What Ever Happened to Cold Fusion? Roy W. Clark Middle Tennessee State University, Murfreesboro, TN 37132 The hot science topic of 1989 was cold fusion. The term, as used by the press, refers to the electrolysis experiments reported by Fleishmann and Pons ( I ) in March of 1989 and to similar experiments by Jones (2) that were reported almost simultaneously. Fleishmann and Pons reported excess heat, neutron emissions, and radiation in the gamma ray region. Jones reported only neutron emissions, and these in much smaller amounts. T o the average chemist this report meant that chemists had done what physicists had been unable to do in 50 years of hot fusion experiments, namely to fuse hydrogen nuclei in a controlled manner to form helium nuclei, thus liberating energy of great potential value. To skeptical physicists this meant that chemists did not know how t o make neutron measurements and were probably misinterpreting their thermal measurements. Chemistry and physics are not very different sciences. The overlap between them is enormous and growing. The cold fusion reports seemed to polarize these two fields like nothing in recent memory. Physicists were skeptical, chemists optimistic. Over a year has now passed, and it is time to look back and see what did happen and why a simple electrochemistry experiment can be so controversial. Cold Fusion before 1989 Physicists do not doubt that cold fusion of hydrogen isotopes to helium is possible. They predicted i t ( 3 , 4 )in 1947 and discovered it experimentally in 1957. This discovery by Alvarez and co-workers (5)a t Berkeley was made in a liquid hydrogen bubble chamber a t about 30 K, truly cold fusion. No electrolysis experiments here; this cold fusion was muoncatalyzed fusion, now commonly called pCF. If the traces in the bubble chambers are being correctly interpreted, this cold fusion really works. I t fuses deuterium nuclei to tritium nuclei, liberating the expected energy. I t is a reproducible experiment. So why is i t not solving the energy problems of the United States? Because t o generate a muon using an accelerator requires about 8 GeV of beam energy, and the negative muon produced catalyzes fusions that release only 2.5 GeV. So far the pCF process is scientifically interesting, but commercially discouraging. Muon-Catalyzed Fusion Before returning to the Fleishmann, Pons, and Jones electrolysis experiments, it will he helpful to understand what physicists think is going on in pCF. There is some truly unusual chemistry in this process. The discussion here is quite abbreviated, so the reader is referred to references 6 and 7 for more detailed discussions. Imagine a nuclear accelerator attached to a bubble chamber containing liquid hydrogen predominantly in the form of ZHand 3H isotopes, which we shall abbreviate to D and T. The liquid consists of Dp, DT, and Tz molecules. The nuclear accelerator creates a negative muon. This is a subatomic particle identical to the electron except with a mass 207 times that of normal electrons. The high-speed muon crashes through the liquid in the bubble chamber, slowing down by ionizing molecules in its path. When i t has slowed to 10 eV, i t takes the place of an
electron around a deuteron. I will represent the deuterium atom as D, the deuteron as d, the electron as e, and the negative muon as p. N+D-dp+e
(1)
The muonicatom formed is not in its ground ntate. It is in its n = 14 state. because in this state it is about the same size as the electroiic atom it replaces. When i t falls to its ground state, it has a size much smaller than the typical deuterium atom. Its orbital radius is 207 times smaller'. At this point should the muonic atom meet another muonic atom like it, they might fuse to form helium because of the closeness of approach of their nuclei. Such a meeting is too improbable, however, so the muonic atom makes do with what is available. More probably it exchanges its muon with a tritium nucleus to form the more stable t muoatom. Then this electrically neutral t p wanders about among the Dp and DT molecules until it attaches itself to a d inside one of these molecules. This nucleus now becomes part of a dty muomolecular ion. Since it is very small and positively charged, the molecule sees this muomolecular ion as a nucleus. The process can be envisioned as: t~
+
-
EZ3
w
The product molecule, with the dtp as one nucleus, forms in its u = 1, J = 1 vihration-rotation state. When it loses energy to drop into its J = 0 state, the repulsion of the neighboring d, added to the shielding of coulomhic charge by the muon, is sufficient to cause fusion of the d and t in the muonic ion. Energy is liberated and a helium nucleus is formed. Ideally, the muon is regenerated to catalyze another fusion. Since the muon is regenerated, it would seem that, unless it escapes from the chamber, i t would catalyze the fusion of many more d t pairs. Unfortunately, there are two problems that limit the muon as a catalyst. The first problem is that the muon is an unstable particle. I t decays with a half life of only 2 ps. If i t is to cause many fusions it must hurry before i t decays into a normal electron plus two neutrinos. Even so, the preceding events happen so fast that a muon could catalyze hundreds of fusions before i t dies, were i t not for another problem. The other prohlem is called "sticking". The muon sometimes sticks to the He nucleus, rather than going off to do more catalysis. Conditions that minimize "sticking" are being studied. Nuclear physicists have experimented with this exotic series of reaction kinetics for 30 years. There is still some understanding of these molecular and nuclear events that remains to be achieved. If understanding comes, then cold fmion will mean muon-catalyzed cold fusion, and commercia1 application would he p&ihle, though by no means a certainty.
