Overview

of the KSTAR commissioning

M. Kwon

3 June, 2008

1. To test the components and systems after system integration.

2. To demonstrate that systems are in accordance with the design values and the performance criteria.

3. To identify any defect preventing the device operation and plasma experiments.

Commissioning Objective

1. Vacuum quality in every environment, before & after cool-down.

2. Controlled cryogenic cool-down of all superconducting magnet

system.

3. Status of the SC magnet assembly without individual cool-down

test.

4. Performance of the Nb3Sn magnet system during the 1st plasma

discharge.

Checkpoints during the Commissioning

Commissioning Milestones

1st PlasmaJune 30

Cooled-down

May 02

• Vacuum pumping system operation• VV baking operation• Discharge cleaning• Gas fuelling system operation

• Base pressure of VV

• Target : 5 x 10-7 mbar, achieved < 3 x 10-8 mbar

• Base pressure of cryostat at room temperature

• Target : 1 x 10-4 mbar, achieved < 1 x 10-5 mbar

• VV baking : 100 0C

• DC glow discharge cleaning(H2, He)

• Fueling system operation & testing

Major Operation

Operation Results

Vacuum commissioning

• Gas : He• No. of Electrodes : 1• RF Power : 200 W• DC Bias Voltage : 400 V• DC Current : 4 A• Operation Pressure : 6.0 10-3 mbar

Vacuum vessel pressure (Mar. 08)

Cryostat pressure (Mar. 08)

• Operation & control of the helium refrigeration system & helium distribution system (9 kW @ 4.5 K).

• Controlled cool-down of cold systems: SC magnet, structures, busline, thermal shields, current leads.

• Superconducting phase transition

Major Operation

Control & Monitoring

• Hydraulic parameters • Temperature, pressure & flow distribution

• Mechanical monitoring• Stress & displacement

• Superconductor monitoring• Coil resistance & SC phase transition

• Safety• Vacuum & helium pressure monitoring

Cool-down commissioning

TF coil CS coil PF Coil

conductor Nb3Sn & Incoloy 908 Nb3Sn & Incoloy 908Nb3Sn & Incoloy 908 (PF5)

NbTi & 316 LN (PF6,7)

No. of coil 16 4 pair 3 pair

Total length 10.2 km 3.8 km 11.2 km

Cooling channel of each coil 4 CS1 : 10, CS2 : 8CS3 : 4, CS4 : 6

PF5 : 8 PF6 : 8, PF7 : 6

Length of each channel 160 m 67 mPF5 : 176 m

PF6 : 315 m, PF7 : 285 m

Cold mass 170 ton 60 ton 70 ton

Operating temperature 5 K 5 K 5 K

Coolant4.5 K SHe

P > 5.5 bar Mass flow rate > 300 g/s

4.5 K SHe P > 5.5 bar

Mass flow rate ~150 g/s

4.5 K SHeP > 5.5 bar

Mass flow rate ~ 150 g/s

CS1U

CS2U

CS3UCS4U

CS1L

CS2LCS3LCS4L

KSTAR SC coils

Cool-down of KSTAR

In April 26, KSTAR superconducting coils were successfully cooled-down.

Controlled cool-down (∆T < 50 K)

The maximum temperature difference in the magnet structures was carefully controlled within 50 K during the cool-down.

Mass flow rate• The gaseous helium of maximum 200 g/s was supplied by the clod box.• After cool-down, the SC coils were cooled by the 600 g/s supercritical helium of

cryogenic circulator to its operating temperature.

Temperature distribution in the thermal shields

• The cryostat thermal shields were well cooled below 70 K. • The maximum temperature of the CRTS measured in 180 K on the blank cover plate without

cooling lines. • The temperature of the vacuum vessel shield was distributed in 90 K ~ 120 K

Cryostat vacuum during cool-down• After cool-down, the vacuum pressure of the cryostat reached to 2.6E-8 mbar. • The partial pressure of each gas greatly decreased as coil cooling and the

residual helium gas was kept almost constant pressure level.

SC transition measurement

• The superconducting phase transition of the SC coils was clearly observed during the 1st cool-down.

• The SC transition of Nb3Sn and NbTi coils appeared at 18K and 9K, respectively.

KSTAR Coils

SCstrand

Tc [K]Expected Measured

[K] [K}

TF Nb3Sn 18.3 17.9

PF1PF1U Nb3Sn

18.3 18.2PF1L Nb3Sn

PF2PF2U Nb3Sn

18.3 18PF2L Nb3Sn

PF3PF3U Nb3Sn 18.3 18

PF3L Nb3Sn 18.3 18

PF4PF4U Nb3Sn 18.3 17.9

PF4L Nb3Sn 18.3 18

PF5PF5U Nb3Sn 18.3 18

PF5L Nb3Sn 18.3 18

PF6PF6U NbTi 9.2 10

PF6L NbTi 9.2 9.8

PF7PF7U NbTi 9.2 10

PF7L NbTi 9.2 10

The measured Tc of the 16 TF coils

SC transition measurement

[The results of the measured Tc of SC coils]

Joint Resistance• The voltage drops were measured at each SC bus-line, which consists of several

numbers of electrical joints.• The joint resistances were estimated by linear fitting to the measured V-I curves.• All of the KSTAR lap joint resistances satisfied the design value of 5 nΩ.

