Technology of superfluid helium
Philippe Lebrun & Laurent Tavian
CERN, Geneva, Switzerland
CERN Accelerator School «Superconductivity for Accelerators»
Ettore Majorana Foundation and Centre for Scientific Culture
Erice, Italy, 24 April – 4 May 2013
Contents
•
•
•
•
•
•
Ph. Lebrun
Introduction to superfluid helium
Superfluid helium as a technical coolant
Practical cooling schemes
Refrigeration below 2 K
Specific technology for He II systems
Applications
CAS Erice, 24 April-4 May 2013
2
Contents
•
•
•
•
•
•
Ph. Lebrun
Introduction to superfluid helium
Superfluid helium as a technical coolant
Practical cooling schemes
Refrigeration below 2 K
Specific technology for He II systems
Applications
CAS Erice, 24 April-4 May 2013
3
First liquefaction of helium (1908)
Leiden « cascade » to
produce liquid hydrogen
Ph. Lebrun
Helium liquefaction stage
precooled by liquid hydrogen
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4
Ph. Lebrun
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5
Unsuccessful attempt to solidify helium
Ph. Lebrun
CAS Erice, 24 April-4 May 2013
6
Hint of a quantum effect…?
Ph. Lebrun
CAS Erice, 24 April-4 May 2013
7
Zero-point (quantum)
energy prevents helium
from solidifying
F. London
Ph. Lebrun
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8
Discovery of He II phase transition (1928)
Helium phase diagram (1933)
W.H. Keesom
Ph. Lebrun
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9
Phase diagram of helium
10000
SOLID
l line
Pressure [kPa]
1000
He II
SUPERCRITICAL
He I
CRITICAL
POINT
100
PRESSURIZED He II
(Subcooled liquid)
SATURATED He I
10
VAPOUR
SATURATED He II
1
0
1
2
3
4
5
6
Temperature [K]
Ph. Lebrun
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10
Discovery of superfluidity in He II (1938)
J.F. Allen & A.D. Misener (Cambridge)
P.L. Kapitsa (Moscow)
Vaporization of liquid helium under applied heat load
He I (T=2.4 K)
Ph. Lebrun
He II (T=2.1 K)
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11
Theoretical approaches to superfluid helium
Fritz London
Bose-Einstein condensation
Ph. Lebrun
Laszlo Tisza
Two-fluid model
CAS Erice, 24 April-4 May 2013
Lev Davidovich Landau
Quasi-particle description
12
Bose-Einstein condensation in gas of particles
Ph. Lebrun
CAS Erice, 24 April-4 May 2013
13
Two-fluid model of He II
Phenomenological model
Two interpenetrating fluids
= s + n
Normal & superfluid fractions varying with T
 v = s vs + n vn
 s = n sn since ss = 0
All entropy carried by normal component
Physical basis of the two-fluid model
• Collective excitations constitute the normal
component (Landau)
• B-E condensate in liquid (Penrose & Onsager)
Ph. Lebrun
CAS Erice, 24 April-4 May 2013
14
He II behaviour explained by two-fluid model
• Frictionless flow through small channels
– Film flow
– Andronikashvilii experiment
• Thermal transport by counterflow
– Laminar
– Turbulent
• Thermomechanical effect
• Second sound
Ph. Lebrun
CAS Erice, 24 April-4 May 2013
15
Contents
•
•
•
•
•
•
Ph. Lebrun
Introduction to superfluid helium
Superfluid helium as a technical coolant
Practical cooling schemes
Refrigeration below 2 K
Specific technology for He II systems
Applications
CAS Erice, 24 April-4 May 2013
16
Benefits of He II cooling
• Lower the operating temperature
– Achieve higher magnetic field through increase of critical current
density of superconductor
