Specifications of a neutron exposure accelerator system for biological effects experiments (NASBEE) in NIRS

We developed a neutron irradiation facility, neutron exposure accelerator system for biological effect experiments (NASBEE) for biological studies in National Institute of Radiological Sciences, Japan. Irradiation field of 2 MeV average neutrons generated by a Be(d–n)B reaction is established. Dose uniformity of 240 mm in diameter irradiation field is producible within ±2.5% with a dose rate of 0.87 Gy/h at sample target distance of 1170 mm. Two irradiation rooms, a specific pathogen-free (SPF) conditioned one and a conventional, are now available. Irradiation protocols for in vitro experiments are now established and demonstrated by obtaining a relative biological effectiveness (RBE) of cell inactivation measured to be 3.54 with 10% survival dose (D₁₀).     

Control of Batch Polymerizations by Continued Feed

The conventional kinetic scheme for a free-radical homopolymerization is modified to incorporate dilution by a feed stream and the effect of propagation on solution density. Neglect of the volume change can result in prediction of erroneously high conversions. The distribution of average molecular weight fractions is evaluated. In the absence of gelation and transfer reactions, the broadening, which is usually thought to arise from varying composition, is found to be small compared to that which is intrinsic to the addition mechanism.     

Design of a stripline kicker for tune measurement in CSNS RCS

For CSNS RCS tune measurement, tune value is measured by exciting the bunch with a strip-line kicker fed with white noise and using a FFT algorithm. This article simulates the strip-line kicker in RCS and the efficiency of the kicker is discussed in a Matlab environment. The parameters of the kicker with an arc electrode structure such as a VSWR, wake impedance, and thermal state are analyzed based on the advantages of this design.     

Undulator linear accelerator as a generator of ribbon high power ion beams

The characteristics of an undulator linear accelerator, based on the use of a plane electrostatic undulator (UNDULAC-E), is presented in this paper. It is shown that UNDULAC-E can be used as a high intensity ribbon ion beam source. The results of modeling of dynamics and construction are presented.     

诊断中性束加速电源打火检测与保护电路的研究与设计

通过检测打火短路过程中产生较大的di/dt 和du/dt 来实现高压电源的打火短路保护。在研究了中性束加速电源控制和保护特点的基础上, 设计了诊断中性束加速电源在打火短路过程中的di/dt 和du/dt 的检测电路和相应的保护电路, 实现提前对加速器高压电源打火短路的保护。     

高功率粒子束及其应用

本文评价了高功率粒子束的工作原理及其应用:文中以闪光-Ⅰ强流脉冲电子束加速器为例,论述了机器的基本技术和它的工作特性 高功率粒子束目前已经应用到许多重要研究领域。包括:核辐射效应模拟源、闪光X射线照相、高功率激光器研究、惯性约束聚变、高功率微波的产生、离子集体加速等方面。 报告中简述了我国在高功率粒子束加速器建造和开拓应用方面取得的进展。 最后,也指出了高功率粒子束技术今后发展有关的研究课题。     

The spatial distribution of thermal and epithermal neutrons in a graphite moderated spallation neutron field

The Gamma-3 assembly is located at the Joint Institute for Nuclear Research, Dubna, Russia. It consists of a cylindrical lead target (ø = 8 cm, L = 58.8 cm) surrounded by reactor grade graphite (110 × 110 × 60 cm). The target was irradiated with a beam of 1.6 GeV deuterons from the Nuclotron accelerator and CR-39 track detectors coupled to LR-115 2B film were used to measure the slow neutron distribution on the surface of the graphite. The detection efficiency of the CR-39 in the CR-39/LR-115 2B system was measured using a custom made calibration setup and found to be (1.12 ± 0.05) × 10⁻³ and (6.1 ± 1.2) × 10⁻⁴ tracks per neutron, for thermal and epithermal neutrons respectively, under the etching and counting procedures described in this work. The irradiation of the Gamma-3 was also simulated using MCNPX 2.7 Monte Carlo code and good agreement between the experimental and calculated track densities was found. This serves as a good validation for the computational models used to simulate spallation neutron production, transport and moderation.     

Neutron yields from massive lead and uranium targets irradiated with relativistic protons

Long-lived isotopes can be transmuted into stable or short-lived elements either by neutron captures or neutron induced fission. The need of a large excess of neutrons has led to the use of accelerator driven sources (ADS). A series of experiments were carried out at the Synchrophasotron/Nuclotron of the Joint Institute for Nuclear Research (JINR) Dubna, using protons of 1.0 GeV. Solid Lead and Uranium targets surrounded by paraffin moderator were irradiated. On the outer surface of the moderator a number of Solid State Track Detectors were placed to monitor neutron spatial distribution. The results showed that the maximum neutron production was reached within the range of one to two proton mean free paths in the target. Then decreasing neutron production follows the proton beam attenuation along the target. Moreover, the results showed both targets neutron production evolution along the target, to be the same. However, neutron flux per incident proton is depended on the target mass, which was found to be higher for the heavier target.     

Influence of accelerator type on properties of NR/EPDM blends

The effect of accelerator type on processability and mechanical properties of 60/40 natural rubber/ethylene propylene diene monomer (NR/EPDM) blend was investigated. Three groups of commercial accelerators were selected, i.e., sulfenamide group (Santocure-TBBS), thiuram group (Perkacit-TMTD) and mercapto group (Perkacit-MBT and Perkacit-MBTS). The results reveal that the accelerator type not only affects the cure characteristics, but also has great influence on compound viscosity. Among the accelerators studied, TBBS gives the best processing safety together with a relatively high state of cure. In addition, TBBS also provides good cure compatibility between the NR and EPDM phases, giving rise to superior mechanical properties. Although TMTD could give a high state of cure, it causes severe cure incompatibility, leading to poor tensile strength. Due to their lower reactivity, the two mercapto accelerators give a relatively low state of cure. Therefore, the vulcanizates obtained possess low modulus and hardness as well as degree of elasticity. Surprisingly, it is found that the tensile strength of the MBTS-cured blend is relatively high. Good cure compatibility given by MBTS could be used to explain the results.     

4 MV静电加速器调试中出现的问题及解决方案

 4 MV静电加速器由高压系统、离子源及束流系统、控制系统和气体系统四部分组成。调试中出现了离子源不起弧、加速管破裂、控制系统失灵和输电带输电能力降低等技术问题，分析了出现这些问题的原因，然后分别采取了相应的措施加以解决：变换工作流程，在每次关机前先把引出电压降为零，开机时等离子源起弧后再把引出电压升到预定值；对过渡法兰进行车加工，重新封装；对高压端的控制设备采取屏蔽措施，在输入、输出端使用TVS二极管，对控制软件进行抗干扰设计；对绝缘气体进行循环干燥等。调试出了流强为100 μA、能量在3 MeV以上的稳定质子流。