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1.
  • Adrian-Martinez, S., et al. (författare)
  • A first search for coincident gravitational waves and high energy neutrinos using LIGO, Virgo and ANTARES data from 2007
  • 2013
  • Ingår i: Journal of Cosmology and Astroparticle Physics. - : IOP Publishing. - 1475-7516. ; :6
  • Tidskriftsartikel (refereegranskat)abstract
    • We present the results of the first search for gravitational wave bursts associated with high energy neutrinos. Together, these messengers could reveal new, hidden sources that are not observed by conventional photon astronomy, particularly at high energy. Our search uses neutrinos detected by the underwater neutrino telescope ANTARES in its 5 line configuration during the period January - September 2007, which coincided with the fifth and first science runs of LIGO and Virgo, respectively. The LIGO-Virgo data were analysed for candidate gravitational-wave signals coincident in time and direction with the neutrino events. No significant coincident events were observed. We place limits on the density of joint high energy neutrino - gravitational wave emission events in the local universe, and compare them with densities of merger and core-collapse events.
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2.
  • Evans, P. A., et al. (författare)
  • Swift Follow-up Observations of Candidate Gravitational-wave Transient Events
  • 2012
  • Ingår i: The Astrophysical Journal Supplement Series. - : American Astronomical Society. - 0067-0049 .- 1538-4365. ; 203:2
  • Tidskriftsartikel (refereegranskat)abstract
    • We present the first multi-wavelength follow-up observations of two candidate gravitational-wave (GW) transient events recorded by LIGO and Virgo in their 2009-2010 science run. The events were selected with low latency by the network of GW detectors (within less than 10 minutes) and their candidate sky locations were observed by the Swift observatory (within 12 hr). Image transient detection was used to analyze the collected electromagnetic data, which were found to be consistent with background. Off-line analysis of the GW data alone has also established that the selected GW events show no evidence of an astrophysical origin; one of them is consistent with background and the other one was a test, part of a "blind injection challenge." With this work we demonstrate the feasibility of rapid follow-ups of GW transients and establish the sensitivity improvement joint electromagnetic and GW observations could bring. This is a first step toward an electromagnetic follow-up program in the regime of routine detections with the advanced GW instruments expected within this decade. In that regime, multi-wavelength observations will play a significant role in completing the astrophysical identification of GW sources. We present the methods and results from this first combined analysis and discuss its implications in terms of sensitivity for the present and future instruments.
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3.
  • Aasi, J., et al. (författare)
  • Einstein@Home all-sky search for periodic gravitational waves in LIGO S5 data
  • 2013
  • Ingår i: Physical Review D (Particles, Fields, Gravitation and Cosmology). - 1550-2368. ; 87:4
  • Tidskriftsartikel (refereegranskat)abstract
    • This paper presents results of an all-sky search for periodic gravitational waves in the frequency range [50, 1190] Hz and with frequency derivative range of similar to[-20, 1.1] x 10(-10) Hz s(-1) for the fifth LIGO science run (S5). The search uses a noncoherent Hough-transform method to combine the information from coherent searches on time scales of about one day. Because these searches are very computationally intensive, they have been carried out with the Einstein@Home volunteer distributed computing project. Postprocessing identifies eight candidate signals; deeper follow-up studies rule them out. Hence, since no gravitational wave signals have been found, we report upper limits on the intrinsic gravitational wave strain amplitude h(0). For example, in the 0.5 Hz-wide band at 152.5 Hz, we can exclude the presence of signals with h(0) greater than 7.6 x 10(-25) at a 90% confidence level. This search is about a factor 3 more sensitive than the previous Einstein@Home search of early S5 LIGO data.
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4.
