Townsend Ionization Coefficient for Hydrogen in a Transverse Strong Magnetic Field

The Townsend ionization coefficient αp ${(cm{-}mm{{0ex}{0ex}}Hg{{0ex}{0ex}}at{{0ex}{0ex}}20{^∘{}}C)}^{{-}1}$ was measured across a strong magnetic field by varying the electrode gap in a cylindrical geometry. Measurements were made for $B/pup to 4000 G/mm Hg at 20^∘C and for{E}{p{(1+{{{ω}}b}²{{τ}}²)}1/2}$ less than 150 V/cm---mm Hg, where ${{ω}}b{τ}$ is the ratio of the electron cyclotron to elastic-collision frequencies. A theoretical expression of Blevin and Haydon ${{α}}{p}={C}₁{(1+{{{ω}}b}²{{τ}}²)}1/2×{}exp[{-}{C}₂(p/E){(1+{{{ω}}b}²{{τ}}²)}1/2], is shown to fit the points well over a limited range of values. The effective collision frequency per mm Hg (3.1×{10}⁹$/sec) that makes the theory fit is about three-fifths of the average momentum-transfer collision frequency. Analysis shows that this discrepancy results from deviations in the electron distribution function because the actual elastic-collision frequency is not the theoretically assumed constant.