Development and Implementation of a New HELIOS Diagnostic using a Fast Piezoelectric Valve on the Prototype Material Plasma Exposure eXperiment*

A new helium line-ratio spectral monitoring (HELIOS) diagnostic, using a piezoelectric valve with high duty cycles (on/off times~ ms), allowing for good background correction, and measured particle flowrates on the order of \textasciitilde 1020 particles/second is being implemented on Oak Ridge National Laboratory's (ORNL) Prototype Material Plasma Exposure eXperiment (Proto-MPEX).~ Built in collaboration with the University of Wisconsin -- Madison, the HELIOS diagnostic communicates with a Labview program for controlled bursts of helium into the vessel.~ The open magnetic geometry of Proto-MPEX is ideal for testing and characterizing a HELIOS diagnostic.~ The circular cross-section with four ports allows for cross comparison between different diagnostics:~ 1) Helium injection with the piezoelectric puff valve, 2) HELIOS line-of-sight high-gain observation, 3) scan-able Double Langmuir probe, and 4) HELIOS 2D imaging observation. Electron density and temperature measurements from the various techniques will be compared.