1 COBRA Magnet Status W.Ootani MEG Experiment Review Meeting, Jul W.Ootani MEG Experiment Review Meeting, Jul. 2004

2 COBRA Excitation at π E5 Apr.13 COBRA installation Apr Cryostat evacuation Apr Cooling Apr Excitation Excitation test (Superconducting Magnet(SC) and Compensation Coils(NC)) Fringing field measurements and test of active shielding in π M3 PMT test for Timing counter inside COBRA PMT test for LXe calorimeter near COBRA Apr.29 Beam is back Apr.13 COBRA installation Apr Cryostat evacuation Apr Cooling Apr Excitation Excitation test (Superconducting Magnet(SC) and Compensation Coils(NC)) Fringing field measurements and test of active shielding in π M3 PMT test for Timing counter inside COBRA PMT test for LXe calorimeter near COBRA Apr.29 Beam is back

3 COBRA Installation in π E5 COBRA placed at almost right place on beam line without platform.

4 Excitation at π E5 Only 4days for cooling thanks to LN2 pre-cooling. Both SC and NC successfully tested at full operating current. (The first time to fully test NC.) COBRA provided perfectly stabilized field ( Δ B/B<0.05%) for PMT tests. Only 4days for cooling thanks to LN2 pre-cooling. Both SC and NC successfully tested at full operating current. (The first time to fully test NC.) COBRA provided perfectly stabilized field ( Δ B/B<0.05%) for PMT tests.

Fringing field measured at π E5 [Gauss] Fringing Field Measurements

Fringing field measured outside area π E5 [Gauss] Fringing Field Measurements

7 π E3 μ Lan < 1G μ Cap < 1G π M33 LTF < 20mG π M32 GPS < 20mG ECRIT < ?G π M3 beam line Kicker < ?G Septum < ?G RequirementMeasured 2-4G 1-2G 1.8G 0.3G 3.3G 4.8G μ E1 < 20mG 0.5G π E5 Neighboring area

8 Fringing Field Measurements Fringing field was measured as predicted (unfortunately). The problems are being fixed for most places. Fringing field was successfully compensated in μ SR facilities at π M3 using compensating coils. Control system has to be implemented. Fringing field at π E3 seems possible to be reduced < 1G by passive shielding. Detector at ECRIT did not work when COBRA was ON. Effect on kicker and septum in π M3 beam line has to be checked. Fringing field was measured as predicted (unfortunately). The problems are being fixed for most places. Fringing field was successfully compensated in μ SR facilities at π M3 using compensating coils. Control system has to be implemented. Fringing field at π E3 seems possible to be reduced < 1G by passive shielding. Detector at ECRIT did not work when COBRA was ON. Effect on kicker and septum in π M3 beam line has to be checked.

9 Possible Solution in π E3 Installation of active shielding in the detector ( μ LAN, μ CAP) is difficult because of limited space and cost(?). Passive shielding Shielding box built with 5mm-thick soft iron plates (5m-D, 4m-W, 3m-H) No front wall for minimizing influence on beam optics Roof might not be necessary. (For good accessibility) Installation of active shielding in the detector ( μ LAN, μ CAP) is difficult because of limited space and cost(?). Passive shielding Shielding box built with 5mm-thick soft iron plates (5m-D, 4m-W, 3m-H) No front wall for minimizing influence on beam optics Roof might not be necessary. (For good accessibility) With roof Without roof Beam

10 Summary COBRA magnet was installed in π E5 and totally tested. PMT tests were carried out by using COBRA field. Δ B/B<0.05% Stray field around LXe detector region is successfully canceled. Fringing field was measured in the neighboring beam line and problems are being fixed. It was found that active shielding is able to compensate COBRA field very well. Calibration of field mapping machine will be made this year. System alignment Calibration of Hall sensors Investigate possibility to use NMR Field map reconstruction Final field measurement is supposed to be carried out during shutdown period in 2006 after beam line commissioning is finished. COBRA magnet was installed in π E5 and totally tested. PMT tests were carried out by using COBRA field. Δ B/B<0.05% Stray field around LXe detector region is successfully canceled. Fringing field was measured in the neighboring beam line and problems are being fixed. It was found that active shielding is able to compensate COBRA field very well. Calibration of field mapping machine will be made this year. System alignment Calibration of Hall sensors Investigate possibility to use NMR Field map reconstruction Final field measurement is supposed to be carried out during shutdown period in 2006 after beam line commissioning is finished.

11 Schedule Feb Jul. 2004