Main-beam polarization properties of four-element sequential-rotation arrays with arbitrary radiators

The measurements were made in Feb. 1982 with the Parkes 64 m telescope using a corrugated waveguide horn with total half-power beam width of 15′, the first sidelobes being 19 dB down, resulting in an aperture efficiency ηA=0.53±0.007, a main beam efficiency of ηmb=0.80±0.005 and a ratio of source flux to antenna temperature of Γ=0.62±0.1 K/Jy (Murray, priv. comm.). A cooled two channel FET frontend used in the frequency switching mode with Δν = 2 MHz resulted in a system noise temperature at zenith of Tsyst = 40 K for one channel and Tsyst = 50 K for the other. Each frontend channel received a single polarization mode, and this radiation was then further analysed in a 2 × 512 channel autocorrelation spectrometer set at a channel separation of 3.906 KHz corresponding to a velocity resolution of V = 0.824 km s−1. Hanning smoothed this resulted in a σT = 0.05 K for the average of both polarization.

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Assessment of stray radiation outside the main beam of the RUM-17 radiological device

Biomedical Engineering ◽

10.1007/bf01674358 ◽

1992 ◽

Vol 26 (3) ◽

pp. 133-135

Author(s):

V. N. Vasil'ev ◽

R. V. El'tsov

Keyword(s):

Main Beam ◽

Stray Radiation

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Relativistic self-focusing of a rippled laser beam in a plasma

Journal of Plasma Physics ◽

10.1017/s0022377899008016 ◽

1999 ◽

Vol 62 (4) ◽

pp. 389-396 ◽

Cited By ~ 10

Author(s):

M. V. ASTHANA ◽

A. GIULIETTI ◽

DINESH VARSHNEY ◽

M. S. SODHA

Keyword(s):

Refractive Index ◽

Laser Beam ◽

The Self ◽

Laser Beams ◽

Radial Dependence ◽

Main Beam ◽

Gaussian Laser Beam ◽

Self Focusing ◽

Saturation Effects ◽

Paraxial Ray

This paper presents an analysis of the relativistic self-focusing of a rippled Gaussian laser beam in a plasma. Considering the nonlinearity as arising owing to relativistic variation of mass, and following the WKB and paraxial-ray approximations, the phenomenon of self-focusing of rippled laser beams is studied for arbitrary magnitude of nonlinearity. Pandey et al. [Phys. Fluids82, 1221 (1990)] have shown that a small ripple on the axis of the main beam grows very rapidly with distance of propagation as compared with the self-focusing of the main beam. Based on this analogy, we have analysed relativistic self-focusing of rippled beams in plasmas. The relativistic intensities with saturation effects of nonlinearity allow the nonlinear refractive index in the paraxial regime to have a slower radial dependence, and thus the ripple extracts relatively less energy from its neighbourhood.

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