A new perspective on synchrotron radiation applications: Runaway electrons studies using a hard x-ray detection in tokamaks.

The synchrotron radiation emitted by runaway electrons in fusion plasma provides information regarding the particle momentum and pitch-angles of the runaway electron population through the strong dependence of the synchrotron spectrum on these parameters. Information about the runaway density and its spatial distribution, as well as the time evolution of the above quantities, can also be deduced. On the other hand, control of radial electric filed and suggestion of the methods to reduce plasma turbulence are important issues in confinement process and particle transport in the tokamaks. In this work, the effects of positive limiter biasing on electrical fluctuations and hard x-ray have been investigated. For this purpose, the radial and poloidal electric fields have been measured using the Langmuir probe, and hard x-ray has been measured using the Scintillator detector. The biased electric voltage was +250 V. Also, electrical fluctuations are analyzed using wavelet transform technique in the presence of positive biasing and without it. The results show that time-frequency activity of radial electric field multiplies in the presence of positive biasing while poloidal electric filed frequency intensity decreases.