29th Symposium on Fusion Technology (SOFT 2016)

P2.019 Conceptual design of the JT-60SA pellet launching system

6 Sep 2016, 14:20

1h 40m

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

Board: 19

Poster A. Experimental Fusion Devices and Supporting Facilities P2 Poster session

Speaker

Peter Lang (Tokamak Scenario Development Division (E 1))

Description

A conceptual design for a pellet injection system will be worked out, capable to support key missions of the new tokamak device JT-60SA. For exploitations in view of ITER and to resolve key physics and engineering issues for DEMO, several tasks were assigned to this system. Physics investigations aim at operation at high density in ITER and DEMO relevant plasma regime above Greenwald density, power exhaust techniques with radiation layers, particle balance studies, and ELM control and mitigation. The postulated engineering requirement is to quantify pellet actuation on electron density for application within the advanced real-time control scheme by controlling density gradients. Our intended pellet system comprises three major components: pellet source, accelerator and guiding system. The guiding system must be installed inside the torus vessel already under construction, hence still possible launch geometry were pursued first. Three different options have been identified: inboard, outboard and top launch. The first one is most promising with respect to fuelling performance but will impose pellet speed restrictions to about 470 m/s for adequate pellet sizes. Both others offer headroom for significantly higher injection speed but under less favourable physics boundary conditions. In order to evaluate expected performances for all relevant plasma scenarios, detailed modelling efforts for every launch geometry option are in progress. For a suitable pellet source covering all requirements, several options are at hand including commercial providers. For the accelerator, the high speed option up to about 4000 m/s could be covered by a multi stage gas gun. Single stage gas guns and centrifuges can cover the speed range up to about 1000 m/s for the basic work load since both fulfil the requirements for pellet size and speed. Due to a to higher speed precision resulting in less timing jitter, a centrifuge would be better suited for control requirements.