22nd IAEA Fusion Energy Conference , Oct 13, 2008, Geneva, Switzerland

Presented by Joo Shik BakNational Fusion Research Institute

Daejeon, Republic of Korea

Overview of Recent CommissioningResults of KSTAR

2

Basic R&D, Conceptual Design (95.12 – 98. 8)

Engineering Design (98. 9 - 02. 5)

Machine Construction & Assembly(02. 6 - 07. 8)

1st plasma Achievement (08. 6-7)

Integrated Machine Commissioning

(07. 9 – 08. 5 )

Brief History

Why we need commissioning

1. To verify the performance of integrated systems

2. To identify any defect preventing machine operation

3. To verify the scenario for each commissioning step

4. To prepare the basis for full-dress operation

3

Must-check Item Step Item

1. 1Vacuum Base pressure, He leak rate, Baking, Gas puffing, Discharge cleaning

2. Cryogenic Cool-down

Tube cleanness, Cold leak, Temperature control, Structural displacement, Operational stabilityFlow balance, Thermo-hydraulic analysis

3. BasicSCM Test

Electrical insulation, Current directionSuperconducting transition, Joint resistance

Single SCM Test

TF∙PF current charging and dischargingTF∙PF quench, PF blip operationField measurement, Power supply controllability

IntegratedSCM Test

Coupling effect among coils, Loop voltageField measurement, Change of basic environment

4. Plasma Start-up

Operational scenario, Field null controlTiming, ECH pre-ionization, Diagnostics

4

55

Step Item Target

VacuumBase pressure of VV & CR (Pa)Total leak rate (Pa·m3/s)

5.0x10-5 , 1.0x10-2

1.0x10-6

CryogenicCool-down

Inlet temperature of TFC & PFC (K)Inlet temperature of CTS & VVTS (K)Temperature control (K)

< 5< 60< 50

SCM Test

Electrical insulation (MΩ)Joint Resistance (nΩ)TF current charging (kA)PF current charging (kA)Blip rate (kA/s)BTF(T)

100 5

154

10-100 1.5

Plasma Start-up

Loop voltage (V)ECH power & pulse lengthPlasma current (kA)Plasma duration (ms)

3.5-4 400 kW, 300 ms

100100

Target Parameters

Phase Action ItemStartDate

FinishDate

April May June July August

Vacuum&

Cool-down

Evacuation & Leak Test - 04-02

Cool-down 1st Stage (300K~80K)

04-03 04-20

Cool-down 2nd Stage(80K ~ 20K)

04-21 04-24

Cool-down 3rd Stage (20K~4.5K)

04-25 05-02

SC Magnet& MPS Test

Joint Resistance &Insulation Test

04-30 05-05

TF Coil Test 05-06 05-14

PF Coil Test 05-15 05-27

Integrated Test(TF, PF, ECH, ICRH, Fueling Test)

05-28 06-06

Plasma Experiment

Field Null Measurement 06-01 06-02

Plasma Startup Experiment 06-03 06-13

Plasma Control Optimization 06-14 07-15

Engineering Test& Warm-up

Engineering Test 07-16 07-19

Warm-up (4.5K~250K) 07-20 08-01

Vacuum Commissioning (04-02)

Cool-down (5 K) (04-26)

1st Plasma (06-13)

TF Coil 15 kA, 8 hours (05-12)

Milestones6

Vacuum Pumping: 161 daysCryogenic State: 122 daysSuperconducting State: 84 daysPlasma Operation: 48 days

7

Primary Vacuum History

8

Secondary Vacuum History

9

Temperature History

10

Cold Leak Monitoring

Stress History of TF9 Structure11

Preload Change of CS Structure12

Superconducting Transition13

18.2 K(PF1)

17.9 K (TF) 10 K (PF7U)

10 K(PF7L)

Rcoil (300K) : 957 mΩRcoil (18K) : 4.4 mΩRRR ~ 217

Stainless steel body

Copper block

Cable

(96.5Sn3.0Ag0.5Cu) + (0.12 Sb)

63Sn36.65Pb0.35Sb

E-beam welding

Piston

Coil Lap JointsTotal R

[nΩ]

Average R

[nΩ /joint]

Design

Value

TF 6 11.11 1.85

< 5 nΩ

PF1 7 15.58 2.23

PF2 7 11.09 1.58

PF3 12 20.29 1.69

PF4 12 17.42 1.45

PF5 12 25.15 2.09

PF6 14 11.20 0.80

PF7 8 4.11 0.51

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

PF CLB TF CLB

Vacuum Isolator

OCB Joints

ICB Joints

Current Leads

PF Bus-lines TF Bus-lines

Joint Resistance14

TF Magnet Charging15

PF Magnet Blip Test16

AC Losses17

Measurement Method Shot No. dI/dt[kA/s] Qtot [J] Qhys [mJ/cc] Ntau [ms]

Trapezoidal Pulse

(Calorimetric)

May325 0.5 [0.5-0.5] 867

178.2 < ( 1.3T)

D eff < 13.5 mm

62.5

279 1.0 [1.0-0.5] 1039 62.5

July

1183 0.5 [0.5-0.5] 840 52.6

1184 1.0 [1.0-1.0] 1218 47.2

1185 2.0 [2.0-2.0] 1888 49.1

Measurement Method Shot No. Frequency[Hz] Q/cycle [J/cycle] Qhys [mJ/cc] Ntau [ms]

