A moving magnetic mirror to slow down a bunch of atoms

Ultracold and slow beams have a huge potential in metrology, matter wave interferometry and nanolithography [1]. The achievement of an ultracold beam of neutrons was made possible by specularly reflecting neutrons from a Ni-surface which moved along the beam direction [2]. This breakthrough was followed by many achievements, among which neutron optics experiments [3] and neutron interferometry experiments [4]. In another context, the deceleration of a pulsed supersonic helium beam through reflection on crystalline atomic mirrors mounted on a high speed spinning rotor is currently being investigated [5], with also the goal of reaching a very intense source for atom optics experiments. In this paper, we report on the slowing down of packets of atoms injected into a magnetic guide through their specular reflection from a moving magnetic mirror, and we also demonstrate the use of this technique to generate a high flux of slow and cold magnetically guided atoms. Such a beam is of crucial importance in order to realize a cw atom laser by implementing the forced evaporative cooling technique on a magnetically guided beam, as proposed in Ref. [6] and experimentally investigated in [7]. In the reference frame of the mirror, the atomic velocity simply changes sign after the reflection, going from vi − vm to vm − vi, where vi is the relatively high mean initial velocity of the packet and vm is the mirror velocity. In the laboratory frame, the final velocity of the packet is thus: