The problem of separation of beams of particles of different masses but of the same momentum at Bev energies is the subject of a great deal of study at several high energy laboratories. In this note we shall describe the problem and tabulate a few of the cogent parameters. Frequently the student of high energy interactions is faced with a beam of miscellaneous particles coming from an accelerator. By standard techniques this beam can be rendered approximately parallel and an inch or so in diameter. By passage through a magnetic field the beam can be analyzed in momentum. Now it frequently happens that the particles in which the experimenter is particularly interested make up only a small fraction of the beam and the exigencies of the proposed experiment may well demand that the background of undesired particles be drastically reduced. The problem is difficult because the velocities of the various particles are almost equal to each other and to the velocity of lights; this makes time-of-flight techniques relatively ineffective. The energies of the particles are almost equal so electrostatic separation also is difficult. Since the beam is already analyzed in momentum, further separation by magnetic means is impossible.

Maintenance of polarization of polarized protons in a linear accelerator is known to be feasible. Circular accelerators present a different problem, and the investigation of the interaction of orbit dynamics and particle polarization in general is undertaken. The equation of motion of the spin vector of a charged particle in a magnetic field as formulated by Bargmann, Michel, and Telegdi is utilized in the study of depolarization for several accelerators. High values of depolarization are obtained, and means for avoiding such depolarization are suggested. (D.C.W.)