GB1582267A – Radio-frequency electron accelerator
– Google Patents
GB1582267A – Radio-frequency electron accelerator
– Google Patents
Radio-frequency electron accelerator
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Publication number
GB1582267A
GB1582267A
GB2871877A
GB2871877A
GB1582267A
GB 1582267 A
GB1582267 A
GB 1582267A
GB 2871877 A
GB2871877 A
GB 2871877A
GB 2871877 A
GB2871877 A
GB 2871877A
GB 1582267 A
GB1582267 A
GB 1582267A
Authority
GB
United Kingdom
Prior art keywords
resonator
frequency
voltage
radio
accelerating
Prior art date
1977-07-08
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
GB2871877A
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
INST YADERNOI FIZIKI SIBIRSKOG
Original Assignee
INST YADERNOI FIZIKI SIBIRSKOG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
1977-07-08
Filing date
1977-07-08
Publication date
1981-01-07
1977-07-08
Application filed by INST YADERNOI FIZIKI SIBIRSKOG
filed
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INST YADERNOI FIZIKI SIBIRSKOG
1977-07-08
Priority to GB2871877A
priority
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patent/GB1582267A/en
1981-01-07
Publication of GB1582267A
publication
Critical
patent/GB1582267A/en
Status
Expired
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Classifications
H—ELECTRICITY
H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
H05H9/00—Linear accelerators
H—ELECTRICITY
H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
H05H7/00—Details of devices of the types covered by groups H05H9/00, H05H11/00, H05H13/00
H05H7/02—Circuits or systems for supplying or feeding radio-frequency energy
Description
(54) RADIO-FREQUENCY ELECTRON ACCELERATOR
(71) We, INSTITUT YADERNOI FIZIKI SlsslRSKoGo OTDELENIA AKADEMII NAUK
SSSR, of Prospekt Nauki II, Novosibirsk, Union of Soviet Socialist Republics, a Corporation organised and existing under the laws of the
Union of Soviet Socialist Republics, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:
The invention relates to accelerators and more particularly to radio-frequency electron accelerators for use in industry as powerful sources of ionizing radiation.
An object of the invention is to provide a radio-frequency electron accelerator which provides a high average output of electron beams.
Another object of the invention is to provide a radio-frequency accelerator having high electron efficiency.
A further object of the invention is to simplify the construction and process of manufacture of radio-frequency electron accelerators.
According to the invention, there is provided a radio-frequency electron accelerator comprising: an accelerating resonator comprising a ressonant cavity encased in a metal vacuum casing, an electron gun for directing an electron beam along the axis of the cavity, a radiofrequency power source for transmitting radiofrequency energy to the electron beam which power source comprises a self-excited oscillator having a single oscillator tube mounted directly on the resonator, a series connected isolating capacitor and coupling loop provided in the cavity of the resonator directly connecting the anode of the tube to the resonator and forming, together with the tube output capacitance, the anode leadout inductance, and the anode cooling water tank inductance, a first resonant circuit of a two-circuit osillatory system in the anode circuit of the osillator tube tuned to a frequency equal or close to that of a second resonant circuit formed by the accelerating resonator.
In order to suppress high-frequency resosnance discharge and to evacuate ions from the accelerating gap, the accelerating resonator preferably comprises a pair of cup-shaped members partially received in each other with their open ends and electrically insulated from each other by providing a gap therebetween defining a capacitor for closing the path of high-frequency currents, a d-c. voltage being applied to one member.
D-c. voltage is preferably applied to the inner member of the resonator, and the edge of the outer member is electrically coupled to the metal vacuum casing along the entire perimeter.
Where the radio-frequencyelectron accelerator functions in the pulsed mode, the anode of the osicillator tube is preferably connected to an independent d-c. source for auxiliary excitation of the accelerating resonator during intervals between pulses.
The isolating capacitor of the coupling loop may be made in the fonn of a system of plates having vacuum gaps therebetween.
The radio-frequency electron accelerator in accordance with the invention enables high average output of the beam of accelerated electrons. Combination of functions of selfexcited oscillator and electron accelerator circuits permits a considerable improvement of electron efficiency of the accelerator, reduction of its size and simplification of the construction and process of manufacture.
The invention will now be described with reference to specific embodiments thereof illustrated in the accompanying drawings, in which:
Figure 1 shows a wiring diagram of the radio-frequency electron accelerator;
Figure 2 shows a wiring diagram of the same accelerator incorporating a system for suppression of high-frequency resonance discharge and evacuation of ions from the accelerating gap;
Figure 3 shows a wiring diagram of the same accelerator having the edge of the outer member of the resonator electrically coupled to the metal vacuum casing along the entire perimeter;
Figure 4 shows a wiring diagram of the same accelerator having an independent d-c. source connected to the anode;
Figure 5 shows a diagrammatic view of the same accelerator having the isolating capacitor of the coupling loop comprising a system of plates with vacuum gaps therebetween.
