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The XL-Calibur balloon-borne hard X-ray polarimetry mission comprises a Compton-scattering polarimeter placed at the focal point of an X-ray mirror. The polarimeter is housed within a BGO anticoincidence shield, which is needed to mitigate the considerable background radiation present at the observation altitude of ~40 km. This paper details the design, construction and testing of the anticoincidence shield, as well as the performance measured during the week-long maiden flight from Esrange Space Centre to the Canadian Northwest Territories in July 2022. The in-flight performance of the shield followed design expectations, with a veto threshold, Submitted to Nuclear Instruments and Methods A

X-Calibur is a balloon-borne telescope that measures the polarization of high-energy X-rays in the 15--50keV energy range. The instrument makes use of the fact that X-rays scatter preferentially perpendicular to the polarization direction. A beryllium scattering element surrounded by pixellated CZT detectors is located at the focal point of the InFOC{\mu}S hard X-ray mirror. The instrument was launched for a long-duration balloon (LDB) flight from McMurdo (Antarctica) on December 29, 2018, and obtained the first constraints of the hard X-ray polarization of an accretion-powered pulsar. Here, we describe the characterization and calibration of the instrument on the ground and its performance during the flight, as well as simulations of particle backgrounds and a comparison to measured rates. The pointing system and polarimeter achieved the excellent projected performance. The energy detection threshold for the anticoincidence system was found to be higher than expected and it exhibited unanticipated dead time. Both issues will be remedied for future flights. Overall, the mission performance was nominal, and results will inform the design of the follow-up mission XL-Calibur, which is scheduled to be launched in summer 2022., Comment: 19 pages, 31 figures, submitted to Astropart. Phys

XL-Calibur is a hard X-ray (15-80 keV) polarimetry mission operating from a stabilised balloon-borne platform in the stratosphere. It builds on heritage from the X-Calibur mission, which observed the accreting neutron star GX 301-2 from Antarctica, between December 29th 2018 and January 1st 2019. The XL-Calibur design incorporates an X-ray mirror, which focusses X-rays onto a polarimeter comprising a beryllium rod surrounded by Cadmium Zinc Telluride (CZT) detectors. The polarimeter is housed in an anticoincidence shield to mitigate background from particles present in the stratosphere. The mirror and polarimeter-shield assembly are mounted at opposite ends of a 12 m long lightweight truss, which is pointed with arcsecond precision by WASP - the Wallops Arc Second Pointer. The XL-Calibur mission will achieve a substantially improved sensitivity over X-Calibur by using a larger effective area X-ray mirror, reducing background through thinner CZT detectors, and improved anticoincidence shielding. When observing a 1 Crab source for $t_{\rm day}$ days, the Minimum Detectable Polarisation (at 99% confidence level) is $\sim$2$\%\cdot t_{\rm day}^{-1/2}$. The energy resolution at 40 keV is $\sim$5.9 keV. The aim of this paper is to describe the design and performance of the XL-Calibur mission, as well as the foreseen science programme., Comment: 19 pages, 17 figures. Accepted for publication in Astroparticle Physics

The accretion-powered X-ray pulsar GX 301-2 was observed with the balloon-borne X-Calibur hard X-ray polarimeter during late December 2018, with contiguous observations by the NICER X-ray telescope, the Swift X-ray Telescope and Burst Alert Telescope, and the Fermi Gamma-ray Burst Monitor spanning several months. The observations detected the pulsar in a rare apastron flaring state coinciding with a significant spin-up of the pulsar discovered with the Fermi GBM. The X-Calibur, NICER, and Swift observations reveal a pulse profile strongly dominated by one main peak, and the NICER and Swift data show strong variation of the profile from pulse to pulse. The X-Calibur observations constrain for the first time the linear polarization of the 15-35 keV emission from a highly magnetized accreting neutron star, indicating a polarization degree of (27+38-27)% (90% confidence limit) averaged over all pulse phases. We discuss the spin-up and the X-ray spectral and polarimetric results in the context of theoretical predictions. We conclude with a discussion of the scientific potential of future observations of highly magnetized neutron stars with the more sensitive follow-up mission XL-Calibur., Comment: Accepted for publication in the Astrophysical Journal. 20 pages, 19 figures, 4 tables

Large-area arrays of position-sensitive virtual Frisch-grid CdZnTe (CZT) detectors with enhanced energy resolution and high efficiency have been proposed for spectroscopy and imaging of gamma-ray sources. Here, we present the design and test results of a linear array of such detectors optimized for use in handheld instruments. There are several application areas for such detectors including uranium enrichment measurements, storage monitoring, dosimetry and other nuclear safeguards related tasks. The array configuration provides a large area with minimum number of readout channels, which potentially allows the developers to avoid using ASIC-based readout electronics by substituting it with hybrid preamplifiers followed by digitizers. The array prototype consists of 6 5 × 7 × 25 mm3 CZT detectors side-oriented with respect to the source to achieve the maximum area. Each detector is furnished with 5 mm-wide charge-sensing pads placed near the anode. As an option, the pads can be grouped together to reduce the number of readout channels. The same can be done with the cathodes. The pads signals are converted into X–Y coordinates and combined with the cathode signals (for the Z coordinates) to give 3D positional information of each interaction point. This information is used to correct the response non-uniformity caused by material inhomogeneity, which allows the developers to use standard grade (unselected) CZT crystals, while retaining high spectroscopic performance.

