Thermal-field and photoemission from meso- and micro-scale features: Effects of screening and roughness on characterization and simulation
Abstract
A methodology of modeling nonplanar surfaces, in which the microscale features of the emission sites can be orders of magnitude smaller than the mesoscale features defining the active emission area, has been developed and applied to both ordered arrays of identical emitters and random variations characteristic of a roughened surface. The methodology combines a general thermal-field-photoemission model for electron emission, a point charge model for the evaluation of field enhancement factors and surface geometry, and a Ballistic-Impulse model to account for the trajectories of electrons close to the cathode surface. How microscale and mesoscale features can both undermine the estimation of thermal-field emission parameters, such as characteristic field enhancement and total current predictions, as well as give rise to changes in the distribution of transverse velocity components used to estimate beam quality features such as emittance that are important to photocathodes, is quantified. The methodology is designed to enable both the proper characterization of emitters based on experimental current-voltage data and the development of a unit cell model of emission regions that will ease the emission model demands in beam optics codes.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Jun 20, 2019
- Source ID
- 10.1063/1.5097149
Entities
People
- Aaron J. Jensen
- D. Shiffler
- J. R. Harris
- John Petillo
- Kevin L. Jensen
- M S McDonald
- Nathan A Moody
- Oksana Chubenko
Organizations
- Air Force Office of Scientific Research
- Air Force Research Laboratory
- Arizona State University
- Los Alamos National Laboratory
- United States Naval Research Laboratory