JPH02263191A - Beam advance direction measuring instrument - Google Patents

Abstract

PURPOSE:To measure the advance direction of a beam by moving a beam shielding means, while irradiating a beam detecting means with a beam, and processing a detecting signal as a function of a signal for showing a relative position of the beam shielding means to the beam detecting means. CONSTITUTION:For instance, an ion beam is made incident toward a detecting head 14 from the direction as indicated with an arrow. A shielding held 16 moves from the right to the left, and when it comes to a position of a broken line, the detecting head 14 is shielded completely by the beam. In this case, when a distance between the detecting head 14 and the shielding head 16 is (w), and the tip of the shielding head 16 protrudes forward by length d' from the tip of the detecting head, an incident angle theta' of the beam becomes theta'= arctan (d'/w). In such a way, the protrusion length d' is obtained, and the angle theta' is calculated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a beam traveling direction measuring device, and more particularly to a device for measuring a beam traveling direction that cannot be directly observed.

In equipment that handles charged particle beams, knowing where and in what direction the beam is currently traveling is necessary information for equipment adjustment, etc. Precise knowledge of the beam's position and direction allows the beam to be used to maximum effect.

[Prior art] Ions are supplied at the center of a planar gap between magnetic poles, are accelerated by a tee, which is a high-frequency electrode for acceleration, and gradually move outward in a spiral pattern, and are deflected to the outside by a deflector. This will be explained using a cyclotron that is drawn out as an example.

Figure 2 schematically shows ion orbits within the cyclotron. In FIG. 2, a cone support tube 50 disposes an ion source 51 in the center. An ion beam 52 emitted from an ion source 51 is accelerated by an electric field between days 55 and 56 to which a high frequency voltage is applied from a high frequency power source 57, and is given a centripetal force in a strong magnetic field formed in the direction of the front and back of the paper. Forms a spiral trajectory.

When an ion beam is introduced into the entrance of the deflector electrode 60 at the outermost part of the ion trajectory, the ion beam is deflected by the deflector electrode 60 and taken out to form an extracted ion beam 61 .

In order to obtain a high-intensity ion beam, it is necessary to properly guide the beam to the entrance of the deflector during beam adjustment of the cyclotron, and to take it out without colliding with the wall. Conventionally, ion beam adjustment has been performed by changing various parameters through trial and error.

[Problems to be Solved by the Invention] As described above, in the beam adjustment of conventional cyclotrons, although the introduction of the beam flux into the deflector cannot be easily adjusted to the optimum condition, the incidence of the beam flux introduced into the deflector is No measures were taken to measure and control the angle.

Even in other devices that handle beams that cannot be directly observed, beam identification has at most been accomplished by forming a visible image of the beam cross section on a screen or by scanning a globe. Until now, no device has been provided that measures not only the position of the beam but also its direction of travel.

An object of the present invention is to provide a beam traveling direction measuring device that measures the traveling direction of a beam.

Another object of the present invention is to provide a beam traveling direction measuring device that can measure the beam traveling direction as well as the beam position.

For example, in a cyclotron, if the angle of incidence of a beam on a deflector is known, adjustment can be simplified and, in turn, it can contribute to reducing deflector activation.

[Means for solving the problem] The beam shielding means for the beam detection means is moved by moving the beam shielding means capable of shielding the beam in front of the beam detection means capable of detecting the beam while irradiating the beam with the beam detection means capable of detecting the beam. processing the detection signal of the beam detection means as a function of the signal representative of the relative position of the beam detection means;

An output signal is obtained indicating the relative position at which the beam is no longer incident on the detection means.

[Operation] FIG. 1 schematically shows the measurement principle of the present invention. In the figure, A indicates the position of the beam detection means, and B indicates the position of the beam shielding means.

