Effect of Collisional Quenching on the Measurement of Ion Species Ratios in Neutral Beam Injectors

In positive ion based Neutral Beam Injectors (NBI), generally corona model is used in analyzing the Doppler shifted spectroscopy diagnostics data for estimating the ion species mix in the ion-source, ion and beam species fractions in extracted beam and power fractions injected into Tokomak. At the beam energies 10-60 keV/amu, the non-radiative processes such as collisional quenching of the excited neutrals affect these estimations when background pressure is ≥ 1 mTorr. We present here a modified corona model that takes into account the effect due to collisional quenching. We describe the application of the present model to a typical Doppler shifted spectral data obtained in SST-1-NBI injector.