[Halla_parity] PREx Status report 3/27/2010

[Dustin McNulty]

Dear Collaborators,
The PREx commissioning effort is steadily progressing.  Here is a list of
accomplishments from yesterday:

--We achieved full raster-size capability with Bill Gunning's help. 
Although there are still some lingering questions here.

--The problem with the target mover system is now fixed.  Dave Meekins
replaced a faulty limit switch.

--Bob et al. with the help of MCC achieved a beam configuration that can
consistently deliver a very low (2 - 10nA) beam current by adjustments in
the slits and attenuator.

--We finalized our pulse-height distributions and alignments for the main
and A_T quartz detectors for this particular HRS tune.

--Formulated a robust strategy for positioning the A_T detector optimally.

--Examined focal plane spectra and relative rates between 4 targets: 9mg
C, 442mg C, 55mg Pb (thin Lead), 122mg Ta.

--Examined Lumi widths and found them consistent with the expected rates.

--Plugged quartz signals to parity 18bit ADC and had first look at widths.
 Here we what to use thick Carbon target elastic peak rate for 100uA as a
benchmark to set det HV and ADC gain to give the proper response (200,000
adc channel means) for 50uA on thick Pb.


At this point in the run plan (2am today), the beam broke and we are
currently waiting for its repair. The problem was just recently
pin-pointed and the fix is underway.  MCC informed us that the fix will
require several hours (at least 4 hours).  The problem was with an
injector chicane dipole.

When we get the beam back we will pick up where we left off.  Here is a
quick list of run plan items to work on over the weekend:

--Finish study of main detector integrated DAQ signals (setting det HVs)
--Thick Lead target commissioning now that the raster works.
--Take pseudo parity quality data...using thick Lead target at 50uA. 
Start up the WAC analysis machinery and start to look at all the standard
plots--det widths, blinded asymmetries, BPMs, Lumi,...
--Testing new tunes for the HRS--exploring the requirement that the
collimator defines our acceptance and not Q1.
--Re-evaluating main detector alignment and pulse height distributions for
the new tune.
--Testing/commissioning the new dithering system.  This requires an ATLIS
(in the works) and so will likely wait until after the weekend.

Cheers,
Dustin


Dustin McNulty
office: CEBAF Center A102
        (757) 269-5023
Postal Address:
12000 Jefferson Avenue, Suite #4
Newport News, VA, USA, 23606