- Nuclear & Particle Physics
- Isotope Research & Production
- RIKEN BNL Research Center
News From Associate Laboratory Director Steve Vigdor
January 21, 2010
I would like to bring you up to date on several recent events with implications for RHIC and its future: a revision to the Run 10 plan for low-energy Au+Au operations; a visit to BNL and RHIC from the DOE Undersecretary for Science Steve Koonin; the second meeting of the international Electron-Ion Collider Advisory Committee; and a spate of serious safety incidents that have occurred at BNL during the past year or so.
Revised Run 10 Plan
The cooldown and beam commissioning stages of RHIC Run 10 are now well under way, and proceeding on schedule toward a start of physics running before the end of the calendar year. At the RHIC Planning Meeting on Nov. 24, 2009 we had a good discussion of priorities for the start of a low-energy scan in Run 10. This discussion was prompted by two new facts revealed in the preceding weeks: (1) we received an FY10 RHIC budget from the Office of Nuclear Physics that will support at least 25 cryo-weeks of operation in FY10, with a possible extension to 27 weeks if the BNL overhead rate is not raised from its present level (a possible increase is under consideration at the lab); (2) a reanalysis of PHENIX data taken during the √sNN = 9.2 GeV Au+Au test run at the end of Run 8 has revealed that PHENIX can indeed trigger successfully and reconstruct events at energies below the RHIC transition energy, without the addition of new trigger detectors. The latter information renders invalid the premise (namely, that PHENIX could participate at the lowest energies only in Run 11 or beyond) of the tentative run plan I proposed last summer.
The highest priorities for Run 10, as set down by the PAC in June 2009, remain 10 physics production weeks at √sNN= 200 GeV and an additional 4 physics production weeks at √sNN= 62.4 GeV Au+Au, while the Hadron Blind Detector remains installed in PHENIX. (Its removal to permit installation of the VTX upgrade is planned for Summer 2010.) Allowing for overheads of 2.0 weeks cooldown, 2.0 weeks collision commissioning at 200 GeV, 0.5 weeks cumulative for subsequent energy changes and 0.5 weeks for warmup, we will have a total of 6.0 weeks remaining for a start on the energy scan in a 25-cryoweek run, growing to 8.0 weeks in a 27-cryoweek run. Of these, I would like to devote 0.5 weeks (to be complemented by dedicated Accelerator Physics Experiments during the regularly scheduled APEX periods) to machine studies important to RHIC’s future program: a test of beam stability near a betatron tune of 0.67, as needed for improved polarization transmission to 250 GeV in subsequent pp runs, and in the wake of improvements made to the main magnet power supply during the shutdown just completed; a first test of feasibility of providing Au+Au collisions at √sNN as low as 5 GeV.
The remaining 5.5-7.5 weeks is insufficient to complete an energy scan. Thus, the question at hand is what aspects of the energy scan to emphasize in this first run, with the understanding that additional low energies can be part of a Run 11 plan. The plan I propose below has the advantage that it provides the opportunity to have significant impact and publications from Run 10 at both the low-energy end of the scan, where STAR is focused on searching for the QCD critical endpoint, and at the intermediate energies, where PHENIX hopes to find clear evidence for the onset of jet quenching and other phenomena associated with the QGP transition. Thus, 4 weeks will be devoted toward the end of the running period to Au+Au collisions at √sNN = 7.7 GeV. While PHENIX estimates that they would accumulate only around 0.5M events during this run, there no longer seems to be any reason to anticipate that this situation will improve by waiting a year. Low-energy electron cooling of the RHIC beams, which would improve the luminosity at the lowest energies, is at least five years off and only worth considering for a second-generation low-energy scan. The beam top-off mode that had been discussed at the June 2009 PAC meeting is hard to reconcile with safety considerations at the low energies, where beam is lost at an elevated rate. And the addition of the PHENIX VTX detector is unlikely to increase the PHENIX event rate significantly at the low energies, given that it will require much tighter vertex cuts out of a large diamond size. Furthermore, C-AD accelerator physicists are confident that 7.7 GeV is a sufficiently small step down from the already demonstrated 9.2 GeV that there is a high probability of successful RHIC operation in this first attempt at 7.7 GeV.
We will devote 1.5 weeks to a run at √sNN= 39 GeV, providing sufficient statistics for PHENIX to see if there is a sharp onset of jet quenching between 22.4 and 62.4 GeV, and more than enough statistics for STAR to compare observables to those at other energies in the scan. The 39 and 7.7 GeV runs will be included in a 25-cryoweek run. If the run can be extended by two weeks, my best guess (informed by PAC advice) of the largest potential impact of those extra weeks is to devote them to Au+Au collisions at 11.5 GeV, even though collisions can be provided to only one detector at a time at this energy. Since STAR has the much larger acceptance at the low energies, the collisions would be arranged at STAR. The remaining energies from the PAC-recommended scan -- √sNN = 27 and 18 GeV – could then be scheduled in Run 11, although that plan can certainly be amended by results revealed during Run 10.
