Radiofrequency Mass Spectrometer

Abstract

A mass spectrometer tube using velocity selection is described. The tube has parallel plane grids made with knitted wire nets with a large percentage of open area. The grids are arranged in groups of three, and radiofrequency alternating potential is applied to the middle grid of each group. Stopping potentials are used to turn back all ions except those with the selected mass. The spectrometer has sufficient resolution for ordinary gas analysis requirements and is simpler, more compact, and more rugged than magnetic beam deflection devices.

The effects of IMF and convection on thermal ion outflow in magnetosphere-ionosphere coupling

“…The SMS is a three-stage, folded, Bennett-type (Bennett, 1950) radiofrequency mass spectrometer equipped with a retarding potential analyzer (RPA) that was designed to measure thermal (0.1-25 eV/q) and suprathermal (25-4000 eV/q) ion distributions in the 0.9-67 amu/q mass-per-charge range (Whalen et al, 1990). It samples ions perpendicular to the Sun-Earth line and in the satellite spin plane, and dynamically selects one of three entrance apertures based on the measured plasma density.…”

Magnetic resonance and radio frequency mass spectrometers and their application

“…The analysis conducted in Ref. [10] yielded the same result as obtained by Bennett [12] for the case of acceleration of an ion beam moving in a straight line by a sine voltage applied to the central grid of the double-gap modulator. In this case:…”

“…This analysis ended with a significant conclusion, namely, that the theory of modulation of an ion beam in a cyclotron instrument is strictly correct only for 0 , i.e., that the increment of velocity gained in the course of modulation should be significantly smaller than the velocity itself, the condition used by Bennett in a linear instrument [12]. In cases where this inequality fails in properly operating cyclotron instruments, the shape of the modulation curve is not strictly sinusoidal and is different in the first and second accelerations.…”

The radiofrequency mass spectrometer as an analogue to the optical grating

“…A single rf stage of length 2s produces an energy gain E (~j that is, in turn, a periodic function of the frequency f with the ion velocity v as parameter, exhibiting (~minima)) at frequencies 1) f=k--(k=l, 2, ...)…”