' The orbital radius is inversely proportional to the mass. Volume 68
Number 4
April 1991
277
-
A Physlclst Turns to Electrochemistry
Steven E. Jones is a physicist and is now at Brieham Young University. ~t t h e ~ oAlamos i Meson Facility i 2 9 8 2 Jones and co-workers, experimented with the conditions for optimizing the fiCF process by varying temperature and pressure conditions. They were able to achieve 150 fusions per muon. Thus Jones had been deeply involved in cold fusion long before the events of 1989. In collaboration with colleague Paul E. Palmer at BYU, Jones began to pursue the idea that cold fusion might have something to do with the generation of heat inside the Earth's mantle. There were some geological explorations that had suggested the presence of 3He.. a . nroduct of ~- one ~ route of coldfusion, in undersea hot water plumes and also in volcanic gases. In 1986 Jones, Palmer, and John Rafelski, a theoretical physicist from the University of Arizona, all considered the idea that cold fusion might haopen in hiehtemperature and high-pressure con&tioni-under c o t springs. This lead to the idea of loading absorptive electrodes with deuterium by electrolysis, using an electrolyte composed of heavy water containing several salts found in hot springs. To detect whether or not fusion took place in these cells, Jones chose to look for neutron emission. Bart Czirr and Gary Jensen in the BYU physics department were developing a sensitive neutron detector then. and so were broueht 01~10 the team. This was the activity gbing on at BYU in [Ate 1988 when Jones first heard of the ideas of Pons and Fleishmann a t the nearby University of Utah chemistry department. Electrochemlots Turn to Physics Stanley Pons and Martin Fleishmann were electrochemists who had been quietly working on a similar idea since 1985. This was the idea that deuterons could be brought close enough together for cold fusion by introducing them into the interstices of oalladium metal. For a eeneration i t had been known that palladium metalhad the &usu&roperty of absorbing hydrogen gas into itself (probably as the atom rather than the molecule). Using palladium as the cathode in electrolvsis was the technioue for loadine valladium with hydrogen. With this in mini, they had conducted experiments in which DIO and LiOD mixtures were the el&rolyte in a cell with platinum anode and a palladium cathode. Adeuteriumatom rhnt diffused intosuchacathode would essentially be a deuteron immersed in a sea of palladium electrons. The idea was that the screening effect of the electrons might make the deuterons approach each other closely enough for fusion, despite the repulsion of like charees. Their exneriments had been self-funded because they-did not want'the public exposure necessitated by grant anvlication. However. bv 1988 this vublic exDosure became i&vitahle. Pons a n d ~ieishmannLad been getting sufficiently encouraging results that they applied for a grant from the U.S. Department of Energy to fund their research. This erant proposal was sent, as fate would have it, to Steven jones for review. Jones was astounded, for when he received the proposal for review he was already scheduled to present a paperon electrolytic cold fusion to-the American Physical Society. Amazed that this similar work was going on 50 miles away, Jones contacted Pons and arranged a meeting of the two groups. Jones's idea was that they might share equipment, such as his new neutron detector. Pons, it turned out, was s in sharine" more concerned about nrioritv and ~ a t e n t than equipment. There were some personality problems, which historv will have to unscramble later. Nevertheless. the result oE these meetings was an agreement to submit papers simultaneously from the two groups on a specific day. Jones, Pons, and Fleishmann ultimately agreed that on March 24, 1989, they would meet at the Federal Express office and send off their papers to Nature. ~
~
~~~
~
~
a
278
Journal of Chemical Education
~~