Assume that a beam is incident on the beam detection means A. At this time, it is assumed that the beam shielding means is moved and when it comes to position B, the beam no longer enters the beam detecting means A. If the beam moves linearly, the direction connecting A and B is the direction of incidence of the beam. Therefore, if the relative position of point B to point A is known, the direction of the incident beam indicated by the arrow can be determined.

If the coordinates of point A are (x, y), and the coordinates of point B are (X + Δx, y + Δy), then Δ
By knowing X and Δy, the angle θ can be calculated from the laws of trigonometric functions.
can be known.

Detecting ΔX and Δy from the position of the shielding means B and calculating the angle θ can be realized using an electric circuit.

[Embodiment] FIGS. 3(A) and 3(B) show a beam traveling direction measuring device in a cyclotron device which is an embodiment of the present invention.

In FIG. 3(A), a gap is formed between the deflector electrode 10 and the septum electrode i12 through which the beam passes. It is assumed that the ion beam is incident from below in the figure.

A detection head 14 is arranged in front of the beam entrance formed by the deflector electrode 10 and the septum electrode 12. The detection head is formed of, for example, a metal electrode plate, and has a configuration in which a current corresponding to the beam current flows when the ion beam is incident thereon.

A shielding head 16 is arranged in front of the detection head 14 at a predetermined location, which is arranged parallel to the detection head and is movable in translation relative to the detection head. The shielding head 16 is made of, for example, graphite, and is electrically insulated from the detection head 14.

The position of the shield head 16 is precisely controlled by a drive means such as a drive motor 18 , and its relative position signal is supplied to a signal processing circuit 20 . The current received by the detection head 14 is processed as a detection signal! ? 820. Detection signal from detection head 14 and drive motor 18
The relative position signal from is connected to the CPU 23 via the interface 21. In the signal processing circuit 20, a CPU 23 processes signals and performs logical operations, and a memory 25 stores necessary information and retrieves the stored information as necessary.

Also, two display devices or two interfaces for display devices.
7, and the operator can read necessary information on the screen of the display device 29.

Further, a drive current to the drive motor 18 is also supplied from the signal processing circuit 20 .

In beam adjustment, the detection head 14 is connected to the deflector electric [
! The ion beam is placed in front of the beam entrance formed by the septum electrode 10 and the septum electrode 12, and the ion beam is first adjusted so that the ion beam properly enters the beam entrance. However, if the direction of the ion beam is not known at this time, the ion beam will collide with the surface of the deflector electrode 10 or septum electrode 12 and disappear. After adjusting so that the ion beam irradiates the tip of the detection head 14, the shielding head 16 is operated to gradually shield the ion beam.

If the shielding head 16 has almost completely shielded the ion beam, the current will be reduced to zero since no ion beam will be incident on the detection head.

FIG. 3(B) shows an enlarged view of the measuring head portion.

Assume that an ion beam is incident toward the detection head 14 from the direction of the arrow. When the shielding head 16 moves from right to left in the figure and reaches the position indicated by the broken line, the detection head 14 is completely shielded from the beam. At this time, if the distance between the detection head 14 and the shielding head 16 is W, and if the tip of the shielding head 16 or the tip of the detection head is protruded by a length do, then the beam incidence angle θ゛ becomes θ' = arctan (d' 7w ).

Since the distance W between the heads is a constant, the protrusion length d' is determined by signal processing the electric signal representing the amount of movement of the shielding head 16 and the ion current detected by the detection head 14.
and calculate the angle θ°.

FIG. 4 is a graph showing how the detected ion beam current changes with respect to the scanning distance of the shielding head.

As the scanning distance of the shielding head increases, the detection beam current reaches a certain value and then gradually begins to decrease.The rate of decrease gradually changes and approaches zero.In Figure 9, the beam current changes almost linearly. The decreasing portion is considered to be a signal while the shielding head 16 is gradually shielding the beam.

The reason why the beam current decreases or becomes gradual in the end is that the beam flux originally has a certain spread in the radial direction, and components that are incident from directions other than the beam traveling direction shown by the arrows in Figure 3 (B) This is probably due to the fact that it also includes Therefore, by linearly approximating the reduced portion and finding the point d that intersects the X-axis, the desired protrusion distance d° of the shielding head can be obtained.

