Bunching instability of rotating relativistic electron layers and coherent synchrotron radiation

Journal Article · Fri Apr 01 00:00:00 EST 2005 · Physical Review. E, Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics

DOI:https://doi.org/10.1103/PhysRevE.71.046502· OSTI ID:20641434

Schmekel, Bjoern S; Lovelace, Richard V. E.; Wasserman, Ira M ^[1]

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1. Department of Physics, Cornell University, Ithaca, New York 14853 (United States)

We study the stability of a collisionless, relativistic, finite-strength, cylindrical layer of charged particles in free space by solving the linearized Vlasov-Maxwell equations and compute the power of the emitted electromagnetic waves. The layer is rotating in an external magnetic field parallel to the layer. This system is of interest to understanding the high brightness temperature of pulsars which cannot be explained by an incoherent radiation mechanism. Coherent synchrotron radiation has also been observed recently in bunch compressors used in particle accelerators. We consider equilibrium layers with a 'thermal' energy spread and therefore a nonzero radial thickness. The particles interact with their retarded electromagnetic self-fields. The effect of the betatron oscillations is retained. A short azimuthal wavelength instability is found which causes a modulation of the charge and current densities. The growth rate is found to be an increasing function of the azimuthal wave number, a decreasing function of the Lorentz factor, and proportional to the square root of the total number of electrons. We argue that the growth of the unstable perturbation saturates when the trapping frequency of electrons in the wave becomes comparable to the growth rate. Owing to this saturation we can predict the radiation spectrum for a given set of parameters. Our predicted brightness temperatures are proportional to the square of the number of particles and scale by the inverse five-third power of the azimuthal wave number which is in rough accord with the observed spectra of radio pulsars.

• OSTI ID: 20641434
• Journal Information: Physical Review. E, Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics, Vol. 71, Issue 4; Other Information: DOI: 10.1103/PhysRevE.71.046502; (c) 2005 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1063-651X
• Country of Publication: United States
• Language: English

Related Subjects

43 PARTICLE ACCELERATORS
ACCELERATORS
BEAM BUNCHING
BETATRON OSCILLATIONS
BOLTZMANN-VLASOV EQUATION
CHARGED PARTICLES
COLLISIONLESS PLASMA
CURRENT DENSITY
CYLINDRICAL CONFIGURATION
ELECTRON BEAMS
EMISSION
INSTABILITY
MAGNETIC FIELDS
MAXWELL EQUATIONS
PULSARS
RELATIVISTIC RANGE
SATURATION
STABILITY
SYNCHROTRON RADIATION
TRAPPING
WAVELENGTHS