DC biased Sinusoidal

(Enthalpy)July

1187 0.1 86.5164.6 < ( 0.65T)

D eff < 9 mm

32.0

1190 0.14 98.55 32.4

1188 0.2 119.97 35.8

Trapezoidal current waveformTraditional temperature overshoot by PF coil current pulse

Cryogenic circuit of PF 1 UL coil

• KSTAR design value

- Qhys < 250 mJ/cm3 per 3T

- n < 60 ms

Sinusoidal current waveform

Magnetic Configuration18

Conventional mode- Favorable for initial breakdown due to larger field null- Flux contributions mainly from PF1~4, weakly from PF5~7

Dipole mode - Higher flux for current ramp-up and feedback control- Considerable flux contributions from PF 5 ~7

0.5 1 1.5 2 2.5 3 3.5 4-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

R [m]

Z [

m]

KSTAR Initial Magnetization Flux, o = 0.82497 Vs

1

1

2

2

2

5

5

510

10

1020

20

20

30

30

30

50

50

50

100

100

100

10

0

100

Coil I (kA)1 1.7202 2.1223 2.9294 2.9575 0.8026 0.7357 -0.413

0.5 1 1.5 2 2.5 3 3.5 4-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

R [m]

Z [

m]

KSTAR Initial Magnetization Flux, o = 0.949 Vs

2

2

2

5

10

10

20

20

20

30

30

30

50

50

50

10

0

100

100

Coil I (kA)1 1.9132 3.0773 2.5524 2.0485 1.0006 1.4147 -1.100

Shot 858 Shot 977

Initial flux: 0.825 WbMax. Vloop @ vacuum: 4.4 VNull size (<10 G): 1m (dia.)Bz/dt: -0.1 T/s

Initial flux: 0.949 WbMax. Vloop @ vacuum: 5.1 VNull size (<10 G): 0.5 (dia.)Bz/dt: -0.12 T/s

Shot no. 794

ECH power: ~ 350 kW with perpendicular launch

ECH power on time: t = -30 ms

H2 pre-fill gas pressure: ~ 4.5 x 10-5 mbar

ECH Pre-ionizationR ~ 1.8 m

2nd

harmonic

resonance

position

(Bt = 1.5 T)

R ~ 1.7 m

(a) Shot 794

(b) Shot 977

(c) Shot 1057

• Shot no. 794Conventional modePerpendicular launchEC beam target:Z=0m, R=~1.8 m

•Shot no. 1057Dipole-like modeOblique launch(tor. angle=-10)EC beam target:Z= -0.1m, R=~1.7 m

• Shot no. 977Dipole-like modePerpendicular launchEC beam target:Z= -0.1m, R=~1.7 m

ECH Pre-ionization19

Observation of 2nd Harmonic ECH Pre-ionization

-0.04 -0.03 -0.02 -0.01 0.00 0.01 0.020.0

0.1

0.2

0.3

0.4

-0.04 -0.03 -0.02 -0.01 0.00 0.01 0.02

0

1

2

3

4

5

PE

CH (

MW

)

ECH power

H(

a.u

.)

Time (s)

ha03 ha05

ha07 ha09

ha11 ha12

ha13 ha14

ha15 ha16

Toroidal H signals

Ch#11

Pre-ionized plasma at t=-10ms before the onset

of the toroidal electric field for shot no. 977

R = ~1.7 m

2nd

harmonic

resonance

•Line of sight of toroidal H channel no. 11 is near

the 2nd harm. EC resonance at R ~ 1.7 m

Evidence of 2nd harmonic ECH pre-ionization

Ch #11

EC beam

ECH antenna

20

Plasma Shot Log 21

First Plasma(#794, ‘08. 6. 13) 22

PF Coil Current

Pressure

ECH Power

H-alpha

ECE

Line Density

Plasma Current

Loop Voltage

BTF : 1.5 Tesla

R=1.8 m, a=0.3m

PECH : 350 kW

Line Density : 1x10 19/m2(peak)

Peak loop voltage : 1.93 V @ inboard mid-plane

Plasma Current : 107 kA (peak)

Pulse length : 210 ms

23

(a) #1058, 200 ms

(b) #1058, 372 ms

(c) #1058, 586 ms

ECH turned off at 300 ms

>380 ms with >100kA

Vertical Instability Onset

(a) (b) (c)

±3cm

Ip Feedback Control

Representative Shots 24

Target Results

ECH Pre-ionization Plasma Current > 100 kA Pulse Length > 100 ms

Reliable Pre-ionization by 2nd Harmonic ECH at 84 GHz Max. Plasma Current : 133 kA (shot 976) Max. Pulse Length : 862 ms (shot 1127)

25

Failure Analysis

Total Fault Events: 330 Total Interrupt Time: 164 hr

Summary

1. KSTAR was successfully passed the engineering/plasma commissioning on the first trial. So, the first Nb3Sn technology-based fully superconducting tokamak is newly registered in operating machine entry.

2. KSTAR has achieved the first plasma on June 13 (Fri).After more than 600 breakdown shots, plasma current was ramped up to 133kA with rate of 0.8 MA/s, and well-controlled with duration up to 862 ms.

3. Success keys to overcome from poor technological base and unexperienced man-power are even pain-taking, exhaustive preparation and ceaseless confirmation.

4. KSTAR now plans to upgrade its power supply, plasma facing components, diagnostics and heating devices as quickly and feasibly as possible.

26