Stimulated Laser Cooling of a Fast Particle Beam

Abstract

This chapter presents an experimental test setup for the study of the dipole force in a fast atom beam. In contrast to the scattering force that saturates at high-intensity lasers, the dipole force requires the atomic transitions to be saturated to observe decelleration/acceleration for a blue/ red shifted detuning. In this way, a dipole force that is much larger than the scattering force can be realized. The condition for the dipole force to be optimum is that the velocity of the particles must be low relative to the standing wave. This can conveniently be satisfied in a transverse geometry in atomic beams; however, at sufficiently high Rabi frequencies, cooling is even observed in a longitudinal geometry. Fast beams, produced in ion sources and extracted by ion optics, have typical relative velocity spreads Δv/v ∼ 10 –3 or better, corresponding to velocity spreads Δν ∼ 20 m/sec. This makes stimulated laser cooling an attractive possibility for cooling of fast beams, with cooling times limited by the transit time.