Particle accelerators, beryllium

An important reaction used quite widely for this purpose is irradiation by neutrons and measurement of die energies of radiations emitted. The source of the neutrons may be a nuclear reactor, a particle accelerator, or an isotopic source, that is, a sealed container in which neutrons are produced by alpha rays emitted by a source such as radium, sodium-24(24Na), yttrium-88f8sY), etc., and arranged so that the alpha rays react-with a substance such as beryllium which in turn emits neutrons. The neutrons react with stable nuclides in the sample to produce radioactive ones. Thus... 

Another view, equally consistent with the source abundances and better suited to account for the abundance of light elements like beryllium in stars of the Galactic halo (see below), is that dust particles in the supernova ejecta are the source of ions that are preferentially accelerated within the hot, tenuous gas of superbubbles surrounding regions of star formation (Lingenfelter, Ramaty Kozlovsky 1998). 

Nuclear Accelerators and Mass Spectrometers. An interesting area is that of using nuelear accelerators as high-sensitivity mass spectrometers. As recently as a decade ago. the Grenoble cyclotron was used as a mass spectrometer in measure ratios of l"Be/, Be of 10 s. ID- 1, and 10 111 in standardized beryllium oxide samples. Measurements of this type also can be used in determine cosmogonic M,Be profiles in various geophysical reservoirs, such as sea sediments and polar ice. Sec also Particles fSubatomic). 

To perform the experiment [41] an intense beam of high-energy K was constructed at Fermilab. After the 400 GeV/c proton beam struck a beryllium target, a series of collimators and magnets defined the beam and swept charged particles from the flux of secondaries emerging in the forward direction (Fig. 5). The average K momentum was about 75 GeV/c, and typical intensities were about 107 K s and 109 neutrons per accelerator pulse. The setup detected the pions and muons from the decay... 

Neutrons bear no charge, so they are not repelled by nuclei as positively charged projectiles are. They do not need to be accelerated to produce bombardment reactions. Neutron beams can be generated in several ways. A frequently used method involves bombardment of beryllium-9 with alpha particles. 

And in starspots, where the magnetic field may be many times greater than in sunspots, we expect particles of very high energy. These naturally accelerated particles can produce elements like lithium, beryllium, and boron which are very rare in the stars but which have been detected by analyzing starlight with a spectroscope. 

Beryllium windows are often used in particle beam accelerators. (Alexander Tsiaras/Photo Researchers, Inc.)... 

What is needed is a window that does not change the nature of the subatomic particles created in the collision. Beryllium is the element of choice, as it has a low atomic number, which means there are fewer protons and electrons to interfere electromagnetically. The element can be made into a metal more easily than hydrogen or lithium, and it is strong, even as a thin foil. This is important because accelerator beam pipes must be evacuated of air particles as much as possible to minimize unwanted collisions. So a huge pressure differential exists between the inside and outside of the beam pipe. Implosion would be a risk with a weaker material. 

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