Preliminary shielding analysis for the CSNS target station monolith

The construction of the China Spallation Neutron Source （CSNS） has been initiated at Dongguan,Guangdong,China.In spallation neutron sources the target station monolith is contaminated by a large number of fast neutrons whose energies can be as large as those of the protons of the proton beam directed towards the tungsten target.A detailed radiation transport analysis of the target station monolith is important for the construction of the CSNS.The analysis is performed using the coupled Monte Carlo and multi-dimensional discrete ordinates method.Successful elimination of the primary ray effects via the two-dimensional uncollided flux and first collision source methodology is also illustrated.The dose at the edge of the monolith is calculated.The results demonstrate that the doses received by the hall staff members are below the required standard limit.     

Preliminary shielding analysis in support of the CSNS target station shutter neutron beam stop design

The construction of China Spallation Neutron Source (CSNS) has been initiated in Dongguan, Guangdong, China. Thus a detailed radiation transport analysis of the shutter neutron beam stop is of vital importance. The analyses are performed using the coupled Monte Carlo and multi-dimensional discrete ordinates method. The target of calculations is to optimize the neutron beamline shielding design to guarantee personal safety and minimize cost. Successful elimination of the primary ray effects via the two-dimensional uncollided flux and the first collision source methodology is also illustrated. Two-dimensional dose distribution is calculated. The dose at the end of the neutron beam line is less than 2.5 μSv/h. The models have ensured that the doses received by the hall staff members are below the standard limit required.     

中国散裂中子源靶站重要部件的辐照损伤计算与分析

本文采用高能粒子输运程序MCNPX 2.5.0,对中国散裂中子源(CSNS)靶站重要部件所使用的钨、SS316不锈钢与Al-6061等材料,由于中子与质子辐照所引起的损伤能量截面与原子离位截面进行了计算,对钨靶体、靶的不锈钢容器、慢化器与反射体的铝容器等部件的辐照损伤量——原子离位次数(displacement per atom,DPA)进行了计算与分析,并给出了质子束斑形状对靶体及靶容器DPA峰值的影响. 这些计算与分析对正在建设的中国散裂中子源靶站的设计及参数选择具有重要的实际意义. 关键词： 中国散裂中子源 损伤能量截面 原子离位截面 DPA     

Calculations of radioactivity and afterheat in the components of the CSNS target station

This paper shows the calculations of radioactivity and afterheat in the components of the China Spallation Neutron Source (CSNS) target station, with the Monte Carlo codes LAHET, MCNP4C and the multigroup code CINDER'90. These calculations provide essential data for the detailed design and maintenance of the CSNS target station.     

Design and analysis of the tunnel connecting the beamcorridor and the spectrum hall of the CSNS

There is a tunnel connecting the beamcorridor and the target station in the spectrum hall in the CSNS project.The length of the tunnel is about 20 m.The shielding design of the tunnel is very significant for the persons working in the spectrum hall because the tunnel is not covered ed soil for shielding.In order to reduce the dose rate at the exit of the cable ducts,we use the ISIS construction,which is designed with four turnings,as a reference for the tunnel design.The thickness of the shielding is obtained by a simulationwith the Monte Carlo Code FLUKA.The result is compared with the data obtained with Moyer Mode and the reliability of the simulation is proved.This paper provides the basis for the design of the tunnel.     

Design and analysis of the tunnel connecting the beamcorridor and the spectrum hall of the CSNS

There is a tunnel connecting the beamcorridor and the target station in the spectrum hall in the CSNS project. The length of the tunnel is about 20 m. The shielding design of the tunnel is very significant for the persons working in the spectrum hall because the tunnel is not covered by soil for shielding. In order to reduce the dose rate at the exit of the cable ducts, we use the ISIS construction, which is designed with four turnings, as a reference for the tunnel design. The thickness of the shielding is obtained by a simulation with the Monte Carlo Code FLUKA. The result is compared with the data obtained with Moyer Mode and the reliability of the simulation is proved. This paper provides the basis for the design of the tunnel.     

