Entwicklung eines Doppel-Plasmaspiegels zur Erzeugung hochenergetischer Ionen mit ultra-dünnen Targets

A residence at 131 W. Jackson Street, which includes large cactus in the back, a clothes line, and an aluminum siding panel fence

Laser and electron deflection from transverse asymmetries in laser-plasma accelerators.

We report on the deflection of laser pulses and accelerated electrons in a laser-plasma accelerator (LPA) by the effects of laser pulse front tilt and transverse density gradients. Asymmetry in the plasma index of refraction leads to laser steering, which can be due to a density gradient or spatiotemporal coupling of the laser pulse. The transverse forces from the skewed plasma wave can also lead to electron deflection relative to the laser. Quantitative models are proposed for both the laser and electron steering, which are confirmed by particle-in-cell simulations. Experiments with the BELLA Petawatt Laser are presented which show controllable 0.1-1 mrad laser and electron beam deflection from laser pulse front tilt. This has potential applications for electron beam pointing control, which is of paramount importance for LPA applications

Highly-integrated signal and pump combiner in chirally-coupled-core fibers

Integrated fiber components enable compact and robust laser systems but are usually not available with specialty fibers. However, specialty fibers allow power scaling of fiber lasers and amplifiers with all advantages of these fiber designs. In this context, chirally-coupled-core fibers show promising properties for optical fiber components. In this paper, we present the development of a highly-integrated signal and pump combiner in chirally-core-fibers using a side-pumping technology. Combining up to four fiber-coupled pump diodes, a pump-light limited power handling of 600 W can be achieved with an efficiency of 78%. The combiner was tested in a side-pumped single-frequency all-fiber amplifier but can also be implemented in almost any fiber laser or amplifier

Recent progress on monolithic fiber amplifiers for next generation of gravitational wave detectors

Single-frequency fiber amplifiers in MOPA configuration operating at 1064 nm (Yb3+) and around 1550 nm (Er3+ or Er3+:Yb3+) are promising candidates to fulfill the challenging requirements of laser sources of the next generation of interferometric gravitational wave detectors (GWDs). Most probably, the next generation of GWDs is going to operate not only at 1064 nm but also at 1550 nm to cover a broader range of frequencies in which gravitational waves are detectable. We developed an engineering fiber amplifier prototype at 1064 nm emitting 215 W of linearly-polarized light in the TEM00 mode. The system consists of three modules: the seed source, the pre-amplifier, and the main amplifier. The modular design ensures reliable long-term operation, decreases system complexity and simplifies repairing and maintenance procedures. It also allows for the future integration of upgraded fiber amplifier systems without excessive downtimes. We also developed and characterized a fiber amplifier prototype at around 1550 nm that emits 100 W of linearly-polarized light in the TEM00 mode. This prototype uses an Er3+:Yb3+ codoped fiber that is pumped off-resonant at 940 nm. The off-resonant pumping scheme improves the Yb3+-to-Er3+ energy transfer and prevents excessive generation of Yb3+-ASE

A workshop report on the FDNext project funded by the German Research Foundation

Nach zwei Jahren Projektlaufzeit lud der DFG-geförderte Projektverbund FDNext zu einem zweiten Community-Workshop ein. Unter dem Motto „Nachhaltiges Forschungsdatenmanagement gemeinsam umsetzen“ wurde eine projektweite Ergebnisbilanz gezogen und im Rahmen einer Online-Veranstaltung vorgestellt. Einzelne Formate ermöglichten den Austausch und die Diskussion zur Vision des Kulturwandels und eines ganzheitlichen FDMs durch Initiativen wie die Nationale Forschungsdateninfrastruktur (NFDI) sowie die Möglichkeiten der Zusammenarbeit zwischen einzelnen Konsortien und Hochschulen. Dabei wurden Aufgaben identifiziert, welche nur gemeinsam mit der FDM- bzw. Wissenschafts-Community bearbeitet werden können.Two years into the project duration, the collaborative project FDNext convened its second community workshop titled “Implementing Sustainable Research Data Management in a Joint Project”. Focusing on a review of achievements, the online event presented findings from all participating parties. Various formats fostered exchange and debates about perspectives of cultural change and a holistic research data management through initiatives such as the Nationale Forschungsdateninfrastruktur NFDI (national research data infrastructure), as well as collaboration opportunities between individual consortia and universities. Tasks and challenges that can only be dealt with in cooperation with RDM and scientific communities have been identified.Peer Reviewe

GWTC-1: A Gravitational-Wave Transient Catalog of Compact Binary Mergers Observed by LIGO and Virgo during the First and Second Observing Runs

