JPH0541298A - Cod detection device and cod correction device for circular accelerator - Google Patents

Abstract

PURPOSE:To detect and correct COD (closed orbit deviation) arranging no detection electrode or the like in a vacuum chamber, in a circular accelerator vacuum chamber such as a storage ring of an SOR equipment. CONSTITUTION:Vacuum ports 49 are drawn out from respective deflection sections 40 of a storage ring 22 in tangential directions. SOR light beams 54 introduced in the vacuum ports 49 are emitted from beryllium windows on the ends to observe with TV cameras 56 respectively. Deviations of electron beams circulating in the storage ring from the central orbit appear as deviations of positions on SOR light images, hence CODs can be obtained from observed images on the TV cameras 56. Then observed images on TV cameras 56 are inputted to a personal computer 66 through image processors 61-64, and horizontal and vertical CODs for respective deflection sections are detected in the personal computer 66, and magnetization of orbit adjusting electromagnets 44, 46 are controlled so as that both dispersions become minimal, to correct CODs.

Description

Detailed Description of the Invention

[0001]

This invention relates to a COD (closed orbit distortion) in a circular accelerator such as a synchrotron.
This is a device for detecting and correcting (closed orbit deviation) so that COD can be detected and corrected without disposing a COD detection electrode or the like in the circular accelerator vacuum chamber.

[0002]

2. Description of the Related Art In recent years, a synchrotron is expected to be applied as a synchrotron radiation (SOR) device to various fields such as creation of ultra-ultra LSI circuits, diagnosis in the medical field, molecular analysis, and structural analysis. The outline of the SOR device is shown in FIG. An electron beam generated by a charged particle generator (electron gun, etc.) 10 is accelerated by a linear accelerator (linac) 12 to near the speed of light, and a deflection electromagnet 16 of the beam transport unit 14 is accelerated.
It is deflected by and is incident on the storage ring (circular accelerator vacuum chamber) 22 via the inflector 18. The electron beam incident on the storage ring 22 is converged by the converging electromagnets 23 (for vertical direction) and 25 (for horizontal direction) while being given energy in the high-frequency acceleration cavity 21, and is deflected by the deflection electromagnet 24 to be stored in the storage ring 22. Keep going around. The SOR light generated when being deflected by the deflection electromagnet 24 is sent to, for example, the exposure device 28 through the beam channel 26, and is used as a light source or the like for creating an ultra-super LSI circuit.

In a circular accelerator such as a synchrotron, the central orbit is a periodic solution (that is, a closed orbit) of the particle equation of motion, and the center of gravity of the beam coincides with the central orbit. However, if there is an extra deflection magnetic field (error magnetic field) in the accelerator, the closed orbit will no longer coincide with the central orbit. The deviation of this closed orbit is called COD) (see FIG. 3).

COD causes various inconveniences when operating the accelerator. First, the reduced physical aperture of the accelerator shortens the life of the beam. In extreme cases,
The beam hits the vacuum chamber and does not rotate at all. In addition, when it is necessary to finely control the position and angle of the beam, such as beam injection, beam extraction, SOR beam position adjustment, noise reduction entering the physical experiment measuring instrument in the collider, it becomes difficult. ..

The COD can be reduced by reducing the cause of the error magnetic field (variation of the magnetic field of the deflection magnet, installation error of the quadrupole magnet, etc.), but there is a limit to that, and a correction system is required. ..

In this correction, the horizontal and vertical orbit adjusting electromagnets are usually arranged at several points in the accelerator, the horizontal and vertical CODs are detected at each position, and the COD deviation in each direction is detected. This is done by adjusting the amount of excitation of these orbit adjusting electromagnets so that the dispersion is minimized.

In the conventional COD detection, as shown in the sectional view of the accelerator in FIG. 4, button electrodes 31 to 34 are arranged above and below the accelerator vacuum chamber 22 as a beam position monitor, and when the beam passes therethrough. The beam positions in the horizontal direction and the vertical direction are obtained from the signal levels obtained at the respective electrodes by a predetermined arithmetic expression, and the deviations Δx and Δy of the actual beam orbit 2 from the central orbit 1 are obtained.

[0008]

In the COD detection by the beam position monitor of FIG. 4, the accelerator vacuum chamber 22 is used.
There is a drawback that the structure of the vacuum chamber is complicated because it is necessary to dispose a button electrode on the.

The present invention solves the above-mentioned problems in the prior art, and makes it possible to detect and correct COD without disposing electrodes or the like in the accelerator vacuum chamber, and a COD detection and COD correction device for a circular accelerator. Is to provide.

[0010]

The COD detector of the present invention is an image for observing an image of SOR light guided to the vacuum port and a vacuum port that is drawn out tangentially from the deflection part of the circular accelerator vacuum chamber. The observation means and the calculation means for obtaining the deviation of the particle beam trajectory from the central trajectory of the circular accelerator vacuum chamber based on the observation by the image observation means are provided.

Further, according to the deviation of the detected orbit, the COD correction device of the present invention adjusts the excitation amount of the orbit adjustment electromagnet arranged in the circular accelerator vacuum chamber so that the dispersion of the deviation of the orbit is minimized. It further comprises control means for controlling.

