Experimental characterization of the gas injection nozzle for the ITER Neutral Beam Test Facility neutralizer

The gas supply for the neutralizer of the Heating Neutral Beam is designed to guarantee the establishment of the gas cloud needed to neutralize the negative ion beam, generated in the beam source, before it can be injected into the tokamak for plasma heating. To guarantee the proper function for optimal beam properties, an experimental validation of the analytical predictions of the gas flow behavior under the conditions of the test facility MITICA (Megavolt ITER Injector and Concept Advancement) was needed. Herewith the throughput properties of the designed gas injection nozzles had to be investigated as well as the behavior of the system in case of a sudden shutdown of the supply. These experiments have been performed at the modified TransFlow facility at KIT. Additionally, the experimental results have been compared with simulations and some effort was spent in order to find proper material and mounting options for the nozzles.