pCM Demagnetization & Magnetic Hygiene: Lessons Learned & Production Plans Saravan K. Chandrasekaran pCM Workshop 12 January 2017
pCM Magnetic History • 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 2 1/12/2017 S.K. Chandrasekaran | pCM Demag & Mag Hygiene
Magnetic hygiene of CM components • 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 3 1/12/2017 S.K. Chandrasekaran | pCM Demag & Mag Hygiene
Vacuum vessel demagnetization • pCM vacuum vessel demagnetized successfully by both labs Magnitude Longitudinal B avg at cavities >500 mG B z at cavities >300 mG ↓ ↓ <50 mG & uniform <50 mG & uniform 4 1/12/2017 S.K. Chandrasekaran | pCM Demag & Mag Hygiene
pCM demagnetization • 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 5 1/12/2017 S.K. Chandrasekaran | pCM Demag & Mag Hygiene
pCM demagnetization • 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 6 1/12/2017 S.K. Chandrasekaran | pCM Demag & Mag Hygiene
pCM active cancellation • 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 7 1/12/2017 S.K. Chandrasekaran | pCM Demag & Mag Hygiene
Production vacuum vessels & CMs • 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 8 1/12/2017 S.K. Chandrasekaran | pCM Demag & Mag Hygiene
Discussion • 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 9 1/12/2017 S.K. Chandrasekaran | pCM Demag & Mag Hygiene
Recommend
More recommend
