Interesting find Eric, If quenching gammas with gammas (pair production) is possible at lower energy – even at the expense of a lower cross-section rate which makes it not useful for real-world shielding– then perhaps all the money which we thought was wasted on the Tokomak and ITER etc can be put to some good use.
This would assume that Ni-H LENR cannot be made reliable enough for primetime. I can see from prior knee-jerk comments here, that this is a painful subject for a few strong supporters of LENR to even consider, since they want this to be a complete advocacy forum … which it almost is… but yet it has to be open to opinion of that which is realistically achievable, as a fallback position. Even when you acknowledge that LENR is real in principle, as most of us do - as a practical matter the technology may still not make it to market, due to inherent stability issues. In a dispassionate viewpoint – that is exactly the problem we could be facing. Do not forget the date of Rossi’s first demo, and all of the failed promises and outright falsehoods, in between. He is the clown of clowns. This is a new suggestion brought on by extending Eric’s recent find: "Automatic quenching of high energy γ-ray sources by synchrotron photons" and it is not yet well-researched by me – but is intriguing on first blush. Aside from LENR applications of gamma quenching, think about fission/fusion hybrids in a completely new light, so to speak. We realize that although lower energy gamma quenching cannot include muonic pairs, fission can occasionally do this. At over 100 MeV, muons are too heavy for pair-production from almost all photon sources except cosmic rays, but, with fast fission, muons can catalyze and perhaps be produced, since the energy yield is occasionally extreme on the Boltzmann tail of the distribution. http://www.osti.gov/energycitations/product.biblio.jsp?osti_id=255465 So one must change horses, since in this chase we are accepting gamma quenching as real, despite the lack of proof - and proceeding from there to its best implementation – which could be lower cost, safer and cleaner hot nuclear energy, with the idea that it can make a contribution even if LENR does not succeed. We all hope that the balancing act of technology advancement, does not leave hot reactions as the best choice, but forewarned is forearmed, as they say. Consider: A small subcritical, unpressurized, unshielded molten-salt breeder reactor is designed to be placed in the center axis of a modified Tokomak, which itself is below breakeven (similar to state of the art). The internal fission reactor can be a fast reactor or hybrid with low inventory and mostly thorium fueled. The tokomak can look more like a small synchrotron. It can be cooled by the same salt coolant. Gammas and neutrons from fission and fusion are mutually self reinforcing in this hybrid, so the fission can be subcritical on its own and the fusion can be below breakeven (without the gamma flux from fission, which pushes it up). Together they work robustly, but divided they fail miserably. Synergy in the extreme. In fact, a version of this general concept has been circulating for some time but, it uses a recirculating beam line, which will be completely unnecessary if active gamma shielding is real and can be incorporated: http://iopscience.iop.org/0029-5515/27/4/001;jsessionid=F7D6F34FDA33BFCA6298 EBF495E82E11.c3 This could evolve into a brilliant concept to the extent gamma quenching can be demonstrated. Note that any time you base a fission design on subcriticality, that design can be inherently clean, since the waste can always be burned in situ to achieve the subcritical criterion. That should please some of the anti-nuke crowd. You may not be aware that the fast neutrons from fusion will split non-fissile thorium in a more advantageous way than neutrons from fission split U – to provide more secondary neutrons and far more energy. Another synergy. In fact, this system might work with 90% thorium and a tiny enriched fissile core. Another synergy. Let’s hope it does not come down to a “lesser of evils” which is any hot nuclear solution, and let’s pray that LENR can be our redemption. But if not, gamma quenching might come to the rescue in a way the so-called “4th generation” fission reactor cannot (it is really a sad PR ploy by a desperate industry). And of course, hot fusion is the saddest joke of all. Jones From: Eric Walker I'm learning more and more how different the worlds of quantum mechanics and high energy physics are from that of everyday experience. There's been an ongoing discussion about the viability of "active gamma suppression," or the quenching of gammas, during a LENR reaction. This is an interesting question because its outcome tells us something about the kinds of reactions that are possible in light of the available experimental evidence. In this context the question of the viability the quenching of gammas under any circumstances is an important one. I'm starting to collect a number of interesting articles and links that seem to be relevant here, which I hope to put together in an email at some point. But before I do that I wanted to share this particular link, which seems promising: "Automatic quenching of high energy γ-ray sources by synchrotron photons" http://arxiv.org/pdf/astro-ph/0701633.pdf We investigate a magnetized plasma in which injected high energy gamma rays annihilate on a soft photon field, that is provided by the synchrotron radiation of the created pairs. For a very wide range of magnetic fields, this process involves gamma-rays between 0.3GeV and 30TeV. We derive a simple dynamical system for this process, analyze its stability to runaway production of soft photons and paris [pairs], and find conditions for it to automatically quench by reaching a steady state with an optical depth to photon-photon annihilation larger than unity. We discuss applications to broad-band γ-ray emitters, in particular supermassive black holes. Automatic quenching limits the gamma-ray luminosity of these objects and predicts substantial pair loading of the jets of less active sources. Some important details here -- the gammas that are thought to be quenched are 10 to 1,000,000 times more powerful than the ones we're interested in. So even though the conditions under which the quenching is thought to happen are extreme, these ranges also provide an upper bound that is well above what we would need. It is possible that the effect cannot be seen below these energies, but perhaps it might. The authors require a magnetic field, but they suggest that the effect can be seen between 10^-9 and 10^6 G. The lower bound, 10^-9 G, is what you find in the human brain, and the upper bound, 10^6 G, is greater than but not too different from the magnetic field of a magnetic resonance imaging machine. The authors mention in passing a related paper looking at the nonlinear effects of pair production generated by ultrarelativistic protons. A recent article at phys.org discusses how laser light coherently accelerates protons in a metal foil at higher energies than previously thought. http://phys.org/news/2012-07-higher-energies-laser-accelerated-particles.htm l So we could potentially have ultrarelativistic protons in our optical cavity, yielding pair production. The pair production cross section in nickel also becomes non-negligible in the energy range of 1 to 30 MeV. http://imgur.com/MrE0K Eric
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