Laser-induced Fluorescence Diagnostic for Ions or Atoms

摘要

The laser-induced fluorescence (LIF) diagnostic is a powerful non-intrusive tool to obtain velocity distribution function of ions or atoms, with a good time (≈μs) and space (≈0. 1mm) resolution. LIF uses the optical pumping of an ion or atom transition by a laser frequency shifted by Doppler effect: if COL is the laser frequency, ω_0 the ion or atom transition frequency at rest, and V the ion or atom velocity along the laser beam v = 2πc(ω_L-ω_0)/ω_L. The level of LIF emitted by ions or atomsinside the probed volume is recorded, and by scanning the laser frequency we obtain a fluorescence signal proportional to the number of pumped ions or atoms, i.e. at the resonant velocity and consequently the velocity distribution function along the laser beam for the probed species.