Sphenix-tpc-l mailing list

["Huang, Jin" <jhuang AT bnl.gov>]

Dear tracking team 

As you know TPC switched to a new firmware for Run25 which provides phase locked clock to the RHIC bunch crossing clock on [Mar 30 2PM]. We are writing to provide details so they can be applied to Run25 calibration: 

From John Haggerty that the RF group measured 3x RHIC collision clock to be 28128771 Hz. And the new FEE firmware (v46) lock the ADC clock to be 30/16 x  RHIC collision clock = 17580482 Hz . So here is our recommendation on the Run25 clock setting in the calibration, carrying more digits of significant than we need for tracking: 

• TPC ADC Time Bin in Run25 = 17580482 Hz or 56.881262 ns <- note this is slower than our previous assumption of 2x RHIC clock
• RHIC beam collision clock = 9376257 Hz or 106.65237 ns  <- the change from pp and AuAu is negligible for our purpose 

Note the default drift speed and T0 in unit of ADC clock need to be calibrated again after the clock frequency calibration update. 

Cheers

Jin & Hugo

 

______________________________

 

Jin HUANG

 

Physicist, Ph.D.

Brookhaven National Laboratory

Physics Department, Bldg 510 C

Upton, NY 11973-5000

 

Office: 631-344-5898

Cell:   757-604-9946

______________________________

 

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From: Huang, Jin
Sent: Friday, January 31, 2025 4:12 PM
To: Osborn, Joseph <josborn1 AT bnl.gov>
Cc: sphenix-tracking-l AT lists.bnl.gov <sphenix-tracking-l AT lists.bnl.gov>
Subject: Clock frequency used in TPC reconstruction

 

Hi Joe and all

Closing the loop on the clock frequency used in Run24/25 reconstruction: 

From John Haggerty that the RF group measured 3x RHIC clock to be 28128770.729 Hz. And Hugo and I measured the 2x FEE ADC clock to RHIC clock ratio to be 4.262916255. 

We don't need that much precision for tracking reconstruction, but 0.1% precision is needed to keep track of the clocks cross 500x beam crossing over one trigger window. So here is my recommendation on the clock setting in the code, carrying more digits of significant than we need: 

• TPC ADC Time Bin in Run24 = 19985099 Hz or 50.037280 ns 
• TPC ADC Time Bin in Run25 = 18752514 Hz or 53.326184 ns
• RHIC beam collision clock = 9376257 Hz or 106.65237 ns  <- the change from pp and AuAu is negligible for our purpose 

Note the drift speed and T0 likely need adjustment by the same ratio once the clock frequency is changed in our calibration database. 

Cheers

Jin

 

______________________________

 

Jin HUANG

 

Physicist, Ph.D.

Brookhaven National Laboratory

Physics Department, Bldg 510 C

Upton, NY 11973-5000

 

Office: 631-344-5898

Cell:   757-604-9946

______________________________