An effective method for determining the plasma displacement on HT-7 superconducting tokamak

In this paper, an approximate expression of magnetic surface function was derived from the well-known Shafranov formula. It directly leads to a simple method for determining the plasma displacement on the HT-7 superconducting Tokamak. In practice, 4 full flux loops were implanted inside the inner surface of the internal copper shell. Signals were acquisited by VAX3300 computer after optical-electro isolated and pre-amplified in a CAMAC crate. Analysis of those data obtained from HT-7 ohmic discharges and current ramp up/down experiments show that the results agree well with another approach in the same device. It was proved to be accurate and effective in routine use. The differences between these two approaches were discussed. Some interesting features of our experiments were also presented.