We evaluated the sub-pixel position resolution achievable in large-volume CdZnTe pixelated detectors with conventional pixel patterns and for several different pixel sizes: 2.8 mm, 1.72 mm, 1.4 mm and 0.8 mm. Achieving position resolution below the physical dimensions of pixels (sub-pixel resolution) is a practical path for making high-granularity position-sensitive detectors, μ m, using a limited number of pixels dictated by the mechanical constraints and multi-channel readout electronics. High position sensitivity is important for improving the imaging capability of CZT gamma cameras. It also allows for making more accurate corrections of response non-uniformities caused by crystal defects , thus enabling use of standard-grade (unselected) and less expensive CZT crystals for producing large-volume position-sensitive CZT detectors feasible for many practical applications. We analyzed the digitized charge signals from a representative 9 pixels and the cathode, generated using a pulsed-laser light beam focused down to 10 μ m (650 nm) to scan over a selected 3 × 3 pixel area. We applied our digital pulse processing technique to the time-correlated signals captured from adjacent pixels to achieve and evaluate the capability for sub-pixel position resolution. As an example, we also demonstrated an application of 3D corrections to improve the energy resolution and positional information of the events for the tested detectors.

Position-sensitive virtual Frisch-grid (VFG) CdZnTe (CZT) detectors offer a unique capability for correcting the response nonuniformities caused by crystal defects. This allowed us to achieve high energy resolution, while using typical-grade commercial CZT crystals with relaxed requirements to their quality, thus reducing the overall cost of detectors. Another advantage of the VFG detectors is that they can be integrated into arrays and used in small compact hand-held instruments or large-area gamma cameras that will enhance detection capability for many practical applications, including nonproliferation, medical imaging, and gamma-ray astronomy. Here, we present the results from testing small array prototypes coupled with front-end application-specified integrated circuit. Each detector in the array is furnished with 5-mm-wide charge-sensing pads placed near the anode. The pads signals are converted into XY coordinates, which combined with the cathode signals (for Z coordinates) provide 3-D position information of all interaction points. The basic array consists of a number of detectors grouped into $2\times 2$ subarrays, each having a common cathode made by connecting together the cathodes of the individual detectors. These features can significantly improve the performance of detectors while using typical-grade low-cost CZT crystals to reduce the overall cost of the proposed instrument.

We evaluated the X-Y position resolution achievable in 3D pixelated detectors by processing the signal waveforms readout from neighboring pixels. In these measurements we used a focused light beam, down to 10 μ m, generated by a ∼1 mW pulsed laser (650 nm) to carry out raster scans over selected 3 × 3 pixel areas, while recording the charge signals from the 9 pixels and the cathode using two synchronized digital oscilloscopes.

An updated overview of recent results on Heavy-Ion induced reactions of interest for neutrinoless double beta decay is reported in the framework of the NUMEN project. The NUMEN idea is to study heavy-ion induced Double Charge Exchange (DCE) reactions with the aim to get information on the nuclear matrix elements for neutrinoless double beta (0νββ) decay. Moreover, to infer the neutrino average masses from the possible measurement of the half- life of 0νββ decay, the knowledge of the nuclear matrix elements is a crucial aspect. Uma visão geral atualizada dos resultados recentes sobre reações induzidas por íons pesados ​​de interesse para o decaimento beta duplo sem neutrinos é relatada na estrutura do projeto NUMEN. A ideia do NUMEN é estudar reações de Double Charge Exchange (DCE) induzidas por íons pesados ​​com o objetivo de obter informações sobre os elementos da matriz nuclear para o decaimento beta duplo sem neutrinos (0νββ). Além disso, para inferir as massas médias dos neutrinos a partir da possível medição da meia-vida do decaimento 0νββ, o conhecimento dos elementos da matriz nuclear é um aspecto crucial. 1308 012002

Liquid argon time projection chamber technology is an attractive choice for large neutrino detectors, as it provides a high-resolution active target and it is expected to be scalable to very large masses. Consequently, it has been chosen as the technology for the first module of the DUNE far detector. However, the fiducial mass required for "far detectors" of the next generation of neutrino oscillation experiments far exceeds what has been demonstrated so far. Scaling to this larger mass, as well as the requirement for underground construction places a number of additional constraints on the design. A prototype 35-ton cryostat was built at Fermi National Acccelerator Laboratory to test the functionality of the components foreseen to be used in a very large far detector. The Phase I run, completed in early 2014, demonstrated that liquid argon could be maintained at sufficient purity in a membrane cryostat. A time projection chamber was installed for the Phase II run, which collected data in February and March of 2016. The Phase II run was a test of the modular anode plane assemblies with wrapped wires, cold readout electronics, and integrated photon detection systems. While the details of the design do not match exactly those chosen for the DUNE far detector, the 35-ton TPC prototype is a demonstration of the functionality of the basic components. Measurements are performed using the Phase II data to extract signal and noise characteristics and to align the detector components. A measurement of the electron lifetime is presented, and a novel technique for measuring a track's position based on pulse properties is described., Comment: 28 pages, 12 figures, accepted by JINST

