As Adrian just pointed out, the MLUs were set incorrectly last night
to see e-right p-left coincidences.
The plan for this evening with beam is to set up the correct MLU
patterns and start the search for symmetric e-p coincidences. The
correct patterns should be:
LSectMLU pattern
00xxxxx000001000 0000000000000001
00xxxxx100000000 0000000000000001
RSectMLU pattern
00xxxx0100000000 0000000000000001
00xxxx0000001000 0000000000000001
XSectMLU pattern
0000000001000001 0000000000000001
If the CODA rates are acceptable, the pattern could be expanded to
include additional conjugate pairs: for example
LSectMLU pattern
00xxxxx000001000 0000000000000001
00xxxxx000010000 0000000000000001
00xxxxx100000000 0000000000000001
RSectMLU pattern
00xxxx0100000000 0000000000000001
00xxxx0000010000 0000000000000001
00xxxx0000001000 0000000000000001
XSectMLU pattern
0000000001000001 0000000000000001
since both TOFs 3 and 4 can be in coincidence with 12/13 in the
opposite sector.
If sufficient data are not accumulated by midnight when Compton
takes over, then we should continue in the morning.
In the meantime, before beam comes on, we can simulate the effect
of e-p coincidences by adding some cable delays to the signal cables
out of TOF12 on either sector. DO NOT CHANGE THE PROGRAMMABLE DELAYS
UNDER THREAT OF TORTURE WORSE THAN DEATH!!! Instead, add a 20 ns
length of cable to each of TOF12 top and bottom either at the patch
in the SH or at the patch in the D-Tunnel. This will simulate the
20 ns additional flight time of a back angle proton. Then, with the
flasher, look for coincidences with the above trigger.
Tancredi is confident that the left and right retiming OR outputs
are now in time +/- 1 ns. Nevertheless, we will move the START CTR
back to the left side for a final check. After doing so, the START
will be put into RTOF15 as before and checked against the LTOFs.
One then must correct the histogram for the measured offset difference
between the LTOF and RTOF TDCs since the START is now in RTOF15
rather than LTOF15 as it was for the right sector measurement. If
this is not clear, please talk to either Tancredi or me before doing
anything foolish. This move of the START will occur either tomorrow
or Sunday depending on the beam and the success of the e-p search.
The final step is to adjust the retiming_OR to arrive at the CS
input of the TS at least 20 ns after the T1 input (to allow for the
T1 to shift due to proton flight time). More would be comfortable.
Of course we must insure that the width of the T1 out of the gate
generator accomodates the delayed CS. At this point the TS can then
be run in strobed mode and we are ready for WC commissioning.
-- John R. Calarco Dept. of Physics Univ. of New Hampshire Durham, NH 03824 phone: (603)862-2088 FAX: (603)862-2998 email: calarco@unh.edu
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