Design of a shattered pellet injector and preliminary bench tests of Ne pellet formation for EAST disruption mitigation

Abstract

Shattered pellet injection (SPI) technology has been demonstrated as a novel effective method for disruption mitigation in tokamaks. To further verify the superiority and reliability of this technology, in this study, a SPI test stand based on in-situ gas formation technology was designed and constructed for Experimental Advanced Superconducting Tokamak (EAST). A pellet producer, a gas feeding system, a pumping system, diagnostic units, and a shatter chamber have been developed and are served as the main components of the SPI test stand. We experimentally demonstrated that the SPI test stand developed in this study can be used for forming and accelerating impurity pellets. On the test stand, Ne pellets with a diameter of ∼5 mm were successfully formed, and their length was varied from ∼7 mm to ∼15 mm by changing the heating power of the heat sinks after the formation of the pellets. The feasibility of pellet shattering was verified using a shatter tube (inner diameter: 15.7 mm) in the shatter chamber. The results showed that Ne pellets with a velocity of ∼150 m/s could be broken into fragments without removing the propellant gas by passing them through a ∼20° bent tube. The SPI test stand developed in this study and the experimental results presented in this paper will serve as the technical basis for developing a reliable SPI system on EAST and will be a good reference for the development of such systems on other fusion devices.