Stellarator theory studies and optimization under EUROfusion
The WPS2 EUROfusion work package entitled “Stellarator Optimization: Theory, Development, Modelling and Engineering” and is targeted to the development of tools for designing new optimised configurations and to support W7-X exploitation. We present here the main research lines and recent achievement...
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| Опубліковано в: : | Вопросы атомной науки и техники |
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| Дата: | 2017 |
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| Мова: | Англійська |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2017
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| Назва журналу: | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| Цитувати: | Stellarator theory studies and optimization under EUROfusion / F. Castejón // Вопросы атомной науки и техники. — 2017. — № 1. — С. 3-5. — англ. |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine| _version_ | 1859618827660165120 |
|---|---|
| author | Castejón, F. |
| author_facet | Castejón, F. |
| citation_txt | Stellarator theory studies and optimization under EUROfusion / F. Castejón // Вопросы атомной науки и техники. — 2017. — № 1. — С. 3-5. — англ. |
| collection | DSpace DC |
| container_title | Вопросы атомной науки и техники |
| description | The WPS2 EUROfusion work package entitled “Stellarator Optimization: Theory, Development, Modelling and Engineering” and is targeted to the development of tools for designing new optimised configurations and to support W7-X exploitation. We present here the main research lines and recent achievements under the work package S2, including those to support W7-X project.
Рабочий пакет WPS2 EUROfusion «Оптимизация стеллараторов: теория, новые разработки, моделирование и инженерия» направлен на развитие методов расчёта новых оптимальных конфигураций для поддержания эксплуатации установки W7-X. Приводятся основные направления и результаты недавних достижений в рамках пакета S2, включая и те, что направлены на поддержку проекта W7-X.
Робочий пакет WPS2 EUROfusion «Оптимізація стелараторів: теорія, нові розробки, моделювання та інженерія» спрямований на розвиток методів розрахунку нових оптимальних конфігурацій для підтримки експлуатації установки W7-X. Наводяться основні напрямки і результати недавніх досягнень у рамках пакету S2, включаючи і ті, що спрямовані на підтримку проекту W7-X.
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| first_indexed | 2025-11-29T00:08:17Z |
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MAGNETIC CONFINEMENT
ISSN 1562-6016. ВАНТ. 2017. №1(107)
PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY. 2017, № 1. Series: Plasma Physics (23), p. 3-5. 3
STELLARATOR THEORY STUDIES AND OPTIMIZATION UNDER
EUROfusion
F. Castejón and WPS2 EUROfusion contributors
Laboratorio Nacional de Fusión, CIEMAT, Madrid, Spain
E-mail: francsico.castejon@ciemat.es
The WPS2 EUROfusion work package entitled “Stellarator Optimization: Theory, Development, Modelling and
Engineering” and is targeted to the development of tools for designing new optimised configurations and to support
W7-X exploitation. We present here the main research lines and recent achievements under the work package S2,
including those to support W7-X project.
PACS: 52.55.Hc; 52.55.Wq; 52.50.Gj
INTRODUCTION
The EUROfusion roadmap establishes several
Missions to be accomplished by the EUROfusion
consortium in order to achieve commercial fusion.
Mission number 8 is devoted to bring stellarators to
maturity and the work is divided into two
workpackages, WPS1 and WPS2. The first one is
devoted to the scientific exploitation of W7-X,
extracting the necessary physics knowledge. The WPS2
is entitled “Stellarator Optimization: Theory,
Development, Modelling and Engineering” and is
targeted to the development of tools for designing new
optimised configurations and to support W7-X
exploitation. We present here a summary of the results
that have been achieved under WPS2 up to date and,
more importantly, the work plan for 2017 and next
years. This exposition is though to describe the
possibilities of collaborating with WPS2 programme.
1. WPS2 OBJECTIVES
The S2 is work package, together with the S1 one, is
devoted to “contribute to bring the stellarator to
maturity”. We recognise that stellarators are one
generation in delay with respect to tokamaks because of
the intrinsic difficulties that the design and simulation
of these devices pose. Stellarators are free from the
main tokamak caveats, so they are considered as a solid
alternative to tokamak concept for a fusion reactor.
Stellarators can work in steady state and are free from
ELMs and disruptions. Disruptions imply an intrinsic
nuclear security problem and ELMs cause an intolerable
heat and particle flux on the walls. The efforts to get
steady state operation are based on current drive
methods, which are not able to guarantee steady state
for the moment.
