Study and development of vacuum window and its cooling mechanism at high intensity beam line

为了实现像J-PARC这样的强光物理实验，必须开发和实现具有冷却能力和远程维护方法的能承受强光的束流窗。例如，我与英国KEK和RAL的工程师作为合作者，设计并开发了真空窗，将J-PARC中微子束线目标的主束线真空系统与He容器分开。首先，我用模拟代码MARS， GEANT和ANSYS对高强度质子束通过窗户时的温升和热应力进行了估算，确定了在半球面双层墙壁之间通过氦气来冷却窗户，没有根本的设计问题。英国的合作者通过模拟脉冲应力及其传播，证实了用0.3 mm厚的Ti-6A1-4V合金制成的窗口可以承受3 × 10^<14>个质子的脉冲热应力。他们还证实，通过模拟双壁之间的氦气流动，可以在半球形窗口表面实现所需的100 W/m^2K的传热系数。我监督了RAL （UK）合作者对窗口系统的详细设计的实施。这包括钛合金窗户与枕头密封法兰的组合，允许远程拆卸窗户。我制作了镜面配合法兰和Helicoflex密封件的原型，并通过测量它们的真空泄漏率来确认它们可以用于实际的光束线。我与加拿大TRIUMF和英国RAL的工程师合作，研究远程维护中可能出现的问题。最后，我完成了波束窗的服务和外部系统的设计，可以在J-PARC等真实的波束线中使用，考虑到周围的屏蔽，远程维护方法，氦气循环系统等。

In order to realize physics experiments with very high intensity beam such as J-PARC, it is indispensable to develop and realize the beam window that can stand for very high intensity beam with cooling ability and remote maintenance method. As a example, I designed and developed the vacuum window, which separates the vacuum system of the primary beam line from the He vessel for the target in the Neutrino beam line at J-PARC, together with engineers of KEK and RAL in UK as collaborators. At first, I confirmed that we have no fundamental design problem if we cool the window by flowing helium gas between hemispherical double walls by estimating the temperature rise and thermal stress when high intensity proton beam passes through it with simulation codes MARS, GEANT and ANSYS. The collaborators in UK confirmed that the window made with 0.3 mm thick Ti-6A1-4V alloy can stand for the pulsed thermal stress by 3x10^<14> protons by simulating the pulsed stress and its propagation. They also confirmed that the required thermal transfer coefficient of 100 W/m^2K can be achieved at the hemispherical window surface by simulating the helium gas flow between double walls. I oversaw the implementation by RAL (UK) collaborators of the detailed design of the window system. This included the combination of the Ti alloy window together with the pillow seal flanges that permit the remote disassembly of the window. I made prototypes of the mirror mating flanges and Helicoflex seals and confirmed that those can be used in the real beam lines by measuring the vacuum leak rate of those. I studied possible problems in the remote maintenance together with the engineers of TRIUMF (Canada) and RAL (UK) as collaborators. Finally, I finalized the design of services and external systems for the beam window, which can be used in the real beam line such as J-PARC, considering surrounding shields, remote maintenance methods, helium gas circulation system and etc.