Mass-dependent channel electron multiplier operation

Abstract

This paper contains the results of measurements to determine the absolute counting efficiencies and pulse height distributions of a continuous channel electron multiplier (Spiraltron) used in the detection of hydrogen, argon, and xenon ions. The technique involves the post-acceleration of 8-eV ion beams to energies between 100 and 4000 eV. The absolute counting efficiency versus effective ion energy for the ions H2+, A+, and Xe+ is given. The Spiraltron was operated in a marginally gain saturated mode to investigate the charge pulse distribution for the three ions H2+, A+, and Xe+ at ion energies of 3 keV. The pulse height distribution for the light ion H2+ peaked near an equivalent gain of 2×107, while the distributions for the heavier ions displayed no significant peaks. This study suggests that discrimination between light and heavy ions may be accomplished in the energy range E<2 keV by utilizing continuous channel electron multipliers.

Quantitative detection of low energy positive and negative ions with a channel electron multiplier

“…The rise in efficiency from 0.28 to 9 keV is similar to the relative efficiency measurements of Burrous et al 8 for detection of H ϩ , He ϩ , Ne ϩ , and Ar ϩ . Our absolute efficiency for O ϩ detection is 10% to 30% higher than that measured by Fields et al 9 for Ar ϩ and Xe ϩ but again the energy dependence is similar. The differences are likely due to both the different detected species and the different CEMs.…”

“…In particular, the CEM's high efficiency and ability to withstand repeated and extended exposure to air make it ideal for experimental systems involving ion counting. While there have been numerous calibrations of CEMs for the detection of electrons, 1-5 photons, 1,2,6,7 and various species of positive ions 1,2, 8,9 and neutral atoms, 1,2,10 very little has been done to calibrate for negative ions. 11 In our studies of charge exchange between atoms and surfaces, we scatter O ϩ from Cu͑001͒ and measure the scattered yields of both positive and negative oxygen ions.…”

Absolute calibration of a multichannel plate detector for low energy O, O−, and O+

“…There have been many attempts to characterize and predict their detection efficiencies for electrons 1,2 and ions. [2][3][4][5][6][7][8][9] Less well studied, however, is their detection efficiency for low energy neutral species. 10 This appears to be primarily due to the lack of facilities able to produce well-characterized, variable energy beams of neutral atoms or molecules.…”

Mars atmospheric losses induced by the solar wind: Comparison of observations with models

“…Post-flight laboratory tests of CEMs from the same party as ones flown on Mars-5 showed, that CEMs working in non-saturated mode had pulse-height distributions depending on the ion mass: heavier ions (O + and N + ) produce, on average, larger pulses than lighter ions (H + and He + ) Smirnov, 1984, Vaisberg, 1992a). Work with pulse discriminator makes this CEM crude mass-spectrometer (this mass-sensitive behavior of CEMs was confirmed by Fields et al, (1977).…”