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Hafnium controversy

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The nuclear isomer 178m2Hf is a particularly attractive candidate for induced gamma emission experiments, because of its high density of stored energy, 2.5 MeV per nucleus, and long 31-year half life for storing that energy. If radiation from some agent could "trigger" a release of that stored energy, the resulting cascade of gamma photons would have the best chance of finding a pair of excited states with the inverted lifetimes needed for stimulated emission. While induced emission adds only power to a radiation field, stimulated emission adds coherence and the possibility to manipulate gamma ray coherence, even to a small degree would be interesting.[1] The lifetime of the hafnium isomer is long enough for tractable amounts of material to be collected into experimental targets. Such samples would hold no hazards for personnel working with the material; 1 microgram of 178m2Hf has an activity of only 40 microcuries (1.5 MBq).

A proposal to test the efficacy for "triggering" 178m2Hf was approved by a NATO-Advanced Research Workshop(NATO-ARW) held in Predeal in 1995[2]. Although the proposal was to use incident protons to bombard the target, α-particles were available when the first experiment was scheduled. It was done by a French, Russian, Romanian and American team that was largely unsupported financially. Results were said to be extraordinary, but clearances from controlling agencies were not obtained. The results were not published. Only fragments of the data can be found at the present time (some at the above URL). The one-of-a-kind 178m2Hf target concentrated to 4% isomer content was also lost. Nevertheless, 178m2Hf was implied to be of special importance to potential applications of IGE. It was almost the optimal situation to excite a major controversy; and such a controversy quickly erupted.

Importance

  • 178m2Hf has the highest excitation energy of any comparably long-lived isomer. One gram of pure Hf-178-m2 would contain approximately 1300 megajoules of energy, the equivalent of exploding about 226 kilograms (500 pounds) of TNT. The half-life of Hf-178-m2 is 31 years or 1 Gs (gigasecond, 1,000,000,000 seconds) so that a gram's natural radioactivity is 1.6 TBq (terabecquerels) or roughly 40 Ci (curies), the activity of 1 gram of radium. The activity is in a cascade of penetrating gamma rays, the most energetic of which is 0.574 MeV. Substantial shielding is needed before it is safe for people to be around.
  • All of the energy released would be in the form of photons of X-rays and gamma rays.
  • Discussions also indicate that the energy might be released very quickly, so that Hf-178-m2 could produce extremely high powers (on the order of exawatts).
  • The characteristic scales of times for processes involved in applications would be favorable for consuming all of the initial radioactivity. The process for triggering a sample by IGE would use photons to trigger and produce photons as a product. The propagation of photons occurs at the speed of light while mechanical disassembly of the target would proceed with a velocity comparable to that of sound. Untriggered 178m2Hf material might not be able to get away from a triggered event if the photons didn't interact first with the electrons.
  • Both the proposal to the NATO-ARW and the fragmentary results from the subsequent experiment indicated that the energy of the photon needed to initiate IGE from 178m2Hf would be less than 300 keV. Many economical sources of such low energy X-rays were available for delivering quite large fluxes to target samples of modest dimensions.
  • Samples of 178m2Hf were and remain available at low concentrations <0.1%.

Chronology of notable events

  • Around 1997 the JASONS advisory group took testimony about the triggering of nuclear isomers. The JASON Defense Advisory Group put out a relevant public report[3] saying that they concluded that such a thing would be impossible and should not even be tried. Despite intervening publications in peer-reviewed journals of articles written by an international team reporting IGE from 178m2Hf, around 2003 IDA took testimony, again from relevant scientists on matters of the credibility of reported results. The Institute for Defense Analysis issued an (IDA) highly critical report[citation needed] proposing that the positive experiments were so flawed that they should never have been published. Significant in both collections of testimony is that the lead US member of the team, Prof. Carl Collins, that was publishing the successes, never testified. In both "Reviews" the processes of testimony were classified. Owing to a personal quirk[4] Prof. Collins refuses to accept a security clearance and so was forbidden to testify, as were overseas collaborators in the experiments described in peer-reviewed publications as successful. Instead, interpretative testimony was provided by J.J. Carroll without consultation with the authors of the articles reporting successes with Hafnium IGE.
File:SP8 BL01B1.jpg
Experiment producing IGE from a sample of the nuclear isomer 178m2Hf. (left to right) Students on duty; (w/ladder) the world's most stable beamline for monochromatic X-rays, BL01B1; (rt.) main ring of the SPring-8 synchrotron at Hyogo.
  • Around 2003, DARPA initiated exploratory research termed stimulated isomer energy release (SIER) and public interest was aroused, at both popular levels[5] and at professional levels[6].
  • The first focus of SIER was whether significant amounts of 178m2Hf could be produced at acceptable costs for possible applications. A closed panel called HIPP was charged with the task and the conclusion was yes, it could. However, a scientist on that confidential DARPA HIPP review panel in 2003 "leaked" prejudicial but preliminary concerns to the press.[7]. This unsubstianted assertion set into motion the subsequent cascade of inaccurate reports about the so-called "outrageous costs" of isomer triggering.
  • Having satisfied the charge to the HIPP panel to explore the problem of production at acceptable cost, the SIER program turned to the matter of definitive confirmation of the reports of IGE from 178m2Hf. A task of TRiggering Isomer Proof (TRIP) was mandated by DARPA and assigned to a completely independent team from those reporting success previously. The "gold standard" of Hafnium-isomer triggering was set as the Rusu dissertation[8]. The TRIP experiment required independent confirmation of the Rusu Dissertation. It was successful, but could not be published.
  • The negative perception of the "earmarking" of Congressional appropriations for "pet projects" is well-known. The reverse process of "inverse earmarking" is less well-known. It is used effectively to stop projects opposed by "pet interests". Forward progress toward the resolution of the scientific conflict within the US over IGE from 178m2Hf by normal scientific discourse was stopped in 2005 by such inverse earmarking[9].
  • By 2006 there were 11 significant publications in peer-reviewed journals supporting the observation of IGE from 178m2Hf. Full-text versions of the oldest 10 can be read here[10]. Reprints of the most recent must be ordered from the publisher[11]. Reprints (available at the link) of articles that were published after 2001 describe work conducted with tunable monochromatic X-ray beams from the synchrotron light sources SPring-8 in Hyogo and SLS in Villigen.
  • By 2006 there were 2 articles[12][13] that claimed to disprove possibilities for IGE from 178m2Hf and three theoretical articles written by the same individual saying why it should not be possible to occur by the particular steps the author envisioned[14][15][16]. The first two described synchrotron experiments in which the X-rays were not monochromatic.
  • In 2007 Pereira et al [17] calculated a production cost of $1/J.
  • February 29, 2008 DARPA distributed some of the 150 copies of the final report of the TRIP experiment that had independently confirmed the "gold standard" of Hafnium-isomer triggering. Sustained by peer review, the 94 page report is distributed for official use only (FOUO) by the DARPA Technical Information Office, 3701 N. Fairfax Dr., Arlington, VA 22203 USA.
  • In 2009 S.A. Karamian et.al. published the results of a four nation team's experimental measurements at Dubna for the production of quantities of 178m2Hf by spallation at energies as low as 80 MeV.[18] Besides significantly lowering the projected cost of production, this experimental result proved the accessibility to sources of 178m2Hf to be within the capabilities of the several idle cyclotron devices scattered around the world.

