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Academic literature on the topic 'Stellarator'

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Published: 4 June 2021
Last updated: 6 September 2023

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Journal articles on the topic "Stellarator"

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Beidler, C. D., H. M. Smith, A. Alonso, T. Andreeva, J. Baldzuhn, M. N. A. Beurskens, M. Borchardt, et al. "Demonstration of reduced neoclassical energy transport in Wendelstein 7-X." Nature 596, no. 7871 (August 11, 2021): 221–26. http://dx.doi.org/10.1038/s41586-021-03687-w.

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AbstractResearch on magnetic confinement of high-temperature plasmas has the ultimate goal of harnessing nuclear fusion for the production of electricity. Although the tokamak1 is the leading toroidal magnetic-confinement concept, it is not without shortcomings and the fusion community has therefore also pursued alternative concepts such as the stellarator. Unlike axisymmetric tokamaks, stellarators possess a three-dimensional (3D) magnetic field geometry. The availability of this additional dimension opens up an extensive configuration space for computational optimization of both the field geometry itself and the current-carrying coils that produce it. Such an optimization was undertaken in designing Wendelstein 7-X (W7-X)2, a large helical-axis advanced stellarator (HELIAS), which began operation in 2015 at Greifswald, Germany. A major drawback of 3D magnetic field geometry, however, is that it introduces a strong temperature dependence into the stellarator’s non-turbulent ‘neoclassical’ energy transport. Indeed, such energy losses will become prohibitive in high-temperature reactor plasmas unless a strong reduction of the geometrical factor associated with this transport can be achieved; such a reduction was therefore a principal goal of the design of W7-X. In spite of the modest heating power currently available, W7-X has already been able to achieve high-temperature plasma conditions during its 2017 and 2018 experimental campaigns, producing record values of the fusion triple product for such stellarator plasmas3,4. The triple product of plasma density, ion temperature and energy confinement time is used in fusion research as a figure of merit, as it must attain a certain threshold value before net-energy-producing operation of a reactor becomes possible1,5. Here we demonstrate that such record values provide evidence for reduced neoclassical energy transport in W7-X, as the plasma profiles that produced these results could not have been obtained in stellarators lacking a comparably high level of neoclassical optimization.
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Landreman, M., S. Buller, and M. Drevlak. "Optimization of quasi-symmetric stellarators with self-consistent bootstrap current and energetic particle confinement." Physics of Plasmas 29, no. 8 (August 2022): 082501. http://dx.doi.org/10.1063/5.0098166.

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Quasi-symmetry can greatly improve the confinement of energetic particles and thermal plasma in a stellarator. The magnetic field of a quasi-symmetric stellarator at high plasma pressure is significantly affected by the bootstrap current, but the computational cost of accurate stellarator bootstrap calculations has precluded use inside optimization. Here, a new efficient method is demonstrated for optimization of quasi-symmetric stellarator configurations such that the bootstrap current profile is consistent with the geometry. The approach is based on the fact that all neoclassical phenomena in quasi-symmetry are isomorphic to those in axisymmetry. Therefore, accurate formulas for the bootstrap current in tokamaks, which can be evaluated rapidly, can be applied also in stellarators. The deviation between this predicted parallel current and the actual parallel current in the magnetohydrodynamic equilibrium is penalized in the objective function, and the current profile of the equilibrium is included in the parameter space. Quasi-symmetric configurations with significant pressure are thereby obtained with self-consistent bootstrap current and excellent confinement. In a comparison of fusion-produced alpha particle confinement across many stellarators, the new configurations have significantly lower alpha energy losses than many previous designs.
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Garrido, Izaskun, Javier Maseda, Itziar Martija, and Aitor J. Garrido. "Real-Time Control for the EHU Stellarator." Symmetry 12, no. 1 (December 19, 2019): 11. http://dx.doi.org/10.3390/sym12010011.

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At present, two main magnetic confinement fusion devices exist: tokamaks and stellarators. Moreover, stellarators have been demonstrated to be a good alternative to tokamaks, due to their ability to operate in continuous mode, which eventually translates into a higher commercial profitability. In stellarators, the magnetic confinement of the plasma is achieved exclusively by the coils, thus no electric current through the plasma is needed. In particular, this article presents the Columbia Non-Neutral Torus stellarator that is located in the Automatic Control Group of Euskal Herriko Unibertsitatea (EHU). This EHU stellarator maintains symmetry in its structure due to the topology of the mesh that is formed by its coils. A cornerstone of future fusion reactors is to obtain real-time control that enables a sustained reaction. In this article, a control-oriented model for the installed magnetic confinement coils is presented. The model is based on matrices that preserve symmetry, which is defined from physical principles and then validated by different sets of experimental data. Then, based on this model, a novel predictive control suited to this particular model with symmetric objective function is implemented in the numerical simulations, and its response is compared to that of traditional controllers. Finally, this control is implemented in a real plant and the satisfactory experiment results provide validation of both the numerical model and proposed controller.
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Nikulsin, N., R. Ramasamy, M. Hoelzl, F. Hindenlang, E. Strumberger, K. Lackner, and S. Günter. "JOREK3D: An extension of the JOREK nonlinear MHD code to stellarators." Physics of Plasmas 29, no. 6 (June 2022): 063901. http://dx.doi.org/10.1063/5.0087104.

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Although the basic concept of a stellarator was known since the early days of fusion research, advances in computational technology have enabled the modeling of increasingly complicated devices, leading up to the construction of Wendelstein 7-X, which has recently shown promising results. This recent success has revived interest in the nonlinear 3D MHD modeling of stellarators in order to better understand their performance and operational limits. This study reports on the extension of the JOREK code to 3D geometries and on the first stellarator simulations carried out with it. The first simple simulations shown here address the classic Wendelstein 7-A stellarator using a reduced MHD model previously derived by us. The results demonstrate that stable full MHD equilibria are preserved in the reduced model: the flux surfaces do not move throughout the simulation and closely match the flux surfaces of the full MHD equilibrium. Furthermore, both tearing and ballooning modes were simulated, and the linear growth rates measured in JOREK are in reasonable agreement with the growth rates from the CASTOR3D linear MHD code.
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Lonigro, Nicola, and Caoxiang Zhu. "Stellarator coil design using cubic splines for improved access on the outboard side." Nuclear Fusion 62, no. 6 (April 6, 2022): 066009. http://dx.doi.org/10.1088/1741-4326/ac2ff3.

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Abstract In recent years many efforts have been undertaken to simplify coil designs for stellarators due to the difficulties in fabricating non-planar coils. The FOCUS code removes the need for a winding surface and represents the coils as arbitrary curves in 3D. In the following work, the implementation of a spline representation for the coils in FOCUS is described, along with the implementation of a new engineering constraint to design coils with a straighter outer section. The new capabilities of the code are shown as an example on HSX, NCSX, and a prototype quasi-axisymmetric reactor-sized stellarator. The flexibility granted by splines along with the new constraint will allow for stellarator coil designs with improved accessibility and simplified maintenance.
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Tykhyy, A. V. "Stochastic Diffusion of Energetic Ions in Wendelstein-Type Stellarators." Ukrainian Journal of Physics 63, no. 6 (July 12, 2018): 495. http://dx.doi.org/10.15407/ujpe63.6.495.

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The collisionless stochastic diffusion of energetic ions in optimized stellarators of the Wendelstein type has been considered. The phenomenon concerned was predicted earlier in the framework of a simplified theory describing the separatrix crossing by ions. The jumps of the adiabatic invariant in magnetic configurations of a stellarator are calculated. The analysis of the results obtained confirms the importance of the stochastic diffusion and demonstrates that the diffusion coefficient can considerably exceed the available result.
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Zhang, Yichao, Haifeng Liu, Jie Huang, Yuhong Xu, Jian Zhang, Akihiro Shimizu, Shinsuke Satake, et al. "Suppression of non-axisymmetric field-induced α-particle loss channels in a quasi-axisymmetric stellarator." AIP Advances 12, no. 5 (May 1, 2022): 055214. http://dx.doi.org/10.1063/5.0079827.

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In future fusion reactors, the confinement of α-particles is a crucial issue. The perfect omnigenity may be difficult to achieve in the quasi-isodynamic and quasi-symmetric stellarators when a multi-objective optimization is considered. Non-axisymmetric field can result in collisionless particles’ transport via localized trapping by ripples. Specific loss channels have been revealed to essentially exist in quasi-axisymmetric stellarators [Yang et al., Europhys. Lett. 129, 35001 (2020)] and W7-X [J. M. Faustin et al., Nucl. Fusion 56, 092006 (2016)]. It indicates a drastic loss of collisionless ions through these channels. This paper is devoted to investigate the effects of axisymmetry-breaking magnetic fields on collisionless α-particle transport in the CFQS (Chinese First Quasi-axisymmetric Stellarator) -like reactor configuration. A semi-analytic representation of radial and poloidal drifts in Boozer coordinates is given, by which we found an effective route to mitigate α-particle losses, i.e., adjusting the location of the quasi-axisymmetric radial position. Such a route enables the enhancement of the poloidal drift and decrease of radial drift in peripheral regions of the identified loss channels. The particles launched inside the quasi-axisymmetric radial surface can be well confined because localized particles that may fall in loss channels can transit into blocked particles near the quasi-axisymmetric surface, escaping from loss channels, which is beneficial for the improvement of the particle confinement. Moreover, this paper may provide a set of proxy functions for suppression of energetic particle losses to optimize stellarator configurations.
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Baillod, A., J. Loizu, J. P. Graves, and M. Landreman. "Stellarator optimization for nested magnetic surfaces at finite β and toroidal current." Physics of Plasmas 29, no. 4 (April 2022): 042505. http://dx.doi.org/10.1063/5.0080809.

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Good magnetic surfaces, as opposed to magnetic islands and chaotic field lines, are generally desirable for stellarators. In previous work, Landreman et al. [Phys. of Plasmas 28, 092505 (2021)] showed that equilibria computed by the Stepped-Pressure Equilibrium Code (SPEC) [Hudson et al., Phys. Plasmas 19, 112502 (2012)] could be optimized for good magnetic surfaces in vacuum. In this paper, we build upon their work to show the first finite- β, fixed-, and free-boundary optimization of SPEC equilibria for good magnetic surfaces. The objective function is constructed with the Greene's residue of selected rational surfaces, and the optimization is driven by the SIMSOPT framework [Landreman et al., J. Open Source Software 6, 3525 (2021)]. We show that the size of magnetic islands and the consequent regions occupied by chaotic field lines can be minimized in a classical stellarator geometry (rotating ellipse) by optimizing either the injected toroidal current profile, the shape of a perfectly conducting wall surrounding the plasma (fixed-boundary case), or the vacuum field produced by the coils (free-boundary case). This work shows that SPEC can be used as an equilibrium code both in a two-step or single-step stellarator optimization loop.
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Zhu, Caoxiang, Kenneth Hammond, Adam Rutkowski, Keith Corrigan, Douglas Bishop, Arthur Brooks, Peter Dugan, et al. "PM4Stell: A prototype permanent magnet stellarator structure." Physics of Plasmas 29, no. 11 (November 2022): 112501. http://dx.doi.org/10.1063/5.0102754.

