Commissioning and running of sPHENIX

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

Hello sPHENIXians,

This week marks the start of cryo-week #27 [out of 19 (funded in FY24) + 6 (carry-over from last year) + 2 (extension coming out of FY25 = 27)].    The end of beam for Run 2025 is almost here -- just 131.6 hours left of gold beams.     The three weeks of Au+Au commissioning (for sPHENIX and C-AD) will end officially at 8 am on Monday, October 21, 2024.       There will then be 24 hours without the beam where the sPHENIX magnet can remain on.    After that there are two weeks of 2-person watch shifts for cosmic data taking with isobutane in the TPC and all detectors available.   Note that I will be flying home to Boulder,  Colorado on Tuesday, October 22, 2024.  🛫   

After a week of machine challenges, C-AD has now been delivering steady  Au-Au  stores with different numbers of bunches, crossing angles, and beam conditions for commissioning sPHENIX to be ready  for Run 2025.    Vertical and longitudinal cooling is now enabled in both blue and yellow beams (with 4 out of 6 planes).    The planned 56 MHz commissioning was pushed back by a week and machine development will just start tomorrow.

The MVTX background hits have re-emerged with the Au-beam, meaning they are specific to heavy-ion running and were simply not present in pp.     Cameron Dean and Kiel Hock (the C-AD Run Coordinator) have led the effort to characterize the backgrounds and test various configurations in an attempt to resolve the problem.     Currently with 111x111 physics-type stores, almost 60% of the MVTX staves in the horizontal plane are unusable due to constant auto-recoveries from too many hits from these splash events.   The last four days have been spent with dedicated sessions of single bunch studies where the auto-recoveries are not saturated to  diagnose the  problems.    A team of MVTX experts and friends have developed a suite of diagnostic tools with rapid feedback.    Additionally, a better understanding of the detector and electronics is worthy of further pursuit, i.e., the problem  is likely mitigated on both ends.     People are working as hard as possible to either mitigate the problem or have enough information for mitigation next year.

All other subsystems are running smoothly with Big Partition running at up to 5.5 kHz with minimum bias triggers.     This rate is limited currently  by the I/O of the buffer box system, and doubling the number of buffer boxes is planned for 2025.   The MBD and  ZDC triggers including z-vertex cuts look good and a Vernier Scan is planned for tomorrow.    TPC operations have been remarkably stable, and an interesting run condition observation has led to running at 1 mrad for the past few evenings.    The total charge load on the TPC has a large background contribution that is smaller when going from 2 -> 1 -> 0 mrad crossing, which  has important implications for how sPHENIX runs next year.  The TPC running has been successful to the level that today two sectors were connected to the new CAEN HV system, and gaining experience with this system will be quite valuable ahead of next year (where everything will be on this new system with many benefits).      The calorimeters, sEPD,  and other detectors have shown plots indicating good performance, and more such checks over the next few days are most welcome.      Despite not having physics specific goals for this AuAu run, a useful data sample is being collected that includes all subsystems (the MVTX too but with coverage limited to ~ 40%).

Many  of the exciting physics data checks, challenges on the MVTX background front, and more can be seen in the 

presentations from today's RHIC Coordination meeting by sPHENIX and C-AD linked below.   

https://indico.bnl.gov/event/20768/contributions/97801/attachments/57941/99504/sPHENIXRunCoordinator_RHICCoordinationMeeting2024_10152024.pdf

https://indico.bnl.gov/event/20768/contributions/97800/attachments/57931/99490/RHIC_Coordination_Meeting_XXXVII.pdf

Lastly, thanks to our next golden sPHENIX shift crew (picture below) and continuing Period Coordinator Akitomo Enokizono!

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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