This aereement was not honored. For details see the book by Peat (8).Ponsand Fleishmann held a press conferenceon March 23, and Jones sent his paper to .Vuture that sameday. What Fleishmann and Pons Reporled2 The Fleishmann and Pons electrol).re was 0.1 M LiOD in 1):O. The anode was platinum: the cathode palladium. Thev reported excess heatgeneration; that is, mire heat out than electrical energy put into the cells. They also reported a gamma ray spectrum that they attributed to product neutrons"eacting with the water bath protons. p -
~
+n
-+ d
gamma ray photon
(3)
The group used a liquid scintillation counter technique to detect the rate of accumulation of tritium4in the electrolyte. They reported low levels of neutrons and tritium; levels that were inconsistent with the high excess heat. Their paper suggested that a hitherto unknown nuclear reaction was taking place that did not generate neutrons and tritium, but did produce much of the heat. Since their vublication ( I ) . the eamma rav spectrum and the neutron counting tecidique of their exp&iment have come under some criticism, and Pons is reported (9) to have said that he bad little faith in these results himself. They steadfastlv claim that the excess heat being zenerated in some exp&ents is real, and not due to anychemical reaction that might follow the electrolysis. What the Jones Group Reported At BYU the Jones group used an electrolyte much different from that of Pons and Fleishmann. Jones's electrolyte was a salt mixture dissolved in D7O. I t was intended to simulate the composition of typical~olcanichot springs, and included compounds of iron, nickel, palladium, calcium, lithium, sodium, titanium, some nitric acid, and a dash of AuCN. As cathodes, they used titanium as well as palladium. Gold foil was used as the anode. They placed their electrolytic cells directlv on too of a sensitive neutron counter. Their measurements were of neutrnn flux, not of heat production or tritium appearance. 'l'hev reported a small but statistically significanineutron flux as the electrolytic cells operated. Their neutron flux u,as seven orders of magnitude less than that renorted hv Pons and Fleishmann. The Jones erouv ~.~ -~ . makes no claim to have produced commercially viable power production techniques. ~
.~ -
Reproducing These Experiments
In the year and a half since these two results were disclosed, chemists and physicists worldwidehaveattempted to reproduce them. Most have failed. Some investigators have reported neutron production but no excess heat. Others reported excess heat but no neutrons. No one to date seems to be able to make their electrolvtic cells nerform on demand in such a way as to convince o&ers that'fusion is occurring in the cells. A Dialog search of the chemistry and physics literature conducted in May of 1990. 14 months after the cold fusion publicity, resulted in 235citations under cold and fusion during this period. Of these, 17 were reporting confirmatory results encouraging to cold fusion advocates, 50 reported negative results, 109 were either theoretical speculations on po&ible nuclear react,ions which might account for these results, criticisms of technique, or speculations on chemical or other explanations of the cold fusion effects. Forty-two of the citations were not about electrolytic cold fusion a t all but were about other cold fusion techniques. These included
-- + +
Graduate student M. Hawkins was added as an author to paper in an addendum. Presumably due to d d =He n. 'Presumably due to d d t p.
++
this
UCF,of course, hut also interesting indications of fusion via low-energy accelerator experiments. An example is a report (10) from Brookhaven Laboratories on the results of striking a-~ deuterium-loaded titanium tareet with a beam of h e a w water clusters: Fusion is reportez to he evidenced by thk detection of 3-MeV protons. ~~
~
~
Cold Fusion b Heaw Element Production
Cold fusion as a key word will also produce papers relating to the production of superheavy elements hy accelerator techniques. Apparently some of the building processes in these reactions. such as the production of element 104, are classified as "cold fusion" because of the low energy of the particles involved. This type of cold fusion seems far afield from the electrolytic cells of Pons and Fleishmann hut may serve as an example of nuclear fusion processes that overcome the coulomb harrier by mechanisms other than brute force.
