Characteristics of plastic scintillator granules

Methods are described for measuring the absorption coefficient of the material, the absorption coefficient of a layer of granules, and the scintillation performance. The theory of light diffusion in a scattering medium is used and is compared with experiment.We are indebted to A. R. Daich and L. E. Pargamanik for a discussion.     

HZE dosimetry in space using plastic track detectors

Plastic nuclear track detectors were used to measure the contribution of High charge Z and energy E (HZE) particles to the radiation exposure of manned space missions. Results from numerous space missions in the orbit planned for the International Space Station are compared. The measurements cover the declining phase of the last solar cycle during the past 7 years and various shielding conditions inside the US Space Shuttle and the Russian MIR-station.     

Calibration of different plastic track detectors using accelerated heavy ions

Measurements of the dependence of track etch rate on the energy-loss of different ions have been presented. In this method, ₁₈ ⁴⁰ Ar, ₁₀ ²² Ne, ₈ ¹⁶ O and ₆ ¹² C-ions of different energies are used as energetic heavy ions for track formation in the detectors. The bulk etch rate and track etch rate are measured for different temperatures and hence the activation energies are determined. The variation ofV =V _t /V _b along the trajectory of the track has been shown for different temperatures. The maximum etched track length is compared with the theoretical range as well as with the range reported earlier. The experimental results indicate the absence of a well-defined threshold in the plastics studied.     

Temperature dependence of the plastic scintillator detector for DAMPE

The Plastic Scintillator Detector(PSD) is one of the main sub-detectors in the DArk Matter Particle Explorer(DAMPE) project. It will be operated over a large temperature range from -10 to 30, so the temperature effect of the whole detection system should be studied in detail. The temperature dependence of the PSD system is mainly contributed by the three parts: the plastic scintillator bar, the photomultiplier tube(PMT), and the Front End Electronics(FEE). These three parts have been studied in detail and the contribution of each part has been obtained and discussed. The temperature coefficient of the PMT is -0.320(±0.033)%/, and the coefficient of the plastic scintillator bar is -0.036(±0.038)%/. This result means that after subtracting the FEE pedestal, the variation of the signal amplitude of the PMT-scintillator system due to temperature mainly comes from the PMT,and the plastic scintillator bar is not sensitive to temperature over the operating range. Since the temperature effect cannot be ignored, the temperature dependence of the whole PSD has been also studied and a correction has been made to minimize this effect. The correction result shows that the effect of temperature on the signal amplitude of the PSD system can be suppressed.     

In-phantom dose verification of prostate IMRT and VMAT deliveries using plastic scintillation detectors

The goal of this work was to demonstrate the feasibility of using a plastic scintillation detector (PSD) incorporated into a prostate immobilization device to verify doses in vivo delivered during intensity-modulated radiation therapy (IMRT) and volumetric modulated-arc therapy (VMAT) for prostate cancer. The treatment plans for both modalities had been developed for a patient undergoing prostate radiation therapy. First, a study was performed to test the dependence, if any, of PSD accuracy on the number and type of calibration conditions. This study included PSD measurements of each treatment plan being delivered under quality assurance (QA) conditions using a rigid QA phantom. PSD results obtained under these conditions were compared to ionization chamber measurements. After an optimal set of calibration factors had been found, the PSD was combined with a commercial endorectal balloon used for rectal distension and prostate immobilization during external beam radiotherapy. This PSD-enhanced endorectal balloon was placed inside of a deformable anthropomorphic phantom designed to simulate male pelvic anatomy. PSD results obtained under these so-called “simulated treatment conditions” were compared to doses calculated by the treatment planning system (TPS). With the PSD still inserted in the pelvic phantom, each plan was delivered once again after applying a shift of 1 cm anterior to the original isocenter to simulate a treatment setup error.The mean total accumulated dose measured using the PSD differed the TPS-calculated doses by less than 1% for both treatment modalities simulated treatment conditions using the pelvic phantom. When the isocenter was shifted, the PSD results differed from the TPS calculations of mean dose by 1.2% (for IMRT) and 10.1% (for VMAT); in both cases, the doses were within the dose range calculated over the detector volume for these regions of steep dose gradient. Our results suggest that the system could benefit prostate cancer patient treatment by providing accurate in vivo dose reports during treatment and verify in real-time whether treatments are being delivered according to the prescribed plan.     

