Protection study options for HQ01e-3

Tiina SalmiQXF meeting, 27 Nov 2012

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OutlineProposals:

1. Protection heater delay at 14 kA / 80% short sample limit2. Current decay after outer layer protection heater activation: Study

MIITs vs. operating current3. Normal zone propagation velocity4. Options for high MIITs quenches

Summary

Time for discussion

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1. PROTECTION HEATER DELAY

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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 Rdump 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

time lineFirePH

Q

PS Off, fire other PH,activate Rdump

Prot. delay 15 ms

tdet

PH delay

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

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ConceptReal quench protected with only OL PH Test: Provoked quench to estimate MIITsdecay

Difference to real quench:

MIITsdecay due to PH + quench back (No initial quench)

MIITstotal = MIITsdet + MIITsdecay’

MIITsdet: Imag ~constant, easy to estimate for various tdet

MIITsdecay’: Imag decay due to initial quench + PH +

quenchback

PS offFire OL PH

Test result: MIITsdecay vs. Imag

Conservative estimation

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Test procedure1. Deactivate IL PH and Rdump

2. Set OL PH voltage to 250 V (nominal setting)– Or highest possible based on hi-pot performance

3. Ramp to a constant Imag

– 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 MIITsdecay after the trigger

6. Monitor cryostat pressure and MIITsdecay (Thotspot)- Terminate the test if approaching safe limits (t.b.d.)- Ecryo = LImag

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7. Verification with a spontaneous quench using regular delayand ramp procedure if MIITS are above 14 (t.b.d.)

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Advantages• Controlled, gradual increase in Ecryo and MIITs

Reduced risk to test facility and magnet

• Conservative estimation of MIITs for real quench: Sum MIITsdecay and MIITs for an estimated detection time

• No initial quench in the magnet Lower total MIITs and Thotspot

• The first comparison with HQ02 can be done at low current and low MIITs

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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 Imag up to 15.5 kA, + verification quench(es)

• Data on cryostat pressure vs. Ecryo useful for the high MIITs quenches (discussed later)

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3. NORMAL ZONE PROPAGATION VELOCITY

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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

time lineQ

PS Off, fire other PH,activate Rdump

Prot. delay

tdet

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4. MORE OPTIONS FOR HIGH MIITS QUENCHES

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Options for high MIITs quenchesIF safe MTF range established and magnet not degraded:1) Spontaneous quench with only OL PH and Rdump, to see the additional MIITs

(expected +1-1.5 Miits) (1 quench)

2) Spontaneous quenches with delayed Rdump

• Info about cryostat pressure vs. Ecryo useful for defining the delay

• Ultimate goal to delay Rdump 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)

time lineQ tdet

PS Off, fire PH ~ 1 ms

Rdump

dump delay

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Summary of the proposals 1/21. 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 MIITsdecay vs. operating current

– Provoked protection with only OL PH: Current decay due to Rmag 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

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Summary of the proposals 2/24. 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 Rdump (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

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Thank you. Discussion is open.

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AbbreviationsPH = Protection HeaterRdump = Dump resistor

PS = Main Power SupplyIL = Inner LayerOL = Outer LayerMIITsdecay = MIITs for the current decay after trigger

MIITsdet = MIITs for the constant current before detection

MIITstotal = Total MIITs for a quench hotspot temperature

Imag = Magnet current

Rmag = Magnet resistance

Ecryo = Energy dissipated in the cryostat

L = Magnet inductanceThotspot = Adiabatic hotspot temperature