Radiant energy – Ionic separation or analysis – Static field-type ion path-bending selecting means
Patent
1991-12-02
1993-03-30
Berman, Jack I.
Radiant energy
Ionic separation or analysis
Static field-type ion path-bending selecting means
250305, 250396R, 250296, H01J 4902, H01J 4948
Patent
active
051986663
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a mass spectrometer incorporating an electrostatic ion energy analyzer and a multichannel focal-plane detector.
If the single channel detector of a conventional scanning type mass spectrometer is replaced by a multichannel detector disposed in the focal plane of the final analyzer it is possible to record more than one mass-to-charge ratio simultaneously and therefore increase the efficiency of the spectrometer In other words, more of the ions formed from the sample may be detected in a given time so that the sensitivity is increased. In practice, however, the advantage that can be obtained is usually well below expectations.
In a spectrometer incorporating a conventional sector type electrostatic analyzer, this is partly due to the limitations imposed on a multichannel detector by the sector analyzer. Firstly, because of the limited spacing between the electrodes, the extent of its focal plane is limited, so that the range of masses that can be simultaneously imaged is also limited. Secondly, the focal plane of a sector analyzer is not usually perpendicular to the direction of travel of the ions leaving it, but inclined at a shallow angle. This further limits the maximum extent of the spectrum which can be simultaneously recorded and complicates the design of the detector system. Further, because a conventional analyzer comprises only 2 electrodes, the electrostatic analyzing field is determined entirely by the shape of the electrodes. This means that the homogeneity of the field cannot be varied and the number of aberrations (eg focal plane tilt and curvature) which can be corrected is very limited. Similarly, although a greater portion of the spectrum can be transmitted by use of an analyzer with a wider gap, it is then necessary to increase the height of the plates to ensure that the field in the vicinity of the ion beram is sufficiently uniform, which results in a very large and prohibitively expensive analyzer.
Another limitation on performance is that the spacing between the channels on currently available multichannel detectors is such that it is not possible to record a complete high resolution spectrum on a detector of reasonable length. A variable dispersion mass spectrometer which can image on the same detector either a small portion of the spectrum at high resolution or a larger portion at Iow resolution is therefore desirable, but because dispersion is determined by the geometrical parameters of the analyzers this is not easily implemented, especially if accurate double-focusing is to be achieved at all dispersions. One solution to this problem, proposed in PCT application publication number 89/12315, is an arrangement wherein the magnification of the electrostatic analyzer is substantially zero, which permits the use of a "variable radius" electrostatic analyzer while maintaining double focusing, thereby allowing the dispersion to be changed.
Very few electrostatic analyzers are known which do not rely on the field generated between two accurately shaped electrodes to define the energy dispersing field. Auxiliary electrodes are used in prior analyzers to compensate for the effect of fringing fields where the charged-particle beam enters and leaves the analyzer, but these do not define the main analyzing field. In these analyzers, one or more electrodes are provided at the entrance and exit of the analyzer and are maintained at potentials such that the field between the main electrodes is maintained as close as possible to the ideal field (eg, a 1/r field in the case of a cylindrical sector analyzer). Similar fringing-field corrector electrodes may be provided around the edges of a parallel-plate analyzer, (see, for example, Stolterfoht in DE2648466 A1).
Matsuda (Rev. Sci. Instrum. 1961, vol 32(7), pp 850-852) has described a variable focal length cylindrical sector analyzer which comprises a pair of conventional sector electrodes and a pair of planar auxiliary electrodes, respectively disposed. Above and below the sector electrodes (ie, displaced along the "z" axis)
REFERENCES:
patent: 3407323 (1968-10-01), Hand
patent: 3636345 (1972-01-01), Hirschel
patent: 4912326 (1990-03-01), Naito
Matsuda, "Electrostatic Analyzer with Variable Focal Length", published on The Review of Scientific Instruments 1961 vol. 32 (7) pp. 850-852.
Matsuda, "Electric Field In Cylinder Condensers of Finite Length", published on International Journal of Mass Spectrometry and Ions Physics, 22 (1976) pp. 95-102.
Zashkvara, Korsunshii, "An Electrostatic Analyzer with Electrodes On Which The Potential Is Linearly Distributed", published on Soviet Physics-Technical Physics 1963 vol. 7 (7) pp. 614-619.
Dymovich, Sysoev, "Calculation and Some Ion-Optical Characteristics of an Electrostatic Focussing System", published on Physical Electronics (Moscow) 1965, vol. 2, pp. 15-26, an English translation is enclosed.
Dymovich, Sysoev, "Calculation of the Field of an Electrostatic Focussing System and Modelling in an Electrolytic Bath", published on Physical Electronics (Moscow) 1965, vol. 2, pp. 27-32, an English translation is enclosed.
Dymovich, Dorofeev, Petrov, "Triple Focusing Crossed Field Mass Spectrometer", published on Physical Electronics (Moscow) 1966 vol. 3, pp. 66-75, an English translation is enclosed.
Daukeev, Karetskaya, Kasymov, Kelman, Mit.sup.1, Saichenko, Shevelev, "Secondary-ion mass spectrometer", published on Soviet Physics Technical Physics Mar. 1985, No. 3, Woodbury, N.Y., USA.
Curtis, Hsieh, "Compact Wide-Aperture Hyperbolic Analyzers", published on Review of Scientific Instruments 59 (1988) Nov., No. 11, New York, NY, USA.
Gibson, Reid, "A Modified Fountain Spectrometer for Measuring Double Differential Cross Sections in Ion-atom collisions", published on J. Phys. E: Sci Instrum., vol. 17, 1984, pp. 1227-1230.
Kelman, Rodnikova, Finogenov, "Prism Mass Spectrometer With Energy Focusing", published on Soviet Physics-Technical Physics 1971 vol. 16 (1) pp. 130-135.
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