JPH11297267A - Time-of-fiight mass spectrometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve resolution without impairing detecting sensitivity of an ion by flying the ion on a revolving path. SOLUTION: A pluse-like ion from an ion source 24 is accelerated by constant voltage to proceed to a ring-shaped revolving path 10 by a deflection electrode 28 so as to get on the revolving path 10 by an incident electrode 30 or 50 operating in synchronism with the incidence. For example, the ion revolving in the revolving path 10 by six sets of toroidal type sector electric fiels 12, 14, 16, 18, 20, 22 is completely corrected in a flying time difference at half round time by the converging action of the sector electric fields, and is returned to a central path to eliminate the flying time difference at one round time, and returns again to the same point to continue to revolve without diverging by taking the same path in a revolution on and after second time. After revolving by the target number of times, the ion is taken out of the revolving path by operation of an emitting electrode 32 or 52 to measure time up to a detector from pulse operation of the ion source 24 by a TOF measuring circuit 40. Since the sector electric fields are used in this way, there is the triple converging action on a time space to prevent scattering of ion beams.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a time-of-flight (TOF) which determines the mass of an ion by measuring the time of flight of the ion over a predetermined distance (abbreviated as TOF).
The present invention relates to a mass spectrometer, and more particularly to a TOF mass spectrometer capable of improving resolution without deteriorating ion detection sensitivity.

[0002]

2. Description of the Related Art There is known a TOF mass spectrometer that measures the TOF and determines the mass of an ion by utilizing the fact that the flight speed of the ion differs for each ion.

A conventional TOF mass spectrometer simply flies ions linearly from an ion source to a detector, and the resolution is determined by the linear distance from the ion source to the detector.

[0004] Therefore, in order to improve the resolution of the TOF mass spectrometer, it is necessary to increase the flight distance of the ions, which inevitably increases the size of the device.

[0005]

However, in practice, there is a practical limit to the size of the device. In addition, if a long flight distance is taken, the detector is inevitably distant, and the solid angle at which the detector can be seen from the ion source is reduced, so that the counting rate is lost due to the divergence of the ion beam. As a result, the amount of ions reaching the detector is reduced and the sensitivity of the device is also reduced.

Therefore, the conventional TOF mass spectrometer had to compromise both the sensitivity and the resolution of the apparatus.
Further, when the flight distance is extended to further improve the resolution, it is necessary to increase the distance from the ion source to the detector, and mechanical modification of the apparatus is required.

The present invention has been made to solve the above-mentioned conventional problems, and has as its object to improve the resolution without deteriorating the ion detection sensitivity.

[0008]

According to the present invention, there is provided a TOF mass spectrometer for determining the mass of an ion by measuring the time that the ion flies over a predetermined distance, wherein the ion flies in a circular orbit. It is a solution to the problem.

Further, the orbit is a race track type ring-shaped orbit.

Further, the ions fly in a circular orbit by using a sector electric field.

Further, the number of turns of the ions is electrically controlled by the timing of a pulse voltage applied to the incident electrode and the output electrode.

In the TOF mass spectrometer, as shown in FIG. 1, for example, six toroidal sector electric fields 12, 14, 1 for forming a circular orbit 10 of ions.
6, 18, 20, 22 and emitted from the ion source 24,
A deflecting electrode 28 for changing the traveling direction of ions traveling on the incident trajectory 26 and placing the ions on the orbit 10 and ions whose traveling direction is bent by the deflecting electrode 28 are introduced into the orbit 10 at a predetermined timing. Electrodes 30 for extracting ions from the orbit 10 at a predetermined timing and guiding the ions toward the detector 34 so that the ions orbit the orbit 10 a predetermined number of times. It was made.

In FIG. 1, six toroidal sector electric fields are arranged in an oval shape. However, the number, arrangement and form of the sector electric fields are not limited to the example of FIG. It is also possible to arrange them so as to be substantially rectangular. Further, the toroidal sector electric field may be replaced with a combination of a cylindrical sector electric field and an electrostatic quadrupole (Q) lens.

[0014] In this way, for example, a racetrack-type ring-shaped ion trajectory is designed by using a toroidal sector electric field excellent in convergence action.
Ions can orbit many times on the same orbit. Since the flight distance of the ions is twice as long as the length of one orbit, the flight distance can be increased without increasing the size of the apparatus.

