Beam Emission Studies

The Transverse Energy Spread Spectrometer (TESS) is an experimental facility constructed by ASTeC, designed to measure longitudinal and transverse electron energy. It can give important insight into the properties of an electron beam, in particular its emittance. In accelerator physics we care about emittance as it is a key parameter describing the performance of any beam in an accelerator or light source.

TESS is specifically investigating into an improved understanding of the emission process from various photocathode materials. This research uses Einstein’s theory of the photoelectric effect which explains how electros are emitted from metals when hit with light. 



TESS started investigating different semiconductor materials and is now used to study various metals.It has recently been upgraded with a modified detector and a laserdriven plasma broadband light source (Energetiq EQ-99), coupled to a high-performance monochromator (Bentham TMC300 f /4). 

The intrinsic emittance of the photo cathode is strongly affected by its surface roughness, and understanding the impact of different surface roughnesses on transverse energy is important for the electron source community. 

In the QUASAR Group we started being involved in TESS through beam emission and transport studies and are currently working on the in-detail characterisation of different cathode materials. TESS helps us better understand the photocathode characteristics and potentially design and build accelerators at lower costs and better performance in the future. 


Selected publications:

'Measurement of the longitudinal energy distribution of electrons in low energy beams using electrostatic elements', L. J. Devlin, L. B. Jones, T. C. Q. Noakes, C. P. Welsch and B. L. Militsyn, Review of Scientific Instruments 89, 083305 (2018);

'Transverse energy distribution measurements for polycrystalline and (100) copper photocathodes with known levels of surface roughness', L.B. Jones, B.L. Militsyn, T.C.Q. Noakes, D.P. Juarez-Lopez, C.P. Welsch, Proc. IPAC18, Vancouver, Canada. (2018) THPMK062

'Charged particle tracking through electrostatic wire meshes using the finite element method', L.J. Devlin, O. Karamyshev and C.P.Welsch, Physics of Plasmas (Vol.23, Issue 6) DOI: 10.1063/1.4953801 (2016)

'Measurements of the Longitudinal Energy Distribution of Low Energy Electrons', L. Devlin,  Proc. IPAC, Dresden, Germany (2014)