Physics and engineering design of the accelerator and electron dump for SPIDER

Abstract

The ITER Neutral Beam Test Facility (PRIMA) is planned to be built at Consorzio RFX (Padova, Italy). PRIMA includes two experimental devices: a full size ion source with low voltage extraction called SPIDER and a full size neutral beam injector at full beam power called MITICA. SPIDER is the first experimental device to be built and operated, aiming at testing the extraction of a negative ion beam (made of H − and in a later stage D − ions) from an ITER size ion source. The main requirements of this experiment are a H − / D − extracted current density larger than 355 / 285 A m −2 , an energy of 100 keV and a pulse duration of up to 3600 s. Several analytical and numerical codes have been used for the design optimization process, some of which are commercial codes, while some others were developed ad hoc. The codes are used to simulate the electrical fields (SLACCAD, BYPO, OPERA), the magnetic fields (OPERA, ANSYS, COMSOL, PERMAG), the beam aiming (OPERA, IRES), the pressure inside the accelerator (CONDUCT, STRIP), the stripping reactions and transmitted/dumped power (EAMCC), the operating temperature, stress and deformations (ALIGN, ANSYS) and the heat loads on the electron dump (EDAC, BACKSCAT). An integrated approach, taking into consideration at the same time physics and engineering aspects, has been adopted all along the design process. Particular care has been taken in investigating the many interactions between physics and engineering aspects of the experiment. According to the "robust design" philosophy, a comprehensive set of sensitivity analyses was performed, in order to investigate the influence of the design choices to the most relevant operating parameters. The design of the SPIDER accelerator, here described, has been developed in order to satisfy with reasonable margin all the requirements given by ITER, from the physics and engineering points of view. In particular, a new approach to the compensation of unwanted beam deflections inside the accelerator and a new concept for the Electron Dump have been introduced.

Simulation of the gas density distribution in the large vacuum system of a fusion-relevant particle accelerator at different scales

“…4 shows the model, which reproduces the geometry described in Ref. [2]. The domain sizes are 22 Â 22 Â 105 mm, and Kn ¼ 3 ÷ 6 is calculated within this flow region.…”

“…SPIDER is presently under construction, and the experimental activities are expected to start in 2016. The SPIDER accelerator was designed to satisfy the physics and engineering requirements of the ITER Heating Neutral Beam Injector [2]: an extracted current density greater than 355/285 A m À2 for H À /D À ions respectively, an ion beam energy of 100 keV, and a pulse duration up to 3600 s. As shown in Fig. 1, the SPIDER Beam Source (BS) is contained in a Vacuum Vessel (VV), which contains also a beam dump and a diagnostic calorimeter to stop the ion beam.…”

Development of versatile multiaperture negative ion sources

“…Negative ion sources [1,2,3] are a fundamental component of Neutral Beam Injectors (NBI) [4,5,6,7,8,9], which contribute most of the additional plasma heating and current drive to the International Tokamak Experimental Reactor (ITER) project and which need to be strongly optimized in the perspective of the more demanding DEMO reactor [10]. A relatively compact radiofrequency (rf) ion source, named NIO1 (Negative Ion Optimization phase 1) is being developed and tested in Padua, Italy, in collaboration bewteen Consorzio RFX and INFN [11], in the framework of the accompanying activities in support to the ITER NBI test facility and to the Megavolt ITer Injector Concept Advancement (MITICA) [8], to provide a test bench for source optimizations.…”

Benchmark of the SLACCAD code against data from the MANITU testbed at IPP

“…In the framework of the support activities for the ITER NBIs, the PRIMA test facility, which includes a RF-driven source with 100 keV accelerator (SPIDER) and a complete 1 MeV Neutral Beam system (MITICA), is under construction at Consorzio RFX in Padova [6,7].…”