Self-generated Terahertz Radiation and Relativistic Optics: A Novel Diagnostic for Table top Laser Particle Accelerators

该项目侧重于目标正常鞘层加速（TNSA）场的时空特征，该场负责相对论性激光-固体相互作用期间离子和质子的加速。理论研究预测，这些场的数量级为TV/m，定位在与激光波长相当的空间维度上，持续时间可能是激光脉冲持续时间的几倍。这些场的极端时空特性使得外部探测器难以探测到它们。在这个项目中，我们提出了一种新的，非侵入性的诊断来精确测量这些领域。这个原理很简单，但却可以对这些极端领域进行真正有力的表征。由于TNSA场的瞬态性质，目标后部的电子-离子鞘应表现为振荡偶极子。这种带电粒子的加速运动在太赫兹频域诱发电磁辐射。最初的实验是在耶拿光学和量子电子学研究所（IOQ）与光子技术研究所（IPHT）合作的耶拿ti -蓝宝石系统（JETI）激光设备上进行的。基于这些有希望的实验结果，我们的目标是通过先进的太赫兹诊断和使用等离子体模拟代码的计算机模拟研究来系统地研究TNSA。最终目标是将发射的太赫兹辐射的特征与TNSA场的动力学联系起来，从而开发出一种独特的诊断工具，可用于优化激光离子加速。

The project focuses on the spatio-temporal characterization of the Target Normal Sheath Acceleration (TNSA) field which is responsible for the acceleration of ions and protons during relativistic laser-solid interaction. Theoretical studies have predicted that these fields are of the order of TV/m, localized in a spatial dimension comparable to the laser wavelength and may last several times the laser pulse duration. The extreme spatio-temporal characteristics of these fields make them difficult to be accessed by external probes.In this project we propose a novel, non-invasive diagnostic for the accurate measurement of these fields. The principle is simple but allows a truly powerful characterization of these extreme fields. Due to the transient nature of the TNSA field, the electron-ion sheath at the rear of the target should act as an oscillating dipole. This accelerated motion of charged particles induces electromagnetic radiation in the THz frequency domain. Initial experiments were carried out at the JETI (JEna TI-Sapphire system) laser facility at the IOQ (Institute for Optics and Quantum electronics in cooperation with the IPHT (Institute of Photonic Technology) Jena. Based on the promising results from these experiments we aim at investigating systematically the TNSA by means of both advanced THz diagnostics and computer simulation studies using Plasma Simulation Code. The ultimate goal is to relate the features of the emitted THz radiation to the dynamics of the TNSA field, and thus developing a unique diagnostic tool which can be employed to optimise the ion acceleration with lasers.