JPS6135658B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ion source suitable for use in a mass spectrometer, and particularly to an ion source in which a sample is ionized by colliding with high-speed neutral particles.

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-velocity neutral particles (such as Ar atoms) with a sample and ionizes the sample with that energy has been attracting attention, and this method is (1)
It is a soft ionization method with low ionization energy, (2) it has a 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) it produces neutral particles. Therefore, it is expected to be developed in the future as a method that has many advantages such as no charge up and can easily ionize even insulating materials.

By the way, in this type of ion source, when creating fast neutral particles such as fast Ar atoms,
An Ar ion gun creates an Ar ion beam, accelerates it to high speed, and then passes it through a collision box filled with collision gas (Ar gas), which strips the ions of their charge and converts them into high-speed neutral Ar atoms. Therefore, it is necessary to supply Ar gas at appropriate pressures to the ion gun and the collision chamber, respectively. The present invention has been made in view of this point, and is constructed by supplying Ar gas only to the collision box, and leaking Ar gas from the collision box to supply the ionization gas to the ion gun. The purpose is to provide an ion source that can simplify the process. The present invention will be explained in detail below using the drawings.

The drawing is a sectional view showing the configuration of one embodiment of the present invention, and in the drawing 1 is a neutral particle, for example, which irradiates the sample.
This is an ion gun for temporarily ionizing Ar atoms. The ion gun 1 is attached to an ion source side wall 2 of a mass spectrometer, and its interior is evacuated via an exhaust pipe 3 and a pulp 4 by a vacuum pump (not shown). The ion gun 1 includes a cylindrical electrode 5,
Ion generation chamber 6 formed inside the cylindrical electrode 5
an anode 7 and a filament 8 arranged in
It is composed of three-stage annular lens electrodes 9, 10, and 11 attached to the lower end of the cylindrical electrode 5. The electrodes 9 and 11 are given a ground potential, and the electrode 10 is given a positive potential of several KV by a power source 12, and the Ar having a positive charge generated in the generation chamber 6 is
Ions (Ar ⁺ ) are accelerated and focused by the electric field formed between these electrodes, and are accelerated at high speed.
The Ar ion beam 13 is taken out of the ion gun.

Here, the annular electrode 11 is shown in FIG.
As shown in FIG. 2, which is a cross-sectional view, it is divided into three parts and integrally molded with an insulating spacer 14 in between, and a variable potential of up to several hundred V, positive or negative, can be applied to the divided electrode 11'. Ar ion beam 1
3 can be deflected in the X direction, and can also be deflected in the Y direction by applying a similar variable potential to the divided electrodes 11''.

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, and 17 is for reversing the electrons generated from the filament toward the electrode 5 toward the anode. 38 is a power source for applying a negative potential to the electrode 5 with respect to the anode, and 38 is a power source for applying an accelerating voltage.

The high speed sample taken out from the ion gun 1 in this way
The Ar ion beam 13 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. is applied, and Ar
The ion beam 13 is accelerated to a higher speed by the high voltage and enters the collision box 19. Ar gas (neutral Ar atoms) is supplied to the interior of the collision box 19 via an introduction pipe 21 and a valve 22.
A considerable portion of the ions passing through the collision chamber collide with the Ar atoms, and their motion direction and speed hardly change, only their charge is removed and they are converted into high-speed neutral Ar atoms, so the collisions occur. Ar ions and neutral Ar atoms coexist in the beam that has passed through box 19. Of these, the Ar ions are deflected by the subsequent deflector 23 and removed, making them neutral.
Only Ar atoms pass through the deflector 23 and are extracted as a high-speed Ar atom beam 24. In this embodiment, the Ar ion current is monitored by grounding the electrode of the pair of electrodes of the deflector 23 with which the deflected Ar ions collide through the ammeter 25. Also, Ar ion current and neutrality
Since there is a proportional relationship with the amount of Ar atoms, the amount of neutral Ar atoms can also be monitored indirectly.

The high-speed Ar atomic beam 24 taken out from the deflector 23 passes through the notch 26 to the ionization box 27.
The Ar atomic beam 24 of the target 28 inserted into the ionization box 27 from the rear collides with the tilted target surface;
A sample prepared by mixing glycerin and a test substance applied to the collision surface is ionized. The target 28 is made of copper, for example, and is attached to the tip of the introduction probe 30 via an insulator 29, and an accelerating voltage of, for example, about 3 KV is applied from a power source 31. It is drawn out and accelerated by slit electrode groups 33 to 36 to which appropriate voltages are applied after being divided at 32, and guided to a mass spectrometer (not shown). 37 is the target 27 and the ionization box 2
This is a power supply for applying a bias voltage (variable positive and negative) between the 7 and 7.

In such a configuration, the collision box 19 is suitable for efficiently converting the ion beam into neutral Ar atoms.
The Ar pressure P ₁ is approximately 10 ^-2 to ^{10 -3} Torr, and Ar gas necessary to maintain this pressure within the collision box is sent into the collision box via the valve 22 and the introduction pipe 21. Precise adjustment of P ₁ can be achieved by operating valve 22. On the other hand, the pressure _P2 of the ionizing Ar gas required to continuously and stably generate an ion beam in the ion gun 1 is approximately 10 ^-3 to 10 ^-4 Torr, and the pressure P2 required to maintain this pressure is approximately 10 -3 to 10 -4 Torr. Ar gas is supplied from the collision box 19 through the beam passage port a of the collision box 19. The conductance of the beam passage port a is set to an extent that allows the pressure difference between P ₁ and P ₂ , and the accuracy of P ₂ can be adjusted by changing the opening degree of valve 4 and adjusting P ₁ by operating valve 22 . It can be done independently of adjustment.

Also, the beam passage port b on the exit side of the collision box 19 is made smaller than a to keep the conductance small so as to maintain a pressure difference with the inside of the high vacuum (10 ^-5 Torr or less) ion source.

In this way, Ar gas for ionization is supplied from the collision box 19, and its pressure is set to the optimum value _P2 by the valve 4.The Ar ion beam 13, which is accelerated to a high speed, is continuously stabilized from the ion gun. Furthermore, the ion beam 13 is efficiently converted into an Ar atomic beam in the collision chamber 19, which is set at an optimum pressure _P1 by the valve 22.

In the embodiment described above, ionizing Ar gas is supplied to the ion gun 1 from the collision box 19 through the beam passage a.
However, the present invention is not limited to this, and a separate passageway for leakage may be provided.

As described in detail above, according to the present invention, an ion source is realized which has a simple configuration in which the collision gas is supplied only to the collision chamber, and in which the pressures of the collision chamber and the ion gun can be adjusted independently.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of an embodiment of the present invention, and FIG. 2 is a cross-sectional view along the line -'. 1: Ion gun, 3: Exhaust pipe, 4, 22: Valve, 13: Ar ion beam, 19: Collision box, 2
1: Introduction tube, 24: High speed Ar atom beam, 28:
Target.

Claims (1)

[Claims] 1. An ion gun, and a collision box having a passage through which ions taken out from the ion gun pass, and for colliding the ions with a collision gas contained therein to convert the ions into neutral particles. In an ion source that ionizes a sample by irradiating the sample with the neutral particles, a means for supplying a collision gas to the collision box is provided, and the collision gas is leaked from the collision box to the ion gun to ionize the ion gun. An ion source characterized in that it is configured to be used as a commercial gas. 2. The ion source according to claim 1, wherein the collision gas is leaked to the ion gun through an ion passage opened in the collision box.