Prototype Detector Research Articles

Spectral and polarimetric characterization of the Gas Microchannel plate Pixel Detector

The Gas Microchannel plate Pixel Detector (GMPD) is used to measure X-ray polarization in astrophysical sources, and is the prototype of the Low Energy Polarimeter Detector (LPD) in the POLAR-2 project. The choice of the detector's gas mixture has a profound impact on its sensitivity to polarized X-rays. Here, we present the characteristics of the GMPD filled with a mixture of 40% He and 60%DME at 0.8 atm. Using Bragg diffraction, we generated nearly fully polarized and monochromatic X-rays at an angle of approximately 45°, and for the first time, we measured the modulation factor and spectral capability at energies of 2.98 keV, 4.51 keV, 6.40 keV, and 8.05 keV. The energy resolution measured is 18% at 6.40 keV, inversely proportional to the square root of the X-ray energy. The measured modulation factors were close to those obtained for the GPD developed by INFN-Pisa and INAF/IASF-Rome, reaching approximately 0.5 above 6 keV, allowing a comparison of the sensitivity of the GMPD and GPD.

Digital radiography by counting photons: innovative solution for testing very thick parts

In 2019 we presented the first prototype of a photon counting detector (PCD) specially designed for the inspection of very thick parts requiring the use of high energy (HE) sources (E > 200keV). HE PCD differs from the standard model by the following characteristics: 1) Photoconductor CdTe active layer thickness optimized for HE, with about 30% increased detection efficiency; 2) Completely renewed ASIC allowing selection of energy threshold up to 1300keV. Modification 2) allows to reduce scattered radiation when using gamma sources such as Iridium 192 and Cobalt 60; or pulsed sources like linear accelerators and betatrons. The object-contrast results from this considerably improved. Image quality is comparable to, if not better than, film. We present energy threshold optimization study and performance evaluation results in terms of ISO 19232 IQI (wire and hole), signal-to-noise ratio, and spatial resolution (via duplex IQI) according to ISO 17636_2 (class B). Focus is given to HE PCD/film comparison, which was carried out by means of mock-ups containing artificial and/or real flaws; and, in 2020, for the first time in a nuclear power plant site, for the examination of primary circuit dissimilar welds. Photons energy thresholding successfully addressed also the presence of background radiation. The latter represented 2% of counted photons, while with film, background was responsible of 13% of optical density.

Performance of the CMS High Granularity Calorimeter prototype to charged pion beams of 20–300 GeV/c

The upgrade of the CMS experiment for the high luminosity operation of the LHC comprises the replacement of the current endcap calorimeter by a high granularity sampling calorimeter (HGCAL). The electromagnetic section of the HGCAL is based on silicon sensors interspersed between lead and copper (or copper tungsten) absorbers. The hadronic section uses layers of stainless steel as an absorbing medium and silicon sensors as an active medium in the regions of high radiation exposure, and scintillator tiles directly read out by silicon photomultipliers in the remaining regions. As part of the development of the detector and its readout electronic components, a section of a silicon-based HGCAL prototype detector along with a section of the CALICE AHCAL prototype was exposed to muons, electrons and charged pions in beam test experiments at the H2 beamline at the CERN SPS in October 2018. The AHCAL uses the same technology as foreseen for the HGCAL but with much finer longitudinal segmentation. The performance of the calorimeters in terms of energy response and resolution, longitudinal and transverse shower profiles is studied using negatively charged pions, and is compared to GEANT4 predictions. This is the first report summarizing results of hadronic showers measured by the HGCAL prototype using beam test data.

