CNR ExploRA

Articolo in rivista, 2022, ENG, 10.1088/1361-6587/ac48bc

Physics of runaway electrons with shattered pellet injection at JET

Reux, C.; Paz-Soldan, C.; Eidietis, N.; Lehnen, M.; Aleynikov, P.; Silburn, S.; Bandaru, V; Ficker, O.; Hoelzl, M.; Hollmann, E. M.; Jachmich, S.; Joffrin, E.; Lomas, P. J.; Rimini, F.; Baylor, L.; Bleasdale, A.; Calacci, L.; Causa, F.; Carnevale, D.; Coffey, I; Craven, D.; Dal Molin, A.; de la Luna, E.; De Tommasi, G.; Garcia, J.; Gebhart, T.; Giacomelli, L.; Huber, A.; Khilkevich, E.; Lowry, C.; Macusova, E.; Manzanares, A.; Nocente, M.; Panontin, E.; Papp, G.; Pautasso, G.; Peacock, A.; Plyusnin, V; Shevelev, A.; Shiraki, D.; Sommariva, C.; Sozzi, C.; Sridhar, S.; Sweeney, R.; Szepesi, G.; Tinguely, R. A.; Wilson, J.

CEA, IRFM, St Paul Les Durance, France; Gen Atom Co, San Diego, CA USA; Columbia Univ, Dept Appl Phys & Appl Math, New York, NY USA; ITER Org, St Paul Les Durance, France; Max Planck Inst Plasma Phys, Greifswald, Germany; Culham Sci Ctr, CCFE, Abingdon, Oxon, England; Max Planck Inst Plasma Phys, Garching, Germany; CAS, Inst Plasma Phys, Prague, Czech Republic; Univ Calif San Diego, La Jolla, CA USA; Oak Ridge Natl Lab, Oak Ridge, TN USA; Univ Roma Tor Vergata, Rome, Italy; ISTP CNR, Ist Sci & Tecnol Plasmi, Milan, Italy; Queens Univ, Sch Math & Phys, Belfast, Antrim, North Ireland; Univ Milano Bicocca, Milan, Italy; CIEMAT, Lab Nacl Fus, Madrid, Spain; Consorzio CREATE, Naples, Italy; Forschungszentrum Julich, Inst Energie & Klimaforsch, Julich, Germany; Ioffe Phys Tech Inst, St Petersburg, Russia; Univ Complutense Madrid, Madrid, Spain; European Commiss, Brussels, Belgium; Univ Lisbon, Inst Plasmas & Fusao Nucl, Inst Super Tecn, Lisbon, Portugal; Ecole Polytech Fed Lausanne EPFL, Swiss Plasma Ctr SPC, Lausanne, Switzerland; MIT, Plasma Sci & Fus Ctr, Cambridge, MA USA.

Runaway electrons (REs) created during tokamak disruptions pose a threat to the reliable operation of future larger machines. Experiments using shattered pellet injection (SPI) have been carried out at the JET tokamak to investigate ways to prevent their generation or suppress them if avoidance is not sufficient. Avoidance is possible if the SPI contains a sufficiently low fraction of high-Z material, or if it is fired early in advance of a disruption prone to runaway generation. These results are consistent with previous similar findings obtained with Massive Gas Injection. Suppression of an already accelerated beam is not efficient using High-Z material, but deuterium leads to harmless terminations without heat loads. This effect is due to the combination of a large magnetohydrodynamic instability scattering REs on a large area and the absence of runaway regeneration during the subsequent current collapse thanks to the flushing of high-Z impurities from the runaway companion plasma. This effect also works in situations where the runaway beam moves upwards and undergoes scraping-off on the wall.

Plasma physics and controlled fusion (Print) 64 (3), pp. 034002-1–034002-11