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Permanent magnets provide a possible solution to simplify complicated stellarator coils. A prototype permanent magnet stellarator structure, PM4Stell, has been funded to demonstrate the technical feasibility of using permanent magnets to create the shaping field of a stellarator. Permanent magnets in uniform cubes with three polarization directions will be carefully placed to generate the required magnetic field for a National Compact Stellarator eXperiment-like equilibrium together with planar toroidal field coils. Discrete magnets will be glued together and inserted into a “post-office-box-like” supporting structure. Electromagnetic and structural analyses have been done to validate the design. Error field correction magnets will be used to shim possible error fields. The design efforts of the prototype permanent magnet stellarator structure are discussed.
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Zanca, P., F. Sattin, D. F. Escande, and F. Auriemma. "A power-balance model for the L-mode radiative density limit in fusion plasmas." Plasma Physics and Controlled Fusion 64, no. 5 (March 30, 2022): 054006. http://dx.doi.org/10.1088/1361-6587/ac57cc.

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Abstract A 1D cylindrical power-balance model of the radiation density limit (DL) gives a unified description of this phenomenon for stellarators, reversed field pinches and L-mode tokamaks (Zanca et al 2019 Nucl. Fusion 59 126011). The DL scaling laws for the three different configurations are all derived from a combination of just two equations: (a) a single-fluid heat-transport equation; (b) on-axis Ohm’s law with Spitzer resistivity, taken in a suitable limit for the stellarator. Here, we present a refined version of the model, alongside further experimental evidence supporting its successful application.
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Dissertations / Theses on the topic "Stellarator"

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Kendl, Alexander. "Driftwellen in Helias-Konfigurationen." [S.l. : s.n.], 2000. http://deposit.ddb.de/cgi-bin/dokserv?idn=959973532.

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Unemura, Takeshi. "Nonlinear Behavior of Pressure Driven Modes in Stellarator Plasmas." Kyoto University, 2003. http://hdl.handle.net/2433/148650.

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Kyoto University (京都大学)
0048
新制・課程博士
博士(エネルギー科学)
甲第10332号
エネ博第68号
新制||エネ||20(附属図書館)
UT51-2003-H753
京都大学大学院エネルギー科学研究科エネルギー基礎科学専攻
(主査)教授 前川 孝, 教授 近藤 克己, 助教授 浜口 智志
学位規則第4条第1項該当
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Zhang, Yangyang. "Three Dimensional Physics in Reversed Field Pinch and Stellarator." Doctoral thesis, Università degli studi di Padova, 2017. http://hdl.handle.net/11577/3426218.

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This dissertation is dedicated to the study of three dimensional transport in toroidal magnetic configurations induced by the presence of the magnetic islands, which break the nested flux surfaces and make the magnetic field intrinsically three dimensional. The methodology applied is based on defining a certain symmetry so that the transport study could be performed in the approximation of 1.5 dimensions. The work has been carried out on both RFX-mod Reversed Field Pinch (RFP) and the TJ-II stellarator. RFX-mod is the largest RFP in the world. The RFP configuration is sustained by the so-called dynamo mechanism, which is related to the non-linear interactions among many resonating MHD tearing modes. The transport study on RFX-mod has been performed on the three sub-states identified in the Quasi-Single Helicity regime, that features one single mode (dominant mode) dominating the mode spectrum, while the rest of the modes (secondary modes) remain at low amplitudes. In this regime proper flux coordinates can be identified considering an equilibrium built on the underlying axi-symmetric magnetic field plus the contribution from the dominant mode. In this way, a 1.5 dimensional approximation transport study is possible by averaging different physical quantities over the flux surfaces. The transport study is focused on the bean-shaped region where nearly conserved flux surfaces have been identified, on which the formation of steep thermal gradients is observed, interpreted as electron Internal Transport Barrier (eITB). Starting from experimental measurements, both the thermal gradients and the thermal diffusivity have been calculated and their behaviors have been discussed within the framework of stochastic transport. Finally, the energy confinement time has also been evaluated, adopting an improved method with respect to past studies, and the results show a significant improvement. The