- 标题
- 摘要
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- 实验方案
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Design and characterization of small detection modules based on scintillators and WLS bars with SiPM readout for a cosmic ray mini-array
摘要： This paper describes the design and characterization tests of detection modules for a low-cost, easily reconfigurable mini-array for cosmic rays. The basic layout of each individual module is based on a 400 cm2 scintillator tile, optically coupled to a Wavelength Shifter (WLS) bar and a Silicon Photomultiplier (SiPM) for light collection and readout. Low cost solutions, based on the Arduino MEGA board, have been adopted for electronics, triggering and data acquisition, in view of the operation of this facility. The first detection modules, equipped with 4×4 mm2 SiPMs were fully built and characterized. Additional tests were also carried out with photosensors having different sensitive area and technology.
关键词： Scintillators, scintillation and light emission processes (solid, gas and liquid scintillators),Particle detectors,Interaction of radiation with matter
更新于2025-09-23 15:23:52
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An algorithmic approach to single probe Cherenkov removal in pulsed X-ray beams
摘要： Purpose: The removal of Cherenkov light in an optical dosimetry system is an important process to ensure accurate dosimetry without compromising spatial resolution. Many solutions have been presented in the literature, each with advantages and disadvantages. We present a methodology to remove Cherenkov light from a scintillator fibre optic dosimeter in a pulsed megavoltage X-ray beam using the temporal waveform across the pulse. Methods: A sample waveform of Cherenkov light can be measured by exposing only the fibre to the beam. By assuming that the Cherenkov waveform closely matches the intensity of incident radiation, this waveform can be convoluted with the instantaneous scintillation response function to generate an expected scintillation signal. By finding the least-squares fit between these two functions and the experimental data, the estimated Cherenkov contribution can be subtracted off the net signal. This can be applied for arbitrarily complex Cherenkov waveforms (within the 2 ns timing resolution of the data acquisition), and in fact the results suggest more fluctuations in the waveforms provide a better fit to data. Results: Four beam profiles for different field sizes and energies were found with this method. They closely matched references data measured with ionisation chamber with average differences across the beam no more than 4%. Noisy waveforms are assumed to be the primary cause of differences between the analysed scintillator and IC results. We propose methods for improving the results and optimising the data acquisition and analysis processes. Conclusions: These results demonstrate that it is possible and effective with a single probe to use function-fitting of expected data to experimental to remove a complicated Cherenkov signal from the net light signal in pulsed-beam optical dosimetry.
关键词： x-ray,scintillators,fiber-optic dosimetry,microbeam radiation therapy
更新于2025-09-23 15:23:52
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Impurity induced cross luminescence in KMgCl3 : An ab-initio study
摘要： Density functional theory calculations have been carried out to calculate the electronic structure and optical properties of host and Cs doped KMgCl3. All the calculations were performed by using the Tran and Blaha modified Becke-Johnson potential (TB-mBJ) in order to accurately predict the band gap and the optical spectra. The investigated compound is found to be an insulator with direct band gap of 4.7, 6.9 eV using Generalized Gradient Approximation (GGA), and TB-mBJ functionals respectively. The calculated refractive index shows the optical isotropy of this compound in the low energy region, though the structure is anisotropic. From our theoretical calculations we predict KMgCl3 doped with Cs to be a better cross luminescence material compared to host compound, where additional Cs states are present below the valence band of the compound. Detailed discussion is presented in the manuscript.
