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User name gilman,reitz
Log entry time 11:50:45 on August 2,2001
Entry number 68612
This entry is a followup to: 68603
keyword=g2 helicity setup
As Bob noticed, I had indeed mis-wired up h+ and h- in the counting house last night so that they were backward.
We changed the counting house LeCroys to be consistent with the proposed revised
setup in halog 68603.
We changed the left/right spectrometers to Phillips to prevent the glitches when
the inhibit goes off at start / stop on runs. One fine point on this: with the LeCroy it is
okay to start on signal and stop on logical complement. With the Phillips,
because apparently the reset (stop) goes false within ~ns of the trigger (start)
going true, it does not catch the transition and it does not fire. We solve this problem
by using out-bar to trigger a g&D channel set to 100 ns width, and this delayed
output to stop the latch. Thus, the latched signals in the spectrometers are
~100 ns longer than the signal width set in the counting house.
Aside from ~ ns effects from different cable dispersion, and the reset (stop)
delays for the Phillips, all the gate widths on both arms should now be the
same, though there appear to be variations at the level of ~10 or 20 us in
any individual gate width.
Bodo and I also checked for the 650 - 900 us both false width change, we do
not see it. There *may* be (it is hard to tell) systematic variations at the level
of 5-10 us of that ~650 us when going (h+ -> h+) vs (h+ -> h-) vs etc etc.
DAQ test of time symmetry is needed.