Study of the energy response of high pressure ionization chamber for high energy gamma-ray

The energy response calibration of the commonly used high pressure ionization chamber is very difficult to obtain when the gamma-ray energy is more than 3 MeV.In order to get the calibration of the higher part of the high pressure ionization chamber,we use the Fluka Monte Carlo program to perfclrm the energy response in both the spherical and the cylindrical high pressure ionization chamber which are full of argon gas.The results compared with prior study when the gamma-ray energy is less than 1.25 MeV.Our result of Monte Carlo calculation shows agreement with those obtained by measurement within the uncertainty of the respective methods.The calculation of this study is significant for the high pressure ionization chamber to measure the high energy gamma-ray.     

能量响应平坦的康普顿探测器设计

以开展能量响应平坦的真空康普顿探测器为目的,采用厚薄材料叠加补偿设计思想,使用蒙特卡罗方法,对真空康普顿探测器的灵敏度能量响应进行了优化设计。优化的探测器系统采用0.01,1.00 mm厚Au叠加的发射极,3 mm厚Fe前窗以及3 mm挡铅。在f40 mm准直下,实现了在0.4~7.0 MeV 能区内,探测器本征灵敏度极值变化小于10.7%。该能量响应平坦性优于当前各种常见的探测器。     

利用252 Cf快裂变室测量BC501A液闪探测器的相对探测效率和响应函数

本文利用²⁵²Cf快裂变室和多参数数据采集系统,逐事例的同时记录了自发裂变中子和瞬发伽马的飞行时间(TOF),脉冲形状甄别(PSD)和反冲能量(RE,裂变中子是通过测量反冲质子;瞬发伽马是通过测量康普顿反冲电子)三维信息.详细介绍了通过离线数据分析完全扣除三维信息中的伽马事例贡献,以获得Φ50.8 mm×50.8 mm的BC501A液闪探测器的相对探测效率和响应函数的方法.在不通过探测器响应函数进行数据转换的条件下,利用中子的能量直接确定了中子的有效测量阈值.得到的中子 关键词： 252Cf快裂变室')" href="#">²⁵²Cf快裂变室 BC501A液闪探测器 相对探测效率 响应函数     

Investigation of NaI(Tl)-Crystal Having Anomalous Inhomogeneity of Light Yield Spatial Distribution

An experiment with a layer-by-layer irradiation of the large volume NaI(Tl)-crystal has been performed. The inhomogeneity of the light yield spatial distribution along the crystal’s axis was revealed. A new method of accounting for the revealed inhomogeneity in the processing of the gamma-ray spectra registered using a crystal with nonuniform response is proposed. This method is quite universal: the conventional stages of the detector investigation (the calibration with standard gamma-ray sources and the inhomogeneity estimation using a layer-by-layer irradiation) are complemented by another one stage with computing of the absorbed energy distribution using Monte Carlo simulation. Finally, based on the results of these stages, the combined broadening function is formed for calculation of the response function.     

Response of CaSO4:Dy phosphor based TLD badge system to high energy electron beams from medical linear accelerator and estimation of whole body dose and skin dose

Response of thermoluminescent dosimeter (TLD) badge based on CaSO₄:Dy phosphor to high energy electron beams from medical linear accelerators was simulated using FLUKA Monte Carlo code and experimentally verified. This study was carried out in order to determine the response of TL discs under different filter regions of the TLD badge and their ratios under different irradiation conditions in the energy range 6–20 MeV of high energy electron beams. It was found that the response of TL disc under metal filters of the TLD badge (D1) is always higher than the response of the TL discs under Polystyrene filter (D2) and open window (D3) and its response was found to decrease with increase in the energy of the electron beam. Estimation of whole body dose and skin dose including its error was carried out as an extension of the present study in case of accidental exposure of radiation worker to high energy electron beam.     

Monte Carlo simulation of exposure factor

In this paper, we simulate the exposure factor by a simple model of a free-air ionization chamber with the Monte Carlo programme Geant4. Special emphasis is placed on the discussion of the exposure factor related to parameters of the chamber model. The reason for the variation in exposure factor with incident ray energy is also analysed in terms of reaction cross section for different types of reactions. The obtained results indicate that our simulation is accurate in the calculation of the exposure factor and can serve as a reference in designing air ionization chambers.     

非全裸碳离子与氦原子碰撞过程中的多重电离研究

采用飞行时间符合技术测得１．５—７．５ＭｅＶ非全裸碳离子轰击氦原子，引起氦原子双重电离与单重电离的相对截面比。对碰撞过程进行多体经典轨道蒙特卡罗模拟，得到相应的Ｏｌｓｏｎ—Ｓｃｈｌａｃｈｔｅｒ曲线，结合本实验结果，给出非全裸碳离子引起氦原子双重电离和单重电离的绝对截面，并进行了讨论。     

Comparison of thermoluminescence energy response of optical fiber subject to photon irradiation between Monte Carlo simulation and experiments

This study is focused on energy response of Ge-doped silicon dioxide optical fiber subjected to photon irradiation. The TL responses for photon energies, ranging from 20 keV to 20MeV, were investigated as energy absorbed in the TL materials of Ge-doped silicon dioxide optical fiber. The simulation was performed using Monte Carlo N-particle transport code version 5 (MCNP5). The input parameters included in this study are source information, geometry specification, material information and tallies F6. Comparisons of energy response were done between simulation and previous results of experiments. A flat response can only be seen in the energy range of 200 keV to 10 MeV.     

