USE THE FLASHER -- Re: [BLAST_ANAWARE] tdc shift in unpol deuterium runs:

From: Karen Dow (kdow@mit.edu)
Date: Tue Aug 19 2003 - 10:46:28 EDT


         Chris is right, the flasher events (trig==8) should give you info
on any timing shifts. BUT THE FLASHER HAS TO BE TURNED ON IN ORDER TO GET
EVENTS!!! I just went out to the counting bay, and the flasher was OFF. I
looked at a sample of runs between about 1790 and 2090, and I don't see any
trig==8 events in the lr ntuple. Maybe lr throws out these events? But
there are events for all the other trigger types (1-7), so I suspect the
flasher just hasn't been on most of the time.

         Turning the flasher on is simple. Click on the daisy at the
bottom of any dblast screen to start the EPICS application, then click the
ON button. The label "Flasher Control" will turn from red to green. Turn
the flasher off if we won't be taking data for a few hours, to save the
laser. When you're on shift and taking data, check that the flasher is on!

         You will also be able to tell the flasher is on by looking at the
scalers. The 8th and 9th columns have the rates for the various triggers;
FLASH is the 8th trigger, should count about 1Hz. This doesn't guarantee
there are actually flasher events, because this trigger must still overlap
with the Common Strobe (the OR of all TOF meantimes) at the trigger
supervisor. I checked this overlap this morning, and it is good, with the
flasher coming late so it determines the trigger timing.

                                         Karen

At 04:25 PM 8/18/2003 -0400, you wrote:
>hi,
>now that we have the flasher incorporated into the trigger, it should be
>very easy to do this on a run-by-run basis, just plot the flasher tdc
>top/bottom spectra, and use this to calibrate the offsets for each run,
>and maybe check if it has changed since last time as a possible trouble flag.
>--chris



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