Transients scenarios for the cryogenic operation of superconducting magnets of LHC experiments
description
Transcript of Transients scenarios for the cryogenic operation of superconducting magnets of LHC experiments
R. Pengo June 1st, 2007
Transients scenarios for the Transients scenarios for the cryogenic operation of cryogenic operation of
superconducting magnets of LHC superconducting magnets of LHC experiments experiments
Experience at CERNExperience at CERNR.Pengo R.Pengo
CERN, AT-ECRCERN, AT-ECR
R. Pengo June 1st, 2007
Content of the presentationContent of the presentation
Details for CMS and ATLAS of:• cooling down process• static heat load• dynamic heat load• fast discharge of the magnets• recovery after a fast dump
R. Pengo June 1st, 2007
Structure of the s/c magnetsStructure of the s/c magnets
CMS is composed of• a s/c solenoid, divided in 5 sectors
ATLAS is composed of• a s/c Central Solenoid (CS)• a Barrel Toroid (BT), formed by 8 s/c
race-track coils• 2 End Cap Toroids (ECT), each formed
by 8 s/c squared coils
R. Pengo June 1st, 2007
Cooling methods for CMS & ATLASCooling methods for CMS & ATLAS
CMS • The solenoid is indirectly cooled by LHe,
driven by thermosyphon movement (i.e. gravity driven)
ATLAS• The CS is indirectly cooled either by the
JT circuit of the Main Refrigerator (MR) or by thermosyphon movement
• Both BT and ECT’s coils are indirectly cooled by forced LHe flow produced by a 1.2 kg/s centrifugal pump
R. Pengo June 1st, 2007
Cold Mass InventoryCold Mass Inventory
CMS total cold mass is 220 Tons (cylinder 6.6 m x 12.5 m)
ATLAS total cold mass is ca. 700 Tons• CS ca. 6 Tons (cylinder 2.5m x 5.3m)• BT (340 +20) Tons (8: 25 m x 5 m)• ECT’s (2 x 160) Tons (8: 5m x 5m)
R. Pengo June 1st, 2007
Where we are with the commissioningWhere we are with the commissioning
Actual status:• CMS fully tested on the surface• ATLAS
– CS fully tested (surface and cavern)– BT fully tested (surface and cavern)– ECT-A tested at LN2 temperature on surface– ECT-C under test on the surface
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Cooling down of the MagnetsCooling down of the Magnets
R. Pengo June 1st, 2007
Cooling down of the MagnetsCooling down of the Magnets
CMS
Cooling CMS
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2-Feb-06 7-Feb-06 12-Feb-06 17-Feb-06 22-Feb-06 27-Feb-06
Tm
in T
ma
x [
K]
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De
lta
T [
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QUR1H_C_TTMAGMIN.POSST QUU1H_C_TTMAGMAX.POSST Delta T
10 days
DT< 22K
1.2 kW @ 4.5 K Refrigerator used
Cooling Time ca. 22 days
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Cooling down of the MagnetsCooling down of the Magnets
ATLAS :CS• Shield Refrigerator (SR) & Main Refrigerator (MR) used
Central Solenoid Cooldown
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350
16-May-06 18-May-06 20-May-06 22-May-06 24-May-06
Tem
per
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Control Dewar Bottom Solenoid coil
4 days
SR: Cold Mass and shield in
series
-SR for shield
- MR for CM75 K
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Cooling down of the MagnetsCooling down of the Magnets
ATLAS :BT• Shield Refrigerator (SR) & Main Refrigerator (MR) used
BT cooling curve
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7/2/0612:00 AM
7/12/0612:00 AM
7/22/0612:00 AM
8/1/0612:00 AM
8/11/0612:00 AM
8/21/0612:00 AM
8/31/0612:00 AM
9/10/0612:00 AM
9/20/0612:00 AM
9/30/0612:00 AM
Tem
per
atu
re [
K]
SR: cold mass and shield in
parallel
-SR for the shields
-MR for Cold mass
Start of the 1.2 kg/s LHe pump
10 days
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Cooling down of the MagnetsCooling down of the Magnets
ATLAS :BT• Shield Refrigerator (SR) & Main Refrigerator (MR) used
BT cooling curve
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04-Jul-06 24-Jul-06 13-Aug-06 02-Sep-06 22-Sep-06
Te
mp
era
ture
[K
]
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DT
[K
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DT< 40 K
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Cooling down of the MagnetsCooling down of the Magnets
ATLAS : ECT-A
Cooling of ECT-A
