JP2968020B2 - High frequency power supply for high frequency accelerating cavity - Google Patents

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial application field) The present invention relates to a high-frequency power supply for a high-frequency accelerating cavity used in, for example, an X-ray generator.

(Prior Art) Strong X-rays having a wide frequency spectrum
It can be obtained with an X-ray generator having a configuration as shown in the figure.
That is, the electrons generated at the cathode 1 are accelerated to near the speed of light by the linear accelerator 2 and the ring accelerator 3, and the high-speed electrons are taken out by the magnet 4 to obtain X-rays A.

The high-frequency energy required to accelerate the electrons in the ring accelerator 3 is supplied from the high-frequency power supply 5 to the ring accelerator 3.
Is supplied into the acceleration cavity 3a provided in a part of the.

FIG. 4 is a circuit configuration diagram of a conventional high-frequency power supply device 5 for a high-frequency acceleration cavity.

That is, the high-frequency signal from the high-frequency signal source 51 is set to a desired voltage amplitude via a voltage variable circuit 52 including a variable resistor or the like, and then supplied to a variable phase shifter 53 to be adjusted in phase.
The high-frequency signal after the phase adjustment is amplified by the power amplifier circuit 54 including the cascade amplification stages of the intermediate power amplifier 541 and the power amplifier 542, and is supplied from the output terminal 543 into the high-frequency acceleration cavity 3a.

The condition required for the electrical characteristics in the accelerating cavity 3a is that the high-frequency power in the cavity always matches the high-speed electrons. It is configured to supply a level of power.

That is, the high-frequency signal level serving as a reference for satisfying the matching condition in the high-frequency accelerating cavity 3a is set in the amplitude level setter 55 in advance, and the signal from the amplitude level setter 55 and the power amplitude The output signal from the directional coupler 54a is supplied to a comparison controller 56, and the variable voltage circuit 52 is controlled by a signal corresponding to the difference between the amplitude levels of the two signals so that the difference is always zero. Control.

Therefore, when a mismatch condition occurs in the acceleration cavity 3a,
The reflected power is generated on the high-frequency power supply device 5 side, and the amplitude level of the output power is reduced.
The variable voltage circuit 52 is controlled so as to compensate for the decrease due to the reflected power by the difference generated by comparing the reference amplitude level with the reference amplitude level, thereby controlling the output signal amplitude at high speed.

Further, in order to efficiently accelerate the electrons in the acceleration cavity 3a by controlling the variable voltage circuit 52, it is required that the phase characteristic of the supplied power, that is, the AM-PM characteristic is always constant. However, as the output power of the power amplifier 54 changes,
Since the AM-PM characteristics change, the signal from the high-frequency signal source 51 and the signal extracted from the power amplifier circuit 54 via the directional coupler 54b are supplied to the phase control circuit 57, and the phase difference is always zero or zero. The configuration was such that the variable phase shifter 35 was controlled to be constant.

However, the conventional power supply device 5 as described above has two completely independent control systems, an amplitude control system and a phase control system, and uses an analog signal as a control signal. There is a drawback that high-speed followability of control and stability of phase control cannot be obtained.

(Problems to be Solved by the Invention) As described above, the conventional power supply device has two independent control systems in the control system, and both of them are based on analog control. Could not be obtained.

The present invention uses a simple configuration and a digitized one.
An object of the present invention is to provide a high-frequency power supply for a high-frequency accelerating cavity, which solves the above-mentioned conventional disadvantages by realizing two control systems.

[Structure of the Invention] (Means for Solving the Problems) A high-frequency accelerating cavity power supply device according to the present invention includes a high-frequency signal source, a variable voltage circuit connected to the high-frequency signal source, and a variable voltage circuit connected to the variable voltage circuit. A variable phase shifter, a power amplifying circuit connected to the variable phase shifter and supplying an amplified high-frequency signal to a high-frequency accelerating cavity, and an analog / digital converter for introducing a part of an output signal of the power amplifying circuit and converting it into a digital signal. A digital converter, an amplitude level setting device for setting a high frequency signal amplitude level required in the high frequency acceleration cavity by a digital signal, and a signal from the amplitude level setting device and a signal from the analog / digital converter are introduced. A comparison controller for comparing and supplying a control signal to the variable voltage circuit; and a phase controller connected to the comparison controller for supplying a phase control signal to the variable phase shifter. Characterized by comprising a circuit.

(Operation) According to the above configuration, since both the control to the variable voltage circuit and the control to the variable phase shifter are performed by the digitized control signal by one comparison controller, the high speed required for the power supply device is obtained. Followability and stabilization are obtained.

