What might be going on in LENR (2)

Here is an update on an idea set out in an earlier post describing some of my more recent thinking on what might be going on in LENR.

I have put together a graphic to capture where my thoughts are currently going:

Here the small molecules are molecular hydrogen, the red particles are protons and the blue area at the left is the surface of a nickel metal grain.  A spark discharge is underway between this grain and another grain nearby (not pictured).  Prior to the discharge the two grains were electrically isolated.  The discharge is drawing the protons into a recess in the metal grain, where a great deal of pressure is building up.  If this process happens sufficiently quickly, e.g., before there is a lattice dislocation, perhaps the pressure could get quite high.

Here is where I think an insight of Ron Maimon's might be applicable [1].  If the pressure is high enough to cause a d+p reaction, or perhaps even a nickel proton capture reaction, normally one would expect a gamma.  But the emission of a gamma is a very slow process.  Because the environment is electron-rich, and because the electromagnetic interaction proceeds quickly, under suitable circumstances it will be competitively favored over the emission of a gamma, which will take a long time.  If so, my take on and adaptation of Ron's insight is that perhaps the [pd]* or [pNi]* intermediate state will couple with the surrounding electronic structure and possibly positively charged lattice ion cores, and the energy that would normally go into the emission of a gamma will instead be divided among a large number of recipients and result in a bath of low-energy photons.

A counterargument can be made that radioisotopes found within metals commonly emit gammas, so there is no reason that coupling with the electronic structure should happen in this particular case instead.  I do not have a strong response to this complaint and only observe that the emission of a gamma from a metastable radioisotope seems to be a sufficiently different situation from the decay of a short-lived fusion intermediate state to suggest that something else might happen in the latter case.

[1] He's looking at a very different system that involves palladium and deuterium, and he makes no claims in connection with the current discussion.  Do not be distracted by Ron's reputation of 1—this goes back to events unrelated to the quality of his posts, and previously he was one of the highest ranked contributors at physics.stackexchange.com.

What might be going on in LENR

Here I'm going to schematically lay out what I think might be going on with LENR, on the assumption that it is nuclear in nature.  We will proceed in six steps.

Step 1:  fusion precursors are far away from one another in the context of an environment at the surface of or a few layers into a host metal, and the likelihood of fusion is negligible.  For the sake of illustration, we'll consider hydrogen and deuterium.

The blue gradient represents the electron charge density.  The closer free atoms get to the lattice sites in the host metal, the stronger the charge density and the more the electrons on the atoms are stripped off and the atoms behave like ions.

Step 2:  a transient in the charge density forms somehow; perhaps there has been a spark discharge:

As a result of the transient, the charge density becomes very high; simultaneously, any atomic hydrogen and deuterium nearby are ionized.

Step 3: the negative charge of the transient becomes so high the now-ionized p's and d's are attracted to and cluster around it.

The ions are so strongly drawn in by the transient that they are brought into close vicinity to one another as well.  The stronger the transient, the closer they are drawn; the longer-lasting the transient, the longer they will remain nearby one another.  A z-pinch might also be involved here, in which a confining magnetic field is formed by current.

Step 4: the likelihood of a p and a d tunneling is a function of their proximity to one another and the amount of time that they linger.  Suppose the strength of the transient and its duration are sufficient to allow tunneling of one of the p+d pairs.  The result is a very unstable [pd]* resonance that will quickly decay:

Normally in such an event, the [pd]* that forms would decay into a 3He (an isotope of helium) and a gamma photon, which would be straightforward to detect.  But this description pertains to what we currently know of the p+d fusion branch seen in pressurized plasmas and ion beam experiments.  We are less familiar with what goes on in solid-state system such as a host metal, where the electronic structure is quite different.  When a fusion reaction takes place in an electron-rich environment, there is reason to think that no gamma will be emitted.

Step 5:  instead what might happen is the momentum of the reaction ends up being divided among a large number of electrons in the area, immediately resulting in the emission in every direction of a corresponding number of lower-energy photons:

Step 6:  after the transient has subsided, what is left over is heat from the bath of lower-energy photons together with a slow-moving 3He daughter:

Here no gamma photon has been emitted.  One can imagine a similar process taking place with d+d or even p+Ni precursors, with environmental parameters determining the likelihood of various outcomes.

