6th US-PRC Magnetic Fusion Collaboration WorkshopSan Diego, July 10-12, 2012

Wandong Liu, on behalf of KTX team

School of Physical Sciences University of Science and Technology of China

Physics Rationale and Engineering Design of Keda Torus eXperiment

– Institute of plasma physics – South western institute of physics– Huazhong University of Science and Technology

– University of Wisconsin at Madison, U.S.– Consorzio RFX, Padova, Italy– Kyoto Institute of Technology, Japan– University of California Los Angles, U.S.– University of Saskatchewan, Canada

Collaboration with：

A new RFP program started in China

The new reversed field pinch（RFP） program in China, Keda Torus eXperiment （KTX）officiallystarted by the Ministry of Science and Technology, in the framework of the ITER domestic program

The duration of the program is 3 years, starting from the end of last year for design and construction of the machine (2012-2014)

The University of Science and Technology of China (USTC) will provide a new building to accommodate KTX device

Reversed Field Pinch: an important alternate toroidal concept

Tokamak RFP

Three major configuration of MCFStellarator: magnetic field is generated totally by the external coils

Tokamak: magnetic field is generated primarily by the external coils

RFP: magnetic field is generated primarily by the plasma current

Main advantages of Reversed Field PinchSmall externally applied field:

the use of normal magnets, high engineering beta, high mass-power-density, efficient assembly

Large plasma current density: Ohmic heating for a burning plasma

Fascinating phenomena of self-organization and nonlinear plasma physics:test bed for the understanding derived at high field, good platform to investigate the transport, link between the fusion energy science and astrophysics

Diversified fusion research recovered

TokamakHL-2A @ SWIP

TokamakJ-TEXT@HUST

Spherical TokamakSUNIT @ THU

TokamakEAST & HT-7 @ IPP

ChengduWuhan

Beijing

4 tokamaks (EAST/HT-7/HL-2A/J-TEXT)a small spherical tokamak (SUNIST)a reversed field pinch (KTX)

RFP KTX @ USTC

Hefei

The former RFP research in China

Construction from 1985 running from 1989Shutdown in 1997

R=0.48m, a=0.1mair core

Al shell: d=1cmstainless steel liner: d=0.4mm

plasma pulse < 2ms, Ip~150kA(max)Te~100eV

The first RFP device in China :SWIP-RFP

Present RFP experiments

RFX-Mod (Italy)R/a = 2 m / 0.46 m

MST (UW-Madison)R/a = 1.5 m / 0.5m

Extrap-T2R (Sweden)R/a = 1.24 m / 0.18m

RELAX (Japan)R/a = 0.5 m / 0.25m

RFX-Mod @ Italy• plasma current~2MA, the biggest RFP device, active

feedback control, high current operationMST @ U.S.

• plasma current ~0.8MA, current drive & confinement improvement

Extrap-T2R @ Sweden• active feedback control of the MHD modes

Relax @ Japan • small aspect ratio R/a~2

MST: improved confinement achieved via modification of the current profile

RFX: self-organized Single Helical Axis state come with electron transport barriers

Recent achievements in RFP

Keda Torus eXperiment (KTX) in USTC

In USTC, we have kept fusion research, small-scale but steadily growing, for almost forty years– tokamak physics and diagnostic– fundamental research in small devices: magnetic reconnection experiment,

chaos, turbulence…– space plasma research: data analysis and numerical simulation of

reconnection phenomena…– theory and numerical simulation: tearing mode, kink mode

RFP naturally fits our current status– the diversity of Chinese fusion research

• KTX will not only address the relative important scientific issues of Tokamak, but also improve the understanding of toroidal confinement in general

– the richness of physics: dynamo, magnetic self organization, RWM– training of fusion talents is the priority of university

• The easy operation, compared with Tokamak; daily running

The KTX project is a nature extension of China MCF program!

Main parameters of KTX

Major radius 1.4 m

Minor radius 0.4 m

Thickness of vacuum shell (SS) 6 mm (τ ~ 2ms)

Thickness of conductive shell (copper) 1.5 mm (τ ~ 20ms)

Plasma current 0.5MA (Phase I), 1.0 MA (Phase II)

Pulse length 30 ms (Phase I), 100 ms (Phase II)

Loop voltage 10～50 V

Plasma inductance ～ 4 μH

Total magnetic flux 3 ~ 5 V٠S

Electron temperature 600 ～ 800 eV

Plasma density ～1019 m-3

Maximum toroidal field 7000 Gauss

Ohmic Coil

Equilibrium Coil

Toroidal Coil

The structure of KTX

KTX has modular shell structureThin simple modular shell structure: thin stainless steel shell(6mm thick, 2ms penetration time) and copper shell (1.5mm, 20ms)– close proximity to the plasma– available active controls, e.g., MHD or PPCD & OFCD – potential research for advanced plasma-facing materials, e.g., lithium

Double-C structure– ensure an excellent accessibility to the internal space

Copper shell

vertical gaps

horizontal gapStainless steel shell

vertical gaps

0 1J rB a

α

μ λ⎡ ⎤⎛ ⎞= = −⎢ ⎥⎜ ⎟

⎝ ⎠⎢ ⎥⎣ ⎦

The modeling of KTX performance

collaborated with Prof. John Sarff

500 kA ramped mode

Simplified electrical circuit model

z zW V I V I Pt θ θ Ω

∂= + −

∂

Current profile: Alpha model

Design for KTX Ohmic coils

Ohmic coils are grouped into 8 sections. The parameters of ohmic coils are optimized to minimize the stray field in the chamber.

contributed by Binjia Xiao & EAST team

The parameters of Ohmic coils

The mutual inductance of Ohmic coils

Design for equilibrium of KTX

Similar to the configuration of RFX, the equilibrium coils of KTX are divided into eight sections, which connect to the corresponding Ohmic coil sections in parallel.

contributed by Binjia Xiao & EAST team

The parameters of equilibrium coils

Design of power supplies (capacitor banks)

Power supply for the toroidal coils

The current waveforms

C1

40k V3m F

C2

15k V50u F

TFcoil_L12m H

TFcoil_R

150m Ohm

D1

TF Coil

C3

450 V1 F

TH1TH2

C1

50k V1.2m F

Loh18.4m H

M96u H

Lplasma3.4u H

Rplasma30u Ohm

D2 Roh9.2m Ohm

C26m F

25k V

TH1

D3

C3

5k V0.15 F

D1

Power supply for the Ohmic coils

contributed by Dr. Peng Fu & EAST team

Design of KTX machine

Fully design for KTX machine, global shape, vacuum chamber, supporting structure, assembly strategy, analysis…contributed by Dr. Yuntao Song & EAST team

KTX Schedule

Laboratory building and KTX hall

30×20×16m3

KTX is open for international collaboration

Madison, July 2010

2010 Oct, USTCRFX, April 2010

June 2011, USTC

SummaryThe features of KTX:– thin simple modular shell structure: good proximity, possible

plasma facing material research, easy active control, for PPCD & OFCD research; for single helicity mode research …

– double C structure for easy accessibility– capacity for tokamak operation (low toroidal B and q value)

The mission of KTX:– contribute to the development of the RFP fusion concept– contribute to fusion science and to explore the similarity (or

contrast) to the tokamak configuration– general plasma science (dynamo, reconnection, …)– education and training of fusion scientists

Future of KTX in USTC天时（right time）

– ITER era

地利（right place）

– USTC, Hefei, Center for MCF research in China

人和（ harmonic human environment）

– Support from international RFP community and Chinese MCF community

Conclusion: KTX must have a bright future

Thanks, and Welcome to USTC!