• M.T. Rooney, C.J. Densham
  STFC/RAL, Chilton, Didcot, Oxon
• Y. Yamada
  KEK, Ibaraki

The target station of the T2K neutrino facility requires a beam window to separate the target chamber, containing helium at atmospheric pressure, from the secondary beam line, which is maintained at ultra high vacuum. In addition to withstanding this differential pressure, the window must survive induced stresses due to intense heating resulting from interaction with a 0.75 MW pulsed proton beam. The design consists of a hemispherical double window with forced convection helium cooling in the volume enclosed, manufactured from titanium alloy. Preliminary analysis suggested that 'shock' waves induced by the pulsed nature of the beam will form the dominant mode of stress. The finite element software ANSYS Mechanical (V10) has been used to simulate the effect of beam impingement on a variety of window thicknesses in an attempt to find the optimum geometry. Results have shown that through thickness stress waves can be amplified if successive bunches arrive in phase with the waves generated by previous bunches. Therefore, thickness has been shown to be a critical variable in determining the window’s resistance to induced thermal shock.