Unidentified peripheral in Tektronix PDP-11/20 system

[William Donzelli]

 > I think it was later they made an electron beam digitizer
> storage scope.  The scope tube created a fan beam that was
> deflected by single-axis deflection plates.  The target had
> patterns of stripes that decoded the beam into a binary code
> that was then recorded in a digital memory.  So, the fan
> beam of electrons and the target formed the ADC!

That family of tubes is called an electron bombardment semiconductor.
The target is actually a semiconductor wafer with an array of diodes
to sense the position of the deflected swept beam, arranged in a Gray
code. I did a video on one of the tubes sometime ago on my Youtube
channel "uniservo".

--
Will