We present the results from three gravitational-wave searches for coalescing compact binaries with component masses above 1 Ma™ during the first and second observing runs of the advanced gravitational-wave detector network. During the first observing run (O1), from September 12, 2015 to January 19, 2016, gravitational waves from three binary black hole mergers were detected. The second observing run (O2), which ran from November 30, 2016 to August 25, 2017, saw the first detection of gravitational waves from a binary neutron star inspiral, in addition to the observation of gravitational waves from a total of seven binary black hole mergers, four of which we report here for the first time: GW170729, GW170809, GW170818, and GW170823. For all significant gravitational-wave events, we provide estimates of the source properties. The detected binary black holes have total masses between 18.6-0.7+3.2 Mâ™ and 84.4-11.1+15.8 Mâ™ and range in distance between 320-110+120 and 2840-1360+1400 Mpc. No neutron star-black hole mergers were detected. In addition to highly significant gravitational-wave events, we also provide a list of marginal event candidates with an estimated false-alarm rate less than 1 per 30 days. From these results over the first two observing runs, which include approximately one gravitational-wave detection per 15 days of data searched, we infer merger rates at the 90% confidence intervals of 110-3840 Gpc-3 y-1 for binary neutron stars and 9.7-101 Gpc-3 y-1 for binary black holes assuming fixed population distributions and determine a neutron star-black hole merger rate 90% upper limit of 610 Gpc-3 y-1. © 2019 authors. Published by the American Physical Society

Adaptive Radiation within Marine Anisakid Nematodes: A Zoogeographical Modeling of Cosmopolitan, Zoonotic Parasites

Parasites of the nematode genus Anisakis are associated with aquatic organisms. They can be found in a variety of marine hosts including whales, crustaceans, fish and cephalopods and are known to be the cause of the zoonotic disease anisakiasis, a painful inflammation of the gastro-intestinal tract caused by the accidental consumptions of infectious larvae raw or semi-raw fishery products. Since the demand on fish as dietary protein source and the export rates of seafood products in general is rapidly increasing worldwide, the knowledge about the distribution of potential foodborne human pathogens in seafood is of major significance for human health. Studies have provided evidence that a few Anisakis species can cause clinical symptoms in humans. The aim of our study was to interpolate the species range for every described Anisakis species on the basis of the existing occurrence data. We used sequence data of 373 Anisakis larvae from 30 different hosts worldwide and previously published molecular data (n = 584) from 53 field-specific publications to model the species range of Anisakis spp., using a interpolation method that combines aspects of the alpha hull interpolation algorithm as well as the conditional interpolation approach. The results of our approach strongly indicate the existence of species-specific distribution patterns of Anisakis spp. within different climate zones and oceans that are in principle congruent with those of their respective final hosts. Our results support preceding studies that propose anisakid nematodes as useful biological indicators for their final host distribution and abundance as they closely follow the trophic relationships among their successive hosts. The modeling might although be helpful for predicting the likelihood of infection in order to reduce the risk of anisakiasis cases in a given area

