S. Feher MICE Magnet Readiness Review RAL, June 28th, 2016 SS QPS S. Feher MICE Magnet Readiness Review RAL, June 28th, 2016

Sandor Feher | MICE Magnet Rediness Review (Ral, June 28, 2016) Outline Status of SS electrical circuits Operational Requirements Modified magnet protection scheme and operation of the Power Supplies Conclusions June 28, 2016 Sandor Feher | MICE Magnet Rediness Review (Ral, June 28, 2016)

Status of SS Electrical Circuit SSD Known Damage: LTS lead between the HTS lead and the M1 coil is open Internal diode pack connection is open for M1 At one side of the M1 LTS lead is shorted to ground The two LTS leads for M1 are connected to each other; finite resistance M2 coil is connected to M1 coil therefore connected to ground with ~ 1.3 kΩ resistance Possible Future Degradations: M2 ground connection becomes more solid; less resistance Physical damage to M2 is worse than we currently believe He-to-Vacuum leak occurs at M1/M2 feedthrough (between the cold mass and insulating vacuum) SSU No Known Issues June 28, 2016 Sandor Feher | MICE Magnet Rediness Review (Ral, June 28, 2016)

Status of SSD Electrical Circuit Cold Mass Shell LTSd LTSa LTSb HTS R1 LTSc LTS/N PSU External Diode Pack Internal Diode Pack M1 R1 R2 Energy Absorber LTSc LTS/N HTS LTSa LTSb LTSd Feedthroughs LTSd LTSa LTSb HTS R1 LTSc LTS/N PSU External Diode Pack Internal Diode Pack M2 R1 R2 Energy Absorber LTSc LTS/N HTS LTSa LTSb LTSd Vacuum Shell June 28, 2016 Sandor Feher | MICE Magnet Rediness Review (Ral, June 28, 2016)

Operational Requirements By design: Powering Current measurement accuracy 2x10-4 (new transductors being installed) Fail safe powering; no harm to equipment (Magnet, leads, PS itself) and personnel Magnet circuit protection Coils are self protected; if the coil quenches it is sufficient to turn off the PS HTS and LTS leads during quench: keep the hot spot temperature below 300 K Coils hot spot temperature during quench less then 120 K Magnet peak voltage relative to ground below 1600 V; for ECE circuit internal diode pack is needed to fulfill this requirement June 28, 2016 Sandor Feher | MICE Magnet Rediness Review (Ral, June 28, 2016)

Operational Requirements Practical reasons: Safe cold HV withstand to ground values measured for SSU and SSD were ~ 150 V ( breaks down ~ 200 V) Localized at the feedthrough (air-to-vacuum) region HTS lead voltage less than 3 mV QPS HTS lead quench detection threshold value is set at 1 mV Keep the LTS lead voltages during quench as low as possible Apply low detection threshold values to keep the hot spot temperature as low as possible No clear understanding (as built) what are the lead dimensions and/or cooling conditions, consequently quench integral value limits are not known. June 28, 2016 Sandor Feher | MICE Magnet Rediness Review (Ral, June 28, 2016)

Sandor Feher | MICE Magnet Rediness Review (Ral, June 28, 2016) QP Modifications Existing QPS was reconfigured: Introduced dI/dt signals for all the magnet currents Every magnet current is measured with transductors The dI/dt signal is obtained with digital signal processing of the magnet current signal Quench detection of the M1 and M2 magnets are using Wcoil – const * dI/dt signals with low threshold values; the goal is to be at least less than 100 mV Separate protection processor is used for LTS and HTS leads/magnet circuit Second FPGA card provides additional trigger to open the external diode packs for each magnet circuit separately June 28, 2016 Sandor Feher | MICE Magnet Rediness Review (Ral, June 28, 2016)

