College-Built Crookes Tube  
Written by AnubisTTP on 2019-11-27  



Up until fairly recently, Crookes tubes were rather expensive devices. A high school or college physics instructor looking to use a Crookes tube in a classroom demonstration would either be forced to buy an expensive reproduction from a scientific supply house, or hope to find an original tube left behind by some long dead Gilded Age researcher. For this reason many teachers resorted to building their own Crookes tubes from whatever glassware and raw materials were on hand. The example shown here is one such device, and serves as a visual example of how sketchy a homemade Crookes tube could be. The tube body is constructed from the outer shell of a Liebig condenser, which has had its thistle removed and replaced with two rubber stoppers. One stopper serves as the cathode, while the anode has been threaded through a blob of resin and bent into a hook which holds a single vane made out of plastic. In operation the stream of cathode rays released by the bottom electrode would strike the plastic target and, hopefully, make it move in response. This tube was designed to be hooked to a vacuum pump continuously while in operation; its resin and rubber construction is likely far too leaky to hold a decent vacuum for any length of time.

The recent arrival of cheap Chinese reproduction Crookes tubes have likely made crude devices such as this wholly obsolete.


Homemade Crookes Railway Tube
Handbuilt Crookes Tube, at rest. This crude device was likely built by a physics instructor for high school or college use.

Handbuilt Crookes Tube
In operation this vane would wiggle when struck by a beam of cathode rays.

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