Spiral accelerator
The spiral accelerator is a helical resistive coating on a cathode-ray tube designed to minimize beam compression in the post-deflection acceleration system by applying a gradually increasing acceleration voltage along the bulb's length.
It was first suggested in 1938 but not developed into a practical device.
In 1952, Howard Vollum revived the idea for the T51 CRT that Tektronix was developing for the 1953 model 535 scope.
The spiral accelerator displaced multi-band acceleration by the 1960s.