Application of the first collision source method to CSNS target station shielding calculation

Ray effects are an inherent problem of the discrete ordinates method. RAY3 D, a functional module of ARES, which is a discrete ordinates code system, employs a semi-analytic first collision source method to mitigate ray effects. This method decomposes the flux into uncollided and collided components, and then calculates them with an analytical method and discrete ordinates method respectively. In this article, RAY3 D is validated by the Kobayashi benchmarks and applied to the neutron beamline shielding problem of China Spallation Neutron Source(CSNS)target station. The numerical results of the Kobayashi benchmarks indicate that the solutions of DONTRAN3 D with RAY3 D agree well with the Monte Carlo solutions. The dose rate at the end of the neutron beamline is less than10.83 μSv/h in the CSNS target station neutron beamline shutter model. RAY3 D can effectively mitigate the ray effects and obtain relatively reasonable results.     

Electromagnetic modeling of the CSNS Hion source extraction system

A Penning surface H^- ion source test stand has been developed for the China Spallation Neutron Source (CSNS) at the Institute of High Energy Physics (IHEP). H^- beams with a current up to 50 mA and a pulse length up to 520μs at a repetition rate of 25 Hz are obtained at present. In order to improve the extraction system based on both the results of the emittance measurements in experiment and the simulation results of the effect of the extraction system on the beam emittance, three dimensional electromagnetic finite element analysis and particle tracking are undertaken. First, the magnetic field of the deflecting magnet is studied in detail, and then the effect of the extraction geometry on the beam transport is also investigated.     

中国散裂中子源直线加速器丝靶扫描器的设计与模拟

In this paper, we report the design and simulation of a wire scanner for the linac of the CSNS （China Spallation Neutron Source）. The wire scanner is used to measure the transverse beam profile and the emittance. The effect of beam energy change upon the mechanical design of the wire scanner must be considered. The simulation results of heat on the two specified wires, tungsten and carbon, by using the finite element method software, ANSYS, are presented. In addition, the effect of wire deformation on the beam profile measurement is qualitatively analyzed, and the signal level of the wire scanner is discussed.     

Design and simulation of a wire scanner for the CSNS linac

In this paper,we report the design and simulation of a wire scanner for the linac of the CSNS(China Spallation Neutron Source).The wire scanner is used to measure the transverse beam profile andthe emittance.The effect of beam energy change upon the mechanical design of the wire scanner must beconsidered.The simulation results of heat on the two specified wires,tungsten and carbon,by using the finite element method software,ANSYS,are presented.In addition,the effect of wire deformation on the beam profile measurement is qualitatively analyzed,and the signal level of the wire scanner is discussed.     

Control system for the CSNS ion source test stand

A penning plasma surface H-ion source test stand for the CSNS has just been constructed at the IHEP.In order to achieve a safe and reliable system,nearly all devices of the ion source are designed to have the capability of both local and remote operation function.The control system consists of PLCs and EPICS real-time software tools separately serving device control and monitoring,PLC integration and OPI support.This paper summarizes the hardware and software implementation satisfying the requirements of the ion source control system.     

Transient electromagnetic simulation and thermal analysis of the DC-biased AC quadrupole magnet for CSNS/RCS

Due to the large eddy currents at the ends of the quadrupole magnets for CSNS/RCS, the magnetic field properties and the heat generation are of great concern. In this paper, we take transient electromagnetic simulation and make use of the eddy current loss from the transient electromagnetic results to perform thermal analysis. Through analysis of the simulated results, the magnetic field dynamic properties of these magnets and a temperature rise are achieved. Finally, the accuracy of the thermal analysis is confirmed by a test of the prototype quadrupole magnet of the RCS.     

Control system for the CSNS ion source test stand

A penning plasma surface H- ion source test stand for the CSNS has just been constructed at the IHEP. In order to achieve a safe and reliable system, nearly all devices of the ion source are designed to have the capability of both local and remote operation function. The control system consists of PLCs and EPICS real-time software tools separately serving device control and monitoring, PLC integration and OPI support. This paper summarizes the hardware and software implementation satisfying the requirements of the ion source control system.     

散裂中子源靶站谱仪的物理设计

中子散射广泛地应用于凝聚态物质研究和应用的众多学科领域,是研究物质微观结构和动态的理想工具之一.散裂中子源能是新一代的加速器基脉冲中子源,能为中子散射提供高通量的脉冲中子.文章重点介绍了散裂中子源项目CSNS中靶站和谱仪的建设内容和设计工作的进展.     

