Detector Assembly Research Articles

Novel neutron detector assembly based on SiPM readout to be coupled with the Active Target for SPES

The Active Target ATS (Active Target for SPES) is a new time-projection chamber designed for reaction and decay studies with nuclei far from stability. The physics cases for the new-generation active target are related to the ongoing developments of facilities for radioactive ion beams. Thanks to its flexibility, this instrument will be capable of taking advantage of the most exotic beams which will become available at the SPES facility under construction at the Legnaro National Laboratories in Italy. Particular attention will be also paid to couple it with ancillary detectors, for both charged and neutral (gamma and neutrons) particles. In particular, in this work, we will focus the attention on the neutron ancillary detectors. The proposed prototype is a compact device able to discriminate, by performing pulse shape analysis, between neutrons and gamma. The device take advantage of recent improvements in silicon photomultiplier (SiPM) technology and the development of new plastic scintillators exhibiting neutron/gamma discrimination capability. Our work is focused on the read-out with silicon photomultipliers arrays of EJ-276 (and its old version EJ-299) and EJ-276G scintillators of several sizes (ranging from 20 mm to 50 mm diameter). Moreover, we will show the comparison of discrimination performances between SiPM and standard photomultiplier read-out configurations.

Impact of bowtie filter and detector collimation on multislice CT scatter profiles: A simulation study

To investigate via Monte Carlo simulations, the impact of scan subject size, antiscatter grid (ASG), collimator size, and bowtie filter on the distribution of scatter radiation in a typical realistically modeled third generation 16 slice diagnostic computed tomography (CT) scanner. Full radiation transport was simulated with Geant4 in a realistic CT scanner geometric model, including the imaging phantom, bowtie filter (BTF), collimators and detector assembly, except for the ASGs. An analytical method was employed to quantify the probable transmission through the ASG of each photon intersecting the detector array. Normalized scatter profiles (NSP) and scatter-to-primary-ratio (SPR) profiles were simulated for 90 and 140kVp beams for different size phantoms and slice thicknesses. The impact of CT scatter on the reconstructed attenuation coefficient factor was also studied as were the modulating effects of phantom- and patient-tissue heterogeneities on scatter profiles. A method to characterize the relative spatial frequency content of sinogram signals was developed to assess the latter. For the 21.4-cm diameter phantom, NSP and SPR increase linearly with collimator opening for both tube potentials, with the 90kVp scan exhibiting slightly larger NSP and SPR. The BTF modestly modulates scatter under the phantom center, reducing the prominent off-axis lobes by factors of 1.1-1.3. The ASG reduces scatter on the central axis NSP threefold, and reduces scatter at the detectors outside the phantom shadow by factors of 25 to 500. For the phantoms with diameters of 27 and 32cm, the scatter increases roughly three- and fourfold, respectively, demonstrating that scatter monotonically increases with phantom size, despite deployment of the ASG and BTF. In the absence of a scan subject, the ASG reduces the signal profile arising photons scattered by the BTF. Without ASG, the in-air scatter profile is relatively flat compared to the scatter profile when the ASG is present. For both 90 and 140 kVp photon spectra, the calculated attenuation coefficient decreases linearly with increasing collimation size. For both homogeneous and heterogeneous objects, NSPs are dominated by low spatial frequency content compared to the primary signal. However, the SPR, which quantifies the local magnitude of nonlinear detector response and is dominated by the high frequency content of the primary profile, can contribute strongly to high-spatial frequency streaking artifacts near high-density structures in reconstructed image artifacts. Public-domain Monte Carlo codes, Geant-4 in particular, is a feasible method for characterizing CT detector response to scattered- and off-focal radiation. Our study demonstrates that the ASG substantially reduces the scatter radiation and reshapes scatter-radiation profiles and affects the accuracy with which the detector array can measure narrow-beam attenuation due its inability to distinguish between true uncollided primary and narrow-angle coherently scattered photons. Hence, incorporating the impact of detector array collimation into the forward-projection signal formation models used by iterative reconstruction algorithms is necessary to use CT for accurately characterizing material properties. While tissue heterogeneities exercise a modest influence on local NPS shape and magnitude, they do not add significant high spatial frequency content.

