[vansig]

boron trifluoride is a precursor to the boranes.

“Boron trifluoride was discovered in 1808 by Joseph Louis Gay-Lussac and Louis Jacques Thénard, who were trying to isolate “fluoric acid” (i.e. hydrofluoric acid) by combining calcium fluoride with vitrified boric acid; the resulting vapours failed to etch glass, so they named it fluoboric gas.”

capture of the exit beam is a significant step. the Rogowski coil is dated circa late 19th to early 20th century.

The onion is completely new science, probably requiring photonic band gap semiconductors. In absense of this, a heat engine would convert energy.
“The Tesla turbine is a bladeless centripetal flow turbine patented by Nikola Tesla in 1913.”

[vansig]

photonic band gap materials could do a lot, for us.

“Unlike semiconductors, which facilitate the coherent propagation of electrons, PBG materials facilitate the coherent localization of photons. Applications include zero-threshold micro-lasers with high modulation speed and low threshold optical switches and all-optical transistors for optical telecommunications and high speed optical computers.

“In a PBG, lasing can occur with zero pumping threshold. Lasing can also occur without mirrors and without a cavity mode since each atom creates its own localized photon mode. This suggests that large arrays of nearly lossless microlasers for all-optical circuits can be fabricated with PBG materials.
— http://www.chem.utoronto.ca/staff/GAO/flashed/Si.htm

it also suggests that you can place photons where you want them, and that could improve efficiency of photo-voltaics quite a lot.

[vansig]

greater yields ultimately bring things closer to break-even, sooner. if you exceed break-even on a smaller shot, then you can run more shots per second, or expect wear on equipment to be lower

zapkitty wrote:
… er… and if that 8-10 fold means 8-10 x the smaller plasmoids?

a careful read of the September 6 report suggests, to me, that the induced angular momentum is like a spinning X, whose arms can be moved to any angle. tall and narrow leads to fast collapse and smaller plasmoids; whereas short and wide leads to slow collapse, and more x-ray loss. the sweet spot optimizes across plasmoid size, rate of collapse, x-ray emission, and yield. lots, but there’s also the total size of the pulse, in kJ, the voltage, rise time, fill pressure, gas temperature, all to be tweaked.

i am, once again, optimistic.

[vansig]

zapkitty wrote:
From an update on the LPP site it seems that they believe they have a handle on that particular issue now and they hope to increase plasmoid volume and fusion yields by 8-10 fold…

http://www.lawrencevilleplasmaphysics.com/index.php?option=com_lyftenbloggie&view=entry&year=2010&month=09&day=06&id=16:switch-problem-resolved&Itemid=90

… and the primary focus of that update is that they’ve gotten the switches to working on cue.

Now if they can deal with the x-ray conversion issues so handily… 😉

That is tremendously good news, because the 8-10 fold increase in yield will result in smaller x-ray emissions, as well.

[vansig]

vansig wrote: probably not, unless we can force a situation where secondary electrons have exactly the right energy to be captured most-efficiently; eg: if the PV cell lases,
…which might be the case if, for a 215 nm band gap, for example, the semiconductor is, say, 215 nm thick, or forced to occupy a channel 215 nm wide.
perhaps something similar to this photonic crystal defect cavity : http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=ADA471262

the above sounds really advanced, but it might be entirely feasible.
— http://www.osti.gov/bridge/servlets/purl/179272-kOZES2/webviewable/179272.pdf

[vansig]

zapkitty wrote:
I thought the trend mentioned was toward smaller, yet hotter plasmoids?

My reasoning is based on having to put 100 kJ energy into the plasmoid each shot. It may be hotter, but if it’s smaller, then less fuel gets burned. (unless smaller implies denser also??)
But I realize that since the machine hasn’t yet been optimized for boron, it’s a bit early to speculate.

[vansig]

Aeronaut wrote:
Do we really need to boil the working fluid to get high efficiency?

Turbines employ the pressure differential between the vapour and the condensed liquid, but other ways are conceivable, each with its own constraints. Thermal photovoltaics, suggested above, would work by spontaneous emission and capture within a narrow band of wavelengths.
Following are the blackbody charts for two different temperatures…

Attached files

[vansig]

MTd2 wrote: Why not tin? Going almost to boiling temperature and lowing it to melting, it gives an ideal of 83% efficiency. It has a reasonably high density and atomic weight, so it can capture a lot of x-rays.

i’m not worried about capturing the xrays; what’s a worry is, how do you contain the hot fluid? what is your container made from? how do you cold-start it?
what is the engine’s principle of operation? how close to ideal does it’s efficiency get?

[vansig]

Most solar PV is concerned with colour temperature matching our sun (5770 kelvin).

Equipment operating temperature upper bound is well below that (700 .. 1500 kelvin), and
the xrays themselves also well outside that range (equivalent to ~500 million kelvin)

[vansig]

Aeronaut wrote:
Eric mentions in the patent that the preferred pulse freq is ~1 khz to keep the fuel ionized.

This changes some assumptions, and the numbers around them. If we assume therefore that a 5 MW generator is pulsing at 1kHz instead of like 330 Hz, then this triples the heat rejection requirements.

However, I read this spring that the plasmoid size is turning out to be smaller than expected — at least in deuterium. if that turns out to be true for boron also, then it would tend to reduce the yield per shot. That isn’t a disaster, but it places tighter constraints on power conversion efficiency, throughout the system.

I think it’s time to get intimate with the properties of the exit beam, and work out how to capture it. I’m assuming it will look like this…

Attached files

[vansig]

Before we turn the page on steam power, do check the discussions over in the LPPX forum that are discussing it,
and the alternatives, under topics called ‘the onion‘, and ‘heat engine’.

[vansig]

Aeronaut wrote: What’s the creep temperature for a generic stainless steel?

this 1972 westinghouse patent seems like a good place to compare different steels: http://www.freepatentsonline.com/3635769.html

interestingly,
operating temperature for the hot side of the heat engine in a CANDU fission reactor is said to be 290 °C. That leads to ~33% efficiency.
— http://www.wordiq.com/definition/CANDU_reactor

Apparently the biggest problem with using steam is boiler system corrosion. — http://www.gewater.com/handbook/boiler_water_systems/ch_11_preboiler.jsp

[vansig]

since the x-rays probably cover a wide range of wavelengths, splitting the spectrum and processing different bands in different places would boost efficiency tremendously.

and that’s where this book will come in handy: http://www.porous-35.com/index.html

[vansig]

Tulse wrote:
As I understand it, current commercial photo-voltaic solar panels are rather inefficient (~15-20%). Can we reasonably expect to get significantly better out of the onion?

that figure is for single-layer monolithic silicon. as of 2009, 45% has been achieved in laboratory, using triple-layer thin films, tuned to different band, R-G-B. (very similar to what the onion is considering, but with visible light, rather than x-ray).

by the way, the principle of up-conversion could make it possible to relax this constraint of whether secondary electrons can be given exactly the right energy. — http://www.rp-photonics.com/upconversion.html

[vansig]

Well, x-ray photo-voltaics is not-only unproven, it’s a completely new regime. There is much imagination and science to do, and it wont be ready by next year.

So if you want to use parts that were available to Nikola Tesla, then we’ll start another thread for Heat Engine

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