Alpha Particle Losses within JET's 2021/2022 DT-Campaign*

Alpha particle confinement is crucial for sustaining burning plasmas and designing future reactor concepts. Along with classical/prompt losses, various MHD instabilities can lead to wave-particle interactions which can transport alpha particles outward from the plasma. These processes are detrimental to plasma self-heating and require further study. Since prior experiments in the mid-90's, advances in experimentation, diagnostic capabilities, and numerical modeling tools have warranted renewed DT-operations. JET's 2021/2022 DT-campaign provided new opportunities for alpha particle experiments in ITER-like plasmas with state-of-the-art energetic particle diagnostics. This work will present alpha particle loss measurements from JET's Faraday cup fast ion loss detector array and scintillator probe with supporting measurements from neutron diagnostics. Losses from low frequency MHD activity are examined with comments on alpha transport, confinement, and heating in the bump-on tail distribution, "afterglow," and baseline scenarios. Alpha particle losses were recorded from both coherent (NTMs, kinks, fishbones, etc.) and non-coherent sources (ELMs and sawteeth). In particular, coherent losses with low frequency (<100 kHz) MHD were strongly observed. An estimate of the maximum alpha loss fraction was determined due to be ~5% from the coherent, low frequency, MHD activity, which could pose an issue for future reactors. Sensitivities to alpha energy, pitch, and spatial loss deposition were also observed. An interesting discharge exhibiting losses maximal in two regions of pitch-space is being examined for NTM induced ripple losses. Additionally, correlations with plasma shaping parameters, impurity concentrations, and fast ion orbit topology were conducted to assess shaping effects, wall interactions, and detector susceptibility. Lastly, comments on higher frequency toroidal Alfven eigenmode (TAE) induced alpha losses will be shared.