A grid controlled cold cathode visual indicator

This paper describes the construction and characteristics of a novel grid controlled cold cathode visual indicator in a T-2 bulb designed for use with transistors. The tube has a keep-alive cathode and a perforated keep-alive anode located at the start of the positive column. Electrons emerging from holes in the anode have an energy of 1 electron volt or less so that -2 volts between a control grid and the keep-alive anode is sufficient to cut off the flow. The main cathode is made of zirconium to reduce sputtering and is planar with a small hole to allow the electrons to enter the main discharge region to initiate the discharge. The main anode is the last electrode in the linear array and is made of wire to minimize obstruction of the light from the negative glow dose to the cathode. A relaxation circuit is used to supply the keep-alive discharge with heavy bursts of current for efficient triggering of the main discharge. Reset is automatically accomplished when a half-wave rectified power supply is used. The lamp was designed for end viewing and an average keep-alive current of 17 microamperes is supplied by a 250 volt supply.