Spectrometer Solenoid Fabrication & Testing Update

Spectrometer Solenoid Fabrication & Testing

Update

Steve VirostekLawrence Berkeley National Lab

MICE Collaboration Meeting #26 University of California at Riverside

Steve Virostek -- Lawrence Berkeley National Laboratory -- March 26, 2010

MICE Spectrometer Solenoid Fabrication and Testing Update

MICE Cooling Channel Layout

Spectrometer Solenoid #1 (ready for reassembly)

Spectrometer Solenoid #2 (testing in progress)



Topics

•Technical review

•Magnet 2 modifications

•Magnet 2 cool down and training

•Coil connection failure

•Magnet leads testing

•Magnet 1 update

•Upcoming task schedule



Magnet Status Summary

•Modifications to Magnet 2 including adding of a single stage cryocooler were completed at the end of Feb. ‘10

•Several delays in reassembly were caused by vacuum leaks in lead test apparatus, vendor extended illness, redesign of the warm leads, and leaks in the magnet vacuum vessel

•Six coil training runs were completed last week

•An open-circuit was found in the internal connection of one of the leads for the M2 coil late last week

•Magnet will remain cold through next week in order to complete additional power supply and thermal tests

•Minimal disassembly will be required to assess M2 issue



MICE Internal Technical Review

•Spectrometer Solenoid technical review was held on November 18-19, 2009 at LBNL

•Review committee: Pasquale Fabbricatore (chair), Amalia Ballarino, Elwyn Baynham, Tom Bradshaw, Mike Courthold, and Chris White; Alain Blondel and Andy Nichols (ex officio)

•The committee came up with several recommendations including the following:- Approved the adding of a single stage cooler to Magnet 2- Recommended additional thermal modeling of the system- Advised installing additional magnet instrumentation- Suggested Magnet 2 test results be used to determine the final modifications to Magnet 1



Magnet 2 Modification Summary

•A modification to Magnet 2 has been carried out which adds a single stage cryocooler to provide additional cooling to the HTS leads and didn’t require full magnet disassembly

•The single-stage Cryomech AL330 cooler provides 170 W at 55 K and required modifications only in the “turret” area

•The added cooling power lowered the HTS lead temperature sufficiently to prevent lead burnout

•Based on results of the lead tests, the design of the warm leads was modified to reduce the I2R heat load to the 1st stage of the cryocoolers

•Additional instrumentation has also been incorporated



Original Magnet 2 Configuration

HTS leads

Cold head 1st stage

Radiation shield

Fill & vent lines

Cold mass



Magnet 2 with Added Cryocooler

Single-stage cooler

Thermal link

HTS leads



Modification Details

Added turret space

Access port



Magnet 2 Single Stage Cooler

Single stage cooler and flexible copper thermal link installed in Magnet 2



Installed Leads in Magnet 2



Vacuum Feedthrough for Magnet Leads

Area of vacuum leak



Vacuum Guard for Leaking FeedthroughLead vacuum

guard



Vacuum Pumping of the MagnetReassembled turret (single stage cooler on right)

Mechanical pump with cold trap and increased diameter connection



•The magnet was successfully cooled down after the vacuum leak in the lead feedthrough was corrected

•The single stage cooler resulted in 30-35K lower temperatures at the upper end of the HTS leads

•The shield temperatures reached levels that are 20-25K lower than the previous cooldown

•Overall, the addition of the single stage cooler has had the desired effect

•With all 5 coils connected in series, the following current levels were reached during training: 165 A, 219 A, 238 A, 253 A and 257 A (165 A result likely a power supply issue)

Magnet 2 Training and Testing Results



•After the last training run, it was found that one of the connections to the M2 coil was open circuit

•Based on the voltage taps, the failure occurred between the HTS lead lower end and the internal connection to the coil

•With the magnet cold, testing has continued on other fronts

•An additional training run on coils E1, C and E2 (in series) reached a current of 270 A

•With E1, C and E2 at 150 A, the currents in E1 and E2 were successfully trimmed by ±50A using the 60 A supplies

•The PS ramp down circuits were successfully tested

•Assessment of the LHe boil off rate will be made on Monday

Magnet 2 Training and Testing Results



•Failed connection to M2 to be assessed within 1 to 2 weeks by grinding off an access window on the magnet turret

•If the failure is accessible, repairs will be made and the magnet reassembled for cooldown and training completion

•If the repair requires removal of the cold mass (more likely), then efforts will move to complete Magnet 1 first

•Subsequent reassembly of Magnet 2 would include all of the modifications incorporated on Magnet 1

