Electron cyclotron heating assisted startup in JT-60U

Abstract

Electron cyclotron heating (ECH)-assisted startup experiments have been performed in JT-60U. The breakdown loop voltage was successfully reduced from 25 to 4 V (=0.26 V m−1) by 200 kW ECH. This is lower than the 0.3 V m−1, which corresponds to the maximum electric field in ITER. Parameter scans of ECH power, prefill pressure, resonance position and polarization were carried out. The sensitivity of the breakdown to polarization and resonance position was observed. A prefilling gas pressure scan showed that the initial breakdown density increases with prefill pressure when it is is lower than 8 × 10−5 Torr. Higher harmonic ECH was also attempted. The second harmonic ECH-assisted startup was possible with higher ECH power injection. However, the third harmonic ECH-assisted startup was not successful.

Electron cyclotron heating during ECRH-assisted pre-ionization in a tokamak

“…where ℘ is the Weierstrass function and the invariants are given by g 2 = 13C 2 and g 3 = 2C 3 + 4ε 4 . Here, Γ 0 is any root of −Γ 4 + 2CΓ 2 + 2Γε 2 −C 2 = 0 and Γ(t 0 ) = Γ 0 .…”

RF heated wall conditioning discharges in JT-60U

“…The following experimental plasma was successfully started up with 0.5 V/m of ohmic electric field. While this startup condition is slightly higher than that required for ITER, 0.3 V/ m, ECH start-up with 0.26 V/m has been obtained with low ECH power, P ECRF = 0.4 MW in JT-60U [12]. Therefore that the wall recovery by the ECH wall conditioning discharge is a promising technique for the fusion reactors.…”

Development of a dual frequency (110/138 GHz) gyrotron for JT-60SA and its extension to an oscillation at 82 GHz

“…Since the CS coil of JT-60SA is also super-conducting coil, the available flux is limited and ECH assist will be required in many experiments. In this purpose, the fundamental harmonic waves are more effective than the second harmonic waves to reduce the required ECH power [18].…”