If not cold fusion, try fracto-fusion?

If not cold fusion, try fracto-fusion?

Whatever its finale, the cold fusion story that began last March will color the history of science. Most of the drama has subsided, but a few researchers have carried on the investigations, continuing to observe phenomena they cannot explain (SN: 12/23&30/89, p.406). Several of these scientists are now exploring a theoretical concept dubbed fracto-fusion to explain at least some of the mystery observations.

Fracto-fusion describes what might happen when microcracks develop in metals containing deuterium or tritium. In this scenario, electrical charges along the cracks speed up deuterium nuclei within the voids, increasing the chances of the nuclei fusing together.

The latest indication that fracto-fusion may occur in some deuterium-loaded solids comes from scientists at Washington State University in Pullman and the Los Alamos (N.M.) National Laboratory. "We suggest that crack growth results in charge separation on the newly formed crack surfaces, which act like a minitature 'linear accelerator,'" the team writes in the January JOURNAL OF MATERIALS RESEARCH.

Although the researchers report no direct evidence of fusion in their samples, University of Washington physicist J. Thomas Dickinson says the experiments show unambiguously that a crucial condition for fracto-fusion -- charge separation across microcracks in a solid -- does occur. In addition, he notes, calculations reported by Japanese researchers suggest that a growing crack, even in an electrically conductive material, can outpace separated charges attempting to neutralize each other by speeding around the increasing perlimeter of a crack.

In principle, the oppositely charged sides of a microcrack could create a strong eleectric field that would greatly accelerate positively charged particles, such as deuterium nuclei, in the gap. This would increase the probability of deuterium-deuterium fusion reactions, Dickinson's group suggests.

As early as 1986, Soviet scientists reported observing neutron emission when they violently crushed lithium deuteride in the presence of an ice made of heavy (deuterium-containing) water. In a letter published in the Nov. 16 NATURE, they describe more recent experiments involving titanium chips and several deuterium-containing materials, including frozen heavy water and lithium deuteride. While vigorously milling the titanium and the deuterium sources, and for a few minutes after milling had ceased, the Soviet researchers detected neutrons emerging at up to seven times the levels measured for titanium chips or deuterium sources milled separately. They suggest that fracturing may play a role.

Dickinson's group placed successive slabs of hydrogen-loaded titanium, deuterium-loaded titanium and unloaded titanium in an apparatus that bends materials until they crack and finally break. During and shortly after fracture, the researchers recorded each specimen's emissions of positively charged particles and photons of various wavelengths. Though they had expected the two gasloaded materials to yield similar results, they found that the deuterium-loaded specimens produced far stronger signals. "The differences in the fracto-emission between these two types of specimens were astounding," they report.

The identities and energies of the emitted particles and radiation remain unknown, and Dickinson wants to conduct follow-up experiments to answer those questions. He notes, however, that funding for cold fusion research has become scarce, especially since last November, when the Energy Department issued a report essentially writing off cold fusion claims as unfounded (SN: 7/28/89, p.78).

Like many physical scientists, Harold Furth, head of the Plasma Physics Laboratory at Princeton (N.J.) University, trains a critical eye on any proposed mechanism for cold fusion. Although Furth himself casually mentioned the possibility of fracto-fusion last May at a meeting of the American Physical Society, he says he now suspects the entire cold fusion drama sprang from misinterpretations of data and experimental errors. "I wouldn't rule out that this [fracto-fusion] is zilch," he told SCIENCE NEWS.

In the midst of such skepticism, physicist Steven E. Jones of Brigham Young University in Provo, Utah, maintains that "fracto-fusion probably is the leading model right now." Jones headed one of the two independent research teams that initially announced the possibility of achieving cold fusion by using electrochemical processes to jam deuterium into metal rods (SN: 4/8/89, p.212). Although he admits that the evidence for fracto-fusion remains inconclusive, he and collaborators at Los Alamos are assembling a sophisticated appratus that may help settle the issue. By injecting tritium into gas-loaded titanium samples and using hydraulic presses to squeeze and fracture the specimens, the team hopes to increase the probability of fusion by several orders of magnitude, Jones told SCIENCE NEWS. If any fusion-produced neutrons do emerge, the apparatus should allow researchers to detect them and measure their energy, he says.