A Quantitative Study of Scattering Phenomena in an Electromagnetic Separator

Abstract

A series of recent experiments has shown that the elastic scattering of a directed ion beam by residual gas is one of the dominant factors causing contamination in an electromagnetic mass separator. This phenomenon is treated numerically, based on geometrical considerations and on an appropriate and reliable interaction potential between the ions and the residual gas molecules. The result is a relation[Formula: see text]expressing the fractional contamination as a function of: the residual gas molecule concentration nr, the fractional mass difference ΔM/M, the collector slit width Δx, the configuration factor [Formula: see text] and constants (σ0 and n) which appear in the expression for the differential cross section. The reciprocal value [Formula: see text] imposes an upper limit to the enhancement factor. By performing the various integrations in a different sequence, a general expression for the transmission from source to collector is obtained. The influence of losses caused by inelastic scattering can be easily incorporated. For elements with a mass number of about 200, scattered by air and for an accelerating voltage of about 30 kv, this expression takes the form:[Formula: see text]where L is the total ion path length in the separator.

Mass Separation for Nuclear Reaction Studies

“…The degree of isotopic purity that can be achieved depends on the dispersion and on the beam profile. The sharpness of the lines depends on the running conditions but there will always be a more or less pronounced tail due to scattering processes that will cause some contamination (44,45). The use of narrow slits is to be avoided when yields of various isotopes are to be compared since these will cause a loss which can hardly be made constant over the whole mass spec trum.…”

Calculation of the effect of collisional broadening on high-resolution translational energy loss spectra

“…Theoretical modelling of ion-scattering processes in a mass spectrometer has been studied previously by Aleksandrov et al [8][9][10] and Menat and coworkers [11,12].…”