Overview of JET results for optimising ITER operation

Abstract

The JET 2019-2020 scientific and technological programme exploited the results of years of concerted scientific and engineering work, including the ITER-like wall (ILW: Be wall and W divertor) installed in 2010, improved diagnostic capabilities now fully available, a major Neutral Beam Injection (NBI) upgrade providing record power in 2019-2020, and tested the technical & procedural preparation for safe operation with tritium. Research along three complementary axes yielded a wealth of new results. Firstly, the JET plasma programme delivered scenarios suitable for high fusion power and alpha particle physics in the coming D-T campaign (DTE2), with record sustained neutron rates, as well as plasmas for clarifying the impact of isotope mass on plasma core, edge and plasma-wall interactions, and for ITER pre-fusion power operation. The efficacy of the newly installed Shattered Pellet Injector for mitigating disruption forces and runaway electrons was demonstrated. Secondly, research on the consequences of long-term exposure to JET-ILW plasma was completed, with emphasis on wall damage and fuel retention, and with analyses of wall materials and dust particles that will help validate assumptions and codes for design & operation of ITER and DEMO. Thirdly, the nuclear technology programme aiming to deliver maximum technological return from operations in D, T and D-T benefited from the highest D-D neutron yield in years, securing results for validating radiation transport and activation codes, and nuclear data for ITER.

Fusion power predictions for β N ≈ 1.8 baseline scenario with 50–50 D–T fuel mix and NBI injection in preparation to D–T operations at JET

“…The pulses considered are JET pulses 42464 and 42982. Both plasmas have I p = 3.8 MA, B T = 3.8 T, a C plasma facing wall (and, consequently a different impurity mix with respect to the references modelled in the previous section) and use a 3 He minority ICRH heating scheme (as opposed to the H minority scheme used in the shots described in the previous section). Shot 42464 is a pure D plasma, whereas shot 42982 is a 50-50 DT plasma.…”

“…The same modelling procedure described in the previous section is applied and the comparison between experiment and simulation results are shown in figures 10 and 11 for shot 42464 and figures 12 and 13 for shot 42982. Note that in these simulations we assumed a nominal 3 He concentration of ≈5%, considered C as the only other impurity contributing to Z eff in the plasma and adjusted its concentration to match the experimental Z eff value (inferred from Bremsstrahlung measurements). This resulted in n C / n e ≈ 3.9% for shot 42464 and n C / n e ≈ 5.6% for shot 42982.…”

“…In preparation to DTE2, experiments have been performed on JET to prepare the plasma scenarios in D, which will be used in DTE2 [2][3][4]. Two scenarios are being developed: the baseline scenario where the confinement is achieved at high plasma current (I p 3.5 MA) and medium normalized beta (β N ≈ 1.8), and the hybrid scenario, which relies on lower plasma current (I p 2.5 MA) and higher normalized beta (β N ≈ 2-3) to achieve good confinement.…”

Towards a fusion power plant: integration of physics and technology

“…In both cases the performance was found to drop substantially (primarily due to changes in the pedestal from the enforced operating regime to avoid melting divertor components)-this was unpredicted and not addressed in scalings (which do not include edge atomic physics and neutral penetration effects). However, intense experimental and model-based optimisation over a number of years has recovered reliable high performance on AUG [33,34], and removed the deficit and indeed exceeded the carbonwall performance in JET [35]. As with many plasma optimisations, it is also found that the time sequence within the discharge is critical, i.e.…”

Frontiers in the Application of RF Vacuum Electronics

“…injected into the plasma) with the best results achieved in the Joint European Tokamak (JET) [79]. The larger device International Thermonuclear Experimental Reactor (ITER) [80] aims at a tenfold increase (Q = 10), but the device, though expected to validate some key concepts needed for commercial viability, is experimental and does not attempt to generate electricity.…”