BI Yanfang BAI Hongyu
The cryogenic system is one of the key auxiliaries for a SC tokamak device. It includes two types of equipment: the cryoplant and the distribution system. The cryoplant provides supercritical helium (SHe) to cool the two sets of coils for the toroidal field and poloidal field (TF and PF), their superconducting (SC) buslines, and the magnet support structures, and provide liquid helium to the current leads, and also supplies a cold helium flow to 80K shields. The cryopumps for the divertors, pellet fuelling, gyrotrons and some diagnostics are also the potential users.
3.1.1 Heat Loads
During the tokamak operation there are three types of heat loads. 1) Steady state heat loads come from the thermal radiation, solid conduction through the support structure, instrument wires and current leads, residual gas conduction in the tokamak device, control dewars and current lead box, Joule-heat in the conductor joints and current leads.2) Pulsed heat loads deposited in the magnet system include the eddy current losses in the massive support structure and in conductor joints, AC losses in the conductors due to electromagnetic variations and nuclear heating. 3) Additional heat load comes from the work of SHe cycle pump. The pulsed heat load can much higher than the refrigeration capacity of cryoplant. The variation of massive magnet structure temperature and LHe level in subcooler can smooth the total heat loads.
Following heat loads should be estimated.
1) Heat Loads of EAST Magnet
· Heat is conducted from the magnet supports and from the measurement wires and pipes.
· Radiation from the thermal shields.
·
Residual gas conduction between the magnets and thermal shields.
· Internal heat loads due to the operation of the magnets include AC losses in conductors, eddy current losses in structures and resistive losses in CICC joints of TF and
PF coils.
· For steady state operating mode the nuclear heat will be dominant heat load for the
TF coils and be also deposited in the PF coils in the vicinity of the plasma chamber ports.
2) Heat Loads of the control dewar and transfer lines
· Thermal radiation from the 80K shields is deposited on the surface of the subcooler
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and 4K pipes.
· Heat is conducted through the control valves and the centrifugal SHe pumps.
3) Liquid helium consumption for TF and PF current leads
One pair of the current leads for 16 TF coils and 12 pairs for the PF coils are required according to the single-null divertor configuration.
·
According to 4T TF requirement for the phase II, the design current of TF leads is
16kA. There is ~12% margin for the 14kA rated current in the phase I. The TF current leads need 1.6 g/s of helium flow.
· The transport currents in PF leads are pulse operating mode and do not stay at the nominal value all the time. We choose 7 kA as the optimum currents, so it results much lower average consumption of liquid helium. The design concept comes from FZK current leads of 30kA for POLO coil, for which optimum current is 12-15 kA. The 12 pairs of PF current leads require a total LHe consumption less than 10 g/s.
4) SHe pumping power of cooling cycle for TF coils
· The TF and PF coils require more than 370 g/s mass flow when the tokamak operation.
The refrigerator cannot supply so high mass flow.
cases.
· The driving power of SHe pumping is an additional heat load, which depends on mass flow and pressure head provided. According to the pump motor power for 220 g/s mass flow and 0.9 bar pressure head given by Barber-Nichols Inc. is 280W and the efficiency is 0.52 (see Table 1). So we can calculate that the additional heat load is about
550-600W for a pump with 260g/s mass flow and 1.5bar pressure head (assume isentropic compressing and efficiency of 0.5).
Table 1. Technical Parameters of SHe Pump (Issued by Barber-Nichols Inc.)
Parameters
Outlet pressure
Pressure head
Mass flow
Isotropy efficiency
Bearing life
Rotating speed
Pump power
Unit bar bar g/s hr rpm
W
Data
4
0.9
220
>= 0.52
>= 3600
~6200
280
Comments
Supercritical helium
Motor has >50% of driving-capacity margin.
Table 1 summarizes the major heat loads in the magnets. The table also includes the losses in two states: the normal operation and idle (standby).
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Table 2. Heat Loads (W) and Liquid Helium Requirements for Current Leads
Item
Operation
4K 80K
Idle Operation Idle
Radiation (plasma chamber operating temp. at 100 ℃ , outer shield with MLI and ε inner shield
=0.1)
Convection of residual gas in cryostat
(<1.33*10 -3 Pa)
Conduction through support structure
Conduction through instrumentation
CICC joints (r

5n

, 35 TFC joints
@14kA in dc mode, 30 PFC joints at 14.5kA in pulse mode)
AC loss including coil cases and windings* (1200 s / shoot), but the ac loss from plasma disruption not included.
