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This update provides information on the progress of Run 9 at RHIC, including the cooling down process, beam injections, ramp development, and the transition to 200 GeV. It also discusses the need for machine studies and the upcoming maintenance day.
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Run 9 polarized proton Log • 9 Jan begin 45 degree cool down from room temp (3 MW-NEW) • 2 Feb, Cool-down to 4.5 degrees begins • 5 Feb, Blue ring cold but still stabilizing • 7 Feb, beam injected into Blue ring, • 8 Feb, Yellow cold but still stabilizing • 9 Feb, 2 week “Setup” mode begins(0.5 weeks early) • 13 Feb, Beam injected into Yellow ring • 14 Feb, STAR magnet on, ramp development begins • 17 Feb Nov, First collisions @ s = 500 GeV (2.3 weeks into run – a record!) • 24 Feb, “Ramp-Up” mode begins, overnight stores for experiments • 6 Mar, Machine in “Physics” mode, integrated lumi begins • 16 Mar, Spin rotator ramps established, longitudal polarization available • 17 Mar Experiments in Physics mode • 13 April (0800), end s = 500 GeV physics (3.9 weeks), begin new low level RF setup • 14 April (0000), Last s = 500 GeV beam development, Maintenance • 14 April (evening), begin setup for s = 200 GeV • 21 April, s = 200 GeV physics begins with further ramp-up • 28 Jun, Run 9 ends (9.9 weeks s = 200 GeV physics) , cryo warm-up begins • 30 Jun, cryo warm-up ~complete, 21.3 weeks cryo operation
Through store 10494 (6 Apr) ~Phenix goal (25 pb-1 recorded) with longitudal polarization ~Star goal (10 pb-1 sampled) with longitudal polarization Experiments start for physics with longitudal polarization 50 % polarization assumed
Sun 4/5/2009 2:23 PM email Dear All, This is an update about the rest of Run 9. First, we have now finally received our official FY09 RHIC operations budget, and it will indeed support running through the end of June. So we will have a long 200 GeV run, and you should inform your collaborators that they will need to sign up for shifts if they haven't already done so. As for the switchover to 200 GeV, I discussed a possible plan with Barbara and Ed at Quark Matter on Thursday, and this plan should be up for discussion at Tuesday's planning meeting, if not before. The plan calls for terminating physics data collecting at 500 GeV either at midnight on Sunday, April 12 or 8 am on Monday, April 13. If by that time we still have open the critical questions regarding maximum luminosity the experiments can stand at 500 GeV, then it worth devoting 2 days to machine and experiment tests to answer these questions as well as we can. In this scenario, we would complete critical machine tests and make the switchover to 200 GeV in conjunction with the normally scheduled maintenance day on Wednesday, April 15. Among critical tests are operation with larger beta* at PHENIX, to see if one can find a more effective combination of luminosity and background, and perhaps similar tests at STAR to see if the TPC current and trip rate can be affected by beam setup. We will need to address these questions in planning the rest of the 500 GeV pp program after Run 9 ends. There are clearly other issues, as well, such as the rate-dependence of the CNI polarimeters, but we probably have enough information already to think about improved electronics design after Run 9. In any case, we can reserve Monday and Tuesday, April 13-14, for any studies we determine are critical to planning the rest of the 500 GeV program. I will be at Fermilab on Tuesday, but am eager to hear the results of discussion of this plan. Of course, if some critical questions are answered before April 14, we can push up the maintenance by a day or two, and start the 200 GeV switchover a bit sooner. Cheers, Steve
Mon 4/6/2009 7:26 PM email Steve, unfortunately I cannot attend Phil's meeting tomorrow, but I would like to make the following comments: Luminosity: We cannot simply raise the luminosity by a large amount. We can, as we have done over the weekend, increase the bunch intensity by small amounts. We are probably close to some limits already. Background: By and large we do understand how the experimental signals scale with the beam loss rate or luminosity. There are a few smaller tests that can still be done (taking out one beam, for example), which are planned. Polarization: We do not really understand the polarization loss on the energy ramp. Very likely these are related to the orbit control, and multiple high resolution ramp polarization measurements can help us understand these issues. These studies should have the highest priority, above luminosity or background studies. Wolfram
