The researchers' contraption-- cobbled together from a scavenged dental x-ray machine and an audio amplifier-- bombarded the sample with radiation for several days as monitoring equipment quietly collected data. When the experiment ended and the measurements were scrutinized, the project leader Dr. Carl B. Collins declared unambiguous success. If his conclusions are accurate, Collins and his colleagues may have found the key to developing fist-sized bombs which can deliver destruction equivalent to a dozen tons of conventional explosives. Despite considerable skepticism from the scientific community, the US Department of Defense has since spent millions of dollars probing the physicist's findings.
Hafnium-178-m2 is a nuclear isomer-- an atomic state where the particles of the nucleus are "excited" by higher than normal amounts of energy. Most such isomers are unstable and extremely short-lived, instantly ejecting their excess energy as gamma radiation in order to return to the ground state. But a handful of varieties such as hafnium-178-m2 have a constitution which prevents this release from occurring immediately, which places them in the category of nearly-stable.
This interesting property causes nearly-stable isomers to act as "energy sponges", allowing them to absorb a massive amount of energy which bleeds out very slowly. Hafnium-178-m2 has a half-life of thirty-one years, meaning that it takes a little over three decades for half of the isomer's stored energy to be emitted as gamma rays. Hafnium is also notable for having the highest excitation energy among the nearly-stable isomers; half a teaspoon of pure Hf-178-m2 contains about the same amount of potential energy as one ton of TNT.
The purpose of Dr. Collins' experiment was to explore the possibility of wringing all of the energy from these isomers on demand. He theorized that properly applied x-rays might prompt the nuclei to dump all of their energy at in a short amount of time, a process referred to as induced gamma emission (IGE). To test this theory a few of Collins' enterprising students procured a second-hand dental x-ray machine, married it to a commercial-grade stereo amplifier, and trained the radiation-emitting apparatus upon a precious smudge of hafnium-178-m2 for several weeks.
According to the paper Collins published in the scientific journal Physical Review Letters, his experiment successfully "triggered" the hafnium isomers into an enhanced decay rate. His sensitive instrumentation had apparently registered a small yet unmistakable increase in gamma ray levels during the test. The implications were clear: if one can accelerate the energy release rate of an isomer to a small degree, it follows that there is probably some set of conditions where the atoms can be coaxed to belch all of their energy very rapidly.
Dr. Collins' credibility was soon battered by a storm of skepticism and ridicule. Many scientists were uncomfortable with his outlandish claims and his experiment's large margin for error. Indeed, his findings were somewhat at odds with the laws of physics given that nuclei are thought to be practically unaffected by electromagnetic radiation. However a small minority of researchers were moved to curiosity by the unorthodox idea, prompting a series of independent efforts to reproduce the findings.
The concept also piqued the Pentagon's interest. Since an isomer bomb would represent a new class of non-fission weapons, it would neatly circumvent the limitations of the Nuclear Non-Proliferation Treaty of 1968. Furthermore, a working hafnium device would tend to deluge its target area with absurd amounts of penetrating gamma radiation during the explosion, liquefying the flesh of any persons nearby-- even those protected by bunkers. But the most appealing aspect of isomer triggering was its potential to shoehorn yet more death and destruction into convenient "fun size" packages.
Sometime in the late 1990s a rash of "I believe in isomers" buttons began to appear on defense department lapels. Peter Zimmerman-- the chief scientist of the US Arms Control and Disarmament Agency at the time-- had been exposed to absurd notions of isomer triggering while earning his PhD in nuclear physics, so he was reluctant to dignify the farfetched idea with funding. But it was his responsibility to ensure that the US stayed abreast of emerging technologies. To address his dilemma, Zimmerman opted to consult "the Jasons." Named for the mythical hero of ancient Greek fame, the Jason Defense Advisory Group was established in 1960 to advise the government in matters of scientific controversy. The panel consists of physicists, biologists, chemists, oceanographers, mathematicians, and computer scientists who are hand-picked by existing members from among the nation's best and brightest.
After a very brief investigation, Jason's assessment of the isomer triggering efforts was far from favorable. The circumspect group of elite scientists concluded that the x-ray experiment had not successfully demonstrated an enhanced decay rate. In addition, the Jasons determined that a successful triggering event would not start the necessary chain reaction due to energy dissipation. Isomer enthusiasm was further diluted by the observation that such weapons would require bulky shielding to protect handlers from the be extreme radioactivity of hafnium.
In spite of the Jason findings and the Argonne results, the Defense Advanced Research Projects Agency (DARPA) poured millions of dollars into various hafnium experiments amidst rumors that foreign governments were conducting their own isomer weapon research. The Pentagon's Military Control Technology List even described hafnium-178-m2 as having the potential to "revolutionize all aspects of warfare." But their Stimulated Isomer Energy Release experiments found that even under the best of circumstances, the coveted isomers would cost approximately $1 million per gram assuming a minimum $30 billion investment in production facilities. The investigations also underscored the fact that radioactive hafnium would not be totally consumed even by a successful triggering-- so any such bomb would produce a profoundly "dirty" detonation by scattering radioactive material over the blast area.
Even with all of the setbacks, the prospect of using induced gamma emission as a weapon has not fizzled altogether. A few subsequent experiments have indicated that hafnium triggering may actually be possible. An x-ray test at Louisiana State University appeared to corroborate Collins' results, and an independent team at DARPA called TRiggering Isomer Proof (TRIP) reported their experiment as "successful." Some non-bomb weapons concepts are also under investigation, including a device which could funnel the deadly gamma radiation into a coherent death ray: a gamma-ray laser. Nonetheless, DARPA cut much of its future funding for hafnium-baked weapons research in 2004 due to lack of confidence in the technology.
Back in Dr. Collins' science barn at the University of Texas, the original styrofoam test platform/coffee cup is preserved for posterity in a glass case, labeled "Dr. C's memorial target holder." Dr. Collins remains optimistic about the future of isomer triggering, though his theories are not limited to devices of destruction. He has suggested that pre-measured doses of hafnium isomers might one day provide gamma radiation for the treatment of cancer tumors.
Whether or not x-ray triggering of hafnium-178-m2 is feasible, experiments with the energy-soaking isomer may yet turn up some interesting applications. As James Carroll-- one of Dr. Collins' former students and a contractor with DARPA-- pointed out, "Maybe you can never make anything practical out of it [...] but in the meantime, we will learn a lot about how the nucleus responds to people banging on it."