Nuclear heating (2.3x 10 15 neutron/s, pulse/shoot period =33% )**
SC bus lines and cryogenic transfer lines
(30 m)
Coolant control box (~50 Valves)
Δ P)
SHe pump (260g/s mass flow and 1.4bar
Miscellaneous
Current leads***
Sum
78
17
30
<20
36+4
160(TF coils)+
45(PF coils)
110
~40
100
~550
~50
11.6 g/s
1240 W +
11.6
g/s
78
17
30
<20
0
0
0
~40
100
<100
~50
6 g/s
440 W
+ 6 g/s
12,000
60
<800
<40
-
1000
800
1000
500
1000
17,200
5,40
0
60
<800
<40
-
0
0
1000
500
1000
8,800
* A coupling loss time constant of 20 ms of CICC is assumed.
** The average values are for a 400 s burn with a 1,200 s pulse repetition. coil.
***The current leads for PF coils should be designed following FZK leads for POLO
3.1.2 Refrigeration and Liquefaction Requirements for Cryoplant
For the normal operation of EAST tokamak the capacity of cryoplant should be larger than the total head load and 1.5 times of the average heat loads. 2.2 kW/4K refrigeration was chosen in 1998. At the beginning stage of EAST tokamak the plasma burning time will be much shorter than 400 s and the nuclear heat will be not strong. In the case of TF coils operating at 3T toroidal field and 12 kA current, SHe mass flow can be reduced, therefore the pumping loss is also decrease The refrigerator has some margin to support the device normal operation. For 3.5T TF of the phase II, the cryoplant power must increase
500-1000W/4K. There are two solutions: 1) running the piston refrigerator for EAST tokamak, 2) running MG300/1.8 refrigerator, but its piston expander should be substitute
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with one turbine. The compressors are also to be increase. Considering enhancement of the cryoplant the diameters of pipelines should select according to requirement for phase II.
The basic design requirements are as follows:
· Stable operation in a long term (more than 8000 hrs). All the components should be as reliable as possible because it takes about 2-3 weeks to cool down EAST magnets and 3-4 months to keep the device at the operating temperature.
· Full automatic control. It is necessary for the cryogenic system to eliminate human errors of the operators during the SC magnets cool-down , warm-up , steady-state operation, and to ensure safety when quenching in one of the coils or one of machines out of running or power failure .
· Cost-minimum design is also required because of limited budget.
· Cryoplant capacity is able to enhance to satisfy requirement for phase II.
3.1.3 Design of 2kW/4K Cryoplant
The cryoplant consists of a refrigerator/liquefier, compressor station, two purifiers and a LHe storage vessel. The capacity of cryoplant and loop design depends on the heat loads and requirements of the all cooled components.
3.1.3.1 2kW/4K Refrigerator/Liquefier
3.1.3.1.1 Process description
According to the estimation of the heat loads, the helium refrigerator is designed at a capacity of 1050 W/3.5 K + 200 W/4.5 K + 13 g/s LHe + 13 kW/80 K. It is approximately equivalent to a 2 kW helium refrigerator at 4 K. The helium refrigeration system has two refrigeration cycles. The refrigeration at 3.5 K and 4.5 K as well as the liquefaction are produced by the primary cycle. The 80 K refrigeration is produced by another cycle. figure
1 shows a schematic flow sheet of the refrigerator.
In the 3.5 K refrigeration cycle, helium first is pre-cooled by liquid nitrogen to 80 K.
To get the full refrigeration power, almost 10 m
3
/day of liquid nitrogen is to be purchased from companies. Three turbines are used in the cycle. Turbine T1 and T2 are arranged in series. They have a mass flow rate of 100 g/s. Before the J-T cooling stage, 110 g/s helium expands through turbine T3 from 18.8 bar to 4.5 bar. The helium is then liquefied by the
Joule-Thomson effect in liquefaction mode or is supplied to cool the SC magnets. To attain
3.5 K temperature an oil ring pump is used to reduce the pressure to 0.47 bar of saturated helium in the control dewar. The pump is designed operating at the suction pressure of 0.37 bar and the volumetric flow rate of 3000 m
3
/h, that gives a refrigeration of 1050 W/3.5 K.
