多功能旋转靶装置研究

Research on Multifunctional Rotating Target Device

  • 摘要: 针对D-D中子发生器采用静态水冷靶时中子产额不稳定、中子产额持续下降等主要问题,研制了一套多功能紧凑型旋转靶装置。装置采用一体化设计,结构紧凑、尺寸小,具备靶体高速旋转和水冷、靶点可视化监测、靶面温度实时测量、中子产额实时监测等功能。本文介绍了该装置的主体结构、功能设计和性能测试,以及靶结构对中子散射影响的模拟计算。性能测试结果表明,该装置真空度满足加速器运行要求,相比静态水冷靶,束流靶点中心最高温度明显降低,中子产额稳定度明显提高。模拟计算结果显示中子能谱峰展宽范围为0~0.057 7 MeV,散射中子占比为10.53%~26.75%。本文还针对模拟计算结果和测量结果中存在的问题进行了分析,提出了改进和优化方案。

     

    Abstract: This paper focuses on the main problems of unstable neutron yield and continuous decrease in neutron yield when using static water-cooled target in the D-D neutron generator. A multifunctional compact rotating target device was developed, which adopted an integrated design and was compact in structure and small in size, equipped with functions such as high-speed rotation and water-cooled of target body, visual monitoring of target point, real-time measurement of target surface temperature, and real-time monitoring of neutron yield. This paper introduced the performance parameters of several major high current neutron generators rotating targets in the world, and elaborated on the advantages of rotating targets compared to traditional static targets. The main structure and functional design of the device were introduced. The main structure of the target was composed of a vacuum target chamber, target plates, beam pipes, circulating cooling water pipes, accompanying particle pipes, target monitoring pipes, stepper motors, and corresponding seals. The functions and structural components of each device were elaborated in detail. In order to study the influence of the structure of the rotating target device on neutron scattering, the energy spectrum distribution of source neutron at various angles in space was simulated by using TARGET software. The energy spectrum data was input into the MCNP data card, and 40 point detectors were set up, with 0°-360° distributed at a distance of 1 m from the target surface. The influence of target structure on neutron scattering was calculated using MCNP simulation. The result of simulation data shows that the target structure broadens the neutron spectrum peak by 0-0.057 7 MeV, and the relative angular yield of scattered neutrons at various angles accounts for 10.53%-26.75%. The influencing factors of neutron scattering effects at several key angles based on energy spectrum curves were analyzed. The vacuum degree, target surface temperature load, and neutron yield stability of the rotating target device were tested. First of all, the average energy of a 300 keV deuterium particle beam in a target thickness of 1 mg/cm2 deuterium titanium target was theoretically calculated. The source neutron flux was calculated using the average energy, and then the device was installed on a neutron generator at Chinese Institute of Atomic Energy to conduct preliminary tests on various performance. The test results show that the vacuum degree of the rotating target remains stable at around 3×10−5 Pa for a long time. Compared with static targets, rotating target improves neutron yield stability by one order of magnitude, and the maximum temperature of the target decreases by 13 ℃. And the cooling effect of the rotating target device was analyzed under different rotational speeds. The results show that as the rotational speed increases, the cooling effect gradually improves. Therefore, the rotating target device designed in this paper basically achieves the expected function, effectively solving the problem of continuous decrease in neutron yield, and the functional test results are normal with low neutron scattering effect. Finally, this paper also analyzes the problems in the simulation calculation results and measurement results, and proposes improvement and optimization plans.

     

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