We have assumed that the near-ICRF field exist only in the box shape region in front of the antenna. The vol-

§7. ICRF Heating of LHD Plasma Using Res- onace Layers in Front of ICRF Antenna

Watanabe, T., Kumazawa, R., Saito, K., Seki, T., Mutoh, T., Watari, T.

The long pulse JCRF' discharge experiments was carried out in the 6th cycle campaign of LHD. We have tried to reproduce this long pulse ICRF discharge by the com- puter analysis and have explored conditions for high per- formance ICRF long pulse discharge in the 8th campaign of L HD experiments.

We have assumed that the near-ICRF field exist only in the box shape region in front of the antenna. The vol-

Ull1C of the box is estimated as VI' f = H x D x D /2 where H( = 1m) and D( = O.3m) correspond to the height and width of the ICRF antenna. This near-ICRF field accel- erates protons at ion cyclotron resonance layers. Colli- sionless proton orbits are calculated llumerically in the LHD magnetic configuration with ICRF electric field.

Initial positions of particle orbit are distributed uni- formly in the box of near-jerf field, which is placed at the front of the ICRF antenna and is curving along t.he last.

closed magnetic surface. Initial energy of proton is set as 2 keY that corresponds to the thermal energy of plasma.

Effects of Coulomb collision are dealt with as pel~turba­

tion. Absorbed rf electric power in plasma are estimated by a linear calculation. The accelerated proton can be classified into two groups. One is the group of non-loss protons, which keep being sustained in magnet.ic snrface region. Another is the group of loss protons, which reach vacuum vessel during the orbit.s calculation. The energy of non-loss particle is a.<;snmed to be converted directly to the thermal energy of plasma. Example of numerical calculation are shown ill Fig.I and in Fig.2,

The energy balance of the plaorna sustained by ICRF alone is analyzed. 'We have assumed that plasma is com- posed of electrons (density= N _{e ):} ions (~ensity = ]\li,

charge = z) and protons (density = N

_{p ).}

Temperatures of these components are assumec! to be equal (= T).

f..iloreover

^l

density and temperature are assumed to be uniform in a magnetic surface region.

The energy confinement time: IE: is expressed by the multiplication factor H to liss95: IE = H X liss95 . Nu- merical exainple of scaling law of the pla.<.;nuL sustained by ICRF alone is shown in Fig.3 The computer analysis result lead the following conclusion.

1) The ICRF power absorption in the resouauce lay-er in front of the antenna can sustain the LHD plasma. Core plasma. heating is realized at that time.

2) As for the resonance magnetic field, the saddle type configuration is more efficient for high energetic proton confinement than the magnetic a..xis configuration.

3) High z (Ar) plaEllla with minority H will be promising for long pulse ICRF discharge because of less heat load brought by high energetic protons.

~ 100

<

"

>

<

w

Z <0

N

IOUil~~llU~llh~~ll6~~llh~~lllO~~~I~' T (MSEC)

Fig.I: Change in particle number anrl mean energy by ICR.F heating

leRF HEATED PARTICLES AT THE FRONT OF ANTENNA

<p=1tI2

Fig.2: Poincare plot of IeEF heated protons. The magnetic sur~

face structure is also shown

leRF HEATING IN LHO : RAX

=

3.6 M, SAX'" 2.75 T, SP1CRF = 0.5 MW, ( NHe I NAVR -0.4 . Np I NAVR :0.2. 8,es,,2.5 T, ERF,,20 KV f M, T MAXw12.43 MSEC )

J.

2.

0 ~ - l ^'I' -1

5~ !

tEl '15595" 5

I -l

>

_{tE' t lSS95 = 4}

o~ ^- " " " I . ~

5l

^{~ Q}

^r:r! I

^tlss95

^{= J} _~

or

^{) ' tlsS9s=2 /}

₁

t

I.

o. 5 05 1.0 1.5 2.0 2.5 3.0

NAVR ( M-

J )

x 10-19

Fig.3: Scaling law of plasma sustained by rCRF alone (He plasma)

183