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

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 layer Outer layer


Both strip heaters on the outer layer developed short to coil after 3rd 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


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


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


Quench # 3

Quench # 18


OL RE


2-mil Kapton ground wrap

3 layers of 5-mil Kapton insulation


11/30/2011HQM02 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

HQ14

26.8 mm

22.6 mm 10.6 mm

18.8 mm

HQM02 coil parts & instrumentation issuesOL LE before the test

OL LE after the test


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


Different technology of splice wiring is used at Fermilab

SS foil in Kapton


• Wires not potted into the LE OL splice block

• Need to repair (Stycast ?)

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

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