采用电离室测定重离子束的Bragg峰位

从探索定点定位诱变要求出发，提出了重离子束Ｂｒａｇｇ峰可作为一个有用手段，阐述了测量重离子束Ｂｒａｇｇ峰的原理和实验装置，采用一对电离室测定初始能量为５０ＭｅＶ／ｕ左右＾１４Ｎ＾７＋离子束在物质密度归一到小麦材料后的Ｂｒａｇｇ峰位。最终得到峰位深度约为４．８５ｎｍ，离子束的最大射程为５．５ｍｍ左右。     

位置灵敏布喇格探测器的研制

本文介绍我们研制的一台用于重离子鉴别的位置灵敏布喇格探测器，它是在普通布喇格探测器的Ｆｒｉｓｃｈ栅和阳极之间加进一个辅助栅－Ｐ栅，位置信号从Ｐ栅上提取，位置由丝确定，用电荷分除法来进行位置读出。其性能用＾２５２Ｃｆ α源进行了测试，得到位置分辨△ｘ＜９ｍｍ。     

组织等效空腔电离室设计与饱和特性研究

MOS场效应管与空腔电离室两种技术结合,形成一种用于个人核辐射剂量监测的新型探测器一直接电荷存贮（Direct Ion Storage,简称DIS）探测器。本文在介绍该探测器原理基础上,从壁材料、气体成分、腔体形状和尺寸、壁厚度以及绝缘材料等角度,设计与研制组织等效空腔电离室。利用^60C07辐射源和中能X射线,测试了电离室饱和特性,很好的满足DIS探测器对电离室饱和特性的要求。     

用于n/γ混合场测量的涂硼电离室研制

研制了一种能同时测量混合场中γ和中子注量率的涂硼电离室,并实验测试了其性能。涂硼电离室由两个大小和结构一致的腔室组成：1个仅对γ灵敏,另1个对γ与中子均灵敏。用强度为2.7×10⁷ s^-1 的Am-Be源测得电离室的中子灵敏度达9.2×10^-16 A/(cm^-2•s^-1),在剂量率为5.24 μGy/h的¹³⁷Cs γ场中,电离室的γ灵敏度达7.36×10^-16 A/(MeV•cm^-2•s^-1)。涂硼电离室I-V曲线坪长为600 V,坪斜小于4%/100 V,在工作电压为-400 V时,其γ补偿修正系数<5%,可用于核设施周围的混合场监测。     

一台用于IMP重离子治癌线上的电离室

介绍一种用于中国科学院近代物理研究所(IMP)重离子肿瘤治疗线上、于纵向场常压下工作的气体电离室,其灵敏面积为250 mm×250 mm,极间距离为10 mm,电离室工作气体为P10,在85kPa下流气式工作.用75 MeV/u 12C离子入射,测量了电离室的坪曲线.发现电离室工作坪区900-3000 V,12C的Bragg峰位于13.73 mm,峰的极大值半高宽(FWHM)为0.19 mm.     

CSNS束流损失监控(BLM)系统电离室的改进

报道了中国散裂中子源工程(CSNS)和强流质子加速器(PA)柬流损失监控(BLM)系统的电离室的改进.对改进后的电离室测量得到,电离室有良好的坪特性(坪长≥2 000 V),测量的辐照剂量范围到3.6×10 5rad/h,高压加到3500 V仍能稳定工作.测量的结果表明电离室探头性能已能满足CSNS和PA对束流损失监控...     

11 宽量程环境γ辐射连续监测技术的研究

为满足核设施环境连续监测中常规和事故监测的需要，选用白行研制的高气压充氩电离室，开展10～109nGy／h8个量级的宽量程环境γ辐射连续监测技术的研究。在国防科工委计量一级站完成了高气压充氩电离室饱和特性曲线及非饱和特性曲线的实验测量，建立了高气压充氩电离室八个量级宽量程的输出电流与γ空气吸收剂量率的关系。     

