29th Symposium on Fusion Technology (SOFT 2016)

P1.033 Electron cyclotron stray radiation detection and machine protection system proposal for JT-60SA

5 Sep 2016, 14:20

1h 40m

Foyer 2A (2nd floor), 3A (3rd floor) (Prague Congress Centre)

Board: 33

Poster B. Plasma Heating and Current Drive P1 Poster session

Speaker

Alessandro Moro (Istituto di Fisica del Plasma "Piero Caldirola" IFP-CNR)

Description

The JT-60SA tokamak is scheduled to start operations in 2019 to support the ITER experimental programme and to provide key information for the design of DEMO scenarios. The device will count on ECRH and NBI as auxiliary heating and EC operations are foreseen for EC assisted startup, EC Wall Cleaning (ECWC), bulk heating and current drive and MHD control, for example. 7 MW of total injected EC power will be available at operating frequencies: 82 GHz, 110 GHz and 138 GHz. Potentially dangerous situations that could harm tokamak structures during operations characterized by low absorption and therefore high levels of EC stray radiation cannot be a priori excluded. An estimation of the wall load under direct beam exposure and during plasma operations such as assisted breakdown, ECWC and main heating phase will be given, determined from the EC antenna main characteristics and launching geometry. A system to minimize the risk of damage to machine components would rely primarily on fast detectors to monitor the level of stray radiation at accessible (ex-vessel) lines of sight,  like those provided by vacuum windows. Pyrodetectors may be suitable to monitor the fast changes in stray level, with the additional advantages of small dimensions and low volume occupation, allowing easy mounting in the proximity of windows. Though no solution could grant complete elimination of risks, local information only with in-situ detector is nevertheless beneficial, and the analysis performed aims to determine suitable positions of fast detectors and probes in the vicinity of ECRH launchers and of potentially critical beam trajectories. A proposal for the system conceptual design for JT-60SA is presented and an example of the time response and potential benefits of such a system will be given, based on experience gained on the TCV tokamak during ECWC experiments performed in preparation of JT-60SA operations.