Modeling of the sparks in Q2-bellows of the PEP-II SLAC B-factory

The PEP-II B-factory at SLAC has recently experienced unexpected aborts due to anomalously high radiation levels at the BaBar detector. Before the problem was finally traced, we performed a wake field analysis of the Q-2 bellows, which is located at a distance of 2.2 m from the interaction point. Analysis showed that the electric field in a small gap between a ceramic tile and metal flange can be high enough to produce sparks or even breakdowns. Later traces of sparks were found in this bellows.