Further, even when the flight distance is extended to further improve the resolution, there is no need to mechanically modify the apparatus, and it is possible to cope only by increasing the number of rounds of ions. The number of turns of the ions can be electrically controlled, for example, by controlling the timing of a pulse voltage applied to the incident electrode 30 and the output electrode 32.

In order to realize an improvement in resolution in a large number of rounds of ions, it is desirable to satisfy the following triple convergence with respect to time.

1. At the position of incidence on the ring, ions that are incident with a horizontal inclination with respect to the central trajectory have the same flight time as ions passing through the central trajectory at the time when they make a half circle around the ring.

2. At the position of incidence on the ring, ions incident at a position shifted in the horizontal direction with respect to the central trajectory have the same flight time as ions passing through the central trajectory at a time when the ring makes a half circle.

3. Ions having kinetic energy different from the set kinetic energy have the same flight time as ions passing through the central trajectory at the time when they make a half circle around the ring.

In order to prevent the loss of the counting rate due to the divergence of the ion beam in many rounds of ions, it is desirable to satisfy the following triple convergence with respect to space.

1. At the position of incidence on the ring, the ions that have entered the central orbit with an inclination in the horizontal direction return to the central orbit at the time when they have made a half circle around the ring.

2. At the incident position of the ring, ions that have entered with a tilt in the vertical direction with respect to the central trajectory return to the central trajectory at the time when they have made a half circle around the ring.

3. Ions having a kinetic energy different from the set kinetic energy return to the central orbit when the ion makes a half circle around the ring.

The convergence condition is designed by ion trajectory calculation.

[0025]

Embodiments of the present invention will be described below in detail with reference to the drawings.

This embodiment is a TOF mass spectrometer having a toroidal sector electric field 12 to 22, an ion source 24, a deflection electrode 28, an incident electrode 30, an output electrode 32 and a detector 34 as shown in FIG. 2, the incident trajectory 26, the incident electrode 30, the exit electrode 32, and the incident trajectory 46 disposed on the side opposite to the detector 34, the incident electrode 50, the exit electrode 52, and the detector 54, as shown in FIG. And conversion dynodes 36 and 56 that convert ions extracted by the emission electrodes 32 and 52 into electrons and guide the electrons toward the detectors 34 and 54.
And with.

The ion source 24 comprises a primary ion gun 24
A, an ion gun power supply 24B for applying a required voltage to the primary ion gun 24A, a sample target 24C, an ion acceleration electrode 24D for accelerating sample ions generated by primary ion bombardment on the sample target 24C, and an acceleration for the ion acceleration electrode 24D. A so-called secondary ion source constituted by an ion accelerating power supply 24E for applying a voltage, an ion chopper 24F, and an ion chopper power supply 24G for applying a predetermined pulsed voltage to the ion chopper 24F. ing.

The deflection electrode 28 has a deflection electrode power supply 29.
Is connected.

For applying a predetermined pulse voltage to one of the incident electrodes 30 and 50,
The common incident electrode power supply 31 is connected.

The toroidal sector electric fields 12, 14, 1
6, 18, 20, and 22 respectively have toroidal power supplies 13, 15, 17, 19, 2 for applying a predetermined voltage.
1, 23 are connected.

For applying a predetermined pulse voltage to one of the emission electrodes 32 and 52,
The common output electrode power supply 33 is connected.

The detectors 34 and 54 are, for example, electron multipliers, and are connected to a common MCP power supply 38 and a TOF measuring circuit 40.

The conversion dynodes 36 and 56 are connected to a common dynode power supply 42.

Hereinafter, the operation of the present embodiment will be described.

The ions produced in a pulse form by the ion source 24 are accelerated at a constant voltage and travel toward the deflection electrode 28. The ions guided to the race-track ring-shaped orbit 10 by the deflection electrode 28 are placed on the orbit 10 by the incident electrode 30 or 50 which operates in synchronization with the incidence. For example, the ions orbiting the ring-shaped orbit 10 by the six sets of toroidal sector electric fields 12, 14, 16, 18, 20, 22 have a flight time lag at the time of a half circle due to the convergence of the toroidal sector electric field. Is completely corrected and returned to the central trajectory.
Even at the time of the round, there is no delay in the flight time, and the vehicle returns to the same point again. Since the ions take the same orbit in the second and subsequent rounds, they do not diverge, and the six sets of toroidal sector electric fields 12, 14, 16, 18, 20,
It is possible to continue the orbit after passing through 22. The ions that have circulated the desired number of times are taken out of the orbit 10 by operating the emission electrode 32 or 52 and are detected by the detector 34 or 5.
4 and converted into an electric signal.

