Electron Flood Charge Compensation Device for Ion Trap Secondary Ion Mass Spectrometry

Journal Article · Fri Nov 01 04:00:00 EST 2002 · International Journal of Mass Spectrometry

DOI:https://doi.org/10.1016/S1387-3806(02)00892-8· OSTI ID:912015

Appelhans, Anthony David; Ward, Michael Blair; Olson, John Eric

During secondary ion mass spectrometry (SIMS) analyses of organophosphorous compounds adsorbed onto soils, the measured anion signals were lower than expected and it was hypothesized that the low signals could be due to sample charging. An electron flood gun was designed, constructed and used to investigate sample charging of these and other sample types. The flood gun was integrated into one end cap of an ion trap secondary ion mass spectrometer and the design maintained the geometry of the self-stabilizing extraction optics used in this instrument. The SIMION ion optics program was used to design the flood gun, and experimental results agreed with the predicted performance. Results showed the low anion signals from the soils were not due to sample charging. Other insulating and conducting samples were tested using both a ReO4- and a Cs+ primary ion beam. The proximity of the sample and electron source to the ion trap aperture resulted in generation of background ions in the ion trap via electron impact (EI) ionization during the period the electron gun was flooding the sample region. When using the electron gun with the ReO4- primary beam, the required electron current was low enough that the EI background was negligible; however, the high electron flood current required with the Cs+ beam produced background EI ions that degraded the quality of the mass spectra. The consequences of the EI produced cations will have to be evaluated on a sample-by-sample basis when using electron flood. It was shown that the electron flood gun could be intentionally operated to produce EI spectra in this instrument. This offers the opportunity to measure, nearly simultaneously, species evaporating from a sample, via EI, and species bound to the surface, via SIMS.

• Research Organization: Idaho National Laboratory (INL)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC07-99ID13727
• OSTI ID: 912015
• Report Number(s): INEEL/JOU-02-00548
• Journal Information: International Journal of Mass Spectrometry, Journal Name: International Journal of Mass Spectrometry Journal Issue: 1 Vol. 221; ISSN 1387-3806
• Country of Publication: United States
• Language: English

Related Subjects

99 GENERAL AND MISCELLANEOUS
ANIONS
APERTURES
CATIONS
ELECTRON GUNS
ELECTRON SOURCES
ELECTRONS
FLOODS
GEOMETRY
ION BEAMS
IONIZATION
MASS SPECTRA
MASS SPECTROMETERS
MASS SPECTROSCOPY
OPTICS
SIMION
SIMS
SOILS
SPECTRA
electron flood
quadrupole ion trap
sample charging
secondry ion mass spectrometry
simulation