MICE Spectrometer Solenoids Step IV running

MICE Spectrometer Solenoids Remember: Both magnets met the full specification at the vendor and were fully mapped. – Cryogenic operation was very good. Both magnets had significant cooling headroom (SS2 more than SS1) SS2 (in upstream position of the beam line – SSU) has reached full operating current at RAL, but full training (soak, solenoid mode) has not been completed. – Cryogenic headroom ~ 50% (3W) – Vacuum excellent SS1 (in downstream position – SSD) had a M1 lead failure during training. – Cryogenic headroom ~<25% (~1W) – Vacuum excellent, but some issues if power feedthrough gets cold What is the path forward for Step IV? 2MICE Project Board April 5, 2016 RAL Alan Bross

Reminder: Basic design 3MICE Project Board April 5, 2016 RAL Alan Bross 5 2-stage CCs 1 single-stage CC 5 Coils Max current ~300A High inductance H M2M1E2CE1 M1 in SSD Is DEAD

Power delivery system 2 Vacuum feedthroughs bring power into vacuum space – One for ECE, one for M1 and M2 Copper leads to HTS – IL/A = 3.6 X 10 6 A/m HTS: – HTS A (M1, M2, C) and 250A E1 and E2 LTS: – Vacuum feedthrough: Proprietary Wang design based on SSC superconductor – Inside He space: Cu stabilized conductor 4MICE Project Board April 5, 2016 RAL Alan Bross

On BST, SSD became Self-aware SS magnet protection and powering scheme after the September 13th, 2015 incident has been re- visited and, during the investigation process, it was realized that there are several potential problems in the protection and powering scheme that need to be addressed. Although there is no solution that will provide a perfect protection scheme, the existing system has been significantly improved upon. The improved protection scheme follows. 5MICE Project Board April 5, 2016 RAL Alan Bross

E-C-E Power system II 6MICE Project Board April 5, 2016 RAL Alan Bross

M1, M2 Power System II 7MICE Project Board April 5, 2016 RAL Alan Bross

External Dump Pack Resistors Centre Coil Resistor Trim Coil Resistor Match Coil Resistor MICE Project Board April 5, 2016 RAL Alan Bross 8

Operation During powering of the magnet circuits all the switches are closed. Several different scenarios can occur and the following actions will be taken: – If magnet quench or ground fault on a circuit is detected: For all three circuits (M1, M2, E-C-E) the two main switches (primary and redundant) open – all together 6 switches open. – If HTS or LTS quench occur: the External Dump Pack (EDP) switch of the circuit that experienced the lead quench opens. For E-C-E resistors located near magnet; M1 & M2 in RR2 In order to decrease the detection voltage threshold significantly the protection and monitoring scheme has changed: 9MICE Project Board April 5, 2016 RAL Alan Bross

Operation II A DCCT (direct-current current transformer) based current readout system was added to precisely measure the magnet current values and provide dI/dt signals for QPS: The “old” QPS still provides a quench trigger signal if any coil, HTS or LTS leads show resistive voltages. The protection scheme has changed: – A dI/dt based protection (using the DCCT system) scheme with mutual coil balancing is used for SSD M2 and SSD E-C-E and for SSU M1 and SSU M2 circuits that monitors the magnet coil voltages; – SSU E-C-E Half-Half coil based protection circuit threshold value was significantly lowered (by lowering the noise level of the circuit); – An additional new protection layer (secondary) was added to the HTS and LTS protection scheme. It will produce a separate trigger for each circuit (M1, M2 or E-C-E) if HTS or LTS lead quench occur in that circuit. This trigger will be used to open the EDP for the circuit that detected HTS or LTS lead quench 10MICE Project Board April 5, 2016 RAL Alan Bross

Operations III NO additional individual “training” of either SSU or SSD is planed Obviously, we have not “trained” the channel: SSU- FC-SSD. – Additional quenches must be assumed This presents the greatest risk to SSD because of potential damage to the power feedthrough for M1/M2 on SSD (vacuum to He space) Initial SSD operations limited to E-C-E 11MICE Project Board April 5, 2016 RAL Alan Bross

Fundamental issue with SSD 12MICE Project Board April 5, 2016 RAL Alan Bross M2 of SSD looks fine, but given that we do not know in detail the condition of this feedthrough, running first with M2 off is envisioned. However, any quench in SSD (from E-C-E) will produce a pressure pulse – Has been checked once and feedthrough held (still vac tight). – Next time…????

Conclusions SSU is in good shape – Magnetically – Cryogenically – Vacuum SSD not so much. – M1 is not retrievable – Cryogenic headroom OK, but worse – Vacuum is fine The new PS/QD/QPS system will have a significant upgrade and will protect these magnets as well as possible (limited by the magnets intrinsic design). 13MICE Project Board April 5, 2016 RAL Alan Bross

Conclusions Installations of components, re-configuration of the QPS modules and finalization of the DCCT system input to the QD system is ongoing. Final install and initial commissioning is scheduled to begin on April 27 th. A second round of work in May will be needed to full commission the SS PS/QD/QPS systems for full magnet operations. SSs ready in June for Step IV operations 14MICE Project Board April 5, 2016 RAL Alan Bross