JPH07114160B2 - Tune measurement device for particle accelerator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Industrial field of application) The present invention relates to a beam monitor device of a particle accelerator for accelerating particles such as electrons, and the betatron frequency of a particle beam passing through a vacuum duct. The present invention relates to a tune measuring device of a particle accelerator for measuring.

(Prior Art) FIG. 2 shows an example of a particle accelerator. In the figure, 1 is a linear accelerator which outputs particles having a predetermined kinetic energy, for example, an electron beam. The electron beam output here is electrostatically deflected by the electrostatic inflector 2, and is incident tangentially to the electron traveling trajectory in the vacuum duct 15A of the acceleration ring 3. Bending electromagnet 4A in the accelerating ring 3
Are arranged in the shaded area in the figure, and the electron beam incident from the linear accelerator 1 is deflected by this. Therefore, the electron beam is controlled by the magnetic field generated by the bending electromagnet 4A so as to be contained within the predetermined trajectory of the vacuum duct 15A. A high-frequency electric field is preliminarily formed in the high-frequency acceleration cavity 5A, so that the electron beam is given more energy than the kinetic energy lost when it orbits the surroundings (energy lost as an electromagnetic wave) and is gradually accelerated. . Further, by excessively decelerating the electron beam by the electric field generated in the high frequency accelerating cavity, a particle group called a bunch, which is divided into some in the traveling direction of the electron beam, is generated on the orbit. This number of electron particle groups is called the harmonic number. Then, the electron beam that has reached a predetermined kinetic energy is removed from the orbit in the acceleration ring 3 by the magnetic field generated by the kicker electromagnet 6 and the deflector electromagnet 7, and is taken out into the particle transport tube 8. The electron beam extracted here reaches the storage ring 9 and enters a circular orbit in the vacuum duct 15B of the storage ring 9 by the magnetic fields generated by the inflector electromagnet 10 and the perturbator electromagnet 11 inside. At this time,
In the storage ring 9, as in the case of the acceleration ring 3 described above, a plurality of deflection electromagnets 4S are properly arranged, and a magnetic field equivalent to the kinetic energy of the incident electron beam is generated in advance. The electron beam is controlled by this magnetic field so as to be within a predetermined orbit. The high frequency accelerating cavity 5S in the storage ring 9 is an electron beam accelerating device similar to 5A, and is controlled by the electric field generated in the high frequency accelerating cavity 5S so as to keep the electron beam at a constant kinetic energy. This compensates for the attenuation of the kinetic energy of the electron beam due to the synchrotron radiation phenomenon.

In addition, a beam line is formed on the bending electromagnet 4S in the storage ring 9.
A port called 12 is provided so that synchrotron radiation generated when an electron beam having a predetermined kinetic energy is deflected is guided to the measurement port 13. This emitted light is extreme ultraviolet continuous light, and after being spectrally processed by the optical system of the measurement port 13, it is used as a light source or the like of the semiconductor control device. The accelerating ring 3, the storage ring 9, the particle transport tube 8 and the like shown in FIG.
In addition to S and 4T, a quadrupole magnet, a hexapole magnet, and the like are installed, and a plurality of beam lines 12 are also provided, but they are omitted here for convenience of explanation.

Next, a tune measuring device for measuring the betatron frequency of an electron beam operating in the above-mentioned vacuum duct will be described with reference to the conventional configuration diagram of FIG.

The tracking generator 16 continuously inputs a constant voltage (constant power) sine wave signal having frequencies f ₀ to f ₁ to the power amplifier 17 (high frequency amplifier) to amplify the voltage (power). The amplified signal is divided and converted into in-phase (0 °) or anti-phase (180 °) signals by the power dividers 18A to 18C. The phase selection of the power dividers 18A to 18C is set as shown in the figure, and is output to the RF knockout electrodes 20A to 20D on the cross section of the vacuum duct 15 through the respective switches SW5 to 8 in the horizontal and vertical switching circuit 19A below. A disturbance magnetic field is applied to the electron beam A from the RF knockout electrodes 20A to 20D.

The accelerated electrons that have received the disturbance magnetic field are displaced horizontally or vertically with respect to the parallel orbit in accordance with the switching of the horizontal / vertical switching circuit 19A. This displaced position signal is detected by the pickup monitor electrodes 21A to 21D on the cross section of the vacuum duct, and passes through the switches SW1 to 4 in the horizontal / vertical switching circuit 19B to the phase calculation circuit 22.
To enter.

The phase calculation circuit 22 calculates the amount of displacement in the horizontal and vertical directions (COD: deviation in the horizontal and vertical directions from the equilibrium orbit) and outputs it to the spectrum analyzer 23.

The spectrum analyzer 23, to which the horizontal and vertical displacements have been input, is swept in the frequency range of the disturbance magnetic field applied from the tracking generator 16 side, and the resonance frequency of the accelerated electron beam is analyzed and displayed. That is, when the frequency of the tracking generator 16 is changed, the frequency of the disturbance magnetic field changes. When this frequency matches the betatron frequency of the accelerated electron beam, the electron beam resonates and is largely displaced in the horizontal and vertical directions. This state is detected by the pickup monitor electrodes 21A to 21D, and the output of the tracking generator 16 at that time is read to know the resonance frequency of the accelerated electron beam. This resonant frequency is the betatron frequency or tune of the electron beam.

