Vacuum electronic devices are one of the types of electric vacuum devices . The main feature of devices of this type is the movement of electrons in a vacuum .
Design
Vacuum electronic devices are usually hermetically sealed glass, metal or ceramic ( nouvistors ) vessels with various electrodes inside, connected to the contacts of the external connector of the device through a glass or ceramic vacuum-tight insulator. Previously, air is removed from them. Pumping is accompanied by heating, both thermal and high-frequency (less often microwave field), of the inside of the device in order to remove absorbed gases. Also, a getter is used for this - a circle or a ring of thin tin coated with metal barium or a special chemical composition that absorbs gases well both during and after spraying. These are, as a rule, the most toxic substances in vacuum devices. The less gas left inside, the more durable the device. The minimum residual pressure in electronic devices operating at voltages up to 1 kV is considered to be 10 -4 Pa for long-term operation. For high-voltage picture tubes (25 kV), the minimum is 10 -7 Pa (5-10 years). For large-sized devices like accelerators, the requirements are thousands of times higher.
In any vacuum device there is a cathode (direct or indirect heating, less often without heating - “cold”), often coated with a special composition for high electron emission into the vacuum of the device’s working area; and the anode is the last working electrode collecting the "spent" electrons.
All vacuum devices have an electronic stream as a working substance, flying from the cathode to the anode and interacting along the path with simple electrodes (grids and focusing electrodes) and complex ( microwave resonators , luminescent screens, etc.)
Classification
Vacuum electronic devices can be divided into the following classes:
- Electronic tubes or radio tubes : diodes , triodes , tetrodes (including beam ones), pentodes - often several different vacuum devices are placed in one cylinder for general reduction in price;
- Microwave vacuum devices : magnetrons , klystrons , TWT , VOC ;
- Electron beam devices : cathode ray tubes , picture tubes ;
- Accelerators of charged particles : x-ray tubes ;
- Photoelectronic devices : PMTs , vacuum photocells, electron-optical converter ;
- Vacuum indicators : indicator lamps (outdated), magic eye , vacuum-luminescent indicators .
Literature
- Batushev V.A. Electronic devices. - M .: Higher school, 1980 .-- 383 p.
- V.N. Dulin, N.A. Avaev, V.P. Demin, and others; Ed. G. G. Shishkin. Electronic devices. - M .: Energoatomizdat, 1989 .-- 496 p. - ISBN 5-283-01472-X .