LENR and thermionic emission

In a post to Vortex-L a few days ago I described some of my recent thinking on what is going on with LENR.  The post focuses on some fusion branches involving gamma rays that have bedeviled anyone trying to understand the LENR experimental data.  Two, in particular, are:

1. d + d → 4He + ɣ (23.8 MeV)
2. p + d → 3He + ɣ (5.49 MeV)

The main reason these fusion reaction branches pose a difficulty is that branch (1) is believed to be involved in LENR in the context of PdD, somehow, through some process, whether directly or indirectly, and yet no gammas are seen.  And (2) has recently come up as a possibility for LENR in NiH.  People involved in trying to explain LENR have taken various roundabout ways to get around the problem of missing gammas, including Bose-Einstein condensates in which four or more deuterons fuse simultaneously.

The message to Vortex summarized points from an ongoing discussion I've had with Robin van Spaandonk concerning a proposal set out by Ron Maimon.  Ron suggested in a post to the physics site physics.stackexchange.com in 2011 that what is going on in LENR is that the energy that would normally be emitted as a gamma in fusion reaction (1), above, is instead transformed into kinetic energy upon the decay of a short-lived [dd]* resonance that is created from the fusion of two deuterons in close proximity to a palladium lattice site, brought about in a very specific way.  In broad terms, Ron proposes that the behavior of reaction (1) is different in close proximity to a palladium spectator nucleus than when it occurs in a plasma or in a vacuum.  Because the electromagnetic dumping of the mass energy of the [dd]* intermediate state into a nearby source of electrostatic charge such as a palladium lattice site would be much faster than the emission of a gamma photon, it would be competitively favored.  Since the process is also faster than the two other known dd fusion branches, it would compete favorably against them as well.  The result would be a 4He daughter that pushes off of the palladium lattice site with 22.9 MeV of energy, instead of a prompt gamma, a triton and a proton, or a 3He and a neutron, products that are known from existing dd fusion experiments.

In the Vortex thread, Ron's idea has been taken and modified a little.  I suspect that the transfer of energy via the electromagnetic interaction can also happen with the electronic structure of the palladium metal, far away from the lattice sites.  If this were to happen, and there is reason to think it would be the dominant outcome, the momentum of the reaction would be absorbed either by an ensemble of electrons in the local system or by a single electron, and the daughter 4He would be almost motionless.

Somehow this disruption of the local system would then feed back into the reaction.  I suspect that this occurs by a modification of the electronic structure of the palladium lattice; in fact, of that of any metal and not just palladium.  The form of the disruption is perhaps a change in the charge density in the lattice.  Normally most of the electrons in a metal are tightly bound around the lattice sites.  The disruption would be to somehow modify the charge density so that some of the electron orbitals extended out into the interstitial areas, where the deuterium and hydrogen nuclei are.  The electrostatic dumping of energy upon the decay of the [dd]* intermediate state would somehow propel this process forward.  An early source of the idea that charge density might play a role in cold fusion was a paper written by a group at UC Berkeley in 1989, when a large number of people were trying to understand the results of Pons and Fleischmann.  The Berkeley group do not appear to have taken into account the possibility that the charge density could be modified under certain conditions, however.

Getting the cold fusion process started would presumably require something other than fusion.  I suspect in the case of Andrea Rossi's E-Cat and possibly Defkalion's Hyperion that this is through the agency of a thermionic emitter, which emits beta particles when heated up sufficiently.  These devices could be using a compound such as lanthanum hexaboride, for example, whose properties are similar to those of modern lighter flint.  As the heat of the substrate is increased by resistance heaters, or the thermionic emitter is stimulated by spark plugs, the compound would start to give off beta particles.  Once that happened perhaps the charge density of the electronic structure of the metal lattice would be modified in some as-yet-unknown way, and dd and pd fusion would become many orders of magnitude more likely.

Ron Maimon does not like the idea of electron screening playing a role, for he believes it does not work at the scales involved in fusion (his explanation can be found in the comments here).  But I suspect there is something like this going on, and that it can be effective, for the mechanism of the Polywell reactor works on a similar principle, and the explanation as a whole provides a very good phenomenological fit with the experimental data along a number of lines, including the observation that 4He appears to be born with almost no energy, as seen in a lack of Bremsstrahlung and prompt radiation.

So if modification of electron charge density or something like the mechanism behind the Polywell reactor is occurring, it might be possible to catalyze it using a thermionic emitter.  What is interesting in this connection is that researchers have noted a possible connection (p. 219 ff) during electrolysis between oxide in the substrate and excess heat.  Elsewhere I have learned that oxidation can sometimes lead to a lower work function, which is what is behind thermionic emission.  This is, then, another detail that points in the direction of this general line of investigation.

Ron Maimon's theory (2)

In a previous post, I attempted to provide a layman's overview of a theory put forward by Ron Maimon concerning what is generating anomalous heat in the palladium deuteride LENR experiments.  The theory, which I have nicknamed a theory of "Auger deuterons," nicely incorporates the primary elements of the signatures seen in many of the Pd/D experiments:

• Heat
• Broadband x-ray spectra
• Fast alpha particles and protons
• 4He off-gas
• Transmutations of various kinds

Part of the motivation for the earlier blog post was to get feedback from people on vortex-l, and as I hoped would happen, Robin, who is on that list, pinpointed several difficulties that needed to be addressed.  Here are questions from him (1 and 2) and me (3 and 4) that resulted from the thread:

1. How do two deuterons approach the Pd nucleus concurrently, as this seems a very unlikely thing to occur?
2. The d+d fusion cross section becomes negligible below 5 keV.  Assuming a loss of 400 eV per palladium atom that a 20 keV deuteron passes through as a result of interactions with its electrons, the energy of the deuteron will drop below the 5 keV threshold after passing through 38 palladium atoms.  In the unlikely event that it hits another deuteron head-on before that, even then a fusion is not assured.  So all-in-all the likelihood of a self-sustaining reaction seems small.  How can one be obtained under these circumstances?
3. The regular branches for d+d fusion are (a) d+d→t+p (50 percent), (b) d+d→3He+n (50 percent) and (c) d+d→4He+ɣ (almost negligible).  What causes branches (a) and (b) to be suppressed and branch (c) to become dominant?
4. When you have fast particles flying through a deuterated metal lattice, a particle is likely to bump into a deuteron, and it in turn will hit another deuteron. Occasionally a side reaction of branch (b), above, will occur, yielding a significant number of neutrons which would then exit the system.  But neutrons are only rarely seen and at levels barely above the sensitivity of the neutron counters.  For this reason Peter Hagelstein places a 20 keV upper limit on the energy of the particles in the system.  Ron's account involves alpha particles with energies of tens of MeV, so the lack of neutrons from side reactions on an order above that currently seen could be expected, presenting a challenge to be addressed.

The full vortex-l thread can be found here.  I am sure that the difficulties go back to my own understanding and have been anticipated by Ron.  I will be interested to hear how he addresses them, especially (3).

EDIT: Concerning items (1) and (3), above, Ron addresses these questions in his original physics.SE post:

The fusion of deuterons always happens through unstable intermediate states, and the cross section to alpha particle is only small because of the same non-relativistic issue. To get an alpha, you need to emit a gamma-ray photon, and emissions of photons are suppressed by 1/c factors. When there is a nucleus nearby, it can be kicked electrostatically, and this process is easier than kicking out a photon, because it is nonrelativistic (the same holds for an electron, but with much smaller cross section due to the smaller charge, and there is no reason to suspect concentration of wavefunction around electron density, as there is for a nucleus). 

The time-scale for kicking a nucleus is the lifetime of the two-deuteron resonance, which is not very long, in terms of distance, it is about 100 fermis, this is about the same size as the inner shell. If the deuterons are kicking about at random, this coincidence is not significant, but if the deuteron-hole excitations are banded, it is plausible that nearly all the energetic deuteron-deuteron collisions take place very close to a nucleus, as explained above. 

There are conservation laws broken when a nucleus is nearby. The nucleus breaks parity, so it might open up a fusion channel, by allowing deuteron pairs to decay to an alpha from a parity odd state. Such a transition would never be observed in a dilute beam fusion, because these fusions happen far away from anything else. This hypothesis is not excluded by alpha particle spectroscopy (there are a lot of relevant levels of different parities), but it is not predicted either.

This only hints at an answer to question (1), by saying that the banded state makes it "plausible" that the energetic deuterons will encounter one another near a palladium nucleus.

Ron Maimon's theory of Auger deuterons

There are plenty of theories available to explain some or most cold fusion experimental results, but none of them has gained general approval among cold fusion researchers. The rudiments of a less-known but interesting theory have been proposed by Ron Maimon, who up until the end of 2012 was an active participant on physics.stackexchange.com.  The theory goes well beyond my knowledge of nuclear physics, but I was able to get ahold of some details about it that make it more recognizable to a hobbyist like myself, which are mentioned in this Stack Exchange chat transcript.  Prior to the chat with Ron I participated in an interesting discussion with Robin van Spaandonk, on the Vortex list, about some of the details of the theory as set out in the reply to the physics.SE question linked to above.  Robin is knowledgeable about nuclear physics, and the discussion helped me to know what to ask later when I was talking to Ron.

