JPS643025B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic field deflection type mass spectrometer.
A type of mass spectrometer that scans mass numbers by changing the strength of a magnetic field has the disadvantage that the speed of mass number scanning cannot be very fast.

The present invention is a magnetic field deflection type mass spectrometer, comprising:
Furthermore, the present invention aims to provide a mass spectrometer that can scan mass numbers at high speed.

The mass spectrometer of the present invention keeps the intensity of the magnetic field for mass dispersion constant over time, forms electric fields that deflect ion trajectories on either or both sides of the ion incidence side and the ion exit side of the magnetic field. Mass number scanning is performed by changing the electric field. The present invention will be explained below with reference to Examples.

In FIG. 1, numeral 1 indicates the trajectory of an ion incident on a mass dispersion magnetic field, and 2 indicates a magnetic pole end face of a magnet forming the mass dispersion magnetic field. In the mass dispersion magnetic field, A is the ion entrance end face, B is the ion exit end face, and they intersect at an angle of 135° with the ion incidence point 0 in between.
The ion beam 1 is incident perpendicularly to the incident end surface A, and the ions advance through the magnetic field in a circular orbit, forming the incident beam 1.
It exits from the injection end face B after being deflected by 90°. The orbital radius r of an ion in a magnetic field is given by Br=143.9√, where B is the strength of the magnetic field, M is the mass number of the ion, and V is the ion acceleration voltage. In the figure, r1 is the orbital radius of the ion with the minimum mass number within the analyzable mass number range, and r2 is the orbital radius of the ion with the maximum mass number.

A flat plate electrode 3 is arranged facing and parallel to the exit end face B of the mass dispersion magnetic field, and a flat plate electrode 2' is arranged to extend the exit end face B to the right, and the magnetic field forming magnet 2 Both the plate electrode 2' and the plate electrode 2' are grounded and have a potential of 0, and a potential of U volt is applied to the electrode 3, so that an electric field is formed in the vertical direction in the figure. An electrode 4 is located between the electrodes 2, 2' and 3 to prevent disturbance of the electric field near the electrode ends. The ions are ejected into the space between the electrodes 2, 2' and 3 at an angle of 45° from the exit end face B of the magnetic field.
It is bent downward by the electric field there, follows a parabolic trajectory, and collides with the electrode 2'. Ions enter the magnetic field from point 0 and are ejected into the electric field from the exit end surface B between points P1 and P2 depending on their mass number. These ions can be made to reach the 0' point one after another by changing the voltage U between the electrodes 2, 2' and 3. The electrode plate 2' is provided with a window W at the 0' point, so that ions that have reached the 0' point enter an electron multiplier 5 for ion detection and are detected. Generally, if the distance between the ion emission point from the magnetic field emission end surface B and the 0' point is x, the strength of the electric field between electrodes 2, 2' and 3 is E, and the ion acceleration voltage is V. , x=2V/E or E=2V/x. Letting the distance between 0 point and 0' be L, the distance x from the emission point of the ion in the same magnetic field to 0', which has drawn a circular orbit of radius r in the resource dispersion magnetic field, is (L
-√2r), and since r is given by 143.9√, x=L−203.5√/B=2V/E. By continuously changing E from the above formula (magnetic field B and ion acceleration voltage V remain fixed)
The mass number of ions reaching the 0′ point can be changed continuously. That is, by changing the voltage U applied between the electrodes 2, 2' and 3, the mass number can be scanned.

FIG. 2 shows another embodiment of the invention. Reference numeral 2 denotes a magnetic pole end face of a magnet that creates a magnetic field for mass dispersion, 2 and 3 represent parallel plate electrodes facing each other, and the apex of the pole end face 2 is in contact with the flat plate electrode 2', and the electrode 2' is grounded and the electrode 3' is in contact with the flat plate electrode 2'.
A voltage U is given to . 1 is an incident ion beam, and ions are accelerated by an acceleration voltage V. The ion beam 1 enters the electric field between the electrodes 2' and 3 at an angle of 45 degrees with respect to the plate electrode 2', forms a parabola, and exits again above the electrode 2' (in the figure). A slit is cut in the electrode plate 2' along the plane of the drawing so that ions can freely enter and exit between the electrodes 2' and 3. The parabola drawn by an ion in an electric field will be the same parabola regardless of its mass number if the ion's charge and kinetic energy are the same.In this case, since the ion accelerating voltage is constant, the ion is incident for a certain interelectrode voltage U. The parabola drawn by the ion is one. The parabolic ions exit above the electrode plate 2' at an angle of 45 degrees with respect to the electrode plate 2', and then enter the magnetic field created by the mass dispersion magnet 2. This magnetic field has a triangular shape with an apex angle of 90° as shown in the figure, and ions with a specific mass number among the incident ions are located at the incident end face A of the magnetic field.
The light enters the magnetic field perpendicularly to the direction of the magnetic field, moves in a circular orbit of 1/4 circumference, is ejected from the magnetic field perpendicularly to the exit end face B, and enters the electric field between the electrodes 2 and 3 again. Since the kinetic energy of the ion remains unchanged, the ion again draws a parabola of the same shape as the one previously drawn and exits again and again to the upper side of the electrode plate 2' at the fixed point 0'.
By sweeping the voltage U applied between the electrodes 2' and 3, it is possible to draw the trajectory shown in the figure a for ions with a small mass number, and the trajectory shown in the figure b for ions with a large mass number. Ions of each mass number can be made to sequentially enter the ion detector 5, and mass numbers can be scanned using a mass number dispersion magnetic field with a constant magnetic field strength.

As described above, the mass spectrometer of the present invention performs mass number scanning by keeping the strength of the magnetic field for mass number dispersion constant and changing the electric field for deflecting ion orbits, so that high-speed scanning is possible.

[Brief explanation of drawings]

FIG. 1 is a plan view of one embodiment of the invention, and FIG. 2 is a plan view of another embodiment of the invention. DESCRIPTION OF SYMBOLS 1...Incoming ion beam, 2...Pole end face of a magnet forming a magnetic field for mass dispersion, 2', 3...Parallel plate electrode, 5...Ion detector.

Claims (1)

[Claims] 1 A mass spectrum having a mass dispersion magnetic field of constant strength and an ion trajectory deflection/focusing electric field formed in a space on at least the ion exit side of the ion entrance and ion exit sides of the same magnetic field, and formed by the above magnetic field. The image is re-imaged by the electric field, and the intensity of the electric field is changed so that the spectral image re-imaged by the electric field is moved along the image plane in front of the ion detector. A mass spectrometer that allows a mass of ions to enter an ion detector.