Use of the ASDEX divertor permits the production of stable low-density discharges ($n_e\gtrsim {10}^{12}$ ${\mathrm{cm}}^{-3\mathrm{}}$) with extremely low resistivity lasting for more than 10 s. While the distribution functions of electrons and ions show suprathermal tails, runaway electrons in the megaelectronvolt range are found to disappear with decreasing density. There are indications that in these discharges the energy confinement is improved compared with ALCATOR scaling.

• Received 20 July 1981

DOI:https://doi.org/10.1103/PhysRevLett.47.1004