Patent Number: 050341839
Section: description

DETAILED DESCRIPTION OF THE INVENTION In its simplest form, the invention of the present invention includes a ring-shaped magnetic field within the evacuated field of an apparatus for obtaining a self-colliding beam of charged particles. Such an apparatus is shown in the above-cited U.S. Pat. No. 4,788,024 to Maglich and Manasian, the disclosure of which, as noted previously, is hereby incorporated by reference as if fully recited herein. The invention of Maglich and Manasian, however, uses a magnetic field falling off weakly with radius. In such a field, ion orbits will cross each other at the axis of symmetry and precess around that axis. The present invention is intended to improve on the containment methodology of Maglich and Manasian by the introduction of a versatile reflecting field which makes possible the achievement of materially higher ion densities, and which can also be employed to selectively expel ions whose energies are too high or too low. In FIG. 1, a ring-shaped magnetic field is provided around the axis of symmetry shown as A--A. this field is created some means, such as the wire-wound coils (10, 12, 20 and 22), possibly with iron yokes, which surround the axis, above and below the median plane B--B. The magnetic field produced by these coils is shown diagrammatically in FIG. 2. FIG. 2 shows a possible shape for the paraxial magnetic field in the median plane. The field strength inside the ring (between the magnet structure and the axis) may be zero or may be positive or negative and may vary with radius in a fashion dictated by the particular application the user has in mind. In particular, the magnetic field of the present invention may surround the field employed in U.S. Pat. No. 4,788,024. Fields elsewhere in the space are determined from the median plane field pattern and the coil structure by the laws governing electromagnetic fields. Charged particles (ions) are injected into the evacuated region, by various possible and well-known procedures, in such a fashion that their orbit passes through the axis. The particle energy and the field strength are chosen such that the ring field serves as a mirror and reflects the ion back to the axis. The ion orbit, seen from above, will then be as shown in FIG. 3. Evidently the orbit precesses around the axis and, when many ions have been injected, there will be an intense concentration near the axis both of ions and of ion collisions. It is necessary to review the motion of the ions normal to the median plane to determine whether the ions will be restrained to travel in stable orbits or whether they can be lost in the axial direction. Employing the magnetic field of the present invention, an ion coming from the axis on an orbit not in the median plan, hereinafter referred to as an errant ion, will first encounter a rising field. This field will have a radial component that interacts with the azimuthal component of ion velocity in such a sense as to deflect the ion away from the median plane. When such an errant ion enters the falling field pattern it will encounter a field force component directed back toward the median plane. This force will be strong for two reasons. First, the rising field has pushed the ion away from the median plane to regions where the restoring force (roughly proportional to distance from the median plane) is stronger. Second, because of the curvature of the orbit, the azimuthal component of velocity is becoming predominant; the restoring force is proportional to this component. Thus we have a version of the "strong-focusing" or "alternating-gradient focusing" used in all modern particle accelerators, where, as in optical systems, a combination of focusing and defocusing lenses can be strongly focusing. Three types of orbits are possible and are illustrated in FIG. 4. All three are shown entering the ring field on orbits parallel to the median plane but displaced from it. Orbit 1 is for an ion whose energy is too low; it penetrates the magnetic field only to point (a), whichis not far enough into the restoring field to have its direction restored toward the median plane. It will leave the ring field with its paraxial velocity component directed away from the median plane and will be lost. Orbit 2 is for an ion whose energy lies in an acceptable range. It penetrates the magnetic field to point (b). Its direction has been restored toward the median plane and it will enter the ring field on the opposite side with a displacement less than its initial displacement. It will continue to be reflected back and forth by the ring magnet on orbits which, from above, will look like the orbits shown in FIG. 3. Orbit 3 is for an ion whose energy is so high that it penetrates too deeply into the falling-field, focusing region at point (c). In this case, "overfocusing" will occur; the ion direction is restored so strongly that it crosses the median plane before reaching the axis and so reaches the ring field again displaced further