Use of position sensitive detectors at energies below 1 MeV: Application to a fast determination of the pitch angle distribution of protons inside the magnetosphere

Abstract

Experimental data which were obtained in the laboratory are presented, concerning the possible use of a position sensitive detector (P.S.D.) to determine the pitch angle and energy distribution of protons inside the magnetosphere. The pitch angle α is determined by putting a slit in front of the P.S.D. Each value of α is therefore associated with a value x of the abscissa of the particle impact on the P.S.D. A division of the two impulses (one being proportional to the particle energy E, and the other to the product of x by E) gives the value of x, hence of α. It is shown that the measurement of x is improved if one takes into account the correlated noise between the two impulses, E and xE. Experimental evidence is given that with such a system, one can achieve an angular resolution of 15° for E ≈ 0.1 MeV and 2.5° for E ≈ 1 MeV. Practical application to spin stabilized satellites is also considered.