Nonlinear Increase of X-ray Intensities from Thin Foils Irradiated with a 200 TW Femtosecond Laser PDF Download
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Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
We report, for the first time, that the energy of femtosecond optical laser pulses, E, with relativistic intensities I> 1021 W/cm2 is efficiently converted to X-ray radiation, which is emitted by "hot" electron component in collision-less processes and heats the solid density plasma periphery. As shown by direct high-resolution spectroscopic measurements X-ray radiation from plasma periphery exhibits unusual non-linear growth ~E4-5 of its power. The non-linear power growth occurs far earlier than the known regime when the radiation reaction dominates particle motion (RDR). Nevertheless, the radiation is shown to dominate the kinetics of the plasma periphery, changing in this regime (now labeled RDKR) the physical picture of the laser plasma interaction. Although in the experiments reported here we demonstrated by observation of KK hollow ions that X-ray intensities in the keV range exceeds ~1017 W/cm2, there is no theoretical limit of the radiation power. Therefore, such powerful X-ray sources can produce and probe exotic material states with high densities and multiple inner-shell electron excitations even for higher Z elements. Femtosecond laser-produced plasmas may thus provide unique ultra-bright X-ray sources, for future studies of matter in extreme conditions, material science studies, and radiography of biological systems.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
We report, for the first time, that the energy of femtosecond optical laser pulses, E, with relativistic intensities I> 1021 W/cm2 is efficiently converted to X-ray radiation, which is emitted by "hot" electron component in collision-less processes and heats the solid density plasma periphery. As shown by direct high-resolution spectroscopic measurements X-ray radiation from plasma periphery exhibits unusual non-linear growth ~E4-5 of its power. The non-linear power growth occurs far earlier than the known regime when the radiation reaction dominates particle motion (RDR). Nevertheless, the radiation is shown to dominate the kinetics of the plasma periphery, changing in this regime (now labeled RDKR) the physical picture of the laser plasma interaction. Although in the experiments reported here we demonstrated by observation of KK hollow ions that X-ray intensities in the keV range exceeds ~1017 W/cm2, there is no theoretical limit of the radiation power. Therefore, such powerful X-ray sources can produce and probe exotic material states with high densities and multiple inner-shell electron excitations even for higher Z elements. Femtosecond laser-produced plasmas may thus provide unique ultra-bright X-ray sources, for future studies of matter in extreme conditions, material science studies, and radiography of biological systems.
Author: Tobias Ostermayr Publisher: Springer ISBN: 303022208X Category : Science Languages : en Pages : 166
Book Description
This dissertation covers several important aspects of relativistically intense laser–microplasma interactions and some potential applications. A Paul-trap based target system was developed to provide fully isolated, well defined and well positioned micro-sphere-targets for experiments with focused peta-watt laser pulses. The laser interaction turned such targets into microplasmas, emitting proton beams with kinetic energies exceeding 10 MeV. The proton beam kinetic energy spectrum and spatial distribution were tuned by variation of the acceleration mechanism, reaching from broadly distributed spectra in relatively cold plasma expansions to spectra with relative energy spread as small as 20% in spherical multi-species Coulomb explosions and in directed acceleration processes. Numerical simulations and analytical calculations support these experimental findings and show how microplasmas may be used to engineer laser-driven proton sources. In a second effort, tungsten micro-needle-targets were used at a peta-watt laser to produce few-keV x-rays and 10-MeV-level proton beams simultaneously, both measured to have only few-μm effective source-size. This source was used to demonstrate single-shot simultaneous radiographic imaging with x-rays and protons of biological and technological samples. Finally, the dissertation discusses future perspectives and directions for laser–microplasma interactions including non-spherical target shapes, as well as thoughts on experimental techniques and advanced quantitative image evaluation for the laser driven radiography.
