[jamesr]

KeithPickering wrote:

Now I can see how the electrons and ions produced might be captured with nearly 100% efficiency (although this too needs to be demonstrated). But 40% of the energy produced is in the form of x-rays, which are supposed to be captured by the layered foil shell. How efficient is that shell? If it’s only 20% efficient (which is comparable to solar PV cells), the device itself will only capture 68% of produced energy. And that would mean that the effective breakeven point is 47% higher than the theoretical breakeven point.

It may turn out that you can get to theoretical breakeven, but not quite to practical breakeven … or just barely over the line, which would mean that the excess salable energy would be a lot more expensive than assumed.

X-rays are not produced by the fusion directly, so it might be a little missleading to say 40% of the energy is produced in the form of x-rays. They are the result of electrons being deflected by ions and emiting Bremsstrahlung radiation.

The key point for Focus Fusion yet to be shown, as I see it, is whether bremsstralung x-rays will cool the plasma too fast and stop enough of the boron fusing in the plasmoid to release more energy than it took to make it. The plasmoid needs to confine the Helium ions and recycle their energy to keep the Hydrogen-Boron plasma hot for over 50ns (a very long time for an ion with a few MeV of energy). The He 2+ and B 5+ (and any other impurity) ions emit huge amounts of x-rays as they interact with the electrons. According to conventional physics this makes ignition of a pB11 plasma impossible as it will always radiate away the energy faster then the fusion reactions can heat it.

Only if the magnetic field in the plasmoid (assuming the plasmoid does exist in the form postulated) is strong enough for the ‘magnetic field effect’ to restrict the energies of the electrons and so result in a lower electron temperature than the ion temperature can there be any hope of it working. It is this that the ongoing experiments need to demonstrate. If the boron bremsstralung rate is only reduced to say 10 times higher than for hydrogen (rather than the normal 5^2=25 times), then the whole effort is still futile. It is needed to get down to only a few times higher that hydrogen for the plasma.

Only after this burning of a pB11 fusion mix has been demonstrated, I think will engineering the capture of the x-rays to recover their energy to get to the breakeven be worth pursuing.

[jamesr]

Rezwan wrote:
New Issue, for all you PC people – how do I download the DV footage to the pc? On my mac, I just used a firewire. This cable apparently does not do anything with the pc. Went out and got a digital IEEE 1394 cable which looks just like a firewire cable – but don’t see where to stick it into the PC. And using a regular USB cable, the thing doesn’t detect anything.

firewire is just a name (mainly used by apple) for IEEE1394 – Sony used to call it i.Link. There are the larger 6pin connectors and smaller 4pin connectors, typically a dv camera will have the smaller 4pin socket and a PC firewire socket will be the 6pin variety. If your PC doesn’t have one you’ll need to get an interface card to put in it – like these.
Alternatively if another PC there has one, capture the material on that and copy it over.

Just to confuse things a newer firewire 800 standard (IEE1394b) is also around, the old one runs at 400Mbps, which has a yet another type of connector.

[jamesr]

You could try and download this version: movie maker 2.6 for vista

[jamesr]

slane wrote:
Pinch, pinch, pinch.
In above posts, I have already pointed out that the eyewalls of sunspots have huge amounts of the circular electric currents (1,000,000,000,000 Amperes for middle size circular sunspots), so plasmas in eyewalls of sunspots are in pinch state, that is, in high temperature high density state, so stable nuclear fusion reactions can happen in eyewalls of sunspots.
Z-pinch fusion experiments are done almost every day; do you not believe these experiments?
Some CMEs and solar flares of the sun are caused by these pinch processes in the eyewalls of the sunspots.
Sunspots are ion-pumps and electron-pumps too; the X-ray photos of the sun reveal that almost all high temperature (above one million Kelvin) high energy phenomena of the sun are related to the sunspots.

Just because there is a current doesn’t mean the pinch is strong enough to collapse the filaments enough to heat them significantly as done in Z-pinch machines. The large current is spread out over a huge volume, so the local current density at any one point is still small.

