Picosecond pump dispersion management and jitter stabilization in a petawatt-scale few-cycle OPCPA system

The petawatt field synthesizer (PFS) is a high-power optical parametric chirped-pulse amplification (OPCPA) system under development, which aims at generating fewcycle pulses with high energies of several Joule. The availability of light pulses with these unique parameters will enable an efficient generation of even shorter attosecond pulses with significantly higher photon flux than achievable today [1]. Not only the real-time observation, but also the control of charge transfer in molecular systems will become feasible for the first time [2]. The technique for realizing the ambitious PFS specifications is short-pulse pumped OPCPA in mm-thin crystals. The reduced crystal thickness allows for ultra-broadband amplification. The pump-pulse duration is reduced to a picosecond—compared to 100 ps to nanosecond pump-pulse duration in conventional high power OPCPA systems. The shortened pulse duration facilitates higher pump intensities whereby an efficient amplification in the mm-thin crystals is achieved. The demonstration of this novel scheme in the PFS project will allow its use in the extreme light infrastructure (ELI)[3]—a pan-European high-power laser project. Based on the PFS technology for the front end, the ELI will generate exawatt peakpower pulses and therefore facilitate the study of laser-matter interaction in an unprecedented intensity range [4]. This work describes the CPA-aspects of a suitable chirped pulse amplification (CPA) pump laser for the PFS OPCPA system. The diode-pumped Yb:YAG amplifiers up to an energy of 300 mJ (at 1030 nm) are presented in combination with the dispersion management. The application of spectral-amplitude shaping in conjunction with an Yb:glass amplifier with broader bandwidth than Yb:YAG enables an unprecedented bandwidth of 3.5nm in the Yb:YAG amplifier at this energy level. Simulations show that a similar bandwidth can be maintained for the full amplifier system. The pulses with 200 mJ could be compressed to 900 fs, close to the transform limit. Later changes in the stretcher increase the bandwidth more and compression down to 740 fs is demonstrated. To date, these are the highest peak power pulses generated in Yb:YAG. For the application as OPCPA pump, the so generated pulses are frequency doubled in a DKDP crystal. Another key aspect of this work is the synchronization of the OPCPA pump and signal pulses. In spite of optical synchronization of both pulses, a large timing fluctuation between these pulses is measured at the first OPCPA stage. The high accuracy jitter measurement setup and a series of measurements, which showed that the stretcher/compressor setup is the main source of jitter, are presented. Theoretical investigations yield that the optical delay in a compressor is orders of magnitude more sensitive to angle changes compared to free space propagation. This makes the stretcher and compressor extremely sensitive for timing jitter caused by turbulent air or mechanical instabilities. This novel insight helped us to significantly reduce the jitter to 100 fs and to demonstrate the feasibility of the PFS concept with first broad-band OPCPA experiments.Das PFS OPCPA System befindet sich zurzeit im Aufbau und zielt darauf ab, ultrakurze Lichtpulse mit wenigen optischen Zyklen und einigen Joule Pulsenergie zu erzeugen. Wenn Lichtpulse mit diesen einzigartigen Parametern verfügbar werden, können kürzere Attosekundenpulse mit höherer Effizienz und deutlich höherem Photonenfluss als bisher generiert werden [1]. Die Anwendung der so erzeugten Attosekundenpulse könnte erstmalig die Beobachtung in Echtzeit und die Kontrolle von Ladungsübergängen in Molekularen Systemen ermöglichen [2]. Die Technik, um die PFS Spezifikationen zu erreichen ist OPCPA mit mm dünnen Kristallen, gepumpt mit kurzen Pulsen. Die reduzierte Kristalldicke ermöglicht ultra-breitbandige Verstärkung. Die Pumppulsdauer ist dabei auf eine Pikosekunde reduziert, im Vergleich zu 100 ps bis Nanosekunden Pulsdauer in konventionellen Hochleistungs-OPCPA Systemen. Dies ermöglicht höhere Pumpintensitäten, wodurch eine effiziente Verstärkung in den kurzen Kristallen gewährleistet wird. Die Demonstration dieses neuartigen Verstärkungsschemas innerhalb des PFS Projektes erlaubt dessen Nutzung in ELI[3]—einem gesamt-europäische Laser Projekt. Basierend auf der PFS-Technologie für das Frontend wird ELI Lichtpulse mit Exawatt Spitzenleistung generieren, wodurch Laser-Materie-Wechselwirkung in einem bis dahin unerreichten Intensitätsbereich untersucht werden kann [4]. Diese Arbeit beschreibt die Entwicklung eines geeigneten CPA Pumplasers für das PFS OPCPA-System. Die diodengepumpten YB:YAG Verstärker bis zu einer Energie von 300 mJ (bei 1030 nm) werden in Kombination mit dem Dispersionsmanagement präsentiert. Die Anwendung von spektralem Amplitudenformen in Verbindung mit einem breitbandigen Verstärker ermöglicht eine bis dahin unerreichte Bandbreite von 3.5nm in Yb:YAG bei diesem Energieniveau. Simulationen zeigen, dass ähnliche Bandbreiten für das vollständige Verstärkersystem erreicht werden können. Die Pulse mit 200 mJ wurden auf 900 fs (nah am Transformlimit) komprimiert. Spätere Veränderungen im Strecker führen zu einer vergrößerten Bandbreite, wodurch eine Kompression auf 740 fs ermöglicht wurde. Aktuell ist dies die höchste Pulsspitzenleistung, die je in Yb:YAG generiert wurde. Für die Anwendung als OPCPA Pumpe werden die so generierten Pulse in einem DKDP Kristall frequenzverdoppelt. Ein weiterer Schwerpunkt dieser Arbeit ist die Synchronisation der OPCPA Pumpund Signalpulse. Trotz optischer Synchronisation beider Pulse wurde eine große zeitliche Schwankung zwischen diesen Pulsen am Ort der ersten OPCPA Stufe gemessen. Der Messaufbau wird vorgestellt und eine Reihe von Messungen zeigt, dass der Strecker/Kompressor des Pumplasers die Hauptursache der zeitlichen Schwankungen von einigen hundert Femtosekunden ist. Theoretische Untersuchungen ergeben, dass der Strecker und Kompressor extrem sensitiv sind für zeitliche Schwankungen, die durch Turbulenzen in Luft oder durch instabile mechanische Komponenten hervorgerufen werden können. Diese neue Einsicht hat geholfen, diese Schwankungen auf 100 fs zu reduzieren und die Machbarkeit des PFS Konzeptes mit ersten breitbandigen OPCPA Experimenten zu demonstrieren