As shown in Figure 1, the wiring diagram of the radio-frequency electron accelerator comprises a metal vacuum casing 1 accommodating a resonator 2 having centrally located internal projections on the end faces. Electrons injected by an electron gun 3 provided on one of the resonator projections are accelerated along the axis of revolution of the resonator 2. A source of radio-frequency power for transmitting radio-frequency energy to the electron beam comprises a self-excited oscillator built around a single oscillator tube 4 which is a powerful pulse-type oscillator triode connected in a common grid configuration. The oscillator tube 4 is mounted on the resonator 2. The cavity of the resonator 2 accommodates a coupling loop 5.An isolating capacitor 6 in the coupling loop 5 is provided for separating the d-c. component of the anode voltage of the triode from the high-frequency component. The coupling loop 5 is directly connected to the anode of the oscillator tube 4 and forms in combination with the accelerating resonator 2, a two-circuit oscillation system in the anode circuit of the oscillator tube 4.
The self-excited oscillator uses an internal feedback formed by a capacitor 7 inserted between the cathode and anode of the oscillator tube 4. The grid of the oscillator tube 4 is earthed for high-frequency, via a capacitor 8, and the bias voltage is applied thereto by means of a bias resistor 9 inserted between the grid of the tube 4 and the casing of the oscillator.
Heating of the oscillator tube 4 is effected from a heating voltage supply source 10. Anode voltage is fed from an anode supply source 11 which may include a pulse transformer 12 where the accelerator functions in the pulsed mode. Fine tuning of the feedback amplitude and phase is effected by using a cathode loop 13.
In the embodiment of the radio-frequency electron accelerator shown in Figure 2, the accelerating resonator is made of a pair of cup-shaped members 2a and 2b. In order to close the path of high-frequency currents, the members 2a and 2b are interconnected via a capacitor 14. The capacitor 14 may be made in the form of a large number of ceramic capacitors inserted in parallel between both members 2a and 2b of the resonator, but, in order to improve reliability of the accelerator, the capacitor 14 is preferably formed of the cup-shaped members 2a and 2b which are partially received in each other. Negative voltage from a supply source 16 is applied to one member 2b of the resonator via a choke 15.
In the embodiment of the radio-frequency electron accelerator shown in Figure 3, as differed from the embodiment shown in Figure 2, the edge 17 of the outer member 2a of the resonator is electrically coupled to the metal vacuum casing 1.
The embodiment of the radio-frequency accelerator shown in Figure 4 differs in that it is designed for operation in the pulsed mode.
An additional positive d-c. voltage source is connected to the anode of the osicillator tube 4. The source 18 is connected to the anode via a secondary winding of the pulse transformer 12.
Figure 5 shows a diagrammatic view of the radio-frequency electron accelerator. Supply sources are not shown for convenience.
The toroidal copper accelerating resonator 2 which at the same time is a part of the anode circuit of the self-excited oscillator is made in the form of a pair of cup-shaped members 2a and 2b insulated from each other which are partially received in each other to define a gap 19 therebetween to define the capacitor 14 (Figure 2) for closing the path of high-frequency current of the resonator 2. The resonator 2 is accommodated in the metal vacuum casing 1. A seal 20 of the metal vacuum casing 1 is made of indium. To reduce losses of radio-frequency power which may leak through the gap 19 between the members 2a and 2b of the resonator 2, the edge 17 of the outer member 2a of the resonator 2 is electrically coupled (e.g. by welding) to the vacuum casing 1 along the entire perimeter.Natural frequency of the cavity between the inner member 2b of the resonator 2 and vacuum casing 1 is selected to be sufficiently different from the natural frequency of the accelerating resonator 2. Negative voltage is applied to the inner member 2b of the resonator 2 via the high-frequency choke 15 for suppression of high-frequency resonance discharge and evacuation of ions from accelerating gap 21. The inner member 2b of the resonator which is insulated from the outer member thereof is mounted on three support insulators 22. The oscillator tube 4 is arranged directly on the outer end face of the resonator 2. The anode of the oscillator tube 4 is connected to the resonator 2 by means of an induction coupling loop 5 without using an intermediate feeder. The isolating capacitor 6 comprises a system of plates 23 having vacuum gaps therebetween.