•Final assessment of Magnet 2 thermal performance not yet complete – should have more information next week (addition of a 4th 2-stage cooler may be required)

Magnet 2 Repair Scenarios



Magnet Quench during Training



Magnet Thermal Modeling

•FEA model of thermal shield, 1st stage plate and HTS leads

•Proposed Magnet 1 modifications are also being modeled



Magnet Thermal Modeling• Parametric studies are being conducted to calculate the temperature profile in the 1st stage copper plate

• Modeling is being used to help determine the optimum configuration of coolers for Magnet 1

1st stage Cu plate model



Magnet Leads Testing

•A series of off line lead tests were conducted in order to characterize the warm leads and verify the performance of the HTS leads at up to 275 A

•The temperature drops across the cooler drop-in joint, the intercepts for the room temperature leads and the copper between the leads and the cooler were measured

•The voltage drops along the leads were also measured

•The resistive heating in the warm leads was found to be higher than originally predicted; a modified design has been incorporated into Magnet 2



Cryocooler Setup for Lead Test

1st Stage heater and Tapered Plate

2nd Stage heater and CondenserPT-415 Dropin Cooler



Magnet Lead Test

HTS lead

1st stageplate

Thermalconnection



Cooler Performance with Two IL/A Leads

24

7065605550454035302.5

3.0

3.5

4.0

4.5

5.0

5.5

T2 (Q1=0)T2 (Q1=21W)T2 (Q1=42W)T2 (Q1=63W)T2 (Q1=84W)Lead 1aLead 1b

First Stage Temperature (K)

Sec

ond

Sta

ge T

emp

erat

ure

(K

)

Q2 = 0

Q2 = 0.5 W

Q2 = 1.0 W

Q2 = 1.5 W

Q2 = 2.0 W

Q2 = 2.5 W

Q2 = 3.0 W

Lead 1aI = 01= 275 AI = 275 A + 20 W

Lead 1bI = 0I = 275 AI = 275 A + 30 W

Lead 1aIL/A = 5.3x10^6

Lead 1bIL/A = 3.1x10^6

Not in Equilibrium



Observations from the Cooler Tests

•The I2R heating for the original copper leads used in Magnet 2 was found to be too high (IL/A=5.3x106 A/m)

•The leads were redesigned with an IL/A of 3.0x106 A/m

•The new design reduces the I2R heating from 27 watts/lead to 11 watts/lead (at 275 A)

•The ΔT in the cooler drop-in joint was 1 to 2 K, and the ΔT from the leads to the 1st stage copper plate was ~1 K

•The 1st stage copper plate used in the leads test was likely too thin; the copper plate in the spectrometer solenoid is sufficiently thick with the addition of the single stage cooler



Magnet 1 Modification Summary

• implement ideas to improve thermal connection between coolers and shield and lower cold mass support intercept temperature

•use copper sheets rather than Al cylinders and straps•use 1100Al strips outside of shield to improve heat conduction

• make preparations for using a 4th 2-stage cooler•augment the single-stage cooler to solve both thermal problems

•decision to add 5th cooler depends on outcome of Magnet 2 tests

• modify cold mass fill pipe to facilitate clearing a blockage should one occur



Magnet 1 Cold Mass

Added port for possible 4th 2-stage cooler



Magnet 1 Shield

• Corresponding hole for 4th 2-stage cooler added to shield

• shield is also being “beefed up” locally to improve heat transfer to edges– this is where cold-mass

support intermediate temperature point is connected

– extra heat load from higher temperature at this point is burden for stage 2 of coolers

•probably more of an issue than bulk radiation load

Attachment point for LN2 reservoir

New connection for cooler added

Area where cold-mass support intercept attached



Heat Shield Thermal Connections• Previous attempt to improve thermal connection

between stage 1 of coolers and shield was a failure

– aluminum bands were even worse than original copper strips

– next iteration will make connectionsbetween 1st stage copper plates and shield with thick copper sheets



2-Stage Cooler Modification

Top view:

• A fourth 2-stage cooler could be added as shown below– still leaves room for the single-stage cooler

Side view:

Single stage cooler

4th 2-stage cooler



Schedule Overview (Path 1)



Schedule Overview (Path 2)



• Lead tests resulted in a new warm lead design

• Fixes to Magnet 2 were implemented, and magnet training continued

• The added single-stage cooler solved the HTS lead problem and lowered the shield temperature

• A failure occurred in the connection to the M2 coil

• Assessment of the problem should be completed in the next 2 weeks

• If the problem is serious, efforts will move to the completion of Magnet 1

Summary

Spectrometer Solenoid Fabrication & Testing Update

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