The 5820 is an image orthicon 3 inch television camera tube. Essentially the image orthicon was designed in the 1940s with the objective of removing the main drawbacks in the iconoscope pick-up tube.
The essential operating characteristics of the image orthicon is a low velocity scanning beam that doubles back from the target without touching it. The target is maintained at cathode potential. The beam focusing and scanning is carried out by means of electromagnetic coils around the tube. Above the base, at the right of the picture, can be seen the integral electron multiplier. A low noise signal is available as the tube's output.
This exhibit has no markings and so is not a 5820 but a close relative. This exhibit was salvaged from a live view medical X-Ray system. The X-Ray image formed on a fluorescent screen was imaged by the image orthicon and then to a monitor. The high sensitivity of the image orthicon and low noise make it a suitable camera tube for such an application.
The electron multiplier surrounds the electron gun.
An initial X-Ray of the tube shows the empty space between the head unit and the gun and multiplier sections. This 52 mm diameter tube would be surrounded by the scanning coils that trace out the raster.
This excellent image reveals the complex internal structure.
The head end: left to right, photo-cathode, accelerator grid 6, target cup and mesh and target.
The gun end. The cylinders are the accelerating and focus grids. The return beam passes through the multiplier dynodes where the current is amplified by secondary emission of electrons. The anode is effectively a ring around the central tube that houses the heater and flat cathode.
The end window envelope is 52 mm in diameter and, excluding the 14 base pins, is 385 mm tall.
References: Datasheet. Type 5820 was first introduced in 1957.