JPH08293399A - Charged particle accelerator - Google Patents

Abstract

PURPOSE: To smoothly operate a charged particle accelerator by generating a current reference value by a current reference value memory, and generating a frequency reference value of the accelerating voltage by a frequency reference value memory by the same operating clock from a time clock generator. CONSTITUTION: A current reference value memory 7a generates a current reference value of the current to be output from an electromagnetic power source 10, and a frequency reference value memory 7b generates an accelerating voltage reference value by a calculator 8 by the same operating clock from a time clock 14. Therefore, the magnetic field B formed by the current to be supplied from the electromagnetic power source 10 and the accelerating frequency (f) from an oscillator 6 are synchronized with each other, and the smooth operation can be performed. That is, the accelerating voltage is oscillated by the oscillator 6 at the accelerating frequency (f) and amplified by a high-frequency amplifier 4 through an amplitude control circuit 5, and the large power high frequency having synchronization required for acceleration of charged particle beams is supplied to an acceleration cave 3. Therefore, the conventional reference electromagnet, the magnetic field measuring unit and the magnetic field clock generator are dispensed with, and the simplification of the system is achieved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable frequency charged particle accelerator for accelerating charged particles such as electrons, protons and ions.

[0002]

2. Description of the Related Art For example, there is a synchroton as an accelerator for accelerating charged particles such as electrons, protons and ions. FIG. 3 is a block diagram showing a configuration of a high frequency acceleration system of such a synchrotron.

The main components of the synchrotron are:
There are a deflection electromagnet 1 for bending a beam of charged particles, a quadrupole electromagnet 2 for converging the beam of charged particles, and an acceleration cavity 3 for accelerating the beam of charged particles. The deflecting electromagnet 1 bends the charged particle beam and controls it so as to form an appropriate orbit. This is performed by controlling the strength of the magnetic field of the deflection electromagnet 1 according to the energy of the charged particle beam.

On the other hand, as the accelerating cavity 3 applies an accelerating voltage to accelerate the charged particle beam, the velocity of the charged particle beam increases. In this case, since the charged particle beam orbits the same orbit, the orbiting frequency increases as the charged particle beam accelerates. Therefore, it is necessary to increase the acceleration frequency of the acceleration voltage according to the acceleration of the charged particle beam. The acceleration frequency f is shown by the following equation (1).

[0005]

[Equation 1]

The magnetic field B of the deflection electromagnet 1 is represented by a function of the current value I (t) flowing in the deflection electromagnet 1 as shown in the following equation (2). Here, it is shown that the current value I (t) is a function of time t.

B = G (I (t)) (2) FIG. 4 shows an operation pattern of the synchrotron in this case. Time t1 after the charged particle beam is incident
Then, the charged particle beam starts to be accelerated and is emitted after time t2 when the maximum energy is reached. To this end, the bending electromagnet 1
It is necessary to control the magnetic field B of 1 with high precision. That is, (1)
The accelerating frequency f of the accelerating voltage in the accelerating cavity 3 is obtained from the equation, and the current value I of the electromagnet power source 10 that gives a current to the deflection electromagnet 1 is controlled with high accuracy, and the appropriate magnetic field B of the deflection electromagnet 1 is obtained from the equation (2). Need to ask.

The function G (I (t)) in the equation (2) does not fit into a clean calculation equation due to the saturation property of the magnetic permeability of the deflection electromagnet 1. Therefore, as shown in FIG. 3, the current value I of the deflection electromagnet 1 controls the current value of the electromagnet power supply 10 from the current reference value memory 7a which is driven by the time clock of the time clock generator 14. Then, the resulting magnetic field B is applied to the reference electromagnet 1
The magnetic field clock of the frequency reference value memory 7b that determines the acceleration frequency f is generated by the signal of the magnetic field clock generator 13 that outputs a pulse in response to the change of the magnetic field B by actually measuring with the magnetic field measuring device 1 of No. 1. . The magnetic field clock is also used as a clock for the acceleration voltage reference value memory 7c and the bias current reference value memory 7d. The acceleration voltage reference value memory 7c supplies the acceleration voltage reference value to the amplitude modulator 5 that temporally controls the amplitude of the acceleration voltage.
On the other hand, the bias current reference value memory 7d supplies a tuning reference value to the bias power supply 9 for tuning the acceleration cavity 3.

