"Material studied in an aqueous electrolysis cell is indicated by "Electro" and a dry electrolytic cell by "electrodischarge"; gas loading is generally designated by The stated value for neutrons per count, expressed as percent, is listed. The value is only for the neutron detector. Occasionally, several configurations were studied, "The background is given as counts per second only for neutron detection. In some cases, a variety of values were observed depending on the configuration. This value gold-plated bar of titanium.' On the other hand, neither Blagus et al. 201 (Ruder Boskovic Institute, Yugoslavia), using much shorter cycles (2 Hz, 2.2 mHz, and 0.56 mHz), nor Aiello et al. 205 (Universita di Catania, Italy), using loading and unloading in D. gas, produced neutrons. 5. Iyengar et al. 235 (BARC, India) reported a large variety of observations during which neutrons were detected from palladium, Pd-Ag, titanium, and Ni-Ti electrodes using LiOD or NaOD in the electrolyte. Steady production as well as large bursts were measured. Neutron production was correlated with gamma-ray and tritium production. Pulsing the current between 1 and 2 A during part of a cell history seemed to encourage production of nuclear products. 6. Gozzi et al. 219 (University of Rome, Italy) correlated a sudden increase in cathode (sintered palladium powder) temperature (>120°C) with a burst of neutrons (7.2 x 103). In this case, it is not known whether the heat rise caused conditions that produce neutrons or, on the other hand, a nuclear event produced neutrons and caused a temperature rise. 7. Yamaguchi and Nishioka254 (NTT Basic Research Laboratory, Japan) coated a sheet of palladium (1 mm thick) on one side with Mn-O and on the other with gold. After being held for a day in 0.5 atm D2 at room temperature, the sample was placed in vacuum. Within 3 h, an explosive release of deuterium occurred that was associated with a burst of neutrons (1 to 2 x 106 n/s). Sudden heating caused alloying between the gold and palladium. Repeated cycles using the same sample produced similar neutron bursts but after a shorter time in vacuum. Neutron production and heat were not observed while using normal hydrogen. This heat cannot be caused simply by loss of the small amount of contained D2 gas because this reaction is endothermic. 8. Bém et al.330 (Institute of Nuclear Physics, Czechoslovakia) found that a thin layer of titanium (1.4 to 1.7 mg/cm2 on molybdenum) that had been reacted with tritium showed low-level neutron production at 14 MeV when it was used as a cathode in an electrolytic cell. On the other hand, Guilinger et al. 152 [Sandia National Laboratories (SNL)] failed to find evidence of fusion using a thin film of titanium tritide on copper in an electrolytic cell, and Southon et al. (McMaster University, Canada) detected no neutrons after a larger piece of titanium had been heated in T2 gas and electrolyzed. However, there were other major differences between these studies besides the thickness of titanium that could account for the different results. 184 'It is not clear which metal, the palladium or the titanium, caused the neutron burst. 9. Sánchez et al. 256 (Universidad Autonoma Cantoblanco, Spain) electrolyzed titanium in a cell containing Li2SO, in D2O. Bursts of neutrons (up to 4 x 10 times background) were correlated with changes in cell current, gamma-ray detection (2 to 2.3 MeV), and tritium production. The neutron rate dropped in a linear manner after the cell current was turned off. 10. Lipson et al. 278 (Institute of Physical Chemistry, USSR) found that ball milling titanium with D2O or deuterated polypropylene caused neutron emission (0.3 to 0.4 count/s) during the process, for a short time (8 to 10 min) afterward, and when the material was cooled in liquid nitrogen. Repeated cycles caused the effect to disappear. 11. Silvera and Moshary11 (Harvard University) reported an important negative study done at very high pressures (105 kbar) using thin palladium (97 μm thick x 208-μm diameter) in D2 gas. A D/Pd ratio of 1.34 ± 0.1 was claimed. This is much higher than any other reported value. However, the palladium had been pressure bonded to rhenium, an operation that would have severely disrupted the periodic array of atoms within the lattice. Detection sensitivity was not sufficient or stable enough to be able to conclude that energy was being produced although there was a slight indication of excess heat (<2.3 mW). No neutrons were observed above the 1.86 ± 0.3 count/h background, and no effort was made to detect tritium. Fractofusion' is not possible under these conditions, although heat and/or tritium production might have been possible but their production was inconclusive. 12. Shani et al. 272 (Ben Gurion University and Hebrew University, Israel) made studies of gas-loaded palladium and high-pressure D2 that suggest that the emission of 2.5-MeV neutrons is enhanced by an external source of neutrons. 