Using plastic track detectors to solve radiation safety problems at nuclear reactor facilities

Three options of the method to determine microconcentrations of fissile materials in water solutions are developed. They utilize plastic track detectors to measure concentrations. The options are as follows a “wet” method, “thin-layer inorganic sorbent-plastic track detectors”, and a method of selective extraction and coprecipitation. These methods are used to check up fuel cladding integrity at the research reactor IVV-2M and liquid radioactive waste contamination by uranium and plutonium at the Beloyarskaya Nuclear Power Plant (BNPP).     

Simultaneous measurement of radon, radon progeny and thoron concentrations using Makrofol-DE detectors

In this study we describe the set-up of a new passive integrating system to measure simultaneously ²²²Rn, ²²²Rn progeny (²¹⁸Po and ²¹⁴Po) and ²²⁰Rn concentration indoors. It consists of four Makrofol-DE (polycarbonate) circular foils. Two are enclosed within two diffusion chambers—each one with a different filter membrane—to measure ²²²Rn and ²²²Rn+²²⁰Rn. The other two foils are kept in direct contact with air and are electrochemically etched at different conditions to obtain the ²²²Rn daughters. Theoretical sensitivities of each Makrofol-DE foil are calculated using Monte-Carlo technique. The calculations are performed taking into account: (1) the Bethe–Bloch's expression for the stopping power of heavy charged particles in a medium, (2) the properties and behaviour of ²²²Rn, ²²⁰Rn and their progeny in the open air and within the diffusion chamber and (3) the etching conditions used to visualise -particles tracks.     

A GUI tool for beta function measurement using MATLAB

The beta function measurement is used to detect the shift in the betatron tune as the strength of an individual quadrupole magnet is varied. A GUI (graphic user interface) tool for the beta function measurement is developed using the MATLAB program language in the Linux environment, which facilitates the commissioning of the Shanghai Synchrotron Radiation Facility (SSRF) storage ring. In this paper, we describe the design of the application and give some measuring results and discussions about the definition of the measurement. The program has been optimized to solve some restrictions of the AT tracking code. After the correction with LOCO (linear optics from closed orbits), the horizontal and the vertical root mean square values (rms values) can be reduced to 0.12 and 0.10.     

A GUI tool for beta function measurement using MATLAB

The beta function measurement is used to detect the shift in the betatron tune as the strength of an individual quadrupole magnet is varied. A GUI （graphic user interface） tool for the beta function measurement is developed using the MATLAB program language in the Linux environment, which facilitates the commissioning of the Shanghai Synchrotron Radiation Facility （SSRF） storage ring. In this paper, we describe the design of the application and give some measuring results and discussions about the definition of the measurement. The program has been optimized to solve some restrictions of the AT tracking code. After the correction with LOCO （linear optics from closed orbits）, the horizontal and the vertical root mean square values （rms values） can be reduced to 0.12 and 0.10.     

Uranium, radium and radon exhalation studies in some soil samples using plastic track detectors

Radium concentration and radon exhalation rate have been measured in soil samples collected from some areas belonging to upper Siwaliks of Kala Amb, Nahan and Morni Hills of Haryana and Himachal Pradesh states, India using LR-115 type II plastic track detectors. Uranium concentration has also been determined in these soil samples using fission track registration technique. Radium concentration has been found to vary from 5.30 to 31.71 Bq.kg⁻¹, whereas uranium concentration varies from 33.21 to 76.26 Bq.kg⁻¹. The radon exhalation rate in these samples varies from 216.87 to 1298.00 mBq.m⁻²hr⁻¹ (6.15 to 36.80 mBq.kg⁻¹.hr⁻¹). Most of the samples have uranium concentration above the worldwide average concentration of 35 Bq.kg⁻¹. A good correlation (R ² = 0.76) has been observed between uranium concentration and radon exhalation rate in soil. The values of uranium, radium and radon exhalation rate in soil are compared with that from the adjoining areas of Punjab.     

Monte Carlo sampling for gamma and beta detectors using a general purpose PC program

The main objective of this study is the computation of several parameters involved in gamma and beta environmental radiation measurements, such as detection efficiency, the attenuation coefficients, mass energy-transfer coefficients and mass energy-absorption coefficients for several materials. In order to accomplish these tasks we developed a PC program, based on a Monte Carlo simulation of radiation transport. This program (GES_MC Gamma-electron Efficiency Simulator) was written entirely in Java and was based on the EGSnrc (Electron Gamma Shower) source code. Although GES_MC was especially designed for the computation of the response function and peak efficiency for gamma detectors, it can also be used in various studies concerning photon or electron interactions with the matter in any cylindrical (RZ) geometry. Several aspects of photon and electron transport and the comparison of the program outputs with experimental data are also presented in this study.The main advantage of the Monte Carlo simulations presented in this paper is that any source and any detector can be properly sampled. In contrast with the Monte Carlo technique, for an accurate experimental result, the computation of detector efficiency for a large number of standard sources having various geometries and compositions is required (one standard source for each sample type).     

