Features of formation, confinement and stability of the field reversed configuration
The field reversed configuration (FRC) is an innovative confinement system that offers a unique fusion reactor potential because of its compact and simple geometry, transport properties, and high plasma beta. Brief review of the simple compact system with natural advantages and reactor potential is...
Збережено в:
| Дата: | 2002 |
|---|---|
| Автор: | |
| Формат: | Стаття |
| Мова: | English |
| Опубліковано: |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2002
|
| Назва видання: | Вопросы атомной науки и техники |
| Теми: | |
| Онлайн доступ: | http://dspace.nbuv.gov.ua/handle/123456789/80255 |
| Теги: |
Додати тег
Немає тегів, Будьте першим, хто поставить тег для цього запису!
|
| Назва журналу: | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| Цитувати: | Features of formation, confinement and stability of the field reversed configuration / S.V. Ryzhkov // Вопросы атомной науки и техники. — 2002. — № 4. — С. 73-75. — Бібліогр.: 27 назв. — англ. |
Репозитарії
Digital Library of Periodicals of National Academy of Sciences of Ukraine| id |
irk-123456789-80255 |
|---|---|
| record_format |
dspace |
| spelling |
irk-123456789-802552015-04-15T03:02:09Z Features of formation, confinement and stability of the field reversed configuration Ryzhkov, S.V. Magnetic confinement The field reversed configuration (FRC) is an innovative confinement system that offers a unique fusion reactor potential because of its compact and simple geometry, transport properties, and high plasma beta. Brief review of the simple compact system with natural advantages and reactor potential is given. Theoretical and experimental results in a FRC plasma study are discussed. Last results in compact toroids research are presented which advance the understanding of the formation and stability properties of the field reversed configuration. Confinement properties of oblate (Elongation<1) and prolate (E>2) FRCs (elliptic shape and racetrack) are discussed. Numerical study is overviewed. 2002 Article Features of formation, confinement and stability of the field reversed configuration / S.V. Ryzhkov // Вопросы атомной науки и техники. — 2002. — № 4. — С. 73-75. — Бібліогр.: 27 назв. — англ. 1562-6016 PACS: 52.55.Lf http://dspace.nbuv.gov.ua/handle/123456789/80255 en Вопросы атомной науки и техники Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| institution |
Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| collection |
DSpace DC |
| language |
English |
| topic |
Magnetic confinement Magnetic confinement |
| spellingShingle |
Magnetic confinement Magnetic confinement Ryzhkov, S.V. Features of formation, confinement and stability of the field reversed configuration Вопросы атомной науки и техники |
| description |
The field reversed configuration (FRC) is an innovative confinement system that offers a unique fusion reactor potential because of its compact and simple geometry, transport properties, and high plasma beta. Brief review of the simple compact system with natural advantages and reactor potential is given. Theoretical and experimental results in a FRC plasma study are discussed. Last results in compact toroids research are presented which advance the understanding of the formation and stability properties of the field reversed configuration. Confinement properties of oblate (Elongation<1) and prolate (E>2) FRCs (elliptic shape and racetrack) are discussed. Numerical study is overviewed. |
| format |
Article |
| author |
Ryzhkov, S.V. |
| author_facet |
Ryzhkov, S.V. |
| author_sort |
Ryzhkov, S.V. |
| title |
Features of formation, confinement and stability of the field reversed configuration |
| title_short |
Features of formation, confinement and stability of the field reversed configuration |
| title_full |
Features of formation, confinement and stability of the field reversed configuration |
| title_fullStr |
Features of formation, confinement and stability of the field reversed configuration |
| title_full_unstemmed |
Features of formation, confinement and stability of the field reversed configuration |
| title_sort |
features of formation, confinement and stability of the field reversed configuration |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| publishDate |
2002 |
| topic_facet |
Magnetic confinement |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/80255 |
| citation_txt |
Features of formation, confinement and stability of the field reversed configuration / S.V. Ryzhkov // Вопросы атомной науки и техники. — 2002. — № 4. — С. 73-75. — Бібліогр.: 27 назв. — англ. |
| series |
Вопросы атомной науки и техники |
| work_keys_str_mv |
AT ryzhkovsv featuresofformationconfinementandstabilityofthefieldreversedconfiguration |
| first_indexed |
2025-07-06T04:13:24Z |
| last_indexed |
2025-07-06T04:13:24Z |
| _version_ |
1836869437337108480 |
| fulltext |
FEATURES OF FORMATION, CONFINEMENT AND STABILITY OF THE
FIELD REVERSED CONFIGURATION
Sergei V. Ryzhkov
Bauman Moscow State Technical University
2nd Baumanskaya Street, 5, Moscow, 105005 Phone: (095) 263-65-70
E-mail: ryzhkov@power.bmstu.ru
The field reversed configuration (FRC) is an innovative confinement system that offers a unique fusion reactor potential
because of its compact and simple geometry, transport properties, and high plasma beta. Brief review of the simple
compact system with natural advantages and reactor potential is given. Theoretical and experimental results in a FRC
plasma study are discussed. Last results in compact toroids research are presented which advance the understanding of
the formation and stability properties of the field reversed configuration. Confinement properties of oblate
(Elongation<1) and prolate (E>2) FRCs (elliptic shape and racetrack) are discussed. Numerical study is overviewed.
