Present:
Chris Allgower,
Andy Bacher,
Chris Lavelle,
Hermann Nann,
John Olmsted,
Tom Rinckel, and
Ed Stephenson
SCHEDULE
The draft Cooler machine schedule calls for a short run that begins with development on Wednesday, May 8 with beam delivery to the experiment starting Friday, May 10. We would use this time to check any changes or improvements to the setup. If all looks well, we would try the HD gas calibration of the luminosity monitors. The run has to end by Tuesday morning, May 14 to allow for the switch from unpolarized to polarized beam. The PINTEX group would then use the beam.
We would begin a longer production run with a machine tune on Tuesday, June 4. This run is tentatively marked to extend until Monday, July 1.
There is no final word at this point on plans for another run with the Michigan group. Whether we take a second long production run also depends on how well the first one goes. So the machine schedule will be left open for the month of July.
Unless there are objections (none are known at this point), this schedule will be published this week.
RESCALING THE CHANNEL
The preliminary analysis shown last week had alpha particles hitting one end of the X3 chamber. Studies were made almost a year ago of the sensitivity of position on X3 to changes in the field of the septum magnet. Because of the focussing in the quadrupoles, large septum field changes are required in order to move this distribution. After some concern about which way X3 readout channels run in real space, we decided that the correct direction is to lower the field by 8.5%. This changes the magnet set point from 1121 A to 1016 A.
MAGNETIC SHIELD FOR THE 6-DEGREE MAGNET
We discussed making another layer of 1/4-inch steel that would fit around the outside of the present shield with a 1/4-inch gap. On the beam-right side, this can probably be accommodated with only minor changes to the Pb-glass stand. On the left side, things are very tight. Tom's plan is to order the large steel sheets cut to size. We would then drill and mount them.
[Tuesday morning we inspected the setup and decided to make one more try with a smaller piece of steel placed between the Pb-glass and the magnet before going ahead with the order for large pieces.]
PICTURE FILES
Several sets of pictures of the setup now exist. We should get these gathered into some central place where they are available to all.
MOVING THE JET TARGET
During the run, we found that the overlap of the beam with the jet required that we move the beam with the flattop combo about 5-6 mm toward the outside of the ring. This raised the question of whether we want to actually move the jet so that it will overlap better at the position where the beam was finally tuned. At present it is reasonably (< 0.5 mm) centered in the target box. This motion would require us to also move scintillators. The effect on the separation between the beam and the alpha cone in the channel is unknown. We decided to consult with Bob Pollock for further information.
CUTTING BACK ON STAINLESS STEEL STAGE-2 BOX
At present, 45-degree scattering from the target leads through the edge of the 50-mil portion of the stainless steel box that surrounds the stage-2 vacuum region. This can be removed, if one is careful to catch fragments from the cutting. It was decided to look into the issue in software before making a final decision.
DEUTERIUM
Two bottles of deuterium gas have been ordered.
LOOKING AT GAMMA RAYS
A first version of the Pb-glass hit file has been sent to Hal Spinka for inspection. Some anomalies with the scaler counts were noted. [A new file has been sent Tuesday.]
PILEUP
The first pileup check comparing harmonics 1 and 6 showed changes of about 0.1% on pileup percentages that ranged from 2.0% to 3.6% on delta-E1 scintillators A through C. We decided to try at a pileup group closer to the alpha group.
[This was done by Tuesday. Improvements are about 20% of the amount of pileup in going from harmonic 6 to 1 (Yup! The wrong way!). We should be operating on harmonic 1.]
PB-GLASS TIMING
We all endorsed getting this done.
LUMINOSITY CONSISTENCY
It is still the case that the luminosity recorded by the forward scintillator-silicon system is about a factor of 3 lower than that from the 25-45 degree scintillator system. Issues raised include: