A double-focusing magnetic field for a spectrometer of the flat type which gives radial focusing to roughly the sixth order, and which utilizes azimuthal variation of the field coefficients, has been devised.

The reaction pp {yields} {pi}{sup +}d resulting from the high energy cosmic rays incident on the interstellar hydrogen gas gives rise to secondary deuterons. Since the total cross section for this reaction is appreciable only at proton kinetic energies of 600 MeV, the deuterons have a very small spread in energy. It is estimated that the flux of deuterons from this mechanism should be easily discernible from deuterons produced by other reactions and copious enough to be detected at the earth. The narrow deuteron energy distribution could provide an energy calibration for the study of the existence of a postinjection acceleration.