The anode circuit of the oscillator which consists of distributed reactance parameters of the anode having a copper screen 24, anode cooling water tank 25, resistance of the coupling loop 5 and resistance of the resonator in the circuit of the coupling loop 5 represents a two-circuit oscillation system in which one of the frequencies is close to the natural resonance frequency of the high-Q accelerating resonator, and it is this frequency that defines the oscillator frequency.
The oscillator has an internal feedback formed by the additional structural capacitor 7 inserted between the cathod and anode of the tube 4 and comprising a dise placed above the anode of the tube 4 and separated therefrom by an air gap. As shown in Figure 5, the anode of the tube 4 is protected by a screen 24. Fine tuning of the feedback ratio and its phase is effected by means of the cathode loop 13.
The electron gun 3 is mounted directly on the internal projection of the member 2a of the resonator 2 axially thereof. The construction of the resonator 2 may also be used for operation with an external injector of charged particles.
For emergence of the beam of accelerated electrons from the resonator 2, a central orifice 26 is made in the wall of the internal projection of the inner member 2b of the resonator 2. The vacuum casing 1 is evacuated by means of coldcathode ion pumps 27. An outlet device 28 for scanning and emitting the beam into atmosphere is secured to the bottom wall on the lower side of the vacuum casing 1 (Figure 5).
The radio-frequency electron accelerator functions in the follow manner.
After evacuation of the vacuum casing 1 (Figures 1, 5), the supply source of the electron gun 3 and the heating supply source 10 of the oscillator tube 4 are energized. Upon energization of the supply source 11 of the anode, the oscillator is self-excited at the frequency which is close to the frequency of the high-Q accelerating resonator 2, and high voltage appears at the accelerating gap thereof, the value of the voltage depending on the area of the coupling loop 5 and supply source voltage. Electrons are drawn from the cathode of the electron gun 3 by the positive half-wave of the high-frequency voltage and accelerated in the accelerating gap 21 of the resonator 2.By varying the area of the coupling loop 5, the system may be matched with various accelerating voltages at a given output level of the electron beam; varying the length of the cathode loop 13 provides for accurate tuning of the feedback ratio and phase.
In order to inprove stability of operation of the accelerator, prolong the life of the electron gun 3 (Figures 2, 5) and suppress high-frequency resonance discharge in the resonator 2, negative d-c. voltage of several kV is applied to the lower inner member 2b of the resonator 2 from the source 16, the ions formed in the accelerating gap 21 being evacuated therefrom via the orifice 26.
In order to reduce losses of radio-frequency power which may leak through the gap 19 (Figures 3, 5) between the members 2a and 2b of the resonator 2, the edge 17 of the outer member 2a of the resonator 2 is electrically coupled to the metal vacuum casing 1 along the entire perimeter, and the natural frequency of the cavity between the inner member 2b of the resonator 2 and the vacuum casing 1 is selected to be sufficiently different from that of the accelerating resonator. Coupling of the outer member 2a of the resonator 2 to the vacuum casing 1 protects the cavity between the vacuum casing 1 and this member against penetration of radio-frequency power.
As differed from the above-described embodiments of the accelerator which may operate in both continuous and pulsed mode, the embodiment of the accelerator shown in Figure 4 is designed for operation in the pulsed mode only. It is noted that the time for gathering steady oscillation amplitude not only depends on the quality of the accelerating resonator 2 and feedback ratio, but is determined to a large extent by the initial amplitude of oscillations, that is the initial starting conditions and availability of auxiliary excitation of the accelerating resonator 2 by the moment of arrival of next pulse.Therefore, in order to reduce the time of growth of oscillations in the accelerating resonator 2, which is equivalent to improvement of efficiency due to an increase in useful pulse length, positive d-c. voltage is applied to the anode of the oscillator tube 4 via a pulse transformer 12 from an independent source 18 so that auxiliary excitation is provided for the resonator 2 during intervals between pulses.
The radio-frequency electron accelerator made in accordance with the construction shown in Figure 5 had the following specifications. Working frequency 110 MHz. Shunting resistance ofthe resonator 24 mOhm. Auxiliary excitation voltage 800 V. Voltage applied to the inner member 2b of the resonator 2-6 kV.
Voltage at the accelerating gap 21 which was 10 cm long -1.5 MV, with the anode supply voltage 23 kV. Pulse length 400 Ms, recurrence frequency 50 Hz.
The oscillator was built around a pulse-type oscillator triode 4 having a pulse output up to 2 MW. Average loss of power in the resonator 2 was from 4 to 5 kW, and average output of the electron beam was 20 kW which gave the electron efficiency of 80%. During tests, the accelerator worked to the above specifications continuously for 500 hours without disconnections. Maximum voltage obtained at the accelerating gap was 2 MW. A modulator of any appropriate type may be used for supplying the oscillator tube 4, provided it has sufficient output. With a voltage of up to 350 kV at the resonator 2, the accelerator may work in the continuous mode. The accelerator according
to the invention is reliable in operation and simple in manufacture.
