Non-Converging Field and Mass Spectrograph

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概要

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• Ion optical properties of the sector type fields which diverge ion beam (diverging field) and of those which have no lens action but have dispersive action (dispersing field) are discussed. If the magnetic field is expressed as H<SUB>z</SUB>=H<SUB>o</SUB>r<SUP>n</SUP> and electric field as E<SUB>r</SUB>=E<SUB>o</SUB>r<SUP>l</SUP> approximately, then the field with n<-1 or l<-3 is diverging field, and that with n=-1 or l =-3 is dispersing field.<BR> Diverging field forms the virtual image and the dispersion at the virtual image is given by(a/k<SUP>2</SUP>) (X-1)δ', where a is the mean radius, k<SUP>2</SUP>=-(n+1)or-(l+3), X the magnification and δ'=γ+β (magnetic field) or γ+2β (electric field) .(γ and β are fractions of mass and velocity respectively.) A very small single focus mass spectrometer is proposed by combining 60° magnetic diverging field (k=1) and electric quadrupole lens in tandem, and a very small double focus mass spectrometer is designed by the combination of the 60 ° electric diverging field (k=1) and the 60 ° uniform magnetic field. These mass spectrometers are about one half in size compared with the ordinary mass spectrometers with the same resolving power.<BR> The dispersive action of the dispersing field is analogous to the optical prism. The dispersion angle is given by Φδ', where Φ is the deflection angle of the field, and is independent of the radius. When the ordinary sector type analyzer is separated in two at the point where ion beam becomes parallel and the dispersing field is inserted between them, the total dispersion and resolving power is increased several times but the total size of the apparatus does not become so large. For example, when 315 ° dispersing magnetic field is inserted between 30°-30° uniform magnetic fields, both dispersion and resolving power are increased about 6.5 times as large as those of the 60° uniform magnetic field of the same radius.<BR> Double focusing mass spectrograph with the resolving power of the order of 10<SUP>7</SUP> is designed by using the above principle. This apparatus consists of toroidal electric field, γ<SUP>-1</SUP>magnetic field and uniform magnetic field and the total ion path is less than 10 m.<BR> The ion orbit in the above fields is also calculated in the second order approximation.

• 日本質量分析学会の論文

著者

• 松田 久

  大阪大学教養

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• Non-Converging Field and Mass Spectrograph

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