High Resolution Study of Nuclear Reactions by p-n Junction Detecors

The specific problems which arise from the use of p-n junctions for the detection of particles emitted in nuclear reactions are studied. The mechanism which allows the distinction between particles of different nature emitted in nuclear reactions like (d, p), (d,¿), (d, d) is explained. Behind the barrier there is a "diffusion zone" which furnishes a slow component to the pulse. Pulse shape selection technics permit elimination of pulses due to long range particles. The diffusion zone is then used as an anticoincidence detector. Manufacturing of detectors in low resistivity material is necessary for the detection of short range particles. Inverse current rapidly increases with the ionic bombardment induced by the beam on the target. A simple electrostatic deflection system can protect the junction. The energy of the emitted particles rapidly varies with the angle of observation. This leads to the use of slit shaped detectors for maximum resolution. On the other hand several detectors can be connected in parallel to the input of the sme amplifier: well resolved peaks are obtained if the difference in angle between the detectors is sufficient. Typical spectra obtained in course of the study of the reactions O16 (d, d) O16, O16(d,¿) N14, O18(d,¿)N16, O18(p,¿)N15 are presented. ¿ ray groups 70 KeV apart have been separated.