"Beyond Dr. Miley ... Pulsed fusor #19" - Cont'd

For posts specifically relating to fusor design, construction, and operation.
DaveC
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"Beyond Dr. Miley ... Pulsed fusor #19" - Cont'd

Post by DaveC » Mon Dec 16, 2002 6:16 am

(Need some new space for more discussion. )

Larry -
When you discharge your cap into a spark gap... how do you control the ringing. nHy inductances and uF capacitances will make your system sing at high frequencies, unless the energy is damped in resistive losses. The energy could be spread over a lot dissipative regions, the gap, the leads and etc.

Probably not too hard to put a small antenna on a fast scope input and check the wave form. Delivering GW levels of energy to a circuit in uS, is a bit tricky. Impedance matching is vital, and making the actual measurement is not trivial. If you have access to a good Pearson coil ( aka rf current transformer) you could probably get a reasonable idea.

Regarding the transformer in vacuum, I think its magnetic field will not be helpful in getting ions to collide. The magnetic field goes down the axis of the transformer and then circulates around on the outside entering the low voltage end. Electrons travelling down the axis will tend to spiral and those outside will be directed into looping paths that will collide with the secondary...

Don't want to throw cold water...Did I miss something in your hardware description?

Interesting ideas, nonetheless... Keep going!!

Dave Cooper

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Re: "Beyond Dr. Miley ... Pulsed fusor #19" - Cont'd

Post by 3l » Mon Dec 16, 2002 3:03 pm

Hi Dave:

That's what makes this work so intriguing.
I fought the ringing problem for about a year maybe a year and 1/2.
Past work in PDF at OSU seemed to reduce ringing by
eliminating leads entirely .... gun attached right to the capacitor.
They charged the cap then DISCONNECTED the ps.
That's how I got around all the grunge work drudgery
of electrical simulations.....without the the supply the problem becomes a simple network problem with three elements. To balance that network enters another realm of drudgery. it must be as perfectly balanced as humanly posible. You must use Gertsch Bridge measurements to 5 or 6 decimal places on all components and all connection leads and the resistance induced by fastener termination ....on restance and capacitance. Humm all that PMEL busy work has paid off. You can do amazing stuff if you know the exact resistance of the Spark gap terminal. Oh yeah that gap must be sealed
for consistant operation.
Water pipe seems so simple but Techneque ....
Techneque.
Even tho it's old timey it is still a hard task master to get it to work right.

Fusion is Fun!

Larry Leins
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Re: "Beyond Dr. Miley ... Pulsed fusor #19" - Cont'd

Post by 3l » Mon Dec 16, 2002 5:51 pm

Oops forgot to mention that picture I posted was from the first attempt at pulse...it's fairly old. I used a digital dvm to meaure out the parts. My new rig ate my digital camera first time I used it... sorry. At a distance of eight feet! My new rig is a free stander and is a heavy
device. The emp burned my circuit breakers in my box
so I had to go to charge and disconnect before fire.
I will try to get a way to put 35 mm film on the net.

Fusion is fun!
Larry Leins

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Re: "Beyond Dr. Miley ... Pulsed fusor #19" - Cont'd

Post by 3l » Mon Dec 16, 2002 9:38 pm

For all those who have interest in high power the following website has some pretty up to date experiments in the 20kj range.
Although a little low in voltage the principles are the same.

http://www.powerlabs.org/index.html

New***
No mater how hard you try you can't get rid of all the ring.... may as well milk the blue sky. I simply reduced the ring length to 2 microseconds. I have yet to precisely measure the actual output.... all I have is how many amps...how many volts.

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Larry Leins
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Richard Hull
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Re: "Beyond Dr. Miley ... Pulsed fusor #19" - Cont'd

Post by Richard Hull » Tue Dec 17, 2002 10:34 pm

Ringing is the exchange of energy back and forth in a more or less closed system between the capative and inductive reactive components.

Careful aplication of a hydrogen thyratron can elimenate all ringing.

I use it in a tesla coil primary and use my 1000:1 pearson wideband CT on a scope to verify this.

The problem comes if your circuit has a resonant frequency above one mhz. Keep it under 1mhz and the H2 thyratron can be used. This might actually require a small inductor in series with the system of about 20uh.

The firing pulse width on the Thryatron grid should be on the order of 1us wide, no more.

When the capacitor fires using the H2 thyratron as a switch, the first half cycle of current rises and falls. The instant it zero crosses the H2 thyratron is reverse biased by the inductor's collapsing field, shuting it off. The current waveform is a single positive pulse of a gang o' amps and any excursion below zero on the first negative alternation of current relates to the dv/dt characteristic of the inductor's internals and the tube cutoff characteristics in reverse bias.

Naturally, the GHz resonant cavity of the fusor itself will be excited as a separate entity, but current wise in the external firing circuit and accelerator chain there will be no ringing due to opening of that circuit before ringing can occur.

Note, that by doing this, you are wasting a lot of energy.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

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Re: "Beyond Dr. Miley ... Pulsed fusor #19" - Cont'd

Post by 3l » Wed Dec 18, 2002 1:20 pm

Hi Richard:
That was my first thought but like you say it bleeds
about 85% of the juice away.
That is why I decided to let it oscilate at 500 khz.
I want to see what an oscilting current does to a fusor structure. if the fusor doesn't like I guess the next step is the blocking diode from hell. that way you would only lose 50% (sigh!)

Larry Leins
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Re: "Beyond Dr. Miley ... Pulsed fusor #19" - Cont'd

Post by 3l » Wed Dec 18, 2002 6:59 pm

I hate to leave a thought unfinished.

So we cant get it to stop ringing....why not use two sets of blocking diodes and run two fusors one on the negative pulse and the other hooked up in reverse order for the positive wave.
I wondered how much more that 50% it will yield?

Larry Leins
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Re: "Beyond Dr. Miley ... Pulsed fusor #19" - Cont'd

Post by DaveC » Wed Dec 25, 2002 3:41 am

Guessing wildly here... and assuming the second fusor is floating with respect to ground, so the cathode can be formed, .... about as much as the other half cycle string yields.. So it should double the output, and vastly increase the safety hazard .

Dave Cooper

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Re: "Beyond Dr. Miley ... Pulsed fusor #19" - Cont'd

Post by 3l » Wed Dec 25, 2002 3:03 pm

Another advantage of charge and disconnect.
Yes at this time they float for about ten minutes until I cut in the bleaders. Blocking diodes are still in the research stage unfortunately ....So safety is still very primative at this level of operation.
The floating deck is highly insulated and fortunately for me it is mainly discharged after the pulse is done with a small but still lethal charge on the cap.
My instruments and vacuum equipment are protected by a 6 " long pvc pipe that isolates them from the floating deck so you won't light up when you close a valve on the vacuum pump or burn up vacuum gauges.
By disconnecting the supply there is no way for the cap to gain charge behind your back. Unlike Dr Milley's machine that runs continiously my test rig doesn't do a high speed charge and fire and that yields a much more managable situation. In the dual which is the next step, the cap will be charged in full but will be disharged in small spurts
with the supply disconnected.
I can deal with a floating deck for ten minutes but to have it go any longer would be death by complacency.
It is very much like a test of a liquid fueled rocket.
Tense loading... tense count down....relief after a successful testfire.

Larry Leins
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Re: "Beyond Dr. Miley ... Pulsed fusor #19" - Cont'd

Post by DaveC » Thu Dec 26, 2002 4:31 am

Colorfully put, Larry !! No need to remind you to be careful.

Dave

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