一台用于重离子鉴别的Bragg曲线谱仪

本文介绍制作的一台用于重离子鉴别的Bragg曲线谱仪。它是一种电场平行于入射粒子方向的全阻止型电离室。其性能用ThC-C’α源和~(252)Cf源进行了测试。对8.785MeV α粒子(ThC’源)能量分辨好于1％,电荷分辨Z/ΔZ=50。     

测厚电离室研制

一、引言放射性测厚仪中使用的传感器是具有高稳定性和高可靠性的电离室,测厚常用的电离室有空气式β电离室,充气式β,γ和X射线电离室等。它们分别可以测量工业上常见的各种厚度的纸张、塑料薄膜、有色金属及铝、钢等板材的厚度。我们主要研制了具有典型应用价值的三种类型的测厚用电离室,它们分别是dLS-X-1型的高效率X射线电离室,dLS-β-1型空气式β电离室,dLS-β-2型充Ar式β电离室。在研制工作中,对三种类型电离室的制作工艺及性能进行了研究。     

确定高气压电离室自身本底的一种方法

一、引言任何测定低水平环境辐射的仪器,仪器自身的放射性本底是需要认真考虑的问题之一,因为在低照射量率情况下,它直接影响仪器读数的准确度。就电离室而言,电离室内壁材料高原子序数杂质的α发射是电离室自身本底的主要来源。早期的工作就已注意到电离室材料的放射性污染。减小常压电离室室壁α发射影响的主要措施有:1)增大电离室体积,2)电离室内部改充负电性气体     

大张角的Bragg探测器

本文介绍的大张角Bragg探测器的张角为±8°的锥形腔体。在整个探测器的灵敏区内,电场是均匀场。用ThC-ThC′源的α粒子(8.785MeV)测试,其能量分辨率为0.8％,电荷数分辨率为1.8％。     

Silicon Surface Barrier Detector

A method has been established for producing silicon surface barrier detectors having an energy resolution of 0.7% for 5.3 MeV α particles, and which are stable for long periods of time. The fabricated detector has been proved to possess a depletion layer as thick as 200 μ and a surface layer with energy loss less than 15 keV for 5.3 MeV α particles. The stability of the detector was also tested and it was found to be stable for at least 2–3 months.     

Measurements of the W values in argon,nitrogen, and methane for 0.93 to 5.3 MeV alpha particles

The W values in argon, nitrogen and methane have been measured for alpha particles with energies from 0.93 MeV to 5.3 MeV by gridded ionization chambers. The energies of alpha particles emitted from ²¹⁰Po (5.3 MeV) were reduced by passage through Al foils and Mylar films of various thicknesses. The mean energies of these “reduced” alpha particles were determined using a silicon detector calibrated with five natural alpha sources. The W values for the gases and energies studied are obtained by assuming a W value of 26.31 eV in pure argon for 5.3 MeV alpha particles. The W value in argon is found to be slightly dependent on the energy of alpha particles. In nitrogen and methane, the W values for an alpha energy of 0.93 MeV are about 5 and 8% larger, respectively, than for an alpha energy of 5.3 MeV.     

A mathematical method to calculate efficiency of BF3 detectors

In order to calculate absolute efficiency of the BF3 detector, MCNP/4C code is applied to calculate rela-tive efficiency of the BF3 detector first, and then absolute efficiency is figured out through mathematical techniques. Finally an energy response curve of the BF3 detector for 1~20 MeV neutrons is derived. It turns out that efficiency of BF3 detector are relatively uniform for 2~16 MeV neutrons.     

Anisotropy of Scintillation Response of Anthracene to Neutron Generated Recoil Protons and Carbon Ions

The directional anisotropy in the scintillation response of an anthracene crystal to heavy charged particles was investigated. Energetic carbon and hydrogen ions were produced internally by scattering fast neutrons from the constituent nuclei. By use of a two detector coincidence system, the scintillations due to monoenergetic ions recoiling in a particular direction were selected and analyzed. The energies of the ions ranged from 2 to 3.5 MeV for the carbon recoils and from .9 to 7.3 MeV for the hydrogen recoils. Even though there was a wide variation in the average specific energy loss of the heavy charged particles considered, the magnitude of the anisotropy only varied between 39% for the carbon recoils and 20% for the 7.3 MeV hydrogen recoils. The measured hydrogen ion response in a particular direction as a function of energy was found to be approximately described by the formula suggested by Birks, dL/dE = (1 + kBdE/dx)-1, with kB being directionally dependent. The directional carbon ion response appeared to be a linear function of energy over the energy range investigated.     