  • Aasi, J., et al. (författare)
  • Parameter estimation for compact binary coalescence signals with the first generation gravitational-wave detector network
  • 2013
  • Ingår i: Physical Review D (Particles, Fields, Gravitation and Cosmology). - 1550-2368. ; 88:6
  • Tidskriftsartikel (refereegranskat)abstract
    • Compact binary systems with neutron stars or black holes are one of the most promising sources for ground-based gravitational-wave detectors. Gravitational radiation encodes rich information about source physics; thus parameter estimation and model selection are crucial analysis steps for any detection candidate events. Detailed models of the anticipated waveforms enable inference on several parameters, such as component masses, spins, sky location and distance, that are essential for new astrophysical studies of these sources. However, accurate measurements of these parameters and discrimination of models describing the underlying physics are complicated by artifacts in the data, uncertainties in the waveform models and in the calibration of the detectors. Here we report such measurements on a selection of simulated signals added either in hardware or software to the data collected by the two LIGO instruments and the Virgo detector during their most recent joint science run, including a "blind injection'' where the signal was not initially revealed to the collaboration. We exemplify the ability to extract information about the source physics on signals that cover the neutron-star and black-hole binary parameter space over the component mass range 1M(circle dot)-25M(circle dot) and the full range of spin parameters. The cases reported in this study provide a snapshot of the status of parameter estimation in preparation for the operation of advanced detectors.
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5.
  • Aasi, J., et al. (författare)
  • Search for gravitational waves from binary black hole inspiral, merger, and ringdown in LIGO-Virgo data from 2009-2010
  • 2013
  • Ingår i: Physical Review D (Particles, Fields, Gravitation and Cosmology). - 1550-2368. ; 87:2
  • Tidskriftsartikel (refereegranskat)abstract
    • We report a search for gravitational waves from the inspiral, merger and ringdown of binary black holes (BBH) with total mass between 25 and 100 solar masses, in data taken at the LIGO and Virgo observatories between July 7, 2009 and October 20, 2010. The maximum sensitive distance of the detectors over this period for a (20, 20)M-circle dot coalescence was 300 Mpc. No gravitational wave signals were found. We thus report upper limits on the astrophysical coalescence rates of BBH as a function of the component masses for nonspinning components, and also evaluate the dependence of the search sensitivity on component spins aligned with the orbital angular momentum. We find an upper limit at 90% confidence on the coalescence rate of BBH with nonspinning components of mass between 19 and 28M(circle dot) of 3:3 x 10(-7) mergers Mpc(-3) yr(-1).
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6.
  • Aasi, J., et al. (författare)
  • The characterization of Virgo data and its impact on gravitational-wave searches
  • 2012
  • Ingår i: Classical and Quantum Gravity. - : IOP Publishing. - 1361-6382 .- 0264-9381. ; 29:15
  • Tidskriftsartikel (refereegranskat)abstract
    • Between 2007 and 2010 Virgo collected data in coincidence with the LIGO and GEO gravitational-wave (GW) detectors. These data have been searched for GWs emitted by cataclysmic phenomena in the universe, by non-axisymmetric rotating neutron stars or from a stochastic background in the frequency band of the detectors. The sensitivity of GW searches is limited by noise produced by the detector or its environment. It is therefore crucial to characterize the various noise sources in a GW detector. This paper reviews the Virgo detector noise sources, noise propagation, and conversion mechanisms which were identified in the three first Virgo observing runs. In many cases, these investigations allowed us to mitigate noise sources in the detector, or to selectively flag noise events and discard them from the data. We present examples from the joint LIGO-GEO-Virgo GW searches to show how well noise transients and narrow spectral lines have been identified and excluded from the Virgo data. We also discuss how detector characterization can improve the astrophysical reach of GW searches.
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7.
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8.
  • Abdalla, E., et al. (författare)
  • Cosmology intertwined : A review of the particle physics, astrophysics, and cosmology associated with the cosmological tensions and anomalies
  • 2022
  • Ingår i: Journal of High Energy Astrophysics. - : Elsevier BV. - 2214-4048 .- 2214-4056. ; 34, s. 49-211
  • Tidskriftsartikel (refereegranskat)abstract
    • The standard Λ Cold Dark Matter (ΛCDM) cosmological model provides a good description of a wide range of astrophysical and cosmological data. However, there are a few big open questions that make the standard model look like an approximation to a more realistic scenario yet to be found. In this paper, we list a few important goals that need to be addressed in the next decade, taking into account the current discordances between the different cosmological probes, such as the disagreement in the value of the Hubble constant H0, the σ8–S8 tension, and other less statistically significant anomalies. While these discordances can still be in part the result of systematic errors, their persistence after several years of accurate analysis strongly hints at cracks in the standard cosmological scenario and the necessity for new physics or generalisations beyond the standard model. In this paper, we focus on the 5.0σ tension between the Planck CMB estimate of the Hubble constant H0 and the SH0ES collaboration measurements. After showing the H0 evaluations made from different teams using different methods and geometric calibrations, we list a few interesting new physics models that could alleviate this tension and discuss how the next decade's experiments will be crucial. Moreover, we focus on the tension of the Planck CMB data with weak lensing measurements and redshift surveys, about the value of the matter energy density Ωm, and the amplitude or rate of the growth of structure (σ8,fσ8). We list a few interesting models proposed for alleviating this tension, and we discuss the importance of trying to fit a full array of data with a single model and not just one parameter at a time. Additionally, we present a wide range of other less discussed anomalies at a statistical significance level lower than the H0–S8 tensions which may also constitute hints towards new physics, and we discuss possible generic theoretical approaches that can collectively explain the non-standard nature of these signals. Finally, we give an overview of upgraded experiments and next-generation space missions and facilities on Earth that will be of crucial importance to address all these open questions. 
