DEVELOPMENT OF RAILGUN PELLET INJECTOR USING A LASER-INDUCED PLASMA ARMATURE - RESULTS OF DUMMY PELLET ACCELERATION TESTS

Using the low electric energy railgun system, dummy pellet acceleratio n tests have been conducted to investigate the application of the elec tromagnetic railgun system for high-speed pellet injection into fusion plasmas. The primary objective of the development is to improve the p ellet acceleration efficiency and durability of the rail materials. In the system, the pellet is pre-accelerated before railgun acceleration . A laser beam is used to induce plasma armature. The ignited plasma a rmature is accelerated by an electromagnetic force that accelerates th e pellet. As low electric energy was used, rail materials were used fo r multiple operations. Tungsten-alloy rail provided longer durability and slightly higher energy conversion coefficient than copper rail. Th e energy conversion coefficient was from 0.3 to 0.5% using a plastic i nsulator. A ceramic insulator improved the energy conversion coefficie nt by 80%. The highest pellet velocity was 1.7 km/s using wooden pelle ts accelerated by 1 m-long railgun. Based on the findings, it is estim ated that the hydrogen pellet has the potential to be accelerated to 5 km/s using a 3 m-long railgun.