Notes From the Associate Director
By Steve Vigdor
I will try to provide roughly monthly updates in the RHIC
News on items of RHIC/AGS policy of general interest to users.
In this first communication, I have good news and bad news. Let
me start with the bad news, since this may call for some
involvement by users.
1) RHIC run 8 is proceeding very smoothly so far. First d+Au collisions were achieved this past weekend, and we are on track to begin physics production by December 1. However, we still do not have an FY08 budget from Congress. The Continuing Resolution (CR) has been extended so far to Dec. 14, and little progress has been noted on an Energy and Water Appropriations bill. If the CR is extended past the beginning of March, we will have to terminate the run early, jeopardizing polarized proton collisions for the second year in a row. If Congress decides to extend the CR for all of FY08, then there can also be no construction start on new detector upgrade projects, namely, the PHENIX FVTX and NCC projects. This is likely, in turn, to push back the start of other planned detector upgrades. Completion of the EBIS source for RHIC might also be delayed. The absence of Energy and Water Appropriations furthermore delays starting on the Competitiveness Initiative that has nominal bipartisan support in Congress. While I will keep you posted on progress regarding a budget in subsequent newsletters, the UEC informs me they plan to organize some response from the user community to this situation.
2) The successful implementation of longitudinal stochastic cooling in the yellow beam of RHIC during the 2007 run opens up the possibility to achieve nearly RHIC II luminosities on a much shorter time scale, and at much lower cost, than envisioned in the 2007 Nuclear Physics Long Range Plan. We have presented to DOE a plan to install and test by FY11 longitudinal and transverse stochastic cooling of both beams. In particular, longitudinal stochastic cooling is installed for the blue beam in 2008, and a first plane of transverse stochastic cooling pickup and correction will be installed in one ring before the 2009 run. This will allow a test in Au+Au collisions in FY09, to see how the time-averaged luminosity will be enhanced and, in particular, if the coupling between radial and vertical beam tunes is sufficient to get significant cooling in both transverse directions with only a single plane of pickup and correction. A single plane of transverse cooling will be installed for the other beam for the FY10 run. In parallel with these implementations, the RF system will be upgraded to 56 MHz, with the effect of reducing the beam population of undesired RF buckets, and thereby improving the collision diamond.
Simulations of the effect of stochastic cooling suggest that the above additions should improve full-energy Au+Au time-averaged luminosity to ~50 x 1026 cm-2s-1, or about 70% of the design goal for RHIC II. If the coupling between the two transverse tunes turns out to be insufficient in the FY09 test, then two additional planes of transverse cooling may be needed in FY10 and beyond to achieve the above luminosity. In any case, the cost of the stochastic cooling upgrade is small enough to be accommodated in BNL’s projected budgets by stretching or delaying other planned Accelerator R&D and Improvement Projects. We place the stochastic cooling at very high priority, and will develop it even if the full-year CR contemplated above comes to pass for FY08. The luminosity upgrade will place RHIC in a favorable position for accomplishing RHIC II research goals during the next decade.
3) In order to take full advantage of early luminosity increases, we will soon have to re-evaluate progress toward DAQ and trigger upgrades for the detectors and capacity upgrades for RCF. This will be done in the context of updating the Midterm Strategic Plan developed at the laboratory over the past few years, with out-year budget guidance promised from DOE. User input into these considerations will be welcome. We will also be re-evaluating the scope of RHIC II, the path toward incorporating electron cooling, and plans to improve luminosities for p+p and for low-energy heavy ion collisions, where stochastic cooling will not be of much help, and for full-energy Au+Au up to full RHIC II goals. Possibilities here include pre-cooling with electrons, installation of electron lenses, and improving bunch intensities. I will update you on these planning exercises in upcoming newsletters. In the meantime, you should all be thinking about how to make optimal use for physics of improved luminosities over the next several years.
The Relativistic Heavy Ion Collider at Brookhaven National
Laboratory is a world-class scientific research facility primarily
funded by the U.S. Department of Energy Office of Science. Hundreds
of physicists from around the world use RHIC to study what the
universe may have looked like in the first few moments after its
creation. What physicists learn from these collisions may help us
understand more about why the physical world works the way it does,
from the smallest subatomic particles, to the largest stars.