[0012]

According to the COD detection device of the present invention, the deviation of the beam in the circular accelerator vacuum chamber is S at the deflection position.
By utilizing the fact that the OR light appears as a deviation, the deviation of the orbit can be detected by observing the image of the SOR light with an image observation device such as a TV camera. According to this, since the observation of the image of the SOR light can be performed by utilizing the vacuum port which is usually provided in the deflection part in the circular accelerator vacuum chamber, COD detection is performed without complicating the structure of the accelerator vacuum chamber. be able to.

Further, according to the COD correction device of the present invention, the COD correction can be automatically performed based on the COD detection.

[0014]

FIG. 1 shows an embodiment of the present invention. In the storage ring (circular accelerator vacuum chamber) 22 of the SOR device, a deflection electromagnet 24 is arranged in each deflection portion 40, and each linear portion 42.
Focusing electromagnet (not shown), vertical orbit adjusting electromagnet 44,
A horizontal orbit adjusting electromagnet 46 and other electromagnets are arranged. The vertical and horizontal orbit adjusting electromagnets 44 and 46 are respectively configured as two-pole electromagnets that sandwich the vacuum chamber of the storage ring 22 and have their magnetic poles facing each other in the horizontal and vertical directions.

From the vacuum chamber of each deflecting section 40, two beam channels 48 and 49 are provided on the tangent line.
Have been pulled out. Of these, the SOR light 50 emitted from the beam channel 48 is guided to an exposure device or the like. The other beam channels 49 are used as vacuum ports for COD detection, and the SOR light 5 passes through a vacuum window 52.
4 is emitted. A TV camera 56 is arranged on the extension of the vacuum port 49 and observes an image of the emitted SOR light 54.

The images observed by the TV camera 56 of each deflecting section 40 are sent to the image processing devices 61 to 64, respectively, and the image output distributions (beam profile signals) in the horizontal and vertical directions are data as shown in FIG. 5, for example. Is output as.

The personal computer 66 serves as a calculation means and a control means, based on the image processing output, the horizontal deviation amount Δx and the vertical deviation amount Δy of the actual track 2 with respect to the central track 1.
Ask for. And i = 1, 2, 3, 4 (representing the four deflecting units 40) is calculated, and the horizontal orbit adjusting power supply 68 and the vertical orbit adjusting power supply 70 are controlled so as to minimize the values of both dispersions, and the horizontal orbit is adjusted. The amount of excitation of the adjusting electromagnet 46 and the vertical orbit adjusting electromagnet 48 is adjusted for each deflecting unit 40. As a result, automatic correction of COD is realized. It should be noted that the personal computer 66 is simply used as a calculation means, and the horizontal and vertical trajectory adjustment power source 6 is manually operated by the operator based on the deviation amount detected here.
COD correction can also be performed by adjusting 8, 70.

[0018]

MODIFICATIONS In the above embodiments, the case where the present invention is applied to the SOR device has been described, but the present invention can be applied to various other circular accelerators.

[0019]

As described above, the COD of the present invention
According to the detection device, by utilizing the fact that the deviation of the beam in the accelerator appears as the deviation of the SOR light at the deflection position,
The deviation of the orbit can be detected by observing the image of the SOR light with an image observation device such as a TV camera. According to this, since the observation of the image of the SOR light can be performed by utilizing the vacuum port which is usually provided in the deflection part in the circular accelerator vacuum chamber, COD detection is performed without complicating the structure of the accelerator vacuum chamber. be able to.

Further, according to the COD correction device of the present invention, the COD correction can be automatically performed based on the COD detection.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a plan view showing an outline of an SOR device.

FIG. 3 is an explanatory diagram of COD.

FIG. 4 is a cross-sectional view of an accelerator vacuum chamber showing a conventional beam position monitor.

5 is a diagram showing an example of output signals from the image processing devices 61 to 64 of FIG. 1. FIG.

[Explanation of symbols]

 1 Central orbit 2 Actual orbit (particle beam orbit) 22 Storage ring (circular accelerator vacuum chamber) 40 Deflection part 44, 46 Orbit adjustment electromagnet 49 Beam channel (vacuum port) 54 SOR light 56 TV camera (observation means) 66 PC ( Calculation means, control means)

Claims (2)

[Claims] 1. A vacuum port drawn out from a deflecting part of a circular accelerator vacuum chamber on its tangent line, an image observing means for observing an image of SOR light guided to this vacuum port, and an observation means for observing the image. Circular accelerator, a COD detection device for a circular accelerator, which comprises a calculating means for obtaining a deviation of a particle beam trajectory from a central trajectory of a vacuum chamber. 2. A vacuum port drawn out from a deflection part of a circular accelerator vacuum chamber on its tangent line, an image observation means for observing an image of SOR light guided to this vacuum port, and an observation means for observing the image. And calculating means for calculating the deviation of the particle beam orbit from the central orbit of the circular accelerator vacuum chamber, and controlling the excitation amount of the orbit adjustment electromagnet arranged in the circular accelerator vacuum chamber so that the deviation of the orbit deviation is minimized. A COD correction device for a circular accelerator, comprising: a control means.