Core electron temperature diagnostic for high-density plasmas in the TJ-II stellarator

摘要

A new diagnostic to monitor the electron temperature with temporal and spatial resolution has been proposed for the TJ-II stellarator [1] based on the method known as the two-filters technique [2]. It will be destined to substitute the 16-channel heterodyne ECE diagnostic to give the time evolution of the electron temperature profiles when plasma electron density is higher than 1.7xl0~(19) m~(-3). In the last experimental campaign, a single-channel prototype consisting in a soft x-ray system equipped with four filters of different thicknesses has been constructed and installed in TJ-II. It is well known that this method to determine electron temperature has two main drawbacks, namely, the deviation of the electron energy 1 distribution function from a Maxwellian and the spurious pollution of the continuum part of the soft x-ray spectra due to line radiation emissions from plasma impurities. Therefore, as it is done in other magnetic confinement devices in operation [3,4],proper interpretation of data obtained with this diagnostic requires the help of impurity transport codes. As was explained in a previous work [5], the IONEQ code [6] has been used initially to design the diagnostic setup and, once experimental data were obtained, to find the best fit to determine the electron temperature in TJ-II plasmas.