PACS: 52.55.Lf
INTRODUCTION
Field reversed configuration (FRC) is a system with
open and closed magnetic field lines separated by
separatrix that confines fuel ions and fusion products. The
axial field inside the reactor is reversed (as compared to
the externally applied magnetic field) by azimuthal
plasma current. This open system has toroidal
confinement, but the magnetic field has poloidal
component only. The FRC is being investigated as an
alternative to the tokamak, as a means of fueling a
tokamak and as a propulsion/power source for deep space
missions. Previous work [1-4] indicates that a FRC would
be a very attractive fusion power plant.
Notable experimental results include: improved
confinement and sustainment are carried out; rotating
magnetic field for current drive is applied; hotter, denser
and longer lived plasma is achieved and important
measurements are made. Impressive results in FRC
research plus good accessibility and low cost encourage
to say about the system of interest for an advanced fuel
fusion reactor as a future practical fusion power plant. But
fusion plasma parameters in FRC still no achieved. So, in
order to achieve them it is necessary to solve following
problems: decreasing of transport in plasma and
increasing of lifetime of magnetic configuration.
FORMATION
Thetа-pinch formation of FRCs has been used
successfully in early experiments. Viable FRC startup and
sustainment methods - RMF current drive and merging
spheromaks - are being examined recently.
It has been proposed that the externally applied
rotating magnetic field (RMF) will keep the reversed
configuration in steady state [5,6]. Recently, several
experiments have shown [e.g. 7] that RMF technique can
be applied to FRCs, both as a formation and a sustainment
mechanism. In addition, the application of RMF,
specifically to FRC, has been studied theoretically [8,9]
and numerically [10,11].
Parameter often used to characterize an RMF
equilibrium is ζ. This parameter represents the ratio of the
equilibrium line current density, to the maximum possible
synchronous line current density (corresponding to all the
electrons co-rotating with the RMF). Normally ζ is found
to be in the range 0.3<ζ<0.7. If ζ→1 the equilibrium will
be lost, because at that point the RMF starts to slow the
electrons down. However a ζ=1 plasma with full
penetration could be stably sustained if end mirrors were
used to continue the FRC length.
RMF current drive for startup and sustainment has
been recently tested on the Star Thrust Experiment (STX)
and Translation, Confinement, and Sustainment (TCS)
experiments (University of Washington). Significant
progress has been made in detaching the separatrix
completely from the wall by the flux conserver equipped
outside of the quartz chamber. It is shown that the quasi-
steady equilibria may be achieved by RMF. Future
research will extend these results towards realizing hotter,
denser and longer lived FRC by increasing the magnetic
flux by the RMF. Partial penetration (a little beyond the
field null) is observed in the present experiments. Inward
radial flow is predicted and measured. The role of inward
flows will be studied in near future.
Fig. 1. RMF antenna surrounding an FRC plasma
Recent experiments have scaled up rotating magnetic
field current drive in a fully ionized FRC plasma. This not
only demonstrates one solution to the FRC current drive
problem, but unexpectedly, RMF also quites internal
magnetic fluctuations and greatly increases energy and
particle confinement times. Improved confinement is also
observed by using end mirror coils and neutral beam
injection at Osaka University on the FIX (FRC Injection
eXperiment) facility [12].
Problems of Atomic Science and Technology. 2002. № 4. Series: Plasma Physics (7). P. 73-75 73
CONFINEMENT
See Ref. [13] for details of the remaining particle and
power balance equations. The electron power balance is
solved to obtained a self-consistent electron temperature.
The power losses are due to charged particle transport,
neutrons, synchrotron radiation and bremsstrahlung have
been estimated.
It is shown that anomalous transport in plasma
consisting of large orbit non-adiabatic ions and adiabatic
electrons can be avoided. Moreover, new model of radial
transfer is just beginning to be investigated [14]. A new
model of anomalous transport is developed especially for
FRC. The main features of this model are taking into
account complex field of drift waves propagating in
plasma and analysis of motion of the particles interacting
with field fluctuations.
Recent theoretical and experimental advances suggest
that stable, low-transport-rate FRCs may indeed exist.
Numerical studies show stabilization of tilt and shift
modes in oblate FRCs by a close fitting conducting shell.
