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Emittance and entropy of electron beams

dc.contributor.advisorBrau, Charles A., 1938-
dc.contributor.authorErickson, Collin
dc.description.abstractCreating high-brightness electron beams, which have many practical applications, is done with cathodes in regions with large electric field by field emission. The brightness is high when the current is high and the volume of the beam in phase space is small. An estimate of the phase space volume is the rms emittance. The simulations described in this report show that the beam emitted by a gated diamond field emitter of the type fabricated at Vanderbilt has an exquisitely small emittance, on the order of a few nm. This is probably too small to measure. The rms emittance is generally thought to be constant for a beam or increasing in the presence of aberrations in the beam optics, but simulations show that this is not true. The rms emittance rises and falls according to the geometry that surrounds the beam. The entropy of an electron beam can be calculated, and should be constant if done in six dimensional phase space, and approximately constant in four dimensions. Calculations show that the entropy is not constant in two nor four dimensions. Rather, the entropy changes over time with a shape similar to how the emittance changes, which includes a local maxima at the entrance to an aperture and minima on either side. It is not clear if the fault is with the calculations or theory. To our knowledge, this is the first time that the entropy of a particle beam has been computed and used in a quantitative fashion. Future research should explore the applications and limitations of this concept.en_US
dc.publisherVanderbilt University. Department of Physics and Astronomyen_US
dc.rightsCC0 1.0 Universal*
dc.subjectelectron beamsen_US
dc.subjecthigh-brightness electron beamsen_US
dc.subjectrms emittanceen_US
dc.subjectfield emission cathodeen_US
dc.subjectbeam entropyen_US
dc.subject.lcshElectron beamsen_US
dc.subject.lcshBeam emittance (Nuclear physics)en_US
dc.subject.lcshField emission cathodesen_US
dc.subject.lcshParticle beamsen_US
dc.subject.lcshHigh-brightness acceleratorsen_US
dc.subject.lcshPhase space (Statistical physics)en_US
dc.titleEmittance and entropy of electron beamsen_US
dc.description.collegeCollege of Arts and Scienceen_US
dc.description.departmentDepartment of Physics and Astronomyen_US

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CC0 1.0 Universal
Except where otherwise noted, this item's license is described as CC0 1.0 Universal