Author: Tetsuya Kawachi Publisher: Springer ISBN: 3319730258 Category : Science Languages : en Pages : 421
Book Description
These proceedings comprise a selection of invited and contributed papers presented at the 15th International Conference on X-Ray Lasers (ICXRL 2016), held at the Nara Kasugano International Forum, Japan, from May 22 to 27, 2016. This conference was part of an ongoing series dedicated to recent developments in the science and technology of x-ray lasers and other coherent x-ray sources with additional focus on supporting technologies, instrumentation and applications. The book showcases recent advances in the generation of intense, coherent x-rays, the development of practical devices and their applications across a wide variety of fields. It also discusses emerging topics such as plasma-based x-ray lasers, 4th generation accelerator-based sources and higher harmonic generations, as well as other x-ray generation schemes.
Author: Sophia Nan Chen Publisher: ISBN: Category : Languages : en Pages : 126
Book Description
Relativistic short pulse laser matter interactions are of great interest in the area of high energy density physics which includes the fields of astrophysics, inertial confinement fusion (ICF), and fast ignition (FI). Such interactions can result in the creation of hot dense matter at keV temperatures near solid density which is crucial for the studying radiation transport, understanding particle transport processes, and benchmarking of computer models in this plasma regime. The plasma by short pulse lasers, with intensity greater than 1019 W/cm2 and picosecond pulses, exists for only several tens of picoseconds, has a nonuniform temperature and density, and has a non-Maxwellian electron distribution thus making characterization a challenge. This work presents for the first time a systematic study of the temperature gradient inside of micron thick solid targets using K-shell spectroscopic techniques and demonstrates the importance of energetic electrons, temporal evolution of the plasma and opacity in the analysis of high intensity short pulse laser plasmas. Tamped titanium foils were with a short-pulse laser with intensity greater than 1019 W/cm2. Target parameters such as size, tamper material, and tamper thickness were varied to optimize heating and uniformity of the titanium plasma. Comparison of measured titanium K-shell spectra, from a 250 x 250 x 5 [mu]m3 titanium foil tamped with aluminum, with a collisional radiative model indicated that the front ~0.2 [mu]m reached a peak temperature of Tb>e, peak= 1300 eV at solid density. The remaining bulk material had temperature Te, bulk= 100 eV. This experimental result is consistent with previous observations and the use of a tamper greatly enhances the density uniformity of the plasma. Further reduction of the lateral and longitudinal target dimensions was needed to refine the analysis and prompted a second experiment. Five targets, with dimensions of 100 x 100 x 0.4 [mu]m3, had a copper foil were buried at different depths (i.e. 0-1.5 [mu]m) and irradiated with a short pulse laser with intensities greater than 1020 W/cm2. The measured K-shell spectra again indicated a temperature gradient in the longitudinal direction inside the target. Analysis using a hydrodynamic code and a collisional radiative atomic code showed that the hot electron population, time dependent plasma conditions, and opacity significantly alters the calculated K-shell line ratios thus producing up to a factor of two error in plasma temperature.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
X-ray techniques have evolved over decades to become highly refined tools for a broad range of investigations. Importantly, these approaches rely on X-ray measurements that depend linearly on the number of incident X-ray photons. The advent of X-ray free electron lasers (XFELs) is opening the ability to reach extremely high photon numbers within ultrashort X-ray pulse durations and is leading to a paradigm shift in our ability to explore nonlinear X-ray signals. However, the enormous increase in X-ray peak power is a double-edged sword with new and exciting methods being developed but at the same time well-established techniques proving unreliable. Consequently, accurate knowledge about the threshold for nonlinear X-ray signals is essential. Here in this paper we report an X-ray spectroscopic study that reveals important details on the thresholds for nonlinear X-ray interactions. By varying both the incident X-ray intensity and photon energy, we establish the regimes at which the simplest nonlinear process, two-photon X-ray absorption (TPA), can be observed. From these measurements we can extract the probability of this process as a function of photon energy and confirm both the nature and sub-femtosecond lifetime of the virtual intermediate electronic state.
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Author: Tobias Ostermayr
Author: Tetsuya Kawachi
Author: Sophia Nan Chen
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Author: Anders Sjögren
Author: Matthias Grätz
Author: Howard Richard Kelly
Author: D. Palmer Smitherman
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