– Minimize overall energy dissipation in RF cavities
• Enhance heat transfer
– At solid-liquid interface  conductor cooling
– In the bulk liquid
 device/system cooling scheme
 calorimetry in isothermal bath
Ph. Lebrun
CAS Erice, 24 April-4 May 2013
17
Critical current density of superconductors
for high-field magnets
Nb-Ti @ 4.5 K
3000
Nb-Ti @ 2 K
Jc [A/mm2]
2500
Nb3Sn @ 4.5 K
2000
1500
1000
500
0
6
Ph. Lebrun
8
10
B [T]
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12
14
18
Optimization of operating temperature
for superconducting RF cavities
• BCS theory
• For practical materials
• Refrigeration (Carnot)
RBCS = (A w2 /T) exp (-B Tc/T)
RS = RBCS + R0
Pa = P (Ta/T - 1)
 depending upon w and R0, optimum operating temperature for
superconducting cavities
500
Niobium
Cavity loss
Carnot efficiency
Arbitrary Units
Cooling power
0
1
Ph. Lebrun
CAS Erice, 24 April-4 May 2013
1.5
2
2.5
T [K]
19
Enhancement of heat transfer
• Low viscosity  permeation
• Very high specific heat  stabilization
– 105 times that of the conductor per unit mass
– 2 x 103 times that of the conductor per unit volume
• Very high thermal conductivity  heat transport
– 103 times that of cryogenic-grade OFHC copper
– peaking at 1.9 K
Full benefit of these transport properties can only be reaped by
appropriate design providing good wetting of the
superconductors and percolation paths in the insulation, often in
conflict with other technical requirements
Ph. Lebrun
CAS Erice, 24 April-4 May 2013
20
Specific heat of liquid helium and copper
100
Specific heat [J/g.K]
10
1
0,1
LHe
Cu
0,01
0,001
0,0001
0,00001
0
Ph. Lebrun
1
2
3
Temperature [K]
CAS Erice, 24 April-4 May 2013
4
5
21
Equivalent thermal conductivity of He II p
2000
Helium II
Y(T) ± 5%
KT,q   q 2.4  YT
1500
dT q 3.4

dX Y(T)
1000
q in W / cm2
T in K
X in cm
500
Tl
Copper OFHC
0
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2
2.1
2.2
T [K]
Ph. Lebrun
CAS Erice, 24 April-4 May 2013
22
Solid-liquid interface: Kapitza conductance
100
Heat exchange surface
t
n limi
o
i
t
a
i
d
on ra
n
o
)
h
P
faces
r
u
S
an
s (Cle
t
n
e
rim
Expe
Solid
He II
T(x)
DTs
2
hK [kW/m .K]
10
q
1
s)
rface
u
S
y
rt
ts (Di
n
e
m
i
r
Expe
0,1
Experimental data for Copper
(S. Van Sciver, "Helium
Cryogenics")
heory
T
v
o
tnik
Khala
hK ~ T 3
0,01
1,3
1,5
1,7
1,9
2,1
Valid for small heat flux
(when DT<<T)
T [K]
Ph. Lebrun
CAS Erice, 24 April-4 May 2013
23
Application of high thermal conductivity
Calorimetry in isothermal He II bath
•
For slow thermal transients, the He II bath
is quasi-isothermal: a single temperature
measurement allows to estimate heat
deposition/generation Q'
- at constant P
- at constant V
•
Ph. Lebrun
Q'
Q' = Mbath dH/dt|1
Q' = Mbath dE/dt|1
Mbath can be estimated by in situ
calibration, using applied heating power W'
- at constant P
- at constant V
T
W'
W' = Mbath dH/dt|2
W' = Mbath dE/dt|2
CAS Erice, 24 April-4 May 2013
24
Calorimetry of magnet quench in He II bath
Time evolution of bath temperature
Correlation with electrical measurements
Ph. Lebrun
CAS Erice, 24 April-4 May 2013
25
Precision thermometry allows calorimetric detection
of faulty joints in LHC at safe powering level
1.92
6000
5000
LBARA_16R1_TT821.POSST
LBARA_17R1_TT821.POSST
1.91
LBARA_19R1_TT821.POSST
LBARB_16R1_TT821.POSST
LBARB_18R1_TT821.POSST
1.9
3000
2000
1.89
Current [A]