Opinions

  • It has been claimed that there is much greater statistical confidence[19] in the results proving IGE from 178m2Hf than confidence in the experiments disproving it.

See also

References

  1. ^ http://findarticles.com/p/articles/mi_m1200/is_v130/ai_4539152/ Link to 1986 article discussing dream of a gamma-ray laser.
  2. ^ Proceedings of the NATO-ARW are collected in Hyperfine Interactions, 107, pp 3-492 (1997).
  3. ^ N. Lewis, R. Garwin, D. Hammer, W. Happer, R. Jeanloz. J. Katz, S. Koonin, P. Weinberger, E. Williams (October 1997). High Energy Density Explosives (PDF). JSR-97-110.{{cite book}}: CS1 maint: multiple names: authors list (link) Sect. 4, p. 13.
  4. ^ Prof. Collins refuses to accept a security clearance.
  5. ^ S. Weinberger (28 March 2004). "Scary things come in small packages". Sunday Supplement Magazine. Washington Post. Retrieved 2009-05-03.
  6. ^ Bertram Schwarzschild (May 2004). "Conflicting Results on a Long-Lived Nuclear Isomer of Hafnium Have Wider Implications". Physics Today: 21.
  7. ^ San Jose newspaper article., October, 2003.
  8. ^ C. Rusu (PhD Dissertation, U of Texas at Dallas, 2002)Available from: Proquest (Order Number: 3087127).
  9. ^ Richard M. Jones (2004-06-04). "Armed Services Committees Refuse to Authorize SIER Weapon Research". American Institute of Physics.
  10. ^ Reprints of articles about nuclear isomers in peer reviewed journals. - The Center for Quantum Electronics, The University of Texas at Dallas.
  11. ^ C.B. Collins, N.C. Zoita, F. Davanloo, Y. Yoda, T. Uruga, J.M.Pouvesle, and I.I. Popescu (2005). "Nuclear resonance spectroscopy of the 31-yr isomer of Hf-178". Laser Physics Letters. 2 (3): 162. doi:10.1002/lapl.200410154.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  12. ^ Ahmad, I.; et al. (2001). "Search for X-Ray Induced Acceleration of the Decay of the 31-Yr Isomer of 178Hf Using Synchrotron Radiation". Physical Review Letters. 87 (7): 072503. doi:10.1103/PhysRevLett.87.072503. PMID 11497887. {{cite journal}}: Explicit use of et al. in: |author= (help)
  13. ^ Ahmad, I.; et al. (2003). "Search for x-ray induced decay of the 31-yr isomer of 178Hf at low x-ray energies". Physical Review C. 67 (4): 041305R. doi:10.1103/PhysRevC.67.041305. {{cite journal}}: Explicit use of et al. in: |author= (help)
  14. ^ Tkalya, Eugene V. (2003). "Probability of L-shell nuclear excitation by electronic transitions in 178Hfm2". Phys Rev C. 68 (6): 064611. doi:10.1103/PhysRevC.68.064611.
  15. ^ Tkalya, Eugene V. (2005). "Induced decay of 178Hfm2: Theoretical analysis of experimental results". Phys Rev C. 71 (2): 024606. doi:10.1103/PhysRevC.71.024606.
  16. ^ Tkalya, Evgenii V (2005). "Induced decay of the nuclear isomer 178m2Hf and the 'isomeric bomb'". Physics-Uspekhi. 48 (5): 525. doi:10.1070/PU2005v048n05ABEH002190. [Uspekhi Fiz. Nauk 175, 555 (2005)].
  17. ^ Pereira; et al. (2007). Laser Physics. 17: 874. {{cite journal}}: Explicit use of et al. in: |author= (help); Missing or empty |title= (help)
  18. ^ Karamian, S. E.; et al. (2009). "Spallation and fission products in the (p+179Hf) and (p+natHf) reactions". Nuclear Instruments and Methods in Physics Research A. 600: 488–497. doi:10.1016/j.nima.2008.12.001. {{cite journal}}: Explicit use of et al. in: |author= (help)
  19. ^ Open letter on triggering confidence.
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