Protection study options for HQ01e-3 Tiina Salmi QXF meeting, 27 Nov 2012

Outline Proposals: 1.Protection heater delay at 14 kA / 80% short sample limit 2.Current decay after outer layer protection heater activation: Study MIITs vs. operating current 3.Normal zone propagation velocity 4.Options for high MIITs quenches Summary Time for discussion 2

1. PROTECTION HEATER DELAY 3

Protection heater delay at high current I/Iss = 80%, 14 kA, or the highest current possible based on HQ performance PH voltage 230 V Set the protection delay to 15 ms (to see quench starts also in lower field areas) Fire one PH circuit (use other circuits and R dump to protect) Measure the delay to quench in various segments of the coils Test all the 4 PH circuits (2IL/2OL): 4 quenches Low risk for excessive MIITs or high cryostat pressure 4 time line Fire PH Q PS Off, fire other PH, activate R dump Prot. delay 15 ms t det PH delay

2. PROVOKED PROTECTION WITH OL PH: MIITS VS. OPERATING CURRENT 5

Concept Real quench protected with only OL PH Test: Provoked quench to estimate MIITs decay Difference to real quench: MIITs decay due to PH + quench back (No initial quench) MIITs total = MIITs det + MIITs decay’ MIITs det : I mag ~constant, easy to estimate for various t det MIITs decay’ : I mag decay due to initial quench + PH + quenchback PS off Fire OL PH Test result: MIITs decay vs. I mag 6 Conservative estimation

Test procedure 1.Deactivate IL PH and R dump 2.Set OL PH voltage to 250 V (nominal setting) – Or highest possible based on hi-pot performance 3.Ramp to a constant I mag – Start with 5 kA – Increase 1.5 kA for each quench 4.Provoke the protection trigger: – Fire OL PH and switch off PS 5.Measure MIITs decay after the trigger 6.Monitor cryostat pressure and MIITs decay (T hotspot ) -Terminate the test if approaching safe limits (t.b.d.) -E cryo = LI mag 2 /2 7.Verification with a spontaneous quench using regular delay and ramp procedure if MIITS are above 14 (t.b.d.) 7

Advantages Controlled, gradual increase in E cryo and MIITs  Reduced risk to test facility and magnet Conservative estimation of MIITs for real quench: Sum MIITs decay and MIITs for an estimated detection time No initial quench in the magnet  Lower total MIITs and T hotspot The first comparison with HQ02 can be done at low current and low MIITs 8

HQ01e-3 test: Situation Only one OL strip is connected in each coil – 4 out of 8 strips in OL are disconnected due to electrical problems – In IL 7 strips out of 8 are connected Proposal: Perform this test using only the available 4 OL PH strips (out of 8) – Establish the test procedure – Also, this probes the redundancy requirement, which states that an accelerator magnet should be protectable with only 50% of heaters working Total number of quenches depends on the pressure rise in the cryostat – Max 8 quenches, if I mag up to 15.5 kA, + verification quench(es) Data on cryostat pressure vs. E cryo useful for the high MIITs quenches (discussed later) 9

3. NORMAL ZONE PROPAGATION VELOCITY 10

Quench propagation velocity Spontaneous quenches with progressively increased protection delay to allow time for normal zone propagation in pole-turn voltage tap signals Gaining  1 MIITs per step, up to  16 MIITs, or per MTF capabilities   4-5 ms additional protection delay per step at 15 kA quench current 3-4 study quenches + 1 verification quench Note: if for some reason the magnet consistently quenches in C7 multi-turn, we skip the above part and proceed with the rest of MIITs studies 11 time line Q PS Off, fire other PH, activate R dump Prot. delay t det

4. MORE OPTIONS FOR HIGH MIITS QUENCHES 12

Options for high MIITs quenches IF safe MTF range established and magnet not degraded: 1)Spontaneous quench with only OL PH and R dump, to see the additional MIITs (expected Miits) (1 quench) 2)Spontaneous quenches with delayed R dump Info about cryostat pressure vs. E cryo useful for defining the delay Ultimate goal to delay R dump beyond the end of current decay – Eventually remove IL PH if MIITs and MTF allow » Eventually delay/remove also OL PH » Magnet self-protecting? 2-3 quenches + 1 verification quench (estimation) 13 time line Q t det PS Off, fire PH ~ 1 ms R dump dump delay

Summary of the proposals 1/2 1.Protection heater delay at 14 kA / 80% short sample limit -Measure delay in different coil segments -Low risk to magnet and MTF -4 quenches 2.Current decay after OL PH activation: Study MIITs decay vs. operating current – Provoked protection with only OL PH: Current decay due to R mag by PH, and potential quench back – Gradual increase in current (from 5 kA, in 1.5 kA steps, up to 15.5 kA) – Potentially high MIITs and cryostat pressure, at higher currents – Max 8 quenches + potential verification quenches 3.Quench propagation velocity using training quenches with delayed protection – Max allowed MIITs 16, cryostat pressure needs to be monitored – 3-4 quenches + verification quench 14

Summary of the proposals 2/2 4.High MIITs quenches, if safe MTF range established and magnet not degraded – Spontaneous quench with only OL PH, to see the additional MIITs – Spontaneous quenches with delayed R dump (Eventually delay/remove also IL and OL PH) – High risk to magnet – Possible degradation needs to be assessed with a verification quench after every increase in MIITs – High risk to MTF – Cyostat pressure needs to be monitored – 3-4 quenches + potential verification quenches 15

16 Thank you. Discussion is open.

Abbreviations PH = Protection Heater R dump = Dump resistor PS = Main Power Supply IL = Inner Layer OL = Outer Layer MIITs decay = MIITs for the current decay after trigger MIITs det = MIITs for the constant current before detection MIITs total = Total MIITs for a quench hotspot temperature I mag = Magnet current R mag = Magnet resistance E cryo = Energy dissipated in the cryostat L = Magnet inductance T hotspot = Adiabatic hotspot temperature 17