高功率环境下多丝靶设计及运行考虑

Design and operation experiences of a multi-wire detector under high beam power environment

多丝靶被广泛用于束流截面测量,但是常常因为束流功率沉积导致丝被损坏。为了研究不同束流参数以及丝靶设计与丝上温度和丝变形之间的关联,开发了基于后向欧拉法的自适应步长多丝靶温度数值模拟程序,并在离子源平台上开展了由温度导致的多丝靶变形实验。模拟和实验表明:在缺失恒定张力的情况下,温度是导致丝变形的主因。基于我们的模拟计算、实验验证以及操作经验,在丝温度低于1 300 K的情况下,拉丝采用锡焊固定的方式,其结构简单成本低;在高于1 300 K的情况下,采用弹簧张力的固定方式,可以提供恒定的张力,避免丝变形。

[Background]Multi-Wires detector(MW)is widely used in beam profile measurements.However,wire deformation and even wire broken have also happened frequently during the MW operation due to beam power deposition on the wire under high beam power environment.[Purpose]This study aims to investigate the influences of the beam parameters and detector design,especially wire tension structure,on the wire temperature and wire deformation arising therefrom.[Methods]Firstly,based on the backward Euler method with adaptive steps,a numerical algorithm was developed to conduct temperature simulation of MW.Then,verification experiments with various beam parameters and detector design of MW were performed in an ion source platform at Institute of Modern Physics(IMP),Chinese Academy of Sciences,and the wire deformation caused by temperature was reproduced and observed at HIMMWW(Heavy Ion Medical Machine at WuWei city,China)complex.Finally,comparative analysis was conducted on the relevant results to find the appropriate beam parameters and detector design.[Results&Conclusions]Experimental results show that temperature plays an essential role on wire deformation if none tension mechanism is implemented on wire structure.Based on numerical simulations,experiments verifications and operation experiences,a fixed wire tension maintained by welding is appropriate while the wire temperature is below 1300 K,which also provides a simple construction and a low cost.After exceeding 1300 K,pre-tensioning by a spring is essential to support the wire with a constant tension to avoid deformation.