sphenix-maps-l AT lists.bnl.gov

Subject: sPHENIX MAPS tracker discussion

List archive

From: "Liu, Ming Xiong" <mliu AT lanl.gov>
To: "SPHENIX MVTX " <sphenix-maps-l AT lists.bnl.gov>, "Sondheim, Walter E" <sondheim AT lanl.gov>
Cc: Stefan Bathe <stefan.bathe AT baruch.cuny.edu>, Kin Yip <kinyip AT bnl.gov>, Jamie Nagle <jamie.nagle AT colorado.edu>
Subject: [[Sphenix-maps-l] ] MVTX meeting next Monday 8/5 12:30PM/ET
Date: Sat, 3 Aug 2024 02:59:08 +0000

Dear all,

We will have MVTX meeting next Monday at usual time 12:30/ET.

Besides the usual topics, I would like to discuss whether we could keep MVTX running during the STAR steering.

Based on Hao-Ren’s presentation (last Monday 7/29 MVTX meeting, https://indico.bnl.gov/event/24327/contributions/94573/attachments/56208/96191/MVTXComm_20240729.pdf), the beam background level is similar to previous -2mrad beam Xing-angle runs, and also similar to the polarization measurements.

From last Monday’s discussion, our main concerns are,

possible beam loss during the STAR steering that could damage the MVTX sensors,
we don’t have spare detector for immediate replacement, and if damage happened, probably there is not enough time to fix it before Run25 - taking out MVTX, replacing damaged staves and putting it back will take several weeks at least.
w/o TPC running, we can only do limited physics now, and it is not worth the risk to operate MVTX during STAR steering

I had phone discussion with Stefan Bathe (PC) tonight, Cameron was also there as evening SL. Based on their recent observations:

it takes ~14min to stop DAQ, turning off MVTX, then restart the run again with the rest of subsystems. MVTX will be brough back to BP after the run ends ~30min later.
There was NO single failure that causes beam loss during STAR steering
There have been several accidental beam losses recently during normal data taking, at frequency of once in every 1.5~2 days. MVTX was ON during these runs and seemed not affected much.

So under current MVTX operation mode, we effectively lose ~45min of beam time for MVTX physics at the beginning of a fill.

Since a store is typically 8hrs long, it is ~9.4% or more loss of useful beams.

It is a judgment call, risk vs benefit. Please think about these factors over the weekend and we can discuss them on Monday.

Cheers,

Ming

Dr. Ming Xiong Liu

P-3 Group, MS H846

Nuclear and Particle Physics & Applications

Physics Division

Office: 505.667.7125

Mobile: 505.412.7396

Los Alamos National Laboratory

[[Sphenix-maps-l] ] MVTX meeting next Monday 8/5 12:30PM/ET, Liu, Ming Xiong, 08/02/2024