256 or above 5.2 MeV. Correlation between gamma-ray and neutron emission also has been reported by Celani et al. 255 (Frascati Research Centre, Italy) for gammaray energy between 100 and 500 keV, and >800 keV; Jorne264 (University of Rochester) for gamma-ray energies >360 keV; and Sánchez et al. (Universidad Autonoma Cantoblanco, Spain) for energies between 2 and 2.3 MeV. Iyengar et al. 235 (BARC, India) measured correlated neutron and gamma-ray emission (1.186 and >3 MeV) in a variety of cells. Bush et al. 228 (University of Texas and Naval Weapons Center) detected electromagnetic radiation while heat was being produced using X-ray film. 2. Matsumoto 283 (Hokkaido University, Japan) saw tracks in nuclear-sensitive film located on the outside of a cell containing a palladium cathode and an electrolyte of 3% NaCl in D2O. The shape of the tracks was used to argue for a new particle called an "iton." 3. Jones et al. 332 (Brigham Young University) detected charged-particle emission from deuteriumloaded palladium foils that showed clear energy peaks. Because the inferred energy depends on an uncertain knowledge of the type of particle, the absolute energy is unknown. III.E. Nuclear Products from Bombardment or Implantation Nuclear products have been produced by bombarding palladium or titanium with deuterium. Energy has been added to the atoms by using high voltage discharge, ion acceleration, or acceleration of D2O or D2 clusters. These techniques add energy to the deuterium atoms before they contact atoms residing in the metal lattice, resulting in what is called "lukewarm fusion" by some workers. Although some fusion is expected to be produced by such high energies, a large quantity of products, a low n/3H ratio, and sustained emission after bombardment has ceased have been observed and are not expected. On the other hand, some experiments did not produce unexpected results. III.E.1. High-Voltage Discharge Karabut et al. 224 (Scientific Industrial Association, USSR) produced heat and neutrons using discharge in D2 gas with a palladium cathode. The purity of the surface was found to be important. A similar study by Besenbacher et al. 199 (University of Aarhus, Denmark), during which the palladium was covered by 50 Å of copper, failed to produce neutrons. Palladium, after being silver-soldered in air to copper, also failed to produce results in a discharge cell [Ruzic et al. (University of Illinois)]. Prelas et al. (University of Missouri) formed a microwave plasma in D2 (0.5 to 268 288 10 eV) that was caused to impact on palladium metal. Evidence of low-level neutron and gamma-ray emission (2 to 10 times background) was obtained while the plasma was operating. A gamma-ray peak centering on 8.1 MeV was observed during one experiment after a lengthy discharge. Rout et al. 236 (BARC, India) subjected titanium to plasma discharge of D2 in a Mather plasma focus device 333 that produced ion energies in the 10- to 100kev range. This technique produced significant amounts of tritium (up to 392 μCi) and a very low n/3H ratio (<10~$). III.E.2. Ion Bombardment Chambers et al. 285 (Naval Research Laboratory), after several previously reported negative attempts, detected the emission of particles that were consistent with the presence of high-energy tritons (≤5 MeV) after bombarding titanium with 300- to 1000-eV deuterons. The magnitude of the emission and its continuation for up to 6 min after the beam had been turned off are not consistent with expectation. Behrisch et al. 167 (MaxPlanck-Institut für Plasmaphysik, Federal Republic of Germany) found that bombardment of titanium by 4.5keV D failed to produce detected reaction products. 284 Cecil et al. (Colorado School of Mines) bombarded thin films of palladium (1 μm) deposited onto molybdenum (3 μm) using 95-keV D*. Evidence of emitted 3-MeV photons and 1-MeV tritons was obtained during the bombardment. After the bombardment was stopped, when the foil had been sufficiently implanted with deuterium, a current was passed through the foil. Particle emission, assumed to be protons, was detected near 3 and 5 MeV. Later studies 283 using titanium implanted with deuterium followed by several thermal cycles produced large bursts of activity that were inferred to be 10-MeV tritons or 3He. The presence of any emission during such a treatment, but especially its energy, is unexpected. Gu et al. 266 (Mississippi State University) observed neutron production (9 times background) while bombarding palladium with 1-keV D. Neutron production was also observed by Durocher et al. 187 (University of Manitoba, Canada) using 60-keV D*. However, in the latter case, the flux was claimed to be consistent with known fusion theory. Further studies reported by McKee et al.334 (University of Manitoba, Canada) showed neutron emission from palladium and titanium targets when loaded with deuterium using 60-keV D* and 30kev Dr. Myers et al. 166 (SNL) detected nearly equal proton and triton emission while bombarding palladium, zirconium, and titanium with 10-keV D+ but found no emission after the beam was turned off. Dignan et al.178 (San Francisco State University) bombarded a thin film of palladium (≈2000 Å) with 1-keV neutral deuterium and D2 at 77 K and found no evidence of emitted neutrons or 23.8-MeV gamma rays. III.E.3. Cluster Bombardment Beuhler et al.289 (Brookhaven National Laboratory) bombarded TiD, ZrD, and perdeuteriopolyethylene with clusters of D2O containing 20 to 1500 molecules accelerated to 200 to 325 keV. A maximum in the resulting photon count rate occurred when the cluster size was near 200 D2O molecules. The fusion rate was much larger than expected from conventional theory, and larger abundances of 'H and 'H were seen in the spectrum compared to 'He, thereby giving an apparent branching ratio' of <0.88. Such studies fall in the transition region between hot fusion and cold fusion. This work has been discussed in detail by Rabinowitz et al. in a series of papers. 