At this time, the time from the pulse operation in the ion source 24 to the arrival at the detector 34 or 54 is represented by T
The measurement is performed by the OF measurement circuit 40. When the acceleration voltage of the ion source 24 is measured as V, the flight distance of the ions is measured as L, and the flight time is measured as T, the mass m per ion charge can be obtained by the following equation.

M = (2VT ² ) / L ² (1)

In the present embodiment, since a toroidal sector electric field is used, there is a triple convergence effect with respect to time, and the resolution is improved. In addition, since the toroidal sector electric field has a triple convergence function with respect to space, divergence of the ion beam is prevented, and the detection sensitivity is not impaired.
The means for orbiting the ions is not limited to the toroidal sector electric field. For example, the same operation and effect can be obtained by replacing the electric field with a cylindrical sector electric field and an electrostatic quadrupole (Q) lens.

In this embodiment, since the ion source, the deflection electrode, the incident electrode, the emission electrode, and the detector are arranged on both sides of the orbit 10, a common orbit can be used efficiently. Note that, as in the example shown in FIG. 1, these can be provided only on one side, or the incident equipment can be arranged on one side and the emission equipment can be arranged on the other side.

In the above embodiment, the present invention provides:
Although the present invention has been applied to a general TOF mass spectrometer, the application of the present invention is not limited to this, and a charged particle analyzer in atomic physics or nuclear physics or a beam using an ion implanter is used. Obviously, it is equally applicable to engineering equipment.

[0041]

According to the present invention, since ions orbit around the same orbit, a long flight distance can be obtained without increasing the size of the apparatus, and the resolution is improved. Further, even when the flight distance is extended, it is only necessary to increase the number of laps, and there is no need to mechanically modify the device.

[Brief description of the drawings]

FIG. 1 is a plan view showing a configuration example of the present invention.

FIG. 2 is a plan view showing the configuration of the embodiment of the present invention.

[Explanation of symbols]

Reference Signs List 10 orbiting orbits 12, 14, 16, 18, 20, 22 ... toroidal sector electric field 24 ... ion source 26, 46 ... incident orbit 28 ... deflection electrode 30, 50 ... incident electrode 32, 52 ... exit electrode 34, 54 ... Detector 36, 56 Conversion dynode 40 TOF measurement circuit

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Kenji Okanishi 5-2 Sokaicho, Niihama-shi, Ehime Sumitomo Heavy Industries, Ltd. Niihama Works (72) Inventor Hiromitsu Nakabushi 5-9-1 Kita Shinagawa, Shinagawa-ku, Tokyo No. 11 Sumitomo Heavy Industries, Ltd.

Claims (6)

[Claims] 1. A time-of-flight mass spectrometer for determining the mass of an ion by measuring the time it takes for the ion to fly over a predetermined distance, wherein the ion flies in a circular orbit. Time-of-flight mass spectrometer. 2. The time-of-flight mass spectrometer according to claim 1, wherein the orbit is a racetrack-type ring-shaped orbit. 3. A time-of-flight mass spectrometer according to claim 1, wherein said ions fly in a circular orbit by using a sector electric field. Analysis equipment. 4. The time-of-flight mass spectrometer according to claim 1, wherein the number of turns of the ions is electrically determined by the timing of a pulse voltage applied to the incident electrode and the output electrode. A time-of-flight mass spectrometer characterized by being controlled. 5. A time-of-flight mass spectrometer for determining the mass of an ion by measuring the time it takes for the ion to fly over a predetermined distance, comprising: a fan-shaped electric field for forming a circular orbit of the ion; A time-of-flight mass spectrometer comprising: an incident electrode for introduction; and an emission electrode for extracting ions from the orbit, wherein the ions fly in a orbit. 6. The time-of-flight mass spectrometer according to claim 3, wherein said sector electric field is a toroidal sector electric field.