JPH06176893A - Phase stabilized transmission device - Google Patents

Abstract

PURPOSE:To make identical the electric lengths in the acceleration signal transmitting part and acceleration signal receiving part and make possible acceleration of an electron beam stably by performing the bidirectional transmission using one optical fiber cable in lieu of two coaxial cables as conventional. CONSTITUTION:A high frequency acceleration signal for transmission (e) and a one for reception (g) are converted into optical signals by E/O converters 31, 36, and the resultant are subjected to bidirectional optical coupling by photo- branch couplers 32, 34 and transmitted through one optical fiber cable 33a. This is bidirectionally branched by the couplers 34, 32 and converted into electric signals by O/E converters 35, 37. This ensures that the electric lengths on the transmission side and on the reception side are identical and that no difference in the phase variation amount is produced originating from the temps. on the transmission side and reception side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a particle accelerator for accelerating particles such as an electron beam and a phase stabilizing transmission device for transmitting a high frequency acceleration signal to a high frequency acceleration cavity.

[0002]

2. Description of the Related Art FIG. 2 shows an example of a particle acceleration accumulator. 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 4 of the acceleration storage ring 3. A plurality of deflection electromagnets 5 are arranged in the acceleration storage ring 3 in the shaded area in the figure, and this deflects the electron beam incident from the linear accelerator 1. Therefore, the electron beam is controlled by the magnetic field generated by the deflecting electromagnet 5 so as to be contained in the predetermined trajectory of the vacuum duct 4. A high-frequency electric field is pre-formed in the high-frequency acceleration cavity 6, which gives the electron beam more energy than the kinetic energy lost when it orbits the orbit (energy lost as an electromagnetic wave) and is gradually accelerated. It In addition, by accelerating and decelerating the electron beam by the electric field generated in the high-frequency acceleration 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 controlled to be kept at a constant kinetic energy by the electric field generated in the high-frequency acceleration cavity 6. This compensates for the attenuation of the kinetic energy of the electron beam due to the synchrotron radiation phenomenon.

Further, a port called a beam line 7 is provided in the deflection electromagnet 5 in the acceleration storage ring 3.
The synchrotron radiation generated when an electron beam having a predetermined kinetic energy is deflected is arranged to be guided to the measurement port 8. This radiated light is extreme ultraviolet continuous light, and after being spectrally processed by the optical system of the measurement port 8, it is used as a light source or the like of the semiconductor control device. The deflection electromagnet 5 is attached to the acceleration storage ring 3, the particle transport tube 9 and the like shown in FIG.
Besides, a quadrupole magnet, a hexapole magnet, etc. are installed, and a plurality of beam lines 7 are also provided, but they are omitted here for the sake of simplicity of description.

In the particle accelerator described above, when a plurality of high-frequency accelerating cavities are installed in the particle accelerating accumulator due to the recent demand for a larger size, the particle accelerator is designed to obtain kinetic energy of several Gev to several tens Gev. There is. In such a case, if the kinetic energy given by each high-frequency accelerating cavity is the same and the increase in the kinetic energy and the increase in the magnetic field in the deflection electromagnet are not in a predetermined proportional relationship, the electron beam will stably orbit. It becomes impossible to orbit, that is, to accelerate. Therefore, it is necessary to match the phases of the high-frequency electric fields generated in a plurality of high-frequency accelerating cavities with the electron beam, and the standard high-frequency signal output from one oscillator is usually distributed and transmitted to each high-frequency accelerating cavity. ing. However, in the case of a large particle accelerator, the reference acceleration frequency is several hundred MHZ, and the orbit of the particle accelerator is also several hundred meters to several km, so the signal between the oscillator that generates the reference high frequency signal and each high frequency acceleration cavity is large. It is difficult to make the transmission distance the same. Therefore, the phase-stabilized transmission device shown in FIG. 3 is configured to match the high-frequency signal phase in each high-frequency acceleration cavity.