Following our successful demonstration of the position-sensitive virtual Frisch-grid detectors, we investigated the feasibility of using high-granularity position sensing to correct response non-uniformities caused by the crystal defects in CdZnTe (CZT) pixelated detectors. The development of high-granularity detectors able to correct response non-uniformities on a scale comparable to the size of electron clouds opens the opportunity of using unselected off-the-shelf CZT material, whilst still assuring high spectral resolution for the majority of the detectors fabricated from an ingot. Here, we present the results from testing 3D position-sensitive 15×15×10 mm 3 pixelated detectors, fabricated with conventional pixel patterns with progressively smaller pixel sizes: 1.4, 0.8, and 0.5 mm. We employed the readout system based on the H3D front-end multi-channel ASIC developed by BNL's Instrumentation Division in collaboration with the University of Michigan. We use the sharing of electron clouds among several adjacent pixels to measure locations of interaction points with sub-pixel resolution. By using the detectors with small-pixel sizes and a high probability of the charge-sharing events, we were able to improve their spectral resolutions in comparison to the baseline levels, measured for the 1.4-mm pixel size detectors with small fractions of charge-sharing events. These results demonstrate that further enhancement of the performance of CZT pixelated detectors and reduction of costs are possible by using high spatial-resolution position information of interaction points to correct the small-scale response non-uniformities caused by crystal defects present in most devices.

CdZnTe (CZT) crystals with thicknesses up to 20 mm and diameters up to 75 mm have become available from Redlen Technologies, Inc. for making large-volume gamma-ray detectors. The modified growth and optimized annealing conditions allowed Redlen to minimize the dark current and improve the uniformity of CZT crystals. Two detector designs, pixelated (H3D) and position-sensitive virtual Frisch-grid (VFG), have greatly benefitted from the availability of such big crystals. Encouraging results from testing of 40 × 40 × 15 mm 3 pixelated detectors were recently reported by the University of Michigan. Here, we evaluated the spectroscopic properties of 8 × 8 × 32 and 10 × 10 × 32 mm 3 crystals configured as position-sensitive VFG detectors. Both digitized waveforms and an analog ASIC were used to read and process the signals from the detectors and test their spectral- and spatial-resolution. The VFG design provides the flexibility to scale-up the dimensions of the detectors for the desired efficiency, while the position information allows for correcting the detectors’ response non-uniformity caused by crystal defects and devices geometry, thereby reducing the instrument cost and making them more feasible for emerging applications in gamma-ray astronomy, nonproliferation, portal screening and nuclear safeguards, where large detector arrays are often required.

The New Small Wheel Upgrade of the ATLAS experiment at CERN, planned to take place at 2020, requires a new generation of front-end electronics that will support its data acquisition requirements. The VMM Application-Specific Integrated Circuit has been in development for the last seven years to serve as the foundation of the New Small Wheel’s readout scheme. It has gone through three major revisions and a minor one, the latter being the production version. To facilitate the testing and readout of the VMM, as well as to study its detector performance, a complete readout system has been developed. It consists of flexible Field-Programmable Gate Array logic with extensive functionality, and an efficient software framework providing the user interface. This system, referred to as the ”The VMM Readout System”, has been used in test-beam campaigns at CERN, as well as in bench calibration and testing measurement scenarios for the past several years, supporting all readout modes and features of the VMM.

Arrays of position-sensitive virtual Frisch-grid CdZnTe (CZT) detectors offer an economical approach to making high efficiency and high energy resolution gamma cameras for spectroscopy and imaging of radioactive sources. There are many application areas for such instruments including gamma-rays astronomy , medical and industrial imaging, nonproliferation and nuclear safeguards . Here we present the test results from a 4 × 4 array module coupled to the front-end ASIC. The array houses 16 detectors made of 6 × 6 × 20 mm3 CZT crystals. Each crystal is encapsulated inside an ultrathin polyester shell and furnished with four 5-mm-wide charge-sensing pads placed near the anode on each side of the detector. The pad’s signals are used to measure X–Y coordinates while the cathode signals give the interaction depths ( Z coordinates). Combined together the signals provide 3D position information of the interaction points which can be used to correct the detector response non-uniformity. This allows developers to use standard grade (unselected) CZT crystals while retaining high spectroscopic performance comparable with that of the H3D pixelated detectors. The array’s design provides flexibility to replace individual detectors and extend their sizes, potentially increasing upwards of 4 cm in height. We started development of position-sensitive VFG detectors several years ago and today this technology has reached a high-maturity level and is ready to use in practical applications.

The characteristics of a recently developed front-end application specific integrated circuit (ASIC) designed for high-purity germanium (HPGe) strip detectors are detailed. The ASIC contains 32 channels, and can instrument either cathode or anode signals from the HPGe detector. The channels provide low-noise charge amplification, four shaping times, four gain ranges, trimmable discrimination for each channel, time to analog output, and peak detectors with analog memory. The channels process events in parallel, and the ASIC emits a logical-OR of the internal discriminators for external control. Each channel contains a time-to-analog circuit to allow the depth of interaction in a detector to be determined. The ASIC has a small noise slope, allowing it to maintain germanium energy resolution at the large, 30 pF, input capacitance of a germanium strip detector connected through the cryostat by a kapton flex cable. The ASIC sparsifies the triggered channels for low deadtime readout. Each channel dissipates 6.2 mW and covers an energy range up to 4 MeV in HPGe. Measurements demonstrate an equivalent noise charge (ENC) of 260 electrons at an input capacitance of 32.5 pF with a slope of 6.4 electrons/pF for a peaking time of 2 μ s .

