JPH06131999A - Emittance measuring device for ion beam - Google Patents

Abstract

PURPOSE:To measure the emittance of an ion beam from the ion current distribution measured by a Faraday cup by independently changing the orbit radius of the ion beam with a deflecting electromagnet and the deflection angle with a deflecting unit. CONSTITUTION:A slit 12 having the longitudinal direction perpendicular to the deflection plane is arranged in front of a deflecting electromagnet 11 which is a mass separator of an ion beam. The beam emitted from the electromagnet 11 is limited to that passable through the slit 12, and it is fed to a Faraday cup 14 via a deflecting unit 13. When the coil current of the electromagnet 11 or the energy of the beam is changed, the orbit radius of the beam is finely changed. The angular distribution of the beam is determined by the ion current measured by the Faraday cup 14 when the deflection angle is changed by the deflecting unit 13. The orbit radius of the beam is changed by the electromagnet 11, the deflection angle is changed by the deflecting unit 13 independently respectively, and the emittance of the ion beam can be measured from the ion current distribution of the Faraday cup 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion beam emittance measuring device capable of accurately measuring the ion beam emittance.

[0002]

2. Description of the Related Art An example of a conventional ion beam emittance measuring device is shown in FIG. 5, in which a second slit 1 which also moves independently with a space in front of a first slit 1 which moves independently. 2 is arranged, and further, a Faraday cup 3 is arranged in front of the second slit 2 with a slight interval.

Another example is shown in FIG. 6, in which a first slit 5 is attached to the entrance of a box-shaped measuring section 4 which is entirely mechanically moved. Inside the measurement unit, an electrostatic deflector 6 including a pair of parallel electrodes 6a and 6b, a second slit 7, and a Faraday cup 8 are arranged in this order.

In an example of a conventional ion beam emittance measuring apparatus, the first slit 1 and the second slit 2 are moved perpendicularly to the optical axis of the ion beam, and the first slit 1 and the second slit 2 are moved. The current of the ion beam that has passed is measured by the Faraday cup 3 to measure the emittance of the ion beam.

In another example, the entire box-shaped measuring unit 4 is moved vertically to the optical axis of the ion beam, and the voltage applied to the pair of parallel electrodes 6a and 6b of the electrostatic deflector 6 is changed. Deflect the ion beam. Therefore, the ion beam that has passed through the first slit 5 is deflected by the pair of parallel electrodes 6a and 6b of the electrostatic deflector 6, then passes through the second slit 7, and its current is measured by the Faraday cup 3, Measure the emittance of the ion beam.

[0006]

In an example of a conventional ion beam emittance measuring device, the first slit 1 and the second slit 2 are moved perpendicularly to the optical axis of the ion beam as described above. However, the positions of the first slit 1 and the second slit 2 with respect to the optical axis of the ion beam must be controlled with sufficiently fine accuracy as compared with the spatial spread of the ion beam in the vacuum system. There was a problem that the structure of the device became complicated.

Also, in another example, since the entire box-shaped measuring unit 4 is moved perpendicularly to the optical axis of the ion beam as described above, the box-shaped measurement is performed as in the case of the above-mentioned one example. The position of the entire part 4 with respect to the optical axis of the ion beam must be controlled with sufficiently fine accuracy as compared with the spatial spread of the ion beam in the vacuum system, which causes a problem that the structure of the vacuum device becomes complicated. .

An object of the present invention is to solve the above-mentioned problems of the prior art, and to measure the emittance of an ion beam without performing precise mechanical movement in a vacuum system. Is to provide.

[0009]

In order to achieve the above object, the ion beam emittance measuring apparatus according to the present invention has a longitudinal direction orthogonal to the deflecting electromagnet, which is a mass separator of the ion beam, in front of the deflecting electromagnet. Place the slit,
Further, a deflector having a deflection surface equal to the deflection surface of the deflection electromagnet is arranged in front of the slit, and further, a Faraday cup is arranged in front of the deflector.

[0010]

In the present invention, the ion beam emitted from the deflecting electromagnet, which is the ion beam mass separator, is limited to those which can pass through the slit, and the ion beam passing through the slit is deflected by the deflector. From, it flows into the Faraday cup. In that case, when the current flowing through the coil of the deflection electromagnet or the energy of the ion beam passing through the deflection electromagnet is changed, the trajectory radius of the ion beam in the deflection electromagnet is slightly changed. Further, the angular distribution of the ion beam that has passed through the slit can be known from the ion current measured by the Faraday cup when the deflection angle is changed by the deflector. Therefore, the emittance of the ion beam can be measured from the distribution of the ion current measured by the Faraday cup when the trajectory radius of the ion beam in the deflecting magnet and the deflection angle in the deflector are changed independently. .

[0011]

Embodiments of the present invention will be described below with reference to the drawings. An ion beam emittance measuring apparatus according to an embodiment of the present invention is shown in FIG. 1, in which a deflection electromagnet 11 which is an ion beam mass separator is shown.
In front of the slit 1 whose longitudinal direction is orthogonal to the deflection surface
2, a deflector 13 having a deflection surface equal to that of the deflection electromagnet 11 is disposed in front of the slit 12, and further, a Faraday cup 14 is disposed in front of the deflector 13. Has been done. The current flowing through the coil of the deflection electromagnet 11 or the energy of the ion beam passing through the deflection electromagnet is controlled, and the deflector 13
The control of the deflection angle is done independently.

