Minutes of the Hall A Group Meeting April 27, 2010

1)  Run Report (Aidan Kelleher):
a)    PREX took production data on 208Pb and 12C
b)    Various auxiliary measurements done: Q^2-measurement, Compton, 
      GEM commissioning, DAQ timeing, etc.
c)    17C collected (proposal goal: 130C)
d)    Main problems: Non-statistical noise due to non-uniformity of Pb
      target foil. Will try to fix by synchronizing the raster to the MPS

2)  Near-term schedule (Kees et al.):
a)    Beam off Friday 8am for the Open House
b)    Hall A proper will stay closed for the Open House due to high radiation
      levels. A tent will be set up outside. John LeRose is coordinating
      displays.

3)  Rad Watch briefing (David Hamlette):
a)    Whole body radiation dose rates near the Hall A target currently 
      exceed 1 R/hr
b)    Legally required to implement "physical controls" to prevent
      unauthorized access
c)    Implement requirement by continuous surveillance of High Radiation Area
      by designated "Rad Watch" personnel
d)    RWP describing details is available in MCC control room
e)    For short accesses (e.g. refilling Moller), the ARM acts as
      Rad Watcher.
f)    For longer, multi-purpose accesses, Hall A will provide a designated
      Rad Watcher.  Anyone so designated must be briefed and sign the RWP.
      This is only necessary once.
g)    Discussion ensues regarding other consequences of high radiation
      levels.
i)      At some point, the entire hall may become a radiation area,
        requiring stricter access controls (RWP with specific task list)
ii)     May take several weeks to "cool down" sufficiently, affecting DVCS
        installation plans

4)  Installation (Ed Folts):
a)    Cryo upgrades
b)    APEX target mechanism
c)    Bogies upgraded
d)    Q1 power supply shielding

5)  Magnets (Javier Gomez, Jack Segal):
a)    Q1 is slowly drifting (concern for experiment - unpredictable optics)
b)    Jack is investigating

6)  Moller (Jixie Zhang):
a)    Did two Moller commissioning runs, April 17 and 22.
b)    Alignment checks show deteriorating alignment between two run periods.
      To be investigated.
c)    Problems at end of April 17 run traced to unstable beam.
d)    Quad scans done on April 22.
e)    Increased DAQ rate capability.
f)    Need to run Monte Carlo to get target analyzing power.
g)    Tested raster effects. Not yet understood.
h)    Successfully ran Moller DAQ with 240 Hz helicity reversal rate.
      However, no software is available yet to analyze the 240 Hz data.
i)    Paul Souder remarks that 240 Hz Moller running is not needed for PREX.
j)    Next Moller run Wednesday or Thursday this week.
k)    Added Moller page to Hall A Wiki.

7)  Alexandre Camsonne reports:
a)    DVCS preparations.
b)    GEM commissioning.

8)  Bogdan Wojtsekhowski reports:
a)    Reminder: Exclusive Rections workshop at end of May (starting May 17).
b)    APEX pilot run preparations:
i)      Target drawings done at SLAC, parts ordered
ii)	Target lifter designed at JLab, parts ordered, ETA early May
iii)	Detectors: waiting to install VDC amplifiers cards
c)    SBS project:
i)      Sub-groups formed
ii)	Milestones being formulated
iii)	Lab space requirements [for assembly] being assessed

9)  Sirish Nanda reports:
a)    Compton cavity performing well
b)    Planing beam tuning and scanning for later this week
c)    Paul Souder inquires about plans for installing shielding
      [to address background problems]. Tentative plan is to build a
      lead hut this coming weekend, enclosing 80+% of the detector

10) Software (Ole Hansen):
a)    GEM tracking code for PREX: adding features to deal with detector
      imperfections (dead channels, incomplete clusters)
b)    High-rate VDC tracking for APEX:
i)      t_0 fit routine (non-linear fit) implemented. Slow, but mostly
	working. Needs some more debugging.
ii)	Cluster matching algorithm implemented, to be tested
c)    SBS simuations
i)      GEANT4 simulations making good progress at INFN
ii)	Track reconstruction code (based on PREX GEM code) under
	development. Algorithm for interpreting/fitting 3-sample data
	from APV25 front-ends needs to be devised.
iii)  Kees inquires whether GEANT4 has known limitations regarding
      modeling of low-energy processes.  No one knows with certainty offhand.
      Will be followed up.

11) Doug Higinbotham reports:
a)    Re upgrades of LeCroy HV crates
i)      Software done (Brad Sawatzky)
ii)	Waiting for more hardware to arrive.
b)    Bogdan inquires if cEPCIS control of HV in the HRS-R, which has not
      been available for several years, can be restored using the new
      hardware.  To be determiend.

12) Other issues:
a)    Javier Gomez remarks: JP Chen and Paul Brindza have concluded that
      the cryo load during DVCS may get too high for the present configuration
b)    Kees de Jager responds that the DVCS collaboration needs to decide which
      polarimeters the experiment needs. Only after this decision has been
      made, the cryo requirements can be evaluated.