NEXT-CRAB-0: a high pressure gaseous xenon time projection chamber with a direct VUV camera based readout

The search for neutrinoless double beta decay (0νββ) remains one of the most compelling experimental avenues for the discovery in the neutrino sector. Electroluminescent gas-phase time projection chambers are well suited to 0νββ searches due to their intrinsically precise energy resolution and topological event identification capabilities. Scalability to ton- and multi-ton masses requires readout of large-area electroluminescent regions with fine spatial resolution, low radiogenic backgrounds, and a scalable data acquisition system. This paper presents a detector prototype that records event topology in an electroluminescent xenon gas TPC via VUV image-intensified cameras. This enables an extendable readout of large tracking planes with commercial devices that reside almost entirely outside of the active medium. Following further development in intermediate scale demonstrators, this technique may represent a novel and enlargeable method for topological event imaging in 0νββ.

Simulation of a neutron imaging detector prototype based on SiPM array readout

Neutron imaging technology as a means of non-destructive detection of materials is complementary to X-ray imaging. Silicon photomultiplier (SiPM), a new type of optical readout device, has overcome some shortcomings of traditional photomultiplier tube (PMT), such as high-power consumption, large volume, high price, uneven gain response, and inability to work in strong magnetic fields. Its application in the field of neutron detection will be an irresistible general trend. In this paper, a thermal neutron imaging detector based on 6LiF/ZnS scintillation screen and SiPM array readout was developed. The design of the detector geometry was optimized by geant4 Monte Carlo simulation software. The optimized detector was evaluated with a step wedge sample. The results show that the detector prototype with a 48 mm × 48 mm sensitive area can achieve about 38% detection efficiency and 0.26 mm position resolution when using a 300 μm thick 6LiF/ZnS scintillation screen and a 2 mm thick Bk7 optical guide coupled with SiPM array, and has good neutron imaging capability. It provides effective data support for developing high-performance imaging detectors applied to the China Spallation Neutron Source (CSNS).

Preliminary characterisation of the HEXITECMHz spectroscopic X-ray imaging detector

The HEXITECMHz ASIC is the next generation of the STFC's High Energy X-ray Imaging Technology (HEXITEC). With a ×100 increase in the camera frame rate to 1 MHz, the new ASIC is capable of delivering fully spectroscopic X-ray imaging at photon fluxes of 2×106 photons s-1 mm-2. The improved flux capability ensures the relevance of the technology at a new generation of difraction-limited storage ring (DLSR) synchrotrons as well as enabeling dynamic spectroscopic imaging with sub-keV energy resolution to be carried out on millisecond timescales. In this paper preliminary results from X-ray testing of a 0.3 mm thick p-type Si sensor and 2.0 mm thick HF-CdZnTe sensor at the Diamond Light Source Synchrotron are presented for the first time. Each module consists of 80 × 80 pixels on a 250 μm pixel pitch operated at a temperature of 20°C and a frame rate of 1 MHz. For these preliminary measurements, testing was completed using a prototype test system which limited readout to a portion of the 1 MHz output sampled over an SPI test interface at ∼50 Hz. Despite this limitation these measurements allow the spectroscopic performance of the ASIC to be characterised ahead of the full DAQ system. The prototype detectors were characterised using monochromatic X-rays with energies 12–35 keV at fluxes of (0.6 – 2.5) × 106 photons s-1 mm-2. At an X-ray energy of 12 keV, the energy resolution of the p-type Si and HF-CdZnTe detectors were measured to be 1.0 keV and 1.1 keV respectively. At the higher energies of 20 keV and 35 keV the energy resolution in the HF-CdZnTe was measured to be 1.2 keV and 1.4 keV respectively.

Baksan large neutrino telescope: current status

The status of the Baksan Large Neutrino Telescope project and some selective results of the first stage of the project, namely a prototype detector with a liquid scintillator mass of 0.5 tons are described. The results of the second stage of the project, a prototype with a liquid scintillator mass of 5 tons, and the prospects for the project are discussed.

