There are methods to determine the plasma density, which is microwave interferometer, Faraday rotation and so on. Electron temperature is measured by using X-ray spectroscopy, Thomson scattering, Langmuir probe etc. Triple porbe is not require voltage sweep. This enable us to determine the electron temperature as well as the electron density within the order of the intrisic response time of the probe itself. In the view of features mentioned, this system is a useful diagnostic tool not only for stationary plasmas but also for rapidly varying time-dependent plasmas.
First, it is considered the linearity of the signal of triple probe with respect to the electron temperature. This is realised through biasing suffisciently negative voltage which is larger than the thermal voltage of electrons. When β is zero, Te is calculated by multiplying the measureed voltage difference between two wire by 1.4. Measured Plasma density is compared with that measured by using microwave interferometer.