Beryllium source materials

New metliods appear regularly. The principal challenges to the ingenuity of the spectroscopist are availability of appropriate radiation sources, absorption or distortion of the radiation by the windows and other components of the high-pressure cells, and small samples. Lasers and synchrotron radiation sources are especially valuable, and use of beryllium gaskets for diamond-anvil cells will open new applications. Impulse-stimulated Brillouin [75], coherent anti-Stokes Raman [76, 77], picosecond kinetics of shocked materials [78], visible circular and x-ray magnetic circular dicliroism [79, 80] and x-ray emission [72] are but a few recent spectroscopic developments in static and dynamic high-pressure research. 

Figure 3.1 James Chadwick used the apparatus depicted above to discover the neutron. The poionium source emits alpha (a) particles. The particles strike a sample of beryllium, resulting in the emission of a neutron (n ). The ejected neutrons hit the target material—paraffin, for instance—and eject a proton that is recorded by the detection device.

The thermal neutron sources are radioactive isotopes which emit neutrons, acclerators, and nuclear reactors. The neutrons from the sources are moderated with materials such as paraffin, graphite, water, heavy water or beryllium. Some of the radioisotopes used as sources of thermal neutrons are antimony, polonium, americium curium and californium. The various sources have different half-lives, ranging from days to years. 

The name comes from the Latin Polonia, meaning Poland, the home country of Marie Curie, one of its discoverers. It was discovered by Marie Curie (1867-1934) and Pierre Curie (1859-1906) in 1898 when they were studying uranium and other radioactive materials found in pitchblende. Polonium is very rare, and, although some exists naturally, most polonium is manufactured in nuclear reactors. Polonium is very dangerous even in minute quantities because of its level of radioactivity. It is a very good source of alpha radiation and, if combined with beryllium, produces neutrons. It is thus used as a thermoelectric source for specialized applications such as satellites. 

Use Structural material in space technology moderator and reflector of neutrons in nuclear reactors source of neutrons when bombarded with a-parti-cles special windows for X ray tubes in gyroscopes, computer parts, inertial guidance systems additive in solid-propellant rocket fuels beryllium-copper alloys. 

X-ray pipes are used as the light source for x-ray fluorescence spectroscopy. There are very many types of x-ray pipes in the modern market. The functioning principle of the x-ray pipe is the same as for cathode lamps described in an earlier section of this chapter. The x-ray pipe contains an electrical heated cathode, anode and radiation output window. This window is made from beryllium because this material is transparent to x-rays. The x-rays pipes offered in the market differ because they have a different anode material, and consequently the spectral characteristics of the emitting radiation are different. 

Of the three moderators that make possible a fission chain reaction in natural uranium, heavy water, graphite, or beryllium, heavy water has become the preferred material. It is used both as coolant and moderataor in heavy-water reactors, which are the exclusive source of nuclear power in Canada, Argentina, and Pakistan, are being used in India, and are being considered in other countries wishing to have a nuclear power system not dependent on a source of enriched uranium. 

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