Prototype Detector Research Articles

Significantly Boosted Photothermoelectric Effect via Carrier Injection in Au Decorated SWCNT Films for Infrared Detection

AbstractCarbon nanotubes (CNTs) have established their promising application as infrared photodetector and the photothermoelectric (PTE) effect is demonstrated to play a critical role. While extensive studies are focused on the optoelectronic behaviors, the thermoelectric conversion involved in the PTE has been pursued to less extent probably due to the overall low thermopower under infrared (IR) illumination. Herein, to trigger a stronger PTE response, Au/CNT heterojunctions are formed by Au nanoparticles (NPs) decoration of CNT films to facilitate both light absorption and carrier transportation, so that thermoelectric property is enhanced simultaneously. Significant boost on infrared radiation energy conversion capability is therefore enabled in Au NPs decorated CNT film, delivering maximum output voltage of 26.1 mV and power of 27.3 µW, outperforming the state‐of‐the art photodetectors based on PTE effect. The transport mechanism is revealed via combining in situ Kelvin Probe Force Microscope mapping of the surface potential and macroscopic transport and output performances under IR illumination. Finally, the IR detection function is validated via an 8‐channel IR detector prototype, presenting sensitive responsivity and long‐term cyclic stability. The study thus demonstrates the PTE effect as a promising platform toward high‐performance optoelectronic applications such as IR detection and solar energy harvesting.

Demonstration of a 25-picosecond single-photon time resolution with gaseous photomultiplication

Photosensitive gaseous detectors with a simple photoelectron multiplication mechanism of resistive plate chambers (RPCs) are expected to have both a large photocoverage and an excellent time resolution and to be low-cost. To demonstrate the time resolution of the RPC-based photodetectors, we built a prototype detector with a LaB6 photocathode. It was tested with a picosecond pulse laser and the intrinsic time resolution for single photons was measured to be 25.0±1.1 ps at a gain of 3.3×106.

Detailed simulation for the ClearMind prototype detection module and event reconstruction using artificial intelligence

The ClearMind project aims to develop the TOF-PET position sensitive detection module optimized for the time resolution, spatial resolution, and detection efficiency. For this, the ClearMind project uses a large (59 × 59 mm2) monolithic PbWO4 (PWO) scintillating crystal with a bialkali photo-electric layer deposited directly on the crystal. Scintillation and Cherenkov photons result together from the 511 keV gamma-ray interaction into the PWO crystal. A micro-channel plate photomultiplier tube (MCP-PMT) encapsulating the PWO crystal amplifies photoelectrons generated at the photocathode, and the corresponding anode signals are collected through the transmission lines read out at both ends and digitized by a SAMPIC module. In this work, we present a realistic Geant4 simulation of the ClearMind prototype detector, including the propagation of the visible photons in the crystal, the modeling of a realistic response of the photocathode and of the PMT, and the propagation of the electrical signals over the transmission lines. The reconstruction of the gamma conversion in the detector volume is performed from the signals registered at both ends of the transmission lines. We compare the reconstruction precision of a statistical algorithm against machine learning algorithms developed using the TMVA package. We expect to reach a spatial resolution down to a few mm3 (FWHM). Finally, we will discuss prospects for the ClearMind detector.

Transmission-Based Muography for Ore Bodies Prospecting: A Case Study from a Skarn Complex in Italy

Transmission-based muography (TM) is an innovative imaging technique based on the measurement and analysis of the cosmic ray muons flux attenuation within the target under investigation. This technique allows imaging inner-body density differences and has successfully been applied in a wide range of research fields: geology, archaeology, engineering geology and civil engineering. The aim of this study is to show the reliability of TM as an innovative, noninvasive geophysical method for ore body prospecting and other mining related studies. The measurements were carried out at the Temperino mine in the San Silvestro Archaeological and Mining Park (Campiglia Marittima, Italy), where several magmatic and metasomatic geological units are embodied. Among them, a Cu–Fe–Zn–Pb(–Ag) sulfide skarn complex primarily composed by hedenbergite and ilvaite minerals. Using the acquired muon imaging data obtained with the MIMA (Muon Imaging for Mining and Archaeology) detector prototype (cubic detector of 0.5 × 0.5 × 0.5 m3), the presence of a high-density vein inside the skarn body within the rock volume above the muon detector was identified, localized and interpreted. Applying a back-projection algorithm to the obtained 2D transmission map made it possible to estimate and visualize as point cloud data, in a 2D or 3D environment, the identified high-density body and its relative distance from the detector. The results of this study highlight the potential of muography as a support tool to other geophysical methods in the field of mining exploration.