transport study on TJ-II stellarator focuses on the calculation of the enhanced non-ambipolar radial electric field due to the presence of the magnetic islands. The main idea of the study is that the magnetic islands could modify the toroidal plasma viscosity, giving rise to an enhancement on the non-ambipolar particle fluxes. This work started with the study of the Neoclassical Toroidal Viscosity developed by K. C. Shaing for tokamak configurations, which ideally has a toroidal symmetry. Applying this theory, the particle flux can be expressed as a function of a monotonic radial coordinate and thus the transport study could be performed with a 1.5-dimensional approach. A moderate modification on the original theory has been made and the corresponding justification is presented, together with the detailed study in both tokamak and TJ-II configurations. The results show that an 'extra' local radial electric field is indeed induced by the magnetic islands in TJ-II plasmas, which could play a positive role in the plasma confinement properties by affecting the L-H transition, which is believed to be strongly linked to the shear of E x B flow.
Questo lavoro di tesi è dedicato allo studio degli effetti tridimensionali sul trasporto indotti dalla presenza di isole magnetiche in configurazioni toroidali per il confinamento magnetico. Le isole magnetiche producono la rottura delle superfici magnetiche annidate dando al campo magnetico caratteristiche intrinsecamente tridimensionali. La metodologia pplicata si base sulla possibilità di definire un certo livello di simmetria in maniera tale da poter studiare il trasporto nell’approssimazione di 1.5 dimensioni. Lo studio è stato fatto sul Reversed Field Pinch (RFP) RFX-mod e sullo stellarator TJ-II. RFX-mod è il più grande RFP al mondo. La configurazione RFP è sostenuta dal meccanismo della dinamo, che è legato all’interazione non-lineare dei molti modi tearing risonanti. Lo studio del trasporto in RFX-mod è stato eseguito sui tre sotto-stati identificati nel regime a Quasi singola Elicità, il quale è caratterizzato da un singolo modo (modo dominante) che risulta dominante nello spettro dei modi, mentre gli altri modi (modi secondari) mantengono un’ampiezza ridotta. In questo regime, sono identificabile delle coordinate di flusso magnetico basate sulla combinazione dell’equilibrio assial-simmetrico sottostante con il contributo del modo dominante. In questa modo un approccio 1.5 dimensionale allo studio del trasporto è possibile considerando la media sulle superfici di flusso delle varie quantità fisiche. Lo studio del trasporto è riferito alla regione a forma di fagiolo dove è possibile identificare delle superfici di flusso quasi conservate dove si osserva la formazione di ripidi gradienti termici, interpretabili come barriere interne di trasporto elettronico (ITB). A partire dalle misure sperimentali, sono stati calcolati sia i gradienti termici che il coefficiente di diffusione termica e il loro andamento è stato discusso nell’ambito del trasporto stocastico. Alla fine è stato anche calcolato il tempo di confinamento dell’energia, utilizzando un metodo migliorato rispetto a quanto fatto in passato, dimostrando un significativo miglioramento delle prestazioni del plasma. Lo studio del trasporto nello stellarator TJ-II si è concentrato nel calcolo dell’aumento del campo elettrico non-ambipolare dovuto alla presenza di isole magnetiche. L’idea alla base dello studio si basa sul fatto che un’isola magnetica potrebbe modificare la viscosità toroidale del plasma, aumentando in questo modo il flusso non-ambipolare delle particelle. Lo studio è partito dall’analisi del modello neoclassico di viscosità toroidale sviluppato da K.C. Shaing per la configurazione tokamak, che idealmente possiede una simmetria toroidale. Applicando questa teoria, il flusso di particelle può essere descritto in funzione di una coordinata radiale monotona e quindi lo studio del trasporto può essere affrontato nell’approssimazione 1.5 dimensionale. E’ stato necessario considerare una parziale modifica della teoria originale la cui giustificazione viene presentata assieme allo studio dettagliato sia nella configurazione tokamak che nello stellarator TJ-II. I risultati mostrano che un campo elettrico radiale ‘aggiuntivo’ è effettivamente indotto da un’isola magnetica nei plasmi di TJ-II. Questo potrebbe giocare un ruolo positivo nelle proprietà di confinamento del plasma, influenzando la transizione L-H, che si ritiene sia fortemente legata allo shear del moto ExB.
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Kauffmann, Karla [Verfasser]. "Including Collisions in Gyrokinetic Tokamak and Stellarator Simulations / Karla Kauffmann." Greifswald : Universitätsbibliothek Greifswald, 2012. http://d-nb.info/1021840904/34.

