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169) Laser-activated excess power

Ludwik Kowalski (8/28/04)
Department of Mathematical Sciences
Montclair State University, Upper Montclair, NJ, 07043

Looking for news about cold fusion (with Google) I found “The New Light on LENR” by Jones Beene: It can be seen at:

This recent piece( 8/17/04) is essentially a reflection on the paper of Letts and Cravens: "Laser Stimulation Of Deuterated Palladium: Past And Present." That paper was presented at the Tenth International Conference on Cold Fusion last year. It can be downloaded over the Internet as:

Beeme thinks that it is “the most important paper in LENR in 15 years.” This strong endorsment forced me read the paper again. I agree that the results are interesting but I see no evidence that they have anything to do with LENR (Low Energy Nuclear Reactions). I have no idea what is responsible for generation of excess heat; why should I assume that it is due to nuclear reactions described by Beene? In trying to answer this question I found an interesting “appeal to researchers” posted by D. Cravens and D. Letts today <>

The author of that document states that “demonstrable transmutations in suitably prepared metals have been reported recently under ‘low energy’ laser stimulation.” That is a different story; the term transmutations is commonly used as a reference to nuclear reactions. I agree with the author that a 30 mW laser beam, uniformly distributed over the area whose diameter is 2 mm, can not possibly generate stellar temperatures. But I would like to know more about the recent “demonstrable transmutations.” In their appeal Dennis Letts (from Texas) and Dennis Cravens (from New Mexico) offer other scientists a possibility to study their samples. Will presence of products of nuclear reactions be confirmed? I responded to the appeal offering an investigation with CR-39 detectors. This was a week ago. The reply came last night; I will have a chance to examine their cathode #163. Waiting for that cathode I will now start summarizing findings the Letts and Cravens.

The “appeal to researchers,” at the above URL, contains links to several pdf files with “related publications.” I downloaded the first of them: “Practical Techniques in CF Research – Triggering Methods.” This paper was presented by Cravens and Letts at the last International Conference on Cold Fusion (ICCF10). It can be downloaded from <> . the document shows that the authors have been working of the subject for 14 years and performed “thousands of experiments.” Referring to the irreproducibility they wrote: “Electrolytic cells using bulk palladium often require loading times of 10 to 20 times longer than would be expected by diffusion times of deuterium within the metal before they be expected to produce excess heat (1). This was likely the cause of failure of early researchers who rushed to replicate Fleischmann’s and Pons’ early work (2). In the first few years after the announcement, it was easier for a researcher to rush to print and claim negative results than to patiently wait until the system was fully loaded and driven into internal transitions that drive the reactions. As a result, early work more often than not failed to see excess heat.”

The introduction contains another interesting observation. Referring to Schwinger, and to more recent theoreticians, the authors wrote: “Most simple theoretical models fail to predict that nuclear reactions within a deuterated metal lattice can take place at significant rates. Such models rely on reaction rates that are based on equilibrium placement of deuterium within a metal lattice or on wave functions based on such placements. In particle models, the global average of the deuterium density within the metal is on the order of an Angstrom or more even for extreme loading ratios of D/Pd. It is clear that deuterium at such remote nuclear separations would not be expected to lead to nuclear events.

The imposition of dynamic conditions can cause the local separations of deuterium to be significantly different from the value predicted by the global density alone. It also seems that dynamic conditions provid[ing] ways for coupling of energy to drive the reactions and impurities within the lattice can allow for spin exchanges required for spin selection rules. It is a surety that the energy required to drive any nuclear events and energy released from such events are much larger than any external energy available to the deuterium based on a per atom division of energy (3). This means that any external energy driving the possible nuclear events must act in a coherent way to channel energy from a large region of many atoms to the active sites (4,5,6).

This coherent channeling must involve over 108 atoms and likely many more. The experimental conditions then must make use of non-equilibrium events acting on a system that has some group coherent nature. The methods described here are simple and practical methods that can be used to produce such dynamic conditions, which may lead to the desired nuclear events. The assumption here is that the reactive nuclear species must be driven to a dynamic active state before the desire events can produce excess energy within the system.”

