JPS6121796Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a magnetic field type mass spectrometer. The primary purpose of the present invention is to increase the degree of freedom in designing the shape, size, and position of the deflecting magnetic field. By doing so, effects such as miniaturization and cost reduction of the mass spectrometer can be obtained. Another purpose of the present invention is to improve the ion focusing effect and increase the sensitivity.

Normally, in a magnetic field type mass spectrometer, the deflection magnetic field also serves as an ion focusing effect, but in this invention, the two effects of dispersion and focusing due to the ion mass number are separated, and dedicated means are used for each to focus the ions. This uses an electrostatic single-pole lens. When performing mass dispersion and ion focusing using a magnetic field, three points, the center of the sector of the magnetic field, the ion source, and the ion focusing point, are aligned in a straight line. Because of this relationship, the size and shape of the magnetic field, the arrangement of the ion source, and the ion focus point are specified, and there is no degree of freedom in design. By changing the conventional method of focusing ions using only a magnetic field, the arrangement of the ion source, magnetic field, and ion focusing point can be freely arranged, making the entire system linear and downsizing the entire mass spectrometer. Can be done. This invention is carried out in a mass spectrometer.
The deflection effect for mass dispersion is taken care of by the magnetic field,
The spectral image as an image of the entrance slit is formed by the electrostatic lens alone or by the cooperation of the electrostatic lens and the magnetic field. In other words, the deflection magnetic field itself exhibits a convergence effect that forms an image of the incident slit under appropriate conditions, but regardless of the inherent characteristics of such a magnetic field, in this invention, the ion convergence effect is borne not by the magnetic field but by the electrostatic lens. It is something that makes you
The present invention will be explained below with reference to Examples.

FIG. 1 shows an electrostatic monopole lens used in the present invention (shows a focusing effect on positive ions). a indicates the side and b indicates the front. The lens hole H is usually circular, but in this case it is an elongated hole. If you do it like this x
The strength of the lens differs in the y-direction and the y-direction, and the image of the point-like ion source has astigmatism and is long in the y-direction on the side close to the lens and long in the x-direction on the far side. This embodiment uses an image that is elongated in the y direction.

FIG. 2 exemplifies the arrangement relationship between the electrostatic lens described above and the deflection magnetic field. In the figures, the electrostatic lenses 1, 1' are shown in the form of optical lenses. 2 is the deflection magnetic field,
The ion input end face and the ion exit end face are parallel to each other. Figure 2a shows a condenser lens 1 inserted between the slit S1 on the ion source side and the magnetic field 2.
A parallel ion beam is incident on the ion beam. Since the incident side and the exit side of the magnetic field 2 are parallel, the ion beam flux after deflection also remains parallel, and is focused onto the slit S2 by the lens 1'. An ion detector is placed behind the slit S2. In Fig. 2b, an image of the ion source S1 is formed on the slit S2 using a single lens 1.
This configuration has a deflection magnetic field placed behind the lens 1. In this case, the ion flux incident on the magnetic field is convergent, so due to the action of the magnetic field 2, the convergence point is somewhat closer to the lens 1 than when there is no magnetic field. Now, lens 1
An image of ions of a specific mass in the slit S1 is formed on the slit S2 by the cooperative action of the ions and the magnetic field 2. Figure c shows a configuration in which the lens 1' is placed behind the deflection magnetic field 2. In this case, the ion flux incident on the magnetic field 2 is divergent, so due to the action of the magnetic field 2, the position of the slit S1 seen from the lens 1' is farther from the magnetic field 2 than the actual position, and therefore the lens 1' and the slit The distance to S2 is shorter than when no magnetic field is acting.

There is a quadrupole type electrostatic lens, and although this type of lens is relatively strong, it converges the ray bundle only in one plane that includes the optical axis, and diverges in the plane perpendicular to this plane. The ray flux converges into a long and thin strip on the slit in front of the ion detector, but because it converges for a length longer than the height of the slit, the ion utilization rate decreases. On the other hand, when a monopole lens is used as in the present invention, the ray flux converges almost equally in each direction, resulting in a good ion utilization rate, and the sensitivity can be improved while making the mass spectrometer smaller.

As mentioned above, the present invention uses an electrostatic lens to release the role of the magnetic field from the ion focusing effect, and the distance from the center position of the magnetic field to the slit S2 on the front side of the detector or the slit S1 on the ion source side is fixed. By using an electric lens, it can be shortened compared to a conventional mass spectrometer that uses only a magnetic field, and the restriction that the fan center of the fan-shaped magnetic field and the ion input/exit slit are aligned in a straight line in the conventional device is eliminated, and the overall device The effect of miniaturization can be obtained.

[Brief explanation of the drawing]

FIG. 1 shows an example of a monopolar electrostatic lens used in the present invention, and FIG. 2 is a plan view illustrating the arrangement relationship between the electrostatic lens and a deflection magnetic field. 1, 1'... Electrostatic lens, 2... Deflection magnetic field, S
1... Ion source side slit, S2... Ion detector front slit.

Claims (1)

[Scope of utility model registration request] The ion beam flux is made obliquely incident on the ion beam incidence end face of a magnetic field in which the entrance end face and the exit end face of the ion beam flux are parallel to each other, and both the entrance side space and the exit side space of the ion beam flux to the magnetic field, or A mass spectrometer in which a convergent electrostatic monopole lens is arranged on either one of the ion beams.