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2/16/07 0:00 2/26/07 0:00 3/8/07 0:00 3/18/07 0:00 3/28/07 0:00 4/7/07 0:00
Tem
per
atu
re [
K]
Calculation Coil Shield
Only LN2 precooler used
10 Days
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Cooling down of the MagnetsCooling down of the Magnets
ATLAS : ECT-C (in progress)
Cooling of ECT-C
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May 15, 2007 May 20, 2007 May 25, 2007 May 30, 2007 June 4, 2007 June 9, 2007 June 14, 2007
Tem
per
atu
re [
K]
Shield out Aveage Shield Average Total
10 days
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STATIC HEAT LOADSTATIC HEAT LOAD
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STATIC HEAT LOADSTATIC HEAT LOAD
CMS• Measured by LHe level decreasing in
Phase Separator• Natural Temperature increasing on the
cold mass
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STATIC HEAT LOADSTATIC HEAT LOAD
CMS: Measured by LHe level decreasing in Phase Separator (178 W)
Débit AdI 2 x 0,4 g/sDniv(A-B) = 6,75% en 10’=Soit 277 l/h
Bilan = 254 l/h = 178 W
A
B
From Ph. Bredy, CEA
Saclay
LHe level in Phase
Separator
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STATIC HEAT LOADSTATIC HEAT LOAD
CMS: Natural Temperature increasing of the cold mass (174 W)
2 K/ 21 ½ min = 154 W on Cold mass alone
(SdP heat loads to be added 20 W)
Total = 174 W
Cold mass bilan :NbTi 4.9 tCu 8.6 tAl pur 73.9 tAl renf 6082 90.4 tG10 9.9 tAl cyl 5083 34.8 t
From Ph. Bredy, CEA
Saclay
10 K
5 K
CDS synchronization !
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STATIC HEAT LOADSTATIC HEAT LOAD
ATLAS: CS
Measurement of total loss was done during thermosyphon operation mode with disconnected refrigerator and looking at the level/time change in the control dewar
Results: - 17 Watts for the solenoid and
the chimney;- below 10 Watts for the dewar.
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STATIC HEAT LOADSTATIC HEAT LOAD
ATLAS: Barrel Toroid CM• For each of the 8 race-track coils the
heat load has been measured – in the surface test hall (Mass-flow meter)– in the UX15 cavern after assembling into BT
(natural temperature increase)
• The total heat load of the BT has been also measured in the cavern
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STATIC HEAT LOADSTATIC HEAT LOAD
ATLAS: Barrel ToroidNatural Warm Up
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28-Nov 8-Dec 18-Dec 28-Dec 7-Jan
Te
mp
era
ture
[K
]
S1_IN
S1_OUT
S2_IN
S2_OUT
S3_IN
S3_OUT
S4_IN
S4_OUT
S5_IN
S5_OUT
S6_IN
S6_OUT
S7_IN
S7_OUT
S8_IN
S8_OUT
Natural Warm Up Jan 9th, 2007
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29-Nov-06 09-Dec-06 19-Dec-06 29-Dec-06 08-Jan-07
Te
mp
era
ture
[K
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Tin-Tout on the pipes
Tmax, Tmin on coils
Pt1000
Carbon resistors
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STATIC HEAT LOADSTATIC HEAT LOAD
ATLAS: Barrel ToroidAverage BT heat load in Cryoring (14 Dec 2006)
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1 2 3 4 5 6 7 8
BT coils
WA
TT
Values measured in test station
TOTAL MEASURED IN TEST STATION 571 W TOTAL IN UX15 IS 586 W
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STATIC HEAT LOADSTATIC HEAT LOAD
ATLAS: Barrel Toroid
LHe Pumps: 660 W
PCS+TL11+Cryoring: 250 W
BT: 620 W (or 1530-660-250)W
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STATIC HEAT LOADSTATIC HEAT LOAD
ATLAS: Barrel Toroid Shields• For each of the 8 cryostats
– in the surface test hall (Mass-flow meter)– Average 800 W
– the total heat load of the BT shield has been also measured in the cavern (Mass-flow meter)
– Total 6000 W
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DYNAMIC HEAT LOADDYNAMIC HEAT LOAD
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DYNAMIC HEAT LOADDYNAMIC HEAT LOAD
Flux is proportional to Current:• Φ = L x I , V = -dΦ /dt = - L x dI/dt
– Voltage is induced when changing current– And energy is dissipated by the induced current on the
casing (~ autotransformer)
Al Coil casing
2 x 60 = 120 turns
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DYNAMIC HEAT LOADDYNAMIC HEAT LOAD
ATLAS:
gcaRdt
dI
n
M
WPsin
2
*][
Calculated: No Fit!
