Spectroscopic measurement of the Doppler broadening region of He II line emission of DT plasmas using impurity pellets

The feasibility of spectroscopic measurement of the velocity distribution of alpha particle using the ablation cloud of a lithium or boron pellet was tested in the DT experiment of TFTR. The measurement was performed using a 10-channel narrow-band filtered spectrometer in the wavelength covering the 3.5 MeV alpha particle Doppler broadening region of the He II 468.6 nm line and its vicinity. The spectra from a lithium pellet consists of the continuum bremsstrablung background, lithium line emissions and possibly a 468.6 nm helium line. However, no clear evidence of alpha particles was observed, even when boron pellets were injected.