Temperature evolution [K]
LBARA_18R1_TT821.POSST
4000
LBBRA_16R1_TT821.POSST
LBBRA_17R1_TT821.POSST
LBBRA_18R1_TT821.POSST
LBBRA_19R1_TT821.POSST
LBBRD_17R1_TT821.POSST
1000
LBBRD_19R1_TT821.POSST
LQATH_16R1_TT821.POSST
LQATH_18R1_TT821.POSST
1.88
0
LQATK_17R1_TT821.POSST
LQATO_15R1_TT821.POSST
RPTE.UA23.RB.A12:I_MEAS
1.87
-1000
14:00
Current
15:00
16:00
17:00
Total (measured)
18:00
19:00
20:00
Nominal
Splices*
Add. local
dissipation
Uncertainty
[A]
[mW/m]
[W]
[W]
[W]
[W]
3000
4.4
1.0
0.4
0.6
0.6
5000
14.9
3.2
1.1
2.1
0.6
7000
32.2
6.9
2.1
4.8
0.6
 Local resistance: ~90 nW, confirmed by electrical measurement
Ph. Lebrun
CAS Erice, 24 April-4 May 2013
26
Pressurized vs saturated He II
10000
SOLID
Pressure [kPa]
1000
SUPERCRITICAL
He II
He I
CRITICAL
POINT
100
PRESSURIZED He II
(Subcooled liquid)
SATURATED He I
10
VAPOUR
SATURATED He II
1
0
1
2
3
4
5
6
Temperature [K]
Ph. Lebrun
CAS Erice, 24 April-4 May 2013
27
Advantages & drawbacks of He II p
• Advantages
– limits the risk of air inleaks and contamination in large and
complex cryogenic systems
– for electrical devices, limits the risk of electrical breakdown
at fairly low voltage due to the bad dielectric characteristics
of helium vapour (Paschen curve)
– better stabilizer for heat buffering
• Drawbacks
– one more level of heat transfer
– additional process equipment (pressurized-to-saturated
helium II heat exchanger)
Ph. Lebrun
CAS Erice, 24 April-4 May 2013
28
Paschen curve for gaseous He at 20 °C
Potential difference, Vr, [kV]
100
Electrical breakdown area
10
1
0.1
1
10
100
1000
Pressure.distance [Pa.m]
10000
100000
e.g., 1.6 kPa pressure and 6 mm gap
Ph. Lebrun
CAS Erice, 24 April-4 May 2013
29
Thermal stabilisation in He II s
He II Sat
(1.8 K)
Dh= 0.1 m
At the device surface:
(adding hydrostatic head)
P*= P + .g.Dh = 17.8 mbar
for which corresponds a temperature
of saturation of T*= 1.82 K
30
Cp [J/g.K]
At the liquid surface:
P= Psat = 16.4 mbar
28
26
24
8 Saturated
22
6 9 mJ/cm3
0
1
4
2
0
0
1
Ph. Lebrun
2
3
4
2
1.8 Tl
3
4
T [K]
The corresponding DH is 9 mJ/cm3
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30
Thermal stabilisation in He II p
10000
30
Pressure [kPa]
1000
Cp [J/g.K]
SOLID
SUPERCRITICAL
He II
He I
CRITICAL
POINT
100
PRESSURIZED He II
(Subcooled liquid)
SATURATED He I
10
VAPOUR
SATURATED He II
1
0
1
2
3
4
5
28
26
24
8 Pressurized
22
6 280 mJ/cm3
0
1
2
4
2
0
0
1
2
1.8 Tl
3
3
4
4
T [K]
6
Temperature [K]
The corresponding DH is 280 mJ/cm3
(30 times higher than in He II s)
Ph. Lebrun
CAS Erice, 24 April-4 May 2013
31
Contents
•
•
•
•
•
•
Ph. Lebrun
Introduction to superfluid helium
Superfluid helium as a technical coolant
Practical cooling schemes
Refrigeration below 2 K
Specific technology for He II systems
Applications
CAS Erice, 24 April-4 May 2013
32
Working with superfluid helium
at atmospheric pressure
P atm
P atm
4.2 K
4.2 K
He I
He I
Tle
Tl
Tl
Refri
He II
He II
Tle
T<<Tl
« Roubeau bath »: He II conduction
prevents from lowering the bath
temperature well below Tl
Ph. Lebrun
Refri
« Claudet bath »: restriction in
cryostat allows subooling He II bath
to temperatures well below Tl
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33
A practical Claudet bath
Ph. Lebrun
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34
Conduction cooling in static He II p
A
Cross-section: A
Length: L
Power: Q
Q
Heat Flux: q 
A
.
