M.V. Dubkov  - Dr.Sc. (Eng.), Associate Professor, Head of Department of General and Experimental Physics

M.A. Burobin - Ph.D. (Eng.), Associate Professor, Deputy Head of Department of General and Experimental Physics

V.V. Ivanov - Ph.D. (Eng.), Associate Professor of Department of General and Experimental Physics

A.E. Malyutin - Ph.D. (Phys.-Math.), Associate Professor of Department of General and Experimental Physics

This work is devoted to finding ways to improve the analytical characteristics of the quadrupole mass filter (QFM), in particular, to increase its resolution. The quadrupole mass filter combines good analytical characteristics, fairly small dimensions, low production costs, and the ability to conduct continuous analysis. In practice, the resolution of the QMF is limited by the influence of the length of the electrode system, the energy of the introduced ion flux, and the presence of unstable ions with small initial coordinates that fall into the detector. Thus, the exclusion already at the entrance to the mass analyzer of ions with small initial coordinates can lead to an increase in resolution and, accordingly, selective properties of QMF. The implementation of the proposed method is associated with the mechanical limitation of the region of input of charged particles into the QMF electrode system.

In this work, the authors propose to close part of the inlet of the mass analyzer with an opaque screen of a certain width, which will limit the input of ions with small initial coordinates. To check the effect of such a screen on the QMF analytical characteristics, mass peaks were calculated and the main analytical characteristics were evaluated: resolution, intensity and quality factor of the mass peak.

The calculations showed that the use of a screen restricting the input of ions with small Y-coordinates leads to a 1.4-fold increase in resolution with a decrease in peak intensity. In this case, a small screen, whose width is 0.005 of the field radius r0, allows you to increase the resolution by 20% without changing the quality factor, defined as the product of the resolution and the intensity of the mass peak. The introduction of a similar screen bounding particles with small X-coordinates does not lead to any significant positive effects. The most promising turned out to be the use of a more complex cross-shaped screen, which ensures the simultaneous elimination of unstable particles with small X- and Y-coordinates. So the introduction of a crosswise screen with a width of 0.04r0 allows up to two times to increase the resolution.

Dubkov M.V., Burobin M.A., Ivanov V.V., Malyutin A.E. Influence of conditions for entering charged particles into the analyzer of the quadrupole mass filter. Radiotekhnika.2020. V.84. № 11(21). P. 23−29. DOI: 10.18127/j00338486-202011(21)-03 (In Russian).

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