The refrigerator usually operates at mixed mode with liquefaction and refrigeration due to the current leads will be cooled by the helium vapor. The temperature-entropy diagrams are shown on figure 2. The energy flow diagram of the refrigerator is shown on figure 3 and
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figure 4, which gives the energy efficiency of 21.8%.
3.1.3.1.2 Turbines
Four turbine modules supplied by Geliymash (Russia) are centripetal with impeller of radial-axis type. The rotor is rotating in combined gas-oil bearings. Radial bearing from impeller is a gas-static one and radial bearing from the side of brake is an oil bearing. Axial thrusts to the rotor are taken by hydrostatic thrust bearings. On the shaft end from the side of impeller there is labyrinth seal with rotating crests that decrease the leakage along the shaft. Table 3 shows the specification of the turbines.
Table 3 Turbine Specifications
Parameters
Inlet Pressure (MPa)
Inlet Temperature (K)
Outlet Pressure (MPa)
Outlet Temperature (K)
Expected Efficiency
Mass Flow Rate (g/s)
Power (kW)
Speed (rpm)
Diameter (mm)
Turbine 1 Turbine 2 Turbine 3 Turbine 4
1.9
45.9
0.69
20.6
1.88
8.72
1.9
80
0.7
34.4
0.76
100
0.12
12.4
0.77
100
0.45
6.4
0.67
110
0.53
56.5
0.74
110
6.2
181000
28
4.1
105000
40
0.98
110500
15
13.85
184000
35
3.1.3.1.3 Heat exchangers
Heat exchangers (Ex1~Ex8) are of the aluminum plate-fin type. All the heat exchangers with a total weight about 2 tones will be manufactured in Kaifeng Air
Separation Group Co., Ltd.
3.1.3.1.4 Coldbox
All of the heat exchangers, 80 K and 20 K adsorbers, and four turbines are installed in a vacuum insulated vessel—coldbox. The coldbox is cylindrical, vertical installed and de-mountable type, which makes the maintenance for it feasible. 23 cryogenic valves are installed on the cold box.
3.1.3.1.5 Valve box and valves
There is a vacuum insulated valve box to install the cryogenic valves at the liquid helium temperature level. These valves are used for the distribution of liquid helium, the distribution of helium in the cooling of the superconducting magnets. On the valve box there are 21 cryogenic valves.
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There are 37 cryogenic control valves, 9 manual cryogenic valves and 12 room temperature control valves in the refrigerator. Total number of control valve is about 50.
All of the cryogenic valves were supplied by WEKA and the room temperature control valves were made by Wuzhong.
3.1.3.1.6 10000 L liquid helium dewar
A 10,000 L dewar is used for the storage of liquid helium. It can regulate the cooling capacity of the plant when the heat load increases or decrease and supply other laboratories.
It also can be a cold buffer while a SC coil quench.
3.1.3.1.7 Oil ring pump
The refrigeration temperature of 3.5 K requires the pressure of the control dewar to be
0.47 bar, which is obtained by an oil ring pump. The oil ring pump can reduce the suction pressure to 0.37 bar at the volumetric flow rate of 3100 Nm
3
/h, which gives a refrigeration power of 1050 W/3.5 K.
3.1.3.1.8 Flow sheet
Figure 5-1, -2, -3, -4, -5 show the flow sheet in detail.