International audience; NUMEN aims at accessing experimentally driven information on Nuclear Matrix Elements (NME) involved in the half-life of the neutrinoless double beta decay (0νββ), by high-accuracy measurements of the cross sections of Heavy Ion (HI) induced Double Charge Exchange (DCE) reactions. First evidence about the possibility to get quantitative information about NME from experiments is found for the (^18O,^18Ne) and (^20Ne,^20O) reactions. Moreover, to infer the neutrino average masses from the possible measurement of the half-life of 0νββ decay, the knowledge of the NME is a crucial aspect. The key tools for this project are the high resolution Superconducting Cyclotron beams and the MAGNEX magnetic spectrometer at INFN Laboratori Nazionali del Sud in Catania (Italy). The measured cross sections are extremely low, limiting the present exploration to few selected isotopes of interest in the context of typically low-yield experimental runs. A major upgrade of the LNS facility is foreseen in order to increase the experimental yield of at least two orders of magnitude, thus making feasible a systematic study of all the cases of interest.

International audience; The article describes the main achievements of the NUMEN project together with an updated and detailed overview of the related R&D activities and theoretical developments. NUMEN proposes an innovative technique to access the nuclear matrix elements entering the expression of the lifetime of the double beta decay by cross section measurements of heavy-ion induced Double Charge Exchange (DCE) reactions. Despite the fact that the two processes, namely neutrinoless double beta decay and DCE reactions, are triggered by the weak and strong interaction respectively, important analogies are suggested. The basic point is the coincidence of the initial and final state many-body wave functions in the two types of processes and the formal similarity of the transition operators. First experimental results obtained at the INFN-LNS laboratory for the$^{40}$Ca($^{18}$O,$^{18}$Ne)$^{40}$Ar reaction at 270MeV give an encouraging indication on the capability of the proposed technique to access relevant quantitative information. The main experimental tools for this project are the K800 Superconducting Cyclotron and MAGNEX spectrometer. The former is used for the acceleration of the required high resolution and low emittance heavy-ion beams and the latter is the large acceptance magnetic spectrometer for the detection of the ejectiles. The use of the high-order trajectory reconstruction technique, implemented in MAGNEX, allows to reach the experimental resolution and sensitivity required for the accurate measurement of the DCE cross sections at forward angles. However, the tiny values of such cross sections and the resolution requirements demand beam intensities much larger than those manageable with the present facility. The on-going upgrade of the INFN-LNS facilities in this perspective is part of the NUMEN project and will be discussed in the article.

Neutrinoless double beta decay (0 nu beta beta) is considered the best potential resource to access the absolute neutrino mass scale. Moreover, if observed, it will signal that neutrinos are their own anti-particles (Majorana particles). Presently, this physics case is one of the most important research “beyond Standard Model” and might guide the way towards a Grand Unified Theory of fundamental interactions. Since the 0 nu beta beta decay process involves nuclei, its analysis necessarily implies nuclear structure issues. In the NURE project, supported by a Starting Grant of the European Research Council (ERC), nuclear reactions of double charge-exchange (DCE) are used as a tool to extract information on the 0 nu beta beta Nuclear Matrix Elements. In DCE reactions and beta beta decay indeed the initial and final nuclear states are the same and the transition operators have similar structure. Thus the measurement of the DCE absolute cross-sections can give crucial information on beta beta matrix elements. In a wider view, the NUMEN international collaboration plans a major upgrade of the INFN-LNS facilities in the next years in order to increase the experimental production of nuclei of at least two orders of magnitude, thus making feasible a systematic study of all the cases of interest as candidates for 0 nu beta beta.

The design of the front-end electronics for the new tracker of the MAGNEX Focal Plane Detector (FPD) for the NUMEN project is presented. The front-end is based on the VMM chip, developed for ATLAS experiment at CERN. The architecture of the front-end (FE) electronics is designed to be modular and scalable to the final detector. The segmented anode board is designed in order to take advantage of the unique performances of the VMM chip, allowing a digital reconstruction of the track at high event rate. This anode board is connected to front-end by mean of Micro Coax Cable Assembly and does not make use of vacuum connectors. The front-end boards will be placed in air, facilitating in this way the heat dissipation and the connection to the read-out (RO) electronics. An innovative anode read-out strategy allows the reduction of the total number of channels to about 1400 and the measurement of the track at different depth in the detector with 750 µm spatial resolution.

Synchrotron radiation news 31(6), 21 - 27 (2018). doi:10.1080/08940886.2018.1528430, Published by Taylor & Francis, Philadelphia, Pa.

The longer electron lifetime of today’s CdZnTe (CZT) crystals allows for free carriers to travel longer distances in the crystals, which means that, in principle, thicker devices could be fabricated. These thicker CZT devices would offer greater detection efficiency for high-energy gamma-ray detectors. However, up to now, the thicknesses and sizes of actual detectors have still been limited by the nonuniform detector response, and the biggest devices reported in the literature are ${(20\times 20\times 15)}\hbox{-mm}^3$ pixelated detectors with a drift distance of 15 mm. Although thicker and bigger single crystals are becoming available today, the high requirements on their crystal quality drastically reduce their acceptance yield and increase their cost. Fortunately, in many cases, the inhomogeneity in response can be corrected by segmenting the active volumes of the detectors and correcting the responses generated from each of the voxels. Such high-granularity position-sensitive detectors open up the opportunity for using thicker and less-expensive CZT crystals. The goal of this work is to demonstrate that today’s commercial high electron mobility-lifetime CZT material is suitable for a new class of detectors with 20-25-mm drift distances and even larger in the near future, provided that the detectors’ response nonuniformities can be corrected on a scale comparable to or larger than the sizes of the electron clouds, which is $\sim 100~\mu\hbox{m}$ .

