Accelerators with similar orbits

We obtain the conditions that must be satisfied by a magnetic system in order that the frequencies of radial and vertical betatron oscillations be independent of the particle momenta (in this case the orbits are called dynamically similar). In such systems mere should in principle be no excitation of betatron oscillations associated with synchrotron oscillations and other phenomena. A magnetic field with n₀ = const produces both geometric and dynamic similarity of the orbit. In weak-focusing accelerators with segments (race tracks) and in strong-focusing proton synchrotrons, the orbits are not dynamically similar. In order to obtain this kind of similarity in the first case, in addition to n₀ = const it is necessary that the magnet sectors have a common center. Different types of annular synchrocyclotrons are considered. In the first type the centers of neighboring magnet sectors are located on different sides of the doughnut and in the second type at the same point (at the center of the accelerator). In the second type the orbits are dynamically similar, unlike those of the first. It is shown mat it is possible to design an annular synchrocyclotron in which the particles can move with stability simultaneously in both directions within the doughnut.     

Accelerators with stable joined particle trajectories

A new class of accelerators is considered; in these accelerators the magnetic system consists of several sectors which are separated by gaps characterized by very weak fields. The magnetic system has two mutually perpendicular planes of symmetry but does not have an axis of symmetry nor a center of symmetry. All the particle orbits pass through a common point at which the acceleration element, a cavity resonator, is located. The stability of particle motion is provided by virtue of the effect of the fringing magnetic fields of the sectors. The magnetic system being considered may be used in cyclotrons and microtrons. The advantages of this new class of accelerators are the higher ion-beam intensity, the lower power supply requirements, the possibility of extracting panicles at any orbit and the possibility of varying the particle energy in the extracted beam over wide limits.     

Super-Energy Accelerators

The further development of high energy physics through the next decade will require new accelerators capable of energies of an order of magnitude greater than presently available. A brief review is given of the current status of plans for the "super-energy" accelerators. Basic parameters are presented for machines in the 200-1000 BeV energy range and the current study at the Lawrence Radiation Laboratory of a 200 BeV accelerator is described in some detail, as an example of the general class.     

Wide-Aperture Electron Accelerators

Wide-aperture low-energy electron accelerators, which provide simultaneous irradiation of large surfaces and volumes, are used in radiation technology, ionization setups for gas lasers, and in scientific research. Certain modifications of wide-aperture electron accelerators – ionization setups for CO and CO₂ lasers and ozone generator based on an electron-beam-controlled discharge – are described.     

High Energy Electron Accelerators

The Cambridge Electron Accelerator is now in full-scale operation for research at energies up to 6 Bev, five times higher than earlier electron accelerators. The machine, a synchrotron, uses a ring of 48 alternating gradient magnets in a circle 236 feet in diameter. Electrons are accelerated by RF fields produced in a set of sixteen resonant cavities spaced around the orbit. The frequency used is 476 Mc/s, the 360th harmonic of the orbital frequency. Injection of 30-Mev electrons is accomplished by using a linear accelerator operating at 2855 Mc/s. The main machine accepts and-accelerates to maximum energy beam currents of up to 1.2 x 1012 electrons/sec. The quality of the beam is fully as good as that from a linear accelerator. The CEA laboratory operates five days a week on a three-shift basis and has a staff of 160 people.     

Advances in Electrostatic Accelerators

Advances in the design and performance of electrostatic accelerators since 1969 are reviewed with special emphasis on the "forefront" accelerators that are currently leading in voltage capability. A comparison of the acceleration tube design offered by the National Electrostatics Corporation and the High Voltage Engineering Corporation will also be made. Other methods of increasing heavy ion energy by means of dual foil stripping will be discussed as well as the performance of a newly developed sputter ion source for the production of negative heavy ions with reliability and flexibility that greatly exceeds all other present systems. Finally, new developments in terms of both booster systems and very high voltage electrostatic accelerators (25-60 MV) are discussed.     

Impact of Accelerators on Technology

Accelerators and accelerator technology has rapidly expanded into Medicine and Industry. The 2500 accelerators in the USA, which represent about 2/3 the worldwide census of accelerators are primarily devoted to practical applications, although the major impact on technology has been produced by a relatively few excellent facilities. Approximately 80% of the current accelerators in the USA are found to be in medical and industrial use representing a capital investment by industry of $200,000,000. Of greater importance is their impact on the treatment of cancer, and the improvement or creation of better products for industrial and consumer use. The development of new accelerators and techniques are required in order to insure continuing benefits to the public.     

Some Medical Applications of Accelerators

The present uses of accelerators in nuclear medicine and radiation therapy are summarized. Attention is called to the widespread use of these devices for production of radioisotopes for diagnostic purposes and of x rays for treatment of cancer. Developments presently underway to make use of high energy heavy nuclear particles for both isotope production and therapy are discussed and an overview is presented of one of a new family of accelerators nearing completion. In view of the large fraction of the total population who stand to benefit from better diagnostic and therapy modalities, the question is posed whether more adequate resources should not be made available for improving diagnostic and therapeutic capabilities while minimizing radiation dose to the patient.     

High Intensity Multi-GeV Proton Accelerators

For performing many high-energy physics experiments, it is necessary to have high-energy particle beams of very high intensity. The intensity of particle beams in circular proton accelerators in the multi-GeV energy range depends, first, on the number of protons accelerated per pulse and, second, on the number of pulses per second. The number of protons which can be accelerated per pulse is limited by the space charge effects, and the number of pulses per second is limited by the design or type of the accelerator. These intensity limitations and methods of pushing back these limits are discussed. It is now feasible both technologically and economically to construct accelerators in the tens of GeV energy range which will accelerate more than 1014 protons per second.     

Transients in Large Tandem Accelerators

The stored energy in dc accelerators capable of reaching terminal potentials of 30 or 40 MV is more than an order of magnitude greater than in existing machines. To analyze the concentration of electrical fields under surge conditions the accelerator has been modeled by lumped constant networks. The analysis shows that in structures similar to the present ones the voltage distribution during a surge is very uneven and micro-discharges in the tube can initiate complete accelerator collapse.