Next, the frequency reference value memory 7b stores the conversion table of the above equation (1). The oscillating voltage is oscillated by the oscillator 6 at the accelerating frequency f thus determined, amplified by the high frequency amplifier 4 via the amplitude control circuit 5, and synchronized with the accelerating cavity 3 necessary for accelerating the charged particle beam. Supply high power high frequency.

Thus, it is necessary to match the magnetic field B of the deflection electromagnet 1 with the acceleration frequency f of the acceleration voltage in advance. This is because if the magnetic field B of the deflection electromagnet 1 and the acceleration frequency f of the acceleration voltage are deviated, the charged particle beam will be lost.

Here, the literature Nuclear Instruments and Me
thords A336 (1993) 391-409 (RF acceleration system
A similar block diagram is also introduced in Fig. 16 of at cooler synchrotron TARN II). In addition, the literature Int. J. Mod. Phys.
A (proc.Suppl) 2A (1993) P763-765 (Successful Appl)
ication of Digially Controled RF Accelerating Syst
A similar block diagram is also introduced in Fig.1 of em for HIMAC Synchrotorns).

Such a magnetic field clock is necessary because the feedback system (not shown) has a narrow response range, and a frequency reference value corresponding to the magnetic field B must be output. In addition, the accuracy of the current control by the computer 8 was poor, and the required accuracy could not be obtained unless the magnetic field B was actually measured.

[0013]

However, in such a conventional charged particle accelerator, as is apparent from FIG. 3, the time clock generator 14 and the magnetic field clock generator 13 are provided.
Two clock generators are required and control is complicated. When considering the pattern of the current reference value memory 7a,
Since the current reference value pattern is made on the time axis and the acceleration frequency pattern is made on the magnetic field B, the correlation is difficult.
Further, the reference electromagnet 11 and the magnetic field measuring device 12 are required to generate the magnetic field clock. An object of the present invention is to obtain a charged particle accelerator which operates with a time clock, has simple control, and has a simple device configuration.

[0014]

According to the invention of claim 1, an electromagnet power source for supplying a current to a deflection electromagnet for bending a beam of charged particles, and a current reference value for generating a current reference value of the current output from the electromagnet power source. A memory and an oscillator for outputting an accelerating voltage to an accelerating cavity for accelerating a beam of charged particles,
A computer that calculates the acceleration frequency pattern of the acceleration voltage corresponding to the pattern of the current reference value generated from the current reference value memory, and a frequency reference that generates the frequency reference value of the acceleration voltage according to the acceleration frequency pattern of the acceleration voltage calculated by the computer. It has a value memory and a time clock generator for supplying the same operating clock to the current reference value memory and the frequency reference value memory.

According to a second aspect of the present invention, there is provided an amplitude control circuit for controlling the amplitude of the acceleration voltage from the oscillator, and an acceleration voltage reference memory for outputting the acceleration voltage reference value to the amplitude control circuit. In addition, the time clock generator supplies the same operation clock to the acceleration voltage reference memory.

According to a third aspect of the present invention, a bias power source for tuning the acceleration cavity and a bias current reference value memory for controlling the bias power source are provided in addition to the invention of the first or second aspect, and the time is set. The charged particle accelerator according to claim 1, wherein the clock generator supplies the same operation clock to the bias current reference value memory.