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ORP
C1
4.4K
C2
LN
2
T1
T2
T4
T3 Thermal
Shield
3.5 K
Figure 1 Simplified flow sheet of the helium refrigerator
57.4 g/s
N
2
300.0 K
19.5 bar
210 g/s
He
148.5 g/s
293.0 K
1.04 bar
110 g/s
45.9 K
T1
100 g/s
34.4 K
7 bar
20.6 K
T2
8.7 K
5.54 K
T3
4.5 bar
6.4 K
12.4 K
13 g/s
4.4 K
3.5 K
200 W 1050 W
0.47 bar
Entropy
48.24 g/s
293.0 K
0.37 bar
Figure 2 Temperature entropy diagram of the 3.5K refrigeration cycle
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Input exergy 100%
21.8%=Exergy efficiency
Irreversible loss
47.6% Compressors and oil ring pump
5.5% LN
2
Pre-cooling stage
2.2% Ex2+Ex3
3.2% Turbine 1
4.7% Ex4 + Ex5
4.6% Turbine 2
2.6% Ex6
3.2% Turbine 3
4.0% J-T cooling stage
0.6% 3.5 K cooling stage
Figure 3 Energy flow
41.1 + 29 g/s
N
2
19.5 bar
300.0 K
He
5.1 bar
293.0 K
80.0 K
T4
110 g/s
5.2 bar
90.0 K
5.72 kW
19.2 kW
5.3 bar
56.5 K
Entropy
Figure 4 Temperature entropy diagram of the 80 K refrigeration cycle
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去中压筒
液氮
氮气放空
×
×
×
×
×
×
×
×
×
W2670
EX8
S1
去氮屏
EX12
来自氮屏
S2
×
×
S3
EX1
EX9
×
A2310
A/B
N
2
H
2
O
A2312
H
N
2
O
A/B
A2210
A/B
N
2
H
2
O
×
A2212
A/B
N
2
H
2
O
×
Turbine 4
Figure 5-1
2660-1 2660-2
W2660
×
氮气
144

EX2
Turbine 1
碳电阻
碳电阻
×
碳电阻
EX3
×
碳电阻
EX4
×
×
碳电阻 碳电阻
Turbine 2
碳电阻
碳电阻
×
碳电阻
×
碳电阻
A2250
W2251
碳电阻
EX5
碳电阻
EX6
碳电阻
×
碳电阻 碳电阻
Turbine 3
碳电阻
碳电阻
EX7
碳电阻
碳电阻
碳电阻
碳电阻
碳电阻
W2552
B2553
P2555
B2556
W2556
碳电阻
Figure 5-2
碳电阻
P6231 P6211
P6210 P6310
145

×
B3110
W3111
3111-1
3111-2
碳电阻
×
EX10
B3120
W3126
3126-1
3126-2
3120-1
3120-2
碳电阻
碳电阻
碳电阻
碳电阻
去控制杜瓦
氦回气
过冷槽回气
S3
S1
S2
P6311
146
Figure 5-3

氮屏进口
碳电阻
液氦
Dewar 4100
W4118
Dewar 4200
147
B4500
电流引线回气
碳电阻
碳电阻
B5100
碳电阻
液氦
Figure 5-4

碳电阻
碳电阻
EX14
EX13
碳电阻
碳电阻
碳电阻
碳电阻
碳电阻
碳电阻
碳电阻
液氦
B5000
148
碳电阻
碳电阻
碳电阻
Figure 5-5

3.1.3.2 Compressor station
The compressor station consists of the main cycle compressors for 2kW/4K cryoplant, oil removal system and helium recovery system. Figure 6 shows the flow diagram of compressor station.
3.1.3.2.1 Screw Compressors
Screw compressors are used to supply compressed helium to the coldbox. There are five oil injected screw compressors arranged in two stages, with a low pressure stage of three screw compressors and a high pressure stage of two screw compressors.
Three low pressure stage compressors run with a suction pressure of 1.04 bar and an exhaust pressure of 5.1 bar. Each compressor has a mass flow rate of more than 87 g/s and a 200 kW motor. Two high pressure stage compressors run with suction pressure of 5.1 bar and exhaust pressure of 20 bar. Each compressor has a mass flow rate of more than 190 g/s and a 355 kW motor. The compressors are manufactured by Wuhan
New World Refrigeration Industrial Corporation, China.
Two buffers of 100 m
3
(19 bar) each are used to store pure helium for the running of the refrigerator and the cooling of the cold mass. Four control valves are used to control the low pressure, the middle pressure and high pressure of the system. The buffers can be switched to supply and recover helium between the suction side of the low pressure stage compressors and the discharge side of the high pressure stage compressors.
