Characterization of the SPIDER Cs oven prototype in the CAesium Test Stand for the ITER HNB negative ion sources

Abstract

The ITER Heating Neutral Beam (HNB) injector is required to deliver 16.7 MW of power to the plasma from a neutralized beam of H−/D− negative ions, produced by an RF source and accelerated up to 1 MeV. To enhance the H−/D− production, Cs will be routinely evaporated in the source by means of specific ovens embedded in the source, to reduce its work function. Controlling and monitoring the evaporation rate of Cs inside the source will be fundamental to achieve the desired performance for the ITER HNB.The prototype RF negative ion source SPIDER has been developed and built in the Neutral Beam Test Facility at Consorzio RFX. In SPIDER, liquid Cs based ovens will be used to inject Cs vapors inside the source. The CAesium Test Stand (CATS) has been specifically designed and set up for testing, commissioning, and characterizing Cs ovens in vacuum, but also to study the Cs evaporation and deposition onto surfaces. A SPIDER Cs oven prototype has been manufactured and tested in CATS in order to characterize its thermal behavior, by means of thermocouples and thermal camera, and its Cs flux, by means of Surface Ionization Detectors and Laser Absorption Spectroscopy.