335 Fallavier et al. 290 (Institut de Physique Nucléaire de Lyon, France) used clusters of frozen deuterium ions in the size range between (200 D)* and (300 D)*. Bombardment of TiD and polyethylene targets using an energy of 100 to 150 keV produced no evidence of fusion. IV. DISCUSSION During the last 2 years, all of the observations made by the original discoverers of the cold fusion effect have been confirmed by numerous observations throughout the world. In addition, many new conditions have been discovered that cause the effect to occur. In spite of this effort, many people find a major problem in accepting the cold fusion effect because there is a lack of expected nuclear signatures, the magnitude of the effect is much larger than expected based on current theory, and there is still difficulty in replication. As a result, various arguments are proposed to attribute the heat to chemical processes, the tritium is explained as contamination or experimental error, and the neutrons are assumed to be caused by cosmic rays or instrument error. These explanations had reasonable basis during the early history of the field. Now, the variety of techniques and accuracy of the work make this approach much less tenable. When d-d fusion occurs, the reaction products can be tritons (3H), protons (hydrogen), helium ('He), and neutrons. Based on considerable experience with "hot" fusion, these reaction products should be produced in negligible quantity, or at least in nearly equal amounts, and be accompanied by X radiation. To the extent that neutrons form, gamma radiation (2.22 MeV) should also be seen from n-p interaction with the surrounding water bath. The absence of significant neutrons as well as the absence of any expected nuclear product sufficient to cause the observed heat has added 'This value is an upper limit because of an uncertain baseline for the 'He peak caused by the residual X-ray background. to the skepticism. In addition, the apparent absence of 14-MeV neutrons resulting from t-d (3H-2H) fusion is a concern to some. Because of these apparent conundrums, the field is still handicapped by considerable doubt and limited support in many countries. Neutrons are now known to be produced as bursts (=103 to 10' n/s) as well as at a steady but lower rate (<1 n/s). When measured, the expected energy for d-d fusion of 2.45 MeV is found along with neutrons near 3 and 7 MeV. Neutrons in unexpectedly large quantity have been found to issue from palladium, titanium, or several alloys after being loaded with deuterium by gas reaction, electrolysis, or ion bombardment. Nonequilibrium conditions, such as produced by temperature changes, increase the probability of production although an overt creation of nonequilibrium is not always a requirement. Physical commutation (ball milling) of titanium in a deuterium-containing media and chemical reactions involving deuterium-containing compounds also can result in neutrons. In some cases, neutrons seem to result from fracturing (fractofusion) of the material lattice. Although titanium is known to easily fracture when it hydrides, this effect is less obvious in palladium. Nevertheless, fissures are produced in palladium during electrolysis, 336,337 and each time it is cycled through the a-ẞ transition. 297 289 Values for the n/3H ratio fall, at the present time, between 4 x 10- and 10-9 using electrolytic cold fusion cells. Using conventional techniques, the expected branching ratio for d-d fusion is near unity for impact energies at least as low as 3 keV (Refs. 338, 339, and 340) and for muon fusion at even lower energy. 341,342 Ion impact studies by Beuhler et al. near 100 eV indicate a slightly less than unity branching ratio. A variety of approaches have been used to explain this apparent conflict. Kim" argues that the muon fusion data are not applicable and suggests either that the branching ratio is nonlinear to give smaller n/3H values at lower energy or there is some resonance enhancement for tritium production in the low-energy region. Resonance between deuterium atoms has also been proposed by Zakowicz and Rafelski.“ Mayer and Reitz 100 argue that a variety of resonance reactions are possible between deuterium and various impurity metals, and these reactions can result in preferential tritium production. On the other hand, Chatterjee114 suggests that the branching ratio is very sensitive at low energies to the energy available in the final nuclear products after energy is drained off into the lattice electrons. This idea is extended by Hora et al. using a proposed electron surface layer as the medium for screening and energy extraction. Collins et al.111 suggest that a tunneling process in the lattice leads to an excited state of "He that decays primarily by the production of tritium, a proton, and energetic electrons. Handel also suggests a tunneling process that involves neutron transfer. If a source of virtual neutrons were available in the system or real neutrons were |