Latest progress of PandaX-III neutrinoless double beta decay experiment

Neutrinoless double beta decay experiments are one of the most promising approaches to resolving the puzzle of neutrino mass generation. PandaX-III experiment searches the neutrinoless double beta decay of 136Xe with a high-pressure gaseous time projection chamber. A total amount of 140 kg enriched 136Xe under 10 bar will be loaded in the detector. Micromegas is used for charge collection with a high spatial resolution. Benefitting from the long event track in the gaseous detector, identification algorithms can significantly suppress the background rate. In this proceeding, the design and construction of the detector is presented, whose technologies have been successfully demonstrated by a prototype detector. The event classification algorithms were developed, suppressing the background events at a rate of about 300. Based on the result, we expect an exclusion sensitivity of 2.7×1026 yr (90% C.L.) for decay half life after 5 years’ exposure.

X-ray and electrical characterization of a multipixel diamond-based detector in high temperature environments

An 8-pixel X-ray diamond detector prototype, fabricated on an alumina substrate and specifically designed to operate at high temperature, has been developed and tested. Tungsten electrodes were developed as metal-semiconductor contact and showed an ohmic behavior, as inferred from current-voltage measurements. A 40-cycles thermal stress test performed in helium atmosphere, in which temperature has been varied cyclically between 100 and 240 °C, showed minor evolution of the detector dark current, presumably related to progressive water desorption from the alumina substrate. Conversely, X-ray photocurrent measurements showed no significant differences before and after the thermal cycles, confirming no degradation of the stability of the prototype even after prolonged operation at high temperature.

Layer thickness characterization of Faraday cup fast ion loss detectors.

Faraday cup fast ion loss detectors have attractive properties for fusion applications, as they can measure wide ranges of energy, are intrinsically neutron-hardened, and can be packaged in very small form factors. The latter allows them to be installed as arrays, offering opportunities to decouple fast ion loss location and magnitude in fully three-dimensional magnetic fields. In this work, we characterize the layer thicknesses of detector prototypes using spectral reflectance measurements, confocal laser scanning microscopy, as well as raster electron microscopy with a focused ion beam. We find that the measured layer thicknesses agree well enough with the specification to allow for accurate measurements. The as-manufactured heights are on the high side, increasing reliability. The data presented here further sets the basis for future optimizations in manufacturing.

Observation on the bias current variation of a single mask triple GEM chamber

Gas Electron Multiplier (GEM) detector, one of the advanced members of the Micro Pattern Gas Detector (MPGD) group, is widely used in High Energy Physics (HEP) experiments. The high rate handling capability and spatial resolution make it a desired tracking detector for high rate HEP experiments. Investigation of the long-term stability is an essential criterion for any tracking device used in HEP experiments. To investigate the long-term stability of a Single Mask (SM) triple GEM detector prototype, it is irradiated continuously using a 55Fe X-ray source of energy 5.9 keV. The chamber is operated with Ar/CO2 gas mixture in continuous flow mode. The gain and energy resolution of the chamber are calculated from the 5.9 keV X-ray peak and studied as a function of time. The applied voltage, divider current and also the environmental parameters (ambient temperature, pressure and relative humidity) are recorded continuously. It is observed that at a fixed applied voltage, the divider current of the detector is changing with time and as a result, the gain of the detector also changes. A systematic investigation is carried out to understand the probable reasons behind the observed variation in divider current and also to find its possible remedies. The details of the experimental setup, methodology and results are discussed in this article.

Robust Thermal Neutron Detection by LiInP2 Se6 Bulk Single Crystals.

