  In this paper, the performances of a type of the domestic THGEM (THick
Gaseous Electron Multiplier) working in the Ar/CO2 mixtures are reported in
details. This kind of single THGEM can provide the gain range from 100 to 1000,
which is very suitable for the application in the neutron detection. In order
to study its basic characteristics as the references for the development of
THGEM based neutron detector, the counting rate plateau, the energy resolution
and the gain of the THGEM have been measured in the different Ar/CO2 mixtures
with the change of the electrical fields. For the Ar/CO2(90%/10%) gas mixture,
a wide counting rate plateau is got from 720V to 770V with the plateau slope of
2.4% / 100 V and the excellent energy resolution about 22% is obtained at the
5.9keV full energy peak of the 55Fe X-ray source.
