Wall Recycling on the Superconducting Tokamak TRIAM-1M

Abstract

The study of wall recycling of long duration discharge has been carried out using 2.45 GHz and 8.2 GHz lower hybrid current drive in the superconducting tokamak TRIAM-1M. The recycling coefficient increases with two time constants. One is 1˜3 s and the other is ˜30 s. These two time constants are common to low (˜2 × 10¹⁸ m^-3) and high (˜1 × 10¹⁹ m^-3) density discharges. In the ultra-long discharge, the wall repeats a process of being saturated and refreshed. One possible candidate of the mechanism of wall refreshment is co-deposition of in vessel element (i.e. Molybdenum). In the high density discharge, the wall becomes saturated and the discharge is terminated due to the density increase. The achievable discharge duration becomes shorter as the plasma density is higher.