JPS5838910B2 - 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 (1) is a soft ionization method with low ionization energy, (2) has a high production 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 cannot be deflected, so alignment of the irradiation of the neutral particles onto the sample must be done by mechanically moving the sample. Not only was a complicated precision fine movement mechanism required, but alignment was also time-consuming and labor-intensive.

The present invention has been made in view of this point, and focuses on the structure of an ion source in which a high-speed ion beam produced by an ion gun is converted into a neutral particle beam in a collision box. It is characterized in that the traveling direction of the neutral particle beam is changed by arranging an ion deflecting means and deflecting the ion beam.

The present invention will be explained in detail below using the drawings. The drawing is a cross-sectional view showing the configuration of 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 to be irradiated onto a sample.

The ion gun 1 is attached to the ion source side wall 2 of the 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 1 includes a cylindrical electrode 5, an anode 7 and a filament 8 disposed in an ion generation chamber 6 formed inside the cylindrical electrode 5, and three stages attached to the lower end of the cylindrical electrode 5. It is composed of annular lens electrodes 9, 10, and 11.

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 in the ion gun 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 sections as shown in FIG. Or by applying a variable potential up to several hundred V negative
The ion beam 13 can be deflected in the X direction, and the divided electrode 11
The structure is such that it can be deflected in the Y direction by applying a similar variable potential to .

15 is a power source for heating the filament; 16 is a power source for applying a voltage of several hundred μ 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 37 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 21, 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 chamber collide with the Ar atoms, and their direction and speed remain almost unchanged, only their charge is taken away, resulting in a high-speed medium. Since the ions are converted into neutral Ar atoms, the beam passing through the collision box 19 contains a mixture of Ar ions and neutral Ar atoms.

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 this embodiment, at this time, of the pair of electrodes of the deflector 22, the electrode with which the deflected Ar ions collide is connected to the ammeter 24.
The Ar ion current is monitored by grounding through the ground.

Furthermore, since there is a proportional relationship between the Ar ion current and the amount of neutral Ar atoms, the amount of neutral Ar atoms can also be indirectly monitored.

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 targera) 27 is made of copper, for example, and is attached to the tip of the introducing glove 29 via an insulator 28, and an accelerating voltage of, for example, about 3 KV is applied from a power source 30, and the sample ions ejected from its 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 voltage (variable positive and negative) between the target 27 and the ionization box 26.

In such a configuration, the Ar necessary for the ion gun 1 (pressure: 10-3 to 10-' Torr) is supplied from the collision box (also < 10-2 to 10-3 Torr), and the beam passing between the two The respective pressures are set to be maintained by adjusting the size of the opening a and the valve 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 (-5 Torr or less) can be maintained.

The Ar ions generated in the generation chamber 6 in the ion gun 1 are accelerated by the annular lens electrode 9, 10° 11, then pass through the collision box 19 and are converted into a neutral Ar atomic beam. In this embodiment, the lens electrode 11 also serves as an X-Y deflector as shown in FIG. The traveling direction of the converted neutral Ar atomic beam 23 also changes arbitrarily.

Therefore, the irradiation position of the Ar atomic beam 23 onto the sample can be electrically controlled, and accurate positioning can be achieved in a shorter time than in the conventional method in which the sample is moved mechanically.

It should be noted that the beam passage opening of the collision box 19 is mainly aligned in the direction of arrow C in FIG. It is desirable to make the hole long in the C direction in consideration of maintaining this.

In the above-described embodiment, the lens electrode 11 of the ion gun 1 is divided and used as a deflector by applying a deflection voltage, but the present invention is not limited to this, and an independent deflector may be provided between the ion gun and the collision box. Needless to say, it is good to use an electromagnetic type deflector.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of one embodiment of the present invention.
The figure is an I-I' cross-sectional view. 1: Ion gun, 9, 10.11: Annular lens electrode, 11
', 1111: split electrode, 132 Ar ion beam,
19: Collision box, 22: Deflector, 23: High speed Ar atomic beam, 27 Ni target.

Claims (1)

[Claims] 1. An ion generation chamber, a means for accelerating the ions generated in the generation chamber, and a passage through which the accelerated ions are passed, and a collision gas contained therein deprives the ions of electric charge. An ion source that includes a collision box for converting neutral particles into neutral particles and ionizes the sample by irradiating the neutral particles onto the sample,
An ion source characterized in that a deflection means for deflecting ions is provided between the collision box and the ion generation chamber. 2. The ion source according to claim 1, wherein the electrode that accelerates the ions also serves as the deflection means.