Analysis of behavior of charged particles in cusp type direct energy converter for advanced fusion

In order to convert kinetic energy of fusion-produced charged particles to electric power directly, separation of charged particles is necessary. A cusp type direct energy converter (CUSP-DEC) is expected to achieve this function. Some demonstration experiments using a small-scaled experimental device succeeded in efficient separation and direct energy conversion, and improvement of efficiency due to two-stage deceleration was proposed. In the present paper, orbit calculation of charged particles in the device was performed to analyze those experimental results theoretically for an application to an actual reactor. For electrons, those near the axis or with high energy go toward the point cusp and cannot be separated, and this is consistent with the experimental results. For ions, it is found that there are some particles unable to reach the additional electrode due to conditions on incident pitch angle and additional electrode bias voltage. Two cases of equivalent efficiency in a simple estimation were also examined and it was found that low voltage bias was desirable. (author)