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

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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.