Development of a single capacitor-voltage-divider flux-loop for field-reversed theta-pinch plasmas

As one of the most important diagnostics of field reversed plasma, the single-flux loop around the vacuum chamber is usually used to measure the magnetic flux to deduce the plasma size. In the theta-pinch process, the power supply will drive a large current through the coil in a short time to generate a high magnetic field, which will cause the magnetic flux in the vacuum chamber to rise sharply. Therefore, the induced voltage on the single-flux loop may be very strong and have high-frequency components. A voltage divider must be used to reduce the induced voltage to the range that the transmission line can withstand. According to the high-frequency characteristics of the measured signal, this paper designs a capacitor voltage divider single-flux loop with reference to the capacitive voltage divider in the industry. After theoretical derivation of parameter selection and then in the preliminary experimental test with and without plasma, the effectiveness of the distributed capacitor flux loop is verified.