Fluoresent lamp with double cathode and probe

A fluorescent lamp of the type having a sealed envelope with a phosphor coating on an internal wall thereof and having an electrode at each end adapted to receive current from an external current source and an ionizable medium for supporting an electron arc stream therein between said electrode, wherein at least one of said electrodes comprises:

• first cathode means having first and second ends adapted to be electrically connected to two active leads of said external current source for emitting electrons resonsive to an electric current received from said external source;
• second cathode means having first and second ends for emitting electrons responsive to an electric current, said second cathode means first end being electrically connected to said first cathode means first end and thereby adapting it to be connected to one active lead of said external current source and its second end left unconnected;
• and
• electron collecting means electrically connected to said second cathode means second end and extending outwardly from said second cathode means toward the electrode at the other end of the envelope and into the electron arc stream for capturing electrons from said arc stream and supplying the electric current resulting therefrom to said second cathode means, said electron collecting means collecting electrons in an amount of sufficient current to induce thermionic heating of said second cathode means to cause it to emit electrons such that at least a part of the production of said electron arc stream transfers from said first to said second cathode means.