WHAT WE CLAIM IS:
1. A radio-frequency electron accelerator comprising: an accelerating resonator comprising a resonant cavity encased in a metal vacuum casing, an electron gun for directing an electron beam along the axis of the cavity, a radio-frequency power source for transmitting radio-frequency energy to the electron beam which power source comprises a self
excited oscillator having a single oscillator tube
mounted directly on the resonator, a series
connected isolating capacitor and coupling loop
provided in the cavity of the resonator directly
connecting the anode at the tube to the resona
tor and forming, together with the tube out
put capacitance, the anode leadout inductance,
and the anode cooling water tank inductance, a
**WARNING** end of DESC field may overlap start of CLMS **.
Claims (6)
**WARNING** start of CLMS field may overlap end of DESC **. tuning of the feedback ratio and its phase is effected by means of the cathode loop 13. The electron gun 3 is mounted directly on the internal projection of the member 2a of the resonator 2 axially thereof. The construction of the resonator 2 may also be used for operation with an external injector of charged particles. For emergence of the beam of accelerated electrons from the resonator 2, a central orifice 26 is made in the wall of the internal projection of the inner member 2b of the resonator 2. The vacuum casing 1 is evacuated by means of coldcathode ion pumps 27. An outlet device 28 for scanning and emitting the beam into atmosphere is secured to the bottom wall on the lower side of the vacuum casing 1 (Figure 5). The radio-frequency electron accelerator functions in the follow manner. After evacuation of the vacuum casing 1 (Figures 1, 5), the supply source of the electron gun 3 and the heating supply source 10 of the oscillator tube 4 are energized. Upon energization of the supply source 11 of the anode, the oscillator is self-excited at the frequency which is close to the frequency of the high-Q accelerating resonator 2, and high voltage appears at the accelerating gap thereof, the value of the voltage depending on the area of the coupling loop 5 and supply source voltage. Electrons are drawn from the cathode of the electron gun 3 by the positive half-wave of the high-frequency voltage and accelerated in the accelerating gap 21 of the resonator 2.By varying the area of the coupling loop 5, the system may be matched with various accelerating voltages at a given output level of the electron beam; varying the length of the cathode loop 13 provides for accurate tuning of the feedback ratio and phase. In order to inprove stability of operation of the accelerator, prolong the life of the electron gun 3 (Figures 2, 5) and suppress high-frequency resonance discharge in the resonator 2, negative d-c. voltage of several kV is applied to the lower inner member 2b of the resonator 2 from the source 16, the ions formed in the accelerating gap 21 being evacuated therefrom via the orifice 26. In order to reduce losses of radio-frequency power which may leak through the gap 19 (Figures 3, 5) between the members 2a and 2b of the resonator 2, the edge 17 of the outer member 2a of the resonator 2 is electrically coupled to the metal vacuum casing 1 along the entire perimeter, and the natural frequency of the cavity between the inner member 2b of the resonator 2 and the vacuum casing 1 is selected to be sufficiently different from that of the accelerating resonator. Coupling of the outer member 2a of the resonator 2 to the vacuum casing 1 protects the cavity between the vacuum casing 1 and this member against penetration of radio-frequency power. As differed from the above-described embodiments of the accelerator which may operate in both continuous and pulsed mode, the embodiment of the accelerator shown in Figure 4 is designed for operation in the pulsed mode only. It is noted that the time for gathering steady oscillation amplitude not only depends on the quality of the accelerating resonator 2 and feedback ratio, but is determined to a large extent by the initial amplitude of oscillations, that is the initial starting conditions and availability of auxiliary excitation of the accelerating resonator 2 by the moment of arrival of next pulse.Therefore, in order to reduce the time of growth of oscillations in the accelerating resonator 2, which is equivalent to improvement of efficiency due to an increase in useful pulse length, positive d-c. voltage is applied to the anode of the oscillator tube 4 via a pulse transformer 12 from an independent source 18 so that auxiliary excitation is provided for the resonator 2 during intervals between pulses. The radio-frequency electron accelerator made in accordance with the construction shown in Figure 5 had the following specifications. Working frequency 110 MHz. Shunting resistance ofthe resonator 24 mOhm. Auxiliary excitation voltage 800 V. Voltage applied to the inner member 2b of the resonator 2-6 kV. Voltage at the accelerating