HUST-PTF质子治疗装置能量选择段真空设计与仿真

Design and simulation of vacuum system in energy selection section for HUST-PTF

能量选择段是华中科技大学质子治疗装置束流线的重要组成部分,其位于回旋加速器下游,包含四极铁组、kicker磁铁、降能器以及DBA(Double Bending Achromatic)消色散段等几个部分。该段真空室种类和插入件较多,且在降能器下游辐射剂量较大,增加了真空系统设计与选型的难度。根据系统设计要求,该段动态真空度需好于5×10-4 Pa。本文利用MOLFLOW软件对能量选择段真空系统进行模拟,分析不同工况下的压强分布,并对各类真空室进行力学强度校核。仿真结果显示:能量选择段真空度均好于4.14×10-5 Pa,比系统设计要求高一个量级,且各类真空室的机械形变小于0.3 mm,不会引起额外的束损。因而,该段真空室的动态真空度和机械强度均可满足系统设计要求。

[Background] Energy selection section(ESS) is an important part of the beam line of Huazhong University of Science and Technology Proton Therapy Facility(HUST-PTF). It is located downstream of the cyclotron and includes a set of quadrupoles, a kicker magnet system, an energy degrader system and a double bending achromatic(DBA) section. Various types of vacuum pipe and several inserts are placed in this section.What’s worse, large radiation exists in the downstream of the degrader. [Purpose] This study aims at the design of the vacuum system and the selection of the vacuum pump to satisfy system requirements for better than 5×10-4 Pa dynamic vacuum pressure. [Methods] First of all, the ESS vacuum system was simulated by Monte Carlo method in the MOLFLOW software. Then the pressure distributions under different working conditions were analyzed, and the mechanical strength of various vacuum pipe was calculated and checked. [Results] The simulation results show that the pressure in the ESS is lower than 4.14×10-5 Pa, an order of magnitude better than the system requirement. The mechanical deformation of various vacuum pipes is less than 0.3 mm, avoiding the extra beam loss. [Conclusions]Both of the dynamic vacuum pressure and the mechanical strength can meet the design requirements.