Laserem buzené zdroje rentgenového záření pro zobrazování

With the advent of high-power lasers in recent decades, a unique source of hard X-ray radiation has become availible. This source of collimated, broadband, femtosecond, incoherent and hard X-ray radiation is produced when a focused laser with intensity above 10^18 W/cm^2 collides with a gas target. The strong electric field of the laser pulse ionizes the gas and interacts with the plasma generating a strong plasma wake wave. This space charge separation inside the target generates longitudal electric fields of the order of 100 GV/m. This resulting electrostatic wakefield accelerates the electrons to relativistic velocities and causes them to travel in oscillatory motion behind the laser pulse, producing hard and collimated X-ray radiation. This thesis is focused on a theoretical evaluation and an experimental design of this laser-plasma X-ray source. Furthermore, we consider the source's unique properties for novel imaging applications.Díky příchodu vysoko-intenzitních laserů v posledních dekádách je k dispozici nový zdroj tvrdého rentgenového záření. Tento zdroj kolimovaného, širokopásmového, ultrakrátkého a prostorově koherentního rentgenového záření je produkován když vstoupí laserový puls s intenzitou nad 10^18 W/cm^2 v ohnisku do plynného terče. Silné elektrické pole laseru ionizuje plyn a interaguje se vzniklým plazmatem, čímž excituje silnou brázdovou vlnu v plazmatu. Takto vzniklé rozložení náboje v terči generuje podélné elektrické pole v řádu 100 GV/m. Vzniklé elektrostatické brázdové pole urychluje elektrony na relativistické rychlosti a způsobuje, že oscilují za laserovým pulsem, což produkuje kolimované rentgenové záření. Tato práce je zaměřena na teoretické vyhodnocení a experimentální design tohoto laser-plazmového rentgenového zdroje. Dále diskutujeme unikátní vlastnosti zdroje vhodné pro moderní aplikace v zobrazování.Department of Chemical Physics and OpticsKatedra chemické fyziky a optikyMatematicko-fyzikální fakultaFaculty of Mathematics and Physic

Anomalous Relativistic Emission from Self-Modulated Plasma Mirrors

The interaction of relativistically intense laser pulse with a plasma mirror produces harmonics of the incident frequency co-propagating in the direction of specular reflection due to the plasma mirror surface oscillating with velocity close to the speed of light. This mechanism has shown its potential for realization of a bright source of extreme ultraviolet radiation and attosecond pulses. Here, we reveal an unexpected transition of this well-known process into a new regime of efficient extreme ultraviolet radiation generation. A novel mechanism of relativistic emission of radiation from plasma mirrors is identified with an extraordinary property that instead of following specular reflection, the radiation is emitted in the direction along the plasma mirror surface. With analytical calculations and numerical particle-in-cell simulations, we show that this radiation originates from laser-driven non-linear oscillations of relativistic electron nanobunches that are generated by a plasma surface instability and propagate along the plasma mirror surface.Comment: 6 pages, 3 figure

Bright coherent attosecond X-ray pulses from beam-driven relativistic mirrors

Bright ultrashort X-ray pulses allow scientists to observe ultrafast motion of atoms and molecules. Coherent light sources, such as the X-ray free electron laser (XFEL), enable remarkable discoveries in cell biology, protein crystallography, chemistry or materials science. However, in contrast to optical lasers, lack of X-ray mirrors demands XFELs to amplify radiation over a single pass, requiring tens or hundreds of meters long undulators to produce bright femtosecond X-ray pulses. Here, we propose a new ultrafast coherent light source based on laser reflection from a relativistic mirror driven by a relativistic charged particle beam in micrometer-scale plasma. We show that reflection of millijoule-level laser pulses from such mirrors can produce bright, coherent and bandwidth-tunable attosecond X-ray pulses with peak intensity and spectral brightness comparable to XFELs. In addition, we find that beam-driven relativistic mirrors are highly robust, with laser-induced damage threshold exceeding solid-state components by at least two orders of magnitude. Our results promise a new way for bright coherent attosecond X-ray pulse generation, suitable for unique applications in fundamental physics, biology and chemistry

