BTW, if Chris needs very high-Q low capacitance coil designs, he might wantto look at some of the Basket or Rook wound coils. The crystal radio and Pulse Induction metal detector people are really into these things. _http://www.geocities.com/rook_coils/index.html_ (http://www.geocities.com/rook_coils/index.html) I first heard of these from a local TCML member (still out there,Adam?). With Chris' peculiar design needs these might be practical for him.-Phil LaBudde Center for the Advanced Study of Ballistic Improbabilities
I took a look! In the beginning I went for a single turn low inductance low resistance primary (what I built) though it seems my cap bank isn't upto speed with this, so now I am adding a few more turn (for inductance) to lower the strain on the cap bank.. Even though resistance will go up, the Q of the primary should go up due to the extra inductance, though I have not looking into the Q for either primary coil.... The resistance is pretty much as low as physically possible, the inductance has been set so the cap banks should be "happy". Other than that the Q of the primary isn't something I looked into as it can't really be made anyother way.
I am not sure what the outcome of the capacitance is... if it was a rolled cap then spacing the turns just 5mm apart should pretty much kill any capacitance there... I think we all agree that a primary capacitance will be far less in value... so overall, if I space my turns a few mm apart then the capacitance of the primary should in be in the order of a few pF, probably not worth even thinking about..
I know from my initial scope readings that the single turn primary trace on the scope was so faint I couldn't hardly see it, my scope is only 20mhz, so I am not sure what frequency it would actually go to until the trace is so fast you can't see it... but even assuming a 20mhz scope can't see the waveform, and a single turn primary with no capacitance (or very small) the frequency could well be 50mhz or more..
I maybe being too critical with this, though calculating the Joules to 3nF works out at a few KV, the simulation says 800V so I am still unsure why such a difference there. In either case, 1nF either side of the 3nF value could greatly reduce or increase the voltage.... my SCR is only rated at 1200V.... The complication is I don't 100% know the exact secondary frequency, so that's why I am looking for a variable capacitor so I can fine tune the primary.. though its possible it will also effect the primary voltage also so I think everyone can imagine how problematic this thing is to design.
So far I am just trying to pulse the primary to 800V so it gets somewhere neat what the simulation says it should be... any other factors at this point in time I can't really take into account... Once the energy is in the primary (should be 800V or there abouts) then I can work on tuning the primary to about 2mhz and making sure the tuning works... then just a matter of inserting the secondary coil.. study tuning effects, and retune.... There is not much to do really, but the large problem is why I only have 40V on my primary when its supposed to be 800V... once the primary voltage is up, everything else is just regular tuning etc :-)
Once everything is working, then I plan to make another version, and its possible it will be just 10 turns on the secondary coil... low capacitance is the key issue.. it also means a very small toroid... Double the size of the toroid will double the secondary capacitance and half the voltage gain... Though we start to overlap onto known issues then related to size of toroids and breakout voltages... it will be interesting to study these effects on a solid state design, as with a classic spark gap coil, the spark gap itself is the heart of most problems. The only switch in my design is a 100hz SCR pulse, so it should be a lot easier to truly study sizes of toroid and breakout voltages as all the aspects of the circuit are known.
There are no doubt better skilled people on the list that could probably replicate my design and even progress on it.. Though I think everyone is a bit skeptical about the High Q design at the moment.. Though I hope when first light comes that some people on here will start to progress in High Q design also!
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