A interferometer beam of wavelength crosses a plasma chord of length in which the…

PHYSICS · Multi-part · Fermi University Physics · Plasma Physics · Waves in plasmas · Laboratory, industrial and space plasmas

Plasma Physics, Ch Plasma oscillations and light in an unmagnetised plasma

Problem

\mathrm{CO_2}

interferometer beam of wavelength

\lambda = 10.6\,\mu\mathrm{m}

crosses a plasma chord of length

L = 2.5\,\mathrm{m}

in which the electron density is uniform at

n_e = 3.0\times10^{19}\,\mathrm{m^{-3}}

, with

\omega \gg \omega_{pe}

along the whole path. ((a)) Calculate the phase shift

\Delta\phi

acquired relative to a vacuum path of the same length. ((b)) Express this as a fraction of one fringe (one fringe corresponds to

2\pi\,\mathrm{rad}