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9.
  • Alcorn, J, et al. (författare)
  • Basic instrumentation for Hall A at Jefferson Lab
  • 2004
  • Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - : Elsevier BV. - 0167-5087 .- 0168-9002. ; 522:3, s. 294-346
  • Tidskriftsartikel (refereegranskat)abstract
    • The instrumentation in Hall A at the Thomas Jefferson National Accelerator Facility was designed to study electro-and photo-induced reactions at very high luminosity and good momentum and angular resolution for at least one of the reaction products. The central components of Hall A are two identical high resolution spectrometers, which allow the vertical drift chambers in the focal plane to provide a momentum resolution of better than 2 x 10(-4). A variety of Cherenkov counters, scintillators and lead-glass calorimeters provide excellent particle identification. The facility has been operated successfully at a luminosity well in excess of 10(38) CM-2 s(-1). The research program is aimed at a variety of subjects, including nucleon structure functions, nucleon form factors and properties of the nuclear medium. (C) 2003 Elsevier B.V. All rights reserved.
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10.
  • Carré, B., et al. (författare)
  • Characterization of attosecond pulse trains
  • 2007
  • Ingår i: Ultrafast Optics V. - New York, NY : Springer New York. - 1556-1534 .- 0342-4111. - 9780387491172 ; 132, s. 45-56
  • Konferensbidrag (refereegranskat)abstract
    • Ultrashort light pulses, as short as 100 as, can be produced from high harmonic generation (HHG) in an atomic gas medium. This major achievement of the last 6 years in high field physics has now been demonstrated in different conditions of medium-field interaction [1].
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11.
  • Fages, A., et al. (författare)
  • Tracking Five Millennia of Horse Management with Extensive Ancient Genome Time Series
  • 2019
  • Ingår i: Cell. - : Elsevier BV. - 0092-8674. ; 177:6
  • Tidskriftsartikel (refereegranskat)abstract
    • Horse domestication revolutionized warfare and accelerated travel, trade, and the geographic expansion of languages. Here, we present the largest DNA time series for a non-human organism to date, including genome-scale data from 149 ancient animals and 129 ancient genomes (>= 1-fold coverage), 87 of which are new. This extensive dataset allows us to assess the modem legacy of past equestrian civilisations. We find that two extinct horse lineages existed during early domestication, one at the far western (Iberia) and the other at the far eastern range (Siberia) of Eurasia. None of these contributed significantly to modern diversity. We show that the influence of Persian-related horse lineages increased following the Islamic conquests in Europe and Asia. Multiple alleles associated with elite-racing, including at the MSTN "speed gene," only rose in popularity within the last millennium. Finally, the development of modem breeding impacted genetic diversity more dramatically than the previous millennia of human management.
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12.
  • Arnold, C. L., et al. (författare)
  • The ELI-ALPS secondary sources : A getaway to scientific excellence
  • 2013
  • Ingår i: 2013 Conference on Lasers and Electro-Optics, CLEO 2013. - 9781557529725 ; 2013
  • Konferensbidrag (refereegranskat)abstract
    • The essence of ELI-ALPS, the laser driven secondary sources ranging from X-ray and X-UV to THz with duration as short as tens of attoseconds, are designed to be available for users from 2016.
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13.