"cold fusion". If the term is used to mean the electrolytic experiments of Pons and Fleishmann using D20 and palladium electrodes, then there seems little doubt that these experiments are very difficult to reproduce. Many would argue that the heat produced can he explained in ways other than by assuming nuclear reactions. The tiny neutron flux reported by the BYU group is equally difficult to reproduce, primarily because it is on the edge of the neutron counting threshold. In a broader sense, "cold fusion" is certainly a demonstrated phenomenon. Muon-catalyzed cold fusion exists, and there is some indication that accelerator experiments can initiate nuclear fusion at lower energy than was previously thought possible. Perhaps in the near future all of these different experiments will he looked upon as clues to some fundamental property of atomic particles, a property waitine to he discovered. When that discoverv. comes. the mysteFy of cold fusion will at last be solved.
Cold Fusion Conference
In March of 1990 a conference was held at Salt Lake Citv, Utah, that was called optimistically "The First Annual con: ference on Cold Fusion". At least six groups a t these proceedings reported excess heat generation, three detected tritium production, and four found neutron emission. One participant a t this meeting (11) concluded that "the general consensus of the meeting was that the cold fusion effect is real, hut we need to find t h e triggering mechanism."
1. Fleirchmann.M.:Pons.S.; Hawkins, M. J.El~ctroano1.Chem. 1989,261.301308snd an appended erratum. 2. Jones, S. E.: Palmer. E. P.; Czirr. J. B.; Decker. D. L.: ense en. G. L.: J. M.:
~~
5 . Alvaren.
~
~
~
~
~
..., ~ ~ , ~ . .
i.W.; Bmdner, H.: Crawford. F. S.: Crawford, J. A,; Fslk~vairant,P.;~ o u d ,
M. L.; Gow, J. D.:Rmenfeld. A. H.: Solmitz, F.; Stevenson. M. L.: Ticho. H. K.: Tripp,R.D.Phys.Reu. LYS7.105, 1127-1128. 6. Rafelski, Johann: Jon-, Steven E. Sci. Am. 1987,237 Ill. 84-89. 7. Breunlich. W. H.;Kammel, P.; Cohen,J.S.: Leon. M.Ann.Reu.Nuc1. Port. Sci. 1989.
39.311-356.
8, P e a t F. David. Cold Fusion: The Making o/a Scientific Conlrooersy: Contemporary:
Conclusion
The two separate routes purported m have caused electrolyticcold fusion haveaerved to confuse the usage of the term
Neact Annual Summer Conference Thr Yew England .4smciatmn of Chemistry Tt.achers announces its Fifty-Thrd Annual Summer (hferencr on Aukwst 12-16th at Rivier College, Nnihua. New Hompshwe. Thc t h r m e fir this year's conference li Nuclcar Terhnulu&?,les.Theme sprakrr will he C.H Arwmd oI'.Mrrwr College. Among the topics to bc discuastd arc radiation, nuclear instrumention,nuclear energy,nuclear biochemistry and medicine, and waste disposal.This is the year to upgrade your understandine and utilization of nuclear science and technolaw. .,. A series of lectures bv outstandine sneakers., tours of nuclear faril:t~es,workshops,andexhih,tsare beingplanned. Field tripssnd tours will maken pwsmlr for panupants to cnpy the man" nlTenngs ofrhr Nashua and Yew Hampshire area. Robrn Litman. Chemlitry and their fam~l~es Suprrwsor at thr Srabruuk Nurlpar Power I'lnnt, 1%chairing promam of spcnkrrs. Registrations are beinl: handled .the . by James Harris, 50 Dover Street, Keene, NH 03431.
".
Volume 68
Number 4
~~~~~
April 1991
279
