In the CIRCE experiment, the plasma is obtained by the trapping of a plasma injected into a magnetic bottle by electron heating at cyclotron resonance. The plasma density lies between 5×1011cm−3 and 1012cm−3, the electron temperature is about 100 keV and the ion temperature is in the range of few hundred electronvolts. Gross instabilities are not observed. The ratio of the plasma density to the neutral-gas density inside the plasma is higher than 100. A few kilowatts of r.f. power at 8 GHz are sufficient to obtain these results, a fact which looks encouraging as far as the creation of a more effective fast-neutraltarget plasma using the CIRCE-experiment concept is concerned.