This would be a good reply to those who formed their opinion about cold fusion in 1989 and 1990. But general observations of that kind do not substitute for identifying conditions under which unexpected nuclear reactions are reproducible. I have no doubt that quantitative theoretical models will be found, sooner or later, after cold fusion phenomena become 100% reproducible. Why should situations in cold fusion be different from situations in other areas of science? Let me now focus on another paper that Letts and Cravens presented at the same conference. That paper, entitled “Laser Stimulation Of Deuterated Palladium: Past And Present,” can be also be downloaded from<> . The authors discovered that laser light can trigger generation of excess power in suitably prepared materials. Here is the abstract of their paper:

“A method is disclosed to fabricate a Palladium cathode that can be electrolyzed in heavy water and stimulated with a laser at a predetermined wavelength to produce apparent excess power; the fabrication method involves cold working, polishing, etching and annealing the Palladium prior to electrolytic loading with Deuterium. Loading is accomplished with the cathode sitting in a magnetic field of 350 Gauss. After loading the cathode with Deuterium, Gold is co-deposited electrolytically on the cathode. When a coating of Gold is visible on the cathode, co-deposition is halted and the cathode is stimulated with a low-power laser with a maximum power of 30 milliwatts. The thermal response of the cathode is typically 500 mW with maximum output observed of approximately 1 watt. The effect is repeatable when protocols are followed and has been demonstrated in several laboratories.”

The constant current and voltage, used by the authors, are typically 1A and 5V. They wait till the Pd cathode is loaded with deuterium and measure the temperature of the electrolyte after thermal equilibrium is established. The relationship between the input power (in this case 5000 mW) and the temperature is known from the “isoperibolic calibration” of the electolytic cell. The loaded cathode is then exposed to a laser beam, delivering only 30 mW of power, and the new, slightly higher equilibrium temperature is established. The observed temperature change, however, does not correspond to the input power of 30 mW, it corresponds to the power of, for example, 5500 mW. Excess power, for this numeric illustration, would be 470 mW. In other words, 5030 mW input (electric+light) and 5530 mW output (thermal). The ouput is nearly 10% hogher than the input. The excess energy, Q = 2.7*t=X joules (where t is the laser-exposure time is seconds) is very small but it is probably larger than in Galvani’s experiments with frog’s legs.

What is the origin of excess power? Without having any evidence that it comes from nuclear reactions I tend to suspect that it comes chemical reactions of some kind. Perhaps chemical energy was somehow stored in the cell during the period of loading palladium with deuterium and subsequently released under laser irradiation. I know that this kind of guessing in not original; speculations of that kind were advanced as soon as the discovery of cold fusion was announced. The authors specify that to load the cathode with deuterium the current of 0.1 A was flowing through the cell for 100 hours. After that the current was increased to 1 A for 24 hours. What evidence do the authors have that a fraction of inputed energy could not possibly be accumulated, like in a car battery, before the laser beam was turned on?

I am not a chemist and I will not speculate about reactions that can conceivably be involved in the storage of energy. I would like to see the energy balance for the entire experiment. Was the average input power during the entire experiment, for example, in 100 +24 +3 = 127 hours, significantly smaller than the average output power for the same time interval? A positive answer to this difficult question, and absence of large experimental errors, would convince me that the energy storage during the loading of deuterium did not occur. On the other hand, as I indicated above, presence of nuclear reaction products, or nuclear particles, would by itself be sufficient to demonstrate that at least a fraction of excess power was nuclear. The situation seems to be the same as it was in 1989, except that the effect is said to be highly reproducible, at very low wattage levels. Is it a nuclear effect or is it a chemical effect? That is the main question.

In the section entitled “Results” the authors wrote: “It has been observed that a common red laser (30mW) when tuned to specific wavelengths appears to trigger a cathodic exothermic reaction 5-30 times greater than the magnitude of its radiant power output. The effect has not disappeared or diminished as calorimetric quality improved. It has also been observed that the magnitude of the thermal response of the cell may be altered by the polarization of the laser beam with respect to an external magnetic field.” They do not speculate on the “nature of the cathodic exothermic reaction.” They do not say that it might be nuclear. But the phrase “nuclear events” does appear in their papers. I will assume they think that the reactions are nuclear. The papers were presented at the cold fusion conference and “cold fusion” is often described as a new kind of nuclear reaction.

I suppose that better “calorimetric quality” refer to more accurate calorimetry. The numbers 5-30, on the other hand, refer to ratios of excess power over the laser beam power. These numbers show that small powers trigger releases of much larger powers. Let me turn to two other observations made in the paper: the effect of the magnetic field on the loading of deuterium into palladium, and the effect of polarization of laser light (with respect to the magnetic field) on excess power. In the section entitled “Experimental” that authors wrote: “ We think the magnetic field improves the loading of deuterium.” I suppose that the phrase “improves the loading” is meaningful to a chemist. The magnetic field strength, at the cathode submerged in the electrolyte, was 350 Gs. This is only several times larger than the terrestrial field. How can loading of deuterium be influenced by such field? How did the D/Pd ratio differ between loading with and without the magnetic field? These questions alone can become subject of a doctoral dissertation.