Q
L
T1
• Gorter-Mellink law:
T2
q m  L  XT2   XT1 
X(T)
• Experimental work of Bon Mardion, Claudet & Seyfert:
• m ≈ 3.4
• tabulation of X(T)
600
Note 1: this is a non-linear formula
for conduction  use proper units!
Note 2: m = 1 for classical solid
conduction (Fourier’s law)
Ph. Lebrun
400
200
Tl
0
CAS Erice, 24 April-4 May 2013
1.3 1.5 1.7 1.9 2.1
T [K]
35
Thermal conduction integral function of He II p
600
X(Tc)  X(Tw)  q 3.4  L
q in W.cm2
500
X(T) ± 3%
L in cm
T in K
400
Tw
300
200
.
q
Tc
He II
L
100
Tl
0
1.3 1.4 1.5 1.6 1.7 1.8 1.9
2
2.1 2.2
T [K]
Ph. Lebrun
CAS Erice, 24 April-4 May 2013
36
Conduction cooling: a numerical example
A
A = 1 cm2
L = 1 m = 100 cm (Units!)
T1 = 1.9 K
 X(T1) = 200
T2 = 1.8 K
 X(T2) = 360
.
Q
L
T1
T2
.
Then:
q3.4.L = 360 - 200
. 3.4
 q
.
= 1.6  q = 1.15 W/cm2
Comparison with "good solid conductor", e.g. Copper
q  k 
ΔT
with k = thermal conductivity at 1.8 K
L
Cu type
k [W/m.K]
DT [K]
L [m]
q [mW/cm2]
OFHC
120
0.1
1
1.2
DHP
3
0.1
1
0.03
He II conducts heat 1000 times better than OFHC Cu
Ph. Lebrun
CAS Erice, 24 April-4 May 2013
37
Steady-state conduction duct in He II
100
90
From 1.80 K to 1.90 K
DN
100
80
Cold source
He II Sat.
(1.75 K) Superconducting
device
1.8 K
He II Pres.
Q
60 80
Q [W]
DN
70
50
40 65
L
1.9 K
30
50
20
40
10
0
1
10
100
Length, L, [m]
Ph. Lebrun
CAS Erice, 24 April-4 May 2013
38
Tore Supra tokamak at CEA Cadarache, France
Ph. Lebrun
CAS Erice, 24 April-4 May 2013
39
He II p conduction cooling of Tore Supra coils
Ph. Lebrun
CAS Erice, 24 April-4 May 2013
40
He IIp conduction cooling of 45 T hybrid magnet
NHFML Tallahassee
Ph. Lebrun
CAS Erice, 24 April-4 May 2013
41
Conduction in polyimide
Heat transfer across
electrical insulation of LHC
superconducting cable
Ph. Lebrun
CAS Erice, 24 April-4 May 2013
42
The LHC: 1716 superconducting magnets
cooled at 1.9 K in 3 km long strings:
how to transport the heat over such distances?
Ph. Lebrun
CAS Erice, 24 April-4 May 2013
43
Conduction cooling of accelerator string:
the fin problem
A
dz
.
Q
.
q
.
Qtot
.
qtot
.
.
Q + dQ
.
.
q + dq
T1
x.dz T
T2
Distance : z
Linear heat load: x
z
 dz  dX T 
G-M law applied on dz:
q
Energy conservation:
ξ

dq   dz
A
then, q
 d q 
ξ
 d X T   q tot
4.4
 dz 
  L  ξ  q  A 
Q
tot
tot
Ph. Lebrun
q
ξ
 d q
ξ
 4.4   XT2   XT1 
A
A
Calling Qtot the total heat load on the string of length L:
Hence,
A
 L  4.4  X T   X T
ξ q tot

A
L

CAS Erice, 24 April-4 May 2013
44
Conduction in He II
with linear applied heat load
1 W/m
50
From 1.80 K to 1.90 K
0.5 0.4
0.3
45
0.2
40
1.8 K
He II Pres.
