Bulletin of the American Physical Society
64th Annual Meeting of the APS Division of Plasma Physics
Volume 67, Number 15
Monday–Friday, October 17–21, 2022; Spokane, Washington
Session BI01: Magnetic Confinement Fusion ILive Streamed
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Chair: Andrea Garofalo, General Atomics Room: Ballroom 100 A |
Monday, October 17, 2022 9:30AM - 10:00AM |
BI01.00001: Overview of deuterium-tritium results from JET-ILW experiments Invited Speaker: Elena De La Luna JET has recently completed the first deuterium-tritium (D-T) campaign in a tokamak since 1997, and for the first time ever with ITER-like W/Be divertor and first wall materials. Scientific results include demonstration of high (average Pfus>10 MW) sustained fusion power for 5 s, demonstration of an integrated radiative scenario, demonstration of clear alpha particle effects, exploration of isotope and mixed plasma species effects on energy and particle transport, addressing plasma-wall interaction in D-T plasmas, and demonstration of RF schemes relevant to ITER D-T operation. Highlights include achievement of 42 MJ fusion energy production in a 50/50 D-T plasma pulse and 59 MJ in a deuterium-NBI heated tritium-rich pulse, both surpassing the 1997 record of 22 MJ and demonstrating the compatibility of the ILW with sustained fusion performance. The dependence of Pfus on input power was consistent with pre-experiment predictions, validating predictive capabilities. An integrated scenario with Ne seeding was demonstrated for the first time in D-T with the ILW, with detached divertor conditions and improved energy confinement over reference unseeded plasmas, confirming Ne as a promising radiator for ITER. Improved diagnostics compared to 1997 show variation of pedestal structure depending on D-T fuel mix, with a clear increase in pedestal density and pressure with increasing tritium concentration. Expected increase in erosion observed due to heavier tritium ions, but plasma impurity levels remained tolerable. Alpha-driven modes at Alfvénic frequencies are observed in an afterglow phase with no NBI heating. Efficient core heating demonstrated with 3-ion D-9Be-T RF scheme. |
Monday, October 17, 2022 10:00AM - 10:30AM |
BI01.00002: Sustained high fusion power production with the hybrid scenario in the recent JET D-T campaign Invited Speaker: Athina Kappatou In the recent JET D-T experiments, ‘hybrid’ scenario plasmas with Ip=2.3MA and a current overshoot, Bt=3.45T, βp>1, q0≥1 and nD~nT fuel mixture delivered sustained high D-T fusion power, with a time average over 5sec up to ~8.3MW. The fusion power and gain achieved with the ‘hybrid’ scenario, for the first time operated in D-T, are higher with respect to those obtained in steady ELMy H-mode plasmas in the previous D-T campaign in 1997, and now with the metal ITER-like wall. Very high fusion power >10MW could be maintained for periods longer than 3 α-particle slowing-down times. |
Monday, October 17, 2022 10:30AM - 11:00AM |
BI01.00003: T-rich scenario for the record fusion energy plasma in JET DT Invited Speaker: Mikhail Maslov One of the main goals of the recent JET DT experimental campaign with ITER-like wall was to achieve high fusion power >10MW steady for 5 seconds. Scenarios developed for that purpose were utilizing close to 50/50 DT plasma mixture and balanced D-NBI and T-NBI injected heating power. |
Monday, October 17, 2022 11:00AM - 11:30AM |
BI01.00004: Fast ions as a tool for plasma control and enhanced performance on JET Invited Speaker: Yevgen Kazakov High-energy alpha particles will be the main source of plasma heating in ITER and future fusion reactors. Extrapolating the performance of plasmas with dominant alpha particle heating is not straightforward [1]. Indeed, MeV-range alphas can simultaneously destabilize Alfvén eigenmodes (AEs), impact the sawtooth dynamics, modify plasma equilibrium etc., altogether defining the resulting plasma performance [2]. |
Monday, October 17, 2022 11:30AM - 12:00PM |
BI01.00005: Influence of energetic particle profiles on DIII-D high bootstrap fraction plasmas Invited Speaker: Kathreen E Thome Broadening the energetic particle profile in a high bootstrap fraction (~60%), noninductive DIII-D plasma significantly lowers anomalous fast-ion transport and broadens plasma profiles, which is desirable for maintaining the elevated-qmin scenario in steady-state. An upgraded capability allows DIII-D to inject up to half of its neutral beams off-axis, and understanding the stability and transport differences between on-axis injection with a peaked fast-ion profile and 50% off-axis injection with a broad fast-ion profile informs the development of a steady-state burning plasma. Elevated-qmin discharges with only on-axis beams have strong Alfvén eigenmode activity and high anomalous fast-ion transport, whereas steering 50% of the beams off-axis decreases both of these, and results in broader fast-ion profiles, more consistent with classical predictions. Plasmas with off-axis beams also have a broader current profile and higher neutral beam current drive, due to the reduced fast-ion activity, even with less off-axis electron cyclotron current drive. In both cases qmin is slowly decreasing throughout the high-betaN phase from approximately 2 to 1.3, correlated with increasing fast-ion activity and decreasing plasma performance, especially for the on-axis beam case. These two types of plasmas have similar energy confinement time and transport levels; although, the electron density profile switches from highly-peaked to broad with 50% off-axis injection, which may be the source of the other plasma profiles broadening. While modeling shows off-axis beams give higher n=1 ideal-wall kink beta limits, these discharges have stronger and more frequent bursty n=1 and 3 energetic particle modes that often trigger tearing modes. Planned increases in RF power should reduce bursty mode drive and better sustain a high-qmin scenario. |
Monday, October 17, 2022 12:00PM - 12:30PM |
BI01.00006: Distinguishing electron driven from fast-ion driven Alfvénic instabilities Invited Speaker: William W Heidbrink Modes with frequencies below the toroidal Alfvén eigenmode (AE) are often unstable in existing toroidal plasmas and cause appreciable fast-ion transport, so understanding their stability is vital to predict their impact on alphas in future devices. Through experiment and theory, we now understand that fast ions play an important role in driving beta-induced AEs (BAE), while another mode, the recently identified low-frequency Alfvén mode (LFAM), relies on electron temperature Te. Reversed shear DIII-D plasmas with simultaneous neutral beam injection (NBI) and electron cyclotron heating (ECH) have unstable BAEs and LFAMs. The eigenfunctions of both modes peak near qmin but BAEs typically have higher frequencies and lower mode numbers [1,2]. The BAEs rapidly disappear when the NBI is notched off, then rapidly reappear when it resumes, demonstrating that BAEs are driven by resonances with high-energy fast ions [1]. In contrast, as long as Te is sustained, LFAMs persist throughout the beam notch and are even observed in high Te discharges without any NBI [2]. A large database shows that BAEs are more unstable in plasmas with beta poloidal βp>0.5 but LFAMs are unstable most often when Te>2.1 keV but βp is small. Theoretical analysis that identifies the LFAM as a reactive-type kinetic ballooning mode instability with dominant Alfvénic polarization successfully predicts all of the experimental properties [3], including stronger instability in hydrogen plasmas [4]. Gyrokinetic simulations [5] reproduce most but not all of the BAE and LFAM properties. Calculations of ITER stability are underway. |
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