Dynamic heat load
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0 1 2 3 4 5 6 7 8 9
dI/dt [A/s]
Po
we
r [W
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P,th (12.63 micro ohm) P,th (13.33 micro ohm) B2 B3 B4 B5 B6 B8
Slow dump equivalent
One coil: L = 0.5667 H, Total BT: L= 5.5 H => expected value 350 W
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DYNAMIC HEAT LOADDYNAMIC HEAT LOAD
ATLAS: BTSlow dump on Nov. 18th, 2006
Return Buckets Levels
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Time [hh:mm]
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E L
ev
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uc
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rre
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[A]
Level of LHe is reduced due to the
higher vaporization during slow discharge
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DYNAMIC HEAT LOADDYNAMIC HEAT LOAD
ATLAS: BTSlow Dump 20.5 kA on Nov. 18, 2006
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ss
flo
w [
g/s
]
LHe vapor mass flow on the
phase separator is increased due
to the higher heat load
~380 W
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DYNAMIC HEAT LOADDYNAMIC HEAT LOAD
ATLAS: CS• Eddy current loss are around 25 Watts.
Measurement principle: compare consumption during ramp up at 6 A/s with previously measured
static losses by looking at the heater power in the control dewar which is reduced by 25 watts.
Furthermore “gas counting”.
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DYNAMIC HEAT LOADDYNAMIC HEAT LOAD
CMS:
CMS slow dump (~4 hours)
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Cu
rre
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[A]
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Le
ve
l Bu
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ew
ar
Current Level Buffer Dewar
Thermosyphon Mass flow is
naturally increased due to the higher heat
load
Current decreasing during slow discharge
Temperature increase ~ 0.28 K
4.5 K
7.5 K
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DYNAMIC HEAT LOADDYNAMIC HEAT LOAD
CMSSlow discharge
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20/10/200617:02:24
20/10/200618:14:24
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Cu
rre
nt
[A]
4.5
5
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Te
mp
era
ture
[K
]
Fast discharge at 5000 A
Slow discharge
Temperature increase ~ 0.28 K
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FAST CURRENT DISCHARGEFAST CURRENT DISCHARGE
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FAST CURRENT DISCHARGEFAST CURRENT DISCHARGE
CMS: stored EM energy is 2.5 GJ (about 220 Tons)
Fast dump on August 22nd, 2006
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Cu
rre
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[A]
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Current Pressure Temperature
Temperature rise up to 70 K
Pressure rise in PS
1 hour
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FAST CURRENT DISCHARGEFAST CURRENT DISCHARGE
ATLAS-CS: Stored EM energy is 40 MJ
Solenoid Fast Dump
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10:27:33 10:28:16 10:29:00 10:29:43 10:30:26
Te
mp
era
ture
[K
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Cu
rre
nt
[A]
Chimney Coil Tmax Coil Tmin Current
1 min
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FAST CURRENT DISCHARGEFAST CURRENT DISCHARGE
ATLAS-CS: pressure rise
From F.Haug
Coil return: max 7.11 bar
Coil inlet: max 4.32 bar
Current: 7800 A
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FAST CURRENT DISCHARGEFAST CURRENT DISCHARGE
ATLAS-BT: Stored EM vs. EnthalpyFast Dump Temperature
0102030405060708090
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Energy (MJoule)
Tem
per
atu
re [
K]
0200040006000800010000120001400016000180002000022000
Cu
rren
t [A
]
EM Energy at Current [A]
BT Enthalpy
57 K
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FAST CURRENT DISCHARGEFAST CURRENT DISCHARGE
ATLAS-BT:Fast Dump 20.5 kA
9th Nov., 2006
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1012
14
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11:24 PM 11:31 PM 11:38 PM 11:45 PM 11:52 PM 12:00 AM
Pre
ss
ure
[b
ar]
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5000
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25000
Cu
rre
nt
[A]
Pressure PS Pressure return Current
Pressure in Phase Separator
Pressure on the return to the Shield
Refrigerator
15 min
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FAST CURRENT DISCHARGEFAST CURRENT DISCHARGE
ATLAS-BT:Fast Dump Pressures
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10/25/2006 10/30/2006 11/4/2006 11/9/2006 11/14/2006
Pre
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[B
ar]
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Cu
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[A]
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FAST CURRENT DISCHARGEFAST CURRENT DISCHARGE
BT: Recovery after a full current fast dump
Recovery from 20.5 kA fast dump
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11/12/0612:00
Co
ils T
em
pe
ratu
re [
K]
One day58 K
R. Pengo June 1st, 2007
SummarySummary
Data on transient modes of operation have been Data on transient modes of operation have been displayed and discussed, namely:displayed and discussed, namely:
-- cooling down process cooling down process- static heat load- static heat load- dynamic heat load- dynamic heat load- fast discharge of the magnets- fast discharge of the magnets- recovery after a fast dump.- recovery after a fast dump.
The results are in good agreement with the design The results are in good agreement with the design
R. Pengo June 1st, 2007
I would like to thank for their collaboration all I would like to thank for their collaboration all colleagues from CERN and from the external colleagues from CERN and from the external
Institutes involved (CEA-SACLAY,INFN,KEK,RAL)Institutes involved (CEA-SACLAY,INFN,KEK,RAL)