Absolute detection efficiencies of low energy H, H-, H+, H-2(+) and H-3(+)incident on a multichannel plate detector

Measured absolute detection efficiencies are presented for H, H- and H-n(+) (n = 1, 2, 3) impacting a commercially available, dual multichannel plate (MCP) electron multiplier at kinetic energies ranging from 30 to 1000 eV. M easurements involving isotopic substitutions (D, D-, D-n(+)) and Ar+ are al so presented. In addition, atomic hydrogen detection efficiencies relative to those of H+ and H- are given, as they may have a more universal applicat ion. For the three charge states, H, H+ and H-, the absolute detection effi ciencies are markedly different at low energies and converge to a nearly un iform Value of similar to 70% with increasing projectile energy. The energy dependence is strongest for H+, varying nearly three orders of magnitude o ver the energy range studied, and weakest for H-, varying by less than one order of magnitude. In general, for the low energy positive ions at a given energy, the lighter the incident particle mass, the greater the probabilit y of its detection. (C) 2000 Elsevier Science B.V. All rights reserved.