JPH0789476B2 - Time-of-flight mass spectrometer - Google Patents

Description

TECHNICAL FIELD The present invention relates to a time-of-flight mass spectrometer that mainly uses laser light for ionization.

(B) Conventional technology and its problems Generally, in a time-of-flight mass spectrometer, when a sample is excited by a laser beam or the like to be ionized and then the ions are accelerated and emitted into a space, the ions are separated by a certain distance. Since the flight time differs depending on the mass number of each, the phenomenon contained in the sample is identified and quantitatively analyzed by utilizing this phenomenon.

By the way, laser light and plasma ions are used to ionize the sample. In particular, there is a conventional time-of-flight mass spectrometer using the former laser light as shown in FIG.

This time-of-flight mass spectrometer a is provided with an arrangement part d of a sample c, an ion reflector f, an ion detector g, and reflection mirrors h, i, and j in a vacuum chamber b, while a vacuum chamber b is provided.
A laser light source m that excites the sample c, light sources n and p for observation illumination of the sample c, and an observation microscope q are arranged outside the device.

In this conventional time-of-flight mass spectrometer a, the ion detector g is not coaxially arranged with respect to the ion emission trajectory 1 of the sample c. Therefore, in order to guide the ions emitted from the sample c to the ion detector g, the ion reflector f
Needs to be attached with a certain angle θ, or an ion deflector for deflecting ions must be separately provided.

As described above, when the ion reflector f is attached with an inclination, the ions cannot be efficiently guided to the ion detector unless the attachment angle θ is set with high accuracy. For this reason, fine adjustment is required to set the angle of the ion reflector f, which may be time-consuming to adjust when the device is assembled. This is also the case when an ion reflector for deflecting ions is separately provided, which requires time and effort for adjustment and increases the number of parts, which causes a cost increase. Further, in the structure shown in FIG. 2, the optical system that guides the laser light from the laser light source to the sample and the optical system that guides the light from the observation illumination light source to the sample are independent of each other. The structure of is complicated. That is, when the sample is excited by laser light for analysis, the reflection mirrors i and j for observing the sample interfere with the ion emission trajectory l, so that the reflection mirrors in the analysis mode and the observation mode are different. A mechanism for switching and moving i and j is required, and the structure of the optical system is complicated.

The present invention has been made in view of the above circumstances, and simplifies both the structure of the ion detection system and the optical system to reduce the number of parts and cost, and also adjusts when assembling the device. The purpose is to make it relatively easy.

(C) Means for Solving Problems The present invention adopts the following configuration in order to achieve the above object. That is, the time-of-flight mass spectrometric instrument of the present invention, a laser light source for exciting the sample, a light source for observation illumination of the sample,
A light reflection mirror that guides light from each of the light sources to the sample, a sample stage on which the sample is arranged, an ion reflector that reflects ions emitted from the sample, and an ion detector that detects the ions reflected by the ion reflector. And the light reflection mirror, the sample stage, the ion reflector, and the ion detector are arranged coaxially in a vacuum chamber, the light reflection mirror and the ion detector are integrally fixed, and both are in a central portion. On the other hand, an ion passage hole is formed, and a light introducing means for guiding each light emitted from the laser light source and the illuminating light source to the reflection mirror in common is provided.

(D) Action In the time-of-flight chamber volume analyzer of the present invention, the sample stage, the ion reflector, and the ion detector are all arranged coaxially, so that the ions emitted from the sample are the light reflection mirror and the ion detector. Through the ion passage holes formed in the respective central portions of the above to enter the ion reflector. In this case, the ion reflector is arranged coaxially with the sample stage and each ion passage hole, and the ions entering the ion reflector have a slight incident angle, so that the ions reflected by the ion reflector will travel from the incident orbit. It comes off and goes to the ion detector. Therefore, unlike the conventional case, it is not necessary to attach the ion reflector at an inclination in order to guide it to the ion detector or to provide an ion deflector for deflecting the ions.

