ISIS-21 ISIS Summer Student for the development of elemental analysis using muons
04 Feb 2019
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This project is to develop the unique capabilities offered by the RIKEN-RAL muon facility. Implanting negative muons results in X-ray emission which is element dependent and therefore the energy and intensity of such peaks can result in the determination of the elemental composition. These X-rays have large energies (~MeV) therefore probing beneath the surface is entirely possible, making this a novel and potentially powerful non-destructive probe. Alongside the instrument development we propose a broad science program, from cultural heritage to bio-materials to energy related materials.

ISIS is a primary high-flux source of pulsed muon beams and the provision of such beams is an important contribution to the character of the facility. However, at ISIS (RIKEN-RAL) a high flux of  negative muons is also available which opens up the possibility of answering different experimental questions of interest for a new type of user with different and interesting sci­entific questions [1]. Figure 1 presents a cartoon schematic of the negative muon absorption and X-ray emission process. Negative muons can be considered as 'heavy electrons' and replace an electron in the outer shell of an atom, then travel to near the nucleus through the modified energy states of the atom. Each transition on this path produces an X-ray which is characteristic of the atom which absorbed the muon, hence allowing this spectrum to reflect the atomic species. The sensitivity of this technique is such that even light atoms can be detected (such an experiment is sensitive to all elements with atomic masses greater than Li). Furthermore, this technique can be used as a depth analysis tool, since by varying the momentum of the incident muon beam it is possible to change the depth of implantation for the negative muon [2].

 Currently, elemental analysis commonly uses X-ray and electron beams which are good for measuring surfaces, how­ever a significant advantage of muonic X-rays over those of electronic X-rays is their higher energy (0.01-6 MeV) due to the mass of the muon. These high energy muonic X-rays are emitted from the bulk of the samples without significant photon self-absorption. The penetration depth of the muons can be varied by controlling the muon momentum, providing data from a thin slice of sample at a given depth. This can be over a centimetre in iron, silver and gold or over 4 cm in less dense materials such as carbon.

We would like to employ a summer student to develop new data analysis techniques that can be used to speed up the identification of the elements from the X-ray spectrum.

The student will get experience in programming (Python), version control and new scientific techniques.  This work is a growing field of interest and would allow a student to see how scientific ideas are developed.


Supervisor: Anthony Lim, anthony.lim@stfc.ac.uk

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