The LUX-ZEPLIN (LZ) radioactivity and cleanliness control programs

LUX-ZEPLIN (LZ) is a second-generation direct dark matter experiment with spin-independent WIMP-nucleon scattering sensitivity above {1.4 times 10^{-48}}, {hbox {cm}}^{2} for a WIMP mass of {40}, hbox {GeV}/{hbox {c}}^{2} and a {1000}, hbox {days} exposure. LZ achieves this sensitivity through a combination of a large {5.6}, hbox {t} fiducial volume, active inner and outer veto systems, and radio-pure construction using materials with inherently low radioactivity content. The LZ collaboration performed an extensive radioassay campaign over a period of six years to inform material selection for construction and provide an input to the experimental background model against which any possible signal excess may be evaluated. The campaign and its results are described in this paper. We present assays of dust and radon daughters depositing on the surface of components as well as cleanliness controls necessary to maintain background expectations through detector construction and assembly. Finally, examples from the campaign to highlight fixed contaminant radioassays for the LZ photomultiplier tubes, quality control and quality assurance procedures through fabrication, radon emanation measurements of major sub-systems, and bespoke detector systems to assay scintillator are presented.

Assembly and performance study of a triple gas electron multiplier with a 55Fe source

In this work, a process for the assembly of a standard triple Gas Electron Multiplier detector and the study of the main variables was made at the Universidad Antonio Nariño, Colombia, detectors laboratory. The triple gas electron multiplier was tested with Ar/CO2 mixtures in proportions of 70/30%, 80/20% and 90/10% using a 55Fe X-ray source (5.9 keV). The energy spectrum, energy resolution, effective gain and ionization rate were analyzed according to the applied voltage and the Ar/CO2 gas mixture. The Universidad Antonio Nariño, Colombia, triple gas electron multiplier detector obtained an energy resolution of up to 19% and an effective gain close to 104; where the detection efficiency is approximately 95%. These results were compared with other studies to check the triple gas electron multiplier performance.

Rapid PXRF soil organic carbon and organic matter assessment using novel modular radiation detector assembly

Soil organic matter and organic carbon are variables of critical environmental importance in terms of soil productivity and function, global food security, and climate change mitigation. Rapid and accurate assessment of these variables is central to national programs and international agreements. Portable X-ray fluorescence instruments are widely used to rapidly quantify and map soil elements, however quantification of light elements that constitute the majority of organic materials is not yet possible with this technique (e.g. carbon). We developed a novel attachment for portable X-ray fluorescence instrumentation enabling concurrent volumetric soil organic matter and organic carbon quantification during PXRF analyses. This primary prototype outperformed more expensive visible-near infrared instrumentation using parsimonious soil specific simple linear regression (R2 ranged 0.85–0.97) enabling rapid, parallel, nondestructive, cost-effective acquisition of soil elemental concentrations together with soil organic carbon and soil organic matter data.

Mitigating artifacts by data driven identification & correction of rotational misalignment in gamma ray computed tomography

Industrial Computed Tomography (ICT) is a radiation based cross sectional imaging technique that requires a sample to be manipulated precisely in a specific geometry to acquire analytically useful data. Unlike medical CT, industrial CT may require use of gamma radiation from radio-isotopes like Co60, Cs137 etc. having higher energy radiations for penetrating through higher density and thickness of material under inspection. Data acquisition in ICT involves use of a mechanical manipulator to rotate either the specimen or the source and detectors assembly in circular and linear geometry. Misalignment in mechanical set-up leads to significant artifacts in CT image. The effects may be even more pronounced in data acquired with discrete detector as against Linear Detector Array (LDA) because of certain built-in mechanical integrity associated with LDA. This paper discusses cross correlation based software correction method for combination of gamma ray source and NaI (Tl) scintillation detector based transmission ICT system in parallel beam CT geometry. The proposed correction does not require calibration of the set-up and any prior knowledge of the sample geometry or composition. This data driven correction yields improved CT reconstruction with limited data. The method is demonstrated with a mathematical simulation and applied to experimental data for validation.

Development of ultra-pure NaI(Tl) detectors for the COSINE-200 experiment

The annual modulation signal observed by the DAMA experiment is a long-standing question in the community of dark matter direct detection. This necessitates an independent verification of its existence using the same detection technique. The COSINE-100 experiment has been operating with 106 kg of low-background NaI(Tl) detectors providing interesting checks on the DAMA signal. However, due to higher backgrounds in the NaI(Tl) crystals used in COSINE-100 relative to those used for DAMA, it was difficult to reach final conclusions. Since the start of COSINE-100 data taking in 2016, we also have initiated a program to develop ultra-pure NaI(Tl) crystals for COSINE-200, the next phase of the experiment. The program includes efforts of raw powder purification, ultra-pure NaI(Tl) crystal growth, and detector assembly techniques. After extensive research and development of NaI(Tl) crystal growth, we have successfully grown a few small-size (0.61–0.78 kg) thallium-doped crystals with high radio-purity. A high light yield has been achieved by improvements of our detector assembly technique. Here we report the ultra-pure NaI(Tl) detector developments at the Institute for Basic Science, Korea. The technique developed here will be applied to the production of NaI(Tl) detectors for the COSINE-200 experiment.

