How to calibrate shower and preshower with cosmics

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Procedure to calibrate shower and preshower with cosmics

1. Set the T6 threshold to -20mV using command " theshold_BB -s BB_Sh -20mV" on any adaq@adaql* machine.

2. Take a run with ps6=1 for about 500k events.

3. Replay the Bigbite run

4. Go to "adaq@adaql6:~/e06014/shower_calib/" location where you can find two scripts - one for shower and one for preshwer

5. Run the scripts "ser_sh_hist.C" for shower and "ser_ps_hist.C" for preshower.

4. The output of the ADC histograms is stored in ./ps/ and the HV adjustment factors are stored in ./adj_BB/adj_sh_XXXX.dat and ./adj_BB/adj_ps_L_XXXX.dat and ./adj_BB/adj_ps_R_XXXX.dat

5. Look at the histograms first and make sure all the fits are good. If there are any bad fits then find out the rough mean value of the ADC peak and use following procedure to make changes in the adjustment file.

 -- For shower, calculate the adjustment factor ( 120/peak_value) and set it in the file for that particlular channel.
 -- Do the same thing for preshower if the fit is bad. Preshower adjustment factor = 240/peak_value.  The index 0 on the ADC plot means preshower right     and index 1 means preshower left.

6. Once both the adjusment files are ready(check to see if there are no negative adj_factors in the file - result of bad fit) then copy them to following location adev@adaql3:~/slowc/HV_HALL_BB/adj_BB/

7. Go to the above location in adev@adaql3 account and and run following commands to adjust the HV

  -- For shower: " BB_SH  adj_sh_XXXX.dat" 
  -- For preshower: " BB_PS_L adj_ps_L_XXXX.dat"  and " BB_PS_R adj_ps_R_XXXX.dat" 

8. The HV is automatically updated once this is done. Save the HV file from the HV GUI.

9. Repeat the procedure by taking another cosmic run and check to see if the ADC peaks are aligned. If not, then perform the same procedure again. Usually it very close after 1-2 iteration.

10. Contact Kalyan or Yawei if there are any questions.