The characteristics of a self-sustaining magnetically confined electron cloud under different electromagnetic fields and pressures are studied by means of the rf method and the charge collection method. The electron cloud has been obtained at lower background pressures by a cold-cathode Penning discharge. The electron density of the cloud increases with the applied voltage, and with the magnetic field as well, if the electron cloud is in the unsaturated state. The density of a saturated cloud is independent of the magnetic field. When the pressure exceeds a critical value the electron cloud will be transformed into a neutral plasma.