mice/mucool coupling magnetsfor final machining. • the fabrication contract for the two mice...

Progress on MICE/MuCool Coupling Magnets

-1-2010-03-24 to 27, CM26, Riverside/USA WANG, LI

Progress Progress on on

MICE/MICE/MuCoolMuCool Coupling MagnetsCoupling Magnets

WANG, LiWANG, Li

Shanghai Institute of Applied Physics, CASShanghai Institute of Applied Physics, CAS



Contents

• Recent progress

Fabrication drawings, contract, forged mandrels & cover plates, etc.

• Design updating

Coil size, vacuum chamber, thermal shields, 3rd cryocooler etc.

• Schedule

• Comments



Recent Progress

• Prof. ShiXian Zheng still acts as the HIT representative in the MICE collaboration, Prof. Bin Guo (President assistant) as the HIT official supervisor for the coupling magnet project, Dr. FengYu Xu designated as the local HIT project manager and Prof. Li Wang as chief engineer (must be under agreement between HIT and SINAP, not done yet till now) .

LBNL-HIT collaboration meeting was held in Harbin at the early of last December, LBNL collaborators, ICST MICE group, representatives from QiHuanCorp., HIT official (Prof. Bin Guo and ShiXian Zheng) and Li Wang from SINAP/Shanghai were present. During the meeting, critical issues related to the coupling magnet were discussed in detail including project management in HIT, design drawings and fabrication procedures. According to the agreement achieved during the meeting:



• The fabrication drawings for the coupling magnets were finished by ICST/HIT at the end of last December. The reviews for the drawings have been performed two times and fed back to the ICST. The updating of cold mass assembly fabrication drawings were completed and delivered to QiHuanCorp., but the revision for the other drawings of the magnet are not finalized yet.

• The 6061-T6 Al mandrel fabrication for the coupling coil 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 is delivered to QiHuan Corp. this week for final machining.

• The fabrication contract for the two MICE coupling magnets excluding the assembly welding of coil cold mass were awarded to QiHuan Corp. and signed last Friday (March. 18) finally.



Forged mandrels and cover plates



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



Design Updating

• Coil size & effects on magnet performance

• Vacuum chamber

• Thermal shields

• Coupling magnet assembly tolerance

• The 3rd cryocooler to be possibly installed



Coil size & effects on magnet performanceCoil size

Previous design value

Practical value

Updated design value Note

Turn-to-turn gap（um）

66 34 40

Layer-to-layer gap（um）

100 74 75

The thickness of fiberglass cloth put between coil layers is 50um. The less epoxy used between turns and layers may improve magnet stabilization and reduce coil quench potential.

• According to coil winding experience gained from 2 test coils and 1 training coil, the following winding parameters were updated for the coupling coil design and will be used for coil winding quality control.

1501.452 mm

Coil inner diameter

≥ 80263 m (81230)281mm (284)103.2 mm (105.6)96166 (168)

Coil length Conductor lengthCoil thicknessLayersTurns/layer

• The updated coil size



• 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.

The increased space will be helpful for the assembly of the coupling magnet.



Effects of coil size on magnet performance

• Effect on coil basic parameters

Coil Length (mm) 284 281

Coil Inner Radius (mm) 750 750

104

96

166

210

595.1

7.47

13.1

4.2K Temp. Margin (K) 0.76 0.77114.514

Coil Thickness (mm) 106

Number of Layers 96

No. Turns per Layer 168

Magnet Current (A) 210

Magnet Self Inductance (H) 607.3

Peak Induction in Coil (T) 7.48

Magnet Stored Energy (MJ) 13.4

Filling factor (A-turn/mm^2) 112.506

The magnet self inductance, peak induction in coil, and magnet stored energy lower down a little bit with increasing of the coil filling factor, and the temp. margin increases, which are good for magnet training.



• Effect on stress in coil cold mass assemblyThe peak stresses in the updated coil cold mass drop down about 4% compared with those in the previous one.

