charge sensitive preamplifier as the first stage of the readout chain, a high-speed comparator and a circuit for fine threshold tuning. The paper thoroughly discusses the results, mainly focused on the charge sensitive amplifier, coming from the characterization of the submitted test structures.

Front end ASIC for AGIPD, a high dynamic range fast detector for the European XFEL

The Adaptive Gain Integrating Pixel Detector (AGIPD) is a hybrid pixel X-ray detector for the European-XFEL. One of the detector's important parts is the radiation tolerant front end ASIC fulfilling the European-XFEL requirements: high dynamic range—from sensitivity to single 12.5keV-photons up to 104 photons. It is implemented using the dynamic gain switching technique with three possible gains of the charge sensitive preamplifier. Each pixel can store up to 352 images in memory operated in random-access mode at ⩾4.5 MHz frame rate. An external vetoing may be applied to overwrite unwanted frames.

Ultra-low noise mechanically cooled germanium detector

Low capacitance, large volume, high purity germanium (HPGe) radiation detectors have been successfully employed in low-background physics experiments. However, some physical processes may not be detectable with existing detectors whose energy thresholds are limited by electronic noise. In this paper, methods are presented which can lower the electronic noise of these detectors. Through ultra-low vibration mechanical cooling and wire bonding of a CMOS charge sensitive preamplifier to a sub-pF p-type point contact HPGe detector, we demonstrate electronic noise levels below 40eV-FWHM.