hq summary of quench protection studies
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HQ Summary of quench protection studies. 2 nd Joint HiLumi LHC – LARP Annual Meeting INFN Frascati – November 14 th to 16 th 2012 LBNL: Helene Felice – Tiina Salmi – Ray Hafalia – Maxim Martchevsky FNAL: Guram Chlachidze CERN: Ezio Todesco – Hugo Bajas. - PowerPoint PPT PresentationTRANSCRIPT
2nd Joint HiLumi LHC – LARP Annual MeetingINFN Frascati – November 14th to 16th 2012
LBNL: Helene Felice – Tiina Salmi – Ray Hafalia – Maxim MartchevskyFNAL: Guram Chlachidze
CERN: Ezio Todesco – Hugo Bajas
HQ Summary of quench protection studies
Work partially supported by the U. S. Department of Energy, under Contract No. DE-AC02-05CH11231
2nd Joint HiLumi LHC - LARP Annual meeting
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MIITs curve and Time margin
2012/11/14
0
5
10
15
20
25
30
0 50 100 150 200 250 300
MIIT
s (10
^6*A
^2*s
)
Hotspot temperature (K)
T0 = 2 K
12 T, RRR = 6012 T, RRR = 1000 T, RRR = 1000 T, RRR = 60
• Well-known that material properties play an important role
• Example of HQ MIITS computation: NIST+cryocomp /cryocomp /quenchproAt 2K and 12 T RRR 60 = 20.6 / 21.6 / 19.5At 2K and 0 T RRR 60 = 25.2/ 26.3 / 23.5
Average: 2 K, 12 T and RRR 60 = 20.6 +/- 1 MIITs
Figure of merit: the time margin (E. Todesco)
(MIITS budget – MIITS decay)/I2 = time to quench
HQ time margin of the order of 27 ms
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HQ protection scheme
2012/11/14
Protection Heaters (PH)
• PH strip on both layers• 2 strips per layer• 4 strips per coil• Strip R: ~ 4.5 W at 4.2 K
• Powering scheme• Typical: 4 circuits
• all B02, all A02, all B01, all A01• PH hipot failure to coil can lead to replacement by a resistance• In some cases, enough power supplies to power a few strips individually
• Coverage of about 60 % (including propagation between station)
Dump resistor• 30 to 40 mW
Layer 2
Layer 1
A01
A02
B01
B02
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HQProtection studies overview
2012/11/14
• Several tests• Magnets: HQ01a to e• Mirror: HQM01 and HQM04
• Protection Heaters (PH) delay studies• versus Heater peak power• versus magnet margin• versus Kapton thickness
• Quench back • MIITS limits
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Protection Heater (PH)Delay time versus peak power
2012/11/14
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40 60 80 100
Del
ay to
que
nch
onse
t (m
s)
Peak power (W/cm2)
Imag/ Iss tau = 24 mstau = 47 ms
29 %
29 %
42 %42 %
70 %
tau = 24 mstau = 47 ms
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0 20 40 60 80
Tim
e de
lay
(ms)
Peak power (W/cm2)
HQ01d
30 % Iss, circ#1 (IL circ)
30 % Iss, circ#5 (OL strip)
60% Iss, circ#5 (OL strip)
HQ01d
HQM01
Tau = 31 ms
• Some saturation of the delay at high peak power
• Tau => total energy impacts the delay time• Strongly at low fraction of Iss
• Marginally at higher fraction of Iss • Some studies on optimization of energy deposition
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0 20 40 60 80 100
Del
ay to
que
nch
onse
t (m
s)
Imag/iss (%)
HQM04, 4.6 K
HQM01, 4.6 K
HQ01e, 4.4 K
Impact of Kapton thickness on PH delay
2012/11/14
75 mm
25 mm
50 mm
Kapton thickness
H. Bajas et al., “Test Results of the LARP HQ01 Nb3Sn quadrupole magnet at 1.9 K”, presented at ASC2012T. Salmi et al.: “Quench protection challenges in long Nb3Sn accelerator magnets”, AIP Conf. Proc. 1434, 656 (2012)
HQ01e at CERN: Pw0 = 50 W/cm2, tau 40 ms: Iss = 17.3 kA @ 4.4 K; 19.1 kA @ 1.9 KHQM04 at FNAL: Pw0 = 45 W/cm2, tau 46 ms: Iss = 16.2 kA @ 4.6 K; 18.2 kA @ 2.2 KHQM01 at FNAL: Pw0 = 47 W/cm2, tau 46 ms: Iss = 17.0 kA @ 4.6 K
• Large increase of PH delay with Kapton thickness
• From 60 to 150 % from HQ01e to HQM04
• 75 mm: choice made for HQ02to ensure electrical integrity
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PH d
elay
tim
e (m
s)
Imag/Iss (%)
OL - 4.4 K
IL - 4.4 K
Il versus OL
HQ01e at CERN – coil 9 tested(25 mm Kapton)
40 -49 W/cm2
55 W/cm2
HQM04 at FNAL (75 mm kapton)
• In HQ01e: OL PH delay shorter than IL • In HQM04: IL PH delay shorter than OL• Possible differences between HQ01e and HQM04
=> Cooling of the bore?=> high compression due to mechanical preload in HQ01e: better thermal contact?