Tue 4/7/2009 12:02 AM email Hi Wolfram, Thanks for the comments. Obviously, those who are closer than I've been to the machine issues of the last week's performance and the current situations at the detectors should decide on priorities for final 500 GeV machine studies. The main point of the proposal was simply to offer a possibility for 2 final days of dedicated machine studies after the finish of 500 GeV physics running, with the regularly scheduled April 15 maintenance day as an absolute deadline for the changeover to 200 GeV. If some of the relevant machine studies can get done before next Monday, then we can switch a couple of days earlier. I do expect our strategy for completing the 500 GeV spin program, in light of what we learn from this year's run, to be among the topics that get emphasized at the July RHIC S&T review. So we should do our best to understand likely performance limits on the figure of merit achievable in future 500 GeV runs. Steve
Mon 3/30/2009 7:31 PM email, 1/2 Dear Barbara, Nu, Bill and John, I will be at tomorrow’s Time Meeting, but then have to leave to catch a plane to Quark Matter before the weekly planning meeting. I will also miss next week’s Time and Planning Meetings due to a commitment at Fermilab. Thus, I would like to get the most pointed information possible in order to make a likely remote decision regarding the changeover from 500 to 200 GeV. We are likely under any scenario to move the changeover at least from Friday April 10 to first thing Monday morning April 13, to allow one final weekend of hopefully productive 500 GeV data. (I will be back at the lab on April 9.) But in considering possible elongations of the 500 GeV running, and after detailed discussion with C-AD regarding conditions today, I would ask that you consider the following issues and, if possible, present your collaboration’s take on them either tomorrow or a week from tomorrow. 1) I place the highest priorities for this first run at 500 GeV on the following: (a) demonstrating that one can accelerate to 250 GeV without further depolarization of the beams (this is essentially already done, although we do want a 500 GeV polarimeter calibration); (b) demonstrating observation of a clear W peak above background after reasonable cuts; (c) taking measurements with the machine and detectors that will allow us to plan for more effective 500 GeV running in future runs. 2) There is little chance to reach the 25 pb^-1 sampled that PHENIX set as a goal for this 500 GeV run. What is the minimum integrated luminosity needed at each detector to see a clear W peak (even if this is insufficient to get a publishable cross section paper out of this run)? Will you be able to show a W peak from fast offline analysis during the 500 GeV running? 3) Are you willing to sacrifice luminosity for improved background conditions, to improve the chances of seeing a clear W peak? If so, what is the preferred improvement: increasing beta* (possibly shifting the background problem from PHENIX to STAR) or reducing beam intensity out of the AGS (possibly improving the beam polarization slightly)? It is not clear there is much further improvement to be gained in beam lifetimes (aside from the occasional blue beam emittance blowup problem that still shows up in some stores), which are now no worse than those seen at 200 GeV.
Mon 3/30/2009 7:31 PM email, 2/2 4) Right now, the limitations on luminosity are being imposed by the detectors, rather than by the machine. We need to understand if we will see the same limitations in future runs. At the very least, we need auxiliary measurements that will determine answers to the following questions: (a) Does the rate limit imposed on background at PHENIX, via scintillator paddles outside the shielding wall, correspond to the same detector subsystem currents at 500 GeV as at 200 GeV? Can this correspondence be recalibrated in the next 10 days? (b) Do the current trips experienced by the STAR TPC impose a fundamental limit on 500 GeV luminosity? Are there measurements STAR can make to address this question? (c) Is there more background at 500 GeV in the detectors due to higher energy spray from the beam leaking through the existing shielding? (I hope that can be answered from simulations.) Is there space to make the shielding thicker, if this would help? (d) Can STAR determine how much of the TPC current is from real collisions vs. beam background? 5) It is unclear at this point that we will have the 9 MHz cavity operational for this run, and there is a danger that the spin flipper could be ready only for the final several weeks of the (extended) run. Do these issues affect your collaboration’s judgment regarding the split between 500 and 200 GeV? 6) Would you suggest additional critical auxiliary measurements to determine how to improve performance in future 500 GeV runs? Solving the AGS emittance blowup and polarization loss problems at high bunch intensity would be nice, but may not be critical if detector performance already limits us from increasing luminosity from the present levels. Obviously, any additional information you think is critical for a decision about the switchover is also welcome. Thanks, Steve
First overnight store at s=500 GeV • 56 x 56 bunches • b*=0.7 meters
RUN6, 111 bunches b*=1 m 1.35E11/bunch Scaling to s=500 Rate=15* 15 KHz
First overnight store at s=500 GeV • 56 x 56 bunches • b*=0.7 meters
