My photo of the inside of a Doctor X Photocathode - this whole space is around 1cm in diamaeter.
The fine details:
Looking upstream of a 100 kilovolt photocathode electron source from Doctor X (R&D company based in the Netherlands) with misaligned UV laser source that also outputs both green and UV light.
Inside this ultra-high vacuum chamber, pulses of ultraviolet laser light are used to create an electron beam. The laser enters from the right, reflects from a mirror (right structure), and strikes a polished copper disc at the centre of the image. The absorbed light releases electrons through the photoelectric effect, a phenomenon in which light can eject electrons from a material.
A 100 kilovolt electric potential then accelerates the electrons toward the camera. Electron sources such as this are the starting point for many linac accelerator used for medical imaging, radiotherapy and particle accelerators like ANSTO's Australian Synchrotron.
The photoelectric effect was one of the key discoveries that earned Albert Einstein the 1921 Nobel Prize in Physics and today forms the basis of many modern technologies. For copper photocathodes, ultraviolet (UV) light has a higher quantum efficiency than visible light, meaning a larger fraction of photons successfully liberate electrons from the surface.
A collaboration between ANSTO and the University of Melbourne's XLAB to develop the technology needed for the next generation of particle accelerators.