Plasma experiments using a new 170 GHz EC system and a simple model for plasma production on the TRIAM-1M

An electron cyclotron heating (ECH) system has been installed on the TRIAM-1M tokamak, which produces a 170 GHx microwave up to 260 kW at the window of the gyrotron for 5 sec. After the Matching Optical Unit (MOU) converts the microwave to a Gaussian beam, a microwave power of 200 kW is transmitted by a corrugated wave-guide of 63.5 mm in diameter. Tests confirmed these specifications, and the fundamental ordinary electron cyclotron (EC) wave of 170 GHz up to 120 kW was injected into the vacuum vessel of the TRIAM-1M in order to ionize neutral hydrogen gas to make source plasma, which is expected to reduce flux consumption in the case of current start-up by means of Ohmic heating (OH) coils. Though the breakdown does not occur at the input RF power, PRF = 40 kW with the neutral gas pressure, p 1.3 x 10-3 Pa, high-density plasma (more than 0.7 x 1019 m-3) is produced at PRF = 100 kW. In the range of PRF = 40-100 kW, the electron density is proportional to PRF. (author)