FIG. 3 is a system configuration diagram of a conventional phase-stabilized transmission device. In the figure, the reference high frequency signal a generated by the high frequency signal generator 11 is input to the power divider 12 and distributed to the high frequency acceleration signals b _{1 to} b _m to be transmitted to the respective high frequency acceleration cavities. Since the distributed high-frequency acceleration signals b _{1 to} b _m go through exactly the same circuit, only b ₁ is shown here and the others are omitted for the sake of simplicity. The high frequency acceleration signal b ₁ is distributed by the power divider 14 through the amplifier 13, one of which is input as the transmission side high frequency acceleration signal c and the other is input as the transmission side phase difference detection signal d to the phase difference detector 27. The transmission-side high-frequency acceleration signal c passes through the phase adjuster 15 and the amplifier 16 and is output from the acceleration-signal transmitting unit 17a as a transmission high-frequency acceleration signal e. Acceleration signal transmitter
The transmission high-frequency acceleration signal e that outputs 17a is transmitted to the acceleration signal receiving unit 19 via the coaxial cable 18a whose temperature is controlled by cooling water.
It is input to a and then to the power divider 21 via the amplifier 20. Then, it is distributed by the power divider 21, one is output as each high-frequency acceleration signal f ₁ to each high-frequency acceleration cavity via the amplifier 22, and the other is output as the return high-frequency acceleration signal g via the amplifier 23 from the acceleration signal receiving unit 19a. Is output.

The return high-frequency acceleration signal g output from the acceleration signal receiving section 19a is re-input to the acceleration signal receiving section 17a via the coaxial cable 24a whose temperature is controlled by cooling water as in the transmitting side. After that, it passes through the amplifier 25 and the phase adjuster 26, and is input to the phase difference detector 27 as the reception side phase difference detection signal h. The phase difference detector 27 detects the phase difference between the transmission side phase difference detection signal d and the reception side phase difference detection signal h as a voltage signal, and inputs it to the phase adjusters 15 and 26 via the signal halve unit 28. Then, in the phase adjusters 15 and 26, the phase difference detector 27
The phase of the high-frequency acceleration signal b ₁ and the phase of each high-frequency acceleration signal f ₁ output to each high-frequency acceleration cavity are matched by shifting half of the phase difference detected in ₁ . Therefore, the acceleration signal transmitters 17a to 17n and the acceleration signal receivers are provided for each high-frequency acceleration cavity.
19a to 19n and coaxial cables 18a to 18m connecting both
By preparing the 24a 24n, it was configured to match the phase of each rf signal f ₁ ~f _n to be outputted to the high-frequency acceleration signal b ₁ ~b _n and the radio frequency accelerating cavity of the respective circuits.

[0007]

However, in the case of a large particle accelerator, as described above, the orbit becomes several hundred meters to several kilometers. Therefore, the distance between the acceleration signal transmitter and the acceleration signal receiver is the same. That is, it shows that the coaxial cable connecting the acceleration signal transmission unit and the acceleration signal reception unit is about several hundred meters, and the length of the two transmission and reply coaxial cables, which is several hundred meters, is the electrical length. Must match as. However, if the frequency of the high-frequency acceleration signal is 500 M
If the wavelength reduction rate of HZ and coaxial cable is 66%, the wavelength λ of the high frequency acceleration signal is And the length between the transmitting and receiving coaxial cables is 1.1 m.
When m is different, the phase is different by 1 deg. It is difficult to make the length between two coaxial cables of several hundred meters the same length in mm, that is, a phase difference larger than the original phase difference is detected between the transmitting side and the returning side. , Each high frequency acceleration signal f ₁ output to each high frequency acceleration cavity
.About.f _n and the high frequency acceleration signals b _{1 to} b _n cannot be in phase.

Further, the temperature of the coaxial cable on the transmitting side and that on the returning side are controlled by cooling water, but the temperature is controlled to the same temperature for several hundreds of meters, and there is no temperature difference between the two coaxial cables. It is difficult to control. If the frequency of the high-frequency acceleration signal is 500 MHZ, the wavelength shortening rate of the coaxial cable is 66%, the linear expansion coefficient of copper is 16.7 × 10 ^-6 / ° C, and the length of the coaxial cable is 500 m, the wavelength of the high-frequency acceleration signal is as described above. As described above, the phase fluctuation amount Δθ caused by the temperature difference of 1 ° C. is 0.396 m. Becomes Therefore, in the conventional configuration, it is difficult to make the electric lengths of the two long coaxial cables that connect the acceleration signal transmitters and the acceleration signal receivers the same. The present invention has been made to solve the above problems, and an object thereof is to provide a phase-stabilized transmission device in which the electrical lengths of the transmitting side and the returning side are the same.