Sandor Feher | MICE Magnet Rediness Review (Ral, June 28, 2016) Coil Protection SSU M1 and M2 is using Wcoil – const * dI/dt signals E1-C-E2 is using Half – Half bucked half coil signals SSD M2 is using Wcoil – const * dI/dt signals June 28, 2016 Sandor Feher | MICE Magnet Rediness Review (Ral, June 28, 2016)

PS system Modifications Redundant contactors were implemented for the main switches that open when quench is detected External diode packs, dump resistors and additional contactors were procured and installed June 28, 2016 Sandor Feher | MICE Magnet Rediness Review (Ral, June 28, 2016)

Sandor Feher | MICE Magnet Rediness Review (Ral, June 28, 2016)

Sandor Feher | MICE Magnet Rediness Review (Ral, June 28, 2016)

Sandor Feher | MICE Magnet Rediness Review (Ral, June 28, 2016) END June 28, 2016 Sandor Feher | MICE Magnet Rediness Review (Ral, June 28, 2016)

Sandor Feher | MICE Magnet Rediness Review (Ral, June 28, 2016) Protection Issues Cold Mass Shell LTSd LTSa LTSb HTS R1 LTSc LTS/N PSU External Diode Pack Internal Diode Pack Feedthroughs R1 R2 Energy Absorber LTSc LTS/N HTS LTSa LTSb LTSd Vacuum Shell Direct protection of LTSa and LTSb segments with V-taps LTSd is only protected with the magnet; low threshold settings are required to lower the hot spot temperature LTS/N easily can be overheated Internal diode/resistor pack does not extract enough energy June 28, 2016 Sandor Feher | MICE Magnet Rediness Review (Ral, June 28, 2016)

Proposed Operational Configuration Cold Mass Shell LTSd LTSa LTSb HTS R1 LTSc LTS/N PSU External Diode Pack Internal Diode Pack Feedthroughs R1 R2 Energy Absorber LTSc LTS/N HTS LTSa LTSb LTSd Vacuum Shell Carefully selected External diode pack (M1 and M2 ~ 5 V, for ECE ~ 10 V), and R2 (0.5 Ω) Contactor for the External diode pack is open; not to interfere with PS operation June 28, 2016 Sandor Feher | MICE Magnet Rediness Review (Ral, June 28, 2016)

Different Quench and Failure Scenarios Cold Mass Shell LTSd LTSa LTSb HTS R1 LTSc LTS/N PSU External Diode Pack Internal Diode Pack Feedthroughs R1 R2 Energy Absorber LTSc LTS/N HTS LTSa LTSb LTSd Vacuum Shell Magnet quench HTS lead quench LTSa or LTSb quench LTSd quench Ground fault PS malfunction June 28, 2016 Sandor Feher | MICE Magnet Rediness Review (Ral, June 28, 2016)

Sandor Feher | MICE Magnet Rediness Review (Ral, June 28, 2016) Magnet Quench Cold Mass Shell LTSd LTSa LTSb HTS R1 LTSc LTS/N PSU External Diode Pack Internal Diode Pack Feedthroughs R1 R2 Energy Absorber LTSc LTS/N HTS LTSa LTSb LTSd Vacuum Shell Magnet quench is detected PS Contactors open for all circuits: M1 (for SSD M1 is floating), M2, ECE External diode pack contactors close Diode Pack is sized to keep the internal diode pack open (M1 and M2 ~ 5 V, for ECE ~ 10 V); current is circulated through the external diode pack During magnet quench HTS or LTSa or LTSb quench occurs External diode pack contactor opens for the particular circuit R2 resistor is sized (0.5 Ω) to keep the max voltage below 150 V in a case LTSc or LTS/N opens Ground fault occurs during quench No additional action – no influence on maximum external voltage June 28, 2016 Sandor Feher | MICE Magnet Rediness Review (Ral, June 28, 2016)

