24pD35P
Upgrade of 70 GHz ECRH/ECCD system for the Heliotron J Device
N. Inklin1, K. Nagasaki2, K. Sakamoto2, H. Kishikawa1, G. M. Weir2, H. Okada2,T. Minami2, S. Kado2, S. Kobayashi2, S. Yamamoto2, S. Ohshima2 , K. Masuda2, K. Hada1,
N. Kenmochi1,Y. Ohtani1, X. Lu1, S. Konoshima2, Y. Nakamura2,and T. Mizuuchi2
GSES, Kyoto University, 2IAE, Kyoto University

Electron cyclotron resonant heating and current
drive (ECRH/ECCD) is one of the efficient heatingmethods in fusion plasma experiment. In theHeliotron J device, a collector potential depression(CPD) type gyrotron at 70 GHz manufactured by
GYCOM and a new power supply manufactured by
Nisshin Pulse Electronics Co. has been recently
introduced in order to extend operation capability
for the plasma experiment. The objective of thisresearch is to optimize the gyrotron operation andfind the stable operation regime for plasma physics
experiments.
Gyrotron and power supply
Main specification of the RF output at thegyrotron window is listed in Table 1. The DC
voltages up to -57 kV and +22 kV are supplied tocathode and body, respectively. This operation
condition is different from a gyrotron operation test
at GYCOM, -50kV and +30kV, which may be dueto the difference of magnetic field distribution incryomagnet. The available maximum power at
gyrotron window is 514 kW at Ibeam=26 A, Ibody = 26mA.
A high-voltage power supply has also been
upgraded in order to extend the operation capability.
Table 2 shows the main features of the power
supply. The double-pulse injection is possible in aplasma shot, and the gyrotron output power can bemodulated up to 100% at 10 kHz by either beam
voltage or body voltage. Since a capacitor bank isused, lower cathode voltage makes the pulse length
longer, 250 msec.

Transmission line and launcher
A matching optics unit (MOU) is connectedwith the gyrotron window in order to couple theGaussian beam to the HE11 waveguide mode withhigh efficiency. The measured power loss at theMOU is 15 %. The HE11 mode is transmitted by 2.5
inch oversized corrugate waveguides of around 20
meters long including three miter bends, a polarizer,a power monitor and a waveguide switch. The
measured transmission efficiency is 87%. The
transmitted waves are injected into the Heliotron J
vacuum chamber through a barrier window, and alaunching system with a focusing mirror and asteerable flat mirror.

ECRH Operation
After the system is completed, an operation
power map was taken. The body voltage/magnetic
field dependence are shown by Fig.2 and 3
respectively. The maximum injection power is 360
kW. The ECRH/ECCD system has been routinely
operated for plasma production, heating and current
drive since last August in the Heliotron J device.
400350

Output power(kW)16.10.2015

300

Vbeam = 57 kV
Ibeam = 26 A
Icoll. = 0.93 A

250
200
150

10 ms pulse
Series resistor
150x 3Toshiba water load
6.5 l/min

100
50010152025

Body voltage (kV)Fig. 2 Body voltage dependence of gyrotron
power after transmission.

Table 1 Gyrotron specification.

Output power(kW)

400

350

6.10.2015
Vbeam = 57 kV
Icoll. = 0.93 A
10 ms pulse
Series resistor
150x 3Toshiba water load
6.5 l/min

Vbody = 20 kV
Vbody = 19 kVVbody = 18 kV
Vbody = 17 kV

250

200
2.70

Table 2 Power supply specification.

Vbody = 21 kV

300

2.71

2.72

2.73

2.74

2.75

2.76

Magnetic field (T)Fig. 3 Magnetic field dependence of gyrotron
output power after transmission.

0