关键词： Scintillators,Cross luminescence,Optical properties,Electronic structure
更新于2025-09-23 15:23:52
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The LXe calorimeter and the pixelated timing counter in the MEG II experiment
摘要： The MEG experiment is to look for a lepton flavor violating μ + → e+γ decay with an unprecedented sensitivity, and we set an upper limit of the branching ratio for this decay, 5.7 × 10?13 at 90% C.L. in 2013 which is a twenty times more stringent limit than the previous experiment, MEGA. Since the sensitivity improvement was limited by the accidental background, we have considered the major detector upgrade. A proposal was submitted to PSI committee, and was approved in 2013, which aims at a sensitivity enhancement of one order of magnitude compared with the current MEG experiment. Here mainly two components of the MEG detector will be introduced, a γ-ray calorimeter with 900 L of liquid xenon (LXe), and a pixelated timing counter. The LXe detector will be improved by increasing the granularity at the incident face, by replacing the current PMTs with a larger number of smaller photosensors (MPPC) and optimizing the photosensor layout also on the lateral faces. A new highly segmented, fast timing counter array will replace the old system to allow improved timing resolution capabilities.
关键词： visible and IR photons (solid-state),HPG,Large detector systems for particle and astroparticle physics,Photon detectors for UV,CZT,Gamma detectors (scintillators,HgI etc),Timing detectors
更新于2025-09-23 15:23:52
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Role of electron and hole centers in energy transfer in BaBrI crystals
摘要： In this paper we study a role of F-centers, hole centers and excitons in energy transfer in Eu-doped BaBrI crystals. Optical absorption spectra, thermally stimulated (TSL) and photostimulated (PSL) luminescence in wide temperature range 7-300 K are studied in undoped and doped with different concentrations of Eu ions BaBrI crystals. Based on experimental and calculated results two possible energy tranfer processes from host to Eu2+ ions are established.
关键词： energy transfer,thermoluminescence,alkali earth halides,scintillators,bromide,iodide,F-center,photostimulated luminescence
更新于2025-09-23 15:22:29
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crystal scintillators
摘要： The double-beta decay of 116Cd has been investigated with the help of radiopure enriched 116CdWO4 crystal scintillators (mass of 1.162 kg) at the Gran Sasso underground laboratory. The half-life of 116Cd relative to the 2ν2β decay to the ground state of 116Sn was measured with the highest up-to-date accuracy as T1=2 ? e2.63t0.11?0.12 T × 1019 yr. A new improved limit on the 0ν2β decay of 116Cd to the ground state of 116Sn was set as T1=2 ≥ 2.2 × 1023 yr at 90% C.L., which is the most stringent known restriction for this isotope. It corresponds to the effective Majorana neutrino mass limit in the range hmνi ≤ e1.0–1.7T eV, depending on the nuclear matrix elements used in the estimations. New improved half-life limits for the 0ν2β decay with majoron(s) emission, Lorentz-violating 2ν2β decay, and 2β transitions to excited states of 116Sn were set at the level of T1=2 ≥ 1020–1022 yr. New limits for the hypothetical lepton-number violating parameters (right-handed currents admixtures in weak interaction, the effective majoron-neutrino coupling constants, R-parity violating parameter, Lorentz-violating parameter, heavy neutrino mass) were set.
关键词： 116CdWO4 crystal scintillators,Majorana neutrino mass,116Cd,double-beta decay,lepton-number violating parameters,half-life
更新于2025-09-23 15:21:21
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Characterization of monolithic GAGG:Ce coupled to both PMT and SiPM array for gamma imaging in Nuclear Medicine
摘要： GaGG:Ce scintillation crystal is very useful for nuclear imaging purposes, thanks to its several advantages (high density, short decay time, high light yield and good energy resolution, no self-activity, no hygroscopic). However, only the recent improvements in the growth processes make it available with large size, in order to use it in monolithic configuration. The main drawbacks of pixelated crystals, as non-uniform response, high production costs and optical light loss, could be therefore overcome. In this work the characterization of this promising crystal coupled both to a single channel PMT (spectrometric purpose) and to a new technology SiPM (50% PDE and 74% geometrical fill factor) has been performed. The detection efficiency results good both for SPECT (87% at 122 keV) and for PET (18% at 356 keV) applications. However, the unexpected result arises from the energy resolution: at 356 keV 8.9% and 8.0% for single channel PMT and SiPM configuration, respectively. In other terms, the used SiPM allows to achieve higher energy resolution than single channel PMT. Moreover, a high imaging performance has been observed, with a millimeter intrinsic spatial resolution.