HTS or LTSa or LTSb Quenches Cold Mass Shell LTSd LTSa LTSb HTS R1 LTSc LTS/N PSU External Diode Pack Internal Diode Pack Feedthroughs R1 R2 Energy Absorber LTSc LTS/N HTS LTSa LTSb LTSd Vacuum Shell HTS or LTSa or LTSb quench is detected PS Contactors open for all circuits: M1 (for SSD M1 is floating), M2, ECE External diode pack contactor remain open for the quenching circuit the rest of them will be closed – this requires major modifications of the QPS; more channels needed R2 resistor is sized to keep the max voltage below 150 V in case LTSc or LTS/N opens During HTS or LTSa or LTSb quench the magnet also quenches No additional action – the current decay will be faster Ground fault occurs during quench No additional action – no influence on maximum external voltage June 28, 2016 Sandor Feher | MICE Magnet Rediness Review (Ral, June 28, 2016)

Sandor Feher | MICE Magnet Rediness Review (Ral, June 28, 2016) LTSd Quenches Cold Mass Shell LTSd LTSa LTSb HTS R1 LTSc LTS/N PSU External Diode Pack Internal Diode Pack Feedthroughs R1 R2 Energy Absorber LTSc LTS/N HTS LTSa LTSb LTSd Vacuum Shell LTSd quench is detected This quench can not be separated from a magnet quench – very low quench detection threshold is required; dI/dt based quench detection system for M1 & M2 and significantly lower threshold for the ECE half coil based detection system (more filtering) are needed PS Contactors open for all circuits: M1 (for SSD M1 is floating), M2, ECE External diode pack contactor remain open for the quenching circuit the rest of them will be closed – R2 resistor is sized to keep the max voltage below 150 V in case LTSc or LTS/N opens During LTSd quench the magnet also quenches No additional action – the current decay will be faster Ground fault occurs during quench No additional action – no influence on the maximum external voltage June 28, 2016 Sandor Feher | MICE Magnet Rediness Review (Ral, June 28, 2016)

Ground Fault or PS Malfunction Cold Mass Shell LTSd LTSa LTSb HTS R1 LTSc LTS/N PSU External Diode Pack Internal Diode Pack Feedthroughs R1 R2 Energy Absorber LTSc LTS/N HTS LTSa LTSb LTSd Vacuum Shell Ground fault or PS malfunction PS Contactors open for all circuits: M1 (for SSD M1 is floating), M2, ECE External diode pack contactors close Diode Pack is sized to keep the internal diode pack closed (M1 and M2 ~ 5 V, for ECE ~ 10 V); current is circulated through the external diode pack During ground fault or PS malfunction HTS or LTSa or LTSb or LTSd quench occurs External diode pack contactor opens for the particular circuit R2 resistor is sized (0.5 Ω) to keep the max voltage below 150 V in a case LTSc or LTS/N opens June 28, 2016 Sandor Feher | MICE Magnet Rediness Review (Ral, June 28, 2016)

New SSD QPS Configuration For the newly designed SSD cold mass we will implement several changes: Every coil will have two center V-taps (one primary and one redundant) All coils detection circuit will utilize Half Coil 1 – Half coil 2 signal with low threshold values There will be separate V-taps for the LTS and HTS segments At every V-tap locations will be two V-taps (one primary and one redundant) External dump system will be used Dump resistor will be adjusted to the HV withstand values Every coil will have two heaters (one primary and one redundant) Once LTS, HTS or magnet quench is detected the heaters will be energized to initiate a magnet quench For ground fault and PS failure cases slow ramp down will be initiated External diode pack will be used June 28, 2016 Sandor Feher | MICE Magnet Rediness Review (Ral, June 28, 2016)

Sandor Feher | MICE Magnet Rediness Review (Ral, June 28, 2016) Conclusions The proposed PS and QPS configuration will minimize the risk of loosing the magnet circuits Requires major modifications of the QPS June 28, 2016 Sandor Feher | MICE Magnet Rediness Review (Ral, June 28, 2016)