Light emission processes in the context of optical beam profile monitors

Light emission from gas targets using heavy ion beam excitation is described. Typically 32 S beams with ≈90 MeV (2.8 MeV/amu) particle energy were used. This study was performed in context of optical beam profile measurements. Optical transitions from neutral and singly ionized rare gases are suggested for this application. Emission spectra and their line intensities are presented for a wide range of target pressures from about 10 –5 to 300 mbar. The effect of secondary electrons on the beam profiles is discussed. A comparison of ion beam and electron beam-induced spectra is shown and interpreted by a semi-quantitative model of the excitation mechanisms. Examples of beam profiles recorded with three different cameras through appropriate optical filters are presented. A comparison of projected profiles and radial profiles obtained by Abel inversion is given. Effective emission cross sections were measured for atomic and ionic lines at various target gas pressures and their pressure dependence interpreted by the excitation mechanisms. Examples of time-resolved measurements of light emission following pulsed excitation support the interpretation of the excitation mechanisms discussed in this overview of ion beam-induced light emission of gas targets. Graphical Abstract