The TTF-III power coupler adopted for the ILC baseline cavity design has shown a tendency to have long initial high power processing time. A possible cause for the long processing time is believed to be multipacting in various regions of the coupler. To better understand the rf processing limitations of the coupler, SLAC, in collaboration with LLNL, has built a flexible high-power test stand. The coupler comprises of different components including the cold/warm coaxes, the cold/warm bellows and the ceramic window separating the cold and warm sides. To corroborate with experimental measurements, Track3P has been used to numerical simulate of multipacting for individual components.
