T. S. Kim and S. H. Jeong Korea Atomic Energy Research ...psl.postech.ac.kr/kjw16/talks/Na.pdf · National Fusion Research Institute, Daejeon, Korea. T. S. Kim and S. H. Jeong. Korea

B. Na, J. H. Jeong, S. W. Jung, S. J. Wang, J. G. Kwak, Y. S. Kim, and NBI TeamNational Fusion Research Institute, Daejeon, Korea

T. S. Kim and S. H. JeongKorea Atomic Energy Research Institute, Daejeon, Korea

1

KJ workshop 2016 W @Pohang, Korea

NBI-1 has been major heating source for KSTAR operation

2

• 1 beam box with three ion sources• 100 keV, D+ based arc discharge/ion sources• placed in horizontal mid-plane On-axis CD profile

No. 3 (2014)

No. 1 (2010)

No. 2 (2012)

SECONDBeam Line

Long pulse capable positive ion based ion source & multi-aperture plasma grid with CuCrZr

3 1 2

KSTAR for high Beta & steady-state operation

3

• Main mission of KSTAR is to achieve “Advanced Tokamak (AT)” operation mode in long pulse capable superconducting tokamak device

High β & Steady-state operation (fully non-inductive CD)• Basically target to high betaN, steady-state

– Increased power and off-axis current drive• Approach to high betaT & low q95

– For broad q profile with larger IP operation

• Approach to high betaP & q95 – Stable operation with high BT operation

(2016)

4

Off-axis CD for advanced tokamak mode

• One approach to AT mode is utilizing bootstrap current.• Additional off-axis CD provides more flexible, localized control of current

profile.• Current profile is controlled by the angle between NBI and magnetic field pitch

angle.

M. Murakami et al., NF 49, 065031 (2009).

New tangential NBI having off-axis CD capability

5

Advantages– maximizing driving current– maximizing/optimizing off-axis CD capability– compromise with installation constraints– minimizing additional R&D requirements

vertical slant angle

tangential radius

Specification of NBI2

Beam energy <100 keV

Beam power <6 MW

Duration <300 sec

Tangential radius 1.6m

Vertical slant angle 0, +/- 5.5°

Vertical slant angle determines off-axis capability

6

• At lower angle, optimum Rtmoves to higher radius

• At higher angle, off-axis characteristics are enhanced, however efficiency decreases

• Angle 7.5 degrees seems to be better for CD, however absorption decreases

• At lower angle (5.5 deg), absorption increases

• Engineering limit ~ 5.5 deg.

vertical slant angle scan for up-looking beam

Idrv

Pabs/Pb

rhopeak

rhow

Accident on ion dump in 2016 campaign

• Surface metal of full energy ion dump melted.• Even though TC array is installed, the failure was not alarmed.• Sudden change of surface metal may not be detected.

Heat load calculation using BTR code

8

Specifications Remarks

Beam energy 100 keV

Injected neutral beam

power>6 ㎿ = 2.0 ㎿ × 3 ea

Number of Ion sources 3 EA

Beam target position, (Rt) 1.6 m

Vertical slant angle 5.5°

Beam size 450 ㎜ × 130㎜

Beam input port H port

<NBI-2 specifications>

( No. of beamlets: 28×10 )

450 mm

130m

m

< Size of ion source for the NBI-2 >Beam energy 100 keV

Beam current 60 A

No. of Beamlets 28 × 10

No. of Focal beamlets 8×3

Focal position(m) 10

Beam power@12m(In Tokamak)(MW) 5.5

Transmission rate(%) 90.9

• BTR code calculation results without beamline components

• The goal of the BTR calculation- Neutral beam transport, loss and

ionization calculation- Heat load calculation of beam line

components by collision of neutron or ion particles

BTR calculation with beam line components-II

9

Full energy Half energy 1/3 energy

Total loaded beam power(MW)

2.134 0.134 0.081

Peak power density(MW/m2)

6.716 0.674 1.619

<Full energy> <Half energy> <1/3 energy>

single beam

Full energy

Total loaded beam power(MW) 6.402

Peak power density(MW/m2) 6.716

<Full energy>

three beams

• The cooling capacity of hypervapotron is satisfied ( <10MW/m2).

• The margin is not enough• Heat load on a calorimeter: 6.49

MW/m2

Improvement of ion dump-I

• IR camera will be installed to monitor front surface temperature in real-time– Camera with alarm system partially replaces TC arrays at the back of target – Two cameras will see both full and half energy dump for feasibility study (harsh

environment – unstable temperature, electric noise, neutron, magnetic field)

Improvement of ion dump-II

• Energy recovery ion dump is being studied– Reducing thermal load– Increasing power efficiency

Ion beam trajectory not inducing depression electric potential

Ion beam trajectory inducing depression electric potential

Bending magnet

Plas

ma

HH + H+

H+

Acceleration grid

Neutralizer

Ion dump

50kV

50kV

0kV

0kV

0kV

0kV

Improvement of full energy beam fraction

Preparing a full energy fraction measurement system. Doppler shift of D-alpha

E

E

H

H

II

Cn

n

,

/,

α

α 221=

+1

+2

∑l lEl

l lEl

AF

AFC *

/,

*,

221

∑=

IS-B 90kV

θλλ coscv

00 =∆

* S. J. Yoo et al., RSI 71, 1421 (2000).24

fullhalfthird

E=0

Summary

13

• Main mission of KSTAR is steady state high beta AT mode operation.• Off-axis CD provides AT operation and more controllability of current

profile.• The effect of slant angle on heating and CD is calculated, but 5.5 degree

is determined by engineering limit.• Heat loads on beam components satisfy the heat capability of

hypervapotron.• Ion dump temperature measurement system is under consideration.• Ion energy recovery system and full energy beam fraction are being

studied.

14

Thank you for your attention!Inquiry/feedback: [email protected]