SciFi, the new Tracker of the LHCb experiment

The LHCb Collaboration is currently in the final stage of constructing an upgraded detector that will allow the experiment to operate at higher luminosities and with a triggerless readout. The main tracking stations—which originally were subdivided in an Inner Tracker made from silicon strip sensors and an Outer Tracker built from straw-tubes—are being replaced by a single tracking detector, the Scintillating fibre Tracker (SciFi). The SciFi covers a total detector area of 340 m2 by using more than 10000 km of scintillating fibre with 250 μm diameter, enabling a spatial resolution of better than 100 μm for hits originating from charged particles. It is built from individual modules (0.5 m × 4.8 m) comprised of 8 scintillating fibre mats with a length of 2.4 m as the active detector material. The 13 cm wide fibre mats consist of 6 layers of densely packed blue emitting scintillating fibres. The scintillation light is detected with arrays of multi-channel silicon photomultipliers (SiPMs) cooled to −40̂C to minimize the expected high dark noise from neutron radiation. The readout of 524k channels occurs through custom-designed front-end electronics. Since it is the first time that this technology is being used as a large tracker and with a small granularity, many challenges have to be overcome. This document is intended to give an overview of the SciFi detector design, production, performance and the status of the detector assembly.

The X-ray scanning technique application for sTGC detectors quality control

The gas detectors, operated under harsh radiation conditions like the one foreseen at the High Luminosity LHC (HL-LHC), must fulfill a number of stringent quality control criteria. Based on high-voltage current measurements, the X-ray scanning technique has been developed for discovery of various production defects prior to the readout electronics installation. The later usually happens at the last stage of detector assembly. Thus, it allows testing the quality of the chambers, identifying defects and when possible fixing them already at early stage.

Test study of the operating performance of a mechanically pumped two-phase loop for a space remote sensor

To increase the imaging indexes of space remote sensors, temperature stability is required for the core optical detector assembly in the working stage. However, with traditional products, it is difficult to meet the requirements of precise temperature control for a high-power module. A mechanically pumped two-phase loop (MPTL) is highly advantageous as an essential thermal control product in space cameras. In this study, one MPTL setup was constructed to investigate the operating behaviors caused by the heat source of the core detector assembly for the load-on and load-off status. One two-phase thermal-controlled accumulator integrated with passive cooling was first employed as the temperature control component of the system, and the shield centrifugal pump was selected to be the driving force. The obtained test data, which included the temperature, pressure, and mass flow-rate, were used to analyze the thermodynamic behaviors in the accumulator. In addition, the heat and mass transfer processes between the main loop and the accumulator and the operating characteristic of the main loop were investigated. This research focuses on the instability phenomena that occur during the phase transition of the system and during the heat source load-on and load-off status; a method to decrease the system instability has been proposed. In addition, the operating behaviors of the main loop and the accumulator during the power change of the heat source have also been investigated. The results show that there was a temperature difference between the gas and liquid phases in the accumulator, and the cooling capacity of the accumulator was obtained as the temperature difference. The temperatures of the multi-evaporators showed excellent performance in the area of stability and uniformity, which provided good boundary conditions for the stabilization imaging of the space camera. The temperatures and pressure in the accumulator and the flow-rate and flow resistance of system will be affected by the starting up and powering off of the heat sources. The system stability during the process of phase change was influenced by the loading power on the pre-heater. The variations in the heating load affect the operating state of the accumulator and main loop. The results obtained from this study can be used to guide the design and application of the MPTL system for space remote sensors.

The CLAS12 Backward Angle Neutron Detector (BAND)

The Backward Angle Neutron Detector (BAND) of CLAS12 detects neutrons emitted at backward angles of 155° to 175°, with momenta between 200 and 600 MeV/c0. It is positioned 3-m upstream of the target, consists of 18 rows and 5 layers of 7.2-cm by 7.2-cm scintillator bars, and read out on both ends by PMTs to measure time and energy deposition in the scintillator layers. Between the target and BAND there is a 2-cm thick lead wall followed by a 2-cm veto layer to suppress gammas and reject charged particles. This paper discusses the component-selection tests and the detector assembly. Timing calibrations (including offsets and time-walk) were performed using a novel pulsed-laser calibration system, resulting in time resolutions better than 250 ps (150 ps) for energy depositions above 2 MeV (5 MeV). Cosmic rays and a variety of radioactive sources were used to calibration the energy response of the detector. Scintillator bar attenuation lengths were measured. The time resolution results in a neutron momentum reconstruction resolution, δp/p<1.5% for neutron momentum 200≤p≤600 MeV/c. Final performance of the BAND with CLAS12 is shown, including electron–neutral particle timing spectra and a discussion of the off-time neutral contamination as a function of energy deposition threshold.

