Observation of fast-ion Doppler-shifted cyclotron resonance with shear Alfvén waves
نویسندگان
چکیده
The Doppler-shifted cyclotron resonance −kzvz= f between fast ions and shear Alfvén waves is experimentally investigated , wave frequency; kz, axial wavenumber; vz, fast-ion axial speed; f, fast-ion cyclotron frequency . A test particle beam of fast ions is launched by a Li+ source in the helium plasma of the LArge Plasma Device LAPD W. Gekelman, H. Pfister, Z. Lucky, J. Bamber, D. Leneman, and J. Maggs, Rev. Sci. Instrum. 62, 2875 1991 , with shear Alfvén waves SAW amplitude B /B up to 1% launched by a loop antenna. A collimated fast-ion energy analyzer measures the nonclassical spreading of the beam, which is proportional to the resonance with the wave. A resonance spectrum is observed by launching SAWs at 0.3–0.8 ci. Both the magnitude and frequency dependence of the beam-spreading are in agreement with the theoretical prediction using a Monte Carlo Lorentz code that launches fast ions with an initial spread in real/velocity space and random phases relative to the wave. Measured wave magnetic field data are used in the simulation. © 2008 American Institute of Physics. DOI: 10.1063/1.2996323
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Doppler-shifted cyclotron resonance of fast ions with circularly polarized shear Alfvén waves
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