Ultrashort pulse reflectometry for density profile and fluctuation measurements on SSPX

Abstract

A broadband, multichannel ultrashort pulse reflectometry (USPR) diagnostic on the Sustained Spheromak Physics eXperiment device has recently undergone a number of system upgrades, which has resulted in significant improvements in the signal-to-noise ratio of the USPR signals and a dramatic reduction in the number of "lost signals" in which the amplitude of the reflected wave form drops below detection threshold. This has greatly enhanced the ability of USPR to study relatively fast density profile modifications, and allows the simultaneous monitoring of multiple density layers with as short as a 3 mus pulse repetition rate. This article provides details of the upgraded USPR system together with density profiles and fluctuation data. (C) 2003 American Institute of Physics.