Deceleration in a traveling wave direct energy converter for advanced fusion

A traveling wave direct energy converter (TWDEC) is desirable for the direct energy conversion of fast protons produced by deuterium-helium-3 fusion, since the proton energy is so great that conventional electrostatic converters cannot be used. This paper presents the results of high-energy TWDEC simulation experiments as a follow-up to the previously reported proof-of-principle experiments for low energy. As the beam energy increases, the efficiency of energy recovery is expected to improve, and since the variation in the beam velocity becomes large, its effect cannot be neglected. The decelerator electrodes intervals were designed to take into account the velocity matching between the decelerated beam and the traveling wave. The variable intervals also dictate the small size of the hole in the electrode through which the beam passes. A more appropriate hole size results in deceleration efficiency over 20% for a unit wavelength. The effectiveness of the matching design was confirmed by the dependence of deceleration efficiency on the beam energy. The experimental scaling of the deceleration efficiency for a unit wavelength was extended to approach the level of a commercial-scale device. (C) 2008 Elsevier B.V. All rights reserved.