CoilLap Joints

[EA]Total R

[nΩ]Average

[nΩ /joint]Design Value

TF 8 11.1 1.38

< 5 nΩ

PF1 7 15.6 2.23

PF2 7 11.1 1.59

PF3 12 20.3 1.69

PF4 12 17.4 1.45

PF5 12 25.2 2.1

PF6 12 11.2 0.93

PF7 8 4.11 0.51

[The KSTAR lap joint of the SC bus-line]

TR No.

Radial displacements (mm), @ 11K

Sensor indication(Reset at 311 K)

Contractionfrom 293 K

FEManalysis

Deviation

TR 01 -8.59 -7.93 -8.2 -0.27

TR 02 -8.26 -7.67 -8.2 -0.53

TR 03 -8.33 -7.66 -8.2 -0.54

TR 04 -8.26 -7.71 -8.2 -0.49

Radial displacements of the toroidal ring

Reference ; “KSTAR Magnet Structure Stress Analysis”, Efremove, July, 2003

• Radial displacements of the toroidal ring from 293 K to 11 K were measured in the range of 7.66 mm ~ 7.93 mm, which is comparable of the FEM analysis result.

• The maximum deviation of the segments is just 0.006 % as compared with the diameter of the ring, 5780 mm.

• Superconducting joint resistance measurement

• Insulation test at cryogenic temperature

• Magnet power supply control

• TF coil charge & discharge : up to 15 kA (B0 = 1.5 T, Bm = 3.1 T)

• PF coil charge & blip operation

Major Operation

Control & Monitoring

• Coil current & voltage• Field on SC magnet, in vacuum vessel• Coil performance under the dc & pulse field variation• Interlock & safe discharge (quench discharge)

SC Magnet Commissioning

TF magnet SD & FD test

SD & FD test at 5 kA

QD & MD adjust

TF coil charging test (15 kA, 8 hr)

PF Blip Operation

PF1 : 2.7 kA

PF2 : 2.1 kA

PF3 : 2.8 kA

PF5 : 2.1 kA

PF6 : 2.3 kA

PF4 : 2.6 kA

PF7 : -2.3 kA

PF1 coil blip test

TF & PF1 coil charging test

ICRF Discharge test

Cathode voltage (yellow)

Body voltage (green)

Beam current (pink)

Body current (blue)

RF power: ~ 400 kW, 100 ms pulse

Beam current

Forward RF signal

Backward RF signal

Forward RF signal(at the end of transmission line)

Gyrotron operation parameters (80 kV, 18 A, 100 ms)

84 GHz, 500kW CPI Gyrotron(2008. 4. 21)

Gyrotron installation: 2008. 4. 21 Gyrotron Aging: 2008. 4. 28 –

400 kW, 100 ms RF aging Transmission line is under aging

Status of KSTAR ECH commissioning

• Fueling & wall conditioning

• Heating system readiness test

• MPS and BRIS tuning

• ECH pre-ionization

• Plasma start-up and optimization

Major Test

Control & Monitoring

• Coil performance under the dc & pulse field variation• Measurement of plasma parameters (current, density, image, loop voltage, H-alpha etc.)• Change of ECH parameters• Plasma control and monitoring

Plasma Start-up Commissioning

KSTAR SHOT number 586(2008. 05. 30)

00.5

11.5

2

0500

100015002000

00.10.20.30.4

012345

01234

0200004000060000

-0.1 -0.05 0 0.05 0.1 0.15 0.2

ECH Power (A.U)

PF Current (A)

Line Density (1019 m-2)

H-α Intensity (A.U)

Loop Voltage (V)

Total Current (A)

Time (sec)

KSTAR will be one of the most effective devices for ITER relevant operation and physics for reliable fusion reactor.

Accumulation of the technical know-how for the superconducting tokamak operation

Leading the high performance steady-state plasma experiment

Goal

Phase

•First plasma•SC tokamak operation technology (Bt = 3.5 T)

•D-shaped plasma (Ip >1 MA, D2)

•H -mode achievement

•Collaboration for operation

•Long pulse operation (tpulse> 100 s)

• AT operation Tech. (Pheat< 20 MW)

•ITER pilot device operation

•Collaboration for steady-state operation

•Long pulse operation (tpulse > 300 s)

•Stable AT operation (Pheat > 20 MW)

•ITER satellite operation

•Collaboration for advanced research

•High beta AT mode & long pulse

•Reactor material test (divertor, blanket)

SC Tokamak Operation

Technology

Steady-state Operation

High-beta, AT Operation

Steady-state AT

Activities

1st Plasma D-D Reaction 100 s1MA Ion Temp > 10 keV

Year

PHASE 1 PHASE 2 PHASE 3 PHASE 4

08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 2507

ITER Construction Start ITER 1st Plasma

Milestone

Long-term operation plan

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