Beam focusing and consequences for Doppler Backscattering measurements

• DOI: 10.48550/arxiv.2408.12919
• Publication Date: 2024-08-23
• Authors: Juan Ruiz Ruiz; F. I. Parra; V. H. Hall-Chen; Nathan Belrhali; Carine Giroud; J.C. Hillesheim; Nicolas Lopez; Jet Contributors
• Keywords: Backscatter (email)

The phenomenon of beam focusing microwaves in a plasma near turning-point caustic is discussed the context analytical solution to Gaussian beam-tracing equations 2D linear-layer problem. location maximum and width at that are studied terms initial conditions. analytic used study effect this on Doppler backscattering (DBS). We find filter function characterises scattering intensity contributions along path through inversely proportional width, predicting enhanced from region. show DBS signal enhancement for small incident angles between density gradient due not forward scattering. model predict measurement $k_y$ density-fluctuation wavenumber power spectrum via DBS, showing spectral exponent turbulent, intermediate-to-high might be quantitatively measurable but peak corresponding driving scale turbulent cascade.