Plasma detection coils in a thermonuclear device

Purpose: To enable to accurately detect the constant voltage of plasmas and enable one-turn coils to follow the extension and contraction of vacuum vessel bellows. Constitution: A pair of one-turn detection coils are disposed to the inner and outer surfaces of a vacuum vessel, by which the voltage induced to the vessel can be determined based on the difference between both of the voltage induced to these coils. An accurate constant voltage of the plasmas can be measured by subtracting the value from the inner one-turn coils. In this way, since one turn detection coils are disposed to the inside and the outside of the vacuum vessel, the one-turn voltage of plasmas can accurately be measured. Further, since the detection coils at the bellows portion are provided with an extendability, they can sufficiently absorb the extension and contraction of the bellows, by which the risk of destructing the detection coils can be eliminated and the reliability of the structure is extremely improved. (Yoshihara, H.)