5.5.6.6  Handling Considerations

The FPP straw chambers are very delicate devices which are absolutely essential to many Hall A physics experiments. Thus, extreme care must be taken whenever they are moved or used. Also, extreme care must be taken that other objects are not moved into them.

• Before moving a straw chamber, ensure that any protective plates are in position.
• Disconnect and reconnect all TDC, HV, and LV cables with care.
• When initiating gas flow, pay strict attention to the feedback parameters. Straw chambers are not very sensitive to overpressure of perhaps 50 - 100 torr, but the straw chambers can be easily destroyed if a few torr underpressure.
• Never attempt to apply HV to the chambers until gas flow conditions have reached steady-state.
• As the amount of heat generated by the pre-amp/discriminator cards is substantial, always make sure adequate cooling is provided before attempting to run. This is mostly ensured by making certain that the various cooling holes through the Faraday shields are not covered. The chambers have internally mounted fans where needed, which are powered up along with the readout cards.
• If the leakage current on the high voltage rises linearly with voltage and indicates 26 M to ground, a wire has broken and is shorted to ground!