The development of a characteristic heterodyne millimeter wave reflectomete
r used for density measurement on nuclear fusion plasma was reported. The i
nstrument has high measuring sensitivity and good spatial resolution and in
terference resistance by adopting modulation and heterodyne techniques. It
offers a new and high precision plasma diagnostic tool for nuclear fusion d
evices. The experiments show that the spatial resolution of this reflectome
ter is as follows: the poloidal absolute resolution Delta R-p = 0. 7cm, the
poloidal relative resolution delta R-p = Delta R-p/R-0 = 1. 08 %, the toro
idal absolute resolution Delta L-t = 0. 832cm, the toroidal relative resolu
tion delta L-t = Delta L-t/L-0 = 0. 943% (L-0 is the circumference length o
f the reflecting layer), the time resolution is about 10 mu s, the measurin
g sensitivity delta gamma(c) = 0. 79cm, the relative measuring sensitivity
delta gamma(c) = Delta gamma(c/)Ro =1. 22%. The above properties of this re
flectometer can meet all needs required by experiments on HT-6M nuclear fus
ion device.