Device Parameters of Heliotron J

Coil SystemL=1/M=4 helical coil 0.96MATToroidal coil A 0.6MATToroidal coil B 0.218MATMain vertical coil 0.84MATInner vertical coil 0.48MAT

Major radius 1.2mMinor radius of helical coil 0.28mVacuum chamber 2.1m3

Aspect ratio 7Port 65Magnetic Field 1.5TPulse length 0.5secPitch modulation of helical coil

Inner Vertical Coil

Toroidal Coil A

Outer Vertical Coil

Toroidal Coil BHelical Coil

Plasma

Vacuum Chamber

sin( )

0.4

M M

L L

The Heliotron J Device

Main VFC

TFC-A

TFC-B

Aux.VFC

HFC

Configuration “A” is designed to create a helical divertor region shown in red and yellow.

The position of the plasma is shown relative to the helical conductor and the vacuum vessel

Other configurations

• island divertor

• standard

from T. Mizuuchi, M. Nakasuga et al. Stellararor Workshop 1999

Heliotron-J surfaces: cfg “A” - helical divertor

Magnetic Surface Mapping

Fig.3 The magnetic surfaces at = 67.5 in the standard configuration. (a) The experimental results (corrected) and (b) The calculated magnetic surfaces.

(a) (b)

STD config, 0.03 Tesla, corrected for earth’s field

Electron Cyclotron Heating

• ECH 400kW 53GHZ 50ms

• <> ~ 0.2%, <20% radiated

• some Fe Ti C O impurities

Plans:

• will upgrade to 70GHz, 500kW

• ultimately 4MW ~20kJ?

• impurity control

• explore bumpiness and hel. divertorsFig. 2 Dependence of the diamagnetic stored energy on the magnetic field strength.

B*=0 (T)

Wp (kJ)

#1595 ~ #241653.2GHz ECH

0/

0.80 1.00 1.20 1.400

0.2

0.4

0.6

0.8

1

0.4 0.5 0.6 0.7

W-Diamagnetic vs B is peaked, 700J max