More exotic research
Date: Wednesday, September 21, 2005 @ 23:32:10 GMT
Topic: Science

To produce thermonuclear reaction it is necessary, firstly, to have nuclei with a large quantity of neutrons available, for example, deuterium nuclei, and secondly, these nuclei should possess sufficiently high velocity and merge together upon collision, having overcome the Coulomb barrier. It turns out that all these conditions are observed in the course of a stroke of lightning - such a conslusion is evident from calculations by B.M. Kuzhevsky, Ph.D., head of the neutron research laboratory, Skobeltsin Scientific Research Institute of Nuclear Physics (Moscow State University).

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FIRST BEC IN A SOLID. A Bose-Einstein condensate (BEC) has been observed in a solid material for the first time. The BEC in this case is not a collection of atoms but rather a collection of particle-like excitations in the solid called "magnons." In the presence of extremely high magnetic fields, atoms with an intrinsic magnetism of their own (as represented by a spin vector) can be oriented all in one direction if the field strength is larger than a certain value. In this configuration a small input of energy can tilt some of the spins out of the general formation. The successive tilting of spins can take the form of a wave moving through the sample. If also the temperature of the sample is extremely low, then the moving wave can be considered as a particle-like (or quasiparticle) entity, much as mechanical vibrations in a solid can be construed as sound waves or as phonons. A magnon is such a moving magnetic-spin disturbance. What the present experiment observes is a condensation of magnons if the magnetic field is lower than the critical strength and the temperature is below a characteristic value. The work was carried out by a group of scientists from these institutions: Max Planck Institute for Chemical Physics of Solids (MPI, CPfS), Dresden; JINR Lab, Dubna; Oxford University; and Adam Mickiewicz University, Poznan. They used a antiferromagnetic material (in which the spins of neighboring atoms tend to be alternately aligned up and down) with a chemical composition of Cs2CuCl4. The temperatures were in the mK range and the external magnetic field used was at high as 12 T (120,000 gauss).

In an atomic BEC, dilute vapors of atoms (typically a million or so at a time) are chilled until they enter into a single quantum state, as if all the atoms were one atom. In a magnon BEC what is formed is a monolithic static magnetic alignment in the solid. About 10^23 magnons participate in the condensation. A magnon BEC had been predicted several years ago but not realized unambiguously until this work. The evidence for condensation is that the material undergoes a phase transition at a critical temperature dependent on the size of the external field used. What the researchers look for is a significant change in the measured heat capacity (the energy needed to raise the material's temperature by a certain amount). (Radu et al., Physical Review Letters, 16 September 2005; contact Heribert Wilhelm, )

SOLID-STATE SUPERCAPACITORS. A new type of solid state device, prepared by scientists at UCLA, may provide a better method for backing up memory information on a computer in the case of a power failure. A capacitor is an electrical component for storing electrical energy in the form of negative and positively charged opposing electrodes. Its ability to do this is measured in units of farads. So called supercapacitors are perhaps a thousand times better than ordinary capacitors by being much smaller in size and by bringing the two electrodes closer together. As a quick energy storage platform, a supercapacitor can charge or discharge in a time of mere microseconds to seconds, whereas batteries take minutes to hours. However, the energy density for batteries is much higher. Hence many believe that the ideal backup energy storage device would be a hybrid of battery and supercapacitor. To be useful in that role, however, supercapacitors must be easily made and integrated onto chips. Here's where the UCLA model proves itself: its fabrication process is simple (a simple dielectric layer of lithium fluoride sandwiched between Au, Cu, or Al electrodes), it doesn't need an electrolyte (many other supercapacitors are halfway toward being miniature batteries in that they need electrolytes), and it can be integrated for device applications. It features a capacitance of tens of microfarad/cm^2 and charging rates of 10 kHz. (Ma and Yang, Applied Physics Letters, 19 September 2005; contact Yang Yang, UCLA, 310-825-4052, ; website,

The American Institute of Physics Bulletin of Physics News
Number 746 September 21, 2005 by Phillip F. Schewe, Ben Stein

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