Electric lamp and discharge devices: systems – High energy particle accelerator tube – Electrostatic accelerator means
Reexamination Certificate
2001-03-08
2003-05-06
Anderson, Bruce (Department: 2881)
Electric lamp and discharge devices: systems
High energy particle accelerator tube
Electrostatic accelerator means
C315S507000, C315S500000, C315S005410, C315S005420, C315S111610, C250S492100, C250S493100
Reexamination Certificate
active
06559610
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to continuous wave electron-beam accelerators and continuous wave electron-beam accelerating methods thereof, and in particular, to continuous wave electron-beam accelerators for accelerating high intensity continuous wave electron beams particularly sludge for use in food irradiation, irradiation for quarantine, sludge processing, drainage processing, medical sterilization, the generation of low energy positrons, etc., and continuous wave electron-beam accelerating methods thereof.
2. Description of the Related Art
FIG. 10
shows a conventional electron-beam accelerator as described in, for example, Takahashi and Yamada, “Development of Small-sized Synchrotron Radiation Source ‘AURORA’”, Sumitomo Jukikai (Heavy Industries) Giho (Technical Report), Vol. 39, No. 116, 1991, pp. 2-10. This type of electron-beam accelerator is called a “race-track microtron”.
FIG. 10
shows an electron gun
111
, an injection electromagnet
112
, a radio frequency cavity (linac)
113
, bending electromagnets
114
, and electron beam orbits
115
.
The operation of the conventional electron-beam accelerator is described below.
An electron beam is generated by the electron gun
111
. The generated electron beam is a pulsed beam having a frequency of several hertz to several hundred hertz and a pulse width of ten nanoseconds to several microseconds.
The generated electron beam is injected into the electron-beam accelerator by the injection electromagnet
112
. In the electron-beam accelerator, the electron beam is accelerated whenever it passes through the radio frequency cavity
113
while passing along the electron beam orbits
115
. The electron-beam accelerator accelerates the electron beam by mainly using an S-band radio-frequency electric field (approximately 2.8 GHZ). When the electron beam passes through the radio frequency cavity
113
once, it usually obtains an energy of approximately 5 MeV. In order to form the electron beam orbits
115
, the bending electromagnets
114
are disposed across the radio frequency cavity
113
.
In the electron-beam accelerator, the acceleration phase of the electron beam each time it circumferentially passes through the radio frequency cavity
113
is uniquely determined by an expression of the relationship between an acceleration voltage in the radio frequency cavity
113
and the magnetic field strength of the bending magnets
114
. Accordingly, to enable the acceleration of the electron beam up to a high energy level, two conditions must be satisfied: (1) energy gain obtained when the electron beam passes through the radio frequency cavity
113
is close to a multiple of the electron rest energy (approximately 511 keV), and (2) the speed of the electron beam is close to the speed of light.
When the injection energy of the electron beam is low, the speed of the electron beam is much smaller than the speed of light (for example, when the injection energy is 80 keV, the electron beam speed is approximately half of the speed of light), the above conditions do not hold. In addition, when the energy gain obtained when the electron beam passes through the radio frequency cavity
113
is small, the number of circumferential passes of the electron beam until its speed approaches the speed of light increases, which causes a problem in that acceleration is difficult since a shift from the acceleration phase increases during the circumferential passes. Accordingly, the conventional electron-beam accelerator must be operated using parameters in which, by raising the acceleration voltage of the radio frequency cavity
113
, the electron beam speed almost reaches the speed of light when the electron beam is allowed to pass through the radio frequency cavity
113
once or slightly more.
In order to increase the acceleration voltage per unit length, the frequency of a radio frequency electric field applied to the radio frequency cavity
113
must be increased to approximately 1 GHz to 3 GHz. In order to increase the acceleration voltage of the radio frequency cavity
113
when the frequency of the radio frequency electric field is smaller than this value, the size of the radio frequency cavity
113
must be increased. This is because, while the electron beam passes through the radio frequency cavity
113
, it has a deceleration phase and can hardly be accelerated since a shift of the phase of the electron beam from the radio frequency acceleration electric field rapidly increases.
A radio frequency cavity having a radio frequency of 1 GHz to 3 GHz causes a problem in that it is difficult to accelerate a continuous wave electron beam having a large average current since the size of the radio frequency cavity is inevitably small and it is difficult to remove heat generated when high power is supplied. Therefore, it is difficult to apply electron-beam accelerators having a radio frequency cavity of this type to purposes requiring a high intensity continuous wave electron beam, such as food irradiation, irradiation for quarantine, sludge processing, drainage processing, medical sterilization, and generation of low energy positrons.
In the conventional electron-beam accelerator, the microtron acceleration condition must be satisfied such that the energy gain for each circumferential pass of the electron beam must be approximately a multiple of the electron rest energy (approximately 511 keV). Thus, a problem occurs in that electrical efficiency cannot be increased due to parameter limitation.
SUMMARY OF THE INVENTION
Accordingly, the present invention is made for solving the foregoing problems. A first object of the present invention is to provide a continuous wave electron-beam accelerator for accelerating an electron beam having a large average current and a continuous wave accelerating method thereof.
A second object of the present invention is to provide a continuous wave electron-beam accelerator in which an electron beam is accelerated without satisfying the condition that the energy gain for each circumferential pass of an electron beam must be approximately a multiple of the electron rest energy, which is required in microtron acceleration and in which parameters have more degrees of freedom, resulting in an increase in electrical efficiency, and a continuous wave electron-beam accelerating method thereof.
According to an aspect of the present invention, a continuous wave electron-beam accelerator includes an electron-beam generating unit for generating a continuous wave electron beam, an electron-beam accelerating unit for accelerating the continuous wave electron beam, a first electron-beam bending unit that is provided close to one end of the electron-beam accelerating unit and that bends the accelerated continuous wave electron beam, and a second electron-beam bending unit that is provided close to the other end of the electron-beam accelerating unit and that bends the accelerated continuous wave electron beam. Each of the first electron-beam bending unit and the second electron-beam bending unit includes a first bending electromagnet having a surface opposed to one side of the electron-beam accelerating unit, a second bending electromagnet and a third bending electromagnet which are discretely provided opposing another surface of the first bending electromagnet. The first bending electromagnet is made of a reverse bending electromagnet having a polarity opposite to that of the second bending electromagnet or the third bending electromagnet. The second bending electromagnet has a polarity identical to that of the third bending electromagnet, and has a first magnetic field strength different from that of the third bending electromagnet. The third bending electromagnet has a polarity identical to that of the second bending electromagnet, and has a second magnetic field strength different from that of the second bending electromagnet.
The present invention also provides a continuous wave electron-beam accelerator including an electron-beam generating unit for generating a continuous wa
Anderson Bruce
Leydig , Voit & Mayer, Ltd.
Wells Nikita
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