Annular gas ionization detector for low energy heavy ion backscattering spectrometry

A gas ionization chamber for use in backscattering spectrometry has been built. It has the shape of a hollow cylinder and can be placed in-line with the incident ion beam. The entrance window for detected particles is composed of a circular array of silicon nitride membranes. A low noise preamplifier with cooled FET is used for charge amplification. The detector resolution has been measured for a variety of ions in the mass range from He to Si and for energies between 0.5 and 8 MeV. The energy resolution of the ionization chamber surpasses the one of a state-of-the-art silicon charged particle detector for all ions heavier than Li. For Si ions the improvement in resolution is more than a factor of 2. The device does not suffer from any radiation damage. For He particles around 1 MeV the resolution is between 13 and 16 keV (FWHM). Therefore the new detector is not only well suited for heavy ion backscattering spectrometry but can also be applied for standard He RBS, allowing the use of a single detector for all types of projectiles in a wide energy range.     

用次级束流对硅望远镜的时间和能量定标

利用９５ＭｅＶ／ｕ的１６Ｏ束产生的次级束流对半导体硅探测器进行了时间和能量定标。实验结果表明，由于次级束流提供的次级粒子种类多，飞行距离长，因此，能给探测器带来非常精确的定标。     

8×8单元CsI(Tl)探测阵列研制

描述了1个8×8单元CsI(Tl)探测阵列的结构和工作原理。探测阵列的每个单元是由1块前表面21 mm×21 mm、后表面23.1 mm×23.1 mm、高50 mm的CsI(Tl)棱台、1块光导和光电倍增管组成。在兰州放射性次级束流线(RIBLL)上对探测阵列进行测试,得到探测阵列对30 MeV质子的能量分辨可达2.7%,对170 MeV7Be可达1.5%,可很好地用于放射性束物理实验中带电粒子的鉴别。     

The Plastic Ball ? a Multi-Detector, Large Solid Angle Spectrometer with Charged Particle Identification for the Bevalac

For the study of central relativistic nuclear heavy ion collisions, which are characterized by the emission of a large number of particles, one needs a detector which covers a large solid angle ? 4? if possible ? and which is capable of identifying charged particles. The high multiplicity requires a large number of detectors, and the need for charged-particle identification requires a measurement of the energy loss, and the total energy for each particle detected. The spectrometer consists of 815 detector modules, which cover 94% of 4?. The geometry of these modules has been taken from the Stanford crystal ball detector for ?-rays ? with minor modifications. This geometry is suited for the high multiplicities of particles emitted in relativistic heavy ion collisions. The dimension of the individual elements have been chosen to stop 240 MeV protons. Above this energy reaction losses start to dominate, so that the light output of a scintillator would no longer be a true indication of the energy. Out of 100 charged particles, 94 will hit the Plastic Ball, 87 will fire a detector element, and 80 will be identified uniquely. For the individual detector modules we have used the "Phoswich" idea, by gluing a 4 mm thick CaF2 scintillator to a 35 cm thick plastic scintillator (NE114) with the shape of a truncated pyramid, which is viewed by one photomultiplier tube (PM2202B).     

充气飞行时间探测方法分析

本工作涉及充气飞行时间探测器的工作原理和实验测量结果。在不同能量(64、48和33MeV)下，利用充气飞行时间探测方法对同量异位素³⁶S和³⁶Cl进行鉴别，并与用传统的ΔE－E方法在相同能量下的鉴别结果进行比较。实验结果表明，在入射能量较高（E_i＞40MeV）时，ΔE－E法的鉴别能力比充气飞行时间法的稍好些；在E_i＜40MeV时，充气飞行时间法的鉴别能力比ΔE－E法的好，入射能量为20～40MeV时，充气飞行时间法能明显将³⁶S和³⁶Cl区分出来。