JPH04249899A - Acceleration of small synchrotron - Google Patents

Abstract

PURPOSE:To increase accumulated electric current by preventing electron beams injected into an accumulation ring from disappearing after coming into collision with an inwall of the accumulation ring in the case of starting up the operation of a small synchrotron. CONSTITUTION:In the case of starting up operation of a small synchrotron, a standard signal generator 36 reads out exciting current patterns in the case of operating in respective operating modes memorized in a standard signal memory device 35 according to a mode changeover command from a mode changeover command device 37. Respective power sources 46, 47, 48, 49 and 50 for a deflecting electromagnet, a converging electromagnet and an orbit adjusting electromagnet control exciting current according to these exciting current patterns so that excitation volume of these respective electromagnets can be changed in an approximately analogous pattern.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small synchrotron and is intended to increase the accumulated current value.

0002

[Prior Art] In recent years, small synchrotrons are expected to be used as synchrotron radiation (SOR) devices in various fields such as the creation of ultra-super LSI circuits, diagnosis in the medical field, molecular analysis, and structural analysis. .

FIG. 2 shows an outline of a compact synchrotron radiation device. An electron beam generated by a charged particle generator (electron gun, etc.) 10 is accelerated to near the speed of light by a linear accelerator (linac) 12, deflected by a deflection electromagnet 16 of a beam transport section 14, and accumulated via an inflector 18. ring 22
Injected into the inside. The electron beam incident on the storage ring 22 is given energy by the high-frequency acceleration cavity 21, focused by the focusing electromagnets 23 (for vertical direction) and 25 (for the horizontal direction), and deflected by the deflection electromagnet 24 into the storage ring 22. Continue to rotate. Synchrotron radiation generated when deflected by the deflection electromagnet 24 is sent through a beam channel 26 to, for example, an exposure device 28, where it is used as a light source for producing ultra-super LSI circuits.

In a small synchrotron device, since the acceleration energy of the linac 12 as an injector is low, the beam diameter of charged particles incident on the storage ring 22 expands, collides with the inner wall of the storage ring 22, and disappears. However, it is difficult to increase the accumulated current value in the storage ring 22.

Therefore, as an operating method at startup, for example, as shown in FIG. 3, each time an electron beam is incident on the storage ring 22, the beam energy within the storage ring 22 is rapidly increased or decreased to cause radiation attenuation. After accumulating a predetermined amount of electron beam (injection operation A), the beam energy is increased to the final energy (acceleration operation B), and the energy is maintained constant thereafter (accumulation operation C) in order to increase the current. ing. In order to perform such operation, the bending electromagnet 24
The magnetic fields generated by the magnets and converging electromagnets 23 and 25 are controlled according to predetermined magnetic field patterns, respectively.

[0006]

[Problem to be Solved by the Invention] By synchronously controlling and starting up the excitation amounts of the deflecting electromagnet 24 and the focusing electromagnets 23 and 25 in a predetermined pattern as described above, it is possible to prevent the electron beam from reaching the inner wall of the storage ring. However, if the current density is increased beyond a certain level, the electron beam will collide with the inner wall of the storage ring 22 and disappear, making it impossible to increase the current density to the final target value. was difficult.

The present invention solves the problems in the conventional techniques and provides a synchrotron acceleration method that further increases the current density by further suppressing the collision of the electron beam with the inner wall of the storage ring. This is what I am trying to do.

[0008]

[Means for Solving the Problem] The present invention involves changing the amount of excitation of a deflection electromagnet, a focusing electromagnet, and an orbit adjustment electromagnet in a substantially similar pattern during the injection, acceleration, and accumulation processes of a small synchrotron. This is a characteristic feature.

[0009]

[Operation] Conventionally, the operation of the orbit adjustment electromagnet is as follows:
A constant amount of excitation was given that was optimal for electron beam injection. It has been found that in this operating method, when the energy is increasing, the amount of excitation is too small and the electron beam tends to collide with the inner wall of the storage ring.

Therefore, in the present invention, in the process of injection, acceleration, and accumulation of a small synchrotron, the amount of excitation of not only the deflecting electromagnet and the focusing electromagnet but also the orbit adjustment electromagnet is changed in a pattern that is almost similar to these. ,
This prevents the electron beam from colliding with the inner wall of the storage ring due to an inappropriate amount of excitation of the orbit adjustment electromagnet, making it possible to further increase the current density.

[0011]

[Embodiment] An embodiment of the present invention will be described below. In FIG. 1, deflection electromagnets 24 for deflecting the electron beam are provided at the four corners of the storage ring 22 around which the electron beam circulates, and each straight portion of the storage ring 22 sandwiched between these deflection electromagnets 24 is provided with a beam of the electron beam. Quadrupole electromagnets 23 (horizontal) and 25 (vertical) are provided for convergence to narrow down the size. In addition, one of the straight parts of the storage ring 22 has a
A high frequency acceleration cavity 21 is provided which supplies energy to the electron beam.

When the electron beam accelerated by the linear accelerator 12 (FIG. 2) enters the storage ring 22 from the inflector 18, its trajectory is bent by the bending electromagnet 24, and the beam size is narrowed by the focusing electromagnets 23 and 25. and circulates within the storage ring 22 while being supplied with energy by the high frequency acceleration cavity 21.

Further, each linear portion of the storage ring 22 is provided with a horizontal trajectory adjustment electromagnet 31 for adjusting the horizontal trajectory of the electron beam and a vertical trajectory adjustment electromagnet 33 for adjusting the vertical trajectory. ing. Each of these is composed of two-pole electromagnets with magnetic poles facing each other with the storage ring 22 in between (horizontal type facing vertically, vertical type facing horizontally), so that the electron beam passes through the center orbit inside the storage ring 22. The amount of excitation is individually controlled for each.

