Cockcroft—Walton source

The original construction named as Cockcroft-Walton source and shown schematically in panel (a) of Pig. 50.15 can be used in the region ofa few hundred kV (Baldinger 1959). In this voltage source, N stages composed of a pair of rectifiers and capacitors of C capacitance are fed in series through the chain of capacitors. Due to AC feeding with frequency/ of the system, and a load of current I, a ripple of... 

Fig. 3. Principle of linear accelerator (linac). Partially accelerated electrons from a source, such as a Cockcroft-Walton generator, arc further accelerated by stages as rhe electrons pass through radio-frequency cavities, powered by if oscillators. Each paiticle receives a small push as it passes from one cavity to the next until the final desired accelerated beam is produced Tile machine must be carefully synchronized CSG = Cockcroft-Walton generator, RFO = radio-frequency oscillator RFC = radio-frequency cavity...

The most common sources are based on the 3H(d, n) reaction. Deuterons are accelerated to 150 keV with currents 2.5 mA and strike a tritium target. They produce 2 x 1011 of 14-MeV neutrons/s under these conditions. The neutrons produced are widely used in fast neutron activation analysis for the determination of light elements. The tritium targets are typically metals such as Ti, which have been loaded with titanium tritide. The accelerators are usually small Cockcroft-Walton machines or small sealed-tube devices where the ion source and accelerator structure are combined to produce a less expensive device with neutron yields 108/s. 

In a single-stage accelerator, such as a Cockcroft-Walton type, the total potential produced from a high voltage generator is imposed across the accelerator, i.e. between the ion source and the target. The kinetic energy, of the projectile is ... 

This particular reaction is of interest for several reasons. It was the first nuclear reaction that was produced in a laboratory by means of artificially accelerated particles (Cockcroft and Walton 1932 cf. 13.3). Reaction (b) is still used for the production of y-radiation (17 MeV), while reaction (c) is used as a source of mono-energetic neutrons. The energy of the neutrons from reaction (c) is a function of the proton energy and the angle betwe the neutron and the incident proton beam. A necessary requirement, however, is that the threshold energy (1.64 X (8/7) = 1.88 MeV) must be exceeded, the g-value for reaction (c) being —1.64 MeV. 

The a-particles used came from a natural source. In 1932 J. D. Cockcroft and E. T. S. Walton, in Rutherford s labor.atory in Cambridge, disintegrated lithium into helium ... 

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