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   COLLOQUIUM OF THE LABORATORY FOR COMPUTER DESIGN OF MATERIALS
                   School of Computational Sciences
                           (CSI 898-Sec 001)
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	Numerical Modeling of Field-Enhanced Photoemission from
		Metals and Coated Materials

           		 Kevin L. Jensen
	Naval Research Laboratory, Code 6841, Washington DC

Electron sources are important for a variety of applications, from lithography
to radar to accelerators.  Analogously, a variety of methods are used to
generate electron beams, from heating to high fields to incident lasers.  In
this talk, we shall provide a general introduction to the theory of electron
emission to describe the various technologies.  Of particular interest is the
photoemission process, as photocathodes are critical components of Free
Electron Lasers, where the quality and characteristics of the electron beam
are of paramount importance.  Laser-induced photoemission, especially from
high intensity lasers under high fields, is complicated by all of the emission
processes we shall discuss, but also is affected by laser heating and electron
transport in bulk materials.  To increase Quantum Efficiency  (ratio of
electrons out to photons in), often use is made of low work function coatings
(alkali metals) that makes conditions at the surface quite important.  The
models we have developed are designed to account for conditions at the
surface, the mechanisms that affect electron transport through the bulk
material, and complications due to the surface barrier.  The goal is to
predict current distribution and quantum efficiency depending on material and
laser characteristics.  The predictions of the photoemission model in terms of
emitted current and quantum efficiency are compared to our experimental QE
measurements of and to findings in the literature.

                         October 31, 4:30 pm
               Room 206, Science & Tech. I, Fairfax Campus

Refreshments will be served at 4:15 PM.
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Find the schedule at http://www.scs.gmu.edu/lcdm/seminar/schedule.html
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