Ionenbeschleunigung im Laser-Transparenz Regime

Im Rahmen dieser Arbeit wurden neue, verbesserte Ansätze zur Ionenbeschleunigung mit kurzen, intensiven Laser Pulsen untersucht und charakterisiert. Die verwendeten Laser Pulse mit relativistischer Intensität und sehr hohem Intensitätskontrast ermöglichten die Verwendung von Folien-Targets mit Dicken unterhalb der Eindringtiefe des Laserspulses (~nm) und somit erstmals Experimente im sog transparenten Regime. Im Gegensatz zu undurchsichtigen, dicken Folientargets, erlauben transparente Targets die Teilnahme der gesamten Elektronenpopulation im fokalen Volumen an der Beschleunigung und die Anpassung der Gruppengeschwindigkeiten von Laserfeld, Elektronen und Ionen. Die dargestellten Ergebnisse erweitern das bekannte Bild der „Target Normal Sheath Acceleration (TNSA)“ bei dem die Energie des Lasers an der Vorderseite eines lichtundurchlässiges Festkörpertargets in kinetische Energie von Plasmaelektronen umgewandelt wird. Diese so erzeugten „heißen“ Elektronen breiten sich durch das Target aus und erzeugen ein quasi-statisches elektrisches Feld an der Rückseite, das wiederum die Ionen beschleunigt. Aufgrund der hohen Reflektivität des Lasers und der lateralen Ausbreitung der Elektronen ist hierbei die Konversionseffizienz sehr gering, typischerweise ~1%. Außerdem weist die spektrale Verteilung der beschleunigten Ionen einen exponentiellen Verlauf auf. Mit der Entwicklung eines Doppel-Plasmaspiegels, der den zeitlichen Intensitätskontrast des Laserpulses um ca. vier Größenordnungen erhöht, ohne dabei die Qualität der Wellenfront zu beeinflussen, konnten erstmalig derartige ultra-dünne Folien eingesetzt werden. Der Energiedurchsatz dieses Plasmaspiegelsystems betrug 60-65%. Als Targets dienten „Diamond-Like-Carbon (DLC)“ Folien, die senkrecht, mit linear polarisierten Laserpulsen bestrahlt wurden. Damit konnte eine optimale Ionenbeschleunigung bei einer Dicke von 5.3nm nachgewiesen werden, die zu einer Verdopplung der maximalen Energie der Protonen auf 13MeV, und einer Erhöhung um das 20-fache bei Kohlenstoff Ionen (71MeV) führte, verglichen mit Experimenten an Lasersystemen mit ähnlichen Parametern. Das Auftreten dieses Optimums wird darauf zurückgeführt, dass bei ultra-dünnen Targets die ponderomotive Kraft die der Laserspuls auf die Elektronen ausübt, die elektrostatische Rückstellkraft der ruhenden Ionen übersteigt und somit die Elektronen aus dem Einflussbereich der Ionen entfernt. Bei dickeren Targets ist die ponderomotive Kraft nicht ausreichend, um diese maximale Polarisation zu bewirken. Hierbei wurde auch eine wesentliche Erhöhung der Konversionseffizienz für die Erzeugung von C6+ um zwei Größenordnungen auf 10% erreicht. Allerdings war die energetische Verteilung der Ionen noch geprägt von der exponentiellen Energieverteilung der „heißen“ Elektronen und somit ebenfalls exponentiell. Im Weiteren wurde auch zirkulare Laserpolarisation verwendet, um relativistisches (v x B) - „Heizen“ als dominanten Absorptionsprozess zu unterdrücken. Damit werden die Plasmaelektronen unter den o.g. Optimalbedingungen komprimiert und können somit als Spiegel betrachtet werden, der weniger Impuls zugunsten von mehr Energie gewinnt, wenn er beschleunigt wird. Die Ionenbeschleunigung erfolgt dann in einem mitbewegtem elektrischen Feld und führt intrinsisch zu monoenergetischen Spektren. Diese Lichtdruckbeschleunigung konnte hier erstmals experimentell verifiziert werden, wobei Anzahl und Energie der Elektronen verringert und ein ausgeprägter Peak in der Verteilung der C6+ Ionen um die 30MeV beobachtet wurde. Das zusätzliche Auftreten höherer Harmonischer des einfallenden Lasers gemessen in dessen Ausbreitungsrichtung ermöglicht einen detaillierten Einblick in die Plasmadynamik während des Beschleunigungsprozesses. So konnte die instantane Plasmadichte anhand des spektralen Abbruchs der Harmonischen bestimmt- und auf eine eindimensionale Expansion zurückgeführt werden.In this work novel, approved approaches for the acceleration of ions by short, intense laser pulse are investigated and characterized. The applied laser pulses with relativistic intensities and ultra-high temporal contrast enabled the application of foil targets with thicknesses below the collisionless skin depth of the laser (~nm) and hence the first experiments in the laser transparency regime. In contrast to opaque, thick foils these targets allow the participation of all electrons in the focal volume in the acceleration and a group velocity matching of laser field, electrons and ions. The presented results expand the known picture of Target Normal Sheath Acceleration (TNSA) where the energy of the laser pulse is transferred to kinetic energy of plasma electrons at front side of an opaque, solid target. These “hot electrons” expand throughout the target and induce a quasi-static electric field at the rear side that in turn accelerates the ions. The conversion efficiency of this process is very low due to the high reflectivity of the laser and the lateral spreading of the electrons – typically ~1%. Additionally, the spectral shape of the accelerated ions exhibits an exponential slope. With the help of a Double-Plasma-Mirror (DPM) the temporal contrast of the laser pulse could be enhanced by approximately 4 orders of magnitude, without any distortion of the wave front. In the first place, the DPM allowed the deployment of nm-thin foils. An energy throughput of the system of 60-65% was obtained. Diamond-like-Carbon (DLC) foils with thicknesses down to 2nm were used as targets. They were illuminated with linear polarized laser pulses at normal incidence and an optimum thickness for ion acceleration of 5.3nm was demonstrated. At this optimum thickness, the proton energy was enhanced by a factor of two (13MeV) and in case of carbon ions by a factor of 20 (71MeV) compared to experiments with similar laser parameters, accompanied by a significant enhancement of the conversion efficiency up to values of about 10%. The existence of such an optimum is attributed to a pressure unbalance of the ponderomotive force of the laser and the restoring electrostatic force raised by the ions remaining at rest. If the ponderomotive exceeds the electrostatic force, the electrons are expelled from the sphere of influence of the ions and hence the ion acceleration is less effective. In case of thicker targets, the ponderomotive force is not sufficient to exert the maximum polarization between electrons and ions. However the spectral shape of the ions was still exponential as in imprint of the exponential distribution of the hot electrons. Consequently, in the following circular polarization was used to suppress (v x B) – heating as the dominant laser absorption process. According to that, the plasma electrons are compressed and can be regarded as a mirror that gains more energy in favour of less momentum if accelerated. Then the ion acceleration occurs in a co-moving electrical field and intrinsically leads to a mono-energetic spectrum. This dominant acceleration by the laser radiation pressure could be experimentally demonstrated for the first time. The number and energy of accelerated electrons could be reduced and a distinct peak in the carbon spectrum was obtained centred around 30MeV. Furthermore, the harmonic radiation of the incident laser was measured giving a detailed insight into the plasma dynamics during the acceleration. This allowed the determination of the instantaneous plasma density by the spectral cut-off the harmonics which could be ascribed to one dimensional plasma expansion