NationMaster - Encyclopedia: Bubble fusion

Bubble fusion or sonofusion is the common name for a nuclear fusion reaction hypothesized to occur during sonoluminescence, an extreme form of acoustic cavitation; officially, this reaction is termed acoustic inertial confinement fusion (AICF) since the inertia of the collapsing bubble wall confines the energy causing a rise in temperature. The high temperatures produceable through sonoluminescence raises the possibility that it might be a means to achieve thermonuclear fusion. The deuterium-tritium (D-T) fusion reaction is considered the most promising for producing fusion power. ... Image of multi-bubble sonoluminescence created by a high intensity ultrasonic horn immersed in a beaker of liquid. ... Inertial confinement fusion using lasers rapidly progressed in the late 1970s and early 1980s from being able to deliver only a few joules of laser energy to a fusion target to being able to deliver tens of kilojoules to a target. ... The principle of inertia is one of the fundamental laws of classical physics used to describe the normal motion of matter, and how it is affected by applied forces. ...

Original experiments

Rusi P. Taleyarkhan (ORNL) and colleagues reported in the March 8, 2002, issue of the peer-reviewed journal Science, that acoustic cavitation experiments conducted with deuterated acetone show measurements of tritium and neutron output that are consistent with fusion; in addition the neutron emission was claimed to be coincident with the sonoluminescence pulse. Shock wave simulations seem to indicate that the temperatures inside the collapsing bubbles may reach up to 10 megakelvins – as hot as the center of the sun. None of the above measurements have been confirmed by a group outside of Taleyarkhan's and are highly debated, recalling the 1989 cold fusion fiasco. Although the apparatus operates in a room temperature environment, this is not strictly cold fusion, as the claimed nuclear reactions would be occurring at the very high temperatures in the core of the imploding bubbles. Oak Ridge National Laboratory (ORNL) is a multiprogram science and technology national laboratory managed for the United States Department of Energy by UT-Battelle, LLC. ORNL is located in Oak Ridge, Tennessee, near Knoxville. ... March 8 poster from Portugal March 8 is the 67th day of the year in the Gregorian Calendar (68th in Leap years). ... 2002 (MMII) was a common year starting on Tuesday of the Gregorian calendar. ... A science magazine is a periodical publication with news, opinions and reports about science for a non-expert audience. ... Deuterium, also called heavy hydrogen, is a stable isotope of hydrogen with a natural abundance of one atom in 6500 of hydrogen. ... R-phrases , , , S-phrases , , , Flash point -20 Â°C Autoignition temperature 465 Â°C RTECS number AL31500000 Supplementary data page Structure & properties n, Îµr, etc. ... Tritium (symbol T or 3H) is a radioactive isotope of hydrogen. ... Properties In physics, the neutron is a subatomic particle with no net electric charge and a mass of 939. ... The kelvin (symbol: K) is the SI unit of temperature, and is one of the seven SI base units. ... Charles Bennett examines three cold fusion test cells at the Oak Ridge National Laboratory, USA // Cold fusion is the name for a claimed nuclear fusion reaction occurring well below the temperature required for thermonuclear reactions (millions of degrees Celsius) in a relatively small table top apparatus. ...

The researchers used a pulse of neutrons in order to nucleate (i.e., "seed") the tiny bubbles, whereas most previous experiments start with small air bubbles already in the water. Using this new method, the team was able to produce stable bubbles that could expand to nearly a millimeter in radius before collapsing. In this way, the researchers stated, they were able to create the conditions necessary to produce very high pressures and temperatures.

Taleyarkhan et al. also prepared identical experiments in non-deuterated (normal) acetone and failed to observe neutron emission or tritium production. Taleyarkhan got the idea of bubble fusion from his friend Dr. Mark Embrechts after a friendly post-dinner chat in 1995.

Oak Ridge replication

These experiments were repeated at Oak Ridge National Laboratory by D. Shapira and M. J. Saltmarsh with more sophisticated neutron detection equipment and they reported that the neutron release was consistent with random coincidence. A rebuttal by Taleyarkhan and the other authors of the original report claimed that the Shapira and Saltmarsh report failed to account for significant differences in experimental setup, including over an inch of shielding between the neutron detector and the sonoluminescing acetone. Taleyarkhan et al. report that when these differences are properly accounted for, the Shapira and Saltmarsh results are consistent with fusion. Oak Ridge National Laboratory (ORNL) is a multiprogram science and technology national laboratory managed for the United States Department of Energy by UT-Battelle, LLC. ORNL is located in Oak Ridge, Tennessee, near Knoxville. ...

In addition, Galonsky has shown that by Taleyarkhan's own detector calibration the observed neutrons are too high in energy to be from a d-d fusion reaction. In a rebuttal comment, Taleyarkhan says the energy is "reasonably close" to that which is expected.

In February 2005, the BBC commissioned a collaboration between Seth Putterman and Ken Suslick (two leading sonoluminescence researchers) to reproduce Taleyarkhan's work. Using similar acoustic parameters, deuterated acetone, similar bubble nucleation, and a much more sophisticated neutron detection device, the researchers could find no evidence of a fusion reaction. This work was reviewed by a team of four scientists, including an expert in sonoluminescence and an expert in neutron detection, who also concluded that no evidence of fusion could be observed.

