13.6 - Cold cathodes for He-Ne gas lasers

Lifetimes of 18 000 hours have been achieved for He-Ne gas discharge tubes with aluminum cold cathodes, a current of 5mA, a gas volume of 42 cm³and an initial pressure of 3.15 torr. Larger versions using a gas volume of 110 cm³and an initial pressure of 1.54 torr are exceeding 5000 hours at 20 mA.