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Hakso, H. (Heidi). "Nuclear fusion energy and comparison of tokamak and stellarator reactors." Bachelor's thesis, University of Oulu, 2018. http://urn.fi/URN:NBN:fi:oulu-201805261943.

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This bachelor’s thesis presents the basic principles of nuclear fusion energy, its sustainability and compares the two most prominent fusion reactors; tokamaks and stellarators. Work is done through a literature review. Topic is relevant because energy demand is increasing and environmentally friendly ways of producing energy are needed. Fusion energy could have potential to produce vast amounts of pollution free energy without the long-lived radioactive waste or the risk of runaway reactions. However, fusion reactors have not yet been able to prove their feasibility in power generation due to its challenging physics and technology. Fusion and fission are nuclear reactions. In fusion, light atoms fuse together whereas in fission heavy atoms break apart. The reactions produce energy based on the nuclear binding energy as the created atoms are more stable i.e. have a greater binding energy than the initial ones. Produced energy is related to the created mass defect between the nuclei and the separate nucleons. Fusion reactions happen inside plasma. Temperature, density and confinement of plasma, i.e. triple product, need to reach high enough values for fusion to work. Both tokamaks and stellarators use magnetic confinement as plasma is electrically charged and can be controlled with magnetic fields. Magnetic configurations set the two reactors apart. Tokamaks have toroidal and poloidal superconducting magnetic coils. They also have a transformer creating an electric current in the plasma. Their biggest advantage is their symmetrical and simple structure, but a big disadvantage is the transformer-driven current that forces tokamaks to work only in pulses. Stellarators have only magnetic coils and no current inside the plasma. To ensure plasma confinement, their structure is helically twisted and non-axisymmetric making the complicated structure their biggest disadvantage. Lack of current makes them work continuously, which is their biggest advantage. ITER’s tokamak in France and IPP’s Wendelstein 7-X stellarator in Germany show the current state of fusion research. These are used as examples in the thesis. Currently tokamaks are more advanced and closer in generating more energy than is needed to heat the plasma. As plasma physics evolves and the stellarator instabilities are fixed, their continuous operation might make them more viable for the future
Tämä kandidaatintyö esittelee ydinfuusioenergian perusperiaatteet, sen kestävyysnäkökulmat, ja vertailee kahta lupaavinta reaktoria; tokamakia ja stellaraattoria. Työ on kirjallisuuskatsaus. Aihe on ajankohtainen, sillä energiantarve kasvaa ja ympäristöystävällisempiä energiamuotoja tarvitaan. Fuusioenergialla on potentiaalia tuottaa suuria määriä päästötöntä energiaa ilman pitkäikäistä radioaktiivista jätettä tai suurien ydinonnettomuuksien riskiä. Fuusioreaktorit eivät vielä ole onnistuneet todistamaan fuusiovoimaloiden toteutettavuutta johtuen fuusion haastavasta fysiikasta ja teknologiasta. Fuusio ja fissio ovat ydinreaktioita. Fuusiossa kevyet atomit sulautuvat yhteen ja fissiossa raskaat atomit hajoavat pienemmiksi. Reaktiot tuottavat energiaa johtuen sidosenergiasta, kun syntyneet atomit ovat vakaampia eli omaavat korkeamman sidosenergian kuin alkuperäiset. Syntynyt energia voidaan laskea massavajeesta atomiytimien ja erillään olevien nukleonien välillä. Fuusioreaktiot tapahtuvat plasmassa. Plasman lämpötilan, tiheyden ja koossapitoajan eli kolmitulon tulee saavuttaa riittävän korkeat arvot, jotta fuusio voi onnistua. Tokamakit ja stellaraattorit molemmat käyttävät magneettista koossapitoa, sillä plasma on sähköisesti varautunutta ja siten sitä voidaan kontrolloida magneettikenttien avulla. Magneettien kokoonpano on reaktorien suurin eroavaisuus. Tokamakeissa on toroidaalisia ja poloidaalisia suprajohtavia magneettikeloja. Niissä on myös muuntaja, joka luo sähkövirran plasmaan. Tokamakien suurin etu on niiden symmetrinen ja yksinkertainen rakenne, mutta muuntajan tuottaman epäjatkuvan virran takia voivat ne toimia vain pulsseissa. Stellaraattorit käyttävät vain magneettikeloja, ilman sähkövirtaa plasmassa. Varmistaakseen plasman koossapidon, ovat stellaraattorit epäsymmetrisiä ja kierteisiä. Muuntajan poissaolon takia niiden suurin etu on mahdollisuus jatkuvatoimisuuteen. Suurin haitta stellaraattoreilla on kuitenkin niiden monimutkainen rakenne. ITERin tokamak Ranskassa ja IPP:n stellaraattori Wendelstein 7-X Saksassa kuvaavat hyvin fuusioreaktoreiden tutkimuksen nykytilaa. Nämä reaktorit ovat esimerkkeinä tässä työssä. Tällä hetkellä tokamakit ovat kehittyneempiä ja lähempänä tuottamaan enemmän energiaa kuin mitä plasman lämmittämiseen tarvitaan. Kun plasmafysiikka kehittyy ja stellaraattorien epävakauksia korjataan, voi jatkuvatoimisuus tehdä niistä paremman vaihtoehdon tulevaisuuteen
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Ichiguchi, Katsuji. "Numerical Studies of Three-Dimensional Equilibrium and Stability for Stellarator/Heliotron Configurations." Kyoto University, 1989. http://hdl.handle.net/2433/74743.

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Empacher, Lars. "Analyse eines Vielstrahl-Wellenleiters zur Übertragung hoher Mikrowellenleistungen." [S.l.] : Universität Stuttgart , Fakultät Elektrotechnik, 1999. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB8287462.

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Sichardt, Gabriel [Verfasser], and Thomas [Akademischer Betreuer] Hirth. "Electron cyclotron emission investigations at the stellarator TJ-K / Gabriel Sichardt ; Betreuer: Thomas Hirth." Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2020. http://d-nb.info/1212034597/34.

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Rakha, Allah. "Analysis of energetic particle-driven Alfvénic instabilities in tokamak and stellarator plasmas using three dimensional numerical tools." Doctoral thesis, Universitat Politècnica de Catalunya, 2019. http://hdl.handle.net/10803/671252.

