A camera tube with NEA cold cathode

The GaP NEA cold cathode was used in a noncrossover type of electron gun mounted in a camera tube with a photoconductive amorphous selenium target. Sufficient beam current to operate the camera tube was obtained by passing a forward-bias current of several milliamperes in through the p-n junction. The equivalent beam temperature measured from the beam acceptance curve was about 600 K. This resulted in a considerably reduced capacitive lag at low light levels. At a signal current of 25 nA, the rise and decay lags of a 1-in tube were 90 and 12 percent, respectively, at the third field after turning on or off of the fight. Using a cold cathode with an electron-emitting area 50 µm in diameter, a horizontal limiting resolution of 800 TV lines was obtained at the center and high-quality images with good gradation were reproduced.