3.1.3.2.2 Oil removal system
The oil contained in the discharge stream of HP compressors is removed by a four-stage oil removal system: a fine oil filter, two coalescers of super-fine glass fiber, and finally an oil absorber of active charcoal. The oil removal system reduces the oil-residuals down to 0.01 ppm(w). Finally the helium stream flows via a silicon gel/molecular sieve dryer, which removes water vapor in helium.
3.1.3.2.3 Helium recovery system
A total gas storage volume of the recovery system is 9000 Nm 3 . Two 100m 3 tanks
(max pressure 19bar) store pure gas, and other mid-pressure tanks store the recovery helium from the system. The recovery helium from other users is stored in high-pressure vessels. Three piston compressors with capacity of 45Nm
3
/h (max pressure 150bar) can recovery redundant gas from the gasholder. For the normal operation the automatic valves can control the pressure of the supply/return lines, and the recovery compressor running is not necessary. At an emergency, for example one of the main compressors malfunctions, a screw compressor with capacity of 321
Nm
3
/h (max pressure 16 bar) will switch on and discharge gas to the pure gas tanks.
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3.1.3.3 Helium purifiers
The cryoplant equipped two cryogenic helium purifiers. The rated pressure is 25 bar and the maximum flow rate is 500 Nm
3
/h. When the cryogenic system starts cooling down the purifiers are used for purging the system. During normal operation of the cryoplant the makeup helium from recovery tank passes through one of the purifiers.
3.1.4 Design of Cryogenic Distribution
The cryogenic distribution system comprises the auxiliary control dewars with a subcooler, two SHe circulating pumps and a system of cryogenic transfer lines that distribute SHe at 4K and 80K helium to the different components of the tokamak.
The flow diagram of the cooling EAST cryogenic components is shown in Fig.7. In the steady state operation there are four kinds of cryogen: 1) supercritical helium for TF and PF coils and for the magnet support structure, 2) liquid helium or two phase helium for current leads, 3) 57K-80K gaseous helium for the thermal radiation shields of EAST cryostat and cryogenic transfer lines, 4) liquid nitrogen for 80K shields of the SC bus lines, control box and current lead box. The condition parameters of cryogen at the numbered points in the flow diagram are listed in Table 4.
Table 4. Cryogen condition At the numbered points in figure 7
12
13
14
15
16
8
9
10
11
6
7
4
5
No.
1
2
3
Cryogen
SHe Supply
SHe Supply
SHe Supply
SHe Supply
SHe Supply
SHe Supply
SHe Supply
SHe Supply
SHe Supply
LHe Supply
GHe Supply
GHe Return
GHe Return
LN
2
Supply
2-Phase N
2
Return
2-phase He Return
5.1
1.15
1.5
1.2
~2
3.2
3.2
1.2
5.3
Pressure [bar]
4.5
4
2.7
4.2
4.2
4.2
3.2
90
4.5
81
80
4.5
3.8
3.8
4.4
57
Temperature [K] Flow rate [g/s]
5.54 110
3.8
3.8
250
250
3.8
3.8
3.8
3.8
75
20
15
60
40
10
2~50
110
110
100
~100
~100
10
The detail description of cryo-distribution system are as followings.
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100m 3 Gas Holder
28x0.4m
3 /150bar cylinders
2x4m 3 /150bar
HP vessels
20m 3 /30bar+2x50m 3 /21bar
MP tanks
50m 3 Gasbag
For evacuation p
50m 3 Gasbag
HP compressors
MP compressor
Stage I
From 2kW/4K Cryoplant
1.05bar, 205g/s p
Inter-cooler
Water p p
Stage II
From 80K shields
5bar, 110g/s
After-cooler
Water
Oil removers
Adsorber
Fig.6 Flow Diagram for Compressor Station and Recovery System
2x100m 3 /19bar
Buffers
Dryers cryogenic
Purifiers
Filter
To 2kW/4K + 12kW/80K
Cryoplant 20bar, 360g/s
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3.1.4.1 Cooling loops for TF coils and support structure
A centrifugal pump supplies 3.8 K SHe to the TF coils and coil cases at inlet pressure of 4 bar, and the maximum flow rate of 260 g/s. The pressure head loss results from the stubs on the CICC, and it depends on mass flow rate for TF coils. For the designed 260 g/s the pressure drop of the TF magnet is more than 1.5 bar. In the case motor power for the pump requires 550W. The additional heat load is comparable with others, and total heat load almost exceeds the cryoplant capacity. Therefore we have to reduce the toroidal field of the phase I from 3.5T to 3T. It is reasonable if we choose 3.5T as the TF for the phase II. The TF of KSTAR tokamak using Nb
3
Sn
CICC for TF coils is 3.5T only. The TF coils operate at relate higher field, store a large amount of magnetic energy, and suffers fast-pulsed PF disturbance while plasma initiation or plasma disruption. To ensure TF magnet operating stable, enough stability margin is necessary. The capacity of cryoplant must increase 500W/4K for phase II.
