Commissioning and running of sPHENIX

[Jamie Nagle <jamie.nagle AT colorado.edu>]

Hello sPHENIXians,

This week marks the start of cryo-week #10 and we are continuing to sample the full luminosity with photon and jet physics triggers.  There is also important progress in stabilizing running with the MVTX and INTT in the Big Partition, as well as efficiency improvements in the start-of-store procedure.   I encourage people to check the data we are taking at low levels, mid-levels and physics previews that are exciting to see.

The TPC now has the new gas mixture, including nitrogen.    The short summary is that it helps in terms of stability; however, the voltage considered safe is only 4.1 kV and discharges at 4.2 and 4.3 kV prevent running at the desired 4.5 kV.      The decision is to run with the TPC at 4.1 kV six hours per day in Big Partition, checking stability and evaluating efficiency, gains, etc. (noting that it is below optimum working point), and in parallel working on firmware updates and zero suppression for the TPC and TPOT.     The other 24 - 6 = 18 hours a day, we will continue taking physics data at a high rate.      The luminosities and uptime from the accelerator continue to be challenges.    With recent good uptime periods, it would take 40-50 weeks to achieve the sPHENIX 45 pb^-1 for |z|<10 cm minimum goal.    Thus, we cannot stay running this way.

At the RHIC Coordination meeting today, it was decided that C-AD will test some various scenarios.    First, they are testing today bringing sPHENIX and STAR into collision at different times, i.e., separating the ramp.    Then on Thursday's Maintenance Day, they will switch the needed buses for sPHENIX to run at zero crossing angle.      With sPHENIX and STAR both at zero crossing angle, there will be significant beam-beam interaction limits (note that the e-lens used in Run-15 is not available - Wolfram said that resurrecting that is "hopeless").   They will then try configurations without collisions in sPHENIX, without collisions in STAR, with a crossing angle in STAR, etc (see some details in Kiel Hoch's slides from C-AD linked below).     No decision is being made at this point;  these are tests to inform a next discussion to see how a subset of RHIC goals for this run can be met.

Thanks to Anne Sickles for completing a great job as Period Coordinator!  We welcome John Lajoie as the new Period Coordinator (pictured below)  - it is going to be epic (ha, ha, ha)!    A dinner event on Thursday, June 20, 2024 around 6 pm will be awesome (maybe not tacos this time).

Here are links to the slides from the RHIC Coordination meeting from sPHENIX and also from C-AD.  

https://indico.bnl.gov/event/20768/contributions/93110/attachments/55355/94717/sPHENIXRunCoordinator_RHICCoordinationMeeting2024_06182024.pdf

https://indico.bnl.gov/event/20768/contributions/93109/attachments/55358/94722/RHIC_Coordination_Meeting_XXI.pdf

We have another top notch shift crew incoming (picture  below)!

Sincerely,

Jamie

sPHENIX Run Coordinator 2024

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|| James L. Nagle   
|| Professor of Physics, University of Colorado Boulder

|| EMAIL:   jamie.nagle AT colorado.edu
|| SKYPE:  jamie-nagle        
|| WEB:      http://spot.colorado.edu/~naglej 
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