Spherical Dichroic Reflector Improves Limit of Detection in Laser-Induced Fluorescence Detection.

A miniature laser-induced fluorescence (mLIF) detector utilizing a novel spherical dichroic reflector (SDR), an unconventional long working distance high magnification objective, an uncommon broadband emission-matched excitation filter pair, and a silicon-based photodiode detector assembly instead of a photomultiplier tube was developed and evaluated. The detection cell was placed at the spherical center of the SDR instead of the regular focus, yielding a 1.8× signal-to-noise ratio (SNR) improvement. Different from previous works, the use of a 40× objective with a long working distance of 5.38 mm and a broadband BP 527-70 nm emission filter with matched BP 450-30 nm excitation filter improved SNR to 4.6× and 1.9×, respectively. By flow injection analysis (FIA) evaluation, the limit of detection (LOD; 3σ method) for fluorescein sodium was 1.5 × 10-13 M or 8.9 fluorescein molecules in 98 pL detection volume, which was the lowest level of LIFs evaluated by FIA mode. The analysis of three kinds of amino acids with LODs at sub pM to fM level (the lowest levels, hundreds of times lower than previous works using normal capillary) demonstrated the potential of the mLIF in ultratrace analysis of biological and environmental samples, including low copy molecules in a single cell.

Femtosecond soft X-ray absorption spectroscopy of warm dense matter at the PAL-XFEL.

Free-electron laser pulse-based X-ray absorption spectroscopy measurements on warm dense copper are presented. The incident X-ray pulse energies were measured with a detector assembly consisting of a photocathode membrane andmicrochannel plates, and the transmitted energies were measured simultaneously with a photodiode detector. The precision of the absorption measurements was evaluated. For a warm dense copper foil irradiated by an intense femtosecond laser pulse, the enhanced X-ray absorption below the L3-edge, followed by the rapid evolution of highly excited Fermi liquid within apicosecond, were successfully measured. This result demonstrates a unique capability to study femtosecond non-equilibrium electron-hole dynamics in extreme states of matter.

Study of the 232Th(n,f) Cross section at NCSR ‘Demokritos’ using Micromegas Detectors

The accurate knowledge of neutron-induced fission cross sections in actinides, is of great importance when it comes to the design of fast nuclear reactors, as well as accelerator driven systems. Specifically for the 232Th(n,f) case, the existing experimental datasets are quite discrepant in both the low and high energy MeV regions, thus leading to poor evaluations, a fact that in turn implies the need for more accurate measurements.In the present work, the total cross section of the 232Th(n,f) reaction has been measured relative to the 235U(n,f) and 238U(n,f) ones, at incident energies of 7.2, 8.4, 9.9 MeV and 14.8, 16.5, 17.8 MeV utilizing the 2H(d,n) and 3H(d,n) reactions respectively, which generally yield quasi-monoenergetic neutron beams. The experiments were performed at the 5.5 MV Tandem accelerator laboratory of N.C.S.R. “Demokritos”, using a Micromegas detector assembly and an ultra thin ThO2 target, especially prepared for fission measurements at n_ToF, CERN during its first phase of operations, using the painting technique. The masses of all actinide samples were determined via α-spectroscopy. The produced fission yields along with the results obtained from activation foils were studied in parallel, using both the NeusDesc [1] and MCNP5 [2] codes, taking into consideration competing nuclear reactions (e.g. deuteron break up), along with neutron elastic and inelastic scattering with the beam line, detector housing and experimental hall materials. Since the 232Th(n,f) reaction has a relatively low energy threshold and can thus be affected by parasitic neutrons originating from a variety of sources, the thorough characterization of the neutron flux impinging on the targets is a prerequisite for accurate cross-section measurements, especially in the absence of time-of-flight capabilities. Additional Monte-Carlo simulations were also performed coupling both GEF [3] and FLUKA [4] codes for the determination of the detection efficiency.