Forms of knowledge and eco-innovation modes: Evidence from Spanish manufacturing firms

The paper investigates the knowledge drivers of firms' eco-innovations (EI) by retaining the diverse nature of their target. Different internal and external knowledge sources are examined and the evidence of EI-modes is searched for with respect to a sample of Spanish manufacturing firms covering the 2007–2009 and 2010–2012 periods. An “attenuated” Science, Technology, EI-mode prevails internally, with R&D more pivotal than either embodied or disembodied non-R&D knowledge, depending on the EI strategy. Externally, synthetic knowledge matters more than the analytical one, suggesting instead a Doing, Using, Interacting EI-mode. Hence, a dichotomic combination of the two modes emerges across the firm's boundaries. However, remarkable differences are in place, depending on whether EIs target efficiency or non-efficiency related environmental improvements. Our evidence also shows that internal and external knowledge turn out difficult to combine, both within and across modes

Differential cross section measurements for the production of a W boson in association with jets in proton–proton collisions at √s = 7 TeV

Measurements are reported of differential cross sections for the production of a W boson, which decays into a muon and a neutrino, in association with jets, as a function of several variables, including the transverse momenta (pT) and pseudorapidities of the four leading jets, the scalar sum of jet transverse momenta (HT), and the difference in azimuthal angle between the directions of each jet and the muon. The data sample of pp collisions at a centre-of-mass energy of 7 TeV was collected with the CMS detector at the LHC and corresponds to an integrated luminosity of 5.0 fb[superscript −1]. The measured cross sections are compared to predictions from Monte Carlo generators, MadGraph + pythia and sherpa, and to next-to-leading-order calculations from BlackHat + sherpa. The differential cross sections are found to be in agreement with the predictions, apart from the pT distributions of the leading jets at high pT values, the distributions of the HT at high-HT and low jet multiplicity, and the distribution of the difference in azimuthal angle between the leading jet and the muon at low values.United States. Dept. of EnergyNational Science Foundation (U.S.)Alfred P. Sloan Foundatio

Search for stop and higgsino production using diphoton Higgs boson decays

Results are presented of a search for a "natural" supersymmetry scenario with gauge mediated symmetry breaking. It is assumed that only the supersymmetric partners of the top-quark (stop) and the Higgs boson (higgsino) are accessible. Events are examined in which there are two photons forming a Higgs boson candidate, and at least two b-quark jets. In 19.7 inverse femtobarns of proton-proton collision data at sqrt(s) = 8 TeV, recorded in the CMS experiment, no evidence of a signal is found and lower limits at the 95% confidence level are set, excluding the stop mass below 360 to 410 GeV, depending on the higgsino mass

Juxtaposing BTE and ATE – on the role of the European insurance industry in funding civil litigation

One of the ways in which legal services are financed, and indeed shaped, is through private insurance arrangement. Two contrasting types of legal expenses insurance contracts (LEI) seem to dominate in Europe: before the event (BTE) and after the event (ATE) legal expenses insurance. Notwithstanding institutional differences between different legal systems, BTE and ATE insurance arrangements may be instrumental if government policy is geared towards strengthening a market-oriented system of financing access to justice for individuals and business. At the same time, emphasizing the role of a private industry as a keeper of the gates to justice raises issues of accountability and transparency, not readily reconcilable with demands of competition. Moreover, multiple actors (clients, lawyers, courts, insurers) are involved, causing behavioural dynamics which are not easily predicted or influenced. Against this background, this paper looks into BTE and ATE arrangements by analysing the particularities of BTE and ATE arrangements currently available in some European jurisdictions and by painting a picture of their respective markets and legal contexts. This allows for some reflection on the performance of BTE and ATE providers as both financiers and keepers. Two issues emerge from the analysis that are worthy of some further reflection. Firstly, there is the problematic long-term sustainability of some ATE products. Secondly, the challenges faced by policymakers that would like to nudge consumers into voluntarily taking out BTE LEI