The ions & electrons accelerated into the magnetic loops above the area of the sunspot do indeed reach a high velocity/temperature and so the electrons emit bremsstrahlung radiation at x-ray wavelengths. And I suppose there could be a very small chance of fusion for the most energetic ions, but it’s hardly a significant phenomena.

Flares and CMEs are spectacular and involve the transfer of huge amounts of energy from the magnetic field to the plasma surface of the sun, but in no way are they related to fusion.

[jamesr]

Here is an old article about it – Science Daily

The way I see it, he is using a resonant chamber to create order out of chaos – this takes energy which is taken from the heat of the gas, cooling it. I’m not sure how efficient it could be though. The efficiency is governed by the difference in initial and final temperature. If the gas cools too far it will no longer be enough to excite the resonance and so stop cooling.

It is similar in a way to cooling by lasers. In ultra cold experiments they use lasers to set up a standing EM-wave. Atoms are then trapped in the troughs of the wave and can’t get out – restricting their movement and therfore cooling them.

[jamesr]

dash wrote:
OK, my interpretation of what you claim this fellow said is he has computed the theoretical amount of heat generated by radioactive decay in the crust of the earth. He has evidently put some nice equations together and has some numbers.

And you come along and accept it as fact without question. Moreover you accept his assertion that the earth must be cooling.

Dude, it’s just a theory. It may be right. It may be wrong. But it’s not proof. You behave as if it is proof. And you get offensive when other people (such as myself) don’t accept it as fact.

-Dave

Both texaslabrat and myself have tried to explain, citing well respected sources, why radioactive heating is dominant on earth and tidal heating is only a minor component. Yet you seem to be disregarding them out of hand. As texaslabrat said, the figures we quoted are based on years of independently verified measurments that fit (to a greater or lesser extent) the theoretical models. Just becuase you think everyone else is wrong doesn’t make you correct. Where is your evidence? What are your sources? Qualitative statements on things like Io and Venus’s volcanism are pretty meaningless. To compare Io with Earth you need a quanitiative approach.

You say I accept it as fact without question – I did not. My understanding on the basis of years of study as a physicist with more than a passing interest in geology, reading and comparing multiple sources. I cited the book as a well respected source, and one that conveiniently had all the figures to hand.

Be skeptical when a theory fails to explain measured data, or where it constantly has fudge factors added. But with radioactivity you’re on pretty safe ground.

[jamesr]

I wasn’t sure about the 1/10 figure either so I did a bit of googling.

The book:
The solid earth: an introduction to global geophysics By C. M. R. Fowler gives detailed analysis of the figures for the radioactive heating and gives a bottom line figure of 2.1*10^13W = 21TW for the radioactive heat of the crust and mantle (not including the core). NB it wasn’t thought the concentration of Potassium-40 was very high in the core itself. However recent studies have found potassium does actually dissolve in iron when at very high pressures. So if there is a higher concentration of potassium-40 in the core then there will be some more heat generated there. (source)

If the 3.75TW figure for tidal heating is correct, and using the 21TW figure from above, this would make the ratio of tidal/radioactive 3.75/21 = 1/5.6. So the 1/10 figure is correct to 1sf.

The total rate of heat loss currently by the earth is given as 4.2-4.4*10^13W. ie. we are loosing twice as much heat as is is now being made – hence the earth is cooling. In the past the radioactive heating component would have been much larger, exponenitally so, given the nature of radioactivity. Whereas the tidal heating would have been roughly the same. Hence over the age of the earth the proportion of the stored heat due to radioactivity will be much higher than the current heat generation ratio.

[jamesr]

annodomini2 wrote: Has anyone considered using a diamond anvil to create fusion?

Is this possible?

Either way why?

If possible could this system be used to create a net energy effect?

Would there be any significant additional problems with this concept?

To get fusion you need a high enough temperature (10-100million Kelvin). Obviously increasing the pressure of a substance will cause it to heat up, and some diamond anvil cells are design to use lasers to provide additional heating, but only to a few thousand degrees. Diamond anvils can exert such high pressures becuse the diamond is very strong and hard. However diamond’s melting point is around 3500C, at which point it will not be able to maintain the pressure. No solid or liquid substace can exist in the regeme where fusion works, everything is plasma.

So, no it won’t work.

