Neon seeded ITER baseline scenario experiments in JET D and D-T plasmas

Carvalho, I. S.; Giroud, C.; King, D. B.; Keeling, D. L.; Frassinetti, L.; Pitts, R. A.; Wiesen, S.; Pucella, G.; Kappatou, A.; Vianello, N.; Wischmeier, M.; Rimini, F.; Baruzzo, M.; Maslov, M.; Sos, M.; Litaudon, X.; Henriques, R. B.; Kirov, K.; Perez von Thun, C.; Sun, H. J.; Lennholm, M.; Mitchell, J.; Parrot, A.; Bernardo, J.; Zerbini, M.; Coffey, I.; Collie, K.; Fontdecaba, J. M.; Hawkes, N.; Huang, Z.; Jepu, I.; Kos, D.; Lawson, K.; Litherland-Smith, E.; Meigs, A.; Olde, C.; Patel, A.; Piron, L.; Poradzinski, M. P.; Stancar, Z.; Taylor, D.; Alessi, E.; Balboa, I.; Boboc, A.; Bakes, S.; Brix, M.; De la Cal, E.; Carvalho, P.; Chomiczewska, A.; Ghani, Z.; Giovannozzi, E.; Foster, J.; Huber, A.; Karhunen, J.; Kowalska-Strzeciwilk, E.; Maddock, J.; Matthews, J.; Menmuir, S.; Mikszuta, K.; Morales-Bianchetti, R. B.; Pawelec, E.; Petravich, G.; Pinto, E.; Voldiner, I.; Sergienko, G.; Silburn, S.; Svodoba, J.; Tomes, M.; Thomas, B.; Tookey, A.; Zayachuk, Y.; Valovic, M.; Widdowson, A.; Xiang, L.; Auriemma, F.; Innocente, P.; Gabriellini, S.; Mariani, A.; Marin, M.; Predebon, I.; Thrysoe, A.; Zotta, V. K.

The ITER baseline scenario [1] defined as the first target for ITER deuterium-tritium (DT) operation consists on an inductive scenario at 15MA, 5.3T, high triangularity (≈0.45), q95≈3, Q=10 expected to be achieved with H98(y,2)=1, fGW=0.86, βp=0.86, and e,ped*=0.01 for a duration greater than 300s. The integrity of the divertor requires the heat load to be maintined below 10MW.m-2 , and for this, neon impurity seeding is required to achieve a partially detached divertor state. The challenge in achieving this integrated scenario in ITER is to reduce the power load whislt maintaining sufficient impurity compression at the divertor, and midplane in order to keep the impurity content in the core plasma within an acceptable limit for the required fusion gain. Over the past years, JET has carried out core-edge integration studies [2] dedicated to understand how the integrated scenario of ITER would work in the so-called JET ITER baseline plasmas with the following characteristics: high-triangularity (=0.35- 0.38), with divertor configuration with the inner and outer leg on the vertical targets, closer to the ITER divertor and optimal for better detachment, see figure 1. The previously best demonstration of an integrated ITER-baseline scenario with neon seeding at JET was obtained at 2.5MA/2.7T, H98(y,2) =0.9, N=2.2, av =0.37, fGW=0.7, frad=0.86, Zeff=2.7, PNBI=29MW, PICRH=5MW with deuterium (D) gas rate of 3.6x1022 el.s-1 and no ELMs (pulse #97490) [2][3]. Machine size and high temperature was demonstrated to be key to maintain impurities in the divertor where it is aimed for them to radiate [4][5][6]. Consequently, JET the closest tokamak in size to ITER amongst current devices is best positioned to address the core-edge integration issues. Although, we note that JET cannot reach the same neon compression, therefore, in semidetachment state some radiation is located near the x-point (see figure 5), unlike the expectations for ITER where most radiation is expected to be below x-point [5]. The core-edge integration was one of the main topics addressed in the last JET campaigns, where the aim was to demonstrate the robustness of the 2.5MA neon seeded scenario, push the pedestal collisionality to lower values (as reasonably possible given the machine size and not to compromise the remaining scenario parameters), to port the scenario to higher current (3MA and 3.2MA) and from D to DT operation. The aim of thisstudy not only to develop an integrated scenario for JET addressing issues faced by ITER but also to understand the key physics at play in this integration, how to achieve a high radiative divertor, its impact on the pedestal and overall confinement, as well as provide key data to improve modelling capabilities. This paper presents only the key highlights of the last JET campaign on this topic.

Neon seeded ITER baseline scenario experiments in JET D and D-T plasmas / Carvalho, I. S.; Giroud, C.; King, D. B.; Keeling, D. L.; Frassinetti, L.; Pitts, R. A.; Wiesen, S.; Pucella, G.; Kappatou, A.; Vianello, N.; Wischmeier, M.; Rimini, F.; Baruzzo, M.; Maslov, M.; Sos, M.; Litaudon, X.; Henriques, R. B.; Kirov, K.; Perez von Thun, C.; Sun, H. J.; Lennholm, M.; Mitchell, J.; Parrot, A.; Bernardo, J.; Zerbini, M.; Coffey, I.; Collie, K.; Fontdecaba, J. M.; Hawkes, N.; Huang, Z.; Jepu, I.; Kos, D.; Lawson, K.; Litherland-Smith, E.; Meigs, A.; Olde, C.; Patel, A.; Piron, L.; Poradzinski, M. P.; Stancar, Z.; Taylor, D.; Alessi, E.; Balboa, I.; Boboc, A.; Bakes, S.; Brix, M.; De la Cal, E.; Carvalho, P.; Chomiczewska, A.; Ghani, Z.; Giovannozzi, E.; Foster, J.; Huber, A.; Karhunen, J.; Kowalska-Strzeciwilk, E.; Maddock, J.; Matthews, J.; Menmuir, S.; Mikszuta, K.; Morales-Bianchetti, R. B.; Pawelec, E.; Petravich, G.; Pinto, E.; Voldiner, I.; Sergienko, G.; Silburn, S.; Svodoba, J.; Tomes, M.; Thomas, B.; Tookey, A.; Zayachuk, Y.; Valovic, M.; Widdowson, A.; Xiang, L.; Auriemma, F.; Innocente, P.; Gabriellini, S.; Mariani, A.; Marin, M.; Predebon, I.; Thrysoe, A.; Zotta, V. K.. - 48A:(2024), pp. 1-4. (Intervento presentato al convegno 50thEPS Conference on Controlled Fusion and Plasma Physics tenutosi a Salamanca, Spain).