Ultrashort-pulse reflectometer performance on Sustained Spheromak Physics Experiment

Time-resolved density profiles on the Sustained Spheromak Physics Experiment device are now generated automatically from data collected by an ultrashort-pulse reflectometry (USPR) diagnostic comprised of 24 frequency channels spanning 34–75 GHz . Upgrades in USPR timing electronics and reconstruction software, coupled with new low noise amplifiers and reduced bandwidth filters, have significantly decreased amplitude and timing jitter enabling simultaneous density profile and multilayer density fluctuation operation. Hardware and software components of the upgraded USPR system are described, and sample profile and fluctuation data are presented. A new system layout is proposed to increase the USPR dynamic range by 8–10 dB .