Direct neutron detection based on semiconductor crystals holds promise to transform current neutron detector technologies and further boosts their widespread applications. It is, however, long impeded by the dearth of suitable materials in the form of sizeable bulk crystals. Here, we have developed high-quality centimeter-sized LiInP2 Se6 single crystals using the Bridgman method and systematically investigated their structure and property characteristics. The prototype detectors fabricated from the crystals demonstrate an energy resolution of 53.7% in response to α-particles generated from an 241 Am source and robust, well-defined response spectra to thermal neutrons that exhibit no polarization or degradation effects under prolonged neutron/γ-ray irradiation. We have also identified the primary mechanisms of Se-vacancy and InLi antisite defects in the carrier trapping process. Such insights are critical for further enhancing the energy resolution of LiInP2 Se6 bulk crystals towards the intrinsic level (∼8.6% as indicated by our chemical vapor transport-grown thin crystals). These results pave the way for practically adopting LiInP2 Se6 single crystals in new-generation solid-state neutron detectors. This article is protected by copyright. All rights reserved.

A CNN-based four-layer DOI encoding detector using LYSO and BGO scintillators for small animal PET imaging

Objective. We propose a novel four-layer depth-of-interaction (DOI) encoding phoswich detector using lutetium–yttrium oxyothosilicate (LYSO) and bismuth germanate (BGO) scintillator crystal arrays for high sensitivity and high spatial resolution small animal PET imaging. Approach. The detector was comprised of a stack of four alternating LYSO and BGO scintillator crystal arrays coupled to an 8 × 8 multi-pixel photon counter (MPPC) array and read out by a PETsys TOFPET2 application specific integrated circuit. The four layers from the top (gamma ray entrance) to the bottom (facing the MPPC) consisted of a 24 × 24 array of 0.99 × 0.99 × 6 mm3 LYSO crystals, a 24 × 24 array of 0.99 × 0.99 × 6 mm3 BGO crystals, a 16 × 16 array of 1.53 × 1.53 × 6 mm3 LYSO crystals and a 16 × 16 array of 1.53 × 1.53 × 6 mm3 BGO crystals. Main results. Events that occurred in the LYSO and BGO layers were first separated by measuring the pulse energy (integrated charge) and duration (time over threshold (ToT)) from the scintillation pulses. Convolutional neural networks (CNNs) were then used to distinguish between the top and lower LYSO layers and between the upper and bottom BGO layers. Measurements with the prototype detector showed that our proposed method successfully identified events from all four layers. The CNN models achieved a classification accuracy of 91% for distinguishing the two LYSO layers and 81% for distinguishing the two BGO layers. The measured average energy resolution was 13.1% ± 1.7% for the top LYSO layer, 34.0% ± 6.3% for the upper BGO layer, 12.3% ± 1.3% for the lower LYSO layer, and 33.9% ± 6.9% for the bottom BGO layer. The timing resolution between each individual layer (from the top to the bottom) and a single crystal reference detector was 350 ps, 2.8 ns, 328 ps, and 2.1 ns respectively. Significance. In conclusion, the proposed four-layer DOI encoding detector achieved high performance and is an attractive choice for next-generation high sensitivity and high spatial resolution small animal positron emission tomography systems.

In-beam test results of the Super-FRS GEM-TPC detector prototype with relativistic uranium ion beam

As an essential part of the Super-FRS particle identification, the GEM-TPC detector in a twin field-cage configuration will provide position information at up to 1 MHz counting rate with a spatial resolution < 1 mm and with tracking efficiency >95 %. This detector is designed to provide particle-beam tracking information of projectiles ranging from protons to uranium. The performance of the GEM-TPC detector in a single field-cage configuration and newly integrated AWAGS readout electronics with a differential output was studied at the FRS for the response to the uranium beam at 850 MeV/u with intensity up to 1000 ions/spill. The result shows that a clusterization algorithm developed for this analysis works properly. The spatial resolution of 0.74–0.81 mm, a detection efficiency >99 %, and a tracking efficiency >96 % were found. This work describes the methodology used to achieve such results in detail.

