# Dr James Robinson

## Tokamak transport and strong, structured flows

Working with Dr Ben McMillan, my current project is adding strong flows into the global gyrokinetic PIC code NEMORB, the electromagnetic version of ORB5. Based on the Hahm formalism of the gyrokinetic Vlasov and Poisson equations in the presence of equilibrium ExB velocity $$u_E \sim v_{Ti}$$.

PhD Thesis: The Geodesic Acoustic Mode in strongly-shaped tight aspect ratio tokamaks
Supervisor: Dr Bogdan Hnat

Comparison between experimental measurements from the spherical tokamak MAST, two-fluid simulation data and theory of the Geodesic Acoustic Mode (GAM) in tight aspect ratio strongly shaped tokamak plasmas. The first identification of a strong ≈ 10kHz mode detected in both potential and density fluctuations of the edge plasma in MAST using a reciprocating probe is given. The mode is radially localised, with outer limit ≈2cm inside the separatrix, and is affected on application of resonant magnetic perturbations (RMP) generated by external coils. A shift in frequency with plasma rotation is found, and a suppression of the mode is observed above a certain threshold. Non-linear coupling to high wave number turbulence is evident, and an increase in power of turbulence fluctuations is seen after suppression. These observations are then interpreted in the context of known low frequency plasma modes present in the toroidal configuration. The supposition that the observed mode is a geodesic acoustic mode is considered and motivated by experimental observations and numerical simulations.

Publications:

• Robinson, J. R., B. Hnat, A. Thyagaraja, K. G. McClements, P. J. Knight, and A. Kirk. Global Two-fluid Simulations of Geodesic Acoustic Modes in Strongly Shaped Tight Aspect Ratio Tokamak Plasmas. Phys. Plasmas 20 052302 (2013)
• J R Robinson, B Hnat, P Dura, A Kirk, P Tamain and the MAST Team, Interaction between a low-frequency electrostatic mode and resonant magnetic perturbations in MAST, Plasma Phys. Control. Fusion 54 105007 (2012)
• P. D. Dura, B. Hnat, J. Robinson, and R. O. Dendy, Vorticity scaling and intermittency in drift-interchange plasma turbulence, Phys. Plasmas 19, 092301 (2012)
• J. L. A. Fordham, H. Kawakami, R. M. Michel, R. Much and J. R. Robinson , High time-resolution spectroscopic imaging using intensified CCD detectors Mon. Not. R. Astron. Soc. 319, 414-418 (2000)

Background:

After a pre-University year at IBM writing some multi-threaded network tools in C, I completed my Physics BSc from UCL. I then worked in general IT support for a while before briefly returning to UCL to work on improving the photocathode sensitivity in a microchannel plate intensified CCD camera. Following this I moved to an independent TV/Film Post Production company looking after high end SGI/Irix and Linux based Autodesk visual effects systems such as Flame and Maya, and the associated render farm, 10Gb network and SAN storage infrastructure. In returning to science, I first studied for the renowned MSc "Physics and Technology of Nuclear Reactors" at the University of Birmingham, before going on to get my PhD from the University of Warwick

### Contact Details

Centre for Fusion, Space & Astrophysics
Department of Physics
University of Warwick
Coventry
CV4 7AL
United Kingdom

telephone:
+44(0)2476 150946

fax:
+44 (0) 24 76150897

email:
james.robinson@warwick.ac.uk

office:
PS103

Profiles: