JPS5838909B2 - ion source - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ion source suitable for use in a mass spectrometer,
In particular, it relates to an ion source that ionizes a sample by colliding high-speed neutral particles with it.

As ionization methods for ion sources used in mass spectrometers, electron impact type, chemical ionization type, field ionization type, field desorption type, and the like have been developed and put into practical use one after another.

By the way, recently, an ionization method that collides high-energy high-speed neutral particles (such as Ar atoms) with a sample and ionizes the sample with that energy has been attracting attention.
This method has (1) low ionization energy;
This is a strong ionization.

(2) High generation rate of not only positive ions but also negative ions,
(3) There is little thermal decomposition of the sample because no heating vaporization is required.
4) Since it is a neutral particle, it does not cause charge-up and can be easily ionized even in insulators, so it is expected to be developed in the future as a method with many advantages.

However, in this type of ion source, the sample is irradiated with neutral particles that do not have an electric charge, so it cannot be detected electrically by placing an electrode, and the amount of irradiation of the neutral particles onto the sample cannot be monitored. This was extremely difficult.

The present invention was made in view of this point, and it collides with a high-speed ion beam produced by an ion gun and converts it into a neutral particle beam, and removes the remaining unconverted particles from the neutral particle beam. Focusing on the structure of an ion source in which ions are removed using a deflection means, an electrode is placed at a position where the ions deflected by the deflection means collide, and the amount of ions removed by the electrode is detected, and based on the It is characterized by calculating the amount of neutral particles using

The present invention will be explained in detail below using the drawings.

The drawing is a sectional view showing an embodiment of the present invention, and numeral 1 in the drawing is an ion gun for temporarily ionizing neutral particles, such as Ar atoms, which are irradiated onto a sample.

The ion gun 1 is attached to a side wall 2 of an ion source of a mass spectrometer and its interior is evacuated via an exhaust pipe 3 and a valve 4 by a vacuum pump (not shown).

The ion gun 11ri has a cylindrical electrode 5 and an anode 7 arranged in an ion generation chamber 6 formed inside the cylindrical electrode 5.
and a filament 8, and a three-stage annular lens electrode 9, 10, 11 attached to the lower end of the cylindrical electrode 5.

The electrodes 9 and 11 are connected to a ground potential, and the electrode 10 is connected to a power source 12.
A positive potential of several KV is applied to the generation chamber 6.
The positively charged Ar ions (Ar+) generated are accelerated and focused by the electric field formed between these electrodes, and are taken out of the ion gun as a high-speed Ar ion beam 13.

Here, the annular electrode 11 is divided into three parts, as shown in FIG. 2, which is a sectional view taken along the line ■-■' in FIG. 1, and integrally formed with an insulating spacer 14 in between.
It has a structure in which the Ar ion beam 13 can be deflected in the X direction by applying a positive or negative variable potential of several hundred square meters to the electrode, and can be deflected in the Y direction by applying a similar variable potential to the split electrode 11. ing.

15 is a power source for heating the filament; 16 is a power source for applying a voltage of several hundred V between the filament and the anode;
17 is a power source for applying a negative potential to the electrode 5 with respect to the anode in order to reverse the electrons generated from the filament toward the electrode 5 toward the anode, and 38 is a power source for applying an accelerating voltage. .

The high-speed Ar ion beam 13 taken out from the ion gun 1 in this manner passes through a collision box 19 fixed to the ion source side wall 2 via an insulator 18 and is introduced into the ion source. A negative high voltage is applied to the collision box 19 from a power source 20, and the Ar ion beam 13 is accelerated to a higher speed by the high voltage and enters the collision box 19.

Ar gas (
A large portion of the ions passing through the collision box collide with the Ar atoms, and their direction and speed remain almost unchanged, only their charge is removed, resulting in high speed. Since the ions are converted into neutral Ar atoms, Ar ions and neutral Ar atoms coexist in the beam that has passed through the collision box 19.

Of these, the Ar ions are deflected by a subsequent deflector 22 and removed, and only neutral Ar atoms pass through the deflector 22 and are extracted as a high-speed Ar atomic beam 23.

In the present invention, at this time, of the pair of electrodes of the deflector 22, the electrode with which the deflected Ar ions collide is grounded via the ammeter 24.

