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Andrzej Siemko 26 February 2009 MMI^2T limits for magnets, what are they and how where they developed. I^2T limits for magnets, what are they and how where they developed. A. Siemko
Andrzej Siemko26 February
2009
MMI^2T limits for magnets, what are they and how where they developed.
I^2T limits for magnets, what are they and how where they developed.
A. Siemko
Andrzej Siemko26 February
2009
Quench Heater Position Variants the positions of quench
heaters were in the outer layer of the coil either at
outer radius - so-called outer radius quench heaters (ORQH) or
between the inner and the outer layer - inter radius quench heaters (IRQH)
High field position (HF)
Low field position (LF)
Block 2
spot heater position in the pole turn
outer radius quench heater(ORQH)
inter radius quench heater (IRQH)
two insulation foils 75 and 200 mm thick placed between the heater strip and the magnet coil were tested.
Andrzej Siemko26 February
2009
Temperature profiles
60
280
7080
95105
115
125
135
Natural quench
I=13967A; T=1.88 KTht ~ 277 K
DThb ~ 145 K
250
65
75
85
95
105
125
140
Quench provoked by
spot heaterI=12850A ; T=1.90 K Tht~249 K
DThb~110 K
Quench origin
Quench origin (Spot heater)
Hottest block
Hottest turn
the temperature of the hottest turn and the temperature difference between the hottest turn and the average temperature of the related block DThb were considered.
Andrzej Siemko26 February
2009
Principles of the method
Magnet equivalent electrical circuit during a quench
At the beginning of the quench, a pure inductive voltage is measured by most of the voltage taps
For the cable length between two voltage taps
Joule heat released during the quenches
LE (I) R(t)
)0( ILV
VL Emagnet
inductive
tapsinductive
n
22002
1)0(
)()( tItILtItILLL
tdtItVtQ EEE
nt
to
Andrzej Siemko26 February
2009
Effect of the quench heater position Quenches were
provoked by firing a spot heater in the outer layer.
At low currents the protection by IRQH and ORQH was equivalent.
At I = 12850A reduction of 35 K and 20 K was measured for Tht and DThb when the magnet was protected by the IRQH and ORQH respectively.
Effect of the quench heater position on Tht.
0
50
100
150
200
250
300
4000 5500 7000 8500 10000 11500 13000
Current[A]
Tht
[ K] ORQH IRQH
Effect of the quench heater position on DThb.
0
25
50
75
100
125
4000 5500 7000 8500 10000 11500 13000
Current[A]
DT
hb [
K]
ORQH IRQH
Andrzej Siemko26 February
2009
Protection by different sets of IRQH
Protection by all IRQH heaters (HF+LF) or by HF only is equivalent.
Protection by only half HF IRQH assured temperatures within the design specification limit.
For adequate redundancy protection by one full set of HF IRQH is fully sufficient.
Temperature of hottest turn
50
100
150
200
250
300
5000 6000 7000 8000 9000 10000 11000
Current (A)
Tht
[K]
HF+LF HFLF one HF
DThb vs several types of IRQH protection
0
20
40
60
80
100
120
140
5000 6000 7000 8000 9000 10000 11000
T [K
]
HF+LF HFLF one HF
Andrzej Siemko26 February
2009
Effect of the insulation thickness As expected Tht and
DThb increase with the insulation thickness.
At high currents the increase was important and equal to about 80 K for Tht and 54 K for DThb .
At the nominal current (11850 A) an insulation thickness of 200 mm between the heater and the coils results in peak temperatures and gradients exceeding “good engineering” practice.
Influence of the thickness on T ht.
0
50
100
150
200
250
300
4000 6000 8000 10000 12000 14000
Current [A]
Tht
[ K
] t=0.075 mmt=0.2 mm
Influence of the thickness on DThb.
0
20
40
60
80
100
120
140
160
180
200
4000 5500 7000 8500 10000 11500 13000
Current [A]
DT
hb [
K]
t=0.075 mmt=0.2 mm
Andrzej Siemko26 February
2009
De-training and Temperature Quench field drops
down to two different levels Dinter and Douter , depending on heaters.
Protection by ORQH caused a decrease of quench level to 8.4 T in average (Douter).
Protection by IRQH limited the drop to an average value of 8.7T (Dinter).
Drop to a lower level appeared after an increase of Tht and DThb of 35 K and 26 K respectively.
506070
8090
100110120
130140150
25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45
Quench Number
DT
hb
[K]
77.27.4
7.67.888.28.4
8.68.89
B[T
] at q
uenc
hIRQH ORQH B[T] at quench
D inter
D outer
140160180200220240260280300320340360
25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45
Quench Number
Tht
[K]
77.27.47.67.88
8.28.48.68.89
B[T
] at q
uenc
h
IRQH ORQH B[T] at quench
D inter
D outer
Andrzej Siemko26 February
2009
Influence on the quench training
de-training effect, observed in LHC dipole model magnets is of a thermo-mechanical origin.
it is induced by the coexistence of a mechanical weak region and a thermal contraction which is due to the temperature rise when all the stored energy is dissipated in the magnet.
Training Quenches at 1.8K
7.00
7.50
8.00
8.50
9.00
9.50
10.00
10.50
0 5 10 15 20 25 30 35 40 45 50Quench Number
Mag
netic
Fie
ld a
t Que
nch
B [T
esla
]
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
80.0
90.0
100.0
Dep
osite
d E
nerg
y [%
]
Training S.S.Limit at 1.8K S.S.Limit at 4.35K Bnom = 8.3 Tesla Deposited Energy [%]
Dinter
Douter
IRQH protection IRQH protection
ORQH protection
Andrzej Siemko26 February
2009
Correlation between Tht and de-training
magnets with similar mechanical features exhibit a strong correlation between the de-training effect and the hot spot temperature
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
250 260 270 280 290 300 310 320T[K] (average)
Ave
rage
de-
trai
ning
[T]
S15.V2
S15.V4
S15.V5
S15.V5
S15.V1
S17.V1
S18.V1
S23.V1
Hottest turn temperature
Andrzej Siemko26 February
2009
Correlation between DTht and de-training
magnets with similar mechanical features exhibit a strong correlation between the de-training effect and the temperature gradients
DT =Thot-TB2for quenches in the outer layer
without extraction
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
100 120 140 160 180 200DT[K] (average)
Ave
rage
de-
trai
ning
[T]
S15.V2
S15.V4
S15.V5
S15.V5
S15.V1S17.V1
S18.V1
S23.V1
Andrzej Siemko26 February
2009
0.00
50.00
100.00
150.00
200.00
250.00
300.00
350.00
400.00
0 5 10 15 20 25 30 35
MIITs vs Temperature
T(K), B=0 Tesla T(K), B=2 Tesla
T(K), B=4 Tesla T(K), B=6 Tesla
T(K), B=8 Tesla T(K), B=10 Tesla
RRR 150
Andrzej Siemko26 February
2009
Automatic quench analysis and MIITs monitoring
Andrzej Siemko26 February
2009
MIITs monitoring
Andrzej Siemko26 February
2009
Reference
V.Maroussov and A.Siemko
" A Method to Evaluate the Temperature Profile in a Superconducting Magnet During a Quench”
IEEE Trans. Applied. Superconductivity 9, pp. 1153-1156 (1998).