关键词： SPECT,PET PET/CT,Gamma camera,Intra-operative probes,Scintillators and scintillating fibres and light guides,coronary CT angiography (CTA),Scintigraphy and whole-body imaging
更新于2025-09-23 15:21:01
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Characteristics of Si and SiC detectors at registration of Xe ions
摘要： The results of an investigation of silicon (Si) and silicon carbide (SiC) detectors when irradiated with a beam of Xenon (Xe) ions are presented. The irradiation was carried out at the IC-100 cyclotron, JINR, Dubna. The effect of the Pulse Height Defect (PHD) in registering Xe ions with energies 165, 82 and 45 MeV is shown to be twice as large for SiC detectors as that for Si detectors. It is also shown that degradation of SiC detectors irradiated with heavy Xe ions occurs at doses an order of magnitude greater than for Si detectors. The measurement method described, including continuous detector calibration by alpha-particles, makes it possible to simultaneously control the characteristics of detectors during irradiation and determine the energy of a beam of ions.
关键词： Radiation-hard detectors,Heavy-ion detectors,Solid state detectors,Gamma detectors (scintillators, CZT, HPG, HgI etc)
更新于2025-09-23 15:19:57
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Optical properties of InAs quantum Dots/GaAs waveguides for ultra-fast scintillators
摘要： InAs Quantum Dots (QDs) embedded in a GaAs matrix have unique scintillation properties, valuable for high-energy physics and medical applications. Temperature-dependent photoluminescence, waveguide attenuation and alpha particle response measurements were employed to analyze the optical properties of a 25 m m thick waveguiding scintillator. Optimizing the electrostatics of the QD layered structure with p-type modulation doping resulted in QD photoluminescence (PL) efficiency as high as 60% at room temperature. Analysis of attenuation of the QD waveguide showed surface scattering predominated over the first 2-3 mm of light propagation and low (~1 cm-1) self-absorption was more significant at longer distances, after the after the decay of high order modes (high angle light rays). Responses to 5.5 MeV alpha particles from the integrated photodiode on top of the QD scintillator/waveguide (QD/WG) show an extremely fast (300 ps) decay constant, and a 70 ps time resolution (limited by circuit noise and bandwidth) with a collection efficiency of 17000 photons per 1 MeV of deposited energy.
关键词： InAs Quantum Dots,GaAs waveguides,ultra-fast scintillators,alpha particle response,photoluminescence
更新于2025-09-12 10:27:22
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High-speed x-ray imaging system for the investigation of laser welding processes
摘要： A high-speed x-ray imaging system was built to investigate the fundamentals of laser material processing, such as laser welding. The system allows visualizing and analyzing the laser-induced process dynamics occurring also inside optically nontransparent workpieces. The details of the setup are presented together with the resulting performance with regard to edge sharpness, contrast, contrast transfer, and spatial as well as temporal noise. For voids with a depth (in respect to the x-ray radiation) of 100–500 μm, which is a typical range for focal diameters used in laser beam welding, a maximum contrast of 3%–19%, respectively, can be achieved. Due to the edge blurring, caused by the imaging system, the contrast is further decreased by 20% for voids with a lateral size of 100 μm and less than 10% for voids with a lateral size of 500 μm, when a magnification of 5.4 is used. The image intensifier, needed to increase the number of photons to saturate the camera, induces a noise floor of +15% in respect to the mean gray value and results in a maximum achievable signal to noise ratio for a 100 μm step of 1.2.
关键词： optical devices,x-ray imaging,materials synthesis and processing,scintillators,welding,electronic noise,vacuum tubes,noise floor,covariance and correlation,lasers
更新于2025-09-12 10:27:22