L
Qtot [W]
Cold source
He II Sat.
(1.75 K)
DN
35
DN
30
100
25
0.1
20
Qtot= .L
x (W/m)
SC magnet string
1.9 K
80
15
65
10
50
40
5
0
0
Ph. Lebrun
50
CAS Erice, 24 April-4 May 2013
100
150
Length, L [m]
200
45
Cooling the LHC magnet strings
by two-phase flow of He II s
• Monophase
• Excellent thermal conductivity
• Good dielectric strength
• Fixed temperature
• Small flow, no pump
Ph. Lebrun
CAS Erice, 24 April-4 May 2013
46
Two-phase Flow of Saturated He II
(Mandhane, Gregory & Aziz flow map)
10
Superficial liquid velocity [m/s]
Dispersed
1
Bubble
Slug
0.1
Annular
Stratified
Wavy
Inlet
0.01
LHC
heat exchanger
0.001
0.01
0.1
Outlet
1
10
100
Superficial gas velocity [m/s]
Ph. Lebrun
CAS Erice, 24 April-4 May 2013
47
Investigation of two-phase He II s flow
(CEA Grenoble, France)
• Phenomenology
• Stability
• Pressure drop
• Heat transfer at wall
Data 7.2 g/s 1.77 K
Horizontal line
Code
Wetted perimeter (%)(%)
60
50
40
30
20
10
0
1
3
LHC nominal operation
Ph. Lebrun
CAS Erice, 24 April-4 May 2013
5
Vgs (m/s)
7
11
9
48
LHC magnet cross-section
Ph. Lebrun
CAS Erice, 24 April-4 May 2013
49
Temperature profile of LHC sector
3.3 km
Ph. Lebrun
CAS Erice, 24 April-4 May 2013
50
Contents
•
•
•
•
•
•
Ph. Lebrun
Introduction to superfluid helium
Superfluid helium as a technical coolant
Practical cooling schemes
Refrigeration below 2 K
Specific technology for He II systems
Applications
CAS Erice, 24 April-4 May 2013
51
Challenges of power refrigeration at 1.8 K
10000
SOLID
Pressure [kPa]
1000
Compression > 80
SUPERCRITICAL
He I
He II
CRITICAL
POINT
100
PRESSURIZED He II
(Subcooled liquid)
SATURATED He I
10
VAPOUR
SATURATED He II
1
0
1
2
3
4
5
6
Temperature [K]
• Compression of large mass flow-rate of He vapor across high pressure ratio
 intake He at maximum density, i.e. cold
• Need contact-less, vane-less machine  hydrodynamic compressor
• Compression heat rejected at low temperature  thermodynamic efficiency
Ph. Lebrun
CAS Erice, 24 April-4 May 2013
52
Warm pumping unit for LHC magnet tests
3 stages of Roots + 1 stage rotary-vane pumps
6 g/s @ 10 mbar (1/160 of LHC!)
