Abstract
The laser ablation pressure is often estimated by an exponential scaling law, which is determined by integral averaging of 1–2 ns short pulses. Here, we report a direct, continuous measurement of ablation pressure of a 3–10 ns ramp 351-nm laser pulse. Aluminum is deposited on LiF window, ablation pressure is inferred from the particle velocity of interface using the backward integration method, combined with incident ramp shaped laser intensity, and the real-time laser-driven ablation pressure as a function of incident laser power density on an aluminum target is obtained. For the same ablation pressure scale, when intensity is higher than 1TW/cm2, the surface illuminated intensity of laser should be modified with the cosine of incident angle, which agrees well with the modified Manheimer model [Scheiner and Schmitt, Phys. Plasmas 26(2), 024502 (2019)]. On the other hand, the incidence angle has the least effect when the intensity is below 0.1 TW/cm2. In the range of 0.1–1 TW/cm2, a significant loss in ablation pressure is observed, deviating notably from the exponential scaling relationship. This characteristic makes the laser direct drive ramp loading technique unfriendly to elastoplastic and phase transition problems.
Published Version
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