29th Symposium on Fusion Technology (SOFT 2016)

P4.007 Final design and prototyping of the SPIDER caesium ovens

8 Sep 2016, 14:20

1h 40m

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

Board: 7

Poster A. Experimental Fusion Devices and Supporting Facilities P4 Poster session

Speaker

Michela De Muri (Consorzio RFX)

Description

The Padova Research on ITER Megavolt Accelerator (PRIMA), under construction at Consorzio RFX, will host SPIDER test bed, a full-size 100 kV negative ion source, and MITICA test bed, a prototype of the whole ITER injector, aiming to develop and optimize the heating injectors to be installed in ITER. The production of hydrogen (or deuterium) negative ions inside the sources relies mainly on the generation on a caesiated surface with a low work function, which enhances the ion yield and reduces the co-extracted electrons. In the SPIDER beam source fresh Cs has to be injected in a controlled way by means of three Cs ovens. Since the Cs ovens are embedded in the source, their design has to assure vacuum and high temperature compatibility, and the remote operation. The design is complicated by the high reactivity of Cs, the difficulty in setting a stable (but adjustable) temperature distribution among the parts under vacuum, and need for the development of a special solenoid valve. The final design, which concludes an initial design and R&D phase, is carried out with the IPP Garching collaboration and the experience gained at ELISE test bed. Specific diagnostics are embedded to measure the Cs vapour flux exiting from the injection nozzle, by means of a Surface Ionization Detector (SID) developed at IPP, and also the amount of Cs in the reservoir, with a level indicator. The procurement of the three ovens is preceded by the setting up of a Cs oven test bed, where a prototype of oven is tested and characterised inside a vacuum chamber. The final design of the oven, also supported by finite element thermal analyses, and the R&D activity on the solenoid valve are presented. The Cs test bed is described and the results of the prototyping activities are given.