Readout electronics for the CEPC vertex detector prototype and beam telescope

The proposed Circular Electron Positron Collider (CEPC) imposes unique requirements on the vertex detector. In response, the MOST1 and MOST2 projects were launched with the aim of developing a fully functional pixel sensor and implementing the prototype of the inner tracking detector. To efficiently manage the data flow from multiple sensors, specialized readout electronics are required. In order to evaluate the MOST2 project indicators set for the vertex detector prototype, a beam telescope was constructed using six TaichuPix-3 sensor chips and applied in different experiments. The experimental results demonstrate that the telescope functions effectively and that the detector prototype meets the design objectives of the MOST2 project. This project encompasses the design of the readout electronics, the functionality of the readout system, the architecture of the telescope, and the specifics of the telescope experiments.

Development and test of the Micromegas detector prototype and its readout electronics for the AMBER experiment at CERN

Several spectrometer upgrades are planned for future phases of the AMBER (NA66) experiment at CERN. Among these upgrades, the replacement of some aging Multi-Wire Proportional Chambers has motivated a R&D program to develop a Micro-Pattern Gaseous Detector and its front-end electronics. The results of testing the first small Micromegas prototype with the TIGER-based front-end are presented.

High Count Rate Peak-Based PET Detector

Determining the deposited energy of a gamma interaction in a scintillator is of vital importance for PET imaging. In this paper, a peak-based PET detector that simultaneously attain a high count rate is proposed. This detector exploits a known fact that a pulse peak is roughly linear with its energy. Therefore, a fast peak detector is designed for energy characterization using peaks directly acquired from scintillation pulses without any pulse shaping techniques. The key design of this peak detector is the utilization of comparators rather than amplifiers, along with a turbocharged current source, so as to increase the slew rate and equivalently curtail the time it requires to catch the peak of a fast scintillation pulse in as few as around 40 ns. A PET detector prototype is implemented based on the designed circuit and experiments are carried out extensively to evaluate its performance. The prototype achieves an energy resolution of 14.8%@511KeV and a coincidence resolution time of 345 ps.

Silicon photomultiplier based scintillator thermal neutron detector for China Spallation Neutron Source (CSNS)

The energy-resolved neutron imaging spectrometer (ERNI) will be installed in 2022 according to the spectrometer construction plan of the China Spallation Neutron Source (CSNS). The instrument requires neutron detectors with the coverage area of approximately 4 m2 in 5°–170° neutron diffraction angle. The neutron detection efficiency needs to be better than 40% at 1 Å neutron wavelength. The spatial resolution should be better than 3 mm × 50 mm in the horizontal and vertical directions respectively. We develop a one-dimensional scintillator neutron detector which is composed of the 6LiF/ZnS (Ag) scintillation screens, the wavelength-shifting fiber (WLSF) array, the silicon photomultipliers (SiPMs), and the self-designed application-specific integrated circuit (ASIC) readout electronics. The pixel size of the detector is designed as 3 mm × 50 mm, and the neutron-sensitive area is 50 mm × 200 mm. The performance of the detector prototype is measured using neutron beam 20# of the CSNS. The maximum counting rate of 247 kHz, and the detection efficiency of 63% at 1.59 Å are obtained. The test results show that the performance of the detector fulfills the physical requirements of the ERNI under construction at the CSNS.

Pulse shape discrimination and spectral performance of an inverted coaxial point contact HPGe detector with sub-pF capacitance

The inverted coaxial point contact high purity germanium (ICPC HPGe) detector exhibits the advantages of large volume, low depletion voltage, small capacitance, and excellent pulse shape discrimination (PSD) capability. An ICPC detector prototype with 0.9 pF capacitance was successfully fabricated and tested in this study using two different front-end electronics. The detector weighted approximately 1.5 kg and the depletion voltage was only 1800 V. The optimized operating voltage was found to be 2500 V and the leakage current was 7 pA. The detector was first connected to a homemade JFET based front-end with a pulsed reset design to minimize parallel noise. An energy resolution of 1.72 keV (full width at half maximum) was achieved at 1332 keV, demonstrating the good charge collection efficiency of the detector. An RC feedback front-end circuit was employed to test the PSD properties using a 228Th source. The PSD capability is similar to that of typical broad energy or point contact HPGe detectors, but is notably improved when the charge trapping is corrected using the drift time.

