Gas inlets (10) introduce an ionizable inert gas to a gas outlet. Electrodes convey a coagulation flow from a high frequency source (16) into the gas. Flow devices (12-14) in the form of flow meters and regulators are arranged so that the ionizable gas completely fills a space between the electrodes and the biological tissue to be coagulated, free from laminar flow particles. The flow devices enable the ionizable gas to slowly displace the steam emerging from the biological tissue. The insulating effect of the steam protects the corresponding parts of the tissue from further action through the coagulation flow until the steam is displaced.
