Thank you all for your valuable suggestions and highly interesting information, and for taking me seriously. I appreciate this brainstorming. I attached a photo of my self-made 2KV capacitor (150 microFarad) to show that I am very seriously working on this project - that Cornell Dubilier cap cost me 5,000 USD in parts and quite a few days of CNC-drilling and soldering. Its internal resistance is 0.05 Ohm. I did not measure its self induction yet. Please note that I am a NOOB. I did not want to buy a Chinese cap bec. my cap is superior in terms of being able to handle much larger and for a much a longer time, ability to self-repair at over-voltage as well as gaining experience with such projects.
I will carefully consider all your comments and suggestions and will base my decisions on them, as well as on further discussion/research/experimentation/calculation/simulation. And I may PM those who offered consultancy.
I will address your points now. Minimum specs in more detail:
- The device MUST be variable-frequency and it must be settable to any arbitrary frequency between 0.5 and 2 MHz (20 MHz was a "nice to have" feature but let's stick to the essentials first) by an analogue dial and the device should be able to operate for at least 10 minutes at a time before cooldown is required. The freq. should be changeable steplessly while the field is on. The field strength should be between 0 and 2T, 2T being nice but 0.5 would already be acceptable. The volume of the field should be at least approx. 1 cubic centrimetre.
- IMPORTANT: It's permissible to have a short duty-cycle. For ex. the device operates for 100 ms and then is off for 900 ms. That would reduce heating by an order of magnitude.
- The budget is 50,000 USD - 100,000 USD.
- Thanks for suggesting tubes. I started to think about that already.
- Thanks for talking about various physics-related issues that are complicating design factors. I tried machining Teflon - indeed difficult. I could freeze it (even in liquid nitrogen) to make that easier. The comment about gold-plating: I actually have several KG of gold at my disposal so I could even make the coil out of solid gold, but isn't silver a better electrical as well as thermal conductor? I will perhaps make the coil out of thick litz, to help with the higher frequencies. A disadvantage is that you can't run water through litz.
- I have been thinking of constructing a variable-induction coil but I think that's less practical than a variable C.
- This is a private project with perhaps commercial potential in the far future.
- I am aware of potential adverse health effects and will strive to provide adequate shielding with mu-metal (crazy expensive stuff...) etc.
- I will resist the urge to try how quickly I can wirelessly charge my smartphone with it. If I break down and can't resist that urge anymore, I will try it first with my wife's phone and get back to you with the results.
- I am aware of potential harmful radio interference and will work to avoid getting into trouble with the law. I have RF probes for my spectrum analyzer and successfully done FCC pre-compliance testing on one of my products so I should be able to detect such stray radiation.
- The attached cap I made was for the purpose of generating a multi-T AC field for just a few microsecs. Using a spark gap as a switch and a MOT-based PSU.
- Interchangable heads is an interesting idea but there still needs to be a very significant freq. range, so perhaps not practical.
- Different machines: Too expensive/impractical. I rather spent even 100 grand on one machine and have it weigh a tonne.
- It is NOT OK if the frequency undershoots/overshoots significantly for a while before settling to the target. The freq. should be stable to a reasonable degree but can vary due to thermal issues etc. There are no requirements as to maintaining a set freq. stably. Any significant deviations of the freq, even for one microsecond, are NOT permissible.
- The field should look like a sine wave and not have harmonics or other freq. components.
- The coil, absent heroic measures, will come apart due to the enormous forces generated inside of it, so it will have to be heavily reinforced by composite materials.
- Any fellow aspies noticing that those bolts are ugly-long: I replaced them with shorter ones :-)