After coil winding (MPa) After cool down (MPa)284x106-168 281x104-166 284x106-168 281x104-166

Shear stress 8.36 7.87 38.5 37.7

Von Mises stress 32 31 81 80.1

Peak stress at coil bottom corners

1041106870Von Mises stress

-101.8-107-67-68Hoop stress

-2.4-2.5-2.96-3.1Radial stress

281x104-166284x106-168281x104-166284x106-168

After cool down (MPa)After coil winding (MPa)Peak stress at the center of coil inner layer

• Effect on quench process and AC losses: <2% (better), negligible



Vacuum chamber

FEA modelDeformation: max. 0.471mm>0.3mm, close to the

dented parts for couplers and vacuum pump ports

Previous design

0.262 mm

0.419 mm

0.471 mm

The outer diameter is enlarged from 2278 mm to 2308 mm for welding the sleeves for installing cold mass supports.



Updated design

FEA modelDeformation: max. 0.253mm<0.3mm, on the

upper neck parts

0.253 mm

0.197 mmAdditional reinforcement ribs

0.169 mm



The Von Mises Stress on the main body of vacuum chamber lowers down a little bit.

Interference with the RF cavity module should be checked.



Thermal shields

Elec-insulation

1st-stage cold head

Upper neck shield

End shield

Inner shield

Outer shield

Copper plate for thermal connection

Flexible connection

8 Shield supports

8 Supports for upper neck shield

Elec-insulation

• The thermal shields are to be conduction-cooled through the upper neck part connected to the 1st-stage cold heads of coolers.

• Copper or Al flexible connections are to release the stress between the main shield and the copper plate due to contraction and weight of shields.

• The temperature differencethroughout the shields should be less than 20 K, and the hot temperature should be no more than 80 K.

• The main shields are to be made of 1100 aluminum, the connection plate to the cooler and thermal intercepts to the cold mass supports are to be made of pure copper with RRR 20.



67K

• The upper neck shield and flexible connections are made of 1100 Al strips with 8 mm thickness:

The temperature difference along the upper neck shield and the flexible connections is about 6.3 K assuming good thermal contact.



Shrinkage of 8mm is unacceptable

Displacement in the vertical direction after cool down (zoomed in 100 times)

4.5mm, how to avoid the constructive interference ?10

The 8mm thick flexible connection made of 1100 aluminum has a large stiffness, and is to pull the main shields upward during cooling down. The displacement of shields in the vertical direction may cause thermal-shorts near the dented parts for RFCC couplers .Reducing the thickness of flexible connections can decrease the stiffness, but it will increase the ΔT throughout the shields. Restricting the deformation will cause large local stress concentration on the flexible connections.



65K

• The upper neck shield and flexible connections are made of copper/Al sheets or copper braid:

The temperature difference along the upper neck shield and the flexible connections is about 4.7 K assuming good thermal contact.



10 100

3Ther

mal

con

duct

ivity

(W/m

*K)

Temperature (K)

0 T 2 T 4 T 6 T

80100

1000

500

If the flexible connections have sufficient flexibility, the main shields will contract towards the mechanical center of the magnet during cool down and will not stress the upper shield parts. There will be little thermal stress in the main shields, and the maximum displacement is 3.67 mm in the outer shield.

The shields will not interfere with the vacuum chamber near the RFCC coupler.

Changing the material of the upper neck shield from Al to copper will improve the thermal conduction of the shields and make the welding easier for the upper neck shield parts, but increase about a weight of 21.8 kg.

10 100

10

100

Ther

mal

con

duct

ivity

(W/m

*K)

Temperature (K)

5356Al,0 T 1100Al,0 T 1100Al,2 T 1100Al,4 T 1100Al,6 T

3

3

500

1100 aluminum

5356 aluminum Copper (RRR=20)



Coupling magnet assembly tolerance

In fabrication contract, the following assembly tolerances are in agreement:

Tolerance range

The longitudinal position of the cryostat center should be the same as the coil center ±0.5 mm to ±1.0 mm

The coupling solenoid cold mass central axis shall be co-axial with the cryostat vacuum vessel axis

± 0.3 mm to ± 1.0 mm

The maximum allowable tilt of the cold mass axis (the magnetic axis) with respect to the axis of the warm bore tube

±0.057 to ±0.069 degree



The 3rd cryocooler to be possibly installed

• The estimated heat loads for the coupling coil according to the current design (operated by two cryo-coolers):

Heat loads at 4.2K (W) Heat loads at 60K (W)

1.73 1.73

0.87 (50%) 1.73 (100%)

Total 2.6 3.46 81.2 108.2Cooling capacity at 4.2K 1.5x2=3.0 W

55x2=110 W

54.1

27.1 (50%)

Calculated 54.1

Contingency 54.1 (100%)

Cooling capacity at 60K

Uncertain contingency and less margin!



