Speaker: Merijn Bronsgeest (Delft University of Technology, the Netherlands)
Title: The physics of creating electron beams with a Schottky source: the balance between brightness, energy spread and stability

Time: Today, 15.15
Place: Fysisk Auditorium

Abstract: 
The predominant source type for making focused electron beams is the Schottky electron emitter. The main questions that will be addressed are: what is the Schottky electron emitter, how does it work, and how do its properties affect the performance of a system at the target level?

Important factors are the brightness and energy spread of the beam leaving the source surface and also the stochastic interactions between electrons that can take place in the beam upon emission. How do these factors depend on the operating conditions of the source? A further parameter is the stability of the physical shape of the emitter. For good emission properties a high operating temperature is required (~1800 K). However, a high temperature also leads to unwanted surface diffusion processes that can cause changes of the shape of the emitter and thereby instability of the emitted beam. This means there is a trade-off to be made between brightness, energy spread and stability. It will be shown that different applications of electron beams require different parameters for the best possible results.

 

Peter Staanum and Nicolai Nygaard