International audience; This paper describes the development of a common front-end test stand for the analog ASICs, which are part of the effort to develop the front-end electronics for the ATLAS LAr calorimeter HL-LHC (High Luminosity LHC) upgrade. The common test stand consists of the front-end test board, toy calorimeters, ASIC mezzanine boards and the DAQ system. The front-end test board is the bridge between the DAQ system and the ASIC mezzanine, it integrates two 16-channel ADCs for digitizing the outputs of the analog ASIC and a calibration pulse generator for detector signal injection. The analog ASICs under test are mounted on the ASIC mezzanine boards, their outputs are connected to the front-end test board through an FMC connector. A Xilinx ZC706 evaluation board is utilized as the DAQ board for this test stand, a Gigabit Ethernet link is implemented on the DAQ board for slow control, configuration and ADC data transmission. The tests of two front-end analog ASICs with this test stand are ongoing. The preliminary test results demonstrated that this test stand is suitable for the testing of the multi-channel analog ASICs developed for the LAr Calorimeter HL-LHC upgrade.

X-ray polarimetry promises to give qualitatively new information bout high-energy astrophysical sources, such as binary black hole systems, micro-quasars, active galactic nuclei, and gamma-ray bursts. We designed, built and tested ahard X-ray polarimeter, X-Calibur, to be used in the focal plane of the InFOCuS grazing incidence hard X-ray telescope.X-Calibur combines a low-Z Compton scatterer with a CZT detector assembly to measure the polarization of 20−60 keV X-rays making use of the fact that polarized photons Compton scatter preferentially perpendicular to the electric field orientation; in principal, a similar space-borne experiment could be operated in the 5−100 keV regime. X-Calibur achieves a high detection efficiency of order unity.

We have constructed a pixelated germanium detector using a technique which has been shown to provide good isolation between adjacent pixels. In this work we present initial tests of the application of a low-noise CMOS ASIC to read out this detector. The detector has 64 pixels, each 0.5mm × 5mm, arranged as a series of strips. It is connected by wire-bonds to two 32-channel ASICs (Application-Specific Integrated Circuit) which provide a complete photon-counting chain for every channel. Since the size of the pixel array is no longer restricted by the difficulties of instrumenting large channel-count conventional electronics, this development will open up the possibility of even larger arrays, similar to those offered by silicon detectors.

Intraocular cancer is a serious threat to the lives of those that suffer from it. Dosimetry for eye brachytherapy presents a significant challenge due to the inherently steep dose gradients that are needed to treat such small tumours in close proximity to sensitive normal structures. This issue is addressed by providing much needed quality assurance to eye brachytherapy, a novel volumetric dosimetry system, called Panoptes was developed. This study focuses on the preliminary characterisation and calibration of the system. Using ion beam facilities, the custom, pixelated silicon detector of Panoptes was shown to have good charge collection uniformity and a well defined sensitive volume. Flat-field calibration was conducted on the device using a 250 kVp orthovoltage beam. Finally, the detector and phantom were simulated with Monte Carlo in Geant4, to create water equivalent dose correction factors for each pixel across a range of angles.

We present our results from testing 15×15×10 mm3 CdZnTe pixelated detectors using a readout system based on the H3D ASIC. Data obtained with an uncollimated 137Cs source helped reveal details of the operational principle of such devices, and how the pulse-processing electronics may influence their performance. The responses of individual pixels were compared by using two different pulse processing approaches based on the analog shaping (H3D ASIC) and fitting of the waveforms as read out from hybrid preamplifiers.

We present VMM1, the first prototype of a family of front-end ASICs designed for the ATLAS muon upgrade. The ASIC will operate with MICROMEGAS and TGC detectors, providing charge and timing measurements along with other features including sub-hysteresis discrimination, address of the first event in real time, and digital output per channel for Time-over-Threshold measurements. The shaper, designed via the concept of Delayed Dissipative Feedback (DDF), supports analog dynamic ranges in excess of 10 \thinspace000. With a capacitance of 200 pF and a nominal peaking time of 25 ns, the ASIC offers resolution of charge and timing better than 1 fC and 1 ns, respectively, for input charges up to 2 pC. Designed in a commercial 130 nm technology it dissipates about 4.5 mW per channel.

CdZnTe (CZT) is a wide band-gap II–VI semiconductor and can be used as detector for hard X-rays in astronomical instrumentation and for medical applications. Angular and energy resolutions, as well as detection efficiencies are crucial parameters to characterize the performance of CZT detectors. We studied the detector performance as a function of the geometrical layout of the anode pixel matrix for two 2 × 2 cm 2 CZT detectors with thicknesses of 2 mm and 5 mm, respectively. We varied the pixel sizes as well as their relative distances and quantified the energy resolutions and detection efficiencies. We also studied how a steering grid located between pixels affects the energy resolution and detection rate. The results of the study are presented and suggest that a steering grid substantially improves the high-energy performance of thin detectors—whereas thick detectors mainly benefit from larger pixel widths.