On the other hand, stellarators need to improve their
confinement and their complicated design, i. e., to
achieve maturity. The main stream of sellarators
research is to research the on the helias, or W7-X-like
configurations. With this target in mind, we have
defined the objectives of this work package as three-
folded. On the one hand we plan to give support to
W7-X Exploitation, producing the necessary
simulations and theoretical tools to help to the
exploitation of this device. This implies also to extract
the physical results from the operation of W7-X and
other strellarators like TJ-II and LHD in order to
introduce them in the optimization loop.
The second target is the optimisation of the W7-X-
like (Helias) concept in view of a future reactor. Here
we will introduce the new developments and findings,
including turbulence, topology and fast ion
confinement. The consideration of new physics for
optimization sometime requires the development of
proxies that allow fast calculations to be introduced in
an optimization loop.
The third target is the inclusion of engineering in the
optimization process: Coil design and room for the
Breeding Blankets. The final chosen magnetic
configuration will be a balance between good
confinement and simplicity in the building of the
device. Engineering activities will be reinforce in the
next future, since the physics is more and more known.
2. NEXT WORK LINES AND RECENT
ACHIEVEMENTS IN WP2
Fig. 1. Left: ray tracing calculations for X2 in W7-X.
Left: Power deposition profile together with the input
density and temperature profiles
One of the activities in support of W7-X operation,
which implies the development of theoetival tools for
design and exploitation of future stellarator reactors is
ECRH and ECCD studies. During the fomer year, the
ray tracing code TRAVIS, developed at IPP-Greifswald
has been used to identify the best ECRH regimes in
W7-X as well as to estimate the driven current. In
particular X2 and O2 heating scenarios have been
identified, developed and the calculations were the input
for testing of these scenarios during the first
experimental phase in W7-X. The test was successful
and shows that these scenarios are feasible to be used
routinely in this device. In the next future, a model for
OXB heating in overdense plasmas (including the
mailto:francsico.castejon@ciemat.es
4 ISSN 1562-6016. ВАНТ. 2017. №1(107)
description of non-planar regions of O-X conversion)
will be built. This module will be introduced in the
TRAVIS code in order to simulate this heating method.
Fig. 1 shows the ray tracing for X2 scenario in W7-X.
Regarding ECCD, during next year we plan to
introduce finite collionality in the current drive
calculations which have been performed in the high
energy limit up to now. The neoclassical code NEO is
modified to include finite collisionality and non-local
effects and this new development is also included in
TRAVIS, so first estimates of finite collisionality
current drive will be available.
Fast ion dynamics and confinement has been also
studied in optimized Helias-like configurations with
reduced bootstrap current. A new configuration suitable
for a reactor has been created (HYDRA-21) with the
conditions of reducing bootstrap current and to improve
fast ion confinement. The first target is necessary in
order to keep almost frozen the value of the rotational
transform in the edge, in order that the island divertor
concept can work properly. The fast ion confinement is
not usually well achieved in stellarator configurations,
so we have to try to improve this. New methods for
calculating fast ion orbits is under development. The
influence of the number of field periods is also studied.
The study of ICRH-generated fast ions and their
confinement is performed using SCENIC, a suit of
codes that includes equilibrium calculation, full wave
propagation and absorption, and fast ion orbits. Hit
points on the vacuum vessel are also calculated.
SCENIC has been developed under WPS2, including
anisotropic equilibrium calculations, a full wave code
and a MC code that estimates fast ion orbits in a
complex 3D system, which allow us to calculate the fast
ion distribution function. The full wave code has
allowed to explore the ICRH regimes suitable for W7X.
Fig. 2 shows the escape of fast ions created by ICRH in
W7-X as a function of toroidal angle.
Fig. 2. Number of lost fast ions created by ICRH as a
function of toroidal angle in W7-X estimated with
SCENIC
Basic transport theory based on Hamiltonian
techniques is used to characterise the properties of
configurations regarding the confinement quality.