Current design To be updated design

3rd cooler to be added considering heat load margin at 4.2K



Connected VCR fittings

Cooling piping system

Heat shield assembly (neck part)

Vacuum chamber (neck part)

Cooling connection (plate size) between the 1st-stage cold-head and shields

• To add the 3rd cryocooler will result in the following changes of design and additional cost:

Heat loads at 60K and 4.2K

Temperature distribution along heat shields w/ and w/o the 3rd cryocoolerinstalled

Stress analyses on vacuum chamber

• The following calculations need to be carried out:

Operation w/ the 3rd cryocooler mounted



Disconnected VCR fittings: to eliminate additional heat load from the 3rd cooler to 4.2K cold mass

Additional G-10 supports

Operation w/o the 3rd cryocooler mounted

Heat load from 300K to the 1st-stage cold heads of cryocoolers through the heat conduction from the SS sleeve of the 3rd cooler and additional G-10 shield supports (~ 4.5 W)

The radiation heat load from vacuum vessel to the heat shields due to enlarged heat shield cold surface (~1W/m^2X? m^2).

The radiation heat load from the lower SS sleeve of the 3rd cooler to the 4.2K cold surface (~ ? W)

• With the 3rd cryocooler uninstalled, and the CC is to be operated by two cryooolers, there will be additional heat leakage:

SS sleeve



ScheduleAccording to the fabrication schedule submitted by QiHuan Corp. early this

week, without considering cryo-test for the coil cold mass in HIT, to assume HIT will provide all the final fabrication drawings by the end of this March and to start procuring all the materials from early of this April, and fabrication process in parallel style, so:

MuCool coil mandrel ready for winding May 19, 2010Completion of MuCool coil winding August 25, 2010MuCool coupling magnet early of March, 20111st MICE coupling magnet end of May, 20112nd MICE coupling magnet end of Sept., 2011



• When will the final fabrication drawings for magnet cryostat be completed and delivered to QiHuan? (block the fabrication, additional cost due to the 3rd cryocooler and HIT available funding, amendment to the signed contract?)

• Possibility of cryo-test for the coil cold masses? When will the cryo-test system be ready? (available manpower and funding in HIT? )

• Contract for welding of the coil cold mass should start as soon as possible?

• The detailed schedule should be discussed face-to-face among HIT, LBNL and QiHuan to make it realistic and achievable as SOON as possible.

Questions:



CommentsThe fabrication contract for two MICE coupling magnets was awarded to QiHuan Corp. and signed on March 18, 2010, and then

• The detailed fabrication schedule should be discussed face-to-face among HIT, LBNL and QiHuan to make it realistic and achievable as SOON as possible.

• The fabrication drawings for magnet cryostat should be finalized and delivered to QiHuan as SOON as possible.

• The fabrication & assembly procedures for some critical parts (coil cold mass, vacuum chamber, cryostat assembly) as well as QA plan (including detailed inspection plan) should be submitted by QiHuan, reviewed and approved by HIT and LBNL before fabrication starts.

• Contract for welding of the coil cold mass should start as SOON as possible.



Possibility of cryo-test for the coil cold masses and when the cryo-test system will be ready in HIT should be explored (available manpower and funding in HIT? )

Test needed to be done

• For the coupling magnet, the cold diodes for quench protection circuit will work in a magnetic field from 1.5 to 2.5T, in which its performance (forwarded voltage, etc.) will be affected. However, how much the effect will be is still a question? Because the performance of the diode directly affect that of QPC (coil safety), the tests for diode performance at 4.2K and in a magnetic field (0 to 3T) should be carried out.

• Originally, the diode tests were planned using the large test coil and cryo-test system in HIT. Considering the current situation in HIT, to propose the tests to be performed in LBNL.



C l i c k t o e d i t c o m p a n y s l o g a n .

mice/mucool coupling magnetsfor final machining. • the fabrication contract for the two mice...

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