[0009]

According to the present invention, the two coaxial cables used in the conventional phase-stabilized transmission apparatus are replaced by one optical fiber cable, and the acceleration signal transmitting section and the acceleration signal receiving section receive an electric signal / electric signal. An optical signal converter (hereinafter referred to as an E / O converter) and an optical signal / electrical signal converter (hereinafter referred to as an O / E converter) are prepared, and the optical signal is branched and coupled to the acceleration signal transmitter and the acceleration signal receiver. By preparing a container, the signal on the transmitting side and the signal on the returning side are transmitted by the above-mentioned one optical fiber cable.

In the phase-stabilized transmission device, in order to make the electric lengths of the transmitting side and the returning side the same and to prevent the phase fluctuation due to the temperature difference, the phase difference between the acceleration signal transmitting section and the acceleration signal receiving section is set. It is possible if only one connection cable is used. However, as an electric signal, it is difficult to perform transmission on both the transmitting side and the returning side on a single cable because it requires coupling and separation of bidirectional signals. However, as long as it is an optical signal, it is possible to transmit both the transmitting side signal and the returning side signal with a single optical fiber cable, so it is not necessary to match the lengths of the two optical fibers. Moreover, both an E / O converter using a laser diode and an O / E converter using a PIN photodiode are technically established for E / O conversion of a high frequency signal of about several hundred MHZ. Has been done. An optical branching / coupling device for transmitting and receiving two optical signals to one optical fiber cable is also technically established. Regarding the amount of phase fluctuation due to temperature conversion of the optical fiber cable, the frequency of the high frequency acceleration signal is 500 MHZ, the optical fiber cable length is 500 m, the refractive index of the silica glass of the optical fiber cable is 1.48, and the linear expansion coefficient is Assuming 0.4 × 10 ^-6 , the wavelength λ is Since it is much more stable than a coaxial cable, it is economical without the need for temperature control by cooling water.
Moreover, since both the transmitting side and the returning side are transmitted by the same optical fiber cable, even if there is a temperature difference on the laying of the optical fiber cable, the transmitting side and the returning side will have the same phase fluctuation amount, so each high frequency acceleration It is possible to obtain a phase-stabilized transmission device in which the phase difference between signals is always kept in the same phase.

[0010]

Embodiments will be described below with reference to the drawings. Figure 1
FIG. 3 is a configuration diagram of an embodiment of a phase-stabilized transmission device according to the present invention. In FIG. 1, the same reference numerals as those in FIG. 3 denote the same or corresponding parts. The configuration of FIG. 1 is different from that of FIG. 3 in that the transmission high-frequency acceleration signal e in the acceleration signal transmission unit 17a is the E / O converter.
The point is that the signal is transmitted to the acceleration signal receiving section 19a via the optical fiber cable 33a via 31 and the optical branching / coupling device 32, and is input to the amplifier 20 via the optical branching / coupling device 34 and the O / E converter 35. Then, the return high-frequency acceleration signal g from the acceleration signal receiving section 19a is transmitted to the acceleration signal transmitting section 17a via the optical fiber cable 33a via the E / O converter 36 and the optical branching / coupling unit 34, and the optical branching / coupling is performed. The point is that the signal is input to the amplifier 25 via the converter 32 and the O / E converter 37.

In the above-mentioned structure, the transmission high-frequency acceleration signal e is converted from an electric signal into an optical signal in the E / O converter 31, is further optically coupled in the optical branching / coupling device 32, and is output from the acceleration signal transmitting unit 17a. Then, it is transmitted through the optical fiber cable 33a and input to the acceleration signal receiving section 19a. In the acceleration signal receiving unit 19a, the light is branched by the optical branching / coupling device 34, converted into an electric signal by the O / E converter 35, and input to the amplifier 20. On the other hand, the reply high-frequency acceleration signal g is converted into an optical signal by the E / O converter 36. Further, the signal g is optically combined with the transmitting side signal by the optical branching / coupling device 34 and output from the acceleration signal receiving section 19a. This signal is transmitted from the optical fiber cable 33a to the optical branching / coupling device 32 and branched as a return signal. This optical signal is converted into an electric signal by the O / E converter 37 and then input to the amplifier 25.

