Our sponsor, the UCSD Pisces Laboratory, conducts PMI (Plasma-Material Interface) research for magnetic confinement fusion reactors such as the ITER (International Thermonuclear Experimental Reactor) tokamak. The materials of the first wall and blanket within these reactors must be able to withstand extreme conditions such as a heat flux of up to 10 MW/m2 and a modest flux of neutral particles (100s of eV) which are produced by the deuterium-tritium fusion reactions within the operating plasma. The Pisces Lab currently simulates these conditions with a linear plasma device called Pisces-RF, which uses an MPEX style liquid cooled RF source and high density continuous helicon-mode deuterium plasma. In the coming summer, the lab plans to incorporate a new 3 MV tandem accelerator that will deliver high-energy heavy ions at the plasma-target interface to simulate neutron irradiation. 

Project Goals

The goal of the project was to design and implement a linearly-actuated ion beam diagnostic system that characterizes the beam current and spatial profile within the target chamber of Pisces-RF using a mounted Faraday cup and scintillator. Our system actuates the measurement devices in high vacuum conditions (up to ~10-7 torr) using a metal bellows-sealed actuator while protecting them from the plasma with a water-cooled canister shield. During operation, the spatial profile of the ion beam will be measured by a camera mounted outside of the target chamber and the beam current from the Faraday cup will be read using a picoammeter in accordance with the Pisces controls system. 

Working with our sponsor we were able to find a ultra high vacuum (UHV) linear manipulator labeled above as "Actuator" uses a screw driven actuator to expand and contract a welded bellows which is welded to an upper and lower Conflat flange allowing for a vacuum seal. On the upper side we use a port aligner between the manipulator and the top flange which allows for slight angular positioning to accurately tune in the final locations of the instruments. This motion can be seen below.

Design Performance