Synchrotron Radiation Sources driven by Laser-Plasma Accelaerators

Diese Arbeit stellt ein neues Verfahren zur Erzeugung von Synchrotronstrahlung vor. Dabei werden die Elektronenpulse, die beim Durchgang durch einen Undulator Synchrotronstrahlung erzeugen, mit einem Laser-Plasma-Beschleuniger anstatt mit einem konventionellen Beschleuniger erzeugt. Laser-Plasma-Beschleuniger beruhen auf der Wechselwirkung von hochintensiven Laserpulsen mit Plasmen. Ein markanter Vorteil gegenüber den üblichen Hochfrequenzbeschleunigern ist die deutliche Verkürzung der Beschleunigungsstrecke auf typischerweise einige Millimeter. Allerdings ist die Wechselwirkung nichtlinear, wodurch die Eigenschaften der Elektronenpulse schwer zu kontrollieren sind. In Experimenten wurde der Prozess untersucht und deutlich verbessert. Insbesondere wurden ringförmige Magnetfelder von einigen Mega-Gauss, die die Elektronen begleiten, während der Beschleunigung detektiert. Dadurch gelang es zum ersten Mal, in den Beschleunigungsprozess sowohl mit hoher räumlicher als auch hoher zeitlicher Auflösung hineinzublicken. Weitere Diagnostiken gestatteten ein kontrolliertes Einstellen der Wechselwirkungsparameter. Dadurch gelang es, die zur Erzeugung von Synchrotronstrahlung nötigen hochenergetischen und gebündelten Elektronenstrahlen mit hoher Stabilität und Wiederholbarkeit zu erzeugen. Die vorgestellten Experimente beweisen zunächst das Prinzip der Methode, die erzeugten Wellenlängen waren im Wesentlichen durch die verfügbaren Elektronenenergien begrenzt. Jedoch gestatten gegenwärtige Entwicklungen im Gebiet der Laser-Teilchen-Beschleunigung die Erzeugung kurzwelliger Synchrotronstrahlung bis in den Röntgenbereich in naher Zukunft. Darüber hinaus scheinen die ultrakurzen Elektronenpulse für den FEL-Betrieb geeignet zu sein, und die inhärente Synchronisierung mit einem Kurzpuls-Lasersystem kann genaueste zeitaufgelöste Untersuchungen ermöglichen. Insofern stellt das präsentierte Verfahren die Grundlage für einen neuen Typ Laser-basierter Strahlungsquellen dar

I-BEAT: New ultrasonic method for single bunch measurement of ion energy distribution

The shape of a wave carries all information about the spatial and temporal structure of its source, given that the medium and its properties are known. Most modern imaging methods seek to utilize this nature of waves originating from Huygens' principle. We discuss the retrieval of the complete kinetic energy distribution from the acoustic trace that is recorded when a short ion bunch deposits its energy in water. This novel method, which we refer to as Ion-Bunch Energy Acoustic Tracing (I-BEAT), is a generalization of the ionoacoustic approach. Featuring compactness, simple operation, indestructibility and high dynamic ranges in energy and intensity, I-BEAT is a promising approach to meet the needs of petawatt-class laser-based ion accelerators. With its capability of completely monitoring a single, focused proton bunch with prompt readout it, is expected to have particular impact for experiments and applications using ultrashort ion bunches in high flux regimes. We demonstrate its functionality using it with two laser-driven ion sources for quantitative determination of the kinetic energy distribution of single, focused proton bunches.Comment: Paper: 17 Pages, 3 figures Supplementary Material 16 pages, 7 figure

Efficient laser-driven proton acceleration from cylindrical and planar cryogenic hydrogen jets.

We report on recent experimental results deploying a continuous cryogenic hydrogen jet as a debris-free, renewable laser-driven source of pure proton beams generated at the 150 TW ultrashort pulse laser Draco. Efficient proton acceleration reaching cut-off energies of up to 20 MeV with particle numbers exceeding 109 particles per MeV per steradian is demonstrated, showing for the first time that the acceleration performance is comparable to solid foil targets with thicknesses in the micrometer range. Two different target geometries are presented and their proton beam deliverance characterized: cylindrical (∅ 5 μm) and planar (20 μm × 2 μm). In both cases typical Target Normal Sheath Acceleration emission patterns with exponential proton energy spectra are detected. Significantly higher proton numbers in laser-forward direction are observed when deploying the planar jet as compared to the cylindrical jet case. This is confirmed by two-dimensional Particle-in-Cell (2D3V PIC) simulations, which demonstrate that the planar jet proves favorable as its geometry leads to more optimized acceleration conditions

Optimizing laser coupling, matter heating, and particle acceleration from solids using multiplexed ultraintense lasers

Realizing the full potential of ultrahigh-intensity lasers for particle and radiation generation will require multi-beam arrangements due to technology limitations. Here, we investigate how to optimize their coupling with solid targets. Experimentally, we show that overlapping two intense lasers in a mirror-like configuration onto a solid with a large preplasma can greatly improve the generation of hot electrons at the target front and ion acceleration at the target backside. The underlying mechanisms are analyzed through multidimensional particle-in-cell simulations, revealing that the self-induced magnetic fields driven by the two laser beams at the target front are susceptible to reconnection, which is one possible mechanism to boost electron energization. In addition, the resistive magnetic field generated during the transport of the hot electrons in the target bulk tends to improve their collimation. Our simulations also indicate that such effects can be further enhanced by overlapping more than two laser beams

Spectral and spatial shaping of laser-driven proton beams using a pulsed high-field magnet beamline

Intense laser-driven proton pulses, inherently broadband and highly divergent, pose a challenge to established beamline concepts on the path to application-adapted irradiation field formation, particularly for 3D. Here we experimentally show the successful implementation of a highly efficient (50% transmission) and tuneable dual pulsed solenoid setup to generate a homogeneous (8.5% uniformity laterally and in depth) volumetric dose distribution (cylindrical volume of 5 mm diameter and depth) at a single pulse dose of 0.7 Gy via multi-energy slice selection from the broad input spectrum. The experiments have been conducted at the Petawatt beam of the Dresden Laser Acceleration Source Draco and were aided by a predictive simulation model verified by proton transport studies. With the characterised beamline we investigated manipulation and matching of lateral and depth dose profiles to various desired applications and targets. Using a specifically adapted dose profile, we successfully performed first proof-of-concept laser-driven proton irradiation studies of volumetric in-vivo normal tissue (zebrafish embryos) and in-vitro tumour tissue (SAS spheroids) samples.Comment: Submitted to Scientific Report

I-BEAT: Ultrasonic method for online measurement of the energy distribution of a single ion bunch

The shape of a wave carries all information about the spatial and temporal structure of its source, given that the medium and its properties are known. Most modern imaging methods seek to utilize this nature of waves originating from Huygens' principle. We discuss the retrieval of the complete kinetic energy distribution from the acoustic trace that is recorded when a short ion bunch deposits its energy in water. This novel method, which we refer to as Ion-Bunch Energy Acoustic Tracing (I-BEAT), is a refinement of the ionoacoustic approach. With its capability of completely monitoring a single, focused proton bunch with prompt readout and high repetition rate, I-BEAT is a promising approach to meet future requirements of experiments and applications in the field of laser-based ion acceleration. We demonstrate its functionality at two laser-driven ion sources for quantitative online determination of the kinetic energy distribution in the focus of single proton bunches