QT Dropout during FMS HV test run sequence

Jingguo noticed that in running HV scans for the large cell FMS, we observed sudden changes in ADC counting rates summed over all channels.

Apparently this is do to QT crates suddenly failing to collect data.


As an example, in run 11200039 (large cell HV = 1500 Volts), this occurred 344 events into the test run.

(for list of test runs: http://drupal.star.bnl.gov/STAR/blog/jgma/2010/jul/21/summary-runs-taken-fms-test)


See event display for events 275 to 374 of run 11200039.


Everything seems ok through event 343

On event 344, the lower South QT reads out and little else.

For subsequent events, the other 3 QT crates read out but the lower south crate seems to be malfunctioning.

All events before 343 look similar and all events after 344 look similar (with a QT crate problem). Event 344 is unique.


Apparently, the problem was resolved by stopping the run and starting another run although these runs of ~100 triggers were mostly doing this for this period.

 Just for reference, here is a picture showing QT card boundaries.