sPHENIX tracking discussion

["Frawley, Anthony" <afrawley AT fsu.edu>]

Hi All,

We had two presentations. The slides are posted on the indico page:

https://indico.bnl.gov/conferenceDisplay.py?confId=1601

The minutes are below.

Cheers
Tony

Luciano Musa - Upgrade of the ALICE silicon tracker using CMOS pixel sensors
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Luciano gave us a nice overview of the ALICE MAPS detector project, including the timeline and cost breakdown.

There was a discussion of how we might fit into the production schedule if we opted to go with this technology for all or part of the sPHENIX tracker. Luciano said that this is a complicated question. The capacity for silicon manufacture is typically huge compared with ALICE requirements, so it should not be a problem expanding the silicon production. But it is more complicated to predict bottlenecks for the later stages. It will be clearer once the production actually starts.

Luciano said he asked a CERN engineer about the suitability of the ALICE space frame design for use in sPHENIX.
He said (although no guarantees without detailed engineering) that it looks like it could be used unmodified for sPHENIX up to a 60 cm outer radius.

Tom Hemmick - TPC ion backflow and space charge calculations:
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Tom described the effort that is ongoing to simulate space charge effects in the TPC in sPHENIX.

The bottom line is that first results with a new code are expected in the coming days.

Slide 19: Discussion about the modified gating grid idea suggested by Dick Majka.
The mesh spacing is a variable that has to be optimized. The estimate of 80-90% efficiency depends on how many mesh layers are distributed along the graded voltage, and how much of the tail is collected.
Normally, the electric field lines would go through holes in mesh, the gate is operated by turning on the kicker so that the mesh collects ions, and how long it takes to collect the ions depends on how far to the nearest mesh.
In principle, we could install the mesh and not use it. But there may be complications.

Slide 20: Expect to get results in the next few days.
It is possible to use Tom's configurable new code to calculate results for the ALICE case, as a check on the code.

Come back in 2 weeks with results!
Carlos will be the speaker.

Next meeting:
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We will hopefully hear about results from the new TPC space charge code.

Mike McCumber will report on his work on generating four macros to allow us to simulate each of our possible combinations.

Mike also mentioned that he is having trouble with ganging together strips in the outer silicon strip tracker (we will need to connect three strips together in layer s1 and six strips together in layer s2. When he tried it the code ran for a long time and ran out of memory. This needs to be resolved, since the present design forces us to gang those strips together.

We will have a discussion about creating common criteria for pattern recognition across our tracking options. Following the discussion at the simulations meeting last Tuesday, Mike and Tony will start working on a proposal.

The next meeting will be on December 18 at 9:00 am ET.