Neutral beam diagnostics

Fig. 8.4. Comparison of the electron temperature measured in the plasma center by the X-ray spectrometer and the ECE diagnostics with hydrogen (solid points) and deuterium (open points) as working gas. The squares and triangles correspond to discharges with neutral beam injection [3]...

In the context of hydrogen neutral beam attenuation kinetics in fusion plasmas, and charge exchange core plasma diagnostics, the important hydrogen atom processes are those with highly stripped impurity ions, Aqz (where Z is the atomic number of impurity, and q is its charge)... 

New fusion applications include the concept of production of intense negative ion beams ( ) (for neutral beam injection for heating and diagnostics in tokamaks or other magnetically confined plasmas (26, 28)) by using photodissociation to ion pairs (e.g. NaLi + hVyy Na + Li") in supersonic molecular beams. Another promising concept is the use of laser induced fluorescence to monitor very low tritium concentrations (as little as 10 Tj/cm ) under fusion reactor conditions (29). 

Electron ionization (El) is surely the ionization method most widely employed (Mark and Dunn, 1985). This method was proposed and used from the early days of mass spectrometry (MS) applications in the chemical world and is still of wide interest. This interest is due to the presence of libraries of El mass spectra, which allows easy identification of unknown previously studied analytes. The El method suffers from two limitations It is based on the gas-phase interactions between the neutral molecules of the analyte and an electron beam of mean energy 70 eV. This interaction leads to the deposition of internal energy in the molecules of the analyte, which is reflected in the production of odd-electron molecular ([M]+ ) and fragment ions. These ions are highly diagnostic from a structural point of view. 

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