However, oblate FRCs with no nearby wall are not
simultaneously stable to both tilt and shift. Furthermore,
hybrid simulations reveal near stabilization of the tilt by a
combination of spontaneously generated weak toroidal
magnetic fluxes and associated strong poloidal ion flows
in the absence of a nearby conducting boundary.
Axisymmetric resistive MHD simulations of spheromak
merging [15] have been performed and simulations using
the MHD field data was used to track particle orbits [16].
Recent 3D hybrid code (kinetic ions and fluid
electrons) calculations show a stabilization of the tilt in an
FRC correlated with self generation of oppositely directed
toroidal flux ropes. Simulations [17] have shown that
there is a reduction in the tilt mode growth rate in the
kinetic regime, but no absolute stabilization has been
found for s <1. Also two-dimensional evolution of the
reconnection has been studied.
Experimental studies in recent years have addressed
various FRC-related topics at Tokyo University, the TS-3
and 4 devices [18], in the TRAP [19] experiment, in the
Cornell Field Reversed Ion Ring Experiment, FIREX, on
FRX-L (Field Reversed eXperiment, Liner) at Los
Alamos National Laboratory in Magnetized Target Fusion
[20] implosion experiments, and the Swarthmore
Spheromak Experiment (SSX-FRC) [21].
Typical FRC parameters achieved in experiments are
summarized in Table 1.
Table 1
Separatrix radius, rs 0.03 - 0.40 m
Separatrix length, ls 0.2 - 1 m
Electron density, ne 0.005 - 5 x1021 m-3
Ion temperature, Ti 0.03 - 3 keV
Electron temperature, Te 0.03 - 0.5 keV
External B-field, Be 0.05 - 2 T
Average beta, <β> 75 - 95 %
Energy confinement time, τE 0.05 - 0.5 ms
STABILITY
The parameter most often used to characterize FRC
stability is s, the average number of gyroradii radially
between the 0-point (null field point) and the separatrix.
Power plants will require s > 20 and perhaps even higher,
while experiments have operated only with s ≤ 8.
More recently, an empirical criterion, the so-called
S*/E stability scaling has been useful for making some
projections to delineate FRC stability regimes, where E ≡
Ls/rs is the plasma elongation, and S* is defined by S* ≡ rs
ωpi /c, where Ls ≡ separatrix length, c ≡ speed of light and
ωpi ≡ ion plasma frequency. S* is based on the maximum
density, and the average density inside the separatrix is a
large fraction (i.e. < β > ≈ 0.9) of the maximum. The S*
parameter is preferable to use as a radial size index from
two points of view: 1) it is based on the natural length
scale of two-fluid analysis, c/ωpi, which is comparable to
the ion gyroradius for β ≈ 1; and 2) it less unambiguous
since density is routinely measured and relatively easily
measured. The size parameter s is more difficult to
calculate, because the ion temperature must usually be
inferred.
The S*/E scaling is based on the assumption that the
magnetohydrodynamic (MHD) growth rate varies as≈E-1.
This scaling combined with a "reactive" effect from Hall
effects or FLR (which is independent of E) gives the
condition S*/E ≡ const for marginal stability. Recent
works that certain pressure profiles allow the favorable
“1/E” scaling to persist for large elongation.
The stability of very elongated field-reversed
configurations is solved [22] by an expansion in the small
parameter (inverse elongation).
Since the FRC is unstable to several low-n MHD
modes, two-fluid or kinetic effect has been considered to
explain the FRC lifetime longer than the MHD time scale
[23]. 2D flowing equilibria with the magnetic and flow
structure is presented. The proposed theory of the “most
probable state of turbulence” is based on the two-fluid
model. The formalism of equilibrium and stability
analyses of a flowing two-fluid plasma is developed to
investigate the effect of the flow on the high beta plasmas
and some new stationary energy states [24] are found but
the question which state is preferred is still without
answer.
Narrow ion rings have proved to be unstable to rapid
azimuthal breakup and thermalization, at least in the
conditions found so far in FIREX. An isotropic
distribution of energetic particles would be more stable.
This might be achieved by an altered injection strtucture.
The FRC stability observed in the experiments can
not be explained within linear theory. Global stability
remains the leading issue affecting the future of FRC
research. A standart ideal MHD analysis of tilting
suggests that internal current profile and separatrix shape
have a strong influence on tilting stability, of course, in
this theory ballooning modes are still unstable with fast
growth rates. The stabilization mechanism is likely to be a
lengthening of the separatrix and the non-linear wave-
particle interaction.
So, a combination of kinetic and nonlinear effects
may explain the transport observed experimentally.
74
Also power balance issues, such as effective
resistivity, opening field lines and enhancement of the
losses concerning RMF must be considered.
