Abstract
Typical high-energy negative ion electrostatic accelerators such as the ones designed for fusion applications produce a significant amount of secondary particles. These particles may originate from coextracted electrons, which flow from the ion source, impacting the accelerator grids or as by-products of collisions between accelerated negative ions and the residual background gas, in the accelerator. Secondary emission particles may carry a non-negligible power and consequently must be precisely studied. The electrostatic-accelerator-Monte-Carlo-simulation code (EAMCC) [G. Fubiani et al., Phys. Rev. ST Accel. Beams 11, 014202 (2008)] was developed in order to provide a three-dimensional characterization of power and current deposition on all parts of the accelerator. The code includes all the relevant physics associated with secondary emission processes and consequently may be used as a tool for design improvement. In this paper, the two accelerator designs considered for the International Thermonuclear Experimental Reactor, that is, the multiaperture-multigrid and the single gap single aperture (SINGAP) designs, are discussed and their predicted performances compared. Simulations have been compared with measurements on prototype accelerators of the SINGAP type. Reasonable agreement between EAMCC calculations and measurements of backstreaming ions and transmitted electrons was found.
Highlights
Plasma heating and current drive requirements for the International Thermonuclear Experimental Reactor (ITER) include the use of high power neutral beam (NB) injectors
One of the main drawbacks of the negative ion electrostatic accelerators for high power NB injectors is the significant amount of secondary particles which are produced inside the accelerator [4]
Both accelerators consist of a plasma grid (PG) which separates the ion source from the accelerator, an extraction grid (EG), and a series of acceleration grids (AGs)
Summary
Universitede Toulouse; UPS, INPT; LAPLACE (Laboratoire Plasma et Conversion d’Energie); 118 route de Narbonne, F-31062 Toulouse cedex 9, France and CNRS; LAPLACE; F-31062 Toulouse, France. Svensson DSM/DRFC, Association EURATOM-CEA, CEA Cadarache, F-13108, St. Paul lez Durance, France (Received 10 February 2009; published 20 May 2009). Typical high-energy negative ion electrostatic accelerators such as the ones designed for fusion applications produce a significant amount of secondary particles. These particles may originate from coextracted electrons, which flow from the ion source, impacting the accelerator grids or as by-products of collisions between accelerated negative ions and the residual background gas, in the accelerator. The code includes all the relevant physics associated with secondary emission processes and may be used as a tool for design improvement. Simulations have been compared with measurements on prototype accelerators of the SINGAP type. Reasonable agreement between EAMCC calculations and measurements of backstreaming ions and transmitted electrons was found
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