Electron density and temperature profiles of the plasma produced by ECH in an axisymmetric mirror with an internal hoop are described. This mirror has a strong gradient in magnetic field intensity including a null-field separatrix ring on the midplane. The plasma stability in this MHD-stabilized magnetic field configuration is examined through measurements of the radial distribution of fluctuations appearing in the saturation current of Langmuir probes. The fluctuation was well suppressed in the MHD-stabilized region, satisfying either the absolute or averaged minimum-B condition. The electron density was peaked at the zero-field ring region on the separatrix flux surface. A stable plasma with an electron temperature of over 20 eV and isolated from the chamber wall was formed. A high-energy electron component was not observed.
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