CNR ExploRA

Articolo in rivista, 2021, ENG, 10.1038/s41586-021-03687-w

Demonstration of reduced neoclassical energy transport in Wendelstein 7-X

Beidler C.D.; Smith H.M.; Alonso A.; Andreeva T.; Baldzuhn J.; Beurskens M.N.A.; Borchardt M.; Bozhenkov S.A.; Brunner K.J.; Damm H.; Drevlak M.; Ford O.P.; Fuchert G.; Geiger J.; Helander P.; Hergenhahn U.; Hirsch M.; Hofel U.; Kazakov Y.O.; Kleiber R.; Krychowiak M.; Kwak S.; Langenberg A.; Laqua H.P.; Neuner U.; Pablant N.A.; Pasch E.; Pavone A.; Pedersen T.S.; Rahbarnia K.; Schilling J.; Scott E.R.; Stange T.; Svensson J.; Thomsen H.; Turkin Y.; Warmer F.; Wolf R.C.; Zhang D.; Abramovic I.; Akaslompolo S.; Alcuson J.; Aleynikov P.; Aleynikova K.; Ali A.; Alonso A.; Anda G.; Ascasibar E.; Bahner J.P.; Baek S.G.; Balden M.; Banduch M.; Barbui T.; Behr W.; Benndorf A.; Biedermann C.; Biel W.; Blackwell B.; Blanco E.; Blatzheim M.; Ballinger S.; Bluhm T.; Bockenhoff D.; Boswirth B.; Bottger L.-G.; Borsuk V.; Boscary J.; Bosch H.-S.; Brakel R.; Brand H.; Brandt C.; Brauer T.; Braune H.; Brezinsek S.; Brunner K.-J.; Burhenn R.; Bussiahn R.; Buttenschon B.; Bykov V.; Cai J.; Calvo I.; Cannas B.; Cappa A.; Carls A.; Carraro L.; Carvalho B.; Castejon F.; Charl A.; Chaudhary N.; Chauvin D.; Chernyshev F.; Cianciosa M.; Citarella R.; Claps G.; Coenen J.; Cole M.; Cole M.J.; Cordella F.; Cseh G.; Czarnecka A.; Czerski K.; Czerwinski M.; Czymek G.; da Molin A.; da Silva A.; de la Pena A.; Degenkolbe S.; Dhard C.P.; Dibon M.; Dinklage A.; Dittmar T.; Drewelow P.; Drews P.; Durodie F.; Edlund E.; Effenberg F.; Ehrke G.; Elgeti S.; Endler M.; Ennis D.; Esteban H.; Estrada T.; Fellinger J.; Feng Y.; Flom E.; Fernandes H.; Fietz W.H.; Figacz W.; Fontdecaba J.; Fornal T.; Frerichs H.; Freund A.; Funaba T.; Galkowski A.; Gantenbein G.; Gao Y.; Garcia Regana J.; Gates D.; Geiger B.; Giannella V.; Gogoleva A.; Goncalves B.; Goriaev A.; Gradic D.; Grahl M.; Green J.; Greuner H.; Grosman A.; Grote H.; Gruca M.; Grulke O.; Guerard C.; Hacker P.; Han X.; Harris J.H.; Hartmann D.; Hathiramani D.; Hein B.; Heinemann B.; Helander P.; Henneberg S.; Henkel M.; Hergenhahn U.; Hernandez Sanchez J.; Hidalgo C.; Hollfeld K.P.; Holting A.; Hoschen D.; Houry M.; Howard J.; Huang X.; Huang Z.; Hubeny M.; Huber M.; Hunger H.; Ida K.; Ilkei T.; Illy S.; Israeli B.; Jablonski S.; Jakubowski M.; Jelonnek J.; Jenzsch H.; Jesche T.; Jia M.; Junghanns P.; Kacmarczyk J.; Kallmeyer J.-P.; Kamionka U.; Kasahara H.; Kasparek W.; Kenmochi N.; Killer C.; Kirschner A.; Klinger T.; Knauer J.; Knaup M.; Knieps A.; Kobarg T.; Kocsis G.; Kochl F.; Kolesnichenko Y.; Konies A.; Konig R.; Kornejew P.; Koschinsky J.