EMR 18 Stage Photomultiplier (Unknown P/N)  
Written by AnubisTTP on 2020-12-12  



This device, made by EMR, is complicated high-gain photomultiplier tube designed for use in satellites and underground oil prospecting equipment. The tube is built around 18 dynodes formed into a single vacuum envelope, which is constructed from multiple layers of kovar and glass that have been induction fused into a solid package. Each kovar ring acts as an external pin for the device, with glass encapsulated resistors installed at the factory to form the voltage divider for the dynodes. The side viewing window at the top of the device also contains the tube's evacuation nipple, as well as providing an entry point for the vaporized metals that form this tube's photocathode. During manufacture a glass compartment filled with photocathode material would be attached to the nipple. Electric heaters built into the compartment would vaporize the photocathode material, which would enter the tube and coat the window. We do not know the exact part number of this device, but it appears externally similar to an EMR 541 venetian blind phototube.

EMR photomultipler tubes are normally potted into a protective black cylinder of rubbery material with only the front window exposed. The example shown here has had it's outer rubbery shell stripped away, allowing the complex internal construction to be seen.


EMR 18 Stage Photomultiplier tube
EMR 18 stage photomultiplier, at rest

EMR 541A Photomultiplier Tube
Though we do not know the exact part number of this device, it appears externally similar to an EMR 541 and 541A.

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