Reduction of Outgassing for Suppressing Electrical Breakdown in the Kicker Magnet of J-PARC RCS

Abstract

Extraction kicker magnets in the RCS of the J-PARC project are now under construction. They are pulse magnets with high charging voltage of 60 kV, which are installed in vacuum chambers. They mainly consist of aluminum alloy for the electrode plates and ferrites for the magnetic cores. Some structures of the magnet were improved to suppress discharge, and we thoroughly reduced the rate of outgassing from the components. The surface of the aluminum alloy was finished by pit-free electropolishing. Aluminum alloy and ferrites cores were baked under vacuum before construction of the magnet. They were each baked until water, which is the main outgassing component, was reduced. As a result, their outgassing rates were reduced by two or three orders of magnitude. The effect of the excitation of the magnet was examined. Outgassing of certain components increased with application of the high voltage. These components were reduced by repeated periods of continuous excitation.