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In this thesis, a detailed analysis of the experientially observed energetic particle-driven Alfvénic instabilities in tokamak and stellarator plasmas using three dimensional numerical tools based on the reduced MHD model has been carried out. In TJ-II stellarator plasmas, modelling of chirping and steady modes assesses their coexistence on the persistent appearance of the corresponding combination of the toroidal (n) and poloidal (m) mode numbers through the rotational transform sensitivity analysis both in iota lowering and iota rising dynamic plasmas. Modelling of the experimentally observed frequency sweeping phenomenon during the presence of Alfvénic activity with radially extended low-shear and radially localized strong-shear non-monotonic (NM) iota profiles provides an extended spectrum of Alfvénic modes in the wide frequency range as compared with normal (monotonic) iota profile results. Comparison of mode frequencies calculated using a standard dispersion relation and those modelled with the reduced MHD clustered frequency solver AE3D shows an agreement with the selection of iota minimum values, which supports MHD spectroscopy calculations. Wave particle interaction (WPI) studies for the resonance function calculations developed using Monte Carlo transport model based on the 3D MHD equilibria for the TJ-II plasmas suggest for low bounce harmonics (p) the possibility of describing the non-linear evolution of the AEs in TJ-II by a sum of two ion populations with different weighting factors, one of which is dominated by drag and the other by diffusion. As the bounce harmonic increases, the resonance region starts to expand and can cover a significant area of the particle phase space until this resonance region vanishes at high bounce harmonics. In ASDEX Upgrade tokamak plasmas a bifurcated MHD equilibrium is reconstructed with formation of 3D helical core as saturated magnetic axis and the remaining torus with an axisymmetric equilibrium. The formation of helical core is characterized as an 3D perturbation in an axisymmetric equilibrium state. Helically distorted MHD equilibria exit for the axisymmetric devices if q = 1 rational surfaces are present. Alfvén continuum calculations with the bifurcated equilibria lead to the frequency splitting between the highest frequency branch and the lowest frequency branch continua at the frequency accumulation point. Radially localised shifting of modes happens via coupling of the adjacent n-1 continuum around an accumulation point. Modelling including 3D effects correctly reproduces the phenomenon of continuum frequency splitting and provides a possible solution for the differences of few kHz in frequency splitting, which remained unexplained with the 2D kinetic calculations. The pressure scaling confirms the increase of helical excursion of the magnetic axis in equilibrium reconstruction and hence the range of continuum frequency splitting. The existence of low-frequency continua and its splitting around the frequency accumulation point are in agreement with the experimental observations for the low-frequency modes. This dissertation provides an extensive comparison of the experimental and modelling results for the TJ-II stellarator plasmas along with the effect of the formation of bifurcated MHD equilibria on Alfvén continua in AUG tokamak plasmas.
En esta tesis, se ha llevado a cabo un análisis detallado de las inestabilidades Alfvénicas de partículas energéticas observadas experimentalmente en plasmas de tokamak y stellarators utilizando herramientas numéricas tridimensionales basadas en el modelo MHD reducido. En los plasmas de estellarators de TJ-II, el modelado de chirping y modos estables evalúa su coexistencia en la aparición persistente de la combinación correspondiente de los números de modo toroidal (n) y poloidal (m) a través del análisis de sensibilidad de transformación rotacional tanto en disminución de iota como en aumento de iota. El modelado del fenómeno de barrido de frecuencia observado experimentalmente durante la presencia de actividad Alfvénica con perfiles de iota no monotónicos (NM) de cizallamiento fuerte y de cizallamiento fuerte radialmente extendido proporciona un espectro extendido de modos Alfvénicos en el amplio rango de frecuencia en comparación con el normal (monotónico). La comparación de las frecuencias de modo calculadas usando una relación de dispersión estándar y aquellas modeladas con el solver de frecuencia agrupada para MHD reducido AE3D muestra un acuerdo con la selección de valores mínimos de iota, que respalda los cálculos de espectroscopía MHD. Los estudios de interacción de onda-partículas (WPI) para los cálculos de la función de resonancia desarrollados utilizando el modelo de transporte Monte Carlo basado en los equilibrios 3D MHD para los plasmas TJ-II sugieren para armónicos de bajo rebote (p) la posibilidad de describir la evolución no lineal de los AE en TJ-II por una suma de dos poblaciones de iones con diferentes factores de ponderación, uno de los cuales está dominado por arrastre y el otro por difusión. A medida que aumenta el armónico de rebote, la región de resonancia comienza a expandirse y puede cubrir un área significativa del espacio de fase de partículas hasta que esta región de resonancia se desvanece en armónicos de alto rebote. En los plasmas del ASDEX Upgrade tokamak se reconstruye un equilibrio MHD bifurcado con formación de núcleo helicoidal 3D como eje magnético saturado y el toro restante con un equilibrio axisimétrico. La formación del núcleo helicoidal se caracteriza como una perturbación 3D en un estado de equilibrio axisimétrico. Los equilibrios MHD distorsionados helicoidalmente salen para los dispositivos axisimétricos si en q = 1 están presentes superficies racionales. Los cálculos continuos de Alfvén con los equilibrios bifurcados conducen a la división de frecuencia entre la rama de frecuencia más alta y la rama de frecuencia más baja continua en el punto de acumulación de frecuencia. El cambio de modos radialmente localizado ocurre mediante el acoplamiento del continuo n-1 adyacente alrededor de un punto de acumulación. El modelado que incluye efectos 3D reproduce correctamente el fenómeno de la división de frecuencia continua y proporciona una posible solución para las diferencias de pocos kHz en la división de frecuencia, que permaneció sin explicación con los cálculos cinéticos 2D. La escala de presión confirma el aumento de la excursión helicoidal del eje magnético en la reconstrucción de equilibrio y, por lo tanto, el rango de división de frecuencia continua. La existencia de continuas de baja frecuencia y su división alrededor del punto de acumulación de frecuencia están de acuerdo con las observaciones experimentales para los modos de baja frecuencia. Este estudio se compone de una comparación extena de los resultados experimentales y de modelaje para los plasmas del stellarator TJ-II junto con el efecto de formación del equilibrio MHD bifurcado en el continuo Alfvén en los plasmas del AUG tokamak.
(Neerlandès) De experimenteel waargenomen Alfvénic-instabiliteiten die in tokamak- en stellaratorplasma's aangedreven worden door snelle deeltjes worden in detail geanalyseerd. De analyse gebeurde met behulp van driedimensionale numerieke methodes gebaseerd op het gereduceerde MHD-model. In TJ-II stellarator plasma's werd de co-existentie van tjilpende (chirping) en steady-state modi vastgesteld op basis van het aanhoudend voorkomen van de overeenkomstige combinatie van de toroïdale (n) en poloidale (m) modenummers. Deze vaststelling gebeurde op basis van de gevoeligheid ten opzichte van de rotatie-transformatie (rotational transform). Modellering van de veging van de frequentie (frequency sweeping) van de Alfvénic-activiteit met niet-monotone iota-profielen zijn, in vergelijking met normale (monotone) iota-profielresultaten, consistent met experimentele resultaten. Studies van de interactie tussen golf en deeltjes (WPI-wave particle interaction) voor de berekening van de resonantiefunctie met behulp van Monte Carlo transportmodel voor TJ-II plasma's, suggereren dat de niet-lineaire evolutie van AE's een som is van twee ion populaties met verschillende wegingsfactoren. Voor lage bounce harmonische, wordt één gedomineerd door sleep (drag) en de andere door diffusie. In ASDEX Upgrade tokamak-plasma's wordt een vertakt MHD-evenwicht gereconstrueerd met de vorming van een 3D-spiraalvormige kern en de asymmetrische 2D-mantel. Alfvén continuümberekeningen met de vertakte evenwichten leiden tot de frequentiesplitsing tussen de continua van de hoogste frequentietak en de laagste frequentietak en het verschuiven van modi met aangrenzend n continuüm rond het frequentieaccumulatiepunt.
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Häußler, André [Verfasser], and R. [Akademischer Betreuer] Stieglitz. "Computational approaches for nuclear design analyses of the stellarator power reactor HELIAS / André Häußler ; Betreuer: R. Stieglitz." Karlsruhe : KIT-Bibliothek, 2020. http://d-nb.info/1219577928/34.

