Development of thick hybrid-type carbon stripper foils with high durability at 1800 K for RCS of J-PARC

The Japan-Proton Accelerator Research Complexes (J-PARC) requires thick carbon stripper foils (250–500 μg/cm2) to strip electrons from the H− beam supplied by the linac before injection into the Rapid Cycling Synchrotron (RCS). The 200 MeV H− beam from the linac has a pulse length of 0.5 ms with a repetition rate of 25 Hz and an average beam current of 335 μA. For this high-energy and high-intensity beam, conventional carbon stripper foils will break in a very short time and even a diamond foil will be ruptured at around 1800 K by the MW class accelerator. Thus, thick carbon stripper foils with high durability at 1800 K produced by energy deposition in the foil are indispensable for this accelerator. For this purpose, we have been developing carbon stripper foils of 350 μg/cm2 by means of both the controlled DC and AC/DC arc-discharge methods. Recently, we have successfully developed hybrid type thick boron-doped carbon stripper foils, which showed a drastic improvement not only with respect to the lifetime, but also with respect to thickness reduction and shrinkage at high temperature during long beam irradiation. In this report the preparation procedure and lifetime measurements with a 3.2 MeV, Ne+ beam are presented.