Applications for this project are now closed.
Angle-resolved photoemission spectroscopy (ARPES) is the most direct probe of electronic structure in solids. By analysing the energy and momentum of the photoelectrons that are ejected when the sample is illuminated by an ultraviolet or soft x-ray light source, one can build up a high-resolution map of the 3D band structure of the material. There is, however, an implicit assumption in the technique, that the electrons, once emitted from the sample surface, do not interact with each other. However, progress in shrinking the size of the beam spot, in so-called nano-ARPES experiments, means that a large number of electrons are simultaneously excited from the same location, which may mutually repel due to Coulomb interactions. This so called “vacuum space charge” effect can lead to “blurring” of the measured energy of the electrons.
Understanding the limitations that vacuum space charge effect introduces, and strategies to mitigate the effect, will be crucial for both current nano-ARPES experiments at the I05 beamline, and for future development of the nano-ARPES technique at Diamond Light Source.
The project has a computational and an experimental side.
First, using established empirical models and literature references, you will assess the possibility of vacuum space charge effects, performing relatively simple numerical calculations of the current bunch structure and optical schemes at the I05 beamline.
Second, you will assist in the development of a new tool for characterising the beam spot, a “knife edge” with electrical contacts. This will allow us to measure the spot size. It will be gold-coated to give a strong signal in photoemission, while the drain current can be converted into the number of electrons emitted per bunch. With this set up, we will be able to directly test the regime of space charge that we reach in the current nano-ARPES set-up.
As part of the project, you will plan and perform experiments in at least one day of commissioning time using the beam at the I05 nano-ARPES beamline, to obtain a systematic data set. After this, you will analyse the data and produce a report. Your work will be influential in quantifying the effect of vacuum space charge, for the benefit of future users of the I05 beamline.
(Unfortunately, students of disciplines other than Physics are unlikely to have studied the combination of both optics and electromagnetism that is desired for this project)
Please apply via our online application portal. The vacancy that you are applying for is the "Summer Placements 2022" listing, you will then have the opportunity to select up to three projects to apply for. This project's reference is 22009SP.
Applications are now closed with interviews scheduled for 7, 8, 9 and 10 February 2022.
If you are disabled and would like to be considered under the Guaranteed Interview Scheme, please let us know via the online application process.
Please note that this role does not meet the required skill level for a Skilled Worker visa and therefore we would be unable to sponsor individuals due to the current UK Home Office immigration rules. To be appointed to the role, candidates will need to have the right to work in the UK without sponsorship from us.
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