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N°32 I quarterly I january 2014 Live from the Labs | 11 w Energy By using a beam of protons accelerated by ultra-intense laser pulses, CNRS researchers increase the yield of proton-boron fusion reaction a hundredfold. Improving Neutron-Free Fusion delivered, which in the initial study was about ten times that emitted by a cell phone held against the ear. In the longer term, the researchers hope to gain a clearer understanding of the molecular and cellular mechanisms involved in radio wave-brain interactions. 01. D. Moretti et al., “In-vitro exposure of neuronal networks to the GSM -1800 signal,” Bioelectromagnetics, 2013. 34: 571-8. 02. L aboratoire de l’intégration du matériau au système (CNRS / Université Bordeaux-I / Institut Polytechnique), Institut des maladies neurodégénératives (CNRS / Université Bordeaux-II), and Institut de recherche XLIM (CNRS / Universités de Limoges and Poitiers), in partnership with Bouygues Telecom. Contact information: IMS Laboratory, Bordeaux. Noëlle Lewis > noelle.lewis@ims-bordeaux.fr Bernard Veyret > bernard.veyret@ims-bordeaux.fr creating a proton beam from the hydrogenated foil surface. By tuning the experimental parameters, the proton energy could be adjusted to better match the low-energy resonances of the cross section of the pB reaction, thereby increasing the reaction yield. Much work is left to optimize this approach and Labaune is confident that the yield can be significantly improved. Considering the advantages of the pB reaction, she has already shown that the proposed scheme deserves further study. 01. Laboratoire pour l’utilisation des lasers intenses (CNRS / CEA / Ecole polytechnique / UPMC). 02. C. Labaune et al., “Fusion reactions initiated by laser-accelerated particle beams in a laser-produced plasma,” Nat. Commun., 2013. 4:2506. doi: 10.1038/ ncomms3506. by Brett Kraabel Nuclear fusion has powered stars for eons, and mankind now hopes to harness its promise of abundant clean energy. Recently, CNRS researcher Christine Labaune and colleagues at LULI1 and the University of Arizona (US) took an important step toward this goal by using two pulsed lasers to generate a hundredfold increase in the yield of helium nuclei (“alpha particles”) from the fusion of boron and hydrogen nuclei (protons).2 For years, science has pinned its hopes of fusion energy on the deuteriumtritium (D-T) reaction, essentially because igniting it requires an equilibrium temperature of “only” 25 million degrees Celsius. However, tritium is not a natural element and must therefore be continually produced. Moreover, the reaction creates high-energy neutrons that are very hard to handle. An alternative is the proton-boron (pB) reaction, for which all elements involved are abundant in nature and the alpha particles created are easy to convert into thermal energy to run a turbine. The problem is that the equilibrium temperature for igniting the pB reaction is ten times higher than for the D-T reaction, and techniques to run the pB reaction without reaching thermal equilibrium have had very low yields. “To increase the yield of the pB reaction, our idea was to produce a beam of protons accelerated by an ultra-intense laser pulse and to use this beam to create pB reactions in a boron target without attaining thermal equilibrium,” explains Labaune. To do this, the team irradiated a solid boron target with a first laser pulse, creating a boron plasma. A second laser pulse irradiated an aluminum foil target, Contact information: LUL I, Palaiseau. Christine Labaune > christine.labaune@polytechnique.fr q Experiment chamber at LUL I, in which aneutronic, proton-bore reactions took place. © j. Barande /ep Palaiseau Bordeaux


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