André JAUN
 
Associate Professor
NADA
Royal Institute of Technology
Lindstedtsvägen 3
SE-100 44 Stockholm



Tel:  +46 (8) 7908130 (direct)
        +46 (8) 7908176 (secr)
        +46 (70) 7971879 (mobile)
Fax:  +46 (8) 7900930
Email: jaun@nada.kth se
Web: http://www.nada.kth.se/~jaun


Welcome

Wish you a very warm welcome on my home page and since that's its purpose, let me introduce myself as a resonably young Swiss scientist, mountaineer, traveler and would like to be more of a sailor.

I am currently working as an associate professor in the numerical analysis department of the Royal Institute of Technology in Stockholm and, in the limited time granted to the faculty for private entreprises, pursue the development of the educational website www.lifelong-learners.com offering courses in financial engineering and numerical methods in general.

My interests span a number of topics in natural-, financial- and social sciences, with numerical simulation being a common denominator for my research in applied mathematics and physics. Since the beginning of my scientific career, I have been studying the toroidal confinement of plasmas, aiming at the development of a new clean and unlimited source of energy based on the energy released by the fusion of hydrogen isotopes into helium--in a similar way as it occurs inside the stars. Another topic where I have been active, is the development of distance-learning methods and more generally pedagogical tools for the numerical simulation in science and engineering.

In my spare time, I like to go out with friends, listen to fine Jazz and why not, dance some salsa. With my constant professional traveling, the climbing, sailing and volleyball I used to practice almost every day at home in Switzerland have been reduced to activities for holidays. During 1997, I took the opportunity to climb the second highest peak in the former USSR, the Pic Lenina (7134m, Kyrghiztan). More recently in 2001, I reached an easier peak in the Andes called Huayana Potosi (6088m, Bolivia).


Research

Summary
(last update: Jan 2004)

The work carried out for research generally deals with the modeling and the numerical simulation of in physical sciences and engineering. Waves, diffusion, convection and non-linear interactions are phenomena encountered in applications as different as telecomunications, biology, finance and fusion energy research. They can very nicely be described using differential equations, but only in the very simplest (and often limiting) approximations is it generally possible to find solutions in terms of analytic functions. Numerical calculations are then needed and obtained from computer programs built around robust methods to ensure that the computed solutions are also meaningfull.

The progress in the understanding of a basic phenomenon often starts from an intuition of what may be the basic ingredients. Analytic skills are then necessary to formulate approxiations leading to a mathematical model often in terms of integral / differential equations. Using appropriate numerical methods to exploit the power of digital computers, the solutions obtained need always first to be checked against limiting cases and the approximations validated against measurements before it may be possible to make a leap forward in the undestanding and to extrapolate into new regimes.

In fusion energy research, this procedure is routinely applied for the propagation of waves in toroidal plasmas. D(H) mode-conversion in the DIII-D tokamak KAE in the JET tokamak Gyrokinetic effects (where the statistical distribution of charged particles and their finite Larmor excursion around magnetic field lines come into play) are studied on the world largest experiments (such as the JET, DIII-D, TCV tokamaks) in order to design and predict the behaviour of future reactors (such as ITER). Our contributions focus on the stability of global eigenmodes of the toroidal cavity and the propagation / absorption of waves ranging from the ion-cyclotron frequency down to nearly zero.
  Increasingly sophisticated models have been formulated for the interaction between electromagnetic waves and the plasma particles; they lead to a set of coupled integro- / differential equations that have been implemented in the PENN code. The large linear system resulting from a discretization with bi-cubic finite elements can just about be solved with the largest super-computers using iterative Krylov space methods. This unique capability of computing global electromagnetic wavefields with gyrokinetic models for the plasma explains why the PENN code is at present the state of the art for studying Alfvén eigenmodes (AE) and is being used to revisit a number of predictions for macro-instabilities that have up to now been modeled with a simpler magneto-hydrodynamic (MHD) description of the plasma.
Alfvén Eigenmode prediction for ITER   Original results have been obtained showing how the linear mode-conversion between fast and slow wave is an interesting phenomenon that often plays a crucial role in tokamak physics. Slow wavefields have for the first time been numerically resolved, with localized wavefield structures predicted in the ion-cyclotron frequency range that remain to be identified experimentally. Drift- / kinetic Alfvén eigenmodes (D-/KAE) have been predicted, and compared with wavefield and damping measurements from the JET (Oxford, UK) and DIII-D (San Diego, USA) tokamaks. (If your computer has some sound support, take a minute to listen to a plasma with / without macro-instabilities in JET. The sound files are produced by downsampling the magnetic probe measurements. Alfvén instabilities appear as violin like sounds bursts at high pitch, but are absent in the world record discharge where 16 MW of fusion power were produced. Many other modes do however affect the plasma while it reaches thermonuclear conditions. Courtesy of Prof. A. Fasoli, MIT).
The quantitative agreement achieved between the numerical predictions and the damping rate measured in JET allowed us to identify a key stabilizing mechanism associated with the plasma shape (e.g. the cusp at the bottom), drawing on our calculations made in Sweden to predict the stability of ITER -- the future International Thermonuclear Experimental Reactor.
 
 

Slides from selected talks/seminars
(last update: May 2007)


Projects proposed to students
(last update: Jan 2005)

Reprints of selected publications
(last update: Aug 2007)


 

International collaborations
(last update: Mar 2002)



Teaching

(last update: Jan 2004)

Introduction to Numerical Methods (KTH 02-04)
Second year undergraduate introductory course for students in electrical engineering.

Financial Modeling: Options, Swaptions & Derivatives (KTH 02-04)
Graduate level course for students from KTH and the Swedish Netuniversity, can be studied entirely at a distance.
Numerical Methods for Partial-Differential Equations (KTH 97-04)
Graduate level course for students from KTH, the Swedish Netuniversity and EPFL/Lausanne can be studied entirely at a distance.
Introduction to Plasma Physics with Applications (CTH 99-01)
Advanced undergraduate level course taught to physics and electrical engineering students at Chalmers.
Distance-learning for everyone distributed by www.lifelong-learners.com (since 2000).
Courses are organised on a private basis for companies and students from outside the Swedish academic system, as part of the commercial activity granted to the members of the faculty.


Hobbies

(last update: March 2002)

Mountaineering.

Camp IV on the way to the summit (6400m) Mountaineering has been one of my favourite hobbies for a long time. In the good old days, I used to spend up to 60 days skiing, rock+ice climbing every year... This is how I got enrolled as an avalanche specialist in the Swiss army. Today, I limit myself to a couple of excursions every year. Double-click on the picture to visit the album from the expeditions to Pic Lenina (7134m, Kyrghistan), Mt Whitney (4460m, USA) we did together with my friend François and a more recent climb to Huayana Potosi (6088m, Bolivia).


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