2012/11/14
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0.0 20.0 40.0 60.0 80.0 100.0
Del
ay to
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nch
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t (m
s)
Imag/iss (%)
VPH = 250 V
45 W/cm^2 -OL - 4.6 K
49 W/cm^2 - IL - 4.6 K
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Bath Temperature
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PH d
elay
time
(ms)
Imag/Iss (%)
OL - 1.9 K OL - 4.4 KIL - 1.9 K IL - 4.4 K
2012/11/14
HQ01e at CERN
• From HQ01e and HQM04: No effect of the bath temperature observed on the PH delay
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0.0 20.0 40.0 60.0 80.0 100.0D
elay
to q
uenc
h on
set (
ms)
Imag/iss (%)
VPH = 250 V - OL
HQM04: 45 W/cm^2 -4.6 K
HQM04: 45 W/cm^2 - 2.2 K
HQM01: 47 W/cm^2 - 4.6 K
HQ01e: 50 W/cm^2 - 4.4 K
HQ01e: 50 W/cm^2 - 1.9 K
HQ01e at CERN – HQM04 at FNAL
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Next steps on PH studies
2012/11/14
• Development of a 2D thermal model (Tiina Salmi, LBNL) • Simulation of heat transfer from PH to coil for design optimization
• Heater longitudinal layout• PH to coil insulation layout• PH powering
• Optimization of energy deposition: Square pulse, Truncated capacitance discharge
• Minimizing PH Temperature and Voltage• Comparison with experimental data showing good agreement
HQM04 simulationThermal system: half PH period
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• Magnet sitting at a constant current: from 5 to 13 kA – (NO quench)• Discharge in the 40 mW dump resistor without PH
• Does the magnet quench from eddy current generation in the cable (form of quench-back)?
• From the current decay:
• At 5 and 10 kA: no sign of quench• A 13 kA: signs of quench• At 15 kA: fraction of the magnet is quenching• Last 15 kA test with PH: no clear impact
HQ01e – Quench-Back
2012/11/14
𝑅𝑚𝑎𝑔 (𝑡 )=− 𝐿 𝑑𝑑𝑡 ln ( 𝐼 (𝑡 )
𝐼 0 )−𝑅𝑑𝑢𝑚𝑝
𝐼 (𝑡 )=𝐼 0𝑒−𝑅 𝑡𝐿
H. Bajas et al., “Test Results of the LARP HQ01 Nb3Sn quadrupole magnet at 1.9 K”, presented at ASC2012
HQ01e at CERN
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Edump= I(t) * Vdump(t) dt = 0.425 MJ10 ms
300 ms
2) Find total energy in the magnet:Magnet inductance is L=7.5 mH; Then, at I = 14819 A, Emag = LI2/2 = 0.823 MJ
4) Find magnet resistance: A = I2(t) dt = 7.13 106 =>
=> Rav = Ecryo/A = 0.055 W - average magnet resistance during extraction (10-300 ms)10 ms
300 ms
1) Find energy dissipated in the dump resistor
X
3) Find energy dissipated in the cryostat: Ecryo = 0.823-0.425 = 0.398 MJ
A36
Estimate of HQ01 resistance during extraction
2012/11/14
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HQ01e MIITS limit
2012/11/14
• Explored high MIITS by removing the dump resistor and inner layer PH (spontaneous quenches)
• HQ01e-3 at LBL will perform validation quench to check for degradation
H. Bajas et al., “Test Results of the LARP HQ01 Nb3Sn quadrupole magnet at 1.9 K”, presented at ASC2012
18.3 Miits
13.2 Miits 16.9 Miits
Time (s)
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PH and Trace revision
2012/11/14
• Avoid overlapping PH strip with metallic end parts: Rev C
• first implemented in HQ16
• Fit the “LHQ style” extension (Rev D): will be first implemented in HQ20
HQ02: - coil 15 OL: rev B - coil 17 OL: rev C -IL unchanged- coil 16 OL: rev C - coil 20 OL: rev D
HQ02 coils will have 75 microns kapton between PH strips and coil
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Summary
2012/11/14
• Protection heaters:• A wide mapping of the PH delay has been performed with the HQ01 series and
the mirrors• Good start to benchmark models
• From HQ01e: OL PH seem more efficient than IL PH• PH efficiency seems to be independent of temperature
• HQ01e test at CERN explored High MIITs regime• The dump resistor as well as the IL PH were deactivated
• HQ01e test at CERN exposed quench-back in the cable for current above 13 kA• HQ01e coils do not have a core
• Necessity to reproduce these tests with HQ02• cored cable• 75 microns Kapton between coil and PH strip