Low energy pion detection by a silicon surface barrier telescope

Four telescopes of three (2-ΔE, 1-E) silicon surface barrier detectors each, mounted in the focal plane of a magnetic spectrometer, have been used to detect positive pions in the energy range from 4.7–17.9 MeV and negatice pions from 14.1–17.9 MeV. Positive pions from 4.7–12.7 MeV were stopped in the third detector while positive and negative pions from 14.1–17.9 MeV were detected in transmission. For energies greater than 7.4 MeV aluminum moderators were placed in front of the first detector to degrade the pion energy. Energy spectra show well resolved pion peaks with extremely low background. Double differential cross sections for the 12C(e, π+)12B, e′ reaction have been measured.