  • Greer, M., et al. (författare)
  • Lung transplantation after allogeneic stem cell transplantation: a pan-European experience
  • 2018
  • Ingår i: European Respiratory Journal. - : European Respiratory Society (ERS). - 0903-1936 .- 1399-3003. ; 51:2
  • Tidskriftsartikel (refereegranskat)abstract
    • Late-onset noninfectious pulmonary complications (LONIPCs) affect 6% of allogeneic stem cell transplantation (SCT) recipients within 5 years, conferring subsequent 5-year survival of 50%. Lung transplantation is rarely performed in this setting due to concomitant extrapulmonary morbidity, excessive immunosuppression and concerns about recurring malignancy being considered contraindications. This study assesses survival in highly selected patients undergoing lung transplantation for LONIPCs after SCT. SCT patients undergoing lung transplantation at 20 European centres between 1996 and 2014 were included. Clinical data pre- and post-lung transplantation were reviewed. Propensity score-matched controls were generated from the Eurotransplant and Scandiatransplant registries. Kaplan-Meier survival analysis and Cox proportional hazard regression models evaluating predictors of graft loss were performed. Graft survival at 1, 3 and 5 years of 84%, 72% and 67%, respectively, among the 105 SCT patients proved comparable to controls (p=0.75). Sepsis accounted for 15 out of 37 deaths (41%), with prior mechanical ventilation (HR 6.9, 95% CI 1.0-46.7; p<0.001) the leading risk factor. No SCT-specific risk factors were identified. Recurring malignancy occurred in four patients (4%). Lung transplantation <2 years post-SCT increased all-cause 1-year mortality (HR 7.5, 95% CI 2.3-23.8; p=0.001). Lung transplantation outcomes following SCT were comparable to other end-stage diseases. Lung transplantation should be considered feasible in selected candidates. No SCT-specific factors influencing outcome were identified within this carefully selected patient cohort.
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14.
  • Varju, Katalin, et al. (författare)
  • Reconstruction of attosecond pulse trains using an adiabatic phase expansion
  • 2005
  • Ingår i: Physical Review Letters. - 1079-7114. ; 95:24
  • Tidskriftsartikel (refereegranskat)abstract
    • We propose a new method to reconstruct the electric field of attosecond pulse trains. The phase of the high-order harmonic emission electric field is Taylor expanded around the maximum of the laser pulse envelope in the time domain and around the central harmonic in the frequency domain. Experimental measurements allow us to determine the coefficients of this expansion and to characterize the radiation with attosecond accuracy over a femtosecond time scale. The method gives access to pulse-to-pulse variations along the train, including the timing, the chirp, and the attosecond carrier envelope phase.
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15.
  • Bastard, P, et al. (författare)
  • Vaccine breakthrough hypoxemic COVID-19 pneumonia in patients with auto-Abs neutralizing type I IFNs
  • 2023
  • Ingår i: Science immunology. - : American Association for the Advancement of Science (AAAS). - 2470-9468. ; 8:90, s. eabp8966-
  • Tidskriftsartikel (refereegranskat)abstract
    • Life-threatening ‘breakthrough’ cases of critical COVID-19 are attributed to poor or waning antibody response to the SARS-CoV-2 vaccine in individuals already at risk. Pre-existing autoantibodies (auto-Abs) neutralizing type I IFNs underlie at least 15% of critical COVID-19 pneumonia cases in unvaccinated individuals; however, their contribution to hypoxemic breakthrough cases in vaccinated people remains unknown. Here, we studied a cohort of 48 individuals (age 20-86 years) who received 2 doses of an mRNA vaccine and developed a breakthrough infection with hypoxemic COVID-19 pneumonia 2 weeks to 4 months later. Antibody levels to the vaccine, neutralization of the virus, and auto-Abs to type I IFNs were measured in the plasma. Forty-two individuals had no known deficiency of B cell immunity and a normal antibody response to the vaccine. Among them, ten (24%) had auto-Abs neutralizing type I IFNs (aged 43-86 years). Eight of these ten patients had auto-Abs neutralizing both IFN-α2 and IFN-ω, while two neutralized IFN-ω only. No patient neutralized IFN-β. Seven neutralized 10 ng/mL of type I IFNs, and three 100 pg/mL only. Seven patients neutralized SARS-CoV-2 D614G and the Delta variant (B.1.617.2) efficiently, while one patient neutralized Delta slightly less efficiently. Two of the three patients neutralizing only 100 pg/mL of type I IFNs neutralized both D61G and Delta less efficiently. Despite two mRNA vaccine inoculations and the presence of circulating antibodies capable of neutralizing SARS-CoV-2, auto-Abs neutralizing type I IFNs may underlie a significant proportion of hypoxemic COVID-19 pneumonia cases, highlighting the importance of this particularly vulnerable population.
