run status 7-27-02

From: Tancredi Botto (tancredi@mitlns.mit.edu)
Date: Sat Jul 27 2002 - 14:40:58 EDT


Hello Blasters, and people on shift for next 12 hrs.

After fixing the arrival time of the start counter signal we finally see
the left side protons, as expected. However it should be made clear that
in our study of the L/R simmetry the start counter is just a nuisance.
and doesn't need to be tuned in (if possible, should be taken out!)

>From what I recall the s.counter is 1/4" thick (30 MeV punchthrough for
protons). In addition, the chamber plates add another 1/8" of plastic
(but symmetrically L/R). For the right side we then have a higher energy
threshold. To be on the safe side I estimate that for the right sector we
need protons of at least 90 Mev, while 60 MeV should be fine for left sector.

In this range the cross section changes by more than a factor of two (!),
which explains why we (now) even see more protons from the left than the
right (before we had very few on the left, some on the right). This is the
kinematics for the present situation:

theta_e = 25 deg theta_q=67.1 deg T_p = 66.5 MeV (ds/dO = 1.9 ub/sr)

theta_e = 30 deg theta_q=62.9 deg T_p = 92.0 MeV (ds/dO = 0.7 ub/sr)

I changed the trigger to allow for more backward e- angles. We know use
e- paddles 2-5 in coinc with one paired-OR proton paddle (12,13 - I always
count from 0). It is reasonable to expect an asymmetry for elastic events
hitting the first 2 electron paddles. It should go away as you move
backwards. This is the focus for today's analysis (chris, tavi, ... ?)

The start counter is in X mode (so its timing won't matter at all,
although we understand it should be fixed now, although using the start
coutner forces an asymmetric trigger). Data should be taken also with
start counter = 1, but mostly for the purpose of improving the ratio of
target/background events. Adding the next pair of proton tof's increase
the rate only very marginally (about 5 %) so you don't need that to do
things quickly.

In a second part of the program focus on one e- paddle and use at least
the last 3 paired OR proton paddles to study how events multiple scatter
away (maybe talk to john C. before doing this).

The trigger rate is 100 Hz at injection (74 mA) and coda can handle that
comfortably. Also, I downloaded high ADC thresholds for ADC7 in ROCr (not
used) which decreases the event size by about 30 %

Please keep production and analysis happy. Also, your analysis should
be able to say something about the Cerenkov efficiency (with john we agree
to keep x's there and do everything in software).

If succesfull, tomorrow morning we can move the start counter to the left
for a cross-check of our results. Please communicate your results,
also in the logbook, else you may be woken up at 8.00 am. Leave your
phone number too).

Finally, the trigger goes to CS mode. If time will allow I plan to also measure
without the start counter (that part will move first if by tomorrow morning
we don't understand this asymmetry) and finally do some coda tests (chamber TDC
sparsification, communication with ROCr, measure rate vs event size).

regards,
tancredi

________________________________________________________________________________
Tancredi Botto, phone: +1-617-253-9204 fax: +1-617-253-9599
research scientist MIT/Bates, 21 Manning Av Middleton MA, 01949
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