[0017]

According to the present invention, when the pattern of the current reference value generated from the current reference value memory is determined, the current reference value pattern is stored in the current reference value memory.
On the other hand, when the pattern of the current reference value generated from the current reference value memory is determined, the computer calculates the acceleration frequency pattern of the accelerating voltage corresponding to the pattern of the current reference value, and the acceleration oscillated from the oscillator in the frequency reference value memory. The acceleration frequency pattern of voltage is stored. The current reference value memory and the frequency reference value memory generate the current reference value of the current output from the electromagnet power source with the same operation clock from the time clock generator, and the frequency reference value memory A frequency reference value of the acceleration voltage is generated according to the frequency pattern of the acceleration voltage calculated by the computer. As a result, the magnetic field due to the current supplied from the electromagnet power source and the acceleration frequency from the oscillator are correctly synchronized, and smooth operation can be performed.

According to the invention of claim 2, in addition to the operation of claim 1, the amplitude control circuit is based on the acceleration voltage reference value output from the acceleration voltage reference memory to the amplitude control circuit by the clock from the time clock generator. Controls the amplitude of the acceleration voltage from the oscillator.

According to the invention of claim 3, in addition to the operation of claim 1 or claim 2, based on the bias current reference value output from the bias current reference value memory to the bias power supply by the clock from the time clock generator. Tune the acceleration cavity with a bias power supply.

[0020]

Embodiments of the present invention will be described below. FIG. 1 is a block diagram showing the first embodiment of the present invention. The first embodiment is an embodiment of a system of a non-tuning accelerating cavity with a low accelerating voltage used in a compact proton synchrotron.

First, when the pattern of the current reference value generated from the current reference value memory 7a is determined, the current reference value pattern is stored in the current reference value memory 7a. On the other hand, when the pattern of the current reference value generated from the current reference value memory 7a is determined, the computer 8 calculates the acceleration frequency pattern of the acceleration voltage corresponding to the pattern of the current reference value, and the oscillator 6 is stored in the frequency reference value memory 7b. The acceleration frequency pattern of the acceleration voltage oscillated from is stored. Then, the current reference value memory and the frequency reference value memory 7b generate the current reference value of the current output from the electromagnet power source 10 at the same operation clock from the time clock generator 14, and The reference value memory 7b is the computer 8
A frequency reference value of the accelerating voltage is generated according to the frequency pattern of the accelerating voltage calculated in. As a result, the electromagnet power source 1
The magnetic field B due to the current supplied from 0 and the acceleration frequency f from the oscillator 6 are correctly synchronized, and smooth operation can be performed. That is, the oscillating voltage is oscillated by the oscillator 6 at the accelerating frequency f, amplified by the high frequency amplifier 4 via the amplitude control circuit 5,
The acceleration cavity 3 is supplied with the synchronized high-power high-frequency required for accelerating the charged particle beam.

In the computer 8, the current I of the deflection electromagnet 1 is
And the conversion table of the measured values of the magnetic field B and the equation (1) are stored. When the current reference value as a function of time of the electromagnet power supply 10 is created according to the acceleration pattern required for accelerating the charged particle beam, the calculator 8 automatically calculates the acceleration frequency pattern of the accelerating voltage. This calculation is performed based on the conversion table of the actual values of the current I of the deflection electromagnet 1 and the magnetic field B and the equation (1). The acceleration frequency pattern which is the calculation result is stored in each reference value memory 7.

Reference values are output from the current reference value memory 7a and the frequency reference value memory 7b in accordance with the clock of the time clock generator 11. As a result, the charged particle beam is bent by the magnetic field B of the deflection electromagnet 1 due to the current supplied from the electromagnet power supply 10. On the other hand, the high frequency emitted from the oscillator 6 is amplified by the high frequency amplifier 9 and supplied to the acceleration cavity 3 to accelerate the charged particle beam. At this time, the magnetic field B of the deflecting electromagnet 1 and the acceleration frequency f are numerically matched, the time is synchronized correctly, and the charged particle beam can be correctly accelerated.

In this case, the reference electromagnet 11, the magnetic field measuring device 12 and the magnetic field clock generator 13 of the conventional example are unnecessary,
The charged particle accelerator system can be simplified. Also, when creating the pattern of the reference value, it is sufficient to consider only the time axis,
This has the effect of increasing the creation efficiency.