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16.
  • Hergott, JF, et al. (författare)
  • XUV interferometry using high-order harmonics: Application to plasma diagnostics
  • 2001
  • Ingår i: Laser and Particle Beams. - 0263-0346. ; 19:1, s. 35-40
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper, we present and compare the two different XUV interferometric techniques using high-order harmonics that have been developed so far. The first scheme is based on the interference between two spatially separated phase-locked harmonic sources while the second uses two temporally separated harmonic sources. These techniques have been applied to plasma diagnostics in feasibility experiments where electron densities up to a few 1020 e[minus sign/cm3 have been measured with a temporal resolution of 200 fs. We present the main characteristics of each technique and discuss their respective potentials and limitations.
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17.
  • Kovacev, M, et al. (författare)
  • Extreme ultraviolet fourier-transform spectroscopy with high order harmonics
  • 2005
  • Ingår i: Physical Review Letters. - 1079-7114. ; 95:22
  • Tidskriftsartikel (refereegranskat)abstract
    • We demonstrate a new scheme for extreme ultraviolet (xuv) Fourier-transform spectroscopy based on the generation of two phase-locked high-harmonic beams. It allows us to measure for the first time interferograms at wavelengths as short as 90 nm, and open the perspective of performing high-resolution Fourier-transform absorption spectroscopy in the xuv. Our measurements also demonstrate that a precise control of the relative phase of harmonic pulses can be obtained with an accuracy on an attosecond time scale, of importance for future xuv pump-xuv probe attosecond spectroscopy.
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18.
  • Kovács, K, et al. (författare)
  • Multi-parameter optimization of a loose focusing high flux high-harmonic beamline
  • 2019
  • Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 52:5, s. 055402-055402
  • Tidskriftsartikel (refereegranskat)abstract
    • We perform a multi-dimensional parameter scan in the generation of high-order harmonics, with the main purpose to find the macroscopic conditions that optimize the harmonic yield in a specific spectral domain, around 40 eV for this particular case. The scanned parameters are the laser pulse energy, gas pressure, interaction cell position relative to focus and the cell length, while the fixed parameters are chosen to model a loose focusing configuration which is used in many existing laboratories. We performed the simulations with a 3D non-adiabatic model complemented by a detailed analysis of the phase matching mechanisms involved in an efficient harmonic generation. Based on the results we identify a range of parameter combinations that lead to a high yield in the specified spectral domain. The method and results presented here can be the framework for the design and construction of high flux high-order harmonic generation beamlines.
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19.
  • L'Huillier, Anne, et al. (författare)
  • High-order Harmonics - A Coherent Source In the Xuv Range
  • 1995
  • Ingår i: Journal of Nonlinear Optical Physics & Materials. - 0218-1991. ; 4:3, s. 647-665
  • Tidskriftsartikel (refereegranskat)abstract
    • We review the main results concerning high-order generation processes from the point of view of a potential user of this new source of XUV radiation. The perspectives for optimizing the source, both in efficiency and in spectral range, its characteristics and in particular, its coherence properties, are discussed. Finally, we describe two experiments, which demonstrate the usefulness of the harmonics as a short-pulse, coherent source in the XUV domain.
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20.
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21.
  • Antoine, P, et al. (författare)
  • Generation of attosecond pulses in macroscopic media
  • 1997
  • Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 56:6, s. 4960-4969
  • Tidskriftsartikel (refereegranskat)abstract
    • We describe theoretically the generation of ultrashort (subfemtosecond) pulses using high-order harmonics of a laser pulse with a time-dependent degree of ellipticity. The single-atom response is calculated by using a low-frequency strong-field approximation. Propagation effects are taken into account using a method going beyond the slowly varying envelope approximation. Propagation modifies significantly the results obtained in the single-atom response and, in certain conditions, makes the generation of one attosecond pulse possible. We discuss prospects for the observation of these ultrashort pulses. [S1050-2947(97)09411-0].