Inertial confinement fusion as done in the laser facilities such as NIF does work by excerting a huge pressure, but that is done by the laser (via a gold cylinder called a hohlraum) burning off the outside of a frozen pellet of deuterium (or D-T in future), so the centre of the pellet impodes and heats up under the massive pressure shock wave. Think of the pellet as a sphere of rockets all with their noses pointed to the centre. When the rockets all fire their noses are all crushed together. The centre of the pellet then heats up to the 100million degrees needed to ignite the fusion reaction (hopefully) which propagates out through what is left of the pellet like a little bomb. It is still very much debateable whether this will ever be able to break even.

[jamesr]

I definitely think we should stay on expression engine. It is very versatile, and with the add-on modules available I’m sure the site can be given a new lease of life.

A few other things that could be done is updating the member fields: remove AIM, ICQ, Yahoo etc as no one really uses them, and add a twitter username field. Then using some of the other modules available people could easily tweet about articles or other entries.

I thing the rating system & moderation will be enough to maintain the quality of blogs, rather than having everyone need special permission to post. However maybe the admins & senior members could get extra bonus ranking points.

At the end of the day what attracts people to a site is good content. Obviously the news of the ongoing focus fusion experiments is key, but also I think we need some other quality articles written on related topics to bring people in.

There are a number of members with scientific or engineering backgrounds of a level to contribute some good quality reviews. I was thinking of something we used to do at college – a ‘journal club’. Each month people were volunteered to present a review of a recent journal paper they found interesting. These don’t need to be on fusion, a link would be good though. Basically the review article should briefly explain the journal paper in as near laymen terms as possible, without dumbing down, and discuss possible implications or alternative work that is going on. This kind of quality writing, I think, will raise the profile of the site so others can link to us as a source of information rather than the other way round. If we could get 6-8 people to write a good quality article each a month it would be fantastic, and provide the fuel for the other members to discuss and comment on.

Another tier of articles could be brief guides to basic concepts in fusion physics, almost as slightly expanded glossary definitions – these will be a good basis for tags. So terms such as Coulomb barrier, or Lawson criteria have a clear definition to help educate newcomers to the field. I was thinking maybe a wiki format for this but I’m not sure.

[jamesr]

I don’t think it will be quite as simple as dropping in a new css. There will be a number of other tweaks necessary to get a consistant look for the forum & control panel.

But yes the power of css is enormous. Its good to have a separate css to handle print and mobile friendly layouts as well (ie low graphics single column).

Have a look at the expression engine Showcase, for more inspiration of what people have done running on this platform.

Its been a while since I’ve done any web development but I’ll try and have a go at one when I’ve finished my project.

[jamesr]

You need to be clear what the use will be to get the right tool for the job. If you want an everyday camera to post images & short video clips then a compact stills camera with some video capability is fine. Obviously budget is an issue so getting a bargain on last years model or dropping some fancy features may be needed, but concentrate on optical quality. Features to look out for are the wide angle limit & good macro performance – good for getting photos of the equipment from difficult angles.

However, if you want to shoot a promotional video that needs editing and higher production values then compact ‘stills’ cameras are definitely not suitable. So you may be better off getting a cheaper stills camera and dedicated video camera.

The key to getting good video for editing into a professional looking production is first choose the right format – that means plain old normal DV. The fancy MPEG4 & AVC codecs are a pain to edit. The next thing is a camera with external microphone inputs – preferably XLR. I would recommend getting lavalier lapel mics as you’ll want to cut out as much background noise as possible, and means you don’t need an extra person holding a boom. The sound quality is as critical as the pictures, if not more so. When shooting always listen through headphones to pick up the stray fridge or AC unit rumbling away (turn them off when you do a take). Lastly once edited all together, de-interlace it before encoding a version that will be uploaded to the web ( a dvd version can remain interlaced).

It would be better to get an old semi-pro video camera off ebay than buy some fancy new one that hasn’t got manual controls or decent mic inputs. Something like the Sony PD170 or the Canon XL2 (or HVR-Z1 & XH A1S for HD versions). These are obviously not cheap cameras, but as far as producing a professional quality production I think they are worth it. A good standard def camera would be a much better choice in my opinion for a promotional video than a cheap HD one.

