Beam Energy Recovery for Fusion: Collector design for the test on NIO1 source

The next fusion project DEMO which will be the evolution of the Experimental Fusion Reactor ITER, would require a high efficient energy production. As in ITER, DEMO will use fast Neutral Beam (NB) injectors to increase the plasma temperature needed for the fusion reaction ignition in the TOKAMAK. A way to recover the electric energy production efficiency in DEMO could be the beam energy recover in the NB production [1]. The NB are produced by a Dbeam generated by e negative ion source which is neutralized by a gas cell with an efficiency of 60%. beam energy recovery system of the residual charged particles would improve that efficiency. A proposal of a very simple energy recovery device with an axisymmetric cylindrical ion collector which uses only decelerating electric fields combined with the beam space charge effect has been recently done [2]. This energy recovery system will be tested on the beam of the NIO1 source. It is a compact ion source (scaled down from ITER size sources) which has been developed at INFN-LNL and Consorzio RFX (Padua), where effect of wall condition and source magnetic field changes on negative ion production can be easily studied [3]. In this contribution the detailed collector design to be used in the test on one of the beamlet of the NIO1 source will be presented and discussed. Furthermore, a preliminary trajectory simulation for a beam with a rectangular geometry similar to the beam used in ITER to verify the beam recovery for a non-axial symmetric geometry will be also argued.