Nuclear fusion
Nuclear fusion is the process that powers the sun, and it has the potential to provide us with a way of obtaining cheap, clean energy, but there are still scientific barriers to be overcome before commercial fusion power plants can be built. The fuel that will be used is a 50:50 mix of deuterium and tritium (isotopes of hydrogen). In order for fusion reactions to occur, the fuel has to be at such a high temperature that it forms a plasma. Plasma is the fourth state of matter, in which atoms are ionised to create a gas of positively and negatively charged particles. This charged gas then has to be confined - one of the main problems we face when trying to sustain a fusion reaction.
There are two ways of confining the plasma - inertially and magnetically. The largest inertial confinement fusion (ICF) experiment is the National Ignition Facility in the USA. My research, however, is concerned with magnetically confined fusion, or MCF. The most common type of machine is the tokamak, a doughnut-shaped vacuum vessel with specially-shaped magnetic fields to confine the plasma. The largest tokamak currently in operation is the Joint European Torus, JET, at the Culham Centre for Fusion Energy in the UK. A much larger tokamak, ITER, is being constructed in the south of France; a huge collaborative project between China, the EU, India, Japan, Korea, Russia and the USA.
PhD research
I am an experimental physicist, and have primarily worked on the York Linear Plasma Device (YLPD, pictured left and described by Rusbridge et al. (2000)) that is housed in the York Plasma Institute labs. This machine can sustain a continuously streaming, magnetically confined column (a few centimetres in diameter) of hydrogen or helium plasma, which is ideal for running experiments concerning the basic plasma physics that applies to tokamak fusion reactors (e.g. JET or ITER).
"Applications of linear plasma device studies to the improvement of power injection and handling in tokamaks" - see my thesis here
-2
-2
The links between this 1.5 m metre linear machine and the ~20 m high toroidal tokamaks arise because the plasma parameters (e.g. density and pressure) obtained in the YLPD are similar to those observed in the exhaust region, known as the divertor, of a tokamak. This means that the physics studied in the much simpler linear geometry can be applied to the complicated toroidal geometry of a divertor plasma. The main advantage of a linear machine is that diagnostic access is more straightforward, making it much easier to make measurements.
My thesis focused on the phenomenon of detachment. A puff of neutral gas (usually hydrogen) causes the plasma to start recombining before it comes into contact with a surface - the end plate in the linear device, and the divertor plates in a tokamak. There are two advantages to this:
​
-
The ion flux to the surface is lessened, as the charged particles recombine before they reach the surface. This reduces the amount of damage done to the plates, extending component lifetimes.
-
The energy flux to the surface is lessened, as some is radiated away in the recombination interactions. This reduces the amount of heat damage done to the plates, again extending the component lifetimes.
​
The exhaust power flux to the divertor plates in ITER is estimated to be at least 15 MW m (Alvarez et al. 2011), and even larger for DEMO, whereas the limiting flux required for a reasonable divertor plate lifetime is around 5 MW m . It is therefore necessary to utilise a process such as detachment in order to reduce the power flux to a viable level, and so research into detachment processes is required.
I have built on previous work on the YLPD, investigating possible links between detachment processes and instabilities in the plasma column. I have also worked on a Langmuir probe array to increase the time resolution of plasma parameter measurements.
In the summer of 2015, I spent eight weeks at the Australian National University, working with Cormac Corr on MAGPIE, the linear plasma device there. This project has been funded by the Fusion CDT as an opportunity to undertake collaborative work that otherwise would not be feasible. I studied the negative ion population in MAGPIE using laser photodetachment as a diagnostic. I returned for six weeks in the sumer of 2016 to continue the collaboration, extending the scope to look for evidence of detachment in MAGPIE.
Conferences
October 2017: 59th APS Division of Plasma Physics meeting
​
July 2017: 44th EPS Conference on Plasma Physics
Presented a poster. My contribution to the conference proceedings can be found here.
​
November 2016: 58th APS Division of Plasma Physics meeting
Presented a poster.
​
July 2016: 43rd EPS Conference on Plasma Physics
Received a PPCF/EPS/IUPAP prize for my poster. My contribution to the conference proceedings can be found here.
​
May 2016: 43rd IOP Plasma Physics Group Spring Conference
Received an EPL Presentation Award for my poster.
​
November 2015: FuseNet PhD Event
Presented a poster.
​
April 2014: 41st IOP Plasma Physics Group Spring Conference
Past projects
2013: MSci project, University of Cambridge
"Crystal growth and X-ray characterisation of rare-earth based cuprate superconductors"
Supervisor: Suchitra Sebastian
The aim of this four-month project was to grow and subsequently study (using a SQUID magnetometer) crystals of a high-temperature cuprate superconductor. I investigated the effects of annealing the crystals in oxygen, and succeeded in obtaining some superconducting crystals, although further improvements to the method would have been required to increase the superconducting transition temperature to the maximum (~90K). I presented my results through a written report and oral examination.
2012: Summer Undergraduate Research Experience, University of Leicester
"Further Swift follow-up of unidentified X-ray sources in the XMM-Newton Slew Survey"
Supervisor: Rhaana Starling
I spent six weeks analysing data from the XMM-Newton Slew Survey as part of the University of Leicester's SURE scheme. I fitted X-ray and optical spectra in order to identify astronomical X-ray sources, presenting my work orally to the summer student cohort as well as through a written report.
2011: Summer Undergraduate Research Fellow, California Institute of Technology
"Spectroscopic analysis of a plasma for an astrophysical jet experiment"
Supervisor: Paul Bellan
After obtaining a place on the SURF programme at Caltech, I spent ten weeks studying the properties of a plasma source, using spectroscopic techniques and various plasma equilibrium theories, in order to successfully improve the ionisation fraction of the plasma produced. I presented a poster to the summer student cohort, as well as producing a written report.