Confinement in Mixed Isotope Plasmas with Constant ELM Frequency in JET-ILW

Over recent years a series of dedicated experiments have been performed on JET to study the effect of plasma isotope on plasma parameters in an ITER-like wall. These experiments have included plasmas with a single main isotope of H, D or T and mixtures such as HD, HT and ultimately DT. The effective mass of the plasma can have several different effects on plasma parameters e.g., confinement, L-H transition power and ELM frequency.



Variations of isotope mixture from H to D were performed in type I ELMy H-mode plasmas of the same magnetic field, plasma current and divertor configuration. These variations were performed with and without the use of ELM-control via the perturbation of the vertical magnetic field. This was included as an attempt to separate the effects of f_ELM from the isotope effect on pedestal confinement.



A clear increase in plasma stored energy was observed with increasing effective mass, in cases with and without external control of ELMs. This increase was driven by an increase in plasma density driven by the pedestal density. For plasmas that used vertical kicks the plasma thermal stored energy (W_th) varied as ~M_eff^0.7. Results in a HT mixture matched the results in a HD mixture with the same M_eff. Further results in pure tritium proved more difficult to include in the dataset due to changes in the access to H-mode, impurity behaviour and density peaking. This scaling analysis, variation of Ti/Te, tritium behaviour and the results at constant b_N will be presented.