A hybrid 3D/2D field response calculation for liquid argon detectors with PCB based anode plane

Liquid Argon Time Projection Chamber (LArTPC) technology is commonly utilized in neutrino detector designs. It enables detailed reconstruction of neutrino events with high spatial precision and low energy threshold. Its field response (FR) model describes the time-dependent electric currents induced in the anode-plane electrodes when ionization electrons drift nearby. An accurate and precise FR is a crucial input to LArTPC detector simulations and charge reconstruction. Established LArTPC designs have been based on parallel wire planes. It allows accurate and computationally economic two-dimensional (2D) FR models utilizing the translational symmetry along the direction of the wires. Recently, novel LArTPC designs utilize electrodes formed on printed circuit board (PCB) in the shape of strips with through holes. The translational symmetry is no longer a good approximation near the electrodes and a new FR calculation that employs regions with three dimensions (3D) has been developed. Extending the 2D models to 3D would be computationally expensive. Fortuitously, the nature of strips with through holes allows for a computationally economic approach based on the finite-difference method (FDM). In this paper, we present a new software package pochoir that calculates LArTPC field response for these new strip-based anode designs. This package combines 3D calculations in the volume near the electrodes with 2D far-field solutions to achieve fast and precise field response computation. We apply the resulting FR to simulate and reconstruct samples of cosmic-ray muons and 39Ar decays from a Vertical Drift (VD) detector prototype operated at CERN. We find the difference between real and simulated data within 5%. Current state-of-the-art LArTPC software requires a 2D FR which we provide by averaging over one dimension and estimate that variations lost in this average are smaller than 7%.

Demonstration of Gd-GEM detector design for neutron macromolecular crystallography applications

The European Spallation Source (ESS) in Lund, Sweden will become the world's most powerful thermal neutron source. The Macromolecular Diffractometer (NMX) at the ESS requires three 51.2 × 51.2 cm2 detectors with reasonable detection efficiency, sub-mm spatial resolution, a narrow point-spread function (PSF), and good time resolution. This work presents measurements with the improved version of the NMX detector prototype consisting of a Triple-GEM (Gas Electron Multiplier) detector with a natural Gd converter and a low material budget readout. The detector was successfully tested at the neutron reactor of the Budapest Neutron Centre (BNC) and the D16 instrument at the Institut Laue-Langevin (ILL) in Grenoble. The measurements with Cadmium and Gadolinium masks in Budapest demonstrate that the point-spread function of the detector lacks long tails that could impede the measurement of diffraction spot intensities. On the D16 instrument at ILL, diffraction spots from Triose phosphate isomerase w/ 2-phosphoglycolate (PGA) inhibitor were measured both in the MILAND Helium-3 detector and the Gd-GEM. The comparison between the two detectors shows a similar point-spread function in both detectors, and the expected efficiency ratio compared to the Helium-3 detector. Both measurements together thus give good indications that the Gd-GEM detector fits the requirements for the NMX instrument at ESS.

The XYU-GEM: Ambiguity-free coordinate readout of the Gas Electron Multiplier

We describe the development of a position-sensitive Gas Electron Multiplier detector prototype, providing for each ionizing event three coordinates: the cartesian X and Y, and U at 45°. Simultaneous recording of the three projections permits ambiguity-free reconstruction of multiple tracks, and aims at operation in very high intensity radiation fields.

Cosmic ray test of a STCF DTOF detector prototype

A time-of-flight detector based on detection of internally reflected Cherenkov light (DTOF), is proposed for the endcap particle identification at the Super Tau-Charm Facility (STCF). A prototype with a trapezoidal fused silica radiator that had a size of 533 mm/ 295 mm × 454 mm × 15 mm is constructed, which is approximately one-third of the size of the DTOF sector proposed for STCF. A field-programmable-gate-array-based dual-threshold time-over-threshold measurement circuit is employed to read signals from the microchannel-plate photomultiplier tube, which performs functions such as signal amplification, discrimination, and digitization. The DTOF prototype was tested in a cosmic ray telescope, which realizes 3D tracking of cosmic ray muons with an angular resolution of < 1 mrad, position resolution of <200μm, and reference time resolution of 24 ps. To analyze and understand the performance of the DTOF prototype, a GEANT4 simulation is employed. The time resolution of the DTOF prototype is 25 ps by using 10 or more photoelectrons in the cosmic ray test, which is in good agreement with the simulation result, proving the feasibility of this technology.

