The measurement of electron spectra in the track of protons in water vapour.

Abstract

The spectra of the electrons in the track of 1 MeV protons passing through water vapour were measured with a retarding field spectrometer mounted in a movable evacuated probe. About 50,000 measurements were performed in the energy range from 0 to 3000 eV at more than 1300 different radial and angular positions relative to the proton path. The radial distances, reduced to density 1g.cm-3, range from 0.25 nm, where the primary electron spectrum is predominant, to 30 nm, where the electrons are slowed down by collisions with water molecules. From the dense net of data the following were calculated: (i) The dependency of the energy fluence on the solid angle at different distances; (ii)The energy flux vectors for different energy ranges as a function of the radial distance from the proton path; (iii) The spectral fluences at different distances from the proton path; (iv) The degradation spectrum