On the application of the Rutherford-scattering diagnostics to ion temperature measurements

The feasibility for application of small-angle Rutherford scattering of fast neutrals by plasma ions as a possible ion-temperature diagnostic is investigated for a medium-sized tokamak. The analysis is based on elastic scattering of helium atoms from a 20–40 keV and 10 A m−2 probing beam, which are subsequently recorded by a time-of-flight spectrometer with high-energy resolution. Calculations show that the ion temperature can be measured with a 10% accuracy within 1 ms and with a spatial resolution of about 0.1 m. The possible influence of highly charged impurity atoms on the accuracy of the determined temperature value has been closely examined and appears to be negligible at the chosen set of parameters. The good spatial and temporal resolution make the method very suitable to determine the energy deposition profiles in case localized heating is applied to the plasma.