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Books on the topic "Stellarator"

1

Wakatani, Masahiro. Stellarator and heliotron devices. New York: Oxford University Press, 1998.

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Confinement of Non-neutral Plasmas in Stellarator Magnetic Surfaces. [New York, N.Y.?]: [publisher not identified], 2011.

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Heating and stability of Columbia Neutral Torus stellarator plasmas. [New York, N.Y.?]: [publisher not identified], 2017.

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M, Kovrizhnykh L., ed. Stellaratory: Sbornik nauchnykh trudov. Moskva: Nauka, 1991.

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Ng, Kam-Chuen. Magnetic surfaces and neoclassical transport in stellarators. New York: Courant Institute of Mathematical Sciences, Magneto-Fluid Dynamics Division, 1987.

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Ng, Kam-Chuen. Magnetic surfaces and neoclassical transport in stellarators. New York: Courant Institute of Mathematical Sciences, New York University, 1987.

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Y, Ueda, Purazuma Kakuyūgō Gakkai, International Stellarator Conference (11th : 1997 : Toki-shi, Japan), and International Toki Conference on Plasma Physics and Controlled Nuclear Fusion (8th : 1997), eds. Helical system research: Proceedings of joint conference of 11th International Stellarator Conference (ISC-11) & 8th International Toki Conference on Plasma Physics and Controlled Nuclear Fusion (ITC-8) : September 29-October 3,1997, Toki-city, Japan. Nagoya, Japan: Japan Society of Plasma Science and NuclearFusion Fusion Research, 1998.

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United States. Department of Energy. Fusion Energy Sciences Advisory Committee. NCSX Review Committee. Report of the NCSX Review Committee. Gaithersburg, Md: U.S. Dept. of Energy, Office of Science, 2007.

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European Conference on Controlled Fusion and Plasma Heating (13th 1986 Schliersee, Germany). 13th European Conference on Controlled Fusion and Plasma Heating, Schliersee, 14-18 April 1986: Contributed papers. Edited by Briffod G, Kaufmann M, and European Physical Society. Geneva: European Physical Society, 1986.

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Voronov, G. S. Shturm termoi͡a︡dernoĭ kreposti. Moskva: Izd-vo "Nauka," Glav. red. fiziko-matematicheskoĭ lit-ry, 1985.

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Book chapters on the topic "Stellarator"

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Miyamoto, Kenro. "Stellarator." In Plasma Physics for Controlled Fusion, 403–22. Berlin, Heidelberg: Springer Berlin Heidelberg, 2016. http://dx.doi.org/10.1007/978-3-662-49781-4_17.

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Hartfuss, H. J. "Diagnostic System for the W7-X Stellarator." In Advanced Diagnostics for Magnetic and Inertial Fusion, 371–74. Boston, MA: Springer US, 2002. http://dx.doi.org/10.1007/978-1-4419-8696-2_66.

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Werner, A., D. S. Darrow, R. Kuduk, and A. Weller. "Fast Ion Loss Diagnostic for the Wendelstein 7-X Stellarator." In Advanced Diagnostics for Magnetic and Inertial Fusion, 137–40. Boston, MA: Springer US, 2002. http://dx.doi.org/10.1007/978-1-4419-8696-2_22.

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Volpe, Francesco, and Heinrich P. Laqua. "Electron Bernstein Emission Diagnostic of Electron Temperature Profiles at W7-AS Stellarator." In Advanced Diagnostics for Magnetic and Inertial Fusion, 347–54. Boston, MA: Springer US, 2002. http://dx.doi.org/10.1007/978-1-4419-8696-2_63.

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Morse, Edward. "Stellarators." In Graduate Texts in Physics, 215–35. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-98171-0_8.

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Jiménez, Diego, Luis Campos-Duarte, Ricardo Solano-Piedra, Luis Alonso Araya-Solano, Esteban Meneses, and Iván Vargas. "BS-SOLCTRA: Towards a Parallel Magnetic Plasma Confinement Simulation Framework for Modular Stellarator Devices." In Communications in Computer and Information Science, 33–48. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-41005-6_3.

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Reinders, L. J. "Stellarators and Other Alternative Approaches." In Sun in a Bottle?... Pie in the Sky!, 187–200. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-74734-3_14.

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de Bustos Molina, Andrés. "Simulations of Fast Ions in Stellarators." In Kinetic Simulations of Ion Transport in Fusion Devices, 63–95. Cham: Springer International Publishing, 2013. http://dx.doi.org/10.1007/978-3-319-00422-8_4.

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Pustovitov, V. D., and V. D. Shafranov. "Equilibrium and Stability of Plasmas in Stellarators." In Reviews of Plasma Physics, 163–326. Boston, MA: Springer US, 1990. http://dx.doi.org/10.1007/978-1-4615-7784-3_3.

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Pustovitov, V. D. "Theoretical Principles of the Plasma-Equilibrium Control in Stellarators." In Reviews of Plasma Physics, 1–201. Boston, MA: Springer US, 2000. http://dx.doi.org/10.1007/978-1-4615-4309-1_1.