Homogeneity of properties related to material crystallinity is a critical parameter for achieving high-performance CdZnTe (CZT) radiation detectors. Unfortunately, this requirement is not always satisfied in today's commercial CZT material due to high concentrations of extended defects, in particular subgrain boundaries, which are believed to be part of the causes hampering the energy resolution and efficiency of CZT detectors. In the past, the effects of subgrain boundaries have been studied in Si, Ge and other semiconductors. It was demonstrated that subgrain boundaries tend to accumulate secondary phases and impurities causing inhomogeneous distributions of trapping centers. It was also demonstrated that subgrain boundaries result in local perturbations of the electric field, which affect the carrier transport and other properties of semiconductor devices. The subgrain boundaries in CZT material likely behave in a similar way, which makes them responsible for variations in the electron drift time and carrier trapping in CZT detectors. In this work, we employed the transient current technique to measure variations in the electron drift time and related the variations to the device performances and subgrain boundaries, whose presence in the crystals were confirmed with white beam X-ray diffraction topography and infrared transmission microscopy.

The objective of this paper is to describe a Switcher ASIC with 64 high voltage output channels. Each channel provides two high voltage control pulses with maximum amplitudes of 32 V. The high voltage level shifter was designed with a current mirror switching circuit that has a readily adjustable switching speed, unlike conventional switching circuits. The logic control circuit uses a forward and reverse chain of Flip-Flops along with other combinational logic gates to generate bidirection sequential control pulses with adjustable pulsewidth and polarity. The layout was carefully designed to achieve a 14 μ m width for the last stage transistors' drain path based on the 50 μm output channel pitch set up. At least a 200 mA current driving capability was obtained for each channel. The design was fabricated using TSMC's 180 nm CMOS HV technology. The paper further discusses the critical design steps including chip architecture, layout, simulation and bench test. The final experimental results demonstrate that the Switcher ASIC meets requirements and the rising time could reach 480 ns with a 1 nF capacitive load at 15 V pulse amplitude. With this load, the total power consumption of the chip was measured to be approximately 4 mW when the input clock period was 42.2 μs. In addition to use in a charge-pump detector, the ASIC can be used to control the charge accumulation and readout in other detectors, such as X-ray pump probe detectors (XPP).

New results from testing an array of 6 $\,\times\,$ 6 $\,\times\,$ 15 mm $^{3}$ virtual Frisch-grid CdZnTe (CZT) detectors with common-cathode readout for charge signals correction and rejection of incomplete charge collection events (ICC) are presented. The array employs parallelepiped-shaped crystals of a large geometrical aspect ratio with two planar contacts on the top and bottom surfaces (anode and cathode) and an additional shielding electrode placed on the sides to create the virtual Frisch-grid effect. The detectors are arranged in 2 $\,\times\,$ 2 or 3 $\,\times\,$ 3 detector modules with the common cathode readout by a single electronic channel. Because of the common cathode, the length of the shielding electrode can be further reduced with no adverse effects on the device performance. By implementing a novel technique for rejecting ICC events caused by the extended defects, we can achieve good spectral responses from ordinary CZT crystals, which can be produced with higher yield and at lower cost. For such crystals, the resolution of individual detectors is expected to be in the range of 0.8–1.5% FWHM at 662 keV with an average value of 1.3%. Arrays of virtual Frisch-grid detectors offer a robust and low-cost approach for making large-area detection modules that can potentially substitute for more advanced, but also more expensive and less available, pixel detectors in applications with slightly relaxed requirements on position- and energy-resolution (e.g., for coded aperture telescopes). In addition, such virtual Frisch-grid arrays will require a comparably smaller number of readout channels, which allows for lower power consumption.

Two 20 mm × 20 mm × 15 mm pixelated CZT detectors made by eV-Products were characterized using the new H3D Application Specific Integrated Circuits (ASIC) readout system developed by the Instrumentation Division at Brookhaven National Laboratory. The ASIC is capable of reading out energy and timing signals from 121 anode pixels and the planar cathode electrode of one CZT detector simultaneously. The system has a measured electronic noise of ~2.2 keV FWHM with a dynamic range from 20 keV to 3.0 MeV. The two detectors achieved energy resolution of 0.48% FWHM and 0.60% FWHM, respectively, at 662 keV for single-pixel events from the entire 6.0 cm3 detection volume at room temperature with an un-collimated 137Cs source. The average (μτ)e of both detectors were measured to be >; 10-2 cm 2/V. The detection efficiency of the two detectors was evaluated at several different energies up to 1.3 MeV by comparing with simulated data. It was found that the total counts agree well between the measured data and the simulated data over the studied energy range. However, the measured photopeak counts were 10-15% lower than simulated photopeak counts at high gamma-ray energies. The analysis shows that the loss of photopeak efficiency is likely due to the charge loss from peripheral pixels to the boundary of detectors.

MicroBooNE experiment is to build a ∼170 tons Liquid Argon (LAr) Time Projection Chamber (TPC) detector that will observe interactions of neutrinos from the on-axis Booster Neutrino Beam and off-axis NuMI Beam at Fermi National Accelerator Laboratory. The experiment will address the low energy excess observed by the MiniBooNE experiment, measure low energy neutrino cross sections, and serve as the necessary next step in a phased program towards massive Liquid Argon TPC detectors. MicroBooNE TPC will have 3 readout wire planes with 8,256 wires/signal channels. All the signals will be pre–amplified, shaped, digitized and pre-processed online before recording for offline analysis of a wide variety of physics programs. To optimize the detector performance and signal-to-noise ratio, analog front end ASIC designed in 180 nm CMOS technology will be deployed and operated in LAr. Pre-amplified and shaped detector signals will be differentially driven to ADC boards operated in detector hall where signals are digitized and prepared for online data pre-processing in FPGAs. This article is an overview of the front end readout architecture of the MicroBooNE experiment, which describes the development of the front end readout electronics and preliminary test results.

