1. DOM Two Dimensional Scanning using testDAQ Hiroko Miyamoto T. Noda Faculty of Science Department of Physics Chiba University

2. Reminder: We did 2D scan for bare PMTs CE uniformity : Some tube to tube differences Gain uniformity: Almost universal behavior Implemented by ROMEO

3. New: 2D scan for DOMs CE uniformity / Gain uniformity: Present: Rely on Geant4 MC + the bare PMT calibration data to predict DOM acceptance. The complex structure of DOM has not been implemented in the MC. Easier and more reliable to MEASURE it directly!

4. 2D Scanning System for DOM Harness wire

5. DOM 2D Scanning System

6. Setup Light Source: NICHA 375nm UV-LED 100-200 PEs / shot, fired 1.6kHz by pulser 2D scanning system Spot size: ~1cm with the collimator Scan 4  in ~5cm intervals from point to point Do “testDAQ” ( ‘ready’ and ’go’) at each point. DOM Virgo, Rev4 Unsealed DOM, room temperature, ~1atm TestDAQ : taking data with ~4PE threshold, 1e+07Gain

7. Analysis Method (preliminary) (using the java program written by Chris W.) Calculate the photoelectron number with domcal Calibration (J.Braun?). Use the average of ~3,000 samples for each point of the DOM surface.

8. Results (preliminary…) Harness top center Harness top center

9. Results (preliminary…) Harness top center

10. Results (preliminary…) top center ～２５ｃｍ Harness Forward region Backward region Backward region

11. Results (preliminary…) Harness top center

12. Results (preliminary…) top center Harness

13. Results (preliminary…) top center Harness ～２５ｃｍ

14. Results (preliminary…)

15. Summary (Preliminary…) Took a first data of DOM photon CE map (along 1 axis). “effective” diameter of photon detection area is approximately 25 cm, which is consistent with the PMT cathode area we had measured previously. Photons hitting from backside of DOM do not produce measurable signals. To map out this region, we must improve our triggering : currently internal trigger with 4 PE threshold.

16. Issues to be resolved It would be better to trigger DOM EXTERNALY for taking non-biased data – Internal trigger with 4PE threshold may cause bias in scanning backside of DOM sphere. Domcal charge estimation may contain some errors in the estimation of the total charge (photoelectron #) of each channels. Need to figure out a way to turn off and on data taking without recycling HV power.

17. Outlook 4  measurement and map the CE on the whole DOM surface to be implemented by the detector MC simulation. Produce the standard-EYE DOM scanned by this method.

18. Near future plan Absolute calibration of DOM by scattered light from N2 laser : We did for bare PMTs It would be nicer if external trigger available