Further, each light emitted from the laser light source and the illumination light source is commonly guided by the light introducing means to the optical path leading to the light reflecting mirror. Therefore, the light reflecting mirror serves as both the illumination light source for observing the sample and the laser light source for exciting the sample, and the optical system is simplified.

(E) Example FIG. 1 is a block diagram of a time-of-flight mass spectrometer of the present invention. In the figure, reference numeral 1 indicates the whole of the time-of-flight mass spectrometer, 2 is a sample, 6 is a laser light source for emitting N ₂ laser light or the like for exciting the sample 2, 8 is a light source for observation illumination of the sample 2, Reference numeral 10 is a microscope for observing the sample 2. Further, 12 is a light introducing means for commonly guiding each light emitted from the laser light source 6 and the illumination light source 8 to an optical path leading to a light reflection mirror 24 described later. The light introducing means 12 reflects two lights in the wavelength range of ultraviolet rays, and transmits a part of the light in the wavelength range of visible light except a part thereof.
It is configured by combining.

18 is a vacuum chamber, 19 is a partition forming the vacuum chamber 18, 20 is a partition 19
Is a light-transmitting window, 22 is a condenser lens, and 24 is a light-reflecting mirror that guides light from the laser light source 6 and the observation illumination light source 8 to the sample 2. As shown by the arrow in the figure, the condenser lens 22 is provided so as to be movable along the optical axis in order to adjust the focal position of the sample 2, and the light reflection mirror 24
Is provided with an ion passage hole 24a at the center,
The end face is obliquely cut at 45 ° to form a reflecting surface 24b.

Reference numeral 26 is a sample table on which the sample 2 is arranged, and is provided so as to be movable in two orthogonal axes directions. 28 is an ion extraction electrode arranged on the front surface of the sample.

Reference numeral 30 is an ion reflector that reflects the ions emitted from the sample 2. This ion reflector 30 is configured by arranging a large number of donut-shaped grids 32 in parallel on the same axis, and connecting dividing resistances R _{1 to} Rn for setting an electric field to each grid 32. Further, 34 is an ion detector for detecting the ions reflected by the ion reflector 30, which is integrally fixed to the back side of the light reflecting mirror. In this example, a microchannel plate is used for this ion detector 34, and an ion transmission hole 34a is formed in the center thereof.
Are formed.

The light reflection mirror 24, the sample stage 26, the ion reflector 30 and the ion detector 34 are all arranged on the same axis L in the vacuum chamber 18.

Incidentally, 36 is a dynode for converting the ions passing through the ion reflector 30 into electrons, 38 is a detector for detecting the electrons from the dynode 36, 40 is an amplifier, Vr, V1, Vo are power supplies, and sw
₁ and sw ₂ are switches for switching the analysis mode.

Next, the operation of the time-of-flight mass spectrometer 1 of the present invention will be described.

When the use 2 is excited by laser light to perform mass spectrometry, the laser light source 6 is turned on and the laser light is emitted. The laser light is reflected by the dichroic mirrors 14 and 16, respectively, passes through the condenser lens 22, is reflected by the light reflection mirror 24, and is applied to the sample 2. As a result, the ions excited and emitted from the sample 2 are reflected by the reflecting mirror 24 and the ion passing holes 24 of the ion detector 34, both of which are arranged on the same axis L.
It passes through a and 34a in order and enters the ion reflector 30. In the dynode 32 of the ion reflector 30, each dividing resistor R ₁ ~
A predetermined voltage is applied by Rn, whereby a gradient electric field is formed in the ion reflector 30. That is, when positive ions are emitted from the sample 2, for example, the respective voltages are set so that the stronger the electric field is toward the left side in the figure. Therefore, the ion reflector
The ions introduced into 30 are reflected by the ion reflector 30. In this case, since the ions entering the ion reflector 30 have a slight incident angle, the ions reflected by the ion reflector 30 travel toward the ion detector 34 along a parabolic trajectory. Since the time required to reach the ion detector 30 depends on the mass number of each ion, the ions are mass-separated by the difference in the flight time in the ion reflector 30.