2GW功率下CFETR中子屏蔽的初步中子学研究

在中国聚变工程实验堆(CFETR)真空室最新设计尺寸下,利用蒙特卡洛中子输运程序(MCNP)建立一维中子学模型,在2GW 的聚变功率下进行了计算。分析了中子反射材料ZrH₂ 对中子的屏蔽效果,发现200mm 的反射层可以屏蔽94.3%的中子通量和94.9%的中子核热。研究CFETR 在运行10 个满功率年(FPY)和20FPY 后,对应不同中子壁载荷的最小屏蔽包层厚度。结果显示,装置运行10FPY 后中子壁载荷在1.0MW·m⁻²、1.5MW·m⁻²、 2.5MW·m⁻² 时所对应的最小屏蔽包层厚度分别为44cm、53cm、65cm;而在装置运行20FPY 后,则需要在径向方向更厚的屏蔽包层才能满足中子屏蔽要求。屏蔽包层的尺寸优化将为目前阶段的CFETR 先进包层设计提供参考。     

Study on collimation and shielding of the back-streaming neutrons at the CSNS target

The back-streaming neutrons from the spallation target at CSNS are very intense,and can pose serious damage problems for the devices in the accelerator-target interface region. To tackle the problems,a possible scheme for this region was studied,namely a specially designed optics for the proton beam line produces two beam waists,and two collimators are placed at the two waist positions to maximize the collimation effect of the back-streaming neutrons. Detailed Monte Carlo simulations with the beams in the two different CSNS phases show the effectiveness of the collimation system,and the radiation dose rate decreases largely in the interface section. This can ensure the use of epoxy coils for the last magnets and other devices in the beam transport line with reasonable lifetimes,e.g.,thirty years. The design philosophy for such an accelerator-target interface region can also be applicable to other high-power proton beam applications.     

Study on collimation and shielding of the back-streaming neutrons at the CSNS target

The back-streaming neutrons from the spallation target at CSNS are very intense, and can pose serious damage problems for the devices in the accelerator-target interface region. To tackle the problems, a possible scheme for this region was studied, namely a specially designed optics for the proton beam line produces two beam waists, and two collimators are placed at the two waist positions to maximize the collimation effect of the back-streaming neutrons. Detailed Monte Carlo simulations with the beams in the two different CSNS phases show the effectiveness of the collimation system, and the radiation dose rate decreases largely in the interface section. This can ensure the use of epoxy coils for the last magnets and other devices in the beam transport line with reasonable lifetimes, e.g., thirty years. The design philosophy for such an accelerator-target interface region can also be applicable to other high-power proton beam applications.     

在屏蔽墙外用雷姆计测量高能中子的修正因子

考虑到穿过混凝土屏蔽墙后中子能谱相对变“硬”的效应和中子雷姆计的能量响应特性,计算了用10英寸直径单球雷姆计和标准A–B雷姆计在屏蔽墙外测量中能重离子反应出射高能中子剂量当量的修正因子.     

Study on space charge effects of the CSNS/RCS

The Rapid Cycling Synchrotron (RCS) is a key component of the China Spallation Neutron Source (CSNS). The space charge effect is one of the most important issues in the CSNS/RCS, which limits the maximum beam intensity, as well as the maximum beam power. Space charge effects are the main source of emittance growth and beam loss in the RCS. Space charge effects have been studied by simulation for the CSNS/RCS. By optimizing the painting orbit, the optimized painting distribution was obtained. The space charge effects during the acceleration are studied and dangerous resonances, which may induce emittance growth and beam loss, are investigated. The results are an important reference for the design and commissioning of the CSNS/RCS.     

Optimization of the collimation system for CSNS/RCS with the robust conjugate direction search algorithm

The Robust Conjugate Direction Search(RCDS) method is used to optimize the collimation system for the Rapid Cycling Synchrotron(RCS) of the China Spallation Neutron Source(CSNS). The parameters of secondary collimators are optimized for a better performance of the collimation system. To improve the efficiency of the optimization, the Objective Ring Beam Injection and Tracking(ORBIT) parallel module combined with MATLAB parallel computing is used, which can run multiple ORBIT instances simultaneously. This study presents a way to find an optimal parameter combination of the secondary collimators for a machine model in preparation for CSNS/RCS commissioning.