This operation of determining the position of do can be realized using a logic circuit.

n In this way, the shielding head 1 relative to the detection head 14
By measuring the ion beam current detected by the detection head 14 while measuring the relative position of the ion beam 6, the incident angle of the ion beam can be measured.

Furthermore, by knowing the position of the detection head 14 itself,
It is also possible to know the position of the beam itself.

Therefore, by knowing the position of the beam and its traveling direction, a device that handles the beam, such as a cyclotron, can be adjusted with high precision.

Above, we have explained an example of measuring the traveling direction of a charged beam using a cyclotron that handles ion beams in a vacuum container. The present invention can also be applied.

FIG. 5 shows another embodiment of the invention.

The detection head 34 has a planar detection surface, and has a large number of detection elements arranged in a matrix within the detection surface. That is, when a beam is incident on the detection surface of the detection head 34, it can be known which detection element the beam is incident on.

The shielding head 36 is also planar and has sides parallel to the rows and columns of the detection elements Dij of the detection head 34. This shielding head 36 can move two-dimensionally parallel to the plane of the detection head 34.

At least some of the detection elements Dij of the detection head 34 are irradiated with a beam, and the shielding head 36 is scanned two-dimensionally to measure how the detection current of each detection element DiJ changes. The direction of incidence of the incident beam can be measured three-dimensionally.

Although the embodiments have been described above, the present invention is not limited thereto. For example, it will be obvious to those skilled in the art that various changes, modifications, improvements, combinations, etc. are possible.

[Effects of the Invention] As described above, the traveling direction of a beam can be measured in a device that handles invisible beams.

By knowing the direction in which the beam travels, it is possible to effectively adjust the equipment that utilizes the beam and make full use of its capabilities.

[Brief explanation of drawings]

Fig. 1 is a conceptual diagram showing the measurement principle of the present invention, Fig. 2 is a schematic plan view for explaining ion orbits in the cyclotron, and Fig. 3 (A) and (B) show examples of the present invention. 3(A) is a block diagram of the measurement system, and FIG. 3(A) is a block diagram of the measurement system.
B) is an enlarged view of the measuring head part, FIG. 4 is a graph showing how the detected beam current changes as the shielding head scans, and FIG. 5 is a partial perspective view showing another embodiment of the present invention. It is a diagram. In the figure, 10 deflector electrode 12 septum electrode 21, 27 55, 56 detection head shield head drive motor signal processing circuit interface PU memory display device to detection head shield Rad cone support tube ion source ion beam day radio frequency power supply deflector electrode extraction ion beam re-substitute Person Patent Attorney Kei Takahashi Shibeju-to＼～, Betsu ℃

Claims (3)

[Claims] (1) A beam detection means capable of generating an electrical detection signal according to the beam amount by direct exposure to the beam, and a beam detection means capable of shielding the beam and controlling the relative position with respect to the beam detection means. relative position signal generating means capable of generating an electrical relative position signal representative of this relative position; and relative position signal generating means capable of generating an electrical relative position signal representative of this relative position; and a signal processing circuit that processes the electrical detection signal. (2) the signal processing circuit determines the position at which the beam shielding means completely shields the beam incident on the beam detection means for the first time from a change in the electrical detection signal as a function of the electrical relative position signal; 2. The beam traveling direction measuring device according to claim 1, wherein the beam traveling direction is calculated by determining the beam traveling direction. (3), further comprising a position measuring means capable of generating an electric absolute position signal representing the absolute position of one of the beam detecting means and the beam shielding means, the position measuring means being capable of generating an electric absolute position signal representing the absolute position of one of the beam detecting means and the beam shielding means; 3. A beam traveling direction measuring device according to claim 1, which is capable of measuring a beam traveling direction.