I've been dissatisfied with the inherent low voltage limits, non-linearity and variability of commercial capacitors. Electrons will drift between the dielectric medium between the plates of the capacitor. This effect will vary with frequency and will be VERY difficult to model since it will be highly dependent upon the material properties and manufacturing process.
In addition, a combination series / parallel circuit involving a number of capacitors to achieve the desired current / voltage might be unnecessarily complex.
Consider 2 hollow conducting cylinders (different diameters) placed within a cylindrical vacuum tube. The cylinder with the smaller diameter is placed within the cylinder with the larger diameter. They are separated by a distance. A distance separates the cylinder with the larger diameter from the inner surface of the vacuum tube. A +Q charge is deposited on the inner cylinder and a -Q charge is deposited on the outer cylinder.
Wouldn't this produce an extremely linear capacitor capable of EXTREMELY high voltages?
I'm not familiar with the cost of producing vacuum tubes, however considering light bulbs utilize vacuum tubes...the manufacturing process must be relatively mature.
Could anybody offer further insight on this?
Would it be possible to DIY a vacuum tube capacitor similar to what I described? What sort of manufacturing processes / equipment would be required? I do not expect it to be inexpensive, but could it be done for less than $5000?
In addition, a combination series / parallel circuit involving a number of capacitors to achieve the desired current / voltage might be unnecessarily complex.
Consider 2 hollow conducting cylinders (different diameters) placed within a cylindrical vacuum tube. The cylinder with the smaller diameter is placed within the cylinder with the larger diameter. They are separated by a distance. A distance separates the cylinder with the larger diameter from the inner surface of the vacuum tube. A +Q charge is deposited on the inner cylinder and a -Q charge is deposited on the outer cylinder.
Wouldn't this produce an extremely linear capacitor capable of EXTREMELY high voltages?
I'm not familiar with the cost of producing vacuum tubes, however considering light bulbs utilize vacuum tubes...the manufacturing process must be relatively mature.
Could anybody offer further insight on this?
Would it be possible to DIY a vacuum tube capacitor similar to what I described? What sort of manufacturing processes / equipment would be required? I do not expect it to be inexpensive, but could it be done for less than $5000?
First off vacuum caps are available in the small pf range. I seem to recall a 100pf
10kv being about 2" x 3" .
10kv being about 2" x 3" .
I have seen even a variable HT vacuum capacitor for HF transmitter use. Very special construction.
Last time I checked light bulbs were filled with inert gas, often mixed with halogen. I think the early Edison lamps were vacuum, but that's a mighty long time ago...
Come over to NJ and see -- the Edison National Museum in West Orange is now open again.
the capacitance per volume ratio of a vacuum capacitor is extremely small, just about the same as for air dielectric caps (dielectric constant for a vacuum is 1, DC of air is 1.0059), actually it's worse for a vacuum because it has to be enclosed in a glass tube, and an air cap doesn't. many plastics have DC's of between 2 and 10, making them suitable for physically smaller devices. there are some exotic materials with DC's as high as 178 (titanium dioxide TiO2) and even up to 310 (strontium titanate SrTiO), and my guess would be that the TiO2 would also exhibit a high dielectric strength (maybe even as high as that of teflon) since it is a ceramic material.
Sparked my curiosity somewhat: My uncle was literally 'cooked/fried' during his years as a WWII Radio man with all the exposure he endured near transmitting equipment. I know they have been used for decades as antenna tuning couplers for short wave & AM transmitters......but a curious search found this from Greenstone USA:
From their Website: ( I learned somethings )
Current VacCap applications: Plasma deposition and etching equipment for the semiconductor industry, flat panel display (LCD) and data storage (HDD, DVD) manufacturing......Plasma fusion.....High frequency generators for drying/sealing etc......Antenna tuning units or couplers....AM and Shortwave Broadcast Transmitters......Medical MRI
Current designs are usually one of either: 1)Fixed vacuum 2)Variable vacuum 3)Variable vacuum water cooled.
Vacuum Capacitors
see specs
Broadcast vacuum tubes
Broadcast transmitter tubes are still basically unchanged......they will 'cook' you: nowadays at least they're well known for that..
Of real DIY interest.....appears these guys are gearing up to also made 'production' audio-grade Valves.
Charles
From their Website: ( I learned somethings )
Current VacCap applications: Plasma deposition and etching equipment for the semiconductor industry, flat panel display (LCD) and data storage (HDD, DVD) manufacturing......Plasma fusion.....High frequency generators for drying/sealing etc......Antenna tuning units or couplers....AM and Shortwave Broadcast Transmitters......Medical MRI
Current designs are usually one of either: 1)Fixed vacuum 2)Variable vacuum 3)Variable vacuum water cooled.
Vacuum Capacitors
see specs
Broadcast vacuum tubes
Broadcast transmitter tubes are still basically unchanged......they will 'cook' you: nowadays at least they're well known for that..
Of real DIY interest.....appears these guys are gearing up to also made 'production' audio-grade Valves.Charles
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