In such an embodiment, the ion beam emitted from the deflecting electromagnet 11 which is a mass separator of the ion beam is limited to only those which can pass through the slit 12, and the ion beam which has passed through the slit 12 is limited. After being deflected by the deflector 13, it flows into the Faraday cup 14. In that case, when the current flowing through the coil of the deflection electromagnet 11 or the energy of the ion beam passing through the deflection electromagnet 11 is changed, the trajectory radius of the ion beam in the deflection electromagnet 11 is slightly changed. Further, the angular distribution of the ion beam passing through the slit 12 can be known from the ion current measured by the Faraday cup 14 when the deflection angle is changed by the deflector 13. Therefore, when the orbital radius of the ion beam in the deflection electromagnet 11 and the deflection angle in the deflector 13 are independently changed, the emittance of the ion beam is measured from the distribution of the ion current measured by the Faraday cup 14. be able to.

2, 3 and 4 are emittance diagrams (a space and an angular distribution of an ion beam in a phase space) of a deflecting surface, in which the horizontal axis is the position with respect to the optical axis, The vertical axis is the angle formed by the optical axis of the ion beam.

The emittance at the exit of the deflection electromagnet 11 is shown in FIG. 2 when the ion orbit radius at the deflection electromagnet 11 matches the original design value Ro.

Next, the current flowing in the coil of the deflection electromagnet 11 is changed, or the energy of the ions passing through the deflection electromagnet 11 is changed to slightly change the orbit radius of the ions in the deflection electromagnet 11. , The emittance at the exit of the bending electromagnet 11 moves obliquely in parallel as shown in FIG. At that time, the radius of the ion orbit is changed from Ro to Ro.
In order to change to + r, when changing the current flowing through the coil of the bending electromagnet 11, the current is multiplied by -r / Ro, and
When changing the energy of the ions passing through the deflecting electromagnet 11, the potential may be changed by r / 2Ro times.

It is shown in FIG. 4 that the slit 12 has a function of extracting a part of the emittance by restricting only the ion beam that can pass through the ion beam emitted from the deflecting electromagnet 11. When the distance between the slit 12 and the deflector 13 is Lo, the distance between the slit 12 and the Faraday cup 14 is L, and the deflection angle at the deflector 13 is θo, the ion beam incident on the Faraday cup 14 passes through the slit 12. The angle θ with the optical axis is
It is given by (1-Lo / L) θo. Using this relationship, the angular distribution of the ion beam passing through the slit 12 can be known from the ion current measured by the Faraday cup 14 when the deflection angle of the deflector 13 is changed.

By the way, the deflector 13 in the above embodiment.
May be an electrostatic deflector or an electromagnet. Further, for the angular distribution of the ion beam passing through the slit 12, a combination of the deflector 13 and the Faraday cup 14 was used, but instead of these, a function of measuring the spatial distribution of the ion beam sufficiently behind the slit 12 is used. A fixed Faraday cup may be used.

In the above embodiment, the change in the orbital radius of the ion beam at the deflecting electromagnet 11 and the total current of the ion beam passing through the slit 12 at that time are measured to determine the position of the slit 12 at the position. The spatial distribution of the deflection surface of the ion beam can be measured.

[0019]

Since the present invention has the above-mentioned structure, when the ion beam orbit radius in the deflection electromagnet and the deflection angle in the deflector are independently changed, the measurement is performed by the Faraday cup. The ion current emittance makes it possible to measure the emittance of the ion beam without performing precise mechanical movement in the vacuum system.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing the emittance at the exit of the deflection electromagnet when the ion orbit radius in the deflection electromagnet matches the original design value Ro in the embodiment of the present invention.

FIG. 3 is an explanatory view showing the emittance at the exit of the deflection electromagnet when the ion orbit radius in the deflection electromagnet is slightly changed in the embodiment of the present invention.

FIG. 4 is an explanatory diagram showing emittance when the passage of an ion beam is restricted by a slit in the embodiment of the present invention.

FIG. 5 is an explanatory view showing an example of a conventional ion beam emittance measuring device.

FIG. 6 is an explanatory view showing another example of a conventional ion beam emittance measuring device.

[Explanation of symbols]

 11 ・ ・ Bending electromagnet 12 ・ ・ ・ ・ ・ ・ Slit 13 ・ ・ ・ ・ ・ ・ Deflector 14 ・ ・ Faraday cup

Claims (1)

[Claims] 1. A deflection electromagnet, which is a mass separator for ion beams, is provided with a slit having a longitudinal direction orthogonal to that of the deflection electromagnet, and a deflection surface equal to the deflection surface of the deflection electromagnet is provided in front of the slit. An ion beam emittance measuring device characterized in that a deflector having the same is disposed, and further a Faraday cup is disposed in front of the deflector.