[Aeronaut]

Breakable wrote: Nice thing about vacuum tubes is that they are kind of DIY, unlike transistors.
http://www.youtube.com/watch?v=gl-QMuUQhVM

Some problems with tubes are that they’re huge and sensitive to mechanical shock.

[Aeronaut]

Timo wrote:

The Focus Fusion test reactor is roughly the dimensions of a 36 cup coffee pot, so it can go into lawn mowers if you can get the shielding, capacitors, vacuum pumps, and other support systems small enough and light enough.

That sounds nice. 5MW car engine 🙂 Even if it were just very heavy duty trucks, it would still be great improvement over current ICE fossils. Definite ship powerplant material.

I think the shielding is the major problem to miniaturize, others are more or less just engineering challenges.

If I understood physics right you need something that has high hydrogen concentration to capture neutron radiation which basically means water, that that is something that weights a lot. Tried to find some measurements about capacitors but didn’t find any. 25-50kV doesn’t sound much, but IIRC those capacitors are quite big. That might be another not so minor challenge.

I’m currently resigned to a 1 meter water jacket and the same caps, maybe even switches, that LPP’s using for my sketches.

[Aeronaut]

Advances are not linear, and especially not from shot to shot. A LOT of thinking goes into how some of the shots seemed to do better than the current average, and the diagnostic suite of instruments is designed to produce several ways to double check one or more results. Then comes an AHA! moment, some more experiments based on altering one or more variables, some more test shots, and perhaps a trip to PPPL, and perhaps a meatier update. Some months or quarters. Hopefully. Patience and determination are required. Keep up the great work, gang!

[Aeronaut]

The Focus Fusion test reactor is roughly the dimensions of a 36 cup coffee pot, so it can go into lawn mowers if you can get the shielding, capacitors, vacuum pumps, and other support systems small enough and light enough.

[Aeronaut]

Welcome to FFS, Timo. Excellent backgrounder link. Not much hope held out for SSTO without big, expensive rockets, but then the Rocket Equation said to expect that, lol.

[Aeronaut]

Outstanding links, Henning. I learned a lot from Sandia’s copy writing strategy, too- hadn’t realized how similar their electrical requirements are to ours. Any idea who makes those thermos bottle sized capacitors?

[Aeronaut]

Hope you can find the links, Brian. A 20MW SSTO vehicle would be sweet!

[Aeronaut]

mchargue wrote: As I understand the current switch, it comprises 12 spark-gaps to decrease the current density through any single conductor, (switch) and already represents a problem with timing between the various switches. Increasing the number would further decrease current density through any one switch, but would likely increase the timing problem.

Unless & until a better mechanism is put in place to resolve timing issues between switches, I’m not sure that you’d want to increase the count of them.

As for lower voltage, I think the plan is to increase the voltage in order to increase the amperage, so lowed voltages probably could not be a goal.

My $.02

Pat

This reminds me of the old Darlington Transistor configuration, where a fast, sensitive transistor drives the brute force switching transistor. Dusted off and applied to thyristors, why not? After all, 5 inch wafer processing assembly lines should be a dime a dozen in this 8 inch silicon wafer world.

Darren Snider posted this on the FB page recently- http://www.divtecs.com/research/high-current-high-voltage-igbt-switch/ which looks to me like it might be properly scalable.

[Aeronaut]

Francisl wrote: That brings up a related question because of Newton’s law that for every action there is an opposite and equal reaction. The positive beam is carrying a lot of energy and momentum but the negative beam should have relatively little energy and momentum. That means there is an unbalanced directional force on the plasmoid forcing it to move in the opposite direction from the positive beam. If the plasmoid doesn’t move much that would indicate that either there is a significant amount of momentum in the negative beam or the strong magnetic field in the DPF is transferring the reaction force to the DPF structure.
If there is a reaction force that is transferred to the DPF structure would the force be significant? Would a vibration be detectable? Could a resonant vibration occur in a DPF running in continuous mode?

Good question that I’d overlooked. FF’s 1st 2 scaling experiments were funded by NASA’s JPL, so if it were configured as an ion drive, the magnetic field would couple that impulse to the DPF structure, and from there to the ship’s frame. I’d hazard a guess that, configured as a fusion electric power plant, this kinetic energy would be conserved as the coils convert it into electricity and heat.

[Aeronaut]

zapkitty wrote:

I’ve watched the animations for the collapsing plasmoid and they show a positive beam traveling in one direction and a negative beam traveling in the opposite direction. There has been discussion about using energy recovery coils for the positive beam. Can’t coils also be used for the negative beam?

As I understand it the negative beam is supposed to expend its energy on the plasmoid that created it… heating it even further and thus increasing the fusion yield and the positive beam output,.. so it would already be increasing the electrical output in an indirect manner.

Right, Zap. The negative beam is shown for completeness, even though its circuit is virtual- it heats the plasma even further. The problem illustrating it is that you have to show that ion stream being balanced by an electron beam in order to be believable to scientists. Of course that’s at odds with illustrating how the theory says it works…

[Aeronaut]

Great assist, Zap! That’s close enough to get tinkerers wondering if they could build one or more of those coils profitably :coolsmile:

[Aeronaut]

Very good points about safety, Rezwan. I’d like to add that in any conversation regarding safety, the questioner must specify the degree or specification (OSHA, IEEE, Mil-spec, etc), and preferably also specify the configuration(s) which are being asked about. Also, the person representing FF DPF should have a firm grasp that the water jacket covered with boron-10 and lead is designed specifically to reduce operating (not long-term) radiation to below background radiation levels.

Thus the question and response need not necessarily be about the LPPX envisionment for some remote and or military applications. Safety includes specifics.

[Aeronaut]

Francisl wrote: Diamond switches will be expensive to develop. Can we bypass them for a while by using two or more capacitor banks to store the energy released from the DPF? One bank would fire the DPF and the second bank would capture the energy.

The design already calls for separate input and output cap banks and even more high-speed, high-power switching. Darren Snider posted this link on http://www.facebook.com/pages/Focus-Fusion-Society/205597630257?v=app_2373072738&ref=mf#!/permalink.php?story_fbid=158594220845040&id=205597630257 that looks like a company has a series-parallel IGBT (array of solid-state switching elements) which should be be further scalable to our projected operating voltage range.

http://www.divtecs.com/research/high-current-high-voltage-igbt-switch/

[Aeronaut]

Brian H wrote: Is it necessary to get to the level of detail of segments of the coil for this short demo? It might be more a distraction than anything; it certainly isn’t core to comprehending the process.

Yes, since he’s using it to teach himself as well as others. Whether it ends up in the animation remains to be seen. In any event, the lack of voiceovers is a recurring weak spot in our animations.

[Aeronaut]

Great image, Zap. I was figuring helium because it’s going to be handy in the rest of the cooling system (everything’s going to run warm at least) and because I’m neither an engineer or scientist, lol.

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