Ph. Lebrun
CAS Erice, 24 April-4 May 2013
53
Operating ranges
of volumetric & hydrodynamic compressors
Speed N1 < N2 < N3
Pressure
ratio
N1
Pressure
ratio
Stall line
N2
N3
N3
Speed limit
N2
N1
Flow
Volumetric (ideal)
Ph. Lebrun
Choke line
Flow
Hydrodynamic
CAS Erice, 24 April-4 May 2013
54
Cycles for refrigeration below 2 K
HP
4.5 K refrigerator
CC
CC
CC
CC
LHe
~ 2 kPa
CC
2
LP
HP
LP
4.5 K refrigerator
Electrical
heater
LP
MP
LHe
3
CC
CC
CC
HP
4.5 K refrigerator
Sub-atmospheric
compressor
Sub-atmospheric
compressor MP
1
LHe
Sub-cooling
heat exchanger
Heat load
“Warm”
Compression
Ph. Lebrun
Heat load
“Integral Cold”
Compression
CAS Erice, 24 April-4 May 2013
Heat load
“Mixed”
Compression
55
Flow compliance of “mixed” compression
Flow (variable)
P out (fixed)
P inter
Stall line
N3
Volumetric
N2
Volumetric
Choke line
N1
P inter
Hydrodynamic
P in (fixed)
Flow
For fixed overall inlet & outlet conditions, coupling of the two machines
via P inter maintains the operating point in the allowed range
Ph. Lebrun
CAS Erice, 24 April-4 May 2013
56
Simplified flow-schemes
of the 1.8 K refrigeration units of LHC
4.75
bar
9.4bar
WC
0.59bar
0.35bar
WC
WC
WC
HX
HX
Adsorber
CCHeat
Intercepts
Adsorber
HX
T
4.6bar
HX
CC
T
CC
CC
T
CC
CC
CC
4K,124
15mg/
bar
s
20124
K,1.3g/
bar
s
Air Liquide Cycle
Ph. Lebrun
CC
4K,15mbar
124g/s
20K,1.3bar
124g/s
IHI-Linde Cycle
CAS Erice, 24 April-4 May 2013
57
Cold hydrodynamic helium compressors
Air Liquide
Ph. Lebrun
IHI
CAS Erice, 24 April-4 May 2013
58
Cold under
vacuum
300 K under
atmosphere
Specific features of LHC cold compressors
Active
magnetic
bearings
Fixed-vane
diffuser
Outlet
Spiral volute
Pressure ratio
2 to 3.5
Ph. Lebrun
3-phase induction
Electrical motor
(rotational speed:
200 to 700 Hz)
Inlet
CAS Erice, 24 April-4 May 2013
Axial-centrifugal
Impeller (3D)
59
Isentropic efficiency [%]
80
LHC
CEBAF
70
60
Tore Supra
Temperature (T)
Performance of LHC cold compressors
P2
2
2'
P1
50
1
40
30
20
Entropy (s)
10
0
1985
1993
2000
Year of construction
Ph. Lebrun
CAS Erice, 24 April-4 May 2013
H 2'  H1
ηis 
H 2  H1
60
Warm subatmospheric screw compressors
125 g/s @ 0.35 bar
or
2 x 3900 m3/h @ 15 °C
Kaeser
Mycom
125 g/s @ 0.6 bar
or
4600 m3/h @ 15 °C
Ph. Lebrun
CAS Erice, 24 April-4 May 2013
61
Isothermal efficiency
of warm subatmospheric compressors
Isothermal
efficiency
P2
.
Qcomp
Isothermal efficiency [%]
60
50
40
Screw compressors
30
20
Liquid ring pump
10
P1
Tore Supra
LHC Supplier #1
LHC Supplier #2
TESLA
0
0
Ph. Lebrun
20
40
60
Suction pressure [kPa]
80
CAS Erice, 24 April-4 May 2013
100
T0 = 300 K
 P2 
n  R  T0  ln  
 P1 
η th 

Q
comp
62
C.O.P. of LHC 1.8 K units
4.5 K refrigerator part
1.8 K refrigeration unit part
COP [W@RT / W@1.8K]
1000
800
600
400
Carnot Limit
200
0
Air Liquide
Ph. Lebrun
CAS Erice, 24 April-4 May 2013
IHI-Linde
63
Contents
•
•
•
•
•
•
Ph. Lebrun
Introduction to superfluid helium
Superfluid helium as a technical coolant
Practical cooling schemes
Refrigeration below 2 K
Specific technology for He II systems
Applications
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64
Efficiency of Joule-Thomson expansion
.
m
3
LHe
1 1'expansion
valve
2
Sat. He II
1.8 K, 16 mbar
sub-cooling
HX
1' expansion
valve
2
3
.
Q
Sub-cooling efficiency :
LHe
1
.
m
Sat. He II
1.8 K, 16 mbar
H3  H 2
sc 
H3  H0
.
