Gamma-ray weapons

["Fred Dawson" <fd003f0606@blueyonder.co.uk>]

Report from New Scientist 14 August



Gamma-ray weapons could trigger next arms race







http://www.newscientist.com/news/news.jsp?id=ns99994049







An exotic kind of nuclear explosive being developed by the US Department of

Defense could blur the critical distinction between conventional and nuclear

weapons. The work has also raised fears that weapons based on this

technology could trigger the next arms race.







The explosive works by stimulating the release of energy from the nuclei of

certain elements but does not involve nuclear fission or fusion. The energy,

emitted as gamma radiation, is thousands of times greater than that from

conventional chemical explosives.



The technology has already been included in the Department of Defense's

Militarily Critical Technologies List, which says: "Such extraordinary

energy density has the potential to revolutionise all aspects of warfare."







Scientists have known for many years that the nuclei of some elements, such

as hafnium, can exist in a high-energy state, or nuclear isomer, that slowly

decays to a low-energy state by emitting gamma rays. For example,

hafnium-178m2, the excited, isomeric form of hafnium-178, has a half-life of

31 years.







The possibility that this process could be explosive was discovered when

Carl Collins and colleagues at the University of Texas at Dallas

demonstrated that they could artificially trigger the decay of the hafnium

isomer by bombarding it with low-energy X-rays (New Scientist print edition,

3 July 1999). The experiment released 60 times as much energy as was put in,

and in theory a much greater energy release could be achieved.





Energy pump



Before hafnium can be used as an explosive, energy has to be "pumped" into

its nuclei. Just as the electrons in atoms can be excited when the atom

absorbs a photon, hafnium nuclei can become excited by absorbing high-energy

photons. The nuclei later return to their lowest energy states by emitting a

gamma-ray photon.







Nuclear isomers were originally seen as a means of storing energy, but the

possibility that the decay could be accelerated fired the interest of the

Department of Defense, which is also investigating several other candidate

materials such as thorium and niobium.



For the moment, the production method involves bombarding tantalum with

protons, causing it to decay into hafnium-178m2. This requires a nuclear

reactor or a particle accelerator, and only tiny amounts can be made.







Currently, the Air Force Research Laboratory at Kirtland, New Mexico, which

is studying the phenomenon, gets its hafnium-178m2 from SRS Technologies, a

research and development company in Huntsville, Alabama, which refines the

hafnium from nuclear material left over from other experiments. The company

is under contract to produce experimental sources of hafnium-178m2, but only

in amounts less than one ten-thousandth of a gram.







Extremely powerful



But in future there may be cheaper ways to create the hafnium isomer - by

bombarding ordinary hafnium with high-energy photons, for example. Hill

Roberts, chief scientist at SRS, believes that technology to produce gram

quantities will exist within five years.



The price is likely to be high - similar to enriched uranium, which costs

thousands of dollars per kilogram - but unlike uranium it can be used in any

quantity, as it does not require a critical mass to maintain the nuclear

reaction.







The hafnium explosive could be extremely powerful. One gram of fully charged

hafnium isomer could store more energy than 50 kilograms of TNT. Miniature

missiles could be made with warheads that are far more powerful than

existing conventional weapons, giving massively enhanced firepower to the

armed forces using them.







The effect of a nuclear-isomer explosion would be to release high-energy

gamma rays capable of killing any living thing in the immediate area. It

would cause little fallout compared to a fission explosion, but any

undetonated isomer would be dispersed as small radioactive particles, making

it a somewhat "dirty" bomb. This material could cause long-term health

problems for anybody who breathed it in.





Political fallout



There would also be political fallout. In the 1950s, the US backed away from

developing nuclear mini-weapons such as the "Davy Crockett" nuclear bazooka

that delivered an explosive punch of 18 tonnes of TNT. These weapons blurred

the divide between the explosive power of nuclear and conventional weapons,

and the government feared that military commanders would be more likely to

use nuclear weapons that had a similar effect on the battlefield to

conventional weapons.











AIR FORCE PROPOSAL PREPARATION INSTRUCTIONS







http://www.acq.osd.mil/sadbu/sbir/solicitations/sttr02/pdf/af02.pdf







Extract from the above document page 7







AF02T006 TITLE: Isomeric Targets for High-Energy Density Applications



TECHNOLOGY AREAS: Materials / Processes



OBJECTIVE: Identify sources and production methods for isomeric materials.

Build and characterize high-energy



density targets containing isomeric materials for experiments and potential

applications.







DESCRIPTION: Extremely high energy densities can be found in isomeric

materials in which long-lived excited



nuclear states may store up to 1.2 GigaJoules/gram for up to decades.

Spontaneous decay of these special nuclear states occurs typically by gamma

decay only, leading to no direct residual radioactivity. Some recent

experiments have



suggested that a triggered energy release in the form of gamma rays may be

produced, or driven, by incident x rays of



much lower energy. This process could provide a means of controlling the

energy release as a form of nuclear battery.



More experiments are needed to completely resolve the physical situation for

the first isomeric material of interest,



Hafnium-178m2. New targets must be designed, built and characterized to

support these experiments. In addition, other



isomer materials may be of interest, and the possibility of constructing

experimental targets with those isotopes must be



investigated.







Fred Dawson

New Malden

Surrey. KT3 5BP

England



020 8287 2176





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