Detecting and characterizing special nuclear material for nuclear nonproliferation applications

There is an urgent need for new, better instrumentation and techniques for detecting and characterizing special nuclear material (SNM), i.e., highly enriched uranium and plutonium. The development of improved instruments and techniques requires experiments performed with the SNM itself, which is of limited availability. This paper describes the findings of experiments performed at the National Criticality Experiments Research Center conducted using new instruments and techniques on unclassified, kg-quantity SNM objects. These experiments, performed in the framework of the Department of Energy, National Nuclear Security Administration Consortium for Monitoring, Technology, and Verification, focused on detecting, characterizing, and localizing SNM samples with masses ranging from 3.3 to 13.8 kg, including plutonium and highly enriched uranium using prototype detectors and techniques. The work demonstrates SNM detection and characterization using recently-developed prototype detection systems. Specifically, we present new results in passive detection and imaging of plutonium and uranium objects using gamma-ray and dual particle (fast neutron and gamma-ray) imaging. We also present a new analysis of the delayed neutron emissions during active interrogation of uranium using a neutron generator.

Development of ultra-low mass and high-rate capable RPC based on Diamond-Like Carbon electrodes for MEG II experiment

A new type of resistive plate chamber with thin-film electrodes based on diamond-like carbon is under development for background identification in the MEG II experiment. Installed in a low-momentum and high-intensity muon beam, the detector is required to have extremely low mass and a high rate capability. A single-layer prototype detector with 2 cm × 2 cm size was constructed and evaluated to have a high rate capability of 1 MHz/cm2 low-momentum muons. For a higher rate capability and scalability of the detector size, the electrodes to supply high voltage were segmented at a 1 cm pitch by implementing a conductive pattern on diamond-like carbon. Using the new electrodes, a four-layer prototype detector was constructed and evaluated to have a 46% detection efficiency with only a single layer active at a rate of O(10 kHz). The result with the new electrodes is promising to achieve the required detection efficiency of 90% at a rate of 4 MHz/cm2 with all the layers active.

Capability demonstration of a 3D CdZnTe detector on a high-altitude balloon flight

In collaboration between the University of Michigan and Los Alamos National Laboratory, a 3D position-sensing CdZnTe (CZT) detector prototype was built and integrated into a high-altitude balloon platform to evaluate its performance in a space-like mixed-radiation environment. The detector prototype, Orion Eagle, was designed to operate in near-vacuum environments without any temperature regulation. Orion Eagle was hand-launched from NASA’s Columbia Scientific Balloon Facility (CSBF) at Fort Sumner, NM on September 26, 2021, and successfully operated throughout a 9-hour flight, which reached 38.5 km in altitude. The flight met its objectives, successfully detecting atmospheric gamma rays and galactic cosmic rays, and raising the Technical Readiness Level from 4 to 6 for large-volume 3D CZT detector technology for space applications. Ionization tracks produced by charged particles create spatial signatures in the detector that are distinguishable from discrete gamma-ray interactions. Therefore, the 3D position-sensing capabilities using pixelated electrodes on a CZT detector can help enable discrimination of background charged particles from gamma-ray events without an anticoincidence shield. The potential for background rejection capability, ambient-temperature operation, gamma-ray coded-aperture and Compton imaging, and near High Purity Germanium (HPGe) energy resolution motivate the use of large-volume 3D CZT imaging spectrometers in future space missions.

