  Electric field measurement in plasmas permits quantitative comparison between
the experiment and the simulation in this study. An electro-optic (EO) sensor
based on Pockels effect is demonstrated to measure wave electric fields in the
laboratory magnetosphere of the RT-1 device with high frequency heating
sources. This system gives the merits that electric field measurements can
detect electrostatic waves separated clearly from wave magnetic fields, and
that the sensor head is separated electrically from strong stray fields in
circumference. The electromagnetic waves are excited at the double loop antenna
for ion heating in electron cyclotron heated plasmas. In the air, the measured
wave electric fields are in good absolute agreement with those predicted by the
TASK/WF2 code. In inhomogeneous plasmas, the wave electric fields in the
peripheral region are enhanced compared with the simulated electric fields. The
potential oscillation of the antenna is one of the possible reason to explain
the experimental results qualitatively.
