HQ02b Meeting 4/24/14High Miits Study – G. Sabbi 1 High MIITs Study GianLuca Sabbi Video meeting on HQ02b test results – April 24, 2014

HQ02b Meeting 4/24/14High Miits Study – G. Sabbi 2 Summary of HQ02b High MIITs Study

HQ02b Meeting 4/24/14High Miits Study – G. Sabbi 3 All training performed at 1.9K, divided in two phases before/after CLIQ provoked quenches. MIITs for training and initial (CLIQ) quench protection study were kept below 11 (few quenches around 12) Based on HQ02a2 experience showing detraining at ~12 Miits Reached plateau with consistent quenching in same coil (#20) high field area (IL pole) Plateau current ~17.1kA, ~1 kA above HQ02a, much faster training Well above 4.2K SSL (16.5kA) Also performed one verification quench at 4.2K 15.8kA (96% SSL), C17, IL/OL transition Consistent (current, location) with last HQ02a verification at 4.5K 300A lower than initial HQ02a quench at 4.5K (16.1kA, 98%) Initial training/performance baseline

HQ02b Meeting 4/24/14High Miits Study – G. Sabbi 4 1. High MIITs with natural quenches Initial plan was to use natural quenches in the high field area Based on HQ02a training - desired conditions reached at the (very) end Planning to increase MIITs in a controlled way using current flat top (delaying heaters/extraction) then trigger standard protection for consistent decay and energy extraction (also to help recovery time) Some “learning curve” controlling delays led to gradual increase Already indicated that current decay was faster than we thought With much increased delays (factor 2-3) reached 13.5, then 15.8 Miits Last point with 66 ms delay effectively equivalent to no protection Allowed further characterization of detraining in relation to high miits quenches – however, not particularly relevant or of general applicability We were to use subsequent quenches for partial retraining Despite “ideal” conditions, obtained little information on degradation MIITs/temperature limited by magnet and setup (can we improve?) Retraining and 4.2K verification limited by recovery time

HQ02b Meeting 4/24/14High Miits Study – G. Sabbi 5 2. High MIITs with 11 kA quenches Provoked quenches at 11 kA using IL heater Quenches were started in a different coil (16) to differentiate from previous phase involving higher current, natural quenches in coil 20 High field area quenches first – again good conditions for test Current decay still too fast, but reached 19 Miits with 300 ms delay and some system reconfiguration (from CLIQ setting) to help PS reach maximum voltage and slow down current decay Final conditions worse than a “no protection” case at this current Estimating hot spot temperature increases by about 50K from previous step (taking into account lower current/field) to about 300K Verification quenches indicate no effect on coil 16 (retraining continues in coil 20, helping characterization of previous step) Again, MIITs/temperature limited by magnet and setup Useful to put some lower boundary on degradation, but full retraining and/or 4.5K quench would have allowed better characterization

HQ02b Meeting 4/24/14High Miits Study – G. Sabbi 6 3. High MIITs with 6 kA quenches Further decreased current to 6kA and increased delays attempting to reach higher MIITs (slower propagation/current decay at lower field) Quenches were started in a different coil (17) to differentiate from previous phases Initially using IL heater, again allowing early quench in high field area Current decay still too fast, but reached up to 21 Miits with 600 ms delay Equivalent to infinite delay, no further increase in MIITs possible No verification at this MIITs level – lack of time and estimated temperature not higher than previous step (due to lower field) Attempted spot heater quench with 650 ms delay (slower propagation) Obtained 25 MIITs corresponding to another estimated 50K step Verification quench at 1.9K in coil 17 at 15.8kA: detraining of >8% No time to retrain Verification quench at 4.5K: coil 17, 15.4kA to be compared with previous level of 15.8kA (93% SSL instead than 96% SSL)

HQ02b Meeting 4/24/14High Miits Study – G. Sabbi 7 Summary and next steps As “expected”, experiment conditions were difficult and unpredictable from both the magnet and the facility standpoint We managed to react quickly and get some very useful data Special thanks to test facility/cryogenics team, Hugo, Emmanuele, Tiina, Ezio, Maxim In principle, additional/finer characterization should be possible Additional testing effort would provide a well worth return on the magnet development/optimization investment Also requires better understanding, comparison, optimization & upgrades from the test facility and cryogenics standpoint Of course, the difficulties we encountered in reaching high MIITs are actually very good news from the general magnet protection standpoint HQ02b quench protection studies (high MIITs, CLIQ) will likely have major implications for protection of QXF and high field magnets in general Starting next Tuesday…

HQ02b Meeting 4/24/14High Miits Study – G. Sabbi 8 Coil and v-tap configuration

HQ02b Meeting 4/24/14High Miits Study – G. Sabbi 9 HQ Spot heater information (Maxim) 6kA spot heater quench obtained using 6 A, 1 s pulse