(Embodiment) Hereinafter, an embodiment of a power supply device for a high-frequency accelerating cavity according to the present invention will be described in detail with reference to FIG. 1 and FIG.
The same components as those of the conventional configuration shown in FIGS. 3 and 4 are denoted by the same reference numerals, and detailed description is omitted.

That is, a variable phase shifter 53 is connected to the high-frequency signal source 51 via a variable voltage circuit 52 for controlling the amplitude. Variable phase shifter
The output of 53 is supplied from the output terminal 543 to the acceleration cavity 3a via the power amplifier 54 composed of the intermediate power amplifier 541 and the power amplifier 542.

A part of the output of the power amplification circuit 54 is supplied to an analog / digital (A / D) converter 58 via a directional coupler 54a, and the analog signal is converted into a digital signal.

On the other hand, the digitized voltage reference level corresponding to the high-frequency signal amplitude level required for matching in the high-frequency acceleration cavity 3a is set in the amplitude level setter 55 'in advance,
The signal from the amplitude level setting unit 55 'and the A / D converter 5
The signal from 8 is supplied to a comparison controller 56 'and compared.

Therefore, the output of the comparison controller 56 'digitally controls the variable voltage circuit 52 so that the output of the power amplifier circuit 54 satisfies the matching condition in the high-speed cavity 3a.

Incidentally, even if the input / output characteristics of the power amplifier circuit 54 show a linear amplification characteristic as shown in FIG. 2A, the phase characteristics of the power amplifier 54 become non-linear as shown in FIG. 2B. Therefore, in order to realize a good matching state in the acceleration cavity 4a, phase compensation is performed with phase characteristics as shown in FIG. 2 (c) so that the phase characteristics, that is, the AM-PM characteristics are always constant. There is a need. Since the phase characteristics as shown in FIG. 2C correspond to the output level of the power amplifier circuit 54, the variable phase shifter 53 is digitally controlled according to the control of the variable voltage circuit 52.

Therefore, the phase control circuit 59 is composed of a ROM (read only memory) 591 and a phase controller 592, and the comparison controller 5
Information (data) on the amount of phase compensation according to the output level of 6 '
Is stored in the conversion table of the ROM 591 in advance, the storage information is read out by the output of the comparison controller 56 ′, and is supplied to the phase controller 592. The phase controller 592 derives a phase control signal based on the stored information from the ROM 591 to control the variable phase shifter 53, so that the phase of the output signal of the power amplifier circuit 54 is always constant, and the phase Function so that optimal acceleration is performed.

Therefore, the high-frequency power supply for the high-frequency accelerating cavity according to the present invention uses a digital signal for the feedback control signal and is formed by only one control system. Phase control can be realized.

[Effects of the Invention] As described above in detail, the present invention can realize high-speed tracking of power amplification and stable phase control by adopting a digital control system, and is most suitable for a high-period accelerating cavity of an X-ray generator. The present invention provides a high-frequency power supply device having a large practical effect.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing one embodiment of a high-frequency power supply device for a high-frequency accelerating cavity according to the present invention, and FIGS. 2 (a) and 2 (b).
(C) is an input / output characteristic diagram, a phase characteristic diagram, and a phase compensation characteristic diagram of the device shown in FIG. 1, respectively. FIG. 3 is a configuration diagram of an X-ray generator to which a high-frequency power supply device for a high-frequency accelerating cavity is applied. FIG. 1 is a circuit diagram showing a conventional high-frequency power supply for a high-frequency acceleration cavity. DESCRIPTION OF SYMBOLS 1 ... Cathode, 2 ... Linear accelerator, 3 ... Ring accelerator, 4 ... Magnet, 5 ... High frequency power supply, 51 ... High frequency signal source, 52 ... Variable voltage circuit, 53 ... Variable phase 54, a power amplifier circuit, 55, 55 ', an amplitude level setting device, 56, 56', a comparison controller, 57, 59, a phase comparison controller, 58, an analog-digital converter.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H05H 7/02 H03L 5/00 H03L 7/00

Claims (1)

(57) [Claims] A high-frequency signal source, a variable voltage circuit connected to the high-frequency signal source, a variable phase shifter connected to the variable voltage circuit, and an amplified high-frequency signal connected to the variable phase shifter. A power amplifier circuit for supplying the acceleration cavity;
An analog / digital converter that introduces a part of the output signal of the power amplifier circuit and converts it into a digital signal; an amplitude level setter that sets a high frequency signal amplitude level required in the high frequency acceleration cavity by a digital signal; A comparison controller for introducing and comparing a signal from an amplitude level setter and a signal from the analog / digital converter and supplying a control signal to the variable voltage circuit; and a phase controller connected to the comparison controller and controlling the phase of the variable phase shifter. A high frequency power supply for a high frequency acceleration cavity, comprising: a phase control circuit for supplying a control signal.