Link do seminarium: https://bit.ly/3BN7Bb2

Abstract:

The low-Z impurities of the Magnetic Confined Fusion (MCF) plasmas can provide an important information about the wall condition and plasma-wall interactions. Because of that, for the W7-X experiment, a special spectrometer called “C/O Monitor” was designed. It is a dedicated spectrometer system which purpose is to measure four Lyman-α transitions of four low-Z impurities like carbon (3.4 nm), oxygen (1.9 nm), nitrogen (2.5 nm) and boron (4.9 nm). It is high throughput and high time resolution system which will measure the line intensities evolution of indicated elements including information of the background as well. It consists of two vacuum chambers positioned at nearly horizontal position, each containing two energy channels. Their line of sights will cross at the magnetic axis of the W7-X plasma. Its installation is planned before the next Operational Phase (OP 2) which is going to be performed on 2022. The “C/O monitor” system is already designed and has entered into the final executive stage.

In the term of the “C/O monitor” diagnostic system, it is important to determine the incoming photon flux. Moreover, it would be important for quantitative interpretation of the experimental data as well as for the (attempt) of the calibration of this system. Since the discussed diagnostic will deliver continuous information about the line intensities, it is crucial to understand the origin of the obtained signals with respect to the experimental plasma conditions (electron temperature and density). This however might be difficult because of the broad acceptance angle of the spectrometer and irregular shape of the plasma edge or SOL where the radiation is expected to mostly come from, depending on the plasma temperature. For that reason, numerous analyses assuming various ranges of electron density and temperature profiles of the W7-X plasmas have been performed (assuming corona equilibrium as well including impurity transport). The aim of this work was to estimate the expected radiant flux and determine major factors affecting the “C/O Monitor” signals. This will allow to improve understanding between measured signals and impurity concentrations.