High-speed Ar atomic beam 23 taken out from the deflector 22
is introduced into the ionization box 26 through the notch 25,
Target 2 inserted into the ionization box 26 from the rear
The atomic beam 23 of No. 7 collides with an inclined target surface, and ionizes a sample prepared by mixing glycerin and a test substance coated on the collision surface.

The target 27 is made of copper, for example, and is attached to the tip of the introduction probe 29 via an insulator 28, and an accelerating voltage of, for example, about 3 KV is applied from a power source 30.The sample ions ejected from the surface are separated by the accelerating voltage. Pressure vessel 31
Appropriate voltages obtained by dividing the voltages are drawn out and accelerated by the slit electrode groups 32 to 35 to which they are applied, respectively, and guided to a mass spectrometer (not shown).

Note that 36 is a power source for applying a bias bias (variable positive and negative) between the target 27 and the ionization box 26.

In such a configuration, the ArCrE force required for the ion gun 1 (10''-10'Torr) is the same as the collision box (same (
10"-10-3 Torr), and the respective pressures are set to be maintained by adjusting the size of the beam passage port a connecting the two and the adjustment of the pulp 4.

In addition, the beam passage port on the exit side of the collision box 19 also has a high vacuum (10
The hole is smaller than a so that a pressure difference between the inside of the ion source and the inside of the ion source (below Torr) can be maintained.

The Ar ions generated in the generation chamber 6 in the ion gun 1 are accelerated by the annular lens electrodes 9° io and ii, then pass through the collision box 19 and are converted into a neutral Ar atomic beam.
Further, the ions in the beam are removed by the deflector 22, but in the present invention, the electrode of the pair of electrodes of the deflector 22 with which the deflected Ar ions collide is grounded via the ammeter 24. The ion current flowing into the electrode is monitored.

The ratio between the amount of Ar ions and the amount of neutral Ar atoms contained in the beam that has passed through the collision box 19 is constant, so the current meter 2
It is thought that there is a proportional relationship between the ionic current detected in step 4 and the amount of neutral Ar atoms.
It becomes possible to convert and monitor the amount of atoms.

Therefore, the operating state of the ion gun can be controlled in accordance with the monitoring results, and the amount of irradiated neutral Ar atoms (C per time) can be set to a desired value.

In the above-mentioned embodiment, the ions collided with one of the pair of electrodes of the deflector 22, and the ion current flowing into that electrode was detected, making the configuration simple. As shown, a detection electrode 37 may be installed separately from the deflector 22, and the deflected ions may collide with the detection electrode 37.

It is also possible to use not only the electrostatic type as in the above example but also an electromagnetic type as the deflection means, and as shown in Figure 3, by applying a magnetic field H in a direction perpendicular to the plane of the paper, ions are drawn to the detection electrode 37. can be detected by colliding with each other.

Furthermore, although Ar atoms were used in the above-described embodiments, other atoms or neutral particles may also be used for collision.

Furthermore, in the above embodiment, a collision box was provided as a means of converting Ar ions into neutral Ar atoms, and the interior was filled with Ar gas, but it is possible to create a region after the ion gun in which a suitable amount of Ar gas exists. If possible, the transformation can be performed in that region without providing an independent collision box.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of one embodiment of the present invention, FIG. 2 is a sectional view taken along the line II', and FIG. 3 is a diagram showing essential parts of another embodiment. 1: ion gun, 13: Ar ion beam, 19: collision box, 22: deflector, 23: high-speed Ar atomic beam, 24: ammeter, 26: ionization box, 27: target, 37: detection electrode.

Claims (1)

[Claims] 1. An ion gun, a conversion means for colliding an ion beam extracted from the ion gun with a collision gas to convert it into a neutral particle beam, and ions that are not converted from the neutral particle beam. In an ion source that includes a deflection means disposed after the conversion means to remove
An ion source comprising a detection electrode for detecting ions deflected by the deflection means. 2. The ion source according to claim 1, wherein the deflection means is an electromagnetic deflector. 3. The ion source according to claim 1, wherein the deflection means is a pair of electrostatic deflection electrodes disposed opposite to each other with the neutral particle beam interposed therebetween. 4. The ion source according to claim 3, wherein one of the pair of electrostatic deflection electrodes also serves as a detection electrode.