version 2.0

INFORMATION FOR DIRC OPERATIONS

This note gives some information concerning the solenoid and bucking coils, and describes the monitoring of the fringe field using the DIRC magnetic probes.

I. Solenoid and bucking coils: demagnetization of DIRC shield

The nominal operating currents of these coils are 4600A and 200A, respectively. They can be ramped together minimizing the magnetization of the DIRC shield. However, the power supplies cannot ramp down together all the way to zero, thereby magnetizing the shield each ramp down.

Normal operating procedures is to ramp up the solenoid and bucking coils together, and then to demagnetize the DIRC shield via a cycle (available on cryo display) which ramps down the bucking coil to 0A in 2 minutes and then up to 260A in 2 minutes, and then down to 200A in 2 minutes. This cycle ends with the bucking coil at the operating current AND with the shield demagnetized.

There is also a demagnetization cycle with the solenoid off. This cycle requires the frequent reversal of the bucking coil power supply and takes about 30 minutes.