Electron temperature estimation using the Pulse Height Analysis system at Wendelstein 7-X stellarator

This paper presents measurements of the electron temperature in Wendelstein 7-X (W7-X) stellarator plasmas heated by electron-cyclotron-resonance (ECRH) during the first operational phase (OP1.1). The analysis of the slope of the observed X-ray continuum emission (in a semi-logarithmic plot) measured by the use of the Pulse Height Analysis (PHA) system, provides the information about the electron temperature (Te) of the hydrogen plasma. The determination of this fundamental plasma parameter is based on the exponential dependence of the continuum radiation (Bremsstrahlung) on photon energy assuming Maxwellian distribution. In this paper, some experimental results of the estimated electron temperature are presented and compared to the results obtained from the simulations of X-ray spectrum and other diagnostic like the Thomson Scattering (TS) system.