We start with an analysis of the configurations commonly adopted to implement linear shapers. We show that, once the ENC from the charge amplifier is defined, the dynamic range of the system is set by the voltage swing and the value of the capacitance realizing the poles. The configuration used to realize the poles has also an impact, and those configurations based on passive components in feedback are expected to offer a higher dynamic range than the ones that use both active and passive components, like scaling mirrors. Finally, we introduce the concept of delayed dissipative feedback (DDF), which consists of delaying the resistive feedbacks from the furthest available nodes along the shaping chain. We will show that, in order to implement semi-Gaussian shapers, a small capacitor in positive feedback is required. The DDF technique can overcome some of the limitations of the more classical configurations. For example, in a third order shaper a factor of two higher dynamic range can be obtained or, at equal dynamic range, about 25% of the capacitance is needed (i.e. about 30% of the area in practical cases).

CdZnTe (CZT) is a wide bandgap II-VI semiconductor developed for the spectroscopic detection of X-rays and {\gamma}-rays at room temperature. The Swift Burst Alert Telescope is using an 5240 cm2 array of 2 mm thick CZT detectors for the detection of 15-150 keV X-rays from Gamma-Ray Bursts. We report on the systematic tests of thicker (\geq 0.5 cm) CZT detectors with volumes between 2 cm3 and 4 cm3 which are potential detector choices for a number of future X-ray telescopes that operate in the 10 keV to a few MeV energy range. The detectors contacted in our laboratory achieve Full Width Half Maximum energy resolutions of 2.7 keV (4.5%) at 59 keV, 3 keV (2.5%) at 122 keV and 4 keV (0.6%) at 662 keV. The 59 keV and 122 keV energy resolutions are among the world-best results for \geq 0.5 cm thick CZT detectors. We use the data set to study trends of how the energy resolution depends on the detector thickness and on the pixel pitch. Unfortunately, we do not find clear trends, indicating that even for the extremely good energy resolutions reported here, the achievable energy resolutions are largely determined by the properties of individual crystals. Somewhat surprisingly, we achieve the reported results without applying a correction of the anode signals for the depth of the interaction. Measuring the interaction depths thus does not seem to be a pre-requisite for achieving sub-1% energy resolutions at 662 keV., Comment: 15 pages, 11 figures

The fundamental parameter method for quantitative SXRF and PIXE analysis and imaging using the dynamic analysis method is extended to model the changing X-ray yields and detector sensitivity with angle across large detector arrays. The method is implemented in the GeoPIXE software and applied to cope with the large solid-angle of the new Maia 384 detector array and its 96 detector prototype developed by CSIRO and BNL for SXRF imaging applications at the Australian and NSLS synchrotrons. Peak-to-background is controlled by mitigating charge-sharing between detectors through careful optimization of a patterned molybdenum absorber mask. A geological application demonstrates the capability of the method to produce high definition elemental images up to ∼100 M pixels in size.

Application of nuclear microprobe event-by-event data acquisition approaches to synchrotron elemental imaging is at the heart of the design of a large energy-dispersive detector array called Maia, under development by CSIRO and BNL for SXRF elemental imaging on the X-ray microprobe. A new project is aimed at harnessing this development to provide high throughput PIXE imaging on the CSIRO Nuclear Microprobe. Maia combines a 1.2 sr solid-angle 384 detector array, integrated scanning and real-time processing including spectral deconvolution of full-spectral data. Results using a Maia prototype demonstrate the potential using SXRF application data with elemental images of up 100 M pixels.

Synchrotron X-ray fluorescence (SXRF) and X-ray absorption spectroscopy (XAS) have become standard tools to measure element concentration, distribution at micrometer- to nanometer-scale, and speciation (e.g., nature of host phase; oxidation state) in inhomogeneous geomaterials. The new Maia X-ray detector system provides a quantum leap for the method in terms of data acquisition rate. It is now possible to rapidly collect fully quantitative maps of the distribution of major and trace elements at micrometer spatial resolution over areas as large as 1 × 5 cm2. Fast data acquisition rates also open the way to X-ray absorption near-edge structure (XANES) imaging, in which spectroscopic information is available at each pixel in the map. These capabilities are critical for studying inhomogeneous Earth materials. Using a 96-element prototype Maia detector, we imaged thin sections of an oxidized pisolitic regolith (2 × 4.5 mm2 at 2.5 × 2.5 μm2 pixel size) and a metamorphosed, sedimentary exhalative Mn-Fe ore (3.3 × 4 mm2 at 1.25 × 5 μm2). In both cases, As K -edge XANES imaging reveals localized occurrence of reduced As in parts of these oxidized samples, which would have been difficult to recognize using traditional approaches.

