Influence of the contrast of a heating pulse on the heating and compression of spherical microtargets

The effect of a prepulse with a rising amplitude on the absorption and compression of microspheres filled with the DT gas was investigated for ratios of the power of a prepulse to the power of the main pulse in the range 10 ^– 9–10 ^– 4. The experiments were carried out using the PROGRESS laser facility (λ = 1.06 μm, q ≤ 2 X 10¹⁵ W/cm²). An increase of the relative power of a prepulse from 10 ^– 8 to 10 ^– 6–10 ^– 4 reduced the absorption coefficient by a factor of 1.5–2 and increased the degree of compression by a factor of 2–3. An analytic model allowing for the influence of a prepulse was developed. The experimental results were compared with the model calculations.