NB. my previous job for 8 years was video/systems engineer for a post production company in London: GoldenSq

[jamesr]

Henning wrote: I’m wondering whether the pressure (about 7 torr, which is 10 mbar) would be big enough, so that any pistons are reacting at all. In the focus (a micrometer across) temperature and pressure is enormous, but outside? It’s a very small mass hitting the walls at high speed. Mechanics wouldn’t do much.

True – it was a silly idea really. The alloys used for spark plugs and chamber walls could still be useful though.

[jamesr]

I wouldn’t expect this sort of thing to be added to early prototypes. We need to prove it works & we can get the energy out first. But once we are upto the stage of wanting to pulse it at more than a few Hz then the cooling & wear rates become the next challenge.

at the 300Hz or so proposed, this equates to 18000rpm. Formula one car engines rev this high and produce stresses I would think of a similar order of magnitude. That is, the car engine produces around 1700kW of heat which is transformed into 500-700kW of useful power (source: wikipedia). A 5MW focus fusion device would be generating a similar amount of waste heat that is not in the ion beam or x-rays.

If we could take off a few hundred kW of waste heat mechanically, it will help in the whole break-even budget, and reduce the amount of heat that needs to be dumped in a heat exchanger.

At present an F1 car engine doesn’t last long, but it is experience from this kind of industry we will need to make a FF device last any sensible amount of time.

If the FF device was only pulsed at say 100Hz then the heat & rev rate will be similar to a normal road car, and these engines are built to last a long time. Basically the technology is already out there if we want it.

[jamesr]

Aeronaut wrote: I doubt it would be beneficial, James, since the design is entirely about moving magnetic fields. ‘Sides, you know what more moving parts do to MTBF and profitability projections….

There will be moving parts in the system; coolant pumps, vacuum pumps etc. (multiples of each for redundancy). I was just thinking whether modulating the pressure in the chamber over the course of the cycle would reduce the wear and load on the inner surface and components inside exposed to the few thousand degree plasma that will exist between cycles. Do the benefits outweigh the disadvantages of mechanical parts and extra complexity?

There is a comprimise between cooling the waste heat out of the plasma in the bulk of the chamber between pulses, and letting it cool too far so the it starts recombining and leaving deposits.

[jamesr]

slane wrote:
The temperatures of umbrae of the sunspots are approximate 4,500k, why do you think that the temperatures of plasmas in eyewalls of sunspots are 4,500k? The temperatures of plasmas in eyewalls of sunspots are certainly above ten million Kelvin.
The velocity of the Evershed flow of the sunspot is very large (1-9km/s).

Where do you get that temperature from??
The velocity from dopper shift of spectra lines is indeed of the order of a few km/s but this is the bulk flow of material, and nowhere near the speed te ions need to fuse.
The average energy corresponding to 10million K is 862eV ( conversion factor 1eV = 11604K). a KE of 862eV corresponds to a velocity of 200km/s. However even at that temperature only the protons at the top end of the thermal speed distribution have a chance of fusing. A proton with kinetic energy of 10keV has a velocity of 1500km/s

There no evidence I know of that the temperature at any point in or around sunspots gets this high. Indeed the spectral data gives it away a bit. At the temperatures required you cannot get spectra lines. The plasma would be fully ionised; the electrons & ions have way too much energy to recombine and give off a visible photon.

In any case the particle denisty is way too low in the photosphere to have any meaningful fusion anyway.

On a side note – do you realise how unlikely fusion with ordinary hydrogen is? the cross sections (reaction probabilities) are measured in barns (cm^-24)
at 10keV the cross sections are as follows:
for D-T = 2.7E-2 barns
for D-D= 2.8E-4 barns
p+B11 = 4.6E-17 barns
p+p = 3.6E-26 barns

at 100keV it gets a little better, esp for the pB11
for D-T = 3.43 barns
for D-D= 3.3E-2 barns
p+B11 = 3E-4 barns
p+p = 4.4E-25 barns

ie the probablility of a ordinary hydrogen (p+p) reaction is over 20 orders of magnitude lower than D-T

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