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The core electron temperature (T(e0)) of neutral beam heated plasmas is determined in TJ-II stellarator by using soft x ray detectors with beryllium filters of different thickness, based on the method known as the foil absorption technique. T(e0) estimations are done with the impurity code IONEQ, making use of complementary information from the TJ-II soft x ray tomography and the VUV survey diagnostics. When considering the actual electron density and temperature profile shapes, an acceptable agreement is found with Thomson scattering measurements for 8 different magnetic configurations. The impact of the use of both neutral beam injectors on the T(e0) measurements is addressed. Also, the behaviour of T(e0) during spontaneous profile transitions is presented.

The design and preliminary results from a prototype of a multifilter based electron temperature diagnostic for the TJ-II stellarator are presented. The diagnostic consists of four photodiodes with filters of different thicknesses to determine the electron temperature in a wide variety of plasma compositions, thanks to the set of six different signal-pairs ratios available. The impurity transport code IONEQ, the TJ-II soft x-ray tomography, and the VUV survey diagnostics give the necessary information to assess the proposed diagnostic reliability. In parallel, a vacuum-compatible multichannel electronic board has been designed for a future linear array to determine electron temperature profiles in high-density plasmas.