High-speed hydrogen pellet acceleration using an electromagnetic railgun system

Using a low electric energy railgun system, solid hydrogen pellet acceleration tests have been conducted to investigate the application of the electromagnetic railgun system for high-speed pellet injection into fusion plasmas. Pneumatically pre-accelerated hydrogen pellets measuring 3 mm in diameter and 4–9 mm in length were successfully accelerated by a railgun system that uses a laser-induced plasma armature formation. A 2 m long single railgun with ceramic insulators accelerated the hydrogen pellet to 2.6 km s−1 with a supplied energy of 1.7 kJ. The average acceleration rate and the energy conversion coefficient were improved to about 1.6×106m s−2 and 0.37%, which is 1.6 times and three times as large as that using a railgun with plastic insulators, respectively. Furthermore, using the 1 m long augment railgun with ceramic insulators, the energy conversion coefficient was improved to about 0.55% while the acceleration rate was increased to 2.4×106 m s−2. The highest hydrogen pellet velocity attained was about 2.3 km s−1 for the augment railgun under an energy supply of 1.1 kJ. Based on the findings, it is expected that the acceleration efficiency and the pellet velocity can be further improved by using a longer augment railgun with ceramic insulators and by applying an optimal power supply.