Quasi-Symmetric configurations were studied to
develop the tools starting by the simplest case. The
effects of the deviation from Omnigeneity are now
considered, being a basic tool to explore how much the
configuration characteristics can be deviated. These
findings have been implemented in numerical tools for
fast NC calculations, which allows one to compute
neoclassical transport in low collisionality regimes for
optimized stellarators, which might be useful as a
component of an optimization code. Analytical
computation of the effect of high-helicity deviations in
the sqrt(nu) regime and in the superbanana-plateau one
is also considered.
Fig. 3. W7-X like configuration optimised to reduce ITG
transport
Turbulent optimization will be relevant in NC-
optimised stellarators, where turbulent transport will not
be negligible. ITG optimization of Helias configurations
have been carried (Fig. 3) then we have investigated the
possibility of optimizing configurations taking into
account both the ITG and TEM transport channels
combined. On top of that, fast semianalytical
calculations for optimization are developed in order to
estimate the zonal flow properties to explore the
influence of the ZF on the saturation of the turbulence.
The ZF oscillation frequency will be calculated and
compared to GK simulations. Linear and non-linear GK
simulations have been performed in stellarator
configurations, where asymmetries in the potential will
be identified. Semianalytical study of electrostatic
potential perturbations, non-constant on the flux
surfaces, with an assessment on their impact on
impurity transport. Several configurations will be
studied, including Helias-like one. Fig. 4 shows the
results of the ZF residual estimates using these
semianalytical calculations, compared with GK
estimations.
Fig. 4. Comparison of quasi-analytical (CAS3D-
K)estimates of the ZF residual with GK calculations
with the global EUTERPE and the tube-flux GENE
codes, showing a good agreement with both kinetic and
adiabatic electrons
The influence of magnetic topology and equilibrium
on confinement is also studied. It has been found a
decoupling of the NC transport of the rotational
transform value, despite the positive confinement
ISSN 1562-6016. ВАНТ. 2017. №1(107) 5
scalings with iota, and the weak influence, if any, of
magnetic well on confinement.
Fig. 5. EXTENDER calculations of the plasma edge and
SOL topology in W7-X device for different plasma
pressure values. Beta is varied from 0 to 3.3 %
On top of that, the symmetry-breaking caused by
magnetic islands is considered as a possible generator of
ZF by neoclassical effects.
Another important topic considered under WPS2 is
the development of tools to simulate the plasma edge
properly, especially considering the importance of the
divertor design and performance. The island based
divertor concept will be tested in W7-X in full
performance plasmas. The EXTENDER code has been
developed to describe the magnetic topology of plasma
edge and from the LCFS to the device walls. Fig. 5
shows the results of EXTENDER calculations in W7-X
for several values of plasma pressure: beta is varied
from 0 to 3.3 %. On top of EXTENDER, the multi fluid
edge transport code FINDIF is being developed to
perform fast calculations in W7-X and next step
stellarator reactors.
One of the important topics of this WP is to deal
with engineering aspects, trying to take them into
account in the optimization process. The idea is to find a
balance between good confinement stellarators and a
relatively simple coil and TBM sets. The NESCOIL
code is being used to extract the conceptual design of
the coils that create a given magnetic configuration.
Fig. 6 shows a set of the coils that create a possible
reactor configuration that presents good confinement of
fast particles and low value of bootstrap current.
Further engineering activities include the
development and exploitation of the 0D system code
PROCESS devoted to the estimate of the performance
of the device and the neutronic estimates that will be a
useful input for Test Blanket Module activities.
Fig. 6. Conceptual design of the non planar coils that
create the configuration HYDRA-21, which presents
good fast ion confinement and a reduced value of
bootstrap current
CONCLUSIONS
The WPS2 includes the necessary activities to give
support to W7-X exploitation and to develop the tools
and new criteria to optimise stellarator configurations in
order to produce a future stellarator reactor. We deal
with calculations of ECRH, ECCD, ICRH and fast ion
generation. New tools for basic transport theory to
evaluate the quality of configurations are developed.
Equilibrium relaxation and magnetic topology and
turbulence are considered for the first time in the
optimization loop. Basic optimization including good
fast particle confinement and reduced value of bootstrap
current has continued, including the study against the
number of periods. Engineering activities are also
considered in the optimization loop.
No references are shown in this report, given the
extense number of published papers and reports and the
difficulty of choosing some of them.
ACKNOWLEDGEMENTS
This work has been carried out within the framework
of the EUROfusion Consortium and has received
funding from the Euratom research and training
programme 2014-2018 under grant agreement No
633053. The views and opinions expressed herein do
not necessarily reflect those of the European Comission.