Figure 8 shows the cooling schema of TF coils.
The TF coil case and inter-case structure are the main support structure for EAST tokamak. In Fig. 8 cooling loops of the TF coil cases are connected to the coil windings in series and the cooling flow is provided by the pump. In order to reduce
SHe pumping power it is better to shift the TF coil cases from the pumping loop to the downstream of the PF coil loop. 100 g/s mass flow can supply two cases connected in parallel. Then the flow is cooled via a 4.4K subcooler seven times and provides the other 14 cases. According to calculation the heat load of the gravity support of TF magnet is 32 W only, so special cooling for it is not necessary.
3.1.4.2 Cooling loops for the PF coils
The PF coils are operated in fast-pulsed modes and suffer stronger disturbance from ac losses when plasma initiation. So there is the large possibility of PF coil quench. To avoid TF coil quenching caused from a quenched PF coil, the cooling loops for PF and TF coils should be independent each other.
The mass flow cooling PF coils comes from the 2kW/4K coldbox. But the flow rate of 110 g/s is not enough for all PF coil cooling-channels parallel connected. We divide the PF coils in two sections. The SHe flow for the second section is re-cooled via a 3.5K subcooler prior. To regulate mass flows in the parallel-connected cooling lines, some control valves are employed. figure 8, figure 9, figure 10 show the cooling schemes.
3.1.4.3 Cooling loops for the 80K thermal shields
The thermal shields for TF&PF magnets are cooled with helium gas. The 110g/s
152

flow at 5.2bar can cool down the shields from room temperature and keep them at
70-90 K in idle mode. Liquid nitrogen is used to enhance cooling capacity when baking the plasma chamber. For the 100 ℃ baking mode the heat load on the inner shields increases 2.4 times. A LN
2
cooler or heat exchanger inserts between two cooling sections to keep the shield temperature at a reasonable level. Each section consists of 8 parallel cooling units. Figure 10 shows the cooling loops.
3.1.4.4 Control dewar and sub-cooler
Many of the cooling loops for TF coils, coil cases and PF coils are connected in parallel. To control the mass flow rate a number of regulation valves are used. There are some on-off valves and safety valves for leak check and emergency. The valve are mounted in a control dewar, which locates near EAST tokamak. Two centrifugal pumps for SHe cycle and a 3.5K subcooler, 1000 liter volume, are also installed in the dewar. To pre-cool SHe flow entering 3.5K subcooler and to separate helium vapor of down-stream from PF coils, a 4.4K LHe vessel, 500 liter volume, is necessary. If possible, the LHe vessel is also mounted in the control dewar.
3.1.4.5 Cryogenic Transfer Lines
The cryogenic transfer system comprises four lines: 1) 2kW/4K refrigerator to control dewar, 2) control dewar to TF coils, 3) control dewar to PF coils and 4) 80K control dewar to thermal shields. All the transfer lines are insulated with vacuum-MLI.
Their vacuum must segregate from the coldbox and also from EAST tokamak device.
In order to make the transfer lines compact multi transfer lines share a common vacuum tube. Vacuum segregation will increase addition heat loss, taking grate care to reduce solid conduction is necessary. To pay more attention on compensation for thermal contraction and on leak check is also very important.
3.1.4.6 Connection to tokamak device and cold box
The connections of the cryogenic transfer lines with the coldbox and EAST tokamak are more complicated design. The designers must consider approachability for welding, Distances of transfer lines at the connection section are usually larger.
