Speaker
Description
The surfaces of electron sources exhibit non-planar features (intentional ordered arrays here but the methods apply also random surface roughness), the dimensions of which are typically microscale and therefore much smaller than the active emission area [1, 2, 3]: because emission area is already small by comparison to device dimensions, such differences in magnitude are a challenge to beam optics codes. Moreover, such structure complicates both the inference of physical properties such as work function and field enhancement from current data, and the determination of transverse velocity components that are essential for determining a cathode’s intrinsic emittance. We report on the development of semi-numerical methods based on point and line charge [4] models for modeling ordered and rotationally symmetric emitters, and the use of a general thermal-field model for calculating emitted current [5]. The emitter protrusions are the equpotentials of a Point Charge Model (PCM) where the locations and charge magnitudes can be adjusted with great flexibility. A Ballistic- Impulse model that modifies trajectories near the surface of the cathode is implemented via altering the launch velocity in a form to be specified. We analyze how the microscale features undermine the estimation of oft-used parameters such as field enhancement and total emission area, and how well the models account for beam's velocity components. For the latter, a comparison is made to numerical simulations using the Particle-in-Cell code MICHELLE [6].
References
[1] K.L. Jensen, et al., PRST-AB 17, 043402 (2014).
[2] K.L. Jensen, et al., JAP117, 194902 (2015).
[3] N.A. Moody, et al., Physical Review Applied 10, 047002 (2018).
[4] J.R. Harris, et al., Journal of Physics D: Applied Physics 48, 385203 (2015).
[5] K.L. Jensen, et al., J. Appl. Phys. 123, 065301 (2018).
[6] John Petillo, IEEE Trans. Plasma Sci. 30, 1238 (2002); IEEE Trans. Electron Devices 52, 742 (2005).
