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

Abstract

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 $| \tilde {T}_{e,m}|$ and the real temperature fluctuation $| \tilde {T}_{e}|$ , we find that $| \tilde {T}_{e,m} |\ge | \tilde {T}_{e}|$ . 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 $| \tilde {V}_{f} |$ is about 3 ~ 4 times larger than that of $\boldsymbol {\alpha }| \tilde {T}_{e,m} |$ ; in this condition, we can use the floating potential fluctuation $\tilde {V}_{f}$ to stand for the plasma potential fluctuation $\tilde {V}_{p}$ .