Laser-driven hard X-ray source for imaging applications

With the advent of high-power lasers in recent decades, a unique source of hard X-ray radiation has become availible. This source of collimated, broadband, femtosecond, incoherent and hard X-ray radiation is produced when a focused laser with intensity above 10^18 W/cm^2 collides with a gas target. The strong electric field of the laser pulse ionizes the gas and interacts with the plasma generating a strong plasma wake wave. This space charge separation inside the target generates longitudal electric fields of the order of 100 GV/m. This resulting electrostatic wakefield accelerates the electrons to relativistic velocities and causes them to travel in oscillatory motion behind the laser pulse, producing hard and collimated X-ray radiation. This thesis is focused on a theoretical evaluation and an experimental design of this laser-plasma X-ray source. Furthermore, we consider the source's unique properties for novel imaging applications

Natural aging and early precipitation stages in Al-Mg-Si alloys

Modern aluminium alloys 60xx are rich in sillicon and magnesium. They are easy to machine, are weldable, and can be precipitation-hardened, especially se- ries 6061, which we focus on in this thesis. Series 6061 alloy is currently the most general-purpose industrially used aluminium alloy. The purpose of this thesis is to analyze the natural and artificial aging of these alloys through the utilization of positron annihilation spectroscopy and coincidence Doppler broadening of anni- hilation radiation methods. Our goal is precise analysis of precipiation processes, which occur due to natural or artifical aging of the alloy. Although artifical aging in aluminium alloys is a well researched area, understanding and description of key mechanisms controlling the natural aging especially in the early stages of pre- cipitation is not yet sufficiently explained. We use modern methods of positron annihilation spectroscopy to understand and confirm our clustering hypotheses. 1Moderní hliníkové slitiny 60xx jsou bohaté na křemík a hořčík, díky čemuž jsou snadno obráběny, svářeny a srážkově vytvrzovány. Konkrétně pak srážkově vytvrzená slitina Al-Mg-Si s názvem řady 6061, které se v této práci budeme věnovat, je nejobecněji průmyslově využívanou hliníkovou slitinou. Smyslem této práce je shrnout dosavadní literaturu a pochopit procesy přirozeného a umě- lého stárnutí využitím metod pozitronové anihilační spektroskopie a koincidenční spektroskopie Dopplerovského rozšíření anihilačního píku. Cílem je přesná ana- lýza precipitačních procesů, které nastávají v důsledku přirozeného nebo umělého stárnutí slitiny. Ačkoliv je umělé stárnutí hliníkových slitin dobře prozkoumanou oblastí, pochopení a popis klíčových mechanismů ovlivňujících přirozené stárnutí především v raných stádiích precipitace se doposud nepodařilo dostatečně vy- světlit. Pro pochopení a ověření hypotéz shlukování do klastrů v různých stádiích používáme moderní metody pozitronové anihilační spektroskopie. 1Katedra fyziky nízkých teplotDepartment of Low Temperature PhysicsFaculty of Mathematics and PhysicsMatematicko-fyzikální fakult

Laserem buzené zdroje rentgenového záření pro zobrazování

With the advent of high-power lasers in recent decades, a unique source of hard X-ray radiation has become availible. This source of collimated, broadband, femtosecond, incoherent and hard X-ray radiation is produced when a focused laser with intensity above 10^18 W/cm^2 collides with a gas target. The strong electric field of the laser pulse ionizes the gas and interacts with the plasma generating a strong plasma wake wave. This space charge separation inside the target generates longitudal electric fields of the order of 100 GV/m. This resulting electrostatic wakefield accelerates the electrons to relativistic velocities and causes them to travel in oscillatory motion behind the laser pulse, producing hard and collimated X-ray radiation. This thesis is focused on a theoretical evaluation and an experimental design of this laser-plasma X-ray source. Furthermore, we consider the source's unique properties for novel imaging applications.Díky příchodu vysoko-intenzitních laserů v posledních dekádách je k dispozici nový zdroj tvrdého rentgenového záření. Tento zdroj kolimovaného, širokopásmového, ultrakrátkého a prostorově koherentního rentgenového záření je produkován když vstoupí laserový puls s intenzitou nad 10^18 W/cm^2 v ohnisku do plynného terče. Silné elektrické pole laseru ionizuje plyn a interaguje se vzniklým plazmatem, čímž excituje silnou brázdovou vlnu v plazmatu. Takto vzniklé rozložení náboje v terči generuje podélné elektrické pole v řádu 100 GV/m. Vzniklé elektrostatické brázdové pole urychluje elektrony na relativistické rychlosti a způsobuje, že oscilují za laserovým pulsem, což produkuje kolimované rentgenové záření. Tato práce je zaměřena na teoretické vyhodnocení a experimentální design tohoto laser-plazmového rentgenového zdroje. Dále diskutujeme unikátní vlastnosti zdroje vhodné pro moderní aplikace v zobrazování.Institute of Physics of Charles UniversityFyzikální ústav UKMatematicko-fyzikální fakultaFaculty of Mathematics and Physic

