VIGOROUS PUMPING IN ACTION
Posted by STEVE MYCIUNKA on
Today's Mullard archive photograph shows the evacuation of television picture tubes at the Mitcham works some time in 1953.
The operator is placing the tube on a diffusion pump. Diffusion pumps use a high speed jet of vapour to direct gas molecules in the pump throat down into the bottom of the pump and out the exhaust, nowadays we use a polyethylene glycol (PEG), PEG ethers or more commonly, a silicon oil, however, in 1954, the preferred vapour was mercury as it didn't char, didn't contaminate the tubes with vapor backflow and of course was readily available.
The tube passed through a heated tunnel where any gaseous emissions were pumped out prior to sealing once the hi-Torr vacuum was pulled.
