1. Angular Response of 10inch PMT for IceCube Hiroko Miyamoto Dept. of Physics Chiba University

2. What you learn from 2D measurement. Tube angular response (uniformity). Actual collection area of PMT (“10 inch” tube would not imply collection area of 10 inch diameter.) The sensitivity table (X,Y) or (R,q) gives a redundancy in understanding the DOM (Digital Optical Module) angular response.

3. R-guide(300R) UV LED Dynode UV LED Rotation bed 2D Measurement system

6. The Measurement (of the first 14PMTs) The Light Source – UV (380 nm) Nichiya LED (220  driving) Collimated to less than 1mm diameter on the surface of PMT. Flashing at the every 1.3mm point on the R-guide. The Pulse is formed by the Agilent Func. Generator (100 nsec) 30photoelectrons/shots, corresponding the average of 3000 shots. [204 points/slice] PMT – Hamamatsu R7081 “ –02 tube. HV – 2000 V, 5E7 ～ 5E8 Gain Dark current ~ 404  A @ 2000V (~363  A @ 1800V) Noise Rate ~100 Hz ~2.5kHz with 50 mV threshold @ room temperature.

7. 10 8 Gain 75nsec

8. Table 1: collection area and sigma of uniformities (The results of 14 PMTs)

9. N Org - +

10. Example 1: ΔC.E. of SF0023 HV@2000V vs SF0023 HV@1800V

11. Example 2: ΔC.E. of SF0050 HV@2000V vs SF0050 HV@1800V

12. N Org - +

13. Example 3: ΔC.E. of blue SF0050 vs SF0050 rotated (blue) and SF0050 vs SF0050 rotated [without magnetic shield] (red)

14. N Org - +

15. N - +

16. Example 4: ΔC.E. of blue SF0050 @ HV2000V vs SF0050 @ HV1800V (blue) and SF0050 vs SF0016 (yellow)

17. N Org - +

18. N - +

19. N - +

20. Example 5: ΔC.E. of SF0050 vs SF0016 (yellow) and SF0016 vs “ Flat(idealized surface) ” (red)

21. Example 6: ΔC.E. of blue SF0023 vs SF0023 rotated (blue) and SF0023 vs SF0023 rotated [without magnetic shield] (red)

22. N Org - +

23. N - +

24. N - +

25. N - +

31. What we have seen (from Results of 14 PMTs) The uniformity shows variance by 30 ～ 50% in the measurement region. For most of tubes, the effect of geomagnetic field is canceled out at 5% level. The 2d sensitivity behavior does not exhibit spherical symmetry. Actual collection area is 85% ～ 95% (501[cm^2] ～ 560[cm^2] of 590[cm^2]) The effect of geomagnetic field could be seen. Tube by tube variance is significant.

32. Future Work Measurement for evaluation of dependence on the incident angle of the light from LED. Uniformity measurement of Digital Optical Module. Our Java based class for measurement have been already available. Please send us DOM!

33. DOM … a Key element in IceCube

34. The End

35. Improvements of measurement systems.