ATOMIC BEAM PREPARATION TECHNIQUES FOR HYDROGEN MASER OPERATION WITH UNPOLARIZED ATOMS.

Hydrogen maser operation with unpolarized hydrogen atoms offers the advantage of a substantial insensitivity of hydrogen maser frequency against the resonance excitation of low frequency, Delta-mF plus or minus 1 Zeeman transitions at low-magnetic fields. This feature is of particular importance for the application of the Zeeman transition linewidth quenching method for maser cavity tuning purposes. Various experimental techniques are described and analyzed, which can be used for the preparation of hydrogen atom ensembles populating the magnetic substates of the F 1 level of the atomic hydrogen ground state, which do not possess a resulting polarization. The influence of these atomic beam preparation techniques on hydrogen maser amplitude are discussed. Both the saturation of atomic beam induced low frequency, Delta-mF plus or minus 1 Zeeman transitions and a 90 degrees non-adiabatic magnetic field flop result in a vanishing hydrogen atom polarization, but deteriorate the maser amplitude considerably. A periodic switching between 0 and 180 degrees non-adiabatic magnetic field flop conditions, performed with a periodicity which is fast compared to the relaxation rates within the hydrogen maser storage bulb, results in an ensemble of hydrogen atoms with vanishing polarization and does not deteriorate the hydrogen maser oscillation characteristics. Author