sPHENIX is a new detector at RHIC.

[David Morrison <morrison AT bnl.gov>]

Dear sPHENIX EC, collaborators,

As you know, earlier this week there was an incident at RHIC in which a LHe valve box that is part of the blue ring cryogenic system broke and then uncontrollably vented a significant amount of liquid helium. As a result, the blue ring is no longer cold and C-AD has been off-loading helium to its tank farm.  Experts are preparing to inspect the damage and then to develop a plan and timescale for repair.  C-AD Chair Wolfram Fischer has said that it may take a week before they can assess the situation fully.

Gunther and I met about an hour ago with ALD Haiyan Gao and Physics Dept. Assoc. Chair Jamie Dunlop to discuss the situation and possible options for going forward.  We emphasized that the sPHENIX collaboration is well prepared to make use of additional Au+Au beam time in Run-23 if the repairs can be made expeditiously.

Haiyan presented two scenarios: one in which an attempt is made to continue Run-23 (i.e., the RHIC cryo-plant continues to operate) and C-AD works to repair the damage in M weeks and provide N additional weeks of Au+Au beam, if repairs can be completed in time.  Both M and N are highly uncertain.  In the alternative scenario Run-23 is ended essentially immediately, and the operating funds are "banked" and used to add weeks of beam time prior to the currently scheduled start of Run-24.

We pointed out that this second scenario is also highly uncertain -- at a minimum it requires DOE ONP to allow the carrying over of operating funds.  We noted several other questions that we would need C-AD guidance on in order to allow the collaboration to make an informed, rational decision.  For instance, in Haiyan's second scenario, one could imagine wanting to start with Au+Au and then switch to p+p.  We would want to hear from C-AD about the costs, in terms of cryo-weeks, of choosing to do that. 

The ALD is pressing for a rapid decision, on the premise that this maximizes the possible carryover.  She said she wants to make a decision by COB this Friday.

We are scheduling a discussion on Friday at 1pm in the General Meeting time slot, following the end of the RHIC AUM,  to inform our response to the ALD.  We will provide as much reliable, updated information as we can prior to the discussion. We ask all EC members to attend if at all possible, and invite all collaborators to participate in the discussion. 

Regards,
Dave and Gunther

-- 
David Morrison  Brookhaven National Laboratory  phone: 631-344-5840
                Physics Department, Bldg 510 C    fax: 631-344-3253
                          Upton, NY 11973-5000  email: dave AT bnl.gov