Development of a Spark-Detection System for the Quality Assurance of Large-Area GEM-Foils

Gaseous detectors based on large-size GEM-foils are planned to be used for a variety of upgrades and new experiments using high-rate and high-intensity particle beams. An excellent quality control of GEM-foils is a mandatory prerequisite to select the best foils for the assembly of a GEM detector. The high voltage stability of the foils is here of uppermost importance. In particular discharges that occur at the same position need to be detected. A spark detection system has been developed to automatically detect and record the time and position of sparks. The system is based on a commercial web camera installed in a housing for the tests and a custom-made, LabVIEW-based software for control and operation. An automatic Spark-Detection System for GEM foils was designed, built and characterized. It is able to detect and record discharges in large-size GEM foils during the quality control procedure. The spark detection e ciency was estimated to be higher than 97 %, the position resolution was determined to be approximately 0.5 mm. With this system, the characterization of GEM foils can be standardized to a much greater degree than before.

Test Beam Results from sPHENIX prototype Time Projection Chamber

The sequential melting of Upsilon states gives us information about the Debye Screening length of Quark Gluon Plasma (QGP). To observe this sequential melting at RHIC energies of 200GeV, a Time Projection Chamber, as part of the sPHENIX detector assembly, with ability to resolve the Upsilon states is proposed. This paper details the construction of the prototype TPC, the method of analysis of test beam data and its results.

PMT glass window sensitivity to gamma-rays: A digital signal processing approach

A digital data acquisition system together with MATLAB software for data analysis were utilised to measure the pulse specification of the scintillation detector assembly. Besides, the sensitivity of a photomultiplier tube (PMT) window to gamma-rays was studied to discriminate the signals produced as a result of gamma-ray interactions inside the glass window from those originating from the scintillator cell. The result showed that an algorithm based on the time features was capable to evaluate the contributions of these two different signals.

The CUPID-Mo experiment for neutrinoless double-beta decay: performance and prospects

CUPID-Mo is a bolometric experiment to search for neutrinoless double-beta decay (0nu beta beta ) of ^{100}hbox {Mo}. In this article, we detail the CUPID-Mo detector concept, assembly and installation in the Modane underground laboratory, providing results from the first datasets. The CUPID-Mo detector consists of an array of 20 ^{100}hbox {Mo}-enriched 0.2 kg hbox {Li}_2hbox {MoO}_4 crystals operated as scintillating bolometers at sim 20hbox { mK}. The hbox {Li}_2hbox {MoO}_4 crystals are complemented by 20 thin Ge optical bolometers to reject alpha events by the simultaneous detection of heat and scintillation light. We observe a good detector uniformity and an excellent energy resolution of 5.3 keV (6.5 keV) FWHM at 2615 keV, in calibration (physics) data. Light collection ensures the rejection of alpha particles at a level much higher than 99.9% – with equally high acceptance for gamma /beta events – in the region of interest for ^{100}hbox {Mo}0nu beta beta . We present limits on the crystals’ radiopurity: le 3~mu hbox {Bq/kg} of ^{226}hbox {Ra} and le 2~mu hbox {Bq/kg} of ^{232}hbox {Th}. We discuss the science reach of CUPID-Mo, which can set the most stringent half-life limit on the ^{100}hbox {Mo}0nu beta beta decay in half-a-year’s livetime. The achieved results show that CUPID-Mo is a successful demonstrator of the technology developed by the LUMINEU project and subsequently selected for the CUPID experiment, a proposed follow-up of CUORE, the currently running first tonne-scale bolometric 0nu beta beta experiment.

640×512数字化InGaAs探测器组件

Digital InGaAs detector significantly orients the development of short wave (SW) infrared detector technology, it not only can increase integrated level of the system, but also can develop the imager’s performance. The key point to realize the digital InGaAs detector is integrating ADC into the readout integrated circuit (ROIC) and realize digital ROIC (DROIC). The 640×512 DROIC was designed and fabricated, it interconnected InGaAs detector focal plane array with In and realized digital InGaAs detector assembly. The proposed digital InGaAs detector assembly was tested, and the measurement results show that its readout noise is 230 μV, peak quantum efficiency is 65%, detectivity under 300 K temperature is 1.2×1012 cm Hz1/2 / W, and the power consumption is 94 mW when frame rate is 60 Hz. The measurement results indicate that the digital InGaAs detector assembly has some features as low readout noise, high linearity, wide transmission bandwidth, good resistance to interference and so on.

星载红外探测器组件环境适应性分析与性能优选

星载红外探测器组件环境适应性分析与性能优选