from the median plane than it was initially. Its paraxial displacement will continue to increase and eventually it will be lost in the axial direction. Thus it is evident that the ring field is selective. Ions of too low energies will not penetrate far enough into the restoring field. Ions of too high energies will penetrate too far. In both cases the ions will be lost in the axial direction. The proportional energy range to be accepted will be determined by the geometry of the field, and many field geometries are possible and may be preferred for different applications. A field pattern like that indicated by A--A in FIG. 5 will accept a relatively narrow energy range (10 to 20% of the mean energy). By decreasing the slope on the falling side of the field pattern as shown by the shape B--B in FIG. 5 the energy range accepted can be increased to an desired fraction of the mean energy. If the magnetic field inside the ring is small or zero, it may be desirable to provide a supply of electrons to neutralize the ion space charge forces and so to be able to increase the ion density to much higher levels. This is done in the device of U.S. Pat. No. 4,788,0234, but there the electron motion is restricted by the strong magnetic field present everywhere and neutralization may be incomplete. In the present invention, if the central magnetic field is zero or weak, the electrons are free to migrate to wherever they are needed for neutralization. Statements made above about magnetic fields and ion orbits follow from calculations using electromagnetic theory and the dynamics of charged particles. The correctness of the conclusions presented above will be evident to those skilled in the disciplines mentioned. The conclusions presented hereby apply to ions of any type over a wide range of energies ranging from hundreds to billions of electron volts. Magnetic fields required are readily attainable using conventional (possibly superconducting) magnet structures. Variations of the invention will readily occur to those skilled in the art--for example the system may include more than one ring magnet system or systems of various other geometries. Such changes do not depart from the spirit and scope of the invention. Possible applications of the ring magnet system are listed below. 1) Energy production. Numerous reactions between light nuclei yield important quantities of energy (see, for example, the Proceedings of an International Symposium on Aneutronic Energy, Nuclear Instruments and Methods in Physical Research, Vol. A271, No. 1) The colliding beam system presented in this invention can be used to produce these reactions at rates sufficient to produce significant quantities of energy--possibly to pass the "breakeven" point and be able to contribute to the national energy resources. 2) Neutron source. Collisions between deuterons (and many other nuclei) yield neutrons. The present invention can be an important source of intense neutron yields. Intense neutron sources are needed for many applications including deactivation of radioactive waste. 3) Tritium production. Tritium, the hydrogen isotope of mass 3, is produced in collisions between deuterons (and in other nuclear reactions). Tritium is needed in some quantities for defense applications--it can be produced in useful quantities in the present invention. The above applications call for ions in the energy range about 1 MeV. (1 million electron volts.) At energies higher by several thousand (in the GeV range) other important applications may become possible. Three examples follow: 4. Production of antimatter. Antiprotons are produced in many types of nuclear collisions at multi-GeV energies. These are the nuclei of antihydrogen. Antimatter could have many important uses and is of considerable present interest; it may be produced in significant amounts in the present invention. 5. High energy physics. The basic structure of the nucleon is under study in several colliding-beam accelerator laboratories. In deed, this is the objective for the costly "Superconducting Super Collider (SSC)" project now under development. With the present invention, build for multi-GeV energies, colliding beam studies would be possible with much higher intensity than possible using conventional accelerators. The present invention could be an intense meson source. It could at last be used to study collisions between mesons, which was the original (1970) objective of Maglich's colliding beam invention. 6. Synchrotron radiation. Energetic electrons in the ring magnet system will travel on paths similar to those travelled by ions. At energies in the 1 GeV range they will radiate intense synchrotron light from the curved part of their paths. Thus a ring magnet system supporting electron beams could be an intense source of synchrotron radiation, not in discrete beams as in present synchrotron radiation sources, but in all directions. A suitably located radio frequency accelerating system would be needed to supply the energy radiated by the electrons.