A spin flipper for reversal of polarisation in a thermal atomic beam

James Floyd Scott

W Schroder, G. Baum

By using the method of diabatic passage, the authors have developed a spin flipper which allows a rapid and convenient reversal of the atomic spins. The spin flipper was tested with a polarised lithium atomic beam by analysing the atomic beam polarisation with the help of a second spin-flip region and a sextupole magnet. The reversal efficiency was measured to be 0.98 which is in agreement with the calculation. The flipper is especially useful in low-energy electron-atom crossed-beam collision studies. The experimental arrangement used also allows a precise determination of the atomic beam polarisation.

E. Torikai, Hirokazu Hori

G. Baum, W. Schröder

The spin flipper presented here is based on the method of diabatic passage. It allows for a rapid reversal of electronic as well as nuclear polarization of a thermal atomic beam without affecting beam intensity, beam profile, or magnetic fields in the interaction region. The flipper will be useful in spin dependent measurements where instrumental asymmetries and systematic errors have to be kept small. The spin flipper was tested with a polarized lithium beam in an atomic physics experiment and the reversal efficiency was found to by 0.98. The flipper can easily be adapted for other spin‐polarizable atoms, e.g. for a polarized atomic hydrogen beam target.

R. Fermani, Stefan Scheel, P. L. Knight

Wicher H. Kraan, Сергей Валентинович Григорьев, M.Th. Rekveldt

A polarised neutron beam is passed through a gradient resonance flipper. By the amplitude of their RF field, such flippers can be set at flip probability ρ = 0, 1, or ½. At ½, the neutron wave splits into a flipped and a non-flipped part with different precession. We measure the polarisation after a spin-echo (SE) setup with each precession arm made up of 2 such flippers. Offset from SE is made by varying the static fields in one flipper while the other flippers stay unchanged. This shows up as a periodic behaviour of the polarisation. With incoming polarisation parallel to the static field in the flippers–set at ρ = ½–this period is twice the period measured for both ρ = 0 and 1 and with polarisation perpendicular to the static field. In the latter experiments both components of the spinor are affected, whereas in the former experiment we create spin states in which only one spinor component in one state is affected. Hence, this experiment demonstrates explicitly the 4π-periodicity of the spinor.