Radio-Frequency Ion Guides with Periodical Electrodes and Pulse Voltages
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Radio-Frequency Ion Guides with Periodical Electrodes and Pulse Voltages A. S. Berdnikova, *, A. N. Verenchikovb, N. R. Galla, c, A. G. Kuzmina, S. V. Masyukevicha, M. N. Lapushkinc, and Yu. A. Titova aInstitute
for Analytical Instrumentation, Russian Academy of Sciences, St. Petersburg, 190103 Russia b MSC-CG (Mass Spectrometry Consulting), Bar, 85000 Montenegro c Ioffe Institute, Russian Academy of Sciences, St. Petersburg, 194021 Russia *e-mail: [email protected] Received August 6, 2019; revised October 9, 2019
Abstract—We consider radio-frequency ion guides formed by electrodes, which are periodic sequences of circular apertures. With the help of pulse voltages arranged as trains of a special type, a relay-switched sequence of axial distributions of the pseudopotential can be organized along the axis of the system in the form of space waves with alternating maxima and minima, which convey charged particles along the conveying channel. The disadvantage of the proposed conveying technology is the obligatory presence of neutral gas in moderate amounts, which dampens the excess kinetic energy acquired by charged particles in the jump-like switching of the radio-frequency electric field. An advantage of the proposed conveying technology is the simplified form of radio-frequency voltages applied to the electrodes of the device and the flexible control of the guiding velocity in Gas Chromatography–Mass Spectrometry interfaces, for example. Keywords: mass spectrometric devices, radio-frequency electric fields, pulse voltages, ion guides, pseudopotentials, T-WaveTM, A-Wave DOI: 10.1134/S1061934820140063
INTRODUCTION In present-day mass spectrometry, ion-optical devices based on the motion of charged particles in radio-frequency fields, including in gas-filled systems, play an essential role. These devices include, for example, ion traps, quadrupole mass analyzers, gasfilled cooling cells, radio-frequency ion funnels, and other types of ion guide systems [1–9]. These or similar devices are found in all commercial or experimental atmospheric pressure ionization mass spectrometers, and their performance largely determines the analytical parameters of the instrument. The behavior of charged particles in radio-frequency electric fields can be approximately investigated using the theory of pseudopotential, which is a useful and intuitively transparent tool for a qualitative description of the features of motion of charged particles in such systems [10–25]. In particular, radio-frequency traps with periodic electrodes shaped as circular apertures [26–31] and conveying systems based on the Archimedean radio frequency wave (A-Wave) [32–51] operate on the basis of the pseudopotential theory. Axisymmetric radio-frequency traps with periodically positioned electrodes with circular diaphragms (also called stacked ring ion guides (SRIG) and ring
electrode traps (RET)) are widely used in mass spectrometry. They were first proposed in 1969 as an alternative to conventional ion traps [26], then they were modified to perform the f
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