When performing sample observation in parallel with the above sample analysis, or when performing sample observation independently, the observation illumination light source 8 is turned on. The light emitted from the observation illumination light source 8 is transmitted through the first-stage dichroic mirror 14 and then reflected by the second-stage dichroic mirror 16. Then, after passing through the condenser lens 22 and reflected by the light reflection mirror 24, the sample 2 is irradiated with the light. After the reflected light from the sample 2 is reflected by the light reflection mirror 24,
It passes through the dichroic mirror 16 via the condenser lens 22 and is guided into the observation microscope 10. In this way, the light reflecting mirror 24 serves as both the illumination light source 8 for observing the sample and the laser light source 6 for exciting the sample.

In the time-of-flight mass spectrometer 1 of this embodiment, by switching the switches sw ₁ and sw ₂ , the ions are passed through the ion reflector 30 and guided to the dynode 36, where they are converted into electrons and then detected. It is also possible to detect at 38. In addition to this embodiment, an ion reflector
Even in a time-of-flight mass spectrometer not provided with 30, the ion detector 34 can be arranged coaxially with the sample stage 26 and the light reflection mirror 24 to obtain the same effect as described above. Further, the back surface of the sample 2 is irradiated with laser light to
The present invention can also be applied to a system of detecting ions emitted from the other surface of the.

(F) Effect As described above, according to the present invention, the light reflecting mirror, the sample stage,
Since both the ion reflector and the ion detector are coaxially arranged in the vacuum chamber, it is not necessary to mount the ion reflector at an angle to guide it to the ion detector or to provide an ion deflector for deflecting ions as in the conventional case. . Further, the light reflection mirror serves as both the illumination light source for observing the sample and the laser light source for exciting the sample. As a result, both the structure of the ion detection system and the optical system can be simplified, so the number of parts can be reduced, cost can be reduced, and adjustments can be made easily when assembling the device. It

Further, in the present invention, since the light reflection mirror and the ion detector are integrally fixed, the assembly work can be easily performed by incorporating the integrated one. In particular, when assembling, it is necessary to match the optical axes of the light reflecting mirror and the ion detector, but since this invention does not require such an effort, the labor of assembling can be greatly saved. Further, since the light reflection mirror and the ion detector are integrally fixed, the respective optical axes are stably aligned with each other, which enables stable detection by the ion detector and high analysis accuracy is obtained. .

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention, FIG. 2 shows a conventional example, and FIGS. 1 and 2 are configuration diagrams of a time-of-flight mass spectrometer. 1 ... Time-of-flight mass spectrometer, 2 ... Sample, 6 ... Laser light source, 8 ... Observation illumination light source, 12 ... Light introducing means, 18
...... Vacuum chamber, 24 ...... Light-reflecting mirror, 24a …… Ion passage hole, 26 …… Sample stand, 30 …… Ion reflector, 34 …… Ion detector, 34a …… Ion passage hole.

Claims (1)

[Claims] 1. A laser light source for exciting a sample, a light source for observing and illuminating the sample, a light reflection mirror for guiding the light from each of the light sources to the sample, a sample stage on which the sample is arranged, and a light source emitted from the sample. An ion reflector for reflecting ions, and an ion detector for detecting ions reflected by the ion reflector.The light reflection mirror, the sample stage, the ion reflector, and the ion detector are coaxially arranged in a vacuum chamber. In addition, the light reflection mirror and the ion detector are integrally fixed, and an ion passage hole is formed in the center of both, and each light emitted from the laser light source and the illumination light source is reflected by the reflection mirror. A time-of-flight mass spectrometer characterized by being provided with a light introducing means for commonly guiding the light path to.