HIRFL在束γ实验终端BGO反康谱仪性能

引言随着兰州重离子加速器的建成出束,将有八个实验终端随之投入使用。其中在束γ终端是一台主要用于核谱学研究的大型设备。它由置于水平面内的六套带BGO反康普顿屏蔽的高纯Ge探测器和一个由十四块BGO六棱柱探测元构成的小型晶体球组成。增加这种六棱柱形状的BGO元个数,便能使小型晶体球很容易地扩建成中型和大型晶体球。

重离子辐照效应检测系统的研制

为进行静态随机存储器芯片和可编程外围接口芯片的单粒子效应研究,研发了重离子辐照效应检测系统。系统特点是人机界面友好,操作方便、直观,实现了可靠的控制与数据采集。在HI 13串列加速器上,利用此系统对静态随机存储器HM1 65642(SRAM8K×8bit)和可编程外围接口电路ID82C55ACl、56Fe、79的单粒子翻转效应和单粒子锁定效应成功地进行了试验研究,完成两种器件5种离子16O、35Br、127I及反冲197Au的单粒子效应的测量。

空间带电粒子谱仪性能测试及能量刻度

采用金硅面垒探测器及CsI(Tl)探测器设计制作了一套△E-E型探测空间粒子的望远镜系统,利用α粒子、质子、氧离子、铁离子4种粒子对该望远镜系统和电子学系统进行性能测试和能量刻度。电子学的增益系统分为三挡,分别为1.0、1/3和1/12.75。实验结果表明:对于α粒子,采用1/3挡,在△E_1和△E_2探测器中每道能量分别是H_1=0.107 MeV和H_2=0.123 MeV。对质子能量的刻度,采用1挡,每道能量H值为0.016 7 MeV,这个H值几乎不随能量变化,在CsI探测器中,每道能量H为1.047 MeV。对氧离子的能量刻度采用1/12.75的挡别,刻度出每道能量是1.11 MeV。在探测器中,沉积能量高于50 MeV,电子学系统进入饱和状态。对铁离子的标定结果与氧离子的结果相同。

中国质子、重离子放疗装置建设现状

质子和重离子的质量比电子和光子重得多，经同步加速器加速后，获得足够动能的高能质子和重离子束，其辐射剂量可更多地沉积到人体深部的恶性肿瘤内，其临床疗效肯定。据美国能源部资助（合同号DE—AC02—05CH11231）的一项关于质子、重离子治疗的调研报告，纵观全球专用质子、

Reconstruction of fission events in heavy ion reactions with the compact spectrometer for heavy ion experiment

We report a reconstruction method for fast-fission events in 25 MeV/u^(86)Kr +^(208)Pb reactions at the Compact Spectrometer for Heavy Ion Experiment(CSHINE). The fission fragments(FFs) are measured using three large-area parallel-plate avalanche counters, which can deliver the position and arrival timing information of the fragments. The start timing information is provided by the radio frequency of the cyclotron. Fission events were reconstructed using the velocities of the two FFs. The broadening of both the velocity distribution and azimuthal difference of the FFs decreases with the folding angle, in accordance with the picture that fast fission occurs. The anisotropic angular distribution of the fission axis also consistently reveals the dynamic features of fission events.

Lattice damage in InGaN induced by swift heavy ion irradiation

The microstructural responses of In_(0.32)Ga_(0.68)N and In_(0.9)Ga_(0.1)N films to 2.25 GeV Xe ion irradiation have been investigated using x-ray diffraction,Raman scattering,ion channeling and transmission electron microscopy.It was found that the In-rich In_(0.9)Ga_(0.1)N is more susceptible to irradiation than the Ga-rich In_(0.32)Ga_(0.68)N.Xe ion irradiation with a fluence of 7×10^(11)ions·cm^(-2)leads to little damage in In_(0.32)Ga_(0.68)N but an obvious lattice expansion in In_(0.9)Ga_(0.1)N.The level of lattice disorder in In_(0.9)Ga_(0.1)N increases after irradiation,due to the huge electronic energy deposition of the incident Xe ions.However,no Xe ion tracks were observed to be formed,which is attributed to the very high velocity of 2.25 Ge V Xe ions.Point defects and/or small defect clusters are probably the dominant defect type in Xe-irradiated In_(0.9)Ga_(0.1)N.

Monte Carlo study of the neutron ambient dose equivalent at the heavy ion medical machine in Wuwei

The use of carbon-ion radiotherapy(CIRT)is gradually increasing.Owing to the generation of high-energy secondary neutrons during CIRT,its use presents new challenges in radiation protection.Thus,secondary neutron dose distributions must be explored and evaluated under clinical scenarios based on different treatment configurations.However,neutron dose and energy spectrum measurements are often difficult.This can be primarily attributed to the inherent limitations of most neutron detectors,such as their unsuitability for spectral measurements and inaccurate responses to neutrons with energies above 20 MeV.Numerical calculation methods based on probabilistic statistical theory are fast and convenient for neutron dose evaluation.In this study,external secondary neutron doses at the heavy ion medical machine in Wuwei,which is equipped with a passive beam delivery system,were calculated using the Monte Carlo method.The dependence of neutron doses on various treatment parameters(incident carbon-ion beam energy,spatial location,field size,and spread-out Bragg peak(SOBP)width)was investigated.Furthermore,the feasibility of applying an analytical model to predict the ambient dose equivalent was verified.For the combination involving an energy of 400 MeV=u and SOBP width of 6 cm,the ambient dose equivalent per therapeutic dose(H=D)at the isocenter was 79.87 mSv=Gy:The H=D value decreased rapidly with increasing spatial distance and slightly with increasing aperture size and SOBP width.The H=D values derived from the Monte Carlo simulations were in good agreement with the results reported in the literature.The analytical model could be used to quickly predict the H=D value along the incidence direction of the beam with an error of less than 20%.Thus,our study contributes to the understanding of the relationship between neutron radiation and treatment configuration parameters,which establishes a basis for predicting non-therapeutic radiation doses in CIRT.

兰州充气谱仪的焦平面探测系统

在兰州充气谱仪上,设计安装了一套新的焦平面探测系统,该系统包括飞行时间(TOF)探测器、盒型硅(Si-box)探测器阵列和反符合(Veto)探测器3部分。Si-box探测器阵列是由3块位置灵敏硅探测器(PSSD)和8块周边硅探测器(SSD)构成,它对注入核的α衰变的探测效率达到80%左右。Si-box探测器阵列与TOF探测器关联可以有效区分注入信号和α衰变信号。Veto探测器与Si-box探测器阵列和TOF探测器关联可以反符合掉高能轻粒子对注入信号和α衰变信号的干扰。简要介绍了PSSD的能量和位置刻度方法。这套探测器系统已经应用于40Ca+175Lu和40Ca+169Tm的实验。实验结果表明,该探测器系统具备很好的本底抑制能力,能够给出干净的α衰变能谱,结合能量-时间-位置关联测量方法可以实现对单原子的探测和鉴别,总体上达到了预期的设计要求。