High energy machines

For obtaining high energy particles or photons in the laboratory four types of machines are now employed betatrons, linear accelerators, synchrocyclotrons, and synchrotrons. The betatron was developed by Kerst. All betatrons in existence accelerate electrons. The electrons travel in a circular orbit of effectively constant radius. In a betatron the magnetic flux inside the orbit increasing with time accelerates the electrons. 

Synchrocyclotrons are a modification (by McMillan and Veksler ) of the original cyclotron of Lawrence and Livingston . Synchrocyclotrons (also called frequency modulated cyclotrons) compensate for the relativistic increase in mass of heavy particles by appropriately modulating the radio-frequency on the dees of the cyclotron. In a cyclotron, in contrast to other high energy circular accelerators, the magnetic field is kept constant in time and the particles increase their orbits (i.e. spiral paths). Synchrocyclotrons are used to accelerate protons, deuterons, or helium ions. 

Synchrotrons stem from the ideas of McMillan and Veksler. They are generally circular machines in which the orbit is effectively constant. The acceleration is by means of an alternating electric field (radio-frequency) across one or more gaps. For electrons the frequency is almost constant for protons the frequency has to be modu- 

A very valuable principle that enables synchrotrons to be built more economically was independently suggested by Courant, 

The above is only a brief statement of the differences between the machines. Much more information on the principles of these machines can be found in Vol. XLIV of this Encyclopedia, dedicated especially to them, or in Livingston s concise book. 

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High-energy machines require a supply not only of the type of particle desired, but also particles that have been preliminarily accelerated. Electrons are comparatively easy to generate as inputs to accelerators, as by the Cockcroft-Walion generator, Protons are obtained by ionizing hydrogen atoms. 

Natural radioactivity High-energy machines Nuclear reactors Artificial radioactivity a, / , y, x rays electrons, atomic nuclei, fast neutrons, heavy ions Electrons... 

CJ Mesic atoms. High energy machines have made possible the production in the laboratory of beams of n and fx mesons. When negative n or [jl mesons come to rest in matter, they are attracted by the positively charged nucleus in the same way as an electron. 

Semi-classical picture. The first results of high energy machine experiments with nucleons were immediately interpreted by Serber [4] on the basis of a very simple picture it continues as the basis for our physical understanding of many high energy experiments. It is difficult to improve on Berber s statements so several direct quotations from his paper follows ... 

Beschleunigungsanlagen fiir hohe Energien, high energy machines 468. 

The ability of some plastic systems to do this may be useful in schemes for handling the radiation output of nuclear devices, including the radiation from the fusion power machines under development. Obviously the application is not for shielding, which the heavy metals do much better, but rather for an energy level reduction system that would convert the high energy radiation to forms which would be more useful in power distribution. 

The alpha particles could be obtained from a natural decay process. At present, a variety of particles can be used to bombard nuclei (Table 22-3), some of which are raised to high energies in atom smashing machines. Again, nuclear equations can be written, in which the net charge and the total of the mass numbers on one side must be the same as their counterparts on the other side. 

Another interesting development is represented by the introduction (by NEC) of a new kind of AMS system based on single stage machines [64] the ion source and low energy side spectrometer are at ground potential, and the stripper and high energy spectrometer... 

Twin screw versions of dump extruders are available which are claimed to overcome some of the problems of single screw machines, i.e., high energy input, sticking and accelerated wear. 

Radiation therapy The use of high-energy radiation from x-rays, gamma rays, neutrons, and other sources to kill cancer cells and shrink tumors. Radiation may come from a machine outside the body (external-beam radiation therapy), or it may come from radioactive material placed in the body in the area near cancer cells (internal radiation therapy, implant radiation, or brachytherapy). Systemic radiation therapy uses a radioactive substance, such as a radiolabeled monodonal antibody, that circulates throughout the body. Also called radiotherapy, [nih]... 

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