1. Cross-Calibration of FDs Sean R. Stratton TA-All Meeting – June 2010

2. Motivation We’re still trying to understand the relative energy scale differences between our FDs. The UVLED was used to cross-calibrate all three FD sites. Although RXF tests have been done in the past, we needed a longer, more thorough test to be done.

3. BRM/LR Calibration Method Get absolute calibration for selected tubes. ◦ CRAYS. Gain-match remaining PMTs by adjusting individual HV. Correct tube gains in each camera according to: ◦ Camera temperature. ◦ HV supply. ◦ Relative gain from XF data. Gains relevant for 1 hour periods.

4. BRM/LR Calibration Method Get absolute calibration for selected tubes. ◦ CRAYS. Gain-match remaining PMTs by adjusting individual HV. Correct tube gains in each camera according to: ◦ Camera temperature. ◦ HV supply. ◦ Relative gain of center PMT (0x77). Gains relevant for 1 hour periods. Hardware Level

5. BRM/LR Calibration Method Get absolute calibration for selected tubes. ◦ CRAYS. Gain-match remaining PMTs by adjusting individual HV. Correct tube gains in each camera according to: ◦ Camera temperature. ◦ HV supply. ◦ Relative gain of center PMT (0x77). Gains relevant for 1 hour periods. Software Level

6. The Calibration Constants G0G0 Absolute Calibration Constant – Only applies to specific subset of tubes (channels 0x33 & 0x77 of every camera and 0xB3 in cameras 0&6). Measured with CRAYS, has units of FADC/photon. G1G1 XF Non-Uniformity Correction – The HV levels in each camera are adjusted to get a flat response across all channels using the XF. This factor accounts for the non- uniformity of the Xenon source. G2G2 Xenon Flasher Correction – Tube gains are corrected using run-time Xenon flasher data. Mirror splash-back effects are accounted for by using data taken during HV adjustment. G3G3 YAP Correction – YAP source is used to monitor PMT aging effect. This value is currently unity (?). G4G4 Temperature Correction – Each camera’s temperature is monitored, and gains are corrected using a typical dependence of -0.72%/°C.

7. Case Study: BRM 20090225 Clear CLF run night Lots of data (~10 hr.)

8. BRM G 0 as of Feb. 08

9. BRM G total for 20090225

10. G 0 = 0.5087 T 0 = 24.55

12. Camera 08

14. Camera 07 When/Why was HV Changed?

15. Camera 10

16. Camera 05 Camera 07 Camera 10

18. 4 5

20. 6 7

21. 8 6 7

22. 10 11

26. 25 Feb 200922 Sep 2008

27. Camera 08092205 09022505 Temp. Correction Corrected % Change 037.541.9 1.05810439.65.60% 147.548.2 1.05356845.7-3.69% 249.351.1 1.05961648.2-2.18% 343.445.1 1.05738442.7-1.72% 450.153.2 1.06091250.10.09% 586.290.7 1.05702485.8-0.46% 647.059.7 1.06256856.219.54% 771.291.1 1.05860886.120.87% 854.357.3 1.0644453.8-0.86% 935.337.8 1.05788835.71.22% 1083.089.5 1.0644484.11.30% 1148.653.8 1.06184850.74.25%

28. Camera 05

29. Question 1 Are the built-in XF used as an absolute light source or is it used to check uniformity and relative gains? In other words, do we know or care exactly how many photons are produced by each XF per flash?

30. Question 2 It is our understanding that the HV supplied to each tube is adjusted to match the output signal of the absolutely calibrated tubes (0x77, 0x33, & sometimes 0xB3), using covered mirrors and the built-in Xenon flasher apparatus. How is this done? In software? Low-level analysis?

31. Question 3 If each tube’s HV is adjusted to gain-match the absolutely calibrated PMT’s, then why would we need to adjust the HV of an absolutely calibrated PMT (from CRAYS)?