Paper  Title  Page 

TUODC01  Detailed Photoemission Modeling Using the 3D FiniteElement PIC Code MICHELLE  904 


Funding: We gratefully acknowledge funding by the Joint Technology Office and the Office of Naval Research.
Low emittance, high current density sources are required to achieve the small beam size needed for high frequency vacuum electronic devices and for high power free electron lasers (FELs). Emission models are of particular importance in the emittancedominated regime, where emission nonuniformity and surface structure of the cathode can have an impact on beam characteristics. We have been developing comprehensive timedependent photoemission models for the simulation codes that account for laser and cathode material and surface characteristics. MICHELLE* is NRL's finiteelement selfconsistent electrostatic timedomain code: it has the ability to import an RF field, and has unique capabilities for modeling the emission and the self fields, near the cathode. In particular, some instances of surface irregularities and emission nonuniformity (due to work function variation) leading to such effects as beam emittance and high frequency oscillations are possible to model due to the code's conformal meshing capabilities. We will present results of the implementation of the 'next generation' photoemission models in the MICHELLE code for modeling surface roughness and nonuniformity.
* John Petillo, et al., "The MICHELLE ThreeDimensional Electron and Collector Modeling Tool: Theory and Design", IEEE Trans. Plasma Sci., vol. 30, no. 3, June 2002, pp. 12381264. 

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