Performance of the BEBC Internal Picket Fence

The Internal Picket Fence (IPF) for BEBC (Big European Bubble Chamber) is a proportional tube counter system mounted in the bubble chamber vacuum tank close to the liquid hydrogen. Its purpose is to give a timing signal for all events where a charged particle leaves the chamber. The system was installed and tested early this year. We report on performance as seen during several weeks of BEBC operations at cryogenic temperatures with a 3.5 T magnetic field.