Minutes of the E895 meeting Graduate Chemistry Rm 412, SUNY Stony Brook Monday 8/21/95 Attending: DC - Daniel Cebra RM - Bob McGrath MJ - Marvin Justice SG - Steve Gushue MG - Mark Gilkes HH - Hiro Heijima HL - Heng Liu AJ - N. Ajitanand PC - Paul Chung JL - Jerome Lauret TM - Tatiana Magda EL - Erwan LeBras Daniel Cebra described the events of the past week. TPC: ==== The cathode plate has been installed. We ran dry nitrogen through the TPC for a while, and then powered up the cathode to 10 kV. No problems - the current in the resistor chain was normal, and everything checks out. The nitrogen and P10 lines are a concern. We have been discussing our nitrogen needs with the MPS people. SG - The conclusion is that a nitrogen Dewar will be hooked up for the laser and electronics bays. DC - I intend to settle the question of our precise flow rates with the experts, Eric Hjort and Howard Wieman. Cable trays are now being laid between the boom arm and the control room. The stick power supplies need to be moved closer to the TPC. The length of the cable run for the stick power cables is a concern. SG - One could lower the cable tray on the boom arm itself, to gain 1-2 ft at either end. DC - I wanted to take the fence out. Larry Toler prefers moveable power supplies (i.e. wheels on the stick power racks). This may mean that we would need 2 extra feet of slack. Typically, once the cables are strung and working, we don't need to touch them again. SG - Is the cable length tight once the TPC goes into final position, or just while inside the tent ? DC - It's tight in the tent. There are a few feet of slack when in position. The major concern, though, is when we're actually moving the detector. At that time, we'll need all the extra slack we can get. SG - We don't need to have the cables so high on the boom arm. Could gain six feet, if they weren't that high. DC - We have to think about this and decide pretty soon. The cables are very heavy. The boom arm controls them. DC - We need to ensure that the rails can provide the degree of flexibility that we'll need in installing the TPC. We need to interface with Joe Scaduto. MG - Do we intend to use the same claws ? DC - Maybe not. The existing claws may not give us the necessary vertical reach, as the MPS pole gap is wider. LASER: ====== DC - I am still negotiating with the safety personnel. DC - The laser placement also has to be determined. At the Bevalac, the TPC was installed from the opposite side of the magnet from the laser. Now that they are on the same side, there may be other difficulties. MAGNET: ======= HL - Magnet mapping at 1.0T starts tomorrow. The shifts will be from about 6:00 pm to midnight. It should take about 20 hours. The cooling towers for the magnet have been repaired. MJ - (shows the magnet map contour plots). There is a larger uniform region at 0.5T. SG - Which is to say that at 1.0T the iron is saturated. MJ - The 0.75T map is relatively flat too. It may be a good compromise. RM - Why the new maps ? DC - We decided that we needed more fringe field measurements, especially upstream near the beamline. MUSIC: ====== Jerry Chance and Jim Draper have unloaded all the MUSIC hardware and are working with Joe Scaduto on a new mount for the detector. They are reassembling the MUSIC gas handling system, and will soon start electrical tests on the field cages. SOFTWARE: ========= MJ - Telnetting in/out of the control room computers is now ready with the appropriate nameserver support. The router has been reconfigured so that Columbia can download software and talk to the processors without having to come to the lab. We'll get the FORTRAN compiler so that the run control program can be started up. MJ - We need a home page for E895. HL - I volunteer to set one up. MJ - We need a site for the overall software. Some work on tracking is underway. It would be nice to advertise this in a Web page. Some discussion followed regarding the experimental configuration. DC - It would be nice to have the acceptances for pi+ and pi- equal. SG - One could choose different beam angles, or flip the polarity of the magnetic field to equalize the acceptance, if the physics justifies it. Actually, this is a problem for safety reasons, since with the polarity switched the beam curves towards the control room. DC - I'd like to flip the polarity with beam off to look at the distortions. But with the quality of the field represented in these maps, it may be a moot point. MJ - We could also flip the TPC upside down. DC - We should get beam angles and intersection points at the target for all beams and field settings. MG - I will have these at the next meeting. MJ - We need to do some physics simulations to study the effects of acceptance and efficiencies. Effects on diffusion when the field is changed. Effects on the momentum resolution. We will need to run the slow simulator to understand these effects. What's best for flow may not be optimum for strangeness. RM - Isn't it true that benchmark results need to be obtained from comparisons to EOS data, before detailed work can be done for E895 ? MJ - We need to understand the two-track resolution. If the slow simulator can match the EOS data we might have confidence to extrapolate to a different field, and then use it to tune the parameters of the fast simulator. The two-track resolution will be an issue as the multiplicity goes up. MJ - Also, we need to study changing the gain, i.e. the anode wire potential. Raising this would produce more 2-pad and 3-pad hits - more information. The problem has been that the wires have a tendency to trip off. DC - When Joe Scaduto puts in the rails, we will be constrained, well before the detailed simulations are done. MG - The fast simulator results will be ready by next Monday. We should have enough information for the TPC placement. DC - We want to fix the TPC position in the magnet by next week. But the questions of beam energy and field could be prepared for the E895 collaboration meeting. TARGET ASSEMBLY: ================ There was much discussion about different options for the last section of beam pipe, centering on the possibility of getting a 4-inch pipe into the re-entrant. MG - I am leaning toward a manual target wheel, turned by someone in the magnet close to the TPC, rather than a remote motorized scheme. It's simpler and we aren't going to change targets that much. SG - The magnet will have to be off for this. A safety issue. DC - If it's a safety issue, that argues for a remote solution. SG - Turning the MPS magnet off and on is a lot quicker than if it were superconducting. Although sometimes it has been known not to come back on. SG - We could make the window on the pipe into a target. Then you'd have to let that section up to air to change targets, but that's a simple matter. The only problem is that you would not have a real target out (even though a thin mylar window is close). Prepared by: Mark Gilkes