We have recently proposed a new technique of plasma tailoring by laser-driven hydrodynamic shockwaves generated on both sides of a gas jet [Marquès et al., Phys. Plasmas 28, 023103 (2021)]. In a continuation of this numerical work, we study experimentally the influence of the tailoring on proton acceleration driven by a high-intensity picosecond laser in three cases: without tailoring, by tailoring only the entrance side of the picosecond laser, and by tailoring both sides of the gas jet. Without tailoring, the acceleration is transverse to the laser axis, with a low-energy exponential spectrum, produced by Coulomb explosion. When the front side of the gas jet is tailored, a forward acceleration appears, which is significantly enhanced when both the front and back sides of the plasma are tailored. This forward acceleration produces higher-energy protons, with a peaked spectrum, and is in good agreement with the mechanism of collisionless shock acceleration (CSA). The spatiotemporal evolution of the plasma profile is characterized by optical shadowgraphy of a probe beam. The refraction and absorption of this beam are simulated by post-processing 3D hydrodynamic simulations of the plasma tailoring. Comparison with the experimental results allows estimation of the thickness and near-critical density of the plasma slab produced by tailoring both sides of the gas jet. These parameters are in good agreement with those required for CSA.

中文翻译：

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通过两个激光驱动的流体动力冲击波的碰撞，在气体射流中产生等离子板中的质子的无碰撞冲击加速

我们最近提出了一种通过在气体射流两侧产生激光驱动的流体动力冲击波来进行等离子体裁剪的新技术[Marquès et al., Phys. 等离子 28, 023103 (2021)]。在这项数值工作的延续中，我们通过实验研究了三种情况下剪裁对高强度皮秒激光驱动的质子加速的影响：不剪裁、仅剪裁皮秒激光的入口侧和剪裁两侧气体射流的。在没有剪裁的情况下，加速度横向于激光轴，具有由库仑爆炸产生的低能量指数谱。当气体射流的前侧被定制时，会出现向前的加速度，当等离子体的前侧和后侧都被定制时，该向前加速度显着增强。这种向前加速产生更高能量的质子，具有峰值光谱，并且与无碰撞冲击加速（CSA）的机制非常一致。等离子体轮廓的时空演化通过探测光束的光学阴影来表征。该光束的折射和吸收通过等离子体剪裁的后处理 3D 流体动力学模拟进行模拟。与实验结果进行比较，可以估计通过调整气体射流两侧产生的等离子板的厚度和近临界密度。这些参数与 CSA 所需的参数非常一致。