SPIDER Gas injection and Vacuum System: from design to site acceptance test

The ITER project requires at least two Neutral Beam Injectors, each accelerating to 1MV a 40A beam of negative deuterium ions, to deliver to the plasma a power of about 33 MW for one hour as additional heating. Since these requirements have never been experimentally met, it was recognized necessary to build-up a test facility, named PRIMA (Padova Research on ITER Megavolt Accelerator), in Italy, which includes both a full-size negative ion source (SPIDER - Source for Production of Ion of Deuterium Extracted from RF plasma) and a prototype of the whole ITER injector (MITICA - Megavolt ITER Injector & Concept Advancement). This realization is made with the main contribution of the European Union, through Fusion For Energy, the ITER Organization and Consorzio RFX which hosts the Test Facility. SPIDER is a Radio Frequency ion source that has the same characteristics foreseen for the ITER NBI but with beam energy limited to 100 keV. The mission of SPIDER is to increase the understanding of the source operation and to optimize the source performance in terms of extracted current density, current uniformity and duration. The paper describes the Gas injection and Vacuum System (GVS) starting from the analysis of the requirements and going through the detailed design and the procurement of the system up to the site acceptance tests. In particular the rationale behind the main design choices are presented and some manufacturing details of the gas injection plant feeding the RF source is given. Furthermore, the sensor system dedicated to the measurement of the vacuum level, gas pressure and throughput and the residual gas analysis are described considering the interfaces with the PRIMA interlock and safety system. Reference is also made to safety aspects concerning the presence of H2/D2 in a closed environment as the SPIDER bioshield is.