MICE/MuCool Coupling Magnet at HIT Technical Progress

1. MICE/MuCool Coupling Magnet at HIT Technical Progress WANG, Li MICE Group, ICST/HIT Shanghai Institute of Applied Physics, CAS

2. Contents • Mandrels and Cover Plates for 3 coupling magnets • Conductor Slices from the QiHuan Company • Vacuum Chamber & Interface w/RF cavities • Heat loads and Available Cooling Capacity • Coupling Magnet Double-Band Support

3. Mandrels and Cover Plates for 3 coupling magnets • The 6061-T6 Al mandrel fabrication is changed from welded plates to a forging because the heat treatment process of welded mandrel is hard to realize using currently available ovens in China. • 3 forged mandrels and 2 forged cover plates were contracted out to QiHuan Corp. in Beijing at the end of October (Fabrication of one cover plate for the MuCool magnet has been done). The first MuCool mandrel is expected around the middle of February 2010, which means the MuCool coil winding can only start at the end of February 2010 if without having large coil test. The other two MICE mandrels are expected in April or May, 2010. • There is an additional cost of 100k YuanRMB for the MuCool mandrel. The welded mandrel with cost of 70k YuanRMB has to be abandoned. (This is a potential funding issue.)

4. Welded Mandrel Already Fabricated Heat treatment is required to make the mandrel strong enough

5. Strength of forged 6061-T6Al mandrel • 遵循中华人民共和国有色金属行业标准YS/T479-2005《一般工业用铝及铝合金锻件》；Conform to the Chinese standard YS/T479-2005 on forged Al and Al alloy. • 自由锻件（胎膜）的尺寸及偏差符合供需双方签订的图样或合同规定。截面积不大于165000mm^2的自由锻件，室温力学性能符合YS/T479-2005-表4的规定。The material strength at room temp. can reach the value as the below table in YS/T479-2005. Longitudinal Transverse Radial Thick

6. The training of coil winding technique for QiHuan by ICST was done by the end of this July. The QiHuan company submitted three 1-meter long conductor splices to be tested at LBNL. All the splices submitted had resistances that were less than 0.6 n at 1 T. The splice fabricated by ICST were also entirely satisfactory in that they ran from 0.7 to 1.3 n. The change between the ICST splices and the QiHuan splices is not fully understood. The QiHuan splices were tested in magnetic fields from 0 to 5 T. The 0 field splices had a much smaller resistance because the solder was superconducting at that field. The solder selected was the Sn-Pb eutectic Solder, which tested very well in the splice tests. Conductor Slices from the QiHuan Company

7. Vacuum Chamber & Interface w/RF cavities Discussion among HIT, QiHuan and LBNL recently: Too High For MICE • Is tolerance is acceptable for the MICE cooling channel? • Does the MuCool magnet need to work as back-up for the MICE cooling channel? • Higher accuracy means a higher cost for fabrication (doubled price). For now, the cost is till within the budget, but if high accuracy required for MuCool magnet, it is beyond the budget and the procured 304SS materials for MuCool magnet vacuum chamber (~80k Yuan RMB) has to be abandoned (funding issue) !

8. Heat Loads and Available Cooling Capacity at 4.2K Greatest uncertainty A single Cryomech PT415 cooler generates, 1.5W/4.2K, 50Hz with the first stage at 55 K. Is the contingency adequate?

9. Heat Loads and Available Cooling Capacity on the Cooler First Stage at 60K Greatest uncertainty Note: A Cryomech PT415, is good for 60W at 55 K for the cooler first stage.

10. Cover plate Top he vessel Banding Cooling tubing Coil Heat shield End plate Vacuum vessel Bobbin 10mm 18mm Tight space for MLI

11. CM vacuum vessel MLI RFCC coupler tube Cold mass Thermal shield The tight space will lead to difficulty in cryostat assembly and an increase in the heat leak locally in the five places where the couplers and vacuum pump port come out of the vacuum vessel. The problem is the potential for a larger radiation heat leak at 4.2 K into the cold mass. This has been an ongoing problem.

12. 300K-60K Band Rod End Thermal Intercept Clevis Pin Bracket Base Plate 60K-4.2K Band Coupling Magnet Double-Band Support

13. Cold Mass Support Assembly • Due to possible shipping loads of 2.5g during long distance transport, the design force of the cold mass support assembly was increased from 127 kN to 200 kN, the single-band support was updated to the double-band support considering tight space and restricted heat leakage requirement through the bands. • The small angle (<100 due to the magnet design) is another challenge in the cryostat assembly. Angle <10o

14. The mandrel will be changed from a welded plate mandrel to a forging because of heat treatment of the welded mandrel is a problem. The forging has adequate strength in all directions. The margins for coil placement in the cryostat need to be reviewed further. Small insulation spaces around the couplers and on the cryostat inner bore can cause a higher heat leak at 4.2 K. This is still a concern. The cold mass support design was changed because of the shipping loads. The small angle (<10o due to the magnet design) is another challenge in the cryostat assembly. The conservative design of the cold mass supports might allow the support angle to be changed. Concluding Technical Comments

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