Sphenix-tpc-l mailing list

[Takao Sakaguchi <takao AT bnl.gov>]

    Hi Charles and all,
    
     Thanks for the list of activity summary.
    
     About the wandering pedestals, this is basically due to failed
    configuration
    of the SAMPA chip. We tried to fix the resistors on the I2C for as
    many FEEs
    as possible (around 220 out of 624) in Dec 2023, but about the 400
    were
    left as they are because the symptom was not seen for them at that
    time,
    and in addition, we didn't have enough time to fix all of them.
    
     If the configuration was properly done, the pedestal values are
    fixed to 60.
    This is realized by the following procedure in the SAMPA:
    
    1, Turning on so-called Baseline-correction-3 (BC3). The BC3
    function tries
    to follow the long-term perturbation of the baseline values and
    force them
    to zero. This results in the pedestal values of zero, meaning the
    any signal
    going below zero will be cut out and not seen.
    2, In order to keep the data below mean pedestal values, we added an
    offset
    of 60 after the BC3 was applied. This brings the default pedestal
    values to 60.
    
    If the SAMPA configuration was failed, both or either of 1 and 2 are
    not applied,
    and the result will be:
    
    - if 1 is failed, the pedestal value will be ~150. The out-of-box
    typical pedestal
    value is ~80, and if 1 is not applied, it won't be set to zero
    first, but only offset
    is added, meaning the pedestal will be ~150.
    - if 2 is failed, the pedestal values stick to zero and you won't
    see other half of
    the Gaussian distribution.
    
    The safest and sure solution to avoid this problem is to apply
    neither 1 nor 2.
    Then you will know the pedestal values are for sure around 80. The
    downside
    of this is that you have to set the zero-suppression threshold
    channel-by-channel
    if you want to set the thresholds in terms of n * RMS rigorously.
    
    But alternately, we could average the threshold values over one
    SAMPA which we
    are doing now anyway, assuming the pedestal mean and RMS values
    don't change
    so much over a SAMPA, which is usually the case.
    
    Shall we do this? It is very easy to do.
    
    By the way, I don't think I will replace any other FEEs now. The
    only thing I would
    like to do is to remove the GND braids from a FEE in the 6 o'clock
    R3 in south as
    we learned this won't solve the noise issue, and the way the GND
    braids were put
    is ugly.
    
    Takao

On 3/2/25 3:00 PM, Hughes, Charles [PHYSA] wrote:

Hello All

Today I'm using the sphenix-tpc list at the suggestion of @Huang, Jin. I'm not sure who all is on that list, so I included some of the Debrecen and BNL folks as well (apologies if you got 2 emails).

Let's meet MONDAY 03.03 at 9:30 AM ET (3:30 PM CET) to discuss ongoing operations/analysis/planning for the TPC. In particular:

 

HV: Last week we made a lot of progress which has culminated in the TPC running every night and continuously throughout the weekend. However there is still more progress to be made including HV channel mapping and further work on the GUI (implementing weather compensation). Additionally, @Thomas K Hemmick asked me to investigate the cable for NS 12 o'clock R3 and we should discuss plan about that.

Gas/Cooling: @Robert P. Pisanihas helped get our cooling to the point where it has been proven stable for many days. Rob has also requested s few hours when the HV/LV can be off for him to commission some new temperature sensors for the CDU in the hall which will give a much better picture of what's going on there. We should also ask him when the dry cabinet will be installed.

LV/FEEs: Last week we also made progress reducing the noise in the TPC, discovering the EMCAL rack communications module as a big contributor. @Haggerty, John and @Stephen Boose will need to get together to discuss workable solutions. Also @Sakaguchi, Takaohad expressed a desire to explore replacing some FEEs which are newly malfunctioning. Tom had some questions for the Takao and Jin about the TPC FEE settings (why is pedestal set to 60, how to fix the wandering pedestal issue). I would like to talk to Jin and Takao about re-calculation of the TPC ZS thresholds. Since the noise was reduced, last years thresholds are not optimal.

Diffuse Laser: Friday, @Huang, Jin asked if he could re-start services on the diffuse laser fan out board. We asked him to hold off until tomorrow. I think we should bring back the diffuse laser entirely, including some standalone runs to send to Ben Kimmelman for re-analysis. Let's discuss.

Line Laser: @Seth Howell, @Azmoun, Bob, @Finnelli, Kristina, and @Kuczewski, John made great progress on the TPC line laser. This culminated in the testing of the lasers in the NS bore on Friday. We should discuss this as well as @divaldo95 AT gmail.com's work on the noise mitigation. We should also discuss the path forward including Seth's alignment parameter search and getting to the point where we can think about threading the laser into the TPC.

Contingency Box: As @Mandracchia, Kevin said, we need to discuss with John when we can ramp up work with the contingency boxes. We should also make sure we take advantage of @shana Prifte's offer to help.

Analysis: Now that we have a good amount of cosmic data, we should discuss analysis of this for gain balancing. @josborn1 AT bnl.gov and @Luke Legnosky have started to look around in the data. What do we need to do to get to MIP peaks ? 

Any other pressing business (directives from the workfest, offline analysis, etc...). For example, firmware upgrade.

        Indico Link:https://indico.bnl.gov/event/27062/
      
        
      
      
        Zoom Link:https://urldefense.com/v3/__https:/bnl.zoomgov.com/j/1619343392?pwd=MDExeG91aHgyYlJrUldadjZSaGdhUT09__;!!P4SdNyxKAPE!HRoSUDHkh2yMr832EO6tBSgqxIDI10WSRcVdFxtfkmUyGQB_7rYDnEOAP_lv18LmBgev-KS8Ir-CovNhM1aUEu6Btq077w$
      
        
          
            
              
                
                  
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