Direct measurement of the energy spectrum of an intense proton beam

A time resolved magnetic spectrometer has been used to measure the energy spectrum of an intense (0.5 TW/cm²) proton beam. A thin (2400 Å) gold foil placed at the focus of an ion diode Rutherford scattered protons by 90° into the spectrometer, reducing the beam intensity to a level suitable for magnetic analysis. The scattered beam was collimated by two 1 mm diameter apertures separated by 12.3 cm. The collimated protons were deflected in a 12.7 cm diameter, 6.65 Kg samarium-cobalt permanent magnet. The deflected protons were recorded simultaneously on CR-39 and eight 1 mm² by 35 µm thick PIN diodes. A Monte Carlo computer code was used to calculate the sensitivity and resolution of the spectrometer. Data taken on Proto-I show a 150 keV to 250 keV wide proton energy spectrum at each instant in time.