[BLAST_TOF] Thursday - end of day shift

From: Adrian T Sindile (asindile@cisunix.unh.edu)
Date: Thu Sep 12 2002 - 18:51:40 EDT


Hi!
In the morning I was updated by Tavi that during the night he found out
that the reason we are not getting any events for the backward paddles
is that the big Cherenkov boxes are not working properly (they were never
gain matched to the necessary level, the voltages are very low).
He also said that he believed the first small paddle (the one we had been
using for the most forward TOF) gives a very poor signal, which could be
the cause for not getting signals for the corresponding efficiency
"sandwich" - I have doubts this would explain that completely.

Starting the shift, Chris and I decided the right thing would be to move
the 3 not working small paddles to another set of TOFs, keeping the
working one as a reference, and hoping to get 99% efficiency on that one
again (it was reported 97-98% after lowering thresholds by Pete, but
before that I had obtained 99% with thresholds raised).

We went to the South Hall and set up the small paddles so that the test
TOFs are now LTOF#1 (the one that was 99% before), LTOF#2, #4 and #7
(starting from zero).

11 AM - new setup complete, start run # 1687;
        set up new trigger (TOF2efficiency.settings), reflecting new setup;
        wrote TOF2eff.C, reflecting new settings (modified the old macro).

We analyzed the new run and got 97.1% efficiency for the LTOF#1,
consistent with latest results from Pete. However, no other "sandwich"
gave us much: the backward 2 did not give us anything, the first one (for
LTOF#2) gave very few events.
The analysis revealed that we forgot to move the fannout cables in the
D-tunnel for 2 of the new positions of the small paddles.

12 PM - Doug takes over for a few runs with field on.

After lunch we went to the D-tunnel and fixed the fan-out cables, hoping
to see something in the backward "sandwiches" now.
Powered down the coils, took run 1697 -> LTOF#1 efficiency still 97% (of
course since we did not change anything for it); still nothing for the
backward stuff (or LTOF#2).

Adjusted the voltages for the small paddles (MySQL database) even if not
very different from old setup, put 1 SCCM gas (Doug had taken it off for
his last run).
Took run 1698 -> no change, LTOF#1 97%, no other sandwich showing
anything.
By the end of shift, our conclusion is that the second Cherenkov box
denies everything, just as the other two big boxes Tavi reported about (we
had been thinking the fannout cables and then the voltages were the cause
for the small paddles misbehavior). We did not have time to check the
Cherenkov signal in detail.
We suggest next shifts look into the timing of second Cherenkov and the
signal we get from that box.

At the end of the shift, we moved the signal cable going into the
small paddle corresponding to LTOF#2 from one BNC connection on the PMT to
the other (that PMT has double unmarked BNC connectors).
We tried taking two runs, but CCR had problems with the beam, so we left
Pete and Nick to see if they need to move that BNC cable back or not -
and of course to dig more into the LTOF#1 97-99% contradiction and the
second Cherenkov signal - with the hoe that would give us results for
other TOFs.

Adrian and Chris

-------------------------------
Adrian Sindile
Research Assistant
Nuclear Physics Group
University of New Hampshire
phone: (603)862-1691
FAX: (603)862-2998
email: asindile@alberti.unh.edu
http://einstein.unh.edu/~adrian/



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