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arXiv 2007.08677physics.plasm-ph
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种子磁场作用下相对论短脉冲laser与等离子体相互作用中强表面磁场的产生

Strong surface magnetic field generation in relativistic short pulse laser-plasma interaction with an applied seed magnetic field

Kathleen Weichman, Alexander P. L. Robinson, Masakatsu Murakami, Alexey V. Arefiev

摘要:

虽然等离子体往往表现出抗磁性,我们证明了一个薄的不透明的目标与嵌入式目标横向种子磁场$B_\mathrm{seed}$的激光照射可以触发一个数量级的更强的磁场的产生与相反的符号在目标表面。强表面场产生发生在激光脉冲相对论强度时,并且是由与穿过靶的激光加热电子的回旋加速器旋转相关的电流和冷电子的补偿电流引起的。我们推导出一个预测缩放为这个表面场的生成,$B_\mathrm{gen} \sim - 2 πB_\mathrm{seed} Δx/λ_0$,其中$Δx$是目标厚度和$λ_0$是激光波长,并进行一维和二维粒子在细胞模拟,以确认其适用性在很宽的条件范围。我们还表明,种子和表面产生的磁场可以有一个强烈的影响,应用相关的等离子体动力学,例如,从$μ$ m厚的激光照射的目标与千特斯拉级种子磁场的整体膨胀和离子加速大幅改变。

英文摘要:

While plasma often behaves diamagnetically, we demonstrate that the laser irradiation of a thin opaque target with an embedded target-transverse seed magnetic field $B_\mathrm{seed}$ can trigger the generation of an order-of-magnitude stronger magnetic field with opposite sign at the target surface. Strong surface field generation occurs when the laser pulse is relativistically intense and results from the currents associated with the cyclotron rotation of laser-heated electrons transiting through the target and the compensating current of cold electrons. We derive a predictive scaling for this surface field generation, $B_\mathrm{gen} \sim - 2 πB_\mathrm{seed} Δx/λ_0$, where $Δx$ is the target thickness and $λ_0$ is the laser wavelength, and conduct 1D and 2D particle-in-cell simulations to confirm its applicability over a wide range of conditions. We additionally demonstrate that both the seed and surface-generated magnetic fields can have a strong impact on application-relevant plasma dynamics, for example substantially altering the overall expansion and ion acceleration from a $μ$m-thick laser-irradiated target with a kilotesla-level seed magnetic field.

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