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22.
  • Antoine, P, et al. (författare)
  • Theory of high-order harmonic generation by an elliptically polarized laser field
  • 1996
  • Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 53:3, s. 1725-1745
  • Tidskriftsartikel (refereegranskat)abstract
    • We generalize a recently formulated theory of high-order harmonic generation by low-frequency laser fields [Anne L'Huillier et al., Phys. Rev. A 48, R3433 (1993)] to the case of an elliptically polarized light. Our theoretical description includes both the single-atom response and propagation. Phase matching significantly modifies the results obtained in the single-atom response. The results of our calculations, including propagation for both the intensity and polarization properties of harmonics as a function of laser ellipticity, compare very well with recent experimental observations.
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23.
  • Cacciani, P, et al. (författare)
  • Lifetime measurements of the E (1)Pi, upsilon=0 and upsilon=1 states of (CO)-C-12-O-16, (CO)-C-13-O-16, and (CO)-C-13-O-18
  • 1998
  • Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X. ; 499
  • Tidskriftsartikel (refereegranskat)abstract
    • In a laboratory investigation using tunable picosecond lasers in a pump-probe configuration, lifetimes of the E (II)-I-1, v = O and v = 1 states of CO are experimentally determined. For E (II)-I-1, v = 1, the lifetime is found to vary significantly for the isotopomers. Combining the data with existing oscillator strengths, predissociation probabilities within the range of 93.6%-98.64% result for (CO)-C-12-O-16, (CO)-C-13-O-16, and (CO)-C-13-O-18 in, the case of the E (II)-I-1, v=1 state, which is the state that predominantly influences the isotopic fractionation of CO in interstellar clouds.
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24.
  • Cacciani, P., et al. (författare)
  • Lifetime measurements of the e1II, v = 0 and v = 1 states of12C16O, 13C16O, and13C18O
  • 1998
  • Ingår i: Astrophysical Journal. - 0004-637X. ; 499:2 PART II, s. 223-226
  • Tidskriftsartikel (refereegranskat)abstract
    • In a laboratory investigation using tunable picosecond lasers in a pump-probe configuration, lifetimes of the E 1u, v = 0 and v = 1 states of CO are experimentally determined. For E 'D, v = 1, the lifetime is found to vary significantly for the isotopomers. Combining the data with existing oscillator strengths, predissociation probabilities within the range of 93.6%-98.6% result for 12C16O, 13C16O, and 13C18O in the case of the E 1u, v = I state, which is the state that predominantly influences the isotopic fractionation of CO in interstellar clouds.
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25.
  • Campi, F., et al. (författare)
  • The high intensity HHG beamline at lund laser
  • 2014
  • Ingår i: High Intensity Lasers and High Field Phenomena, HILAS 2014. - 9781557529954
  • Konferensbidrag (refereegranskat)abstract
    • We will present the new Lund HHG beamline designed for high photon flux, delivering pulse energies of more than 4 μJ per pulse in the spectral range from 20 eV to 45 eV. Focused XUV intensities above 1014 W/cm2 should become possible.
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26.
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27.
  • Heyl, C. M., et al. (författare)
  • High-average power high-harmonic and attosecond sources : Status and prospects
  • 2016
  • Ingår i: Compact EUV and X-ray Light Sources, EUVXRAY 2016. - 9781943580095 ; Part F14-EUVXRAY 2016
  • Konferensbidrag (refereegranskat)abstract
    • Experiments employing extreme ultraviolet sources based on high harmonic generation often suffer from photon flux limitations. We discuss current status and prospects for scaling such sources to higher repetition rate, pulse energy and average power.
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28.
  • Heyl, C. M., et al. (författare)
  • Noncollinear optical gating - A method for intra-cavity single attosecond pulse generation?
  • 2019
  • Ingår i: Proceedings 2015 European Conference on Lasers and Electro-Optics - European Quantum Electronics Conference, CLEO/Europe-EQEC 2015. - 9781467374750
  • Konferensbidrag (refereegranskat)abstract
    • The process of high-order harmonic generation requires laser intensities around 1014 W/cm2, most easily reached with laser pulses of high energy, thus implicitly limiting the repetition rate of attosecond sources. A route towards multi-MHz attosecond sources relies on HHG inside a passive enhancement cavity [1]. Although successfully demonstrated for attosecond pulse trains, the generation of single attosecond pulses (SAPs) inside a cavity remains an unsolved challenge, mainly limited by dispersion management and out-coupling problems. We recently proposed a new gating concept for SAP generation [2], noncollinear optical gating (NOG) which has the potential to facilitate SAP gating and efficient out-coupling at once. Similar to the recently introduced attosecond lighthouse [3] NOG employs attosecond angular streaking [4] and combines this concept with noncollinear HHG, proposed earlier [5] as out-coupling method for intra cavity HHG.
