Diamagnetic measurement on HT-7 superconducting tokamak

Diamagnetic measurement is a basic diagnostics on tokamak. Some important plasma parameters such as plasma energy and betap βp can be obtained from this measurement. For most case, diamagnetic flux ΔΦ is extremely smaller than toroidal flux Φ (ΔΦ/Φ − 10−4). Therefore we have to use techniques that allow measurement to better than 1 part in 104 to get 10% accuracy in value of βp. Using a compensation coil is a typical technique to improve the signal to noise ratio. In this paper the design of diamagnetic diagnostics system for HT-7 superconducting tokamak device is introduced and some experimental results of plasma energy and βp are given in different plasma discharges.