Showing 1 - 10 of 22 Journals Results
2020
UKAEA-CCFE-PR(20)65
L C Appel S Kwak F Militello J Svensson
A novel approach using Bayesian inference has been implemented to interpret the filamentary dynamics measured by a Langmuir probe fixed to a reciprocating assembly on MAST. The model describes the system as a superposition of time-displaced filaments and a fixed background component. Each filament is parameterised in terms of a characteristic rise …
Preprint Published2017
CCFE-PR(17)68
L. C. Appel I. Lupelli JET Contributors
In many tokamaks ferromagnetic material, usually referred to as an iron-core, is present in order to improve the magnetic coupling between the solenoid and the plasma. The presence of the iron core in proximity to the plasma changes the magnetic topology with consequent e ects on the magnetic field structure and the plasma boundary. This paper cons…
Preprint Purchase2015
CCFE-PR(17)40
I. Lupelli D.G.Muir L. Appel R. Akers M. Carr P. Abreu
Journal publications, as the final product of research activity, are the result of an extensive complex modelling and data analysis effort. It is of paramount importance, therefore, to capture the origins and derivation of the published data in order to achieve high levels of scientific reproducibility, transparency, internal and external data reus…
Preprint Published2013
H. Meyer I.G. Abel R.J. Akers A. Allan S.Y. Allan L.C. Appel O. Asunta M. Barnes N.C. Barratt Et Al
New diagnostic, modelling and plant capability on the Mega Ampere Spherical Tokamak (MAST) have delivered important results in key areas for ITER/DEMO and the upcoming MAST Upgrade, a step towards future ST devices on the path to fusion currently under procurement. Micro-stability analysis of the pedestal highlights the potential roles of micro-tea…
Published2012
G. T. Von Nessi M. J. Hole J. Svensson L. Appel
In this paper, current profiles for plasma discharges on the mega-ampere spherical tokamak are directly calculated from pickup coil, flux loop, and motional-Stark effect observations via methods based in the statistical theory of Bayesian analysis. By representing toroidal plasma current as a series of axisymmetric current beams with rectangular cr…
Published2010
M. J. Hole G. Von Nessi D. Pretty J. Howard B. Blackwell J. Svensson L. C. Appel
Recently, Bayesian probability theory has been used at a number of experiments to fold uncertainties and interdependencies in the diagnostic data and forward models, together with prior knowledge of the state of the plasma, to increase accuracy of inferred physics variables. A new probabilistic framework, MINERVA, based on Bayesian graphical models…
Published2009
M. J. Hole L. C. Appel R. Martin
Over the past two decades, the increase in neutral-beam heating and particle production in magnetically confined fusion plasmas has led to an increase in energetic particle driven mode activity, much of which has an electromagnetic signature which can be detected by the use of external Mirnov coils. Typically, the frequency and spatial wave number …
Published2009
M.J. Hole L.C Appel
Recent observations of magnetic fluctuation activity in the Mega Ampere Spherical Tokamak (MAST) reveal the presence of plasmas with bands of both low and high frequency magnetic fluctuations. Such plasmas exhibit a spectrum of low frequency modes with adjacent toroidal mode numbers, for which the measured frequency is near the Doppler shifted rota…
Published2009
H Meyer R J Akers F Alladio L C Appel K B Axon N Ben Ayed P Boerner R J Buttery P G Carolan D Ciric C D Challis I T Chapman Et Al
Several improvements to the MAST plant and diagnostics have facilitated new studies advancing the physics basis for ITER and DEMO, as well as for future spherical tokamaks. Using the increased heating capabilities PNBI ≤ 3.8 MWH-mode at Ip = 1.2 MA was accessed showing that the energy confinement on MAST scales more weakly with Ip and more strong…
Published2008