The same is probably true for the effect of light polarization. The section devoted to this subject begins with the following statement: ”During the course of experimentation it was discovered that polarization of the laser beam can dramatically affect the thermal response of the cathode to the laser beam. Cravens observed during one of our runs that when the laser beam polarization is perpendicular to an external magnetic field, the thermal response of the cathode is maximized.” I suppose that both authors observed the effect in subsequent experiments; a single observation of something unusual would not be trustworthy. The effect of polarization is described in the caption of Figures 10. It is difficult to understand this effect without first understanding the effect of the magnetic field on triggering excess energy. (It seems that the magnetic field plays a role not only in loading but also in what happens after loading.) Accepting experimental data, as reported on Figure 10, one has to face a difficult task of understanding what was going on.

Figure 11 introduces another complicating factor. “The cathode didn’t respond well to the laser stimulation until the rare earth solution was added to the electrolyte. With the additive, the cathode became responsive to a laser operating at 657nm with a radiant output of 30 mW.” The nature of that additive is not specified in the paper. In the caption of that figure the authors state that the “power to the cell was constant at 7 +/- .01 watts.” That shows that the excess power was, at the highest point, equal to 10% of the input power. In the remaining part of this section the authors state that the effect was witnessed by four invited scientists. I do not think that this refers to the effect of polarization. It probably refers to the effect red light on the excess power (at constant polarization). For how long would the excess power be generated, after 2100 hours, if the laser beam was not turned of? My guess is that chemical reactions taking place in the cathode eventually destroy it. Is it possible that the observed excess heat is due to these reactions? Were the effects of polarized light on the yields of chemical reactions studied in other contexts? I do not know how to answer such questions.

The most recent paper of Letts and Cravens, as far as I know, was presented at the ASTI Conference in Italy (19-21 March 2004). The link to that document is available in

The abstract is essentially the same as in the ICFF10 paper. Most of what I see in the last paper has already been communicated in the two papers to which I referred above. Graphical illustrations of seventeen cathode-preparation steps (previously described in words only) will certainly be appreciated by those who are interested in studying the unexplained Letts-Cravens effects. Some statements, however, are new. The authors wrote, “We did a series of experiments that replaced the LiOD with LiOH. It was clear that the LiOH did not yield any excess [energy].” That is a very significant experimental fact. They also wrote: “There seems to be a relationship between the temperature of the metal host lattice and the wavelength needed to trigger the effect. . . . There are runs where we see no excess [energy] until the correct wavelength [from a tunable laser] is reached. It is very reassuring to see excess heat response when the wavelength of the laser is altered by only a few nm. It is also hard to conceive of a calorimetric error that is so wavelength sensitive.” I agree with this observation.

Referring to the effect of magnetic field on excess heat, and to the effect of polarization, the authors wrote: “Our better experiments have been with cathodes that were initially loaded in the presence of an external field. Often the excess heat is dependent on the relative angles between the linear polarized lasers and the direction of the magnetic field applied when the metal was first loaded. Again, it is hard to conceive of calorimetric errors that would change with the rotation of a laser outside the controlled environment or the insertion of a quarter wave optical plate in the beam. The maximum effect coincides with the E field of the polarized laser being perpendicular to the magnet field.” This implies some kind of magnetically induced alignment on the cathode during its loading with deuterium. Was the magnet, located outside the electrolytic cell, removed after loading? I assume it was. The word “often” is reassuring; it shows that the effect of laser light polarization on the excess power was not a single observation.

The issue of nuclear versus non-nuclear origin of excess power was not addressed in this paper, except indirectly by telling us what happens when the LiOD electrolyte was replaced by LiOH electrolyte. Isotopic effect on chemical reactions, if any, are extremely small. Another issue that was not addressed has to do with duration of excess power runs. I would like to know, for example, why the laser had to be shut off after about 150 minutes in the experiment #560 (or after 3900 minutes in the experiment #587). I would also would like to know which “hidden variable” was responsible for the fluctuations of excess power (between 100 mW and 800 mW) in the experiment #587. The laser beam was presumably stable during the entire 5900 minutes interval.

I have no doubt that the authors are also interested in “hidden variables.” Hopefully their more recent experiments will lead to better understanding of the cause-and-effect relations in this fascinating area of science. Asking questions is easy, answering them is much more difficult. Identification of hidden variables has been the major preoccupation of scientists involved in cold fusion experiments. The progress would be more rapid if the area was not declared to be pseudoscientific. Methods of validation used by individual researcher must always be questioned; condemning that entire field as pseudoscientific is not justifiable, in my opinion. Papers like those of Cravens and Letts should not be rejected by editors of mainstream journals; they should be allowed to undergo the usual pear review process. Financial support of research should be allocated to cold fusion researchers in the same way as in any other area of science. Will the situation change after the ongoing DOE investigation is over? I hope so.

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