Hall C Pedestal Runs and Determining FADC Thresholds

Overview

This How-To discusses the necessary steps required in order to take a pedestal run utilizing the single arm DAQ's. Furthermore, the steps required in-order to determine the appropriate FADC thresholds are discussed.

NOTE: This is for EXPERTS ONLY.  If this is done poorly and not caught the FADCs will not work correctly and the data maybe garbage!

Taking Pedestal Runs

• Ensure that both single arm DAQ's are configured with the "fadcnothr" flag, which is activated via. of the pre-scale GUI, and the configuration has been saved
  • The FADC's can either be in mode 9 or 10
• With both arms take at least 1000 cosmic or EDTM triggers and note the run numbers

Determining the FADC thresholds

• The following example will illustrate the necessary steps required to determine the FADC thresholds for SHMS ROC 2
• On the SHMS side, this procedure will have to be repeated for both ROC's 2 and 4
• On the HMS side, this procedure only has to be executed for ROC 1
• With the pedestal runs complete, open a terminal and SSH into cdaql1

ssh cdaq@cdaql1

• Setup the hallc-online analyzer

go_analysis

• Descend into the hallc-online hcana/podd directory

cd ../hcana/podd/hana_decode/apps

• Exectue the tstfadc_main.C script

./tstfadc

• Input the appropriate configurations: raw data file location, run number, number of events, spectrometer name, crate number

Enter the location of the raw CODA file (raw, raw.copiedtotape): raw
Enter a Run Number (-1 to exit): 1537 
Enter Number of Events to Analyze (-1 = All): -1
All Events in Run 1537 Will be Analayzed
Enter the Spectrometer Name (hms or shms): shms
Enter the Crate Number to be Analyzed: 2

• If successful, the for file "fadc_data.root" will have been produced
• In order to produce the threshold text file "thresholds.dat" one needs to execute the calc_thresh_hallc.C ROOT script

root -l ./calc_thresh_hallc.cxx

• Input the appropriate configurations: spectrometer name, crate number, FADC mode, threshold in channels

Enter the Spectrometer Name (hms or shms): shms
Enter the Crate Number to be Analyzed: 2
Enter The Mode of The F250's: 9
Enter The Number of Channels Above Baseline the Threshold Should Be [40 (10 mV) recommended]: 40

• A ROOT file "fadc_ped_data.root" will have been created which contains the final fits and determines the baseline values and thus the threshold values which are written to the text file "thresholds.dat"
• Open the "thresholds.dat" file and have a sanity check the thresholds
  • Most FADC channels should have thresholds set to 400-700 channels
  • For channels set to 4095, these channels are empty
  • For ROC2 slot 14 channels 12-15 are set to 1 by default since they are fast raster FADC channels
  • For ROC4 slot 18 channels 12-15 are set to 1 by default since they are fast raster FADC channels
• In the event that a few thresholds are set to unrealistic values, simply open the "fadc_ped_data.root" file and perform the fit manually if possible
  • If a manual fit is not possible, then a new pedestal run with more statistics is recommended

Loading the FADC Thresholds

• These instructions only pertain to the HMS at the moment. For NPS, it is different.
• In order to have the CRL's load the appropriate FADC threshold files the newly created "thresholds.dat" file must be placed in the correct location
• SSH into cdaql1 as coda

ssh coda@cdaql1

• Descend into the respective thresholds directory for the appropriate ROC

cd coda/config_files/SHMS/ROC02/thresholds

• Copy the newly created "thresholds.dat" into the current working directory and tag the "thresholds.dat" file with the current date

cp hana_decode/thresholds.dat thresholds_DDMONYYYY.dat

• Ascend one directory and symbolically link the newly created thresholds file as "thresholds.dat"

cd ../
ln -fs thresholds/thresholds_DDMONYYYY.dat thresholds.dat