Penilaian Kinerja Keuangan Koperasi di Kabupaten Pelalawan

This paper describe development and financial performance of cooperative in District Pelalawan among 2007 - 2008. Studies on primary and secondary cooperative in 12 sub-districts. Method in this stady use performance measuring of productivity, efficiency, growth, liquidity, and solvability of cooperative. Productivity of cooperative in Pelalawan was highly but efficiency still low. Profit and income were highly, even liquidity of cooperative very high, and solvability was good

Search for vector-like T quarks decaying to top quarks and Higgs bosons in the all-hadronic channel using jet substructure

Peer reviewe

Impacts of the Tropical Pacific/Indian Oceans on the Seasonal Cycle of the West African Monsoon

The current consensus is that drought has developed in the Sahel during the second half of the twentieth century as a result of remote effects of oceanic anomalies amplified by local land–atmosphere interactions. This paper focuses on the impacts of oceanic anomalies upon West African climate and specifically aims to identify those from SST anomalies in the Pacific/Indian Oceans during spring and summer seasons, when they were significant. Idealized sensitivity experiments are performed with four atmospheric general circulation models (AGCMs). The prescribed SST patterns used in the AGCMs are based on the leading mode of covariability between SST anomalies over the Pacific/Indian Oceans and summer rainfall over West Africa. The results show that such oceanic anomalies in the Pacific/Indian Ocean lead to a northward shift of an anomalous dry belt from the Gulf of Guinea to the Sahel as the season advances. In the Sahel, the magnitude of rainfall anomalies is comparable to that obtained by other authors using SST anomalies confined to the proximity of the Atlantic Ocean. The mechanism connecting the Pacific/Indian SST anomalies with West African rainfall has a strong seasonal cycle. In spring (May and June), anomalous subsidence develops over both the Maritime Continent and the equatorial Atlantic in response to the enhanced equatorial heating. Precipitation increases over continental West Africa in association with stronger zonal convergence of moisture. In addition, precipitation decreases over the Gulf of Guinea. During the monsoon peak (July and August), the SST anomalies move westward over the equatorial Pacific and the two regions where subsidence occurred earlier in the seasons merge over West Africa. The monsoon weakens and rainfall decreases over the Sahel, especially in August.Peer reviewe

Severe early onset preeclampsia: short and long term clinical, psychosocial and biochemical aspects

Preeclampsia is a pregnancy specific disorder commonly defined as de novo hypertension and proteinuria after 20 weeks gestational age. It occurs in approximately 3-5% of pregnancies and it is still a major cause of both foetal and maternal morbidity and mortality worldwide1. As extensive research has not yet elucidated the aetiology of preeclampsia, there are no rational preventive or therapeutic interventions available. The only rational treatment is delivery, which benefits the mother but is not in the interest of the foetus, if remote from term. Early onset preeclampsia (<32 weeks’ gestational age) occurs in less than 1% of pregnancies. It is, however often associated with maternal morbidity as the risk of progression to severe maternal disease is inversely related with gestational age at onset2. Resulting prematurity is therefore the main cause of neonatal mortality and morbidity in patients with severe preeclampsia3. Although the discussion is ongoing, perinatal survival is suggested to be increased in patients with preterm preeclampsia by expectant, non-interventional management. This temporising treatment option to lengthen pregnancy includes the use of antihypertensive medication to control hypertension, magnesium sulphate to prevent eclampsia and corticosteroids to enhance foetal lung maturity4. With optimal maternal haemodynamic status and reassuring foetal condition this results on average in an extension of 2 weeks. Prolongation of these pregnancies is a great challenge for clinicians to balance between potential maternal risks on one the eve hand and possible foetal benefits on the other. Clinical controversies regarding prolongation of preterm preeclamptic pregnancies still exist – also taking into account that preeclampsia is the leading cause of maternal mortality in the Netherlands5 - a debate which is even more pronounced in very preterm pregnancies with questionable foetal viability6-9. Do maternal risks of prolongation of these very early pregnancies outweigh the chances of neonatal survival? Counselling of women with very early onset preeclampsia not only comprises of knowledge of the outcome of those particular pregnancies, but also knowledge of outcomes of future pregnancies of these women is of major clinical importance. This thesis opens with a review of the literature on identifiable risk factors of preeclampsia

Search for the production of dark matter in association with top-quark pairs in the single-lepton final state in proton-proton collisions at √s=8 TeV

Peer reviewe