Article received 21.10.2016
ТЕОРЕТИЧЕСКИЕ ИССЛЕДОВАНИЯ И ОПТИМИЗАЦИЯ СТЕЛЛАРАТОРОВ В РАМКАХ
EUROfusion
F. Castejón and WPS2 EUROfusion contributors
Рабочий пакет WPS2 EUROfusion «Оптимизация стеллараторов: теория, новые разработки,
моделирование и инженерия» направлен на развитие методов расчёта новых оптимальных конфигураций
для поддержания эксплуатации установки W7-X. Приводятся основные направления и результаты недавних
достижений в рамках пакета S2, включая и те, что направлены на поддержку проекта W7-X.
ТЕОРЕТИЧНІ ДОСЛІДЖЕННЯ ТА ОПТИМІЗАЦІЯ СТЕЛАРАТОРІВ У РАМКАХ EUROfusion
F. Castejón and WPS2 EUROfusion contributors
Робочий пакет WPS2 EUROfusion «Оптимізація стелараторів: теорія, нові розробки, моделювання та
інженерія» спрямований на розвиток методів розрахунку нових оптимальних конфігурацій для підтримки
експлуатації установки W7-X. Наводяться основні напрямки і результати недавніх досягнень у рамках
пакету S2, включаючи і ті, що спрямовані на підтримку проекту W7-X.
|
| id | nasplib_isofts_kiev_ua-123456789-122111 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 1562-6016 |
| language | English |
| last_indexed | 2025-11-29T00:08:17Z |
| publishDate | 2017 |
| publisher | Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| record_format | dspace |
| spelling | Castejón, F. 2017-06-27T14:04:08Z 2017-06-27T14:04:08Z 2017 Stellarator theory studies and optimization under EUROfusion / F. Castejón // Вопросы атомной науки и техники. — 2017. — № 1. — С. 3-5. — англ. 1562-6016 PACS: 52.55.Hc; 52.55.Wq; 52.50.Gj https://nasplib.isofts.kiev.ua/handle/123456789/122111 The WPS2 EUROfusion work package entitled “Stellarator Optimization: Theory, Development, Modelling and Engineering” and is targeted to the development of tools for designing new optimised configurations and to support W7-X exploitation. We present here the main research lines and recent achievements under the work package S2, including those to support W7-X project. Рабочий пакет WPS2 EUROfusion «Оптимизация стеллараторов: теория, новые разработки, моделирование и инженерия» направлен на развитие методов расчёта новых оптимальных конфигураций для поддержания эксплуатации установки W7-X. Приводятся основные направления и результаты недавних достижений в рамках пакета S2, включая и те, что направлены на поддержку проекта W7-X. Робочий пакет WPS2 EUROfusion «Оптимізація стелараторів: теорія, нові розробки, моделювання та інженерія» спрямований на розвиток методів розрахунку нових оптимальних конфігурацій для підтримки експлуатації установки W7-X. Наводяться основні напрямки і результати недавніх досягнень у рамках пакету S2, включаючи і ті, що спрямовані на підтримку проекту W7-X. This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training programme 2014-2018 under grant agreement No 633053. The views and opinions expressed herein do not necessarily reflect those of the European Comission. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Магнитное удержание Stellarator theory studies and optimization under EUROfusion Теоретические исследования и оптимизация стеллараторов в рамках EUROfusion Теоретичні дослідження та оптимізація стелараторів у рамках EUROfusion Article published earlier |
| spellingShingle | Stellarator theory studies and optimization under EUROfusion Castejón, F. Магнитное удержание |
| title | Stellarator theory studies and optimization under EUROfusion |
| title_alt | Теоретические исследования и оптимизация стеллараторов в рамках EUROfusion Теоретичні дослідження та оптимізація стелараторів у рамках EUROfusion |
| title_full | Stellarator theory studies and optimization under EUROfusion |
| title_fullStr | Stellarator theory studies and optimization under EUROfusion |
| title_full_unstemmed | Stellarator theory studies and optimization under EUROfusion |
| title_short | Stellarator theory studies and optimization under EUROfusion |
| title_sort | stellarator theory studies and optimization under eurofusion |
| topic | Магнитное удержание |
| topic_facet | Магнитное удержание |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/122111 |
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