Experimental Validation of the 3-D Molecular Flow Code AVOCADO

In the framework of the activities for Padova Research on ITER Megavolt Accelerator (PRIMA), the knowledge of the background gas density distribution in the neutral beam components is a very important aspect, which plays a role in their performances. The adaptable rarefied instrumented atmosphere for neutral injection applications (ARIANNA) experiment has been set up as a complementary service for the modeling activity of the ion beam source for the neutral beam injector. It reproduces the layout of a typical beam source, in which the ion source and grids are integrated. ARIANNA supported the development and validation of the AVOCADO code, which has been created to simulate molecular flow and density gas distribution in 3-D geometry by view factor technique. The validation activity was aimed at demonstrating the capability to correlate the mass flow to the pressure difference, and 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 compares AVOCADO results obtained, while modeling the ARIANNA device with the experimental data.