Laser-driven hard X-ray source for imaging applications

With the advent of high-power lasers in recent decades, a unique source of hard X-ray radiation has become availible. This source of collimated, broadband, femtosecond, incoherent and hard X-ray radiation is produced when a focused laser with intensity above 10^18 W/cm^2 collides with a gas target. The strong electric field of the laser pulse ionizes the gas and interacts with the plasma generating a strong plasma wake wave. This space charge separation inside the target generates longitudal electric fields of the order of 100 GV/m. This resulting electrostatic wakefield accelerates the electrons to relativistic velocities and causes them to travel in oscillatory motion behind the laser pulse, producing hard and collimated X-ray radiation. This thesis is focused on a theoretical evaluation and an experimental design of this laser-plasma X-ray source. Furthermore, we consider the source's unique properties for novel imaging applications

Natural aging and early precipitation stages in Al-Mg-Si alloys

Modern aluminium alloys 60xx are rich in sillicon and magnesium. They are easy to machine, are weldable, and can be precipitation-hardened, especially se- ries 6061, which we focus on in this thesis. Series 6061 alloy is currently the most general-purpose industrially used aluminium alloy. The purpose of this thesis is to analyze the natural and artificial aging of these alloys through the utilization of positron annihilation spectroscopy and coincidence Doppler broadening of anni- hilation radiation methods. Our goal is precise analysis of precipiation processes, which occur due to natural or artifical aging of the alloy. Although artifical aging in aluminium alloys is a well researched area, understanding and description of key mechanisms controlling the natural aging especially in the early stages of pre- cipitation is not yet sufficiently explained. We use modern methods of positron annihilation spectroscopy to understand and confirm our clustering hypotheses.

Generation of intense magnetic wakes by relativistic laser pulses in plasma

Abstract The emergence of petawatt lasers focused to relativistic intensities enables all-optical laboratory generation of intense magnetic fields in plasmas, which are of great interest due to their ubiquity in astrophysical phenomena. In this work, we study generation of spatially extended and long-lived intense magnetic fields. We show that such magnetic fields, scaling up to the gigagauss range, can be generated by interaction of petawatt laser pulses with relativistically underdense plasma. With three-dimensional particle-in-cell simulations we investigate generation of magnetic fields with strengths up to $$10^{10}$$ 10 10 G and perform a large multi-parametric study of magnetic field in dependence on dimensionless laser amplitude $$a_{0}$$ a 0 and normalized plasma density $$n_{e}/n_{c}$$ n e / n c . The numerical results yield scaling laws that closely follow derived analytical result $$B \propto \sqrt{a_{0}n_{e}/n_{c}}$$ B ∝ a 0 n e / n c , and further show a close match with previous experimental works. Furthermore, we show in three-dimensional geometry that the decay of the magnetic wake is governed by current filament bending instability, which develops similarly to von Kármán vortex street in its nonlinear stage

Multi-Lane Mirror for Broadband Applications of the Betatron X-ray Source

A new generation of small-scale ultrafast X-ray sources is rapidly emerging. Laser-driven betatron radiation represents an important class of such ultrafast X-ray sources. With the sources driving towards maturity, many important applications in material and biological sciences are expected to be carried out. While the last decade mainly focused on the optimization of the source properties, the development of such sources into user-oriented beamlines in order to explore the potential applications has recently taken off and is expected to grow rapidly. An important aspect in the realization of such beamlines will be the implementation of proper X-ray optics. Here, we present the design of a multi-lane X-ray mirror as a versatile focusing device covering a wide spectral range of betatron X-rays. The expected photon flux in the focal plane of such optics was also estimated through geometrical simulations