The electron distribution function in a bumpy torus

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Abstract
New and improved diagnostic techniques and increased theoretical understanding of electron‐cyclotron heating (ECH) have led to a new picture of the electron distribution function in the ELMO Bumpy Torus (EBT). For electron energies ≤2 keV, the distribution function can be approximated as consisting of two components: a cold isotropic bulk component and a warm anisotropic tail. For typical steady‐state EBT‐Scale (EBT‐S) operation (microwave power input of 100 to 150 kW) in the T‐mode (the operating mode of interest for fusion experiments), bulk densities and temperatures of ne =0.5–0.7×1012 cm−3 and Te ≤100 eV are observed, while the warm tail component has Te =200–800 eV, and densities ≤0.4 that of the cold component. The non‐Maxwellian nature of the distribution function is caused by ECH.