Next, the processing of the horizontal and vertical displacement amounts in the tune measuring device will be described in more detail.

As described with reference to FIG. 2, the vacuum duct 15 is a duct containing a balanced orbit of the electron beam and is maintained in a high vacuum. Then, the pickup monitor electrode 21 shown in FIG.
A to D are mounted in this vacuum duct, and detect the passing position of the beam on the duct cross section.

Further, the RF knockout electrodes 20A to 20D apply a disturbance magnetic field to the electron beam. The electron beam that has received this disturbance magnetic field is naturally displaced with respect to the equilibrium orbit. As described above, the displacement amount becomes maximum when the frequency of the constant strength disturbance magnetic field coincides with the betatron frequency of the electron beam, that is, the tune. That is, the frequency at which the maximum displacement amount is shown on the pickup monitor electrode side measuring the displacement amount of the electron beam using the spectrum analyzer is the tune of the electron beam.

(Problems to be Solved by the Invention) The conventional tune measuring apparatus for a particle accelerator described above inputs the output signal from the tracking generator 16 to the power amplifier 17 as shown in FIG. 3 to amplify the voltage (power). There is. Therefore, the circuits of the power amplifier 17 and above are all high level power circuits. On the other hand, in recent years, particle acceleration is designed to obtain kinetic energy of several GeV to several tens of GeV due to a demand for larger size, and is partly operated. In order to measure the tune of such high-energy particles, unless the disturbance magnetic field applied to the RF knockout electrodes 20A to 20D is made stronger, the accelerating particles will not be sufficiently displaced, and the pickup monitor electrodes 21A to 21D will not be displaced. A sufficient voltage difference does not appear and tune measurement becomes difficult. Therefore, power up of FR knockout circuit is required for tune measurement of high energy particles of GeV class or higher. However, the conventional configuration shown in FIG. 3 does not reasonably satisfy the power-up requirement. The reason is as follows.

(1) Since there is only one power amplifier 17, a high gain power amplifier is required to obtain a high output, which is more difficult economically and technically.

(2) Since the circuits after the power amplifier 17 are all high-level power circuits, it is necessary to upgrade the ratings of the power dividers 18A to 18C and the changeover switches SW5 to 8 in the horizontal / vertical changeover circuit 19A. It will be more difficult.

Therefore, an object of the present invention is to provide a highly accurate, rational, and economical tune measuring device for a particle accelerator without increasing the ratings of a divider and a horizontal / vertical switching circuit.

[Structure of the Invention] (Means for Solving the Problem) The present invention provides a tracking generator that continuously outputs a low-level sine wave with a frequency of f ₀ to f ₁ of, for example, about 0 dBm = 1 mW, and an output signal of the tracking generator. A divider circuit that divides every predetermined phase, a horizontal or vertical selection switch circuit for connecting each signal output from this divider circuit to a predetermined RF knockout electrode, and a phase between each signal output from each switch circuit And a phase and amplitude adjusting device such as a phase shifter and a variable attenuator for adjusting the amplitude, and applying this output signal to the RF knockout electrode through a power amplifier that amplifies to a high level to generate a disturbance magnetic field Is.

(Working) In the conventional method, even if a power amplifier 17 with a maximum output of 40 W is used, the output end of the divider is 10 W each,
Only this power can be supplied to the RF knockout electrode.

On the other hand, according to the present invention having the above configuration, the maximum output is 40
If you use a W power amplifier, you can directly supply this 40W power to the RF knockout electrode.

The tracking generator and the attenuator are low level circuits. Therefore, irrespective of the increase in output, the circuits such as the divider, the switch circuit, the phase shifter, and the attenuator can use low rated products, which is economical.

By the way, since four power amplifiers are individually used, a characteristic difference between the amplifiers causes a phase difference and an amplitude difference between the signals applied to the RF knockout electrodes. To solve this problem, the RF knockout electrode applied signal is measured in advance, the phase is corrected using a phase shifter, and the amplitude is corrected using, for example, an attenuator. This makes it possible to correct the characteristic variations of the power amplifier, resulting in a highly accurate RF knockout circuit.

(Embodiment) FIG. 1 is a configuration diagram of a tune measuring apparatus for a particle accelerator showing an embodiment of the present invention, and the same reference numerals in FIG.

The structure of FIG. 1 differs from that of FIG. 3 in that the power amplifiers 17A to 17D are arranged in front of each electrode in order to increase the power of the RF knockout electrodes 20A to D, and the characteristics of each power amplifier vary. In order to correct the phase difference and amplitude difference, the phase shifter 24A is placed in front of each power amplifier.
.About.D and variable attenuators 25A to 25D are provided.

