Measurement of local density and magnetic field of a magnetized plasma using Raman scattering from a focused laser pulse

We investigated the possibility of pin pointing the local density and magnetic field of an inhomogeneous, magnetized plasma by stimulated Raman scattering of a pump laser pulse focused on a desired position. As the Raman growth rate is proportional to the pump pulse amplitude, the spectral peak shift of the scattered signal is, though it is a spatially integrated one, expected to be determined dominantly by that from the focal position of the pump pulse. From a theoretical estimation, we found a condition of the pulse duration and plasma density for such an expectation to properly work. It was confirmed by two-dimensional particle-in-cell simulations that as long as the pulse duration is long and the length scale of the plasma inhomogeneity is large compared to the Rayleigh length, the spectral bandwidth of the spatially integrated Raman signal can be narrow enough to distinguish the peak position with good enough resolution.