Experimental study of stainless steel chamber for a pulsed bending magnet of the KEK E-/E+ injector linac

KEK injector linac has two-storied pre-injectors; one for a high-intensity primary beam for positron generation and the other for a low-emittance electron beam. The primary beam generated by a thermionic gun on the upper stage is merged into the lower beam-line by two DC bending magnets and three DC quadrupole magnets. The DC bending magnets will be replaced with pulse bending magnets for pulse-by-pulse switching of the beams from the two pre-injectors in Phase-3 operation of SuperKEKB. To evaluate operation condition of the pulse magnets and stainless steel chambers, we performed simulations and measurements on the heat generated by eddy current and the von Mises stress in the temperature rise. The estimated stress, the measured temperature distribution and outgas in the chambers demonstrated full operation in 50 Hz full pulse repetition. However the measured temperature rise in the coils of the magnets limited the operation time to be less than an hour at 50 Hz or full operation at 25 Hz or lower. (author)