Study of a sealed high gas pressure THGEM detector and response of alpha particle spectra

A sealed high gas pressure detector working in pure argon is assembled.It consists of a 5 cm x 5 cm PCB THGEM(THick Gaseous Electron Multiplier).The detector structure and experimental setup are described.The performance under high pressure(2 atm) is examined,selecting optimal voltages for the ionization region and induction region.The dependence of the shape of alpha particle spectra measured with relative gas gain on gas pressure(1.3-2.0 atm) has been studied.Eight data sets of relative gas gain versus working voltage of THGEM,expressed by weighting field E/P,are normalized,consistent with theory.The results show that the air tightness of the chamber is good,measured by a sensitive barometer and checked with gas gain.The experimental results are compared with Monte Carlo simulation of energy deposition without gas gain involved.     

Determining the energy dependence of a calibration coefficient K_{Q,Q_0 } for a thimble-ionization chamber using computer modeling

The energy dependence of a thimble-chamber calibration coefficient is modeled in this work according to beam quality using the Monte Carlo method. The maximums of the deviations were observed within the range of photon energies that correspond to the giant dipole resonance for light elements. The deviations may reach 10% at photon energies of up to 25 MeV.     

井型高纯锗探测器体源样品无源效率刻度

采用蒙特卡罗程序MCNP建立物理模型,对井型高纯锗探测器的效率进行虚拟刻度。模拟计算在密度为0.4,1.2 gcm-3的6种不同成分环境样品中,探测器对射线的探测效率,当能量高于0.10 MeV时,体源样品的探测效率主要与样品密度、射线能量相关。以土壤、水和植物油样品为代表,结合所选取的函数模型,确定了密度范围0.1~1.6 gcm-3的固体源、密度1.0 gcm-3的水溶液和密度0.92 gcm-3的油溶液体源的效率函数及参数。实验采用标准源,对探测效率模拟结果进行了验证,探测效率的模拟值与实验值符合较好,二者误差均在3%以内。说明MCNP程序可以较为准确地模拟计算井型高纯锗探测器对射线的探测效率,验证了该无源效率刻度方法的准确性和可行性。     

Optimization of the energy response of radiographic films by Monte Carlo method

In the present work a simple model for calculation of the energy response of radiographic films was introduced. According to the model the energy response of a radiographic film is directly proportional to the optical density on the film and thus to the number of developed grains in the emulsion. The model was simulated by Monte Carlo method using MCNP code and the relative energy response of Kodak type 2 film under a few filters of A.E.R.E./R.P.S. film badge was calculated. The simulated responses were in agreement with the experimental data in the region of 30 keV–1.5 MeV. In the next stage a multi-element filter was simulated to optimize the energy response in the above energies. The energy response varied by 25% between 40 keV and 1.5 MeV. So the dose received by the film is equivalent to the desired true dose and there would be no need to the correction factors.     

高能质子在散裂靶中的能量沉积计算与实验验证

高能质子在散裂靶中的能量沉积是散裂靶中子学研究的重要内容之一,准确掌握高能质子在散裂靶中引起的能量沉积分布与瞬态变化是开展散裂靶热工流体设计的重要前提.本文采用MCNPX,PHITS与FLUKA三种蒙特卡罗模拟程序,计算并比较了高能质子入射重金属铅靶、钨靶的能量沉积分布及不同粒子对总能量沉积的占比贡献;针对高能质子入射金属钨靶的能量沉积实验数据空白,采用热释光探测器阵列测量了250 MeV质子束入射厚钨靶的能量沉积分布,实验结果表明蒙特卡罗模拟程序在散裂靶中能量沉积的计算结果具有较高的可靠性.     

阳极杆箍缩二极管产生X射线能谱的模拟计算

采用粒子模拟,得到了阳极杆箍缩二极管阳极钨针上电子的空间分布和入射角分布,分析二极管工作状态得到了电子的能量分布.在此基础上建立阳极杆箍缩二极管的蒙特卡罗模型,模拟得到了阳极杆箍缩二极管的辐射能谱和X射线的平均能量,并与实验结果进行了比较.结果表明:09006炮光子平均能量为0.441 MeV,计算该能谱射线经过不同厚度铅衰减片后的剂量衰减情况,与叠片法PIN探测器所测的实验数据基本一致. 关键词： 阳极杆箍缩二极管 粒子模拟 蒙特卡罗方法 X射线能谱     

