Particle Identification at Relativistic Energies by the Use of Secondary Emitters

The usefulness of negative electron affinity secondary emitters as detectors of particles in the high relativistic region is studied theoretically in detail. It is found that GaP(Cs) has poor secondary escape statistics, resulting in the inability to distinguish between 200 BeV/c protons and pions in single particle experiments. GaAs (Cs+[O2+ Cs]) has good escape statistics, but its active depth may be too large, and density effects are expected to set in. A GaP(1-x) - GaAs(x) heterojunction which could solve both problems is discussed. In any case, it is found that non-linear filtering of the near Landau distributed signals from secondary emitters is required in order to obtain useful particle discrimination. One feasible scheme is proposed which should allow separating 200 BeV/c protons and pions, for example, with 90% efficiency or better at near 100% confidence.