That is, the transmission high-frequency acceleration signal e and the return high-frequency acceleration signal g are converted into optical signals by the E / O converters 31 and 36, respectively, and both are optically coupled by the optical branching / coupling devices 32 and 34. After that, it is transmitted by one optical fiber cable 33a. Then, after both are branched by the optical branching and coupling devices 34 and 32, O /
The E converters 35 and 37 convert the electric signals. Therefore, since it is possible to transmit both signals on the transmitting side and the returning side with one optical fiber cable, the electrical lengths on the transmitting side and the returning side are the same, and the amount of phase fluctuation due to temperature on the transmitting side and the returning side is the same. The difference can be eliminated. Therefore, for each high-frequency acceleration cavity, the acceleration signal transmitter 17
By preparing a to 17n, optical fiber cables 33a to 33n, and acceleration signal receiving sections 19a to 19n, the electrical lengths of the transmitting side and the replying side are made the same, and the phase difference fluctuation amount due to temperature is transmitted to the sending side and the replying side. The phase-stabilized transmission device has no difference between the two.

[0013]

As described above, according to the present invention, by transmitting each signal on the transmitting side and the returning side by one optical fiber cable, the electric lengths on the transmitting side and the returning side are made the same. Thus, it is possible to obtain a phase-stabilized transmission device in which there is no difference in the amount of phase fluctuation due to temperature on both the transmitting side and the returning side. Therefore, by preparing this circuit for a plurality of high-frequency accelerating cavities, the phases of the high-frequency electric fields generated in the respective high-frequency accelerating cavities can be matched, and the electron beam can be stably accelerated.

[Brief description of drawings]

FIG. 1 is a system configuration diagram showing a phase-stabilized transmission device showing an embodiment of the present invention.

FIG. 2 is a configuration diagram showing a configuration of a particle acceleration accumulator.

FIG. 3 is a system configuration diagram showing a conventional phase-stabilized transmission device.

[Explanation of symbols]

 1 Linear Accelerator 2 Electrostatic Inflector 3 Acceleration Storage Ring 4 Vacuum Duct 5 Deflection Magnet 6 High Frequency Accelerating Cavity 7 Beamline 8 Measurement Port 9 Particle Transport Tube 11 High Frequency Signal Generator 12, 14, 21 Power Divider 13, 16, 20 , 22, 23, 25 Amplifier 15, 26 Phase accumulator 17a to 17n Acceleration signal transmitter 18a to 18n, 24a to 24n Coaxial cable 27 Phase difference detector 28 Signal half unit 31, 36 E / O converter 32, 34 Optical Branch coupler 33a to 33n Optical fiber cable 35, 37 O / E converter

Claims (1)

[Claims] 1. A high frequency signal generator, a plurality of high frequency acceleration cavities, a power divider for distributing a high frequency acceleration signal from the high frequency signal generator to the plurality of high frequency acceleration cavities, and a power divider. And an acceleration signal transmitting unit that transmits the signal distributed by the above to the high-frequency acceleration cavity via a coaxial cable, and receives the transmitted signal and outputs it to each high-frequency acceleration cavity, and also to the acceleration signal transmission unit. For the transmission, the acceleration signal receiving unit that returns again via another coaxial cable, and the returned signal is received by the acceleration signal transmitting unit, and the phase difference between the signal distributed by the power divider is detected and used. A phase-stabilized transmission device comprising a circuit for adjusting the phase of a signal to stably transmit the mutual phases of the high-frequency acceleration signals to be distributed to the plurality of high-frequency acceleration cavities. The particle accelerator, instead of the coaxial cable, is a single optical fiber cable, and phase-directional transmission is performed between the acceleration signal transmitting unit and the acceleration signal receiving unit via the single optical fiber cable. Phase stabilized transmission device.