Coil parts & Instrumentation issues for LQ/HQ coils tested at Fermilab HQ/LHQ coil parts task force

Introduction Collect all issues related to HQ/LQ coil parts and instrumentation found at Fermilab before, during or after the test Issues found before the test to be verified with the Lab fabricated or instrumented the coil Keep updating the information on issues for old or forthcoming tests Start summarizing findings

LQ/HQ coils tested at Fermilab LQS01a –Strip heater damage, delamination on the inner coil surface LQS01b –Strip heater damage LQS02 –Mixed up voltage tap wiring HQM01 (coil 12) –Coil to IL pole piece short HQM02 (coil 13) –Coil to IL pole piece short –OL heater to coil short HQM03 (coil 14) in preparation to electrical checkout –Coil to OL splice block short –Wires not potted into the LE outer layer splice block

LQS01a Strip heater in coil 7 (PH07A01) was lost during the test –Heater was connected in parallel with other heaters, HFU decay profile slightly changed but was not noticed during the test –Monitoring of HFU discharge was implemented after this test PH07A01 heater was repaired after the test –Exposed area was filled with Stycast and 5-mil Kapton on top of it and cured with pressure. Damaged area of the heater was replaced with a 10-cm long copper wire –The same heater was lost again in LQS01b

LQS01a Delamination of coils inner diameter –Large “bubbles” underneath the large sections of the heaters Rod SG are vulnerable to cool down –Sector D rod SG was lost during the initial cool-down –Additional sensor on each rod could help

HQM02 coil parts & instrumentation issues Pre-test electrical check-out: short found between the coil and the IL LE pole piece -Short location in A10B10 segment, close to B10 -Inner and outer layer pole pieces at LE are in contact -Small axial gap between the LE and RE pole pieces Inner layerOuter layer

HQM02 coil parts & instrumentation issues Both strip heaters on the outer layer developed short to coil after 3 rd quench at 4.6 K  Significant increase of the quench current from ~14 kA to ~15.7 kA  Strip heaters isolated and removed from the magnet protection Was is safe to continue testing ?  Symmetric grounding of both the magnet and strip heaters, as well as 10 mOhm dump resistor should reduce the maximum voltage drop across the coil  Several manual trips and heater provoked quenches performed to analyze noise in signals  Strain gauge data, especially from the bullets, were investigated  Quench current was gradually increased up to 14 kA before quench training was continued

HQM02 coil parts & instrumentation issues When exactly the short developed ?  Active ground fault protection system tripped only after the quench  HFU discharge plot for quench #3 indicated that short developed after the quench was detected (t=0) OL heaters IL heaters

HQM02 coil parts & instrumentation issues When exactly the short developed ?  HFU discharge profile compared to a reference plot Quench # 3Quench # 2

When exactly the short developed ?  Ground fault current in quenches #3 and #18, both at ~ 15.7 kA HQM02 coil parts & instrumentation issues Quench # 3 Quench # 18

HQM02 coil parts & instrumentation issues OL RE

HQM02 coil parts & instrumentation issues 2-mil Kapton ground wrap 3 layers of 5-mil Kapton insulation

HQM02 coil parts & instrumentation issues 11/30/2011 HQM02 inspection results  OL RE spacer-to-end shoe (IL or OL):open  OL RE spacer-to-IL RE spacer: open  IL RE end shoe-to-OL RE end shoe:open  OL RE spacer-to-OL coil:48.99 Ohm  OL RE spacer-to-IL coil:49.12 Ohm  OL RE spacer-to-strip heater (NT):54.8 Ohm  OL RE spacer-to-strip heater (T):3.37 Ohm Heater to coil short developed during the quench Did the spacer-to-coil short develop after the heater failure ?

HQ02 HQ04 HQ13 HQ mm 22.6 mm10.6 mm 18.8 mm

HQM02 coil parts & instrumentation issues OL LE before the test OL LE after the test

HQM03 coil parts & instrumentation issues Preliminary electrical check-out: short found between the coil and the OL LE splice block -Short is located close to B2, could be B2 voltage tap wire pinched between the splice block B2 vtap wire Short location

HQM03 coil parts & instrumentation issues Different technology of splice wiring is used at Fermilab SS foil in Kapton

HQM03 coil parts & instrumentation issues Wires not potted into the LE OL splice block Need to repair (Stycast ?)