Advertisement

Journal of Analytical Chemistry

, Volume 73, Issue 13, pp 1282–1291 | Cite as

Development of a System for Measuring and Recording Ion Currents for an MI-1201IG Mass Spectrometer

  • V. V. Kolobov
  • V. N. Selivanov
  • M. B. BarannikEmail author
ARTICLES
  • 20 Downloads

Abstract

In the complex modernization of an MI-1201IG isotope mass spectrometer, a new system for measuring and recording ion currents was developed, including an electrometric amplifier based on a high-resistivity (1 TΩ) feedback resistor and a special chip located in the electrometer head. A recording circuit based on a high-precision analog-to-digital converter was included in the new unit for controlling the separating magnetic field and measuring the ion current. In designing the system circuit, the task was not only to increase the sensitivity and expand the dynamic range when measuring the intensity of peaks in mass spectra but also to decrease the time constant of the analog part of the measuring system for the undistorted transfer of the ion current distribution form to the input of the analog-to-digital converter in a dynamic mode. A shielding system was designed that distributes the electric field gradient on the surface of a high-resistivity feedback resistor, which made it possible to compensate its distributed capacitance and decrease the time constant of the electrometric amplifier to 0.2 s. To compensate for the distortion of the shape of the ion current pulses, caused by the in-to-out stray capacitance of the electrometer’s amplifier chip, a special circuit was developed. This results in that the end-to-end frequency response of the new system for measuring and detecting ion currents is determined only by the upper cut-off frequency of the low-pass filters of 10 Hz. The high-speed measuring system made it possible to improve the mass-spectrometric resolution and mass accuracy and to increase full-spectrum scan rate. The working range of the new system for measuring and recording ion currents is 1 × 10–15 to 3 × 10–12 A. The measured equivalent root-mean-square input noise is 0.86 fA at the sampling frequency of 10 Hz and the integration time of 1 s and 0.14 fA at the integration time of 10 s.

Keywords:

MI-1201IG mass spectrometer electrometric amplifier high-resistivity feedback resistor distributed capacitance shielding rings system full-scan mode time constant analog-to-digital converter 

Notes

REFERENCES

  1. 1.
    Shubin, V.M., Manoilov, V.V, Zarutskii, I.V., and Voronin, B.M., Nauchn. Priborostr., 2003, vol. 13, no. 2, p. 64.Google Scholar
  2. 2.
    Saprygin, A.V., Kalashnikov, V.A., Zalesov, Yu.N., and Shvetsov, S.I., Mass-Spektrom., 2006, vol. 3, no. 3, p. 201.Google Scholar
  3. 3.
    Ivanov, V.P., Moiseeva, T.G., Trofimov, A.S., Dryannov, A.I., Sysoev, A.A., and Sysoev, A.A., Instrum. Exp. Tech., 2005, vol. 48, no. 3, p. 321.CrossRefGoogle Scholar
  4. 4.
    Gudkov, A.V., Kamensky, I.L., Melikhova, G.S., Skiba, V.I., Tokarev, I.V., and Tolstikhin, I.N., Geochem. Int., 2014, vol. 52, no. 7, p. 587.CrossRefGoogle Scholar
  5. 5.
    Anso, M.Kh., Cand. Sci. (Tech.) Dissertation, Tartu: Tartu State Univ., 1984.Google Scholar
  6. 6.
    Bondarenko, I.B., Elektroradioelementy (Electroradiolements), part 1: Rezistory (Resistors), St. Petersburg: St. Petersburg. Nats. Issled. Univ. Inf. Tekhnol. Mekh. Opt., 2012.Google Scholar
  7. 7.
    Finite Element Method Magnetics. http://www.femm. info/wiki/HomePage. Accessed July 14, 2017.Google Scholar

Copyright information

© Pleiades Publishing, Inc. 2018

Authors and Affiliations

  • V. V. Kolobov
    • 1
  • V. N. Selivanov
    • 1
  • M. B. Barannik
    • 1
    Email author
  1. 1.Center for Physical and Technological Problems of Energy in Northern Areas, Kola Science Center, Russian Academy of SciencesApatityRussia

Personalised recommendations