From: LARRY KLAES (email@example.com)
Date: Tue Aug 27 2002 - 12:18:59 PDT
See Item 2
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Sent: Monday, August 26, 2002 4:03 PM
Subject: Physics News Update 601
PHYSICS NEWS UPDATE
The American Institute of Physics Bulletin of Physics News
Number 601 August 26, 2002 by Phillip F. Schewe, Ben Stein, and James Riordon
LEFT HANDED MATERIALS (LHM) were the hot topic at the recent Progress on Electromagnetics Research Symposium in Boston (http://www.piers.org/piers2k2/). In LHM both the permittivity (basically the response of the material to an external electric field) and the permeability (response to a magnetic field) have negative values. (It's rare for a material to have either negative permittivity or negative permeability, much less both.) This results in a negative index of refraction; when light falls on a LHM sample it refracts in a direction opposite to that for conventional materials; this "left handed" property makes an LHM a great candidate solid state filter or antenna (see Update item at http://www.aip.org/enews/physnews/2000/split/pnu476-1.htm). LHM are "metamaterials," consisting of combinations of C-shaped metal rings (split ring resonators, or SRR) and tiny metal rods. Although there is still some controversy over the theoretical interpretation of left handed optical effects, several labs now successfully tested the materials.
So far the split ring resonators have been planar (they're arranged like parallel miniature printed circuit units slotted into a motherboard) so the optical effects have also been two-dimensional. But now a group at ETHZ lab in Zurich are close to getting 3D resonators to work, which would allow an LHM to operate in all three dimensions (see figure). According to Olivier Martin (firstname.lastname@example.org, 41-163-25722) left handed materials "could change some fundamental concepts in telecommunications," especially for making possible efficient, isotropic, ultra-small antennas. (Gay-Balmaz and Martin, Applied Physics Letters, 29 July 2002)
PRODUCING LASER-DRIVEN ION JETS with potential fusion and medical applications has reached another milestone. Previously several labs (e.g., Michigan, Livermore, Rutherford, LULI) have produced multi-MeV protons by shining intense microbursts of laser light onto thin targets; the intense electric fields of the light kick the protons out the back of the target in powerful jets. Now, for the first time, a group of physicists (Max-Planck-Institute for Quantum Optics, Garching, Germany; Gesellschaft fuer Schwerionenforschung, Darmstadt, Germany; General Atomics, San Diego, US; and Laboratoire pour l'Utilisation des Lasers Intenses (LULI) in Palaiseau, France) have succeeded in accelerating heavier ions (fluorine and carbon) to energies above 100 MeV (more than 5 MeV/nucleon). The laser light at the LULI lab is impressive: 300-fs pulses, each containing 30 J of energy and a power of up to 5 x 10^19 W/cm^2, producing electric fields with a strength of more than 10^12 V/m (some ten times higher than the fields that hold an electron inside a hydrogen atom), conditions only matched by two other lasers worldwide, Vulcan in Rutherford, UK and Gekko-PW in Osaka, Japan.
In the new experiments the target was heated in order to drive off hydrocarbon impurities in the target which would otherwise have added unwanted protons which screen the electric fields for the heavier ions, thus preventing their efficient acceleration. The high charge state ions are accelerated in the space of about 10 microns; at a conventional accelerator to reach these energies a distance of 100 m would have been required. Furthermore, in the LULI experiment the jets are bright (10^12 particles per burst) and well collimated, possibly making them useful for future particle physics or fusion work (see the colorful figure at http://www.aip.org/mgr/png). In the near term (the next year or two) this whole procedure will be carried out with tabletop lasers, facilitating the in-house production of isotopes hospitals need for therapy and imaging, such as C-11, N-13, O-15, and F-18.
Another potential use for the outgoing ion beams is to heat macroscopic samples in microscopic time. According to team member Manuel Hegelich (Max Planck Institute for Quantum Optics, email@example.com,) an outgoing burst of fluorine ions could heat a 100-micron-sized secondary target to a temperature of 200-300 eV (equivalent to 100,000 K) in mere picoseconds. During this tick of time the crystal of atoms in the target would be heated isochorically (that is, the atoms would not have time to expand) thus approximating the condition inside stars. (Hegelich et al., Physical Review Letters, 19 August 2002)
CORRECTION: Leptoquarks, hypothetical particles that might help to turn quarks into leptons and leptons into quarks, are associated not with the idea of supersymmetry (Update 600), but with the so-called grand unified theory (or GUT), another elaboration and extension of the standard model of particle physics.
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