pCM Demagnetization & Magnetic Hygiene: Lessons Learned & - - PowerPoint PPT Presentation

Saravan K. Chandrasekaran pCM Workshop 12 January 2017

pCM Demagnetization & Magnetic Hygiene: Lessons Learned & Production Plans

• All components in CM examined from a magnetic perspective

– From studs in string to vacuum vessel (VV)

• Magnetic hygiene document developed

– Captures components, acceptable residual magnetic fields, distances to cavities, etc. – Everything in this document was checked, & demagnetized if necessary, prior to assembly

• VV check and demagnetization a separate task

– Size of VV required development of demagnetization equipment and procedure

• pCM displayed remagnetization during assembly &

installation

– Full cryomodule demagnetized at WS5 & at CMTS

pCM Magnetic History

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• Material selection of components decreased probability of

magnetized components

• Both labs developed procedures for checking and

demagnetizing parts

– Cleanroom assembly parts and tools go through stricter controls

• Cannot be taken off string later
• Difficult to demagnetize as part of string
• PRODUCTION MODULES

– Will use processes developed during pCM – Processes being improved for workflow and timing for FNAL – Batch processing being developed to reduce time for demag

Magnetic hygiene of CM components

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• pCM vacuum vessel demagnetized successfully by both labs

Vacuum vessel demagnetization

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Bavgat cavities >500 mG ↓ <50 mG & uniform Magnitude Longitudinal Bz at cavities >300 mG ↓ <50 mG & uniform

• Final welds performed on both pCMs showed significant

increases in the magnetic fields at the cavities

– Witnessed increase with JLab welding

• pCMs were demagnetized prior to move into test cave
• FNAL pCM demag in cave

– Proof of concept – B<1 mG at cavities, 295 K

pCM demagnetization

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• Fields increased in pCM with CMTS modifications
• pCM was unintentionally magnetized to ~35 mG due to an

incident during 35 A demag

– 65 A demag was performed, and fields < 1 mG at cavities – Measures to prevent incident shall be implemented

• JLab pCM (peak fields)

– ~15 mG after assembly – ~6 mG after 35 A demag – ~4.5 mG after 65 A demag

pCM demagnetization

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• Active cancellation was not needed for the single CM
• CMTS has background fields that change polarity & may

cause longitudinal fields to cancel themselves

• Need to examine this further
• SLAC tunnel?

– Current field maps only for a section of tunnel

pCM active cancellation

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• VV shall be demagnetized after all necessary welding and

mechanical modifications are completed

• CMs shall be demagnetized using 65 A cycle
• A new belt-type demagnetization coil system developed to

reuse coils

• Each lab shall have two sets of coils

– FNAL to use one coil at VV demag station and one coil at CMTS

• All four sets of coils to be shipped to SLAC for use during

commissioning

– Specifications and details for demagnetization system shall be provided to SLAC installation & commissioning groups

Production vacuum vessels & CMs

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• Magnetic hygiene program implemented at both labs for pCM

demonstrated the possibility of obtaining low fields at cavities

– This is to continue for production

• pCM instrumentation was critical in knowing the increases in

magnetic fields, especially during assembly

– Production modules do not have this luxury – All modules will therefore be demagnetized just prior to cool down at CMTS & SLAC tunnel

• Active cancellation is to be further examined

Discussion

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