Auxiliary Plant – Heating

JT-60SA will use up to 34 MW of neutral beam (NB) heating and up to 7 MW of electron cyclotron resonance heating (ECRH). The upgraded NBI system (below) for JT-60SA consists of twelve positive-ion-based NBI (P-NBI) units and one negative-ion-based NBI (N-NBI) unit. The P-NBI units control deposition profile and plasma rotation. The P-NBI system has been modified from that of JT-60U in order to extend the pulse duration from 10s to 100s keeping the same injection power. High power N-NBI is also required to provide sufficient NB current drive capability for high beta steady-state (full non-inductively driven) plasma development.

Neutral Beam Injection System

High power N-NBI also contributes to heating of the central region in high density plasmas with a dominant electron heating fraction, which is relevant to ITER and DEMO plasmas heated by alpha particles. The beam line of the co-tangential N-NBI unit is offset downward from the equatorial plane by ~0.6 m to drive off-axis plasma current, and hence to produce reversed shear with a high bootstrap current fraction.

The main modification from JT-60U has been the upgrade of the power supply system and magnetic shield system for suppressing the stray magnetic field in the beam line from the JT-60SA tokamak. In addition, the negative ion source has been modified to improve performance such as the negative ion production and acceleration.

The ECRH system (shown below) will generate or sustain high performance plasmas, provide assistance to plasma start-up, and provide cleaning of the first wall of the vacuum vessel. It is composed of 110GHz systems, basically similar to the JT-60U ECRF system. However the maximum pulse duration of 100 s is much longer than the 5 s required in JT-60U. In the initial research phase 2 gyrotrons from JT-60U will run with two new gyrotrons, capable of 100s operation, provided by JA, with power supplies provided by EU. These 4 units will then be upgraded to nine for extended pulse duration.

Electron Cyclotron Resonance Heating
NBI+ECRH system