SU974458A1 - Prizm mass spectrometer - Google Patents

Description

(54 PRISM MASS SPECTROMETER

one

This invention relates to mass spectral instrumentation. Characteristic signs of prism-:

devices is the presence of a two-dimensional magnetic prism deflecting those of a forest copy. systems and two lenses, collimator and focusing (in particular, transaxial lenses; in whose focal planes are placed the targets of the source and receiver of ions. The magnetic prism performs the role of the dispersing element, and achromatization is achieved by using an elec- tric-lens-lens system in the ion-optical scheme 1 Known devices characterize; with insufficient accommodation and luminosity.

 The closest to the invention in its technical essence is a prism mass spectrometer containing ion detector sources, two electrostatic lenses and two deflecting telescopic electrostatic systems, between which a magnetic telescopic system is located, which is a magnetic prism with a two-dimensional magnetic field 2

This device has a significant resolution and luminosity, but a further increase in its dispersion, and hence resolution, due to the limited angular dispersion of the magnetic prism, can only be achieved by increasing the length of the spectrometer arms (focal length of the collimator and focusing transaxial lenses) , which in turn leads to a significant decrease in the aperture of the device, the value of which in a symmetric version

15 is inversely proportional, and the square of Dina his shoulders. In addition, the total angle of deflection of ions in the magnetic dispersion system is small, as a result of which the instrument appears

20 non-compact - stretched in one direction.

: The purpose of the invention is to increase the dispersion of the resolution of a prism mass spectrometer without

25 reducing its luminosity, as well as reducing the overall dimensions of the device.

This goal is achieved by the fact that in a prism mass spectrometer,

30 containing an ion source and receiver two electrostatic lenses and two deflecting telescopic electrostatic systems, between which there is a magnetic dispersing system, the dispersing system is made in the form of an electromagnet with three pairs, poles, each of which is a two-dimensional magnetic field . The drawing shows schematically the proposed mass spectrometer. general view and course of the ion trajectories projected on the middle plane, The slot of the ion source 1 is located in the focal plane of the collimator electrostatic immersion lens 2 (the figure shows a transaxial electrostatic lens). Behind this lens at an angle V. to the beam axis, the first electrostatic telescopic system 3 is marked. Due to the potential difference between the extreme electrodes of the electrostatic telescopic system, the angles V2 and V between the beam axis and the normal to the faces of the telescopic system are different. The extreme {on the side of the ion source) electrode of the focusing lens 2 and the extreme {on the side of the magnetic dispersing system) electrode of the electrostatic telescopic system is located under the potential of the Earth Vt, corresponding to the ion energy - eV, {The potential is normalized so that it is equal to zero, where it is zero particle energy). The potential on the cp, unit of the electrode of lens 2 is calculated based on solving the corresponding equations of motion so that the focal plane of the lens is aligned with the slit plane of the ion source 1 e. The potential on the middle electrode of the electrostatic telescopic system is calculated so as to satisfy its telescopic condition. The potential W on the common for the lens and the electrostatic telescopic electrode system, the angle V and the angle (/ - of the entrance of the beam to each Prism of the magnetic dispersion system must satisfy the equality V (3- + 3tg s. CtgM YV,. Second electrostatic telescopic system 3, the adjacent fs5-cusping lens 4 and the ion detector slit 5 are in the same relationship with the ruptured interconnection as the source1 and the electrodes.The magnetic dispersing system is located between the first and second electrostatic systems; 3. Unlike prototype she performed An an electric magnet b comprising three pairs of pole jaws, having a common PM 7 and an excitation coil 8. Each pair of pole pieces is a magnetic prism with a two-dimensional field. The angle of entry af of the ion beam into the magnetic prism is chosen based on the requirement Telescopicity. Compliance with the conditions for the telescopicity of electrostatic and magnetic elements of prism spectrometers provides triple focusing of beam a, ionized ions. Depending on the design features of the magnetic prisms, the angle di may be 49 ° -. This determines the choice of the magnetic dispersion system of the proposed spectrometer, consisting precisely of three magnetic prisms. In this case, the axis of the collimator and focusing lenses can be directed in one direction, which ensures the greatest compactness of the device. The spectrometer works as follows. The diverging ion beam emerging from each POINT slit of source 1 is converted into a parallel beam of a collimator transaxial lens 2 operating anamorphic, and deviating in the first electrostatic telescopic system 3, decomposes in energy and then passes three magnetic prisms to dispergulate thereafter. electromagnet 6. Magnetic prisms are angled. to each other 49 - a SPZ, each of which is a magnetic telescopic system 9 with a linear focus in the middle. The parallel ion beam entering the dispersing beam, due to the telescopicity of the magnetic prisms, remains parallel between and after the prisms. After the passage of the second electrostatic telescopic system 3, a beam of particles, the direction of motion of which does not depend on the energy of these particles, but is determined by their specific charge, is focused by a transaxial focusing lens 4, also operating in the anamorphic mode, into the ion receiver slot 5. focal plane of this lens. The mass dispersion of the beam is carried out by a system of three magnetic prisms, as a result of which the value of the dispersion and resolution of the device increases three times as compared with the prototype in accordance with the equality cos Va. where f is the focal length of the transaxial lens. At the same time, the luminosity of the proposed device remains unchanged at the same size as the prototype of the sizes of deflecting and focusing elements and focal lengths.

Claims (2)

Claim A prism mass spectrometer containing an ion source and receiver, two electrostatic lenses and two deflecting telescopic electrostatic systems, between which a magnetic dispersing system is located, characterized by 5 in that, in order to increase the resolution and aperture of the mass spectrometer, as well as reduce its overall dimensions, the magnetic dispersion system is made in the form of 10 electromagnets with three pairs of poles, each of which is a magnetic prism with a two-dimensional field. 15 Sources of information taken into account in the examination of JL. CCQP Copyright 353186, CL H 01 j 49/32, 1972. ¹ 2. Kelman V.M., Nazarenko L.M. Yakushev E.M. Prism mass spectrometer. ZhTF, 1976, 46, p. 1700 (prototype). f Branch of PPP Patent, Uzhhorod, Project 4,