Neutrinoless double beta decay (0v\b{eta}\b{eta}) is considered the best potential resource to access the absolute neutrino mass scale. Moreover, if observed, it will signal that neutrinos are their own anti-particles (Majorana particles). Presently, this physics case is one of the most important research "beyond Standard Model" and might guide the way towards a Grand Unified Theory of fundamental interactions. Since the 0v\b{eta}\b{eta} decay process involves nuclei, its analysis necessarily implies nuclear structure issues. In the NURE project, supported by a Starting Grant of the European Research Council (ERC), nuclear reactions of double charge-exchange (DCE) are used as a tool to extract information on the 0v\b{eta}\b{eta} Nuclear Matrix Elements. In DCE reactions and \b{eta}\b{eta} decay indeed the initial and final nuclear states are the same and the transition operators have similar structure. Thus the measurement of the DCE absolute cross-sections can give crucial information on \b{eta}\b{eta} matrix elements. In a wider view, the NUMEN international collaboration plans a major upgrade of the INFN-LNS facilities in the next years in order to increase the experimental production of nuclei of at least two orders of magnitude, thus making feasible a systematic study of all the cases of interest as candidates for 0v\b{eta}\b{eta}.

We report on the design and estimated performance of a balloon-borne hard X-ray polarimeter called HX-POL. The experiment uses a combination of Si and Cadmium Zinc Telluride detectors to measure the polarization of 50 keV-400 keV X-rays from cosmic sources through the dependence of the angular distribution of Compton scattered photons on the polarization direction. On a one-day balloon flight, HX-POL would allow us to measure the polarization of bright Crab-like sources for polarization degrees well below 10%. On a longer (15-30 day) flight from Australia or Antarctica, HX-POL would be be able to measure the polarization of bright galactic X-ray sources down to polarization degrees of a few percent. Hard X-ray polarization measurements provide unique venues for the study of particle acceleration processes by compact objects and relativistic outflows. In this paper, we discuss the overall instrument design and performance. Furthermore, we present results from laboratory tests of the Si and CZT detectors., Comment: Contribution to the 2008 Nuclear Science Symposium, Medical Imaging Conference and 16th Room Temperature Semiconductor Detector Workshop, 19 - 25 October 2008, Dresden, Germany, Paper R4-6, published in Transactions on Nuclear Science

Several sets of hexagonal Silicon Drift Detector (SDD) arrays were produced by Brookhaven National Laboratory (BNL) and by the commercial vendor, KETEK. These detector arrays were tested at BNL. Each array consists of 14 independent SDD detectors (pixels) and two additional test pixels located at two corners of the array. The side of the detector upon which the X-ray radiation is incident (window side) has a thin junction covering the entire active area. The opposite side (device side) contains a drift-field electrode structure in the form of a hexagonal spiral and an electron collecting anode. There are four guard rings surrounding the 14-pixel array area on each side of the detector. Within each array, seven pixels have aluminum field plates - interrupted spirals that stabilize the electric potential under the Si- SiO2 interface, while the other seven do not. Three bias voltages are applied to control the drift field in the silicon volume; one is applied to a rectifying contact surrounding the central anode (one for each pixel), one is applied to the detector entrance window (common to the full array), and a third bias is applied to a contact on the outer portion of the spiral, common to all pixels in the array. Some arrays were recently tested in NSLS beam line U3C at BNL. For this work, we installed the complete assemblies in the vacuum and cooled them to -27degC. During this beam run, we collected spectra for energies ranging between 350 and 900 eV in several pixels, some with field plates and others without. The detailed testing results of several arrays are reported here.

We describe an application specific integrated circuit (ASIC) for 3D position-sensitive detectors. It was optimized for pixelated cadmium-zinc-telluride (CZT) sensors, and it measures, corresponding to an ionizing event, the energy and timing of signals from 121 anodes and one cathode. Each channel provides low-noise charge amplification, high-order shaping, along with peak- and timing-detection. The cathode's timing can be measured in three different ways: the first is based on multiple thresholds on the charge amplifier's voltage output; the second uses the threshold crossing of a fast-shaped signal; and the third measures the peak amplitude and timing from a bipolar shaper. With its power of 2 mW per channel the ASIC measures, on a CZT sensor connected and biased, charges up to 100 fC with an electronic resolution better than 200 e- rms. Our preliminary spectral measurements applying a simple cathode/anode ratio correction demonstrated a single-pixel resolution of 4.8 keV (0.72 %) at 662 keV, with the electronics and leakage current contributing in total with 2.1 keV.

Frisch-ring CdZnTe detectors have demonstrated good energy resolution for identifying isotopes

A detector concept is described that integrates a large solid-angle detector array developed at Brookhaven National Laboratory and a high speed pipelined parallel processing engine developed at CSIRO for machine vision, with an embedded implementation of the Dynamic Analysis method for fluorescence spectra deconvolution and image projection, to yield a detection system capable of energy-dispersive detection, spectral deconvolution and real-time elemental imaging at ∼108 events per second for PIXE elemental imaging using the nuclear microprobe and SXRF elemental imaging using the synchrotron X-ray microprobe.

We present an ASIC for a 3He gas detector to be used in small angle neutron scattering experiments at the spallation neutron source in oak ridge. The ASIC is composed of 64 channels with low noise charge amplification, filtering, timing and amplitude measurement circuits, where an innovative current-mode peak-detector and digitizer (PDAD) is adopted. The proposed PDAD provides at the same time peak detection and A/D conversion in real time, at low power, and without requiring a clock signal. The channels share an efficient data sparsification and derandomization scheme, a 30-bit 256 deep FIFO, and low voltage differential signaling.