Electro-optical plasma probe

Abstract

A plasma probe enables simultaneous localized electrostatic measurements and optical emission spectroscopy. The probe has a support arm with an elongated longitudinally extending section and a bend section at the end of which is supported an electrical probe element composed of back-to-back charge collection plates separated by an insulating spacer. The inner plate faces an opening in the end of the elongated support arm section which defines a collimating channel. An optical fiber extends through the support arm and has an aperture in the collimating channel to receive light emitted from the plasma between the end of the elongated section of the support arm and the inner charge collection plate. The electrical probe element acts as a blocking element to block light emitted from the plasma outside of the region between the electrical probe element and the end of the support arm section. Electrical wires extend through the probe from the charge collection plates to charge detectors, allowing measurements of electron density, Electron Energy Distribution Function and ion flow. The light received by the optical fiber is detected by a spectrometer to carry out Optical Emission Spectroscopy, which can be correlated with the information obtained from the charge collection plates. The probe can be moved around a plasma confinement chamber to provide spatially localized measurements of plasma characteristics at various positions within the chamber.