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The objective of the present paper is to analyze small-scale experimental facilities of TWDEC (Travelling Wave type Direct Energy Converter) and to propose a modification in regard to a measuring device of the facilities by means of numerical simulation with the axisymmetrical two-dimensional approximation (a PIC method). The numerical simulation has given the following results: (1) tendency of the numerical results agree with the experimental results on the measured deceleration efficiency, (2) the deceleration efficiency measured in the experiment will increase if the radius of Faraday cup installed in the experiment increases and (3) the wave of condensation and rarefaction of measured electric charge density, which is averaged in the r-direction below the radius of Faraday cup, is not formed enough with a small radius of Faraday cup because of the r component of electric field which is induced by the electrode geometry. [Copyright &y& Elsevier]

The separation capability of charged particles is one of the most important requirements for direct energy converters (DEC) of D–3He fusion reactors. An alternative DEC using Helmholtz coils (Helmholtz DEC) is designed to reduce the self-induced electric field and to separate charged particles when the thermal input is large as 10 MW (8.8 MW/m2). Numerical analyses with a two-dimensional approximation have given the following results. (1) When both electrodes (collectors) are grounded, it can separate ions and electrons with 99.4% ion collection efficiency. (2) When the electric potential is applied to both electrodes as nine cases, the highest separation capability of the charged particles is about 95%. (3) When Cusp DEC, Cusp DEC with closer electrodes and Helmholtz DEC are compared, only Helmholtz DEC can separate the charged particles when the electric potential is applied to the anode. [Copyright &y& Elsevier]