Re: end of day shift, 09/25/02

From: Karen Dow (kdow@mit.edu)
Date: Thu Sep 26 2002 - 08:42:49 EDT


Adrian,

        Two questions/comments.

1) Did you get to check any possible DC offset out of the CAEN analog
adders (as Tancredi suggested yesterday)? If there was a big enough
positive DC offset, the discriminator might not fire, because the signal
never gets to -30mV absolute (or wherever the disc is set), even though
the pulse height compared to the baseline is bigger than that. Then you
wouldn't have any Cer logic signal for the trigger, or for a TDC stop.
Also, as per the adder manual, the max input signal (per channel, I
think) is +-400mV. With the flasher, it looks like you exceed that.

2) A discrepancy between the CODA rate and the MLU scalers rate: I
assume we are talking about the DIFFERENTIAL CODA rate; the integrated
rate has any sleep time included in it, so it could easily be lower than
the MLU rate. The problem is likely the overlap between the Physics
Trigger PT from the MLU to the TS, and the Common Strobe CS (OR of MT of
all TOFs) to the TS. The CS should come later than the PT. Pete found
a flaky cable yesterday in the CS long delay (so he got NO CS at all);
maybe the connection is intermittent now. Or maybe, depending on your
trigger (flasher, cosmics, beam), the relative PT-CS timing moves
around, and the overlap is only right for some types of triggers.

                                        Karen



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