Response of triafol-TN plastic track detectors to238U-ions

Triafol-TN plastic detector foils have been irradiated with²³⁸U ions of energy 16.34 MeV/u and the tracks produced have been observed using the chemical etching technique. The bulk etch rate and track etch rate are determined under successive chemical etching. In our case, the validity of Arrhenius’s law is confirmed by the fact that the same value ofE _a obtained for these different concentrations, within experimental errors. The results show a linear correlation between the measured track etch rate along the track and the corresponding total energy loss rate and a threshold value of ～ 5.0 MeV/(mg/cm²) for track registration was obtained. The maximum etched track length of²³⁸U-ion in triafol-TN has been compared with the theoretically computed range.     

Energy measurement and fragment identification using digital signals from partially depleted Si detectors

In this work we devise a new method to study quark-anti-quark interactions beyond simple ladder-exchange that yield massless pions in the chiral limit. The method is based on the requirement to have a representation of the quark-gluon vertex that is explicitly given in terms of quark dressings functions. We outline a general procedure to generate the Bethe-Salpeter kernel for a given vertex representation. Our method allows not only the identification of the mesons' masses but also the extraction of their Bethe-Salpeter wave functions exposing their internal structure. We exemplify our method with vertex models that are of phenomenological interest.     

门控下InGaAs/InP单光子探测器用于符合测量的时域滤波特性研究

基于砷化镓/磷化铟雪崩光电二极管(InGaAs/InP APD)的半导体单光子探测器因工作在通信波段,且具有体积小、成本低、操作方便等优势,在实用化量子通信技术中发挥了重要作用.为尽可能避免暗计数和后脉冲对单光子探测的影响,InGaAs/InP单光子探测器广泛采用门控技术来快速触发和淬灭雪崩效应,有效门宽通常在纳秒量级.本文研究揭示了门控下单光子探测器可测量的最大符合时间宽度受限于门控脉冲的宽度,理论分析与实验结果良好拟合.该研究表明,门控下InGaAs/InP单光子探测器用于双光子符合测量具有显著的时域滤波特性,限制了其在基于双光子时间关联测量的量子信息技术中的应用.     

A study of time over threshold (TOT) technique for plastic scintillator counter

A new charge measurement method, time over threshold (TOT), has been used in some gas detectors lately. Here TOT is studied for TOF system, made of plastic scintillator counter, which can simplify the electronics of the system. The signal characteristics are measured and analyzed with a high quality oscilloscope, including noise, pedestal, signal amplitude, total charge, rise time and the correlation between them. The TOT and charge are related and can be fitted by some empirical formula. The charge measurement resolution by TOT is given and this will help the design of TOF electronics.     

Measurements of the light output functions of plastic scintillator using 9Be(d,n)10B reaction neutron source

The light output functions for protons of ST-401 and BC-408 plastic scintillators were measured using white neutron source produced by the 9Be(d,n)10B reaction at the HI-13 Tandem Accelerator at China Institute of Atomic Energy(CIAE).The LOFs of plastic scintillators for protons in the energy range of 0.516.5 MeV were obtained by the time-of-flight(TOF)technique and an iterative procedure.Two parameters(kB and C)were deduced by fitting the experimental data.     

A measurement system for alpha and beta surface emissionrate using MWPC

We have developed a large area multi-wire proportional counter (MWPC) as a standard for the measurement of alpha and beta surface emission rate at the Shanghai Institute of Measurement and Testing Technology (SIMT). To shorten the preparation time for chamber gas refilling, a self-designed gas control unit was adopted. Various characteristics of the system have been studied. The uncertainties were analysed. Three certified alpha plane sources (Am-241) and six certified beta plane sources (Tl-204 and Sr-90/Y-90) were measured by this system. The results show excellent agreement with the surface emission rate reported by the National Institute of Measuring, China (NIM) that E_n values of all measured sources are within ±1.     

Annealing of heavy ion tracks in cellulose nitrate plastic track detectors

The effect of heat treatment on the latent tracks in cellulose nitrate plastic track detectors has been studied. The bulk etch rate increases with annealing temperature while the track diameters of different ions in cellulose nitrate decrease with increase in annealing time and temperature. Experimental results show that for heavier ions higher temperatures are needed for their complete erasure. The track length and track etch rate are decreased by the application of heat. Experiments reveal that annealing reduces track density. The vertical tracks are more stable than the oblique tracks and require higher temperature for their complete erasure.