Development of a new tracer-encapsulated solid pellet injection system for more precise control of tracer-impurity-deposit location in LHD

Abstract

A new tracer-encapsulated solid pellet (TESPEL) injection system has been developed additionally for the LHD heliotron. This system has three-dimensionally bended guide tubes, which allows us to inject the TESPEL obliquely on a poloidal cross-section of the LHD plasma. Consequently, this system enables us to control a tracer-impurity-deposited location more precisely. Moreover, this system can make it possible for the tracer impurity to be deposited even only inside the ergodic region (outside a last closed flux surface of the LHD plasma). A stereoscopic fast camera system has been also developed for capturing a three-dimensional TESPEL trajectory.

A new multi-tracer pellet injection for a simultaneous study of low- and mid/high-Z impurities in high-temperature plasmas

“…The TESPEL containing the Li 2 TiO 3 tracer (Li 2 TiO 3 -TESPEL) was injected into the LHD plasmas by using the TESPEL injector (the oblique injection type), 13 which is installed at LHD Port 3-O. This injector employs a pneumatic pipe-gun method for TESPEL acceleration, and the propellant gas (He) pressure was set at 1 MPa.…”