Absorption of the laser radiation by the laser plasma with gas microjet targets

An upper limit of absorption of the laser radiation in the plasma produced in a gas jet Xe target with the average density of (3–6) $\times$ 10$^{18}$ cm$^{-3}$ and the effective diameter of 0.7 mm is found. It is equal to $\approx$ 50% and remains constant under any variation in this range of densities. This result contradicts both theoretical assessments that have predicted virtually complete absorption and results of earlier experiments with the laser spark in an unlimited stationary Xe gas with the same density, where the upper limit of absorption was close to 100%. An analysis shows that nonlinearity of absorption and plasma nonequilibrium lead to the reduction of the absorption coefficient that, along with the limited size of plasma, can explain the experimental results.