In summary, the table below shows the revised plan for 25 or 27 cryo-weeks:
| ||Physics production or beam studies weeks|
|√sNN (GeV)||25-cryoweek run||27-cryoweek run|
|11.5 @ STAR||0||2|
|Beam studies @ 5 GeV and @ n» 0.67||0.5||0.5|
Steve Koonin made his first visit to BNL since being named Undersecretary on Nov. 24, 2009. There were detailed discussions during the day covering many aspects of BNL’s research plans for the coming decade. Given Koonin’s intended focus on research related to energy and climate change, those were some of the natural topics of emphasis. But the Undersecretary also spent a good amount of time visiting the STAR detector site at RHIC, and discussing ongoing and future nuclear physics research in some depth. In particular, he showed deep interest in recent science results from RHIC (especially the hint of symmetry-violating high-temperature QCD vacuum fluctuations from charged-particle correlations studied in STAR), in technical details of the detectors, and in the scientific motivation and plans for an Electron-Ion Collider, at both BNL and JLab possible sites. Koonin is part of an exceptionally strong science team in upper management positions within DOE (Steve Chu, Steve Koonin and Bill Brinkman have now all visited BNL within the last year), and it was a pleasure to cover a lot of ground very rapidly, but still in significant depth, with him.
The second meeting of the international EIC Advisory Committee (EICAC) established by Sam Aronson and Hugh Montgomery was held Nov. 2-3, 2009 at Jefferson Laboratory. (The next meeting will be held on-site at Brookhaven.) Very substantial progress had been made since the first meeting in February 2009, especially on fleshing out accelerator designs for first-stage facilities at either BNL or JLab, but also in beginning detector and intersection region (IR) lattice designs and in furthering simulations of science performance and needs. The EICAC was positively impressed by the progress, but also stressed again how much work remains to do. We are currently awaiting the Committee’s report from the November meeting.
In preparations for the meeting, we at BNL went through a detailed bottoms-up cost estimate for much of the machine design for MeRHIC, the first medium-energy stage that would add a 4 GeV electron Energy Recovery Linac to yield collisions with RHIC’s existing ion and polarized proton beams at one (modified) IR of RHIC. That design and cost estimate were subjected to an internal cost review at BNL in early October. The cost estimate is sufficiently high (several hundred million dollars, without inclusion yet of a detector, experimental hall or coherent electron cooling of the hadron beams to boost luminosity) that it is clear the project would require a strong endorsement from the next U.S. Nuclear Physics Long Range Plan to proceed to a DOE Critical Decision stage. Thus, the immediate focus – as recommended in the 2007 Long Range Plan – must be on carrying out a robust R&D program leading to a timely demonstration of feasibility of the needed advances in the technical state of the art. We anticipate a Funding Opportunity Announcement for a competitive program of EIC-related R&D funding to come during FY10 from the Nuclear Physics Office at DOE. One of the primary charges to the EICAC during the November meeting was to make recommendations concerning the most urgent aspects of that R&D program, and we anticipate such recommendations to be part of the Committee’s report.
The EICAC meeting
was immediately preceded by a half-day workshop at the Fall DNP meeting in
BNL Safety Incidents
Five serious safety incidents occurred at BNL during the last year, distributed among multiple sites and directorates. These have jeopardized continuing healthy operations of the laboratory, and have therefore demanded a serious and extensive response from the laboratory management. The incidents themselves are very briefly described in an article in the Dec. 4, 2009 issue of the BNL Bulletin. The article covers a recent All-Hands meeting at the laboratory, at which Sam Aronson and several ALD’s (including me) stressed the seriousness of the incidents, of the injuries to several workers, and of the threat to the laboratory’s reputation and ability to continue attracting healthy funding levels for ongoing and future research. A number of specific corrective actions will be carried out during the coming year in response to the individual incidents, but the suite of incidents has also highlighted common issues at BNL, including deficiencies to date in configuration management for buildings and facilities, in proactive identification of legacy hazards, and in various aspects of work planning, but including above all the need for more effective senior management focus on safe and efficient operations. The senior management has put together a Leadership Action Plan to accomplish that focus, with both short- and long-term changes in mind. The proactive approach taken by laboratory management has, for now, avoided a serious DOE-instigated safety standdown and audit at BNL. Our continuing attention to carrying out the changes envisioned in the Leadership Action Plan, and in accomplishing the range of corrective actions adopted to address specific incidents, will be closely monitored by both DOE and Brookhaven Science Associates. Not only lab staff, but also users, will have to redouble efforts to think through and plan your work carefully before you start, identifying hazards and strategies for dealing with them, in accordance with established BNL procedures and with coordination with your collaboration’s safety liaison officers. We will also be asking your help in maintaining good housekeeping around the experiment sites, and in identifying latent safety hazards at the RHIC complex that people may normally take for granted as part of the everyday work environment.
2010-1587 | INT/EXT | Newsroom