gap 21 which was 10 cm long -1.5 MV, with the anode supply voltage 23 kV. Pulse length 400 Ms, recurrence frequency 50 Hz. The oscillator was built around a pulse-type oscillator triode 4 having a pulse output up to 2 MW. Average loss of power in the resonator 2 was from 4 to 5 kW, and average output of the electron beam was 20 kW which gave the electron efficiency of 80%. During tests, the accelerator worked to the above specifications continuously for 500 hours without disconnections. Maximum voltage obtained at the accelerating gap was 2 MW. A modulator of any appropriate type may be used for supplying the oscillator tube 4, provided it has sufficient output. With a voltage of up to 350 kV at the resonator 2, the accelerator may work in the continuous mode. The accelerator according to the invention is reliable in operation and simple in manufacture. WHAT WE CLAIM IS:
1. A radio-frequency electron accelerator comprising: an accelerating resonator comprising a resonant cavity encased in a metal vacuum casing, an electron gun for directing an electron beam along the axis of the cavity, a radio-frequency power source for transmitting radio-frequency energy to the electron beam which power source comprises a self
excited oscillator having a single oscillator tube
mounted directly on the resonator, a series
connected isolating capacitor and coupling loop
provided in the cavity of the resonator directly
connecting the anode at the tube to the resona
tor and forming, together with the tube out
put capacitance, the anode leadout inductance,
and the anode cooling water tank inductance, a
first resonant circuit of a two-circuit oscillatory system in the anode circuit of the osillator tube tuned to a frequency equal or close to that of a second resonant circuit formed by the accelerating resonator.
2. A radio-frequency electron accelerator as claimed in Claim 1, wherein the accelerating resonator comprises a pair of cup-shaped members partially received in each other with their open ends and electrically insulated from each other by providing a gap therebetween which defines a capacitor for closing the path of high-frequency currents, a d-c. voltage being applied to one of the members.
3. A radio-frequency electron accelerator as claimed in Claim 2, wherein d-c. voltage is applied to the inner member of the resonator, and the edge of the outer member is electrically coupled to the metal vacuum casing along the entire perimeter.
4. A radio-frequency electron accelerator as claimed in Claims I, 2 or 3, wherein the anode of the oscillator tube is connected to an independent positive d-c. voltage source for auxiliary excitation of the accelerating resonator during intervals between pulses when the accelerator functions in the pulsed mode.
5. A radio-frequency electron accelerator as claimed in Claims 1, 2, 3 or 4, wherein the isolating capacitor of the coupling loop comprises a system of plates having vacuum gaps therebetween.
6. A radio-frequency electron accelerator substantially as hereinabove described with reference to, and as shown in the accompanying drawings.
GB2871877A
1977-07-08
1977-07-08
Radio-frequency electron accelerator
Expired
GB1582267A
(en)
Priority Applications (1)
Application Number
Priority Date
Filing Date
Title
GB2871877A
GB1582267A
(en)
1977-07-08
1977-07-08
Radio-frequency electron accelerator
Applications Claiming Priority (1)
Application Number
Priority Date
Filing Date
Title
GB2871877A
GB1582267A
(en)
1977-07-08
1977-07-08
Radio-frequency electron accelerator
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Publication Number
Publication Date
GB1582267A
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GB1582267A
(en)
1981-01-07
Family
ID=10279988
Family Applications (1)
Application Number
Title
Priority Date
Filing Date
GB2871877A
Expired
GB1582267A
(en)
1977-07-08
1977-07-08
Radio-frequency electron accelerator
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GB1582267A
(en)
Cited By (1)
* Cited by examiner, † Cited by third party
Publication number
Priority date
Publication date
Assignee
Title
CN116271577A
(en)
*
2023-03-31
2023-06-23
中国工程物理研究院流体物理研究所
Flash X-ray radiation tumor treatment device based on repetition frequency induction accelerator and application thereof
1977
1977-07-08
GB
GB2871877A
patent/GB1582267A/en
not_active
Expired
Cited By (2)
* Cited by examiner, † Cited by third party
Publication number
Priority date
Publication date
Assignee
Title
CN116271577A
(en)
*
2023-03-31
2023-06-23
中国工程物理研究院流体物理研究所
Flash X-ray radiation tumor treatment device based on repetition frequency induction accelerator and application thereof
CN116271577B
(en)
*
2023-03-31
2023-11-14
中国工程物理研究院流体物理研究所
Flash X-ray radiation tumor treatment device based on repetition frequency induction accelerator and application thereof
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Legal Events
Date
Code
Title
Description
1981-03-25
PS
Patent sealed
1992-03-04
PCNP
Patent ceased through non-payment of renewal fee
