Transmission experiment for measuring total positron–atom collision cross sections in a curved, axial magnetic field

We describe and analyze a transmission experiment developed for measuring total scattering cross sections for low-energy poistrons (0.3–250 eV) colliding with gases in a region containing a curved, axial magnetic field. It is determined that spiralling does not appreciably increase the beam path length through the curved, axial magnetic field in the gas scattering region. An overall test of the experimental apparatus and technique is made by measuring total cross sections for electrons colliding with helium and argon atoms in the energy range from 1.5 to 30 eV, where it is found that the present measurements are within 15% of the most reliable prior measurements.