The vacuum tube should be dismountable to repair leakage at connection.
3.1.5 Cooling of Superconducting Bus Lines and Current Leads
For the single null configuration of divertor field, EAST tokamak has 13 pairs of the SC bus lines, which are assembly within a common vacuum tube. One pair of the bus lines used for the TF magnet .
3.1.5.1 SC bus lines configuration and cooling
The SC bus line is made of the same CICC as for TF coils. So mass flow for a
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bus line about 2.5 g/s. In the case of 10g/s mass flow to cool 13 pairs of the 15kA SC bus lines, every four SC bus lines for PF coils and two lines for TF coils are parallel connected, then series connected together. The total cooling channel length is less than 80 meters, and is comparable to that of the PF coil. The down-steam after cooling bus lines goes to the current leads for PF coils. Figure 11 shows the cooling loop for all SC bus lines.
3.1.5.2 SC bus line connection to current leads and tokamak device
13 pairs of current leads assemble in a common vacuum box, which is installed in the tokamak hall. The SC busline connections with the current leads are low section of the leads. To avoid extra busline joints, the busline terminations will be formed in site.
The busline connections with tokamak device are divided two sets: 1) connecting to TF coils, and PF 11-14 coils; 2) connecting to the central solenoid coils and divertor coils, and locate under an edge port and the central port, respectively.
3.1.5.3 Cooling of current leads
TF current leads consume 1.6 g/s of LHe, which is supplied by 10,000L dewar in the cryogenic hall or the 500L LHe vessel in tokamak hall. Cooling for the 12 pairs of
PF coil current leads is provided with the 10g/s down-stream from the SC buslines.
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⑾
4.5K GHe
①
SHe
⑩
4.4 K
To compressors
PF leads
He Return
⑿
57 K He Supply
⒂
⒁
LN
2
supply
N
2
Return
LHe
TF leads
⒃
LHe
Cold buffer
3.8K G He
3.5 K
②
TF Coils
TF1~4
TF5~8
TF9~12
TF12~16
Center Solenoid Coils
④
CS1~6
⑤
PF7~8
⑥
⑥
PF13~14
3.5 K Subcooler
PF Coils
⑨
⑦
⑧
PF9~10
PF11~12
SC Bus lines
Shield 1
Shield 2
Shield 3
Case 1~4 a
Case 5~8 a
Case 9~12 a
Case13~16a
Figure 7 Flow diagram of EAST cryo-distribution system
TF Coil Cases
Case 1~4 b
Case 5~8 b
③
Case 9~12b
Case13~16b
⒀
Shield 4
Shield 5
Control valve(FC)
Control valve(FO)
ON/OFF valve(FC)
ON/OFF valve(FO)
155

回冷缓冲罐
降温路
氦循环泵排气
回氦循环泵进口
HT-7U 纵场冷却
流程图(方案二)
装置主体
纵场分系统
圈
绕
组
纵
场
线
Bus Line
Bus Line
Figure 8 Cooling loop for TF magnet
156

回中压筒
回冷缓冲罐
外
侧
米
外
侧
CS1-6
米
外
侧
PF11-12
米
Figure 9 Flow diagram for PF coils
外
侧
米
157
外
侧
PF9-10
米
HT-7U
极向场冷却
流程图
弹簧安全阀
气关式气动开关阀
气开式气动开关阀
气关式气动调节阀
气开式气动调节阀
绝缘子
计算机功能
装置主体
极向场分系统

接LN2传输线
接常温低压路
Figure 10 Cooling loop for 80 shields
158
氦
制
冷
机
绝缘子
气动调节阀
手动截止阀
弹簧安全阀
计算机功能

PF
Coils
Control Dewar
TF+
TF-
PF11-
PF12+
PF12-
PF13+
PF13-
PF14+
PF14-
PF14+
CS4-
CS5+
CS5-
CS6+
CS6-
PF7+
PF7-
PF8+
PF8-
PF11+
CS1+
CS1-
CS2+
CS2-
CS3+
CS3-
CS4+
Figure 11 Flow diagram of SC bus lines for TF and PF coils
159
白红宇 2002.11.7
HT-7U 极向场
BUS LINE 冷却流程
Connect
To
Current
Leads