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Description
As the pellet injection for the fuel of the Large Helical Device (LHD), a pneumatic pellet injection is generally used. Although this method injects some pellets made of frozen hydrogen gas into a plasma of the LHD at the velocity of 1.2 km/s, the pellet does not reach the plasma core. For this reason, this method is not efficient in the fuel supply.
Recently, a novel pellet injection system by using a Superconducting Linear Acceleration (SLA) has been proposed to inject the ice pellets into the plasma core to supply the fuel in the LHD. In the system, a pellet container attaching the HTS films for acceleration and levitation is accelerated like the magnetic levitation train electromagnetically. Consequently, the estimation speed of the pellet injection system by the SLA becomes 5 km/s or more. However, it is not clear how much pellet speed can be obtained because the SLA has not yet applied to the pellet injection system.
In the previous study, we develop the FEM code for analyzing a shielding current density in an HTS film to investigate the feasibility of the SLA system. By using the code, the results of the computations show that the pellet container can be accelerated to 5 km/s or more by about 6.9 seconds by using the multiple coils for the acceleration. As a result, the required distance of the electromagnetic rails becomes about 21 km.
The purpose of the present study is to enhance the acceleration performance of the SLA system by locating another acceleration coil outside a conventional one. In addition, we investigate the influence of the experimental conditions of the SLA system on acceleration performance.