CONCLUSIONS
The development of a theory of relaxed/ natural
minimum-energy FRC states (two-fluid plasma physics),
improved confinement (examination of confinement
properties using neutral beam injection), startup by
merging two spheromacs to form an FRC and efficient
current drive by rotating magnetic fields are the most
recent highlights.
Encouraging recent physics progress by the small
worldwide FRC research community has enhanced the
prospects for successful FRC development. Highlights
include indications that natural minimum-energy FRC
states exist [24], stable operation at moderate s, startup by
merging two spheromacs to form an FRC [25], efficient
current drive by rotating magnetic fields, and attractive D-
3He FRC power plant design.
In other words, the main achievements are
developing of FRC stability theory; concept of RMF; and
experiments increasing of lifetime of FRC. Besides, a big
interest presents experiments with electric field inside
plasma (possible confinement improvement) [26].
Experiments on several facilities had demonstrated a
FRC can be formed inside a θ–pinch, RMF coil or by
spheromaks merging and then translated along a
connecting guide field into a region with a steady
magnetic field.
The FRC reactor is cylindrical, which would simplify
much of the maintenance involved. The open field lines
guide charged particles toward the ends for possible direct
conversion as well as effectively removing the energetic
fusion products ions and impurities from the system.
Details of fusion core engineering, including a high
performance cylindrical blanket and shield concept, are
discussed in Ref. 27.
Favorable results from theory and experiments have
raised hopes for development into a practical fusion
system. The present level of research on FRC’s has left
many issues unresolved, support for theoretical analyses
and modeling of experimental data is needed. So, FRC
research should be continued and expanded. FRC
community is strong through collaborations and sharing
of ideas, problems and solutions.
Brief review of the simple compact system with
natural advantages and reactor potential is given.
Theoretical and experimental results over the last decade
are discussed. Conceptual designs and power plant
parameters are presented. Favorable results from theory
and experiments have raised hopes for development a
FRC into a practical fusion system.
REFERENCES
1. M.Tuszewski // Nucl. Fusion 1988, v.28, p.2033.
2. L.C.Steinhauer, et al. // Fusion Technol. 1996, v.30,
p.116.
3. H.Momota, et al. // Fusion Technol. 1992, v.21,
p.2307.
4. J.F.Santarius, et al. // Journal of Fusion Energy 1998,
v.17, p.33.
5. M.Ohnishi, et al. // Fusion Technol. 1995, v.27,
p.391.
6. A.L.Hoffman // Phys. Plasmas 1998, v.5, p.979.
7. A.L.Guo, et al. // Phys. Plasmas 2002, v.9, p.185.
8. A.L.Hoffman // Nucl. Fusion 2000, v.40, p.1523.
9. L.C.Steinhauer // Phys. Plasmas 2001, v.8, p.3367.
10.R.D. Milroy // Phys. Plasmas 2001, v.8, p.2804.
11.J.T.Slough, K.E.Miller // Phys. Rev. Lett. 2000, v.85,
p.1444.
12.T.Asai, et al. // Phys. Plasmas 2000, v.7, p.2294.
13.S.V.Ryzhkov, et al. // Fusion Technol. 2001, v.39
(1T), p.410.
14.V.I.Khvesyuk, S.V.Ryzhkov, A.Yu.Chirkov //
Presented at 29th EPS Conf. on Contr. Fusion and
Plasma Physics (Montreux, 2002).
15.V.S.Lukin, et al. // Phys. Plasmas 2001, v.8, p.1600.
16.C.Qin, et al. // Phys. Plasmas 2001, v.8, p.4816.
17.E.V.Belova, et al. // Phys. Plasmas 2001, v.8, p.1267.
18.Y. Ono, et al. // Nucl. Fusion 1999, v.39, p.2001.
19.J.T.Slough, A.L. Hoffman // Phys. Plasmas 1999,
v.6, p.253.
20.G.A.Wurden, et al. // Rev. Sci. Instrum 2001, v.72,
p.552.
21.M.R.Brown // Phys. Plasmas 1999, v.6, p.1717.
22.D.C.Barnes // Phys. Plasmas 2002, v.9, p.560.
23.L.C.Steinhauer, H.Yamada, and A.Ishida // Phys.
Plasmas 2001, v.8, p.4053.
24.L.C.Steinhauer and A.Ishida // Phys. Plasmas 1998,
v.5, p.2609.
25.M.Yamada, et al. // Phys. Plasmas 1997, v.4, 1936.
26.V.Antoni, et al. // Plasmas Phys. Control Fusion
2000, v.42, p.83.
27.J.F. Santarius, et al. // Fusion Technology Institute,
Madison. Report UWFDM-1129 2000.
75
INTRODUCTION
formation
confinement
Stability
CONCLUSIONS
|