Liquid-organic time projection chamber for detecting low energy antineutrinos

The MeV region of antineutrino energy is of special interest for physics research and for monitoring nuclear nonproliferation. Whereas liquid scintillation detectors are typically used to detect the Inverse Beta Decay (IBD), it has recently been proposed to detect it with a liquid-organic Time Projection Chamber, which could allow a full reconstruction of the particle tracks of the IBD final state. We present the first simulation-based statistical analysis of the expected signatures. Their unequivocal signature could enable a background-minimized detection of electron antineutrinos using information on energy, location and direction of all final state particles. We show that the positron track reflects the antineutrino’s vertex. It can also be used to determine the initial neutrino energy. In addition, we investigate the possibility to reconstruct the antineutrino direction on an event-by-event basis by the energy deposition of the neutron-induced proton recoils. Our simulations indicate that this could be a promising approach which should be further studied through experiments with a detector prototype.

Successful cooling of a pixel tracker using gaseous helium: Studies with a mock-up and a detector prototype

We report the successful operation of a functional pixel detector with gaseous helium cooling. Using an accurate mock-up beforehand, the cooling was validated. We use a miniature turbo compressor to propel the helium at 2g/s under ambient pressure conditions with gas temperatures above 0 °C. Our earlier results based on computational fluid dynamics simulations and a much simpler mock-up are confirmed. With this, we paved the path to cool pixel detectors in experimental particle physics at heat densities up to 400mW/cm2 using helium. This enables cooling of detectors with very low mass requirements, minimising the effects of multiple Coulomb scattering effectively. This technique requires sensors tolerant to be operated in a wide temperature range and a detector geometry to guide the helium flow adequately. The concept presented here is not limited to pixel detector applications and can be used to cool any surface with comparable heat-densities, only limited by shaping the helium gas flow.

Neutrino characterisation using convolutional neural networks in CHIPS water Cherenkov detectors

This work presents a novel approach to water Cherenkov neutrino detector event reconstruction and classification. Three forms of a Convolutional Neural Network have been trained to reject cosmic muon events, classify beam events, and estimate neutrino energies, using only a slightly modified version of the raw detector event as input. When evaluated on a realistic selection of simulated CHIPS-5kton prototype detector events, this new approach significantly increases performance over the standard likelihood-based reconstruction and simple neural network classification.

Towards large size pixelized Micromegas for operation beyond 1 MHz/cm2

The R&D project being presented aims to improve the use of resistive Micromegas technology in high-energy physics experiments. The project focuses on achieving stable, reliable, and high-gain operation at particle flow rates above 1 MHz/cm2 on large surfaces. To achieve this, the project uses a configuration with small pads readout and requires innovative solutions for the spark protection resistive scheme. Different resistive patterns were investigated, and finally the solution based on a double layer of DLC foils was chosen, demonstrating the capability to perform equally for low and high rates under irradiation of X-rays on the full surface of 25 cm2 of the prototype detectors. With this technology and layout, a detector with an active area of 400 cm2 was recently built. In this work we present the results of high-rate capability, robustness, dependence on the irradiated area, obtained with high intensity X-rays measurements, as well as the results on efficiency and spatial resolution obtained, at low rates, at CERN SPS with high energy particle beams. Additionally, preliminary results of pixelized resistive Micromegas time response are reported. With the successful achievements of this detector and the construction of even larger small-pad resistive Micromegas next year, the project will establish the technology for future use in particle physics and other applications.

Reconstruction of the event vertex in the PandaX-III experiment with convolution neural network

The PandaX-III experiment uses a high-pressure xenon gaseous time projection chamber (TPC) to search for the neutrinoless double beta decay (0νββ) of 136Xe. The absence of the vertex position in the electron drift direction at which the event takes place in the detector limits the PandaX-III TPC’s performance. The charged particle tracks recorded by the TPC provide a possibility for vertex reconstruction. In this paper, a convolution neural network (CNN) model VGGZ0net is proposed for the reconstruction of vertex position. An 11 cm precision is achieved with the Monte Carlo simulation events uniformly distributed along a maximum drift distance of 120 cm. The electron loss during the drift under the different gas conditions is studied, and after the distance-based correction, the detector energy resolution is significantly improved. The CNN model is also verified successfully using the experimental data of the PandaX-III prototype detector.