-P.; Koster F.; Kramer M.; Krampitz R.; Kramer-Flecken A.; Krawczyk N.; Kremeyer T.; Krom J.; Ksiazek I.; Kubkowska M.; Kuhner G.; Kurki-Suonio T.; Kurz P.A.; Landreman M.; Lang P.; Lang R.; Langish S.; Laqua H.; Laube R.; Lazerson S.; Lechte C.; Lennartz M.; Leonhardt W.; Li C.; Li C.; Li Y.; Liang Y.; Linsmeier C.; Liu S.; Lobsien J.-F.; Loesser D.; Loizu Cisquella J.; Lore J.; Lorenz A.; Losert M.; Lucke A.; Lumsdaine A.; Lutsenko V.; Maassberg H.; Marchuk O.; Matthew J.H.; Marsen S.; Marushchenko M.; Masuzaki S.; Maurer D.; Mayer M.; McCarthy K.; McNeely P.; Meier A.; Mellein D.; Mendelevitch B.; Mertens P.; Mikkelsen D.; Mishchenko A.; Missal B.; Mittelstaedt J.; Mizuuchi T.; Mollen A.; Moncada V.; Monnich T.; Morisaki T.; Moseev D.; Murakami S.; Nafradi G.; Nagel M.; Naujoks D.; Neilson H.; Neu R.; Neubauer O.; Ngo T.; Nicolai D.; Nielsen S.K.; Niemann H.; Nishizawa T.; Nocentini R.; Nuhrenberg C.; Nuhrenberg J.; Obermayer S.; Offermanns G.; Ogawa K.; Olmanns J.; Ongena J.; Oosterbeek J.W.; Orozco G.; Otte M.; Pacios Rodriguez L.; Panadero N.; Panadero Alvarez N.; Papenfuss D.; Paqay S.; Pawelec E.; Pedersen T.S.; Pelka G.; Perseo V.; Peterson B.; Pilopp D.; Pingel S.; Pisano F.; Plaum B.; Plunk G.; Poloskei P.; Porkolab M.; Proll J.; Puiatti M.-E.; Puig Sitjes A.; Purps F.; Rack M.; Recsei S.; Reiman A.; Reimold F.; Reiter D.; Remppel F.; Renard S.; Riedl R.; Riemann J.; Risse K.; Rohde V.; Rohlinger H.; Rome M.; Rondeshagen D.; Rong P.; Roth B.; Rudischhauser L.; Rummel K.; Rummel T.; Runov A.; Rust N.; Ryc L.; Ryosuke S.; Sakamoto R.; Salewski M.; Samartsev A.; Sanchez M.; Sano F.; Satake S.; Schacht J.; Satheeswaran G.; Schauer F.; Scherer T.; Schlaich A.; Schlisio G.; Schluck F.; Schluter K.-H.; Schmitt J.; Schmitz H.; Schmitz O.; Schmuck S.; Schneider M.; Schneider W.; Scholz P.; Schrittwieser R.; Schroder M.; Schroder T.; Schroeder R.; Schumacher H.; Schweer B.; Sereda S.; Shanahan B.; Sibilia M.; Sinha P.; Siplia S.; Slaby C.; Sleczka M.; Spiess W.; Spong D.A.; Spring A.; Stadler R.; Stejner M.; Stephey L.; Stridde U.; Suzuki C.; Szabo V.; Szabolics T.; Szepesi T.; Szokefalvi-Nagy Z.; Tamura N.; Tancetti A.; Terry J.; Thomas J.; Thumm M.; Travere J.M.; Traverso P.; Tretter J.; Trimino Mora H.; Tsuchiya H.; Tsujimura T.; Tulipan S.; Unterberg B.; Vakulchyk I.; Valet S.; Vano L.; van Eeten P.; van Milligen B.; van Vuuren A.J.; Vela L.; Velasco J.-L.; Vergote M.; Vervier M.; Vianello N.; Viebke H.; Vilbrandt R.; von Stechow A.; Vorkoper A.; Wadle S.; Wagner F.; Wang E.; Wang N.; Wang Z.; Wauters T.; Wegener L.; Weggen J.; Wegner T.; Wei Y.; Weir G.; Wendorf J.; Wenzel U.; Werner A.; White A.; Wiegel B.; Wilde F.; Windisch T.; Winkler M.; Winter A.; Winters V.; Wolf S.; Wolf R.C.; Wright A.; Wurden G.; Xanthopoulos P.; Yamada H.; Yamada I.; Yasuhara R.; Yokoyama M.; Zanini M.; Zarnstorff M.; Zeitler A.; Zhang H.; Zhu J.; Zilker M.; Zocco A.; Zoletnik S.; Zuin M.

