THE ELECTRON GUN

Our CRTs require a beam of electrons, which we produce using the assembly shown in Figure 41. Electrons are stripped off the cathode by a process known as glow discharge between an aluminum cathode rod and a hollow anode. The electron gun is built inside an Ace-Thred #11 connector (Ace catalog number 7644-10). The cathode is a 3/8-in. aluminum rod sealed against the Ace-Thred #11 connector through an Ace-Thred #11 bushing. The anode electrode is a 7/16-in. brass tube threaded to accept a 1/4-in. FIP brass cap. An easy way of making it is from a 1/4-in. brass nipple turned to reduce its body diameter to 7/16-in. Electrons exit the gun in a fine beam from a 1/32-in. hole drilled in the 1/4-in. FIP anode brass cap. The gun couples to our Ace-Thred #25 tubes through an Ace-Thred #25 bushing. The gun is sealed against the bushing through a Kurt J. Lesker B-075-KM vacuum coupling that we epoxied to a 1-in.-OD × 2-in.-long stainless steel tube.

Figure 41 The electron gun for our homemade CRT (Figure 40) uses glow discharge between a cathode rod and a hollow anode. (a) The electron gun is built inside an Ace-Thred #11 connector (b) coupled to an Ace-Thred #25 bushing through a Kurt J. Lesker B-075-KM vacuum coupling epoxied to a 1-in.-OD × 2-in.-long stainless steel tube. (c) We drilled a 1/32-in. hole in the 1/4-in. FIP anode brass cap to allow a thin electron beam to exit the gun.


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