Next, a second embodiment of the present invention will be described.
FIG. 2 shows an embodiment of a system of a tunable accelerating cavity used in a proton or ion synchrotron having a high accelerating voltage. The basic configuration of this second embodiment is the same as that of the first embodiment shown in FIG.
The acceleration voltage reference memory 7c for outputting the acceleration voltage reference value to the amplitude control circuit 5 for controlling the amplitude of the acceleration voltage from the oscillator 6 and the bias power supply 9 for tuning the acceleration cavity 3 And a bias current reference value memory 7d for controlling the above. Then, the time clock generator 14 supplies the same operation clock to the acceleration voltage reference memory 7c and the bias current reference value memory 7d.

That is, in order to tune the acceleration cavity 3, the current value of the bias power supply 9 for supplying a bias current to the ferrite winding is synchronized with the acceleration frequency f. Further, the amplitude of the acceleration voltage is temporally controlled by the amplitude modulator 5. These reference values are also generated by the computer 8 and controlled in the same manner as the current value I and the acceleration frequency f of the other electromagnet power source 10 with a single time clock.

[0027]

As described above, according to the present invention, the reference electromagnet, the magnetic field measuring device and the magnetic field clock generator, which are required in the frequency variable type synchrotron, are not required, and the system can be simplified. Also, when creating the pattern of the reference value, the pattern of the function of the magnetic field becomes unnecessary, and it is sufficient to consider only the pattern of the function of time, and the efficiency of the driver in creating the pattern is improved.

As described above, in the present invention, the clock for the magnetic field is not required, and the current and frequency can be controlled only by the time clock. This is because the response range of the feedback system was expanded, and the accuracy of the current control by the computer was improved by learning control, etc., and the accuracy of the current reference value, that is, the magnetic field reference value and the actual magnetic field was improved.

[Brief description of drawings]

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

FIG. 2 is a block diagram showing a second embodiment of the present invention.

FIG. 3 is a block diagram showing a conventional example.

FIG. 4 is a characteristic diagram showing an operation pattern of a charged particle accelerator.

[Explanation of symbols]

 1 Bending Electromagnet 2 Quadrupole Electromagnet 3 Accelerating Cavity 4 High Frequency Amplifier 5 Amplitude Modulator 6 Oscillator 7a Current Reference Value Memory 7b Frequency Reference Value Memory 7c Acceleration Voltage Reference Value Memory 7d Bias Current Reference Value Memory 8 Calculator 9 Bias Power Supply 10 Electromagnet Power Supply 11 Reference electromagnet 12 Magnetic field measuring instrument 13 Magnetic field clock generator 14 Time clock generator

Claims (3)

[Claims] 1. In a charged particle accelerator of variable acceleration frequency, an electromagnet power supply for supplying a current to a deflection electromagnet that bends a beam of charged particles, and a current reference value for generating a current reference value of a current output from the electromagnet power supply. A memory, an oscillator for outputting an acceleration voltage to an acceleration cavity for accelerating the beam of the charged particles, and an acceleration frequency pattern of the acceleration voltage corresponding to a pattern of a current reference value generated from the current reference value memory. A calculator for calculating, a frequency reference value memory for generating a frequency reference value of the accelerating voltage according to an acceleration frequency pattern of the accelerating voltage calculated by the computer, the same operation clock for the current reference value memory and the frequency reference value memory And a time clock generator for supplying the charged particle accelerator. 2. An amplitude control circuit for controlling the amplitude of the acceleration voltage from the oscillator, and an acceleration voltage reference memory for outputting an acceleration voltage reference value to the amplitude control circuit are additionally provided, and the time clock generator is provided. The charged particle accelerator according to claim 1, wherein the same operation clock is supplied to the acceleration voltage reference memory. 3. A bias power supply for tuning the acceleration cavity and a bias current reference value memory for controlling the bias power supply are additionally provided, and the time clock generator is also provided in the bias current reference value memory. The charged particle accelerator according to claim 1, wherein the same operation clock is supplied.