The basic mechanism occurs when a K-shell electron is kicked out of its orbit around a heavy palladium atom in the metal lattice.  That in turn creates a hole which can decay in various ways; normally it will decay either through an electron from another orbital filling the hole with a subsequent x-ray photon emission or, alternatively, through the ejection of an Auger electron.  The energy involved in the decay of such a K-shell hole is on the order of 20 keV, an amount sufficient to cause two deuterium nuclei to fuse a significant portion of the time in a beam of deuterons.

Ron posits that when a deuteron is in the immediate vicinity of a palladium atom from which a K-shell electron has been ejected by action of an x-ray or a traveling alpha particle, the deuteron will preferentially receive the energy of the K-shell hole decay via electrostatic repulsion, thereby gaining 20 keV of energy.  This makes the deuteron in a sense an "Auger deuteron." Should it fuse with another deuteron, the Q value of the reaction will be a very large 24 MeV, which will be shared with the daughter alpha particle and the spectator palladium atom.  If I have understood Ron's account, there will be no gamma photon, as the reaction will have occurred close enough to the palladium atom for it to share in the momentum of the daughter alpha.  The fusion cross section will be enhanced in the case where two energetic deuterons approach a palladium atom simultaneously; at the "classical turning point," i.e., the point at which the electrostatic repulsion of the positively charged palladium nucleus will start to push the approaching deuterons away, they will be in close enough to one another, as Ron alludes to and Robin clarifies, for their de Broglie waves to overlap enough to possibly result in a fusion.

Occasionally a fast daughter alpha particle will interact with a spectator palladium atom, causing it to gain or lose some number of nucleons and resulting in a transmutation to another element.  This is understood to be a side channel and not the main source of heat. The reaction is sustained as a result of the energetic daughter alpha racing through the lattice, ionizing palladium atoms as it travels, triggering in turn the mechanism described above.  According to this theory, the things to look for during and after anomalous heat are x-rays, helium and transmutations certain numbers above and below the mass of palladium.

An issue that Robin had with Ron's theory is that he thought that the ionization caused by the traveling alpha particles would be too inefficient to result in enough K-shell holes.  But he also pointed out that, if something like this were happening, you might see a similar effect in the nickel/hydrogen system. In that case it would be the fraction of deuterium in light water interacting with energetic protons, rather than p+p fusion, that would be taking place.  If I have understood Robin, an attractive detail of Ron's Pd/D-focused theory is that it potentially provides a way to keep the energy needed for D-D fusion around long enough to sustain a continuous reaction.

Vortex-L temporarily down

The Vortex mailing list is a list that I've been following for over a year now.  The list was started in 1995 and is one of the best places for the general observer to get the latest news about cold fusion.  The subject matter ranges far beyond cold fusion, however, and gets into some pretty wild topics, such as the Papp engine and magnet motors, which can be quite entertaining to learn about.

Unfortunately the list was suspended recently after a prolonged dispute.  Hopefully it will be brought back up soon.

The Martin Fleischmann Memorial Project

At a conference this year, Francesco Celani, a cold fusion researcher, demonstrated a novel wire reactor apparatus.  The apparatus showed what Celani believes to be clear evidence of anomalous heat—more energy coming out of the device, over time, than has been put into it, a central claim of Fleischmann and Pons.

The Martin Fleischmann Memorial Project is a project that started up this year with the aim of assembling a kit that will replicate Celani's experiment.  Celani's device consists of a long glass tube with specially treated wire coiled around a rod of sorts contained within the tube (the composition of the wire is a secret).  The effect is seen when the glass chamber is filled with hydrogen and a current passed through the wire.  Once the Martin Fleischmann Memorial Project have the design worked out for their kit, they will make the kit available to universities and third parties for study.

The project's intention is to be transparent in everything they do, and in this spirit they're keeping a regular blog of their progress and are making their data available.  In one of their blog entries, they show a graphic of impedance in the wire versus the temperature in one of the thermocouples over a number of calibration runs.  I downloaded their data and put together the same graphic:

One detail that stands out right away is that they are smoothing their graphs somewhat.

The following columns are available in the calibration data sets:  Date, T_Board, T_Mica, T_GlassIn, T_Well, T_GlassOut, Pressure, Current Blue, Voltage Blue, Power Blue, Impedance Blue, Current Red, Voltage Red, Power Red, Impedance Red, T_Ambient, Pressure, Total Power, T_Mica Rise, T_GlassIn Rise, T_Well Rise and T_GlassOut Rise.

The blog entry with the graphic mentions that an error of +/-3 percent has been calculated with a 95 percent confidence interval from three identical runs (which statistic is being analyzed is not yet clear).  This error level means that they will be looking for at least 3W excess power.  I would like to try to duplicate their calculation of the error.