Control of the multipactoring by the surface coating of the exciter electrodes in J-PARC MR

Multiple-purpose Exciters are installed in the 30 GeV main ring of J-PARC, and they are used for Bunch by Bunch Feedback, Transverse RF for slow extraction, Tune measurement and Intra-bunch feedback study. Since these Exciters are Strip line Kickers which use the parallel electrodes, a multipactoring is generated depending on the conditions of applied RF. The multipactoring gives damage to an electrode surface, and also causes the electric discharge and the beam loss due to vacuum deterioration. Then, we tried to control the multipactoring by coating of the surface of the electrodes. This time, for three kinds of treatments on the stainless steel electrodes (electrolytic polished, Diamond-Like Carbon (DLC) coated, Titanium Nitride (TiN) coated), the secondary electron yield (SEY) and the pressure rise in the vacuum chamber by multipactoring when the RF is applied were measured. (author)