Alternative principle and method in x-ray diagnostics for plasma electron temperatures

An alternative principle and method in x-ray diagnostics is proposed for measurements of plasma electron temperatures T-e. The method is different from widely utilized standard methods of x-ray pulse-height analysis and x-ray absorption. This proposal is based on three-dimensionally diffusing charges produced by x rays in a field-free substrate of a semiconductor detector, although these charges have been ignored for the x-ray measurements. This proposed theory corrects the standard conventional theory on a semiconductor response employed over the past quarter of the century for T-e analyses. Overestimations of T-e and misinterpretations of broader T-e profiles may result when the conventional theory is utilized. These lead to misunderstandings of pedestal structures in high confinement modes, electron-energy transport, as well as the misestimation of bootstrap currents and hence the misinterpretations of plasma physics itself. The proposed theory is extended to construct an alternative method for T-e measurements; this method is based on detection of the diffusion-charge distributions using a semiconductor depletion layer as a temporally changeable x-ray ''absorber'' during one plasma shot, in place of the conventional use of the depletion layer as an x-ray-sensitive region. X-ray signals in the conventional methods have a complicated dependence on plasma densities and T-e, while the proposed method is conveniently characterized by no effects of plasma densities on the signal analyses as well as no need of complicated systems for x-ray diagnostics. This method would be useful not only for providing a practical alternative but also for clarifying the physics essentials in the proposed theory through such practical examples.