In the figure, the tracking generator 16 continuously outputs a constant power sine wave signal having a frequency f _{0 to} f _{1 of} about 0 dBm = 1 mW to the divider 18X. The divider 18X divides the input signal in phase with half the power of the input signal.
Output to 8Y and 18Z. The divider 18Y outputs half the power of the input signal in opposite phase to the input signal. Divider 18Z is 18
It has the same function as X. Therefore, the signals output from the divider circuits 18X to 18Z have a power of 1/4 and a phase opposite to that of the output signal of the tracking generator 16 for the 18Y output signal and the same phase for the 18Z output signal. .

The horizontal or vertical selection switch circuit 19X is, as shown in the drawing, the phase of the signal applied to the RF knockout electrodes 20A to 20D by switching the connection destinations of the signals input from the divider circuits 18Y and 18Z and having different phase relationships. To switch. Thereby, the application direction of the disturbance magnetic field to the beam can be selected to be horizontal or vertical. Each signal output from the switch circuit 19X is a phase shifter 24A
Input to ~ D. The phase shifters 24A to 24D are delay circuits having a function of delaying the phase of the input signal without changing the frequency, and are configured to be continuously variable. The signals output by the phase shifters 24A-D are input to the variable attenuators 25A-D. The variable attenuators 25A to 25D are attenuators and can attenuate only the amplitude of the output signal with respect to the input signal. Attenuator
The signal output from 25 is input to the power amplifiers 17A to 17D, where it is amplified to a high level signal and applied to the RF knockout electrodes 20A to 20D to generate a high magnetic field. The power amplifiers 17A to 17D are 16W up to 40W for 0.25mW input.
Use an amplifier that can amplify by 000 times. Others are the same as the conventional configuration shown in FIG.

In the above configuration, since the power amplifiers 17A to 17D are high-output, high-gain amplifiers, it is extremely difficult to make the phases significantly different from the input signal and to make the gain balance the same. Therefore, variations in characteristics between the amplifiers A to D cause variations in phase and amplitude between input signals and output signals. Further, it is difficult to make the cable lengths from the tracking generator 16 between the RF knockout electrodes 20A to 20D equal to each other in actual wiring. Therefore, due to the mutual variation of this cable length,
The phase and amplitude between the signals of the RF-knockout electrodes 20A to 20D are mutually different. However, the input signal of each of these electrodes is a reproducible signal that rarely changes with time and from measurement to measurement.

Therefore, after the wiring of the entire measurement system is completed, the RF knockout electrode
Connect a spectrum analyzer to 20A-D and measure the amplitude and phase of the signal between each electrode in advance. As a result, for example, it is assumed that the electrode signals of 20B and 20C have the same phase and amplitude with respect to the 20A electrode, and the signal of the 20D electrode is advanced by 3 ° in phase and 3 dB higher in amplitude. R in this state
Signals between the RF knockout electrodes 20A to D are adjusted by adjusting the phase shifter 24D to delay by 3 ° and adjusting the variable attenuator 25D to -3dB in order to match the phase and amplitude of the signal between the F knockout electrodes. The phase and amplitude of can be matched.

In the above embodiment, four circuits are provided for the phase shifter so that they can be adjusted by mutual adjustment, but the amplitude cannot be amplified because it is an attenuator. Therefore, it is necessary to select the electrode having the lowest amplitude among the four as the reference electrode.
Therefore, if a low-level variable amplifier is used instead of this variable attenuator, the highest electrode in the variable gain range of this amplifier can be selected as a reference.

In addition, phase shifters 24A-D and variable attenuators 25A-
The positions of D may be interchanged, and these may be any phase and amplitude adjusting device that can freely change the phase and amplitude independently of each other.

[Effects of the Invention] As described above, according to the present invention, four power amplifiers corresponding to each RF knockout electrode and a divider and a changeover switch are provided on the low-level circuit side connected to the power amplifiers and each circuit is provided. Since the phase and amplitude adjusting device that corrects the phase and amplitude differences generated mutually is inserted,
A highly accurate, reasonable, and economical particle accelerator tune measuring device can be obtained.

[Brief description of drawings]

FIG. 1 is a partial configuration diagram of a tune measuring device showing an embodiment of the present invention, FIG. 2 is a conceptual overall configuration diagram of a particle accelerator, and FIG. 3 is a configuration diagram of a conventional tune measuring device. 17 ... Power amplifier, 18A-C, 18X-Y ... Power divider, 19A, 19B, 19X ... Horizontal / vertical switching circuit, 20A-D ... RF
Knockout electrode, 24A-D ... Phase shifter, 25A-D
...... Variable attenuator.

Claims (1)

[Claims] 1. A tracking generator for continuously sweeping and outputting a sine wave signal in a predetermined frequency range, a divider circuit for dividing and outputting a signal output from the tracking generator for each predetermined phase, and an output from the divider circuit. In the tune measuring device of the particle accelerator equipped with a horizontal / vertical selection switch circuit for supplying each signal to a predetermined RF knockout electrode, the phase and amplitude of each signal output from the horizontal / vertical selection switch circuit is adjusted. For each phase shifter and each attenuator, and each power amplifier that amplifies each signal output from each phase shifter and each attenuator to a high level.The output of each power amplifier is applied to the RF knockout electrode. A tune measuring device for a particle accelerator, characterized by: