The Development of Laboratory Ion Sources for Mass Spectrometer Calibration
Abstract
Electron impact ion sources were developed for the purpose of quadrupole mass spectrometer calibration in the laboratory. Prototype ion sources were constructed, and tested for operation in both positive and negative ion modes. In the positive mode, sensitivities approaching 10 (exp-3) A/torr were obtained at the highest filament currents tested. Ion currents were linear over an order of magnitude in pressure. Collected ion currents generally increased with electron energy, following somewhat the trend with total ionization cross section. The results of energy analysis of the ion beams are consistent with Gaussian beams with relatively wide variances. Typical beam energies peaked in the regime of 30-35V, with variances of 17-18V. The ion beams did not appear to be fully accelerated at the analyzing electrode. The beams generally seemed to become more Gaussian with reduced variances at the lower electron energies. The use of magnets did not noticeably improve ion source performance in the positive ion mode. However, it did eliminate a significant background current problem at the collector plate. In the negative ion mode, total collected negative ion currents using SF6 were approximately two orders of magnitude less than under comparable conditions in the positive ion mode.
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 01, 1993
- Accession Number
- ADA282041
Entities
People
- J. M. Calo
- W. D. Lilly
Organizations
- Brown University