Abstract
The feasibility of electron density measurement using the relativistic downshift frequency effect of electron cyclotron emission in tokamak plasmas has been studied by numerical calculation. It is found that electron density measurement can be performed by observing the frequency shift from the nonrelativistic electron cyclotron frequency. The frequency shift is large when the observation is carried out from the high-field-side of torus. As this large frequency shift depends mainly on electron temperature and density, electron density can be determined while electron temperature is obtained from the observation of the low-field-side.