Patent
1987-10-23
1989-03-14
Moore, David K.
328228, H05H 700
Patent
active
048127744
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
The present invention relates to a method of suppressing instability to be caused when electrons are to be accelerated from a low energy by an electron storing ring and a system for the method.
2. Background Art
The prior art has the following three systems as a storage ring system for accelerating and storing an electron beam. These three systems are shown in FIG. 2. The first one is a system constructed of a linear accelerator and a storage ring. The electron beam is accelerated to a final energy by the linear accelerator and implanted into the storage ring, in which the electrons are exclusively stored but not accelerated. This system can have a large storage current value but is accompanied by a defect that the linear accelerator becomes excessively long. The second system is constructed of a linear accelerator, a synchrotron and a storage ring. In this system, the electron beam is accelerated to the velocity of light by the linear accelerator and implanted into the synchrotron, in which the electrons are accelerated to the final energy until they are implanted into and stored by the storage ring. This system is also enlarged and complicated as a whole. In the third system, the electron beam is accelerated to several hundreds MeV by the synchrotron and further accelerated in the storage ring. This system has a smaller size than the foregoing two systems, because the electron beam is accelerated to several hundreds MeV by the synchrotron of the linear accelerator, but is still rather large as a whole.
In order to reduce the whole size of a system, as in the third system, the acceleration energy of the pre-accelerator may be dropped to about 10 MeV, at which the electrons acquire the velocity of light, and the electrons may be accelerated to the final energy in the storage ring. The system is further reduced in size if the deflecting magnet in the storage ring is made superconductive. In this case, however, it is anticipated that the electrons are lost one after another in the course of acceleration so that the number of electrons to be finally stored becomes small.
For example, in case electrons are to be accelerated from a low energy of about 15 MeV to several hundreds MeV, the electron beam is sequentially attenuated while it is being accelerated, even if its initial current value at 15 MeV is near 1 A, so that the electricity to be left at the final energy is as high as several tens mA. Several causes for the electron beam to be lost are being considered, some being clarified but others being still unclarified. One cause conceivable for the electron beam loss is the electron beam instabilizing phenomenon due to the interaction between the electron beam and a radio-frequency cavity. This instabilizing phenomenon is the more serious for the lower electron energy. In order to raise the storage current value, therefore, it is a requisite that no instability be caused anyhow.
For the reasons described above, it has never been conducted to make an acceleration from a low energy by the storage ring. However, the closest example is the synchrotron.
In this synchrotron, the beam is accelerated within a short time period of several msecs to pass through a low-energy region, where the instability is liable to occur, so that its loss may be prevented as much as possible. If, however, a superconductive magnet is used as a deflecting magnet for deflecting the electron beam, about ten seconds is required for the acceleration rising time. As a result, the storage ring using the superconductive magnet will not allow the electron beam to pass within the short time through the low-energy energy region where the instability is liable to occur.
One method of raising the threshold current value, at which the instability will occur in the storage stage of high energy not in the case of the synchrotron acceleration, is to cause the Landau damping with an octupole magnet. However, this octupole magnet not only widens the range of resonance but also intrinsically establishes a nonlinear magnet
REFERENCES:
patent: 2882396 (1959-04-01), Courant et al.
Miyata Kenji
Nishi Masatsugu
Tsumaki Koji
Hitachi Ltd
Moore David K.
Wieder K.
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