Q
Enthalpy of pure liquid
T1’ [K]
H3-H2 [J/g]
H3-H0 [J/g]
sc [%]
without
4.5
12.6
23.4
54
with
2.2
20.4
23.4
87
Sub-cooling
Ph. Lebrun
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65
Subcooling before J-T expansion
Pressure [kPa]
1000
Sub-cooled liquid @ 2.2 K
Saturated liquid @ 4.5 K
1
1’
Saturation dome
100
13 % of GHe produced in expansion
10
46 % of GHe produced in expansion
0
1
0
2
3
2
10
20
30
40
Enthalpy [J/g]
Ph. Lebrun
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66
Prototypes of subcooling HX for LHC
Mass-flow: 4.5 g/s
DP VLP stream: < 1 mbar
Sub-cooling T: < 2.2 K
SS Coiled Tubes
SNLS
Romabau
DATE
Perforated
Copper Plates
with SS Spacers
Ph. Lebrun
Stainless Steel Plate
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67
Protection against air inleaks
•
•
Motor shaft of warm sub-atmospheric compressors placed at the
discharge side to work above atmospheric pressure.
For sub-atmospheric circuits which are not under guard vacuum or not
completely welded, apply helium guard protection on dynamic seal of
valves, on instrumentation ports, on safety relief valves and on critical
static seals
PT
He guard header
HP helium
Evacuation
for periodic rinsing
I
VLP circuits
Safety valves
Ph. Lebrun
Instrumentation and components
not completely welded,
without double O-ring joints
Static seal
with double
O-ring joints
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68
Contents
•
•
•
•
•
•
Ph. Lebrun
Introduction to superfluid helium
Superfluid helium as a technical coolant
Practical cooling schemes
Refrigeration below 2 K
Specific technology for He II systems
Applications
CAS Erice, 24 April-4 May 2013
69
High-field magnets for high-frequency NMR
900 MHz  21.2 T
Ph. Lebrun
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70
The European X-ray FEL, DESY, Hamburg (Germany)
Very brilliant, ultra-short
(100 fs) pulses of X-rays
down to 0.1 nm
Based on s.c. e linac
Beam energy 17.5 GeV
Beam power 600 kW
Linac length 1.7 km
928 superconducting RF
cavities operated at 2 K
Refrigeration 2.5 kW @ 2 K
Ph. Lebrun
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European Spallation Source, Lund (Sweden)
5 MW long pulse source
•≤2 ms pulses
•≤20 Hz
•Protons (H+)
•Low losses
•High reliability, >95%
•2.5 GeV
Ph. Lebrun
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International Linear Collider (ILC)
e+ e- linear collider
Collision energy 500 GeV c.m. initially, later
upgrade to ~1 TeV c.m.
Overall length 31 km
Key technology: SC RF cavities
Global Design Effort
No central laboratory
World-wide collaboration
Site-specific studies
conducted on sample sites
Ph. Lebrun
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Conclusion
•
•
•
From a laboratory curiosity and a hot research topic in condensedmatter physics, superfluid helium has become a state-of-the-art
cryogen for cooling large superconducting devices such as high-energy
accelerators, tokamaks and research magnets
Projects such as TORE SUPRA, CEBAF, SNS and LHC have triggered
vigorous development programmes in laboratories and industry
concerning flow and heat transfer, refrigeration techniques,
instrumentation and engineering
Superfluid helium remains an enabling technology for NMR magnets
and future large projects using high-field superconducting devices,
e.g. the European X-FEL, ESS, ILC. The unique hydrodynamic
properties of the fluid can also be used per se, e.g. in turbulence
research
Ph. Lebrun
CAS Erice, 24 April-4 May 2013
74
Application range
of low-pressure He compressors
100
Warm
Integral C
old
Mx
i ed
FNAL/JAERI
Suction Pressure [kPa]
~ 20 000 m3/h @ 15 °C
Screw Compressors
10
BNL
Superf luid
MASCE
WPU
CEBAFTEST
TESLA
CEBAF
CERNTEST
CENG
TTF
1
1
10
TORESUPRA
CERNCCU
LHC
100
1000
Mass-FlowR
ate [g/s]
Ph. Lebrun
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