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TYC Lunchtime Seminar- Theory of Photoemission: Photocathodes for Free electron lasers

Victor Chang

Imperial College London

Monday 19th October 2020
Time: 12pm
Venue: MS Teams
Contact: Ms Hafiza Bibi

Abstract:

Free electron lasers (FELs) are recognised as the state-of-the-art in the generation of extremely intense coherent light. The generated light from a FELs open new windows in structural and dynamical studies from atomic to condense matter science. However, the high cost of FEL limits its availability to just a few facilities all over the world. Improvements in FELs that aim for not only an improve in performance but also its cost is a requirement.

 

One of the key components of a FELs is the photocathode, which is responsible for the generation of the free electrons that act as lasing medium. The main characteristics of an ideal photocathode is to be able to generate a high number of electrons with the narrowest spatial distribution possible. However, no material is known to fulfil these requirements. The lack of understanding of the relation between the chemical and structural properties of photocathode and the photoemission process has prevented us from the use of a rational approach.

 

In this work, we developed a computational model that simulates the photoemission properties of photocathode candidates from first principles. This model gives an insight of the physics underpinning the photoemission process by connecting electronic structure simulations with photoemission models and offers the flexibility to explore the effect of different modifications of the surface of a photocathode at the atomic level. Simulations are then compared to experimental measurements done by the ASTEC group at Daresbury Laboratories.

Victor Chang
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