Experimental validation of a molecular flow code with the ARIANNA setup

In the framework of the PRIMA (Padova Research on ITER Megavolt Accelerator) activities, the knowledge of the background gas density distribution in the Neutral Beam components is a very important aspect which plays a role on their performances. The Adaptable Rarefied Instrumented Atmosphere for Neutral iNjection Applications (ARIANNA) experiment has been set up as complementary service in the NBI source modelling activity. It reproduces the layout of a typical beam source, in which ion source and grids are integrated. ARIANNA supported the development and validation of the AVOCADO code [1], which has been created to simulate molecular flow and density gas distribution in three-dimensional geometry by view factor technique. The validation activity was aimed at demonstrating the capability to correlate the mass flow to the pressure difference, the correctness of the pressure distribution in the volume. This paper presents the ARIANNA experimental setup and the subsystems involved in the vacuum production and measurement and compare the AVOCADO code simulation results obtained modeling the ARIANNA device, with the experimental data.