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Conference papers on the topic "Stellarator"

1

Palumbo, D., Olivier Sauter, Xavier Garbet, and Elio Sindoni. "Vacuum stellarator: direct approach." In THEORY OF FUSION PLASMAS. AIP, 2008. http://dx.doi.org/10.1063/1.3033719.

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NAGASAKI, K., G. MOTOJIMA, A. FERNANDEZ, A. CAPPA, J. M. FONTDECABA, Y. YOSHIMURA, T. NOTAKE, et al. "ECCD EXPERIMENTS IN STELLARATOR/HELIOTRON." In Proceedings of the 15th Joint Workshop. WORLD SCIENTIFIC, 2009. http://dx.doi.org/10.1142/9789812814647_0016.

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Neilson, G. H., D. A. Gates, P. J. Heitzenroeder, S. C. Prager, T. Stevenson, P. Titus, M. D. Williams, and M. C. Zarnstorff. "Facilities for quasi-axisymmetric stellarator research." In 2013 IEEE 25th Symposium on Fusion Engineering (SOFE). IEEE, 2013. http://dx.doi.org/10.1109/sofe.2013.6635336.

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Svidzinski, V. A., and D. G. Swanson. "Fundamental heating with stellarator wave modes." In The twelfth topical conference on radio frequency power in plasmas. AIP, 1997. http://dx.doi.org/10.1063/1.53385.

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Sárközi, J., K. Grosser, G. Kocsis, R. König, U. Neuner, Á Molnár, G. Petravich, et al. "Video Diagnostic for W7-X Stellarator." In PLASMA 2007: International Conference on Research and Applications of Plasmas; 4th German-Polish Conference on Plasma Diagnostics for Fusion and Applications; 6th French-Polish Seminar on Thermal Plasma in Space and Laboratory. AIP, 2008. http://dx.doi.org/10.1063/1.2909102.

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Otte, M., D. Andruczyk, E. Holzhauer, J. Howard, R. König, L. Krupnik, H. P. Laqua, et al. "The WEGA Stellarator: Results and Prospects." In PLASMA 2007: International Conference on Research and Applications of Plasmas; 4th German-Polish Conference on Plasma Diagnostics for Fusion and Applications; 6th French-Polish Seminar on Thermal Plasma in Space and Laboratory. AIP, 2008. http://dx.doi.org/10.1063/1.2909160.

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Clark, A. W., F. A. Volpe, and D. A. Spong. "Proto-CIRCUS tilted-coil tokamak-stellarator hybrid." In 2013 IEEE 25th Symposium on Fusion Engineering (SOFE). IEEE, 2013. http://dx.doi.org/10.1109/sofe.2013.6635516.

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Hurd, F. "Assembly Technology for the W7-X Stellarator." In 21st IEEE/NPS Symposium on Fusion Engineering SOFE 05. IEEE, 2005. http://dx.doi.org/10.1109/fusion.2005.252884.

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Hurd, F. H. "Assembly Status of the W7-X Stellarator." In 2007 IEEE 22nd Symposium on Fusion Engineering. IEEE, 2007. http://dx.doi.org/10.1109/fusion.2007.4337864.

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Brown, T., L. Bromberg, and M. Cole. "Results of Compact Stellarator engineering trade studies." In 2009 23rd IEEE/NPSS Symposium on Fusion Engineering - SOFE. IEEE, 2009. http://dx.doi.org/10.1109/fusion.2009.5226447.

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Reports on the topic "Stellarator"

1

Moroz, P. E. Stellarator-Spheromak. Office of Scientific and Technical Information (OSTI), March 1997. http://dx.doi.org/10.2172/491574.

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Hitchon, W. N. G. Stellarator Transport Theory. Office of Scientific and Technical Information (OSTI), January 1989. http://dx.doi.org/10.2172/5911932.

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Lyon, J. F., G. Grieger, F. Rau, A. Iiyoshi, A. P. Navarro, L. M. Kovrizhnykh, and O. S. Pavlichenko. Stellarator status, 1989. Office of Scientific and Technical Information (OSTI), July 1990. http://dx.doi.org/10.2172/6691089.

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Moroz, P. E. Double-helix stellarator. Office of Scientific and Technical Information (OSTI), September 1997. http://dx.doi.org/10.2172/537394.

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Beidler, C. D., and W. N. G. Hitchon. Ripple transport in Helical-Axis Advanced Stellarators: A comparison with classical stellarator/torsatrons. Office of Scientific and Technical Information (OSTI), July 1995. http://dx.doi.org/10.2172/93468.

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Koniges, A. E., and J. L. Johnson. Helical axis stellarator equilibrium model. Office of Scientific and Technical Information (OSTI), February 1985. http://dx.doi.org/10.2172/6117137.

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Painter, S. L., and J. F. Lyon. Transport analysis of stellarator reactors. Office of Scientific and Technical Information (OSTI), February 1991. http://dx.doi.org/10.2172/6134428.

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H.E. Mynick, P. Xanthopoulos and A. H. Boozer. Geometry Dependence of Stellarator Turbulence. Office of Scientific and Technical Information (OSTI), August 2009. http://dx.doi.org/10.2172/962141.

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Hitchon, W. N. G., and H. E. Mynick. Numerical study of stellarator transport. Office of Scientific and Technical Information (OSTI), May 1986. http://dx.doi.org/10.2172/5851490.

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Persson, M., M. Nadeem, J. L. V. Lewandowski, and H. J. Gardner. Drift waves in stellarator geometry. Office of Scientific and Technical Information (OSTI), February 2000. http://dx.doi.org/10.2172/751423.

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