Max-Planck-Institut für Plasmaphysik, Greifswald, Germany; Laboratorio Nacional de Fusion, CIEMAT, Madrid, Spain; Laboratory for Plasma Physics (LPP), École royale militaire/Koninklijke Militaire School (ERM/KMS), Brussels, Belgium; Princeton Plasma Physics Laboratory, Princeton, NJ, USA; Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin, Germany; Wigner Research Centre for Physics, Budapest, Hungary; Massachusetts Institute of Technology, Cambridge, MA, USA; Max Planck Institute for Plasma Physics, Garching, Germany; University of Wisconsin Madison, Madison, WI, USA; Institute for Energy and Climate Research - Plasma Physics, Research Center Jülich, Germany; The Australian National University, Canberra, ACT, Australia; Technical University of Denmark, Kongens Lyngby, Denmark; Eindhoven University of Technology, Eindhoven, Netherlands; University of Cagliary, Cagliari, Italy; Consorzio RFX (CNR, ENEA, INFN, Università di Padova, Acciaierie Venete SpA), Padova, Italy; CNR ISTP - Istituto per la Scienza e Tecnologia dei Plasmi - Sede secondaria di Padova, Italy; Instituto de Plasmas e Fusao Nuclear, Lisbon, Portugal; CEA Cadarache, Saint-Paul-lez-Durance, France; Ioffe Physical-Technical Institute of the Russian Academy of Sciences, St Petersburg, Russian Federation; Oak Ridge National Laboratory, Oak Ridge, TN, USA; University of Salerno, Fisciano, Italy; ENEA Centro Ricerche Frascati, Frascati, Italy; Institute of Plasma Physics and Laser Microfusion, Warsaw, Poland; University of Szczecin, Poland; University of Milano-Bicocca, Milan, Italy; Auburn University, Auburn, AL, USA; Karlsruhe Institute of Technology, Eggenstein-Leopoldshafen, Germany; National Institute for Fusion Science, Toki, Japan; Universidad Carlos III de Madrid, Madrid, Spain; Greifswald University, Germany; Institute for Surface Process Engineering and Plasma Technology, University of Stuttgart, Germany; Austrian Academy of Science, Vienna, Austria; Institute for Nuclear Research, Kiev, Institute for Nuclear Research, Kiev, Ukraine; Technical University of Berlin, Germany; University of Opole, Poland; Aalto University, Espoo, Finland; University of Maryland, College Park, MA, USA; Physikalisch Technische Bundesanstalt (PTB), Braunschweig, Germany; Kyoto University, Kyoto, Japan; CNR ISTP, Istituto per la Scienza e Tecnologia dei Plasmi, Milano, Italy; Culham Centre for Fusion Energy, Abingdon, United Kingdom; Los Alamos National Laboratory, Los Alamos, NM, USA.

Research 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.

Nature (Basingstoke, Online) 596 (7871), pp. 221–226