Digital computer 45 constituting the control device
During each operation of injection operation, acceleration operation, and accumulation operation,
A reference signal storage device 35 is provided in which unit patterns of excitation current waveforms supplied to the deflection electromagnet 24, convergence electromagnets 23, 25, and orbit adjustment electromagnets 31, 33 are stored. The unit pattern of the injection operation is, for example, a trapezoidal pattern as shown in FIG. 4(b). For example, the unit pattern of acceleration and accumulation operation is as shown in FIG.
This is a pattern in which the rise stops after a predetermined period of time and shifts to a flat state (accumulation). These unit patterns are for each electromagnet 2
4, 23, 25, 31, and 33 have substantially similar waveforms, and their gradients can be set for each electromagnet to a value that allows convenient startup by actually operating the synchrotron. .

The reference signal storage device 35 is connected online to a reference signal generator 36, and the reference signal generator 36 is connected online to a mode switching command device 37 that selects each operation mode of injection, acceleration, and accumulation. . and,
The reference signal generator 36 is used in the input operation as shown in FIG. 4(a).
The waveform pattern of is stored in the reference signal storage device 3 according to the clock.
In acceleration and accumulation operations, the waveform pattern shown in FIG. 4(b) is read out from the reference signal storage device 35 according to the clock, and
A series of excitation current waveform patterns (approximately similar patterns for each electromagnet) are created every 5, 31, and 33.

The reference signal generator 36 is an incident timing generator that synchronizes the incident timing of the electron beam that is accelerated by the linear accelerator 12 (FIG. 2) and enters the storage ring 22 with the operation of each mode. 38, and furthermore, a clock generator 39 that generates a clock for synchronizing the digital computer 45.

The excitation current waveform pattern of each electromagnet outputted from the reference signal generator 36 is transmitted to the data transmission device 4.
0, and from this data transmission device 40 respectively D/A
Via the converters 41 to 45, a bending electromagnet 46, a horizontal focusing electromagnet power supply 47, a vertical focusing electromagnet 48, a vertical orbit adjustment electromagnet power supply 49, and a horizontal orbit adjustment electromagnet power supply 5 are provided.
0.

The operation of this embodiment having the above configuration will be described. FIG. 5 shows a flowchart for outputting the excitation current waveform pattern performed within the reference signal generator 36 shown in FIG. 1. When the operation is started, the injection operation is first commanded, and the unit pattern shown in FIG. is output. Repeat this injection operation pattern a set number of times,
Alternatively, when it is detected that the current density in the storage ring 22 has reached a predetermined value, the mode switching command device 37 switches to acceleration and storage operation, which is synchronized again with the incident timing of the electron beam, as shown in FIG. 4(b). The acceleration and accumulation operation unit pattern is output, and the switching from the incidence operation to the acceleration and accumulation operation is performed. Changes in the excitation current of each electromagnet during this series of operations have approximately similar patterns as shown in FIG. In addition, each orbit adjustment electromagnet power supply 49
, 50, the gradient of change can be individually set so that the amount of excitation necessary for orbit adjustment is finally obtained.

By performing the switching operation from the injection operation to the acceleration and accumulation operation in this way, a large number of electron beams are incident into the storage ring 22 during the injection operation, the storage current becomes large, and the storage ring 22 receives a large number of electron beams. A predetermined amount of electron beams will circulate. Therefore, after this, if the electron beam in the storage ring 22 is switched to acceleration and storage operation in which the electron beam is increased to a predetermined energy, it is possible to obtain a practically usable SOR light of a predetermined amount and a predetermined energy. In particular, not only the deflecting electromagnet 24 and the converging electromagnets 23, 25, but also the orbit adjustment electromagnets 31, 33 are changed in a pattern that is almost similar to these, so that each of these electromagnets is Since the excitation amount corresponds to the accumulated current value at each point in time, it is possible to reduce the number of electrons that collide with the inner wall of the storage ring and disappear, and it is possible to increase the accumulated current value to a desired value.

[0020]

[Modification] In the above embodiment, the excitation amount of both the vertical and horizontal orbit adjustment electromagnets was controlled according to the present invention, but a certain degree of effect can be obtained even if only one of them is used.

[0021]

[Effects of the Invention] As explained above, according to the present invention, in the process of injection, acceleration, and accumulation of a small synchrotron, the amount of excitation of not only the deflection electromagnet and the focusing electromagnet but also the orbit adjustment electromagnet can be changed. Since the changes are made in a similar pattern, it is possible to prevent the electron beam from colliding with the inner wall of the storage ring due to an inappropriate excitation amount of the orbit adjustment electromagnet, and it is possible to further increase the current density.

[Brief explanation of the drawing]

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

FIG. 2 is a plan view showing an outline of a small synchrotron.

FIG. 3 is a diagram showing an example of a beam energy start-up pattern of a small synchrotron.

4 is a diagram showing unit patterns of excitation current in each operation mode stored in the reference signal storage device 35 of FIG. 1; FIG.

FIG. 5 is a flowchart showing an example of output control of an excitation current pattern by the reference signal generator 36 of FIG. 1;

6 is a diagram showing an example of an excitation current pattern output from the reference signal generator 36 of FIG. 1. FIG.

[Explanation of symbols] 22 Storage ring 23 Convergence electromagnet (horizontal) 24 Bending electromagnet 25 Convergence electromagnet (for vertical) 31 Electromagnet for orbit adjustment (horizontal) 33 Orbit adjustment electromagnet (for vertical)

Claims (1)

[Claims] 1. Acceleration of a small synchrotron characterized by changing the excitation amount of a bending electromagnet, a focusing electromagnet, and an orbit adjustment electromagnet in a substantially similar pattern during the injection, acceleration, and accumulation processes of the small synchrotron. Method.