LS301快中子探测器的效率刻度

主要介绍了利用252Cf标准裂变中子能谱刻度快脉冲LS301型液闪中子探测器的探测效率的实验方法和结果, 简要介绍了实验数据的处理过程, 得到了阈值分别为0.5, 0.7, 1.0和1.6 MeV, 以及中子能量在10 MeV以下的探测器效率, 并对测量结果进行了误差分析。同时为了检验实验结果的准确性, 将实验结果与理论计算结果进行比较, 两者在不确定度范围内符合得很好。Neutron detection efficiency of LS301 fast neutron detector was calibrated by measuring the neutron energy spectrum of 252Cf source, which has a standard fission neutron spectrum. A low mass, fast ionization chamber is used as the fission fragments detector in the time of flight(TOF) spectrometer and afforded the start signal of neutron flight. The stop signal was offered by the anode of LS301. A measured TOF spectrum was turned to the neutron energy spectrum which will be compared with the standard one. Consequently, the fast neutron detection efficiency of LS301 was obtained. Calibration procedures of experimental and data processing was given. Relative detection efficiencies were obtained separately for threshold settings of 0.5, 0.7, 1.0 and 1.6 MeV for neutron energies under 10 MeV. Experimental results accorded with theoretical efficiency curves which were calculated with the Monte Carlo code NEFF50.     

Measurement of neutron-induced proton-production energy spectra with NE213 scintillator

Many benchmark data are required for the improvement of theoretical model implemented in a Monte Carlo code for particle transport. To acquire the benchmark data, we measured energy spectra of protons emitted from graphite, aluminum, and iron targets bombarded with continuous-energy neutrons, which enable simultaneous measurements at the incident energies from 100 to 600 MeV at a time. The neutron flux incident on the target was measured with a ²³⁸U fission ionization chamber. Protons emitted from the target were measured with three ΔE–E detectors consisting of a thin NE102A scintillator and a thick NE213 liquid scintillator. In the analysis, the pulse shape discrimination of the NE213 scintillator enable us to distinguish events for a charged particle stopping in the scintillator from events for a charged particle penetrating the scintillator. Experimental results were compared with calculations by the PHITS code coupled with the JENDL-HE file, the Bertini model implemented in the PHITS code, and the PEANUT model in the FLUKA code.     

Thermoluminescence energy response of TLD-100 subjected to photon irradiation using Monte Carlo N-particle transport code version 5

Useful TL properties of TLD-100 that is an excellent candidate for using in TL dosimetry of ionizing radiation are demonstrated. This study is focused on response of TLD-100 subjected to photon irradiation. The thermoluminescence (TL) response of TLD-100 subject to various photon energy, ranging from 20 keV to 6 MeV, was investigated as energy absorbed in the TL material using Monte Carlo N-Particle transport code version 5 (MCNP5). The input parameters included in this study are experimental geometry specification, source information, material information, and tallies. Tally F6 is used in this simulation. The results from MCNP5 simulation show good agreement with previous experimental data. However, the data obtained from the simulation are greater than the experimental data especially in lower energy ranges.     

非弹性核反应对质子束能量沉积的影响

提出了一种比较精确且又省时的质子穿透的解析算法,并给出了考虑核反应后50—250MeV质子在水中的能量沉积,与Monte-Carlo方法的结果进行了比较.结果表明:1)非弹性核反应对质子的能量沉积有明显的影响,特别是对较高能量的质子束入射情况;2)该方法计算效率比Monte Carlo方法高百倍以上.因此,本文方法解决了质子能量沉积计算中效率和精度之间的矛盾,有可能在质子束放射治疗中得到实际应用. 关键词： 质子能量沉积 核反应 截面     

Geant4 simulation of proton-induced single event upset in three-dimensional die-stacked SRAM device

Geant4 Monte Carlo simulation results of the single event upset(SEU) induced by protons with energy ranging from0.3 MeV to 1 GeV are reported.The SEU cross section for planar and three-dimensional(3 D) die-stacked SRAM are calculated.The results show that the SEU cross sections of the planar device and the 3 D device are different from each other under low energy proton direct ionization mechanism,but almost the same for the high energy proton.Besides,the multi-bit upset(MBU) ratio and pattern are presented and analyzed.The results indicate that the MBU ratio of the 3 D die-stacked device is higher than that of the planar device,and the MBU patterns are more complicated.Finally,the onorbit upset rate for the 3 D die-stacked device and the planar device are calculated by SPACE RADIATION software.The calculation results indicate that no matter what the orbital parameters and shielding conditions are,the on-orbit upset rate of planar device is higher than that of 3 D die-stacked device.     

氘-氚中子源辐照旋转靶剂量演化模拟计算

首次将蒙特卡罗自动建模系统(MCAM)、蒙特卡罗粒子输运程序(MCNP)及自主研发的活化程序BURNDOT相结合,实现了中子输运、材料活化、光子输运模拟计算的耦合。对14MeV氘-氚(D-T)中子源旋转靶室剂量演化分析,计算了氘-氚中子源辐照旋转靶室的瞬发中子、γ三维辐射剂量场分布及连续辐照8小时后缓发γ剂量变化情况,并考察了材质、栅元、主要核素对缓发γ剂量贡献的影响,得到了旋转靶的剂量时空演化规律,把计算结果与欧洲活化程序FISPACT-2007进行了对比。