The effects of density fluctuation on density profile measurements using abroadband frequency modulated reflectometer

Numerical simulations of frequency modulation (FM) reflectometry are carrie d out for the effects of density fluctuations on phase measurements. It is found that the fluctuation amplitude, the fluctuation frequency, the sweep time of a source, and the beat frequency of a mixer output play the importa nt roles. The reliability of density profile measurement is investigated fo r various sweep times and local path lengths. It is demonstrated that the r econstructed density profiles seem to be improved when the sweep time is fa ster than 100 mu s and the local path length is shorter than 1 m. The numer ical simulations are compared with the experimental results obtained from a broadband FM reflectometer applied to the GAMMA 10 tandem mirror. (C) 1999 American Institute of Physics. [S0034-6748(99)53801-X].