Classification of breast microcalcifications with GaAs photon-counting spectral mammography using an inverse problem approach

The purpose of this study was to investigate the use of a Gallium Arsenide (GaAs) photon-counting spectral mammography system to differentiate between Type I and Type II calcifications. Type I calcifications, consisting of calcium oxalate dihydrate (CO) or weddellite compounds are more often associated with benign lesions in the breast, and Type II calcifications containing hydroxyapatite (HA) are associated with both benign and malignant lesions in the breast. To be able to differentiate between these two calcification types, it is necessary to be able to estimate the full spectrum of the x-ray beam transmitted through the breast. We propose a novel method for estimating the energy-dependent x-ray transmission fraction of a beam using a photon counting detector with a limited number of energy bins. Using the estimated x-ray transmission through microcalcifications, it was observed that calcification type can be accurately estimated with machine learning. The study was carried out on a custom-built laboratory benchtop system using the SANTIS 0804 GaAs detector prototype system from DECTRIS Ltd with two energy thresholds enabled. Four energy thresholds detector was simulated by taking two separate acquisitions in which two energy thresholds were enabled for each acquisition and set at (12 keV, 21 keV) and then (29 keV, 36 keV). Measurements were performed using BR3D (CIRS, Norfolk, VA) breast imaging phantoms mimicking 100% adipose and 100% glandular tissues swirled together in an approximate 50/50 ratio by weight with the addition of in-house-developed synthetic microcalcifications. First, an inverse problem-based approach was used to estimate the full energy x-ray transmission fraction factor using known basis transmission factors from varying thicknesses of aluminum and polymethyl methacrylate (PMMA). Second, the classification of Type I and Type II calcifications was performed using the estimated energy-dependent transmission fraction factors for the pixels containing calcifications. The results were analyzed using receiver operating characteristic (ROC) analysis and demonstrated good discrimination performance with the area under the ROC curve greater than 84%. They indicated that GaAs photon-counting spectral mammography has potential use as a non-invasive method for discrimination between Type I and Type II calcifications. Results from this study suggested that GaAs-based spectral mammography could serve as a non-invasive measure for ruling out malignancy of calcifications found in the breast. Additional studies in more clinically realistic conditions involving breast tissues samples with smaller microcalcification specks should be performed to further explore the feasibility of this approach.

A high sensitivity Cherenkov detector for prompt gamma timing and time imaging

We recently proposed a new approach for the real-time monitoring of particle therapy treatments with the goal of achieving high sensitivities on the particle range measurement already at limited counting statistics. This method extends the Prompt Gamma (PG) timing technique to obtain the PG vertex distribution from the exclusive measurement of particle Time-Of-Flight (TOF). It was previously shown, through Monte Carlo simulation, that an original data reconstruction algorithm (Prompt Gamma Time Imaging) allows to combine the response of multiple detectors placed around the target. The sensitivity of this technique depends on both the system time resolution and the beam intensity. At reduced intensities (Single Proton Regime—SPR), a millimetric proton range sensitivity can be achieved, provided the overall PG plus proton TOF can be measured with a 235 ps (FWHM) time resolution. At nominal beam intensities, a sensitivity of a few mm can still be obtained by increasing the number of incident protons included in the monitoring procedure. In this work we focus on the experimental feasibility of PGTI in SPR through the development of a multi-channel, Cherenkov-based PG detector with a targeted time resolution of 235 ps (FWHM): the TOF Imaging ARrAy (TIARA). Since PG emission is a rare phenomenon, TIARA design is led by the concomitant optimisation of its detection efficiency and Signal to Noise Ratio (SNR). The PG module that we developed is composed of a small PbF_{2} crystal coupled to a silicon photoMultiplier to provide the time stamp of the PG. This module is currently read in time coincidence with a diamond-based beam monitor placed upstream the target/patient to measure the proton time of arrival. TIARA will be eventually composed of 30 identical modules uniformly arranged around the target. The absence of a collimation system and the use of Cherenkov radiators are both crucial to increase the detection efficiency and the SNR, respectively. A first prototype of the TIARA block detector was tested with 63 MeV protons delivered from a cyclotron: a time resolution of 276 ps (FWHM) was obtained, resulting in a proton range sensitivity of 4 mm at 2sigma with the acquisition of only 600 PGs. A second prototype was also evaluated with 148 MeV protons delivered from a synchro-cyclotron obtaining a time resolution below 167 ps (FWHM) for the gamma detector. Moreover, using two identical PG modules, it was shown that a uniform sensitivity on the PG profiles would be achievable by combining the response of gamma detectors uniformly distributed around the target. This work provides the experimental proof-of-concept for the development of a high sensitivity detector that can be used to monitor particle therapy treatments and potentially act in real-time if the irradiation does not comply to treatment plan.

