Triple Probe Error Evaluation Caused by Spatial Separation in the HL-2A Tokamak

The systematic error between the measured electron temperature T
_e,m
and the real electron temperature T
_e
caused by the spatial separation of a triple probe is introduced. The detailed analysis of the systematic error is presented and the relation between T
_e,m
and T
_e
is derived. By comparing the fluctuation of the measured temperature |T̃
_e,m
| and the real temperature fluctuation |T̃
_e
|, we find that |
_T̃e,m
| ≥ |T̃
_e
|. In addition, electron temperature T
_e
, density n
_e
, floating potential V
_f
, and their fluctuation profiles are measured at the edge of HL-2A tokamak with a reciprocating probe system. We experimentally verified that the amplitude of floating potential fluctuation |Ṽ
_f
| is about 3 ~ 4 times larger than that of α|T̃
_e,m
|; in this condition, we can use the floating potential fluctuation Ṽ
_f
to stand for the plasma potential fluctuation Ṽ
_p
.