Formation of Ultrarelativistic Electron Rings from a Laser-Wakefield Accelerator.
Ultrarelativistic-energy electron ring structures have been observed from laser-wakefield acceleration experiments in the blowout regime. These electron rings had 170-280 MeV energies with 5%-25% energy spread and ∼10  pC of charge and were observed over a range of plasma densities and compositions. Three-dimensional particle-in-cell simulations show that laser intensity enhancement in the wake leads to sheath splitting and the formation of a hollow toroidal pocket in the electron density around the wake behind the first wake period. If the laser propagates over a distance greater than the ideal dephasing length, some of the dephasing electrons in the second period can become trapped within the pocket and form an ultrarelativistic electron ring that propagates in free space over a meter-scale distance upon exiting the plasma. Such a structure acts as a relativistic potential well, which has applications for accelerating positively charged particles such as positrons.
Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, USA.
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Pollock
University of California, Los Angeles, 405 Hilgard Avenue, Los Angeles, California 90095, USA.
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Tsung
Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, USA.
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Albert
University of California, Los Angeles, 405 Hilgard Avenue, Los Angeles, California 90095, USA.
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Shaw
University of California, Los Angeles, 405 Hilgard Avenue, Los Angeles, California 90095, USA.
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Clayton
University of California, Los Angeles, 405 Hilgard Avenue, Los Angeles, California 90095, USA.
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Davidson
University of California, Los Angeles, 405 Hilgard Avenue, Los Angeles, California 90095, USA.
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Lemos
University of California, Los Angeles, 405 Hilgard Avenue, Los Angeles, California 90095, USA.
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Marsh
Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, USA.
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Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, USA.
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Ralph
University of California, Los Angeles, 405 Hilgard Avenue, Los Angeles, California 90095, USA.
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Mori
University of California, Los Angeles, 405 Hilgard Avenue, Los Angeles, California 90095, USA.
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