3D printing of inorganic scintillator-based particle detectors

Inorganic scintillators are widely used for scientific, industrial and medical applications. The development of 3D printing with inorganic scintillators would allow the fast creation of detector prototypes for the registration of ionizing radiation, such as alpha, beta and gamma particles in thin layers of active material, and X-ray radiation. This article reports on the technical work and scientific achievements that aimed at developing a new inorganic scintillation filament to be used for the 3D printing of composite scintillator materials: study and definition of the scintillator composition; development of the methods for the inorganic scintillator filament production and further implementation in the available 3D printing technologies; study of the impact of the different 3D printing modes on the material scintillation characteristics. Also, 3D-printed scintillators can be used to produce combined detectors for high-energy physics.

A simple and low-cost directional detection technique for radiation source localization for nuclear security applications

One of the goals in the field of nuclear security is to prevent the misuse and loss of nuclear or other radiological materials. If lost or stolen, radioactive materials could be located and secured using radiation detectors like count rate meters or imaging systems. However, such detectors may not allow for the swift localization of lost sources or may be cost prohibitive in many measurement scenarios. A simple, low-cost, directional radiation detector that is capable of quickly “pointing” towards the nearest radiation source is sought for source search scenarios. Such a detector can be realized using a plastic scintillator couple on each end to photo-multiplier tubes, as shown in this work. The event-by-event position of scintillation in this study is approximated by averaging the amount of light arriving at each of the photomultiplier tubes during coincidence counting. The detector system is then rotated so that the approximated scintillation positions within the detector volume can be determined in other spatial dimensions. A guess vector generated by comparing light ratio skewness produced by the detector in orthogonal orientations points in the direction of a nearby radiation source. An MCNPX-PoliMi model was used to guide the design of such a detector and validate the guess-vector technique. A prototype system using a cube of an EJ-204 plastic scintillator and two photomultiplier tubes was constructed and a correlation between azimuthal source position and detector response was established. For measurements of tens of thousands of counts, the detector prototype generates guess vectors that can identify source position to within 5° uncertainty. The detector prototype can determine the general direction of a nearby source to within 45° uncertainty using 1000 total counts.

A study on motion reduction for suspended platforms used in gravitational wave detectors

We report a reduction in motion for suspended seismic-isolation platforms in a gravitational wave detector prototype facility. We sense the distance between two seismic-isolation platforms with a suspension platform interferometer and the angular motion with two optical levers. Feedback control loops reduce the length changes between two platforms separated by 11.65,textrm{m} to 10,mathrm {pm,Hz}^{-1/2} at 100,textrm{mHz}, and the angular motion of each platform is reduced to 1,mathrm {nrad, Hz}^{-1/2} at 100,textrm{mHz}. As a result, the length fluctuations in a suspended optical resonator on top of the platforms is reduced by three orders of magnitude. This result is of direct relevance to gravitational wave detectors that use similar suspended optics and seismic isolation platforms.