[Neutron] An unusual Doctoral opportunity

Don Paul phrje at live.warwick.ac.uk
Wed Mar 8 18:25:50 CET 2017

Project Description


*This project is to develop the unique capabilities offered by the 
RIKEN-RAL muon facility in Oxfordshire, UK. 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.*

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 and there sensitivity to light 
atoms. These high energy muonic X-rays are emitted from the bulk of the 
samples without significant photon self-absorption. 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). 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. The X-rays that are emitted can be simply detected by a 
semiconductor detector. We have recently published a proof of principle 
article in the MicroAnalytical Journal describing some of our recent 
work . Over the years there has been sporadic use of negative muons as 
an elemental analysis tool, and a wide-ranging number of materials have 
been investigated, including Japanese coins, spinal columns, pig fat and 
dog’s blood, tissue analysis and ancient Chinese mirrors . Very 
recently, the negative muons at J-PARC have been used to ex­amine 
extra-terrestrial material, *Allende* and *Martinsite* meteorites .

*Project aims*

The main part of this project will be todevelop data analysis for 
negative muon experiments. This will include GEANT4 simula­tions on muon 
implantation depth. Delivering a simplified data reduction and 
correction software, data visualisation within MANTID (includ­ing 
importing the shape of the sample and transforming the acquired data 
from a series of measurements at different orientations relative to the 
incident beam into a 3D voxel mapping). This will also include 
incorporating GEANT4 simulations. Finally, but by no means least, we 
need to determine the limitations of the technique. In order to aid the 
development of the technique, three science themes will be investigated: 
cultural heritage, energy materials and engineering;

>Ancient coins have been obtained from the University of Oxford as part 
of a program of research to study the circula­tion of gold around the 
Roman Empire. Here, the question is to determine in a completely 
non-destructive way the com­position of each coin, which can be 
difficult to achieve with other more surface-sensitive techniques 
because of surface enrichment/deterioration due to either natural 
corrosion processes or deliberate deception. This experiment will form 
part of a round-robin set of measurements using several of the more 
conventional techniques for elemental analysis.

> Lithium battery  materials are important for our current need for power and 
portability, but as Samsung have recently discovered, they do have 
limitations. Elemental analysis can shed light onto location of Li in 
real life, making this a potentially highly valuable avenue of research.

>A recent test experiment has shown that carbon can be measured within 
iron. By mapping samples in 3D we intend to investigate welds to 
understand the role and distribution of light elements throughout welds 
and a correlation between their presence and their stress-strain map.

This is a unique opportunity to start a project at the birth of the 
technique and a suitable student for this would be a Physical 
scientistwith wide range of interests beyond physics. They would also 
have an interest in experimental measurements and the development of 
software for data analysis.

This is a new, exciting and fast moving field and an ideal project for a 
strong and enthusiastic student with interests which extend beyond 
physics. The student should have interests in the design of experimental 
measurements and the development of data analysis software. The student 
will be enrolled on the Materials Physics Doctorate scheme . This gives 
access to a tailored research degree to help you exploit our own 
outstanding materials growth, fabrication, characterisation and 
computational capabilities along with those at central facilities. A 
broad education in Materials Physics is provided through dedicated 
modules under the Midlands Physics Alliance Graduate School, and 
external courses.

Funding Notes

A full 3.5 year studentship for UK students (fees and maintenance) is 
available, and wouldalso be available to outstanding EU applicants. This 
studentship is funded jointly by the University of Warwick and the STFC 
<http://www.isis.stfc.ac.uk/groups/muons/muons3385.html> ISIS Facility 
at Rutherford Appleton Laboratory (RAL) and would involve an initial 
year at Warwick followed by two years at ISIS. Candidates should hold or 
expect to hold a 1st (or high 2.1) in Physics or related subject area.

The Physics department is proud to be an IOP Juno Champion and a winner 
of an Athena Swan Silver Award, reflecting our commitment to equal 
opportunity and to fostering an environment in which all can excel.

For further information please contact Professor Don Paul at 
phrje at live.warwick.ac.uk <mailto:phrje at live.warwick.ac.uk> or Dr Adrian 
Hillier at adrian.hillier at stfc.ac.uk <mailto:adrian.hillier at stfc.ac.uk>.

Professor Don Paul Superconductivity & Magnetism Group University of 
Warwick Coventry CV4 7AL. tel: 024 76 523603 email: phrje at warwick.ac.uk
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