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Researchers show plasmas can focus high-energy electron, positron beams. (Accelerators).



A Lawrence Livermore National Laboratory Lawrence Livermore National Laboratory: see Lawrence Berkeley National Laboratory.

(body) Lawrence Livermore National Laboratory - (LLNL) A research organaisatin operated by the University of California under a contract with the US Department of Energy.
 researcher has shown that plasmas can focus high-density, high-energy (30 GeV) electron and positron positron: see antiparticle.
positron

Subatomic particle having the same mass as an electron but with an electric charge of +1 (an electron has a charge of −1). It constitutes the antiparticle (see antimatter) of an electron.
 beams 1,000 times better than the magnetic quadrupoles used in conventional accelerators.

In the E150 experiment on Stanford Linear Accelerator linear accelerator: see particle accelerator.
linear accelerator
 or linac

Type of particle accelerator that imparts a series of relatively small increases in energy to subatomic particles as they pass through a sequence of
 Center's (SLAG) Final Focus Test beam, a plasma could focus an electron beam A stream of electrons, or electricity, that is directed towards a receiving object. See electron beam imaging and electron beam lithography.  to a third of its original diameter in just 2 centimeters.

In addition, the researchers demonstrated plasma focusing of high-energy positron beams for the first time.

Technologies have existed for focusing MeV electron beams, but not for the GeV beams. that will be used in future accelerator experiments.

The SLAG work demonstrates a potentially promising technique for focusing those GeV beams. The plasma's focusing effect The focusing effect (or focusing illusion) is a cognitive bias that occurs when people place too much importance on one aspect of an event, causing an error in accurately predicting the utility of a future outcome.  was anticipated in earlier theoretical and experimental research, but not demonstrated until now.

Competing Forces Influence Beam

How does a plasma focus particle beams so well? To understand this effect, researchers point out that it is important to realize electrons, or other electrically charged particles, in a beam experience two competing forces: a repulsive "Coulomb coulomb (k`lŏm) [for C. A. de Coulomb], abbr. coul or C, unit of electric charge. The absolute coulomb, the current U.S. " force which tries to make the beam blow apart, and magnetic forces which push the electrons together.

As it passes through a plasma, the high energy beam will redistribute the electrons so that the net Coulomb force is decreased but the magnetic force is not affected. This serves to pinch the beam closer together.

Conventional plasmas seem to focus beams very well; so it appears that no exotic plasmas will need to be prepared, the researchers concluded.

Contact: Hector Baldis, Lawrence Livermore National Laboratory, (925) 422-0101, baldisl@l1nl.gov; or visit the SLAG Web site: http://www.slac.stanford.edu/exv/el150.
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Publication:Fusion Power Report
Article Type:Brief Article
Geographic Code:1USA
Date:Nov 1, 2000
Words:275
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