High-sensitivity Mass Spectrometry Research Articles

Electronic system for high sensitivity and high stability mass spectrometry: Part III: New electronic arrangement for high precision in the determination of isotopic abundances

We continue the preceding work [1, 2] with many improvements in order to obtain high precision in the isotopic abundance determination of very small quantities of products by ion counting detection.

An Ion Counting Method with Multichannel Pulse Height Analyser for High Sensitive Mass Spectrometry

A newly developed ion counting method in mass spectrometry is described. This method makes use of analog switch, so as to make the output pulse height from the secondary electron multiplier linear in (m/e)1/2 of the ions. When fed to a multichannel pulse height analyser (MC-PHA), these output pulses produce a histogram which directly represents the mass spectrum. The new method makes possible a rapid scanning of the magnetic field in a mass-spectrometer. In order to overcome problems of counting loss of ions, which is caused mainly by MCPHA, it is required to change the accumulation rate of pulses in MCPHA especially for the most abundant isotopes. For this purpose, we designed a “window sensitivity attenuator", in which the incoming rate of ions to the electron multiplier is converted into its 1/2n by using a series of binary counters. The new counting method was applied to the isotopic measurement on magnesium with samples of inclusions of the Allende Meteorite, and the results are presented.

Electronic system for high sensitivity and high stability mass spectrometry: Part II. Electronic set-up for an “on-line” mass spectrometer

An electronic set up was established for the study of very short-lived (> 10 μs) isotopes arising from nuclear reactions. This was done by using a mass spectrometer on-line with an accelerator's beam.

Electronic system for high sensitivity and high stability mass spectrometry: Part I. Electronic set up for an “off-line” mass spectrometer

We describe an electronic set up giving very high sensitivity to a mass spectrometer. This sensitivity allows the detection of one ion per minute at the collector. Mass scanning is implemented by a staircase-shaped variation of the accelerating voltage, synchronized with the gating of a multiscaler. The performance shows the very good stability of the assembly.

Mass spectrometric analysis of gas inclusions in Muong Nong glass and Libyan Desert glass

Noble and non-noble gases in bubbles of Muong Nong- and Libyan Desert glass were released by vacuum crushing at room temperature and measured by high sensitivity mass spectrometry. The N 2:Ar:Kr:Xe ratio as well as the rare gas isotope ratios were found to be atmospheric, indicating the terrestrial origin of these glasses. The concentrations of the active gases O 2, CO 2, CO and SO 2 vary highly between adjacent bubbles. Total gas pressure in the bubbles of the glasses is in the 100 mm range, much higher than that found for other types of tektites.

Mass-Spectrometric Search for Neon and Argon Isotopes in Ternary Fission ofU235

We have carried out a search for neon and argon isotopes produced in ternary fission of $^{235}\mathrm{U}$, using high-sensitivity mass spectrometry. The following upper limits - expressed in atoms per binary fission - were obtained: $^{20}\mathrm{Ne}$ 5.8 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}8}$, $^{21}\mathrm{Ne}$ 3.4 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}10}$, $^{22}\mathrm{Ne}$ 5.9 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}9}$, $^{36}\mathrm{Ar}$ 2.4 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}9}$, $^{37}\mathrm{Ar}$ 2.2 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}9}$, $^{38}\mathrm{Ar}$ 2.0 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}9}$, $^{39}\mathrm{Ar}$ 7.8 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}10}$, $^{40}\mathrm{Ar}$ 6.9 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}7}$, $^{42}\mathrm{Ar}$ 2.2 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}9}$. Except in the case of $^{40}\mathrm{Ar}$, these limits are lower by 1 to 4 orders of magnitude than indicated from results of triple-coincidence experiments carried out by previous workers. Assuming unique formation of $^{40}\mathrm{Ar}$, the upper limit for this nuclide is a factor of 5 lower than the triple-coincidence frequency.

Mass Spectrometer Systems for Isotope Geochemistry(1). High Sensitivity Mass Spectrometry of Rare Gases by a System with a Getter Ion Pump

Mass Spectrometer Systems for Isotope Geochemistry(1). High Sensitivity Mass Spectrometry of Rare Gases by a System with a Getter Ion Pump