Orbit topology in conventional stellarators in the presence of electric fields
Orbits are considered in conventional stellarators (i.e. with
helical coils) using Boozer coordinates. The Advanced Toroidal Facility
(ATF) in Oak Ridge, Tennessee, will be used as an example to study the
effects of its configurational flexibility on orbit topology. It is
shown that the symplectic integration technique yields superior results
for single particle orbits. These orbits will be compared with
predictions using the J* invariant. J* conservation
allows examination and understanding of the global stellarator
topology, both with and without radial electric fields.
Recent Advances in Stellarator Development
Large stellarator research programs are being pursued in Europe and Japan (>$1 billion in new facilities). These programs are important because the similarities and differences between stellarators and tokamaks can be used both to improve our understanding of toroidal confinement and to develop an improved reactor concept. Stellarators have performance similar to that of comparable tokamaks. New large stellarator experiments under construction with superconducting coils will have parameters comparable to those of present tokamaks. Significant experimental and theoretical progress has been made in understanding transport, finite-beta behavior in three-dimensional toroidal geometry, and concept improvement. Ideas to further improve the stellarator concept will be tested in new experiments. Recent studies have improved the stellarator reactor concept and shown that stellarators can be competitive with tokamaks as reactors.
The U.S. stellarator community has written a White Paper that describes the US Compact Stellarator Program:
A talk was given at the March 2005 DOE Budget Planning Meeting on the US Compact
Stellarator Program that discussed the program logic for the U.S. compact stellarator
program, the experimental facilities and programs, and the contributions that
the program makes to the Fusion Energy Sciences Advisory Committee list of
priority questions for the U.S. fusion program.
Community response to FEAC Panel
In January 1996, the Fusion Energy Advisory Committee (FEAC)
recommended
to DOE that a review of Alternative Concepts (including stellarators)
be
carried out as part of making the transition to a Fusion Energy
Sciences
Program. This review was held on April 23 and the attached document
gives
the U.S. stellarator community response to the questions raised by the
review panel, including the world-wide status of research and
achievements
on stellarators, the appropiate level of research, and the potential
inpact
of U.S. stellarator research.
U.S. Stellarator Proof of Principle Program
An integrated program with mutually supporting elements is proposed
to develop the physics basis for high-beta good-confinement
stellarators with low plasma aspect ratio that could lead to more
compact stellarator reactors. The program consists of: (1) a new
"proof-of-principle" facility, the National Compact Stellarator
Experiment (NCSX); (2) a new concept exploration experiment, the
Quasi-Omnigeneous Stellarator (QOS); (3) the existing Helically
Symmetric Experiment and an upgrade to the Compact Auburn Torsatron;
(4) stellarator theory focusing on concept optimization and key
stellarator physics issues; (5) collaboration with the international
stellarator program in specific areas; and (6) system studies to guide
concept optimization tradeoffs. The two new elements of the
proposed program are based on promising transport optimization
strategies for compact stellarators: quasiaxisymmetry (NCSX) and
quasiomnigeneity (QOS); each has distinct complementary advantages
(physics, reactor embodiment). Determination of the optimum
approach to pursue is a goal of the US stellarator program.
U.S. Stellarator Program — Opportunities for Concept Improvement (July 1999)
The U.S. stellarator community presented a "White Paper" at the 2-week July 1999 Fusion Summer Study at Snowmass, Colorado outlining a proposed increased U.S. stellarator program. The White Paper discusses: (1) advanced toroidal confinement approaches; (2) compact stellarators; (3) stellarator research opportunities; (4) the proposed National Compact Stellarator Experiment (NCSX); (5) the proposed Quasi-Omnigeneous Stellarator (QOS); (6) the existing Helically Symmetric Experiment (HSX); (7) an upgrade to the Compact Auburn Torsatron (CAT-U); (8) international collaboration; and (9) system studies.
Stellarator reactor design lecture presentations
Horst Wobig held a series of tutorial seminars on the Stellarator Reactor in Greifswald. Materials presented during
the series are available via the W7 Seminar home page
(select talks 2006 in the right-hand menu):
http://w7x.info/w7seminar/w7is_w7sem.html
To access the site, login as user w7as_team, with password
stella.
Note that you will find the transparencies, the software for
coil optimization, and more materials on the stellarator
reactor also via the home page of Stellarator System Studies:
http://w7x.info/proj_sss/w7is_proj_sss.html
CIEMAT has undertaken the compilation of a database containing the proceedings of past Stellarator Workshops, since proceedings for many past events are not available via the Internet. Currently this page (which is still under construction) is available at
http://www-fusion.ciemat.es/SW2005/previous.shtml