M. Bonesini INFN Milano

1. PMTs tests in B field M. Bonesini INFN Milano M. Bonesini - MICE RAL 13-06-07

2. Conventional PMTs shielding • TOF0 PMTs requires no shielding, aside 1 mm m-metal due to small B field (B << 50 Gauss, Kevin private communication) • TOF1/2 even after the 100 mm global iron shielding needs some additional shielding to use conventional PMTs (as B// ~ 200-300 G, B _|_ ~ 1000 G) M. Bonesini - MICE RAL 13-06-07

3. Advocated solutions: • Solution A (“Ghislain cage”): extra shield (50 mm) connected with joints to first shield (100 mm) and local shielding of PMTs (m-metal only if 420 mm hole) • Solution B: no-extra shield but heavy local shielding of PMTs a la D0 (test magnet delivered now at Bicocca) M. Bonesini - MICE RAL 13-06-07

4. Problem: R4998 can bare Bperp but not B// B//< 50 Gauss fine; B_|_ < 100-120 Gauss fineeventually additional m-metal or soft iron M. Bonesini - MICE RAL 13-06-07

5. B field with one 100 mm iron shield (current design) M. Bonesini - MICE RAL 13-06-07

6. My old transparency at RAL CM16 • B field is ~ 200-300 G //; ~ 1000 G _|_ at r=30-35 cm (PMTs position) • I doubt it can be shielded with individual PMTs shields, preserving good timing properties • this point to 2nd shield, but we will try to test PMTs “exotic shieldings” bybuilding a 400 G lab solenoid BUILT: coil with 5 windings for fields up to 700-800 G M. Bonesini - MICE RAL 13-06-07

7. D0 tests (note # 2706) • Problems: • It will work for R4998 1” PMTs? • Tests to be done for Gain + timing See some results later M. Bonesini - MICE RAL 13-06-07

8. R. Bertoni, M. Bonesini INFN MIB M. Bonesini - MICE RAL 13-06-07

9. Laser source (Nichia Blue laser diode + up to 1MHz Avtec fast pulser: signals 100 ps- 2 ns) • field up to 470 G (now: 40A power), to go up to 700-800 G with new power supply (on loan) • signal comparable to BTF (~ 500-700 mV) • Use of different shieldings: mu-metal only, additional Fe shielding, … M. Bonesini - MICE RAL 13-06-07

10. G. Gregoire Shield From presentation by G. Gregoire at PC-224 and J.Cobb at PID // session  Close outer gap between to discs; thicker 2nd disc (50mm) Somewhat more complex – engineering / mounting TOFs…. M. Bonesini - MICE RAL 13-06-07

11. M. Bonesini - MICE RAL 13-06-07

12. Problems: • cabling (HV, signal, calibration fibers …) • in/out alignments (1cm = 50 ps): risk to loose calibration every time you move in/out M. Bonesini - MICE RAL 13-06-07

13. M. Bonesini - MICE RAL 13-06-07

14. B_r -- 500 gauss B_z 500 gauss G. Gregoire scheme gives very effective shielding for TOF1/2 M. Bonesini - MICE RAL 13-06-07

15. R4998 PMTs with only mu-metal shielding B//< 50 Gauss fine; B_|_ < 100-120 Gauss fine eventually additional m-metal or soft iron M. Bonesini - MICE RAL 13-06-07

16. R4998 PMTs: Fe box shielding M. Bonesini - MICE RAL 13-06-07

17. PMT tests results: B// M. Bonesini - MICE RAL 13-06-07

18. 0 cm M. Bonesini - MICE RAL 13-06-07

19. Solution A vs B • Solution A makes life easier for TOF1, but requires an extra shield + some problems for detector access + to change PMTs. Clearly it is very attractive for TOF1 with the 420 mm diameter (only m-metal for PMTs) • Solution B: under test at MIB, easier access to detector but more bulky support. Maybe fine for TOF2 M. Bonesini - MICE RAL 13-06-07

20. Preliminary KL PMTs tests • 2 shielded PMTs in MIB from Ludovico for tests • shielding mu-metal + Fe box • prelim. tests up to 470 G, we will go to 700-800 G with a more performant power supply on loan M. Bonesini - MICE RAL 13-06-07

21. Preliminary KL PMTs tests M. Bonesini - MICE RAL 13-06-07

22. Conclusions • PMTs shielding with massive Fe blocks is a delicate issue (promising for KL and TOF2, but we must go to 700-800 G for test magnet at MIB) • not fully understood effects with active divider of H6533mod: shielding more effective with increased Ia (?) • TOF1 cage fine, but welldue to slipping over of schedule (> 3 months) we may take probably some more time for a for a final decision M. Bonesini - MICE RAL 13-06-07