Minutes of the Cooler-CSB Group Meeting

February 12, 2002 - (EJS)

Present: Chris Allgower, Andy Bacher, Chris Lavelle, Hermann Nann, John Olmsted, and Ed Stephenson

LUMINOSITY DETECTORS

A design for scintillators to measure the luminosity by observing d+d scattering near 45 degrees in the lab has been completed and put into the shop. The design has the features:

• The scintillators fit just outside the windows on the left and right sides of the target box, and have light guides that go upward to PMTs that will be above the Pb-glass arrays. There seems to be sufficient clearance that no machining or detector repositioning is needed in the Pb-glass arrays.
• The scintillators are cut to make sharp edges in theta. Each scintillator will be divided into two parts along a diagonal that changes the depth of the scintillator as theta increases. One depth will go up and the other down so that the relative pulse heights will indicate position.
• The two halves will be displaced in opposite directions vertically so that single scintillator hits can be interpreted in terms of a vertical displacement of the beam spot.
• The two scintillators will glue directly onto 1/4-inch thick light guides that are between 25 and 29 inches long. Each will be bend away from the target box to remove interference between the PMTs and the pumping above the target box.
• For the calibration, the 45 degree detectors will observe the protons from d+p scattering while the deuterons are detected near 25 degrees with separate detectors. These detectors will be placed only for calibration purposes while the Pb-glass arrays are rolled back.

We plan to keep the silicon for one more round, moved up as far as possible.

ENERGY LOSS CALCULATIONS

We have come to some agreement about the materials and thickness list for energy loss calculations.

Time spectra for the four delta-E(1) sections overlap as they should with no adjustment. John will look at correlations with X and Y position, as well as pulse height in the scintillators, to make sure that there are no other systematic effects that need to be considered.

Using the energy loss calculations as a basis, a fit was made to connect channel number in TOF with the z-component of momentum. From this and the MWPC-1 position, x and y components can be inferred and missing mass calculated. With no event selection, a long low-mass tail is present. Choosing just events in the p + d -> 3He + pi0 group shortens this tail. A further kinematic cut on radius (in MWPC-1) and p[z] translates into sharp limits on missing mass. The time and missing mass resolution is comparable, but perhaps somewhat larger, than results obtained last May.

SMALL ITEMS

We still need to check the calibration of the beam position monitors.

This would be a good time for a long cosmic run so that cuts on straight-down cosmics will have enough statistics to be useful.

We need to check on the parts to make the terminator strips.

We discussed thresholds on scintillators, noting that for this past run the thresholds were rather low through the system.

NEXT MEETING

There was a call to have a run plan draft for the next meeting. The run begins March 6 and ends the morning of March 18. The Krisch run will finish the morning of March 4 (Monday). There is one day of scheduled access. Given that we will need to install and align a luminosity system and replace the delta-E(1) detector, one day may not be sufficient. The first day of beam was to be for tuning and additional development of intensity. This may be delayed until Wednesday, depending on work in the Cooler. We will start with polarized beam (PINTEX is presently running with about 100 micro-A.) and switch to unpolarized if the intensity is not high enough. Due to problems with the deuteron polarization, the first development time contained no opportunity for intensity work.

Submitted by
Ed Stephenson