Kouji Satake

Railgun pellet injection system for fusion experimental devices

Abstract A railgun pellet injection system has been developed for fusion experimental devices. Using a low electric energy railgun system, hydrogen pellet acceleration tests have been conducted to investigate the application of the electromagnetic railgun system for high speed pellet injection into fusion plasmas. In the system, the pellet is pre-accelerated before railgun acceleration. A laser beam is used to induce plasma armature. The ignited plasma armature is accelerated by an electromagnetic force that accelerates the pellet. Under the same operational conditions, the energy conversion coefficient for the dummy pellets was around 0.4%, while that for the hydrogen pellets was around 0.12%. The highest hydrogen pellet velocity was 1.4 km s−1 using a 1 m long railgun. Based on the findings, it is estimated that the hydrogen pellet has the potential to be accelerated to 5 km s−1 using a 3 m long railgun.

DEVELOPMENT OF RAILGUN SYSTEM FOR HIGH-SPEED PELLET INJECTION

The application of the electromagnetic railgun system for high-speed pellet injection has been investigated. A pulse laser beam is employed to induce an initial plasma armature between rails. This unique feature provides the reduction of the supplied voltage to the rails, in order to avoid any unnecessary breakdown between the rails and to reduce the erosion of the rails. The ignited plasma armature is accelerated by an electromagnetic (Lorentz) force, that accelerates the pellet to high velocity. A series of experiments using dummy pellets have been conducted to examine the system, along with theoretical study. This report presents the current results of our research and development on the railgun system.