Claims of replication in 2004, 2005

In 2004, new claims of bubble fusion were made by the Taleyarkhan group, claiming that the results of previous experiments have been replicated under more stringent experimental conditions. [1] These results differed from the original results in that fusion was occurring for a much longer time frame than previously reported; the original report only showed neutron emission from the initial bubble collapse after the bubble nucleation whereas this report shows neutron emission many acoustic cycles later. The data however was lacking in that too large of a window was used for determination of a coincidence between the neutron emission and sonoluminescence light emission. Also, the energy of the detected neutrons were not consistent with neutrons produced from a fusion reaction. 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ...

In July 2005, two of Taleyarkhan's students at Purdue published evidence confirming the previous result.[2] They used the same acoustic chamber, the same deuterated acetone fluid and a similar bubble nucleation system. In this report, no neutron-sonoluminecence coincidence was attempted; also the neutron energy was again not consistent with a neutron produced from a d-d fusion reaction. 2005 (MMV) was a common year starting on Saturday of the Gregorian calendar. ... See also Purdue University System. ...

A recent report soon to be published in the journal Physical Review Letters claims further evidence of fusion.[3] In this inital news report, however, it shows that the reaction does not always work correctly and it is unknown what parameters change to cause the reaction to function properly vs not function at all.

Methods of increasing fusion output

While many of the claims remain unverified at this time, many ideas exist to increase the rate of fusion. The experimental apparatus as conducted in experiments thus far produces energy about seven orders of magnitude lower than that which went into it. However, a number of factors suggest that this is unlikely to remain the case.

Acetone under the temperatures, pressures, and other initial conditions involved is unlikely an optimal solution; several orders of magnitude of efficiency improvement are likely by experimenting with different solutions and laboratory settings. Additionally, using a mix of deuterium and tritium will increase fusion yields by three orders of magnitude (as would simply running the apparatus for long enough, as D-D fusion breeds tritium).

An increase in reaction rate may scale up faster than linearly. As a bubble collapses, shocks bounce inward from the edges, encountering their own reflections and additively combining creating the great heat and pressure to the degree that sonoluminesence or sonofusion can occur. The neutrons from the fusion reaction seed new bubbles nearby, creating a bubble cluster containing over 1,000 cavitating centers which act more powerfully together than they would individually.

One of the most interesting propositions, however, is the potential for a new kind of fusion criticality in sonofusion. Given two acoustic anti-nodes (wherein one is at minimum stress while the other is at maximum stress), neutrons from one node will be released while the other is at maximum stress. Some neutrons will interact with their anti-node, creating a bubble cluster and amplifying the reaction. When it collapses in turn, some of its neutrons will do the same to the original node, leading to a self-sustained nuclear reaction. This possibility is yet to be validated, and still remains theoretical.

Sonofusion has some fundamental benefits compared to most other methods of fusion. Shock heating of the fuel leaves the electrons at almost the same velocity as the ions, and thus (due to their much lighter mass) at insignificant temperatures. As energetic electrons are one of the principal energy loss mechanisms in most fusion aparatuses (Bremsstrahlung radiation, recombination losses, line losses, etc), the sonofusion reaction doesn't lose energy as quickly as in such systems. Instead, it behaves largely as if only ions were being dealt with. At the same time, however, it has some fundamental limitations. The amount of dense, energetic area involved in sonofusion is typically tiny, limiting the amount of fusion reactions that can occur (currently about ten per bubble collapse). Bremsstrahlung listen?, German for braking radiation, is electromagnetic radiation produced by the acceleration of a charged particle, such as an electron, when deflected by another charged particle, such as an atomic nucleus. ...

References

2006 (MMVI in Roman) is a common year starting on Sunday of the Gregorian calendar. ... Fusion typically refers to the merging of two or more entities into a single one: In physics and technology nuclear fusion is the combination of two atomic nuclei into a single nucleus, usually the isotopes of hydrogen, Deuterium and Tritium. ... Properties In physics, the neutron is a subatomic particle with no net electric charge and a mass of 939. ... September 19 is the 262nd day of the year (263rd in leap years). ... 2005 (MMV) was a common year starting on Saturday of the Gregorian calendar. ... January 27 is the 27th day of the year in the Gregorian calendar. ... 2006 (MMVI in Roman) is a common year starting on Sunday of the Gregorian calendar. ... Heavy water is dideuterium oxide, or D2O or 2H2O. It is chemically the same as normal water, H2O, but the hydrogen atoms are of the heavy isotope deuterium, in which the nucleus contains a neutron in addition to the proton found in the nucleus of any hydrogen atom. ... March 1 is the 60th day of the year in the Gregorian calendar (61st in leap years). ... 2002 (MMII) was a common year starting on Tuesday of the Gregorian calendar. ... March 2 is the 61st day of the year in the Gregorian Calendar (62nd in leap years). ... 2002 (MMII) was a common year starting on Tuesday of the Gregorian calendar. ... March 22 is the 81st day of the year in the Gregorian Calendar (82nd in Leap years). ... 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ...

Contents

Original experiments

Oak Ridge replication

Claims of replication in 2004, 2005

Methods of increasing fusion output

References

See also

External links

Contents

Original experiments GA_googleFillSlot("encyclopedia_square");

Oak Ridge replication

Claims of replication in 2004, 2005

Methods of increasing fusion output

References

See also

External links

Original experiments