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29.
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30.
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31.
  • Johnsson, Per, et al. (författare)
  • Attosecond electron wave packet dynamics in strong laser fields
  • 2005
  • Ingår i: Physical Review Letters. - 1079-7114. ; 95:1, s. 1-013001
  • Tidskriftsartikel (refereegranskat)abstract
    • We use a train of sub-200 attosecond extreme ultraviolet (XUV) pulses with energies just above the ionization threshold in argon to create a train of temporally localized electron wave packets. We study the energy transfer from a strong infrared (IR) laser field to the ionized electrons as a function of the delay between the XUV and IR fields. When the wave packets are born at the zero crossings of the IR field, a significant amount of energy (similar to 20 eV) is transferred from the field to the electrons. This results in dramatically enhanced above-threshold ionization in conditions where the IR field alone does not induce any significant ionization. Because both the energy and duration of the wave packets can be varied independently of the IR laser, they are valuable tools for studying and controlling strong-field processes.
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32.
  • L'Huillier, Anne, et al. (författare)
  • High-order Harmonic-generation Cutoff
  • 1993
  • Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 48:5
  • Tidskriftsartikel (refereegranskat)abstract
    • We have experimentally determined the harmonic-generation cutoff as a function of the laser intensity in neon using an intense, short-pulse Ti:sapphire laser. The experimental cutoff is lower than that obtained in single-atom calculations. Using a simple quantum-mechanical approach to harmonic generation valid at high intensity, we show that the difference is due to the effect of propagation.
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33.
  • Major, B., et al. (författare)
  • Macroscopic Optimization of High Harmonic Generation for High Power Laser Pulses
  • 2016
  • Ingår i: High Intensity Lasers and High Field Phenomena, HILAS 2016. - 9781943580095 ; Part F15-HILAS 2016
  • Konferensbidrag (refereegranskat)abstract
    • We study upscaling of gas high harmonic generation, to make efficient use of the ever increasing laser pulse powers. Loose focusing geometries optimizing phasematching are investigated and compared in HHG efficiency to shorter focusing arrangements.
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34.
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35.
  • Makos, I, et al. (författare)
  • Α 10-gigawatt attosecond source for non-linear XUV optics and XUV-pump-XUV-probe studies
  • 2020
  • Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 10:1
  • Tidskriftsartikel (refereegranskat)abstract
    • The quantum mechanical motion of electrons and nuclei in systems spatially confined to the molecular dimensions occurs on the sub-femtosecond to the femtosecond timescales respectively. Consequently, the study of ultrafast electronic and, in specific cases, nuclear dynamics requires the availability of light pulses with attosecond (asec) duration and of sufficient intensity to induce two-photon processes, essential for probing the intrinsic system dynamics. The majority of atoms, molecules and solids absorb in the extreme-ultraviolet (XUV) spectral region, in which the synthesis of the required attosecond pulses is feasible. Therefore, the XUV spectral region optimally serves the study of such ultrafast phenomena. Here, we present a detailed review of the first 10-GW class XUV attosecond source based on laser driven high harmonic generation in rare gases. The pulse energy of this source largely exceeds other laser driven attosecond sources and is comparable to the pulse energy of femtosecond Free-Electron-Laser (FEL) XUV sources. The measured pulse duration in the attosecond pulse train is 650 ± 80 asec. The uniqueness of the combined high intensity and short pulse duration of the source is evidenced in non-linear XUV-optics experiments. It further advances the implementation of XUV-pump-XUV-probe experiments and enables the investigation of strong field effects in the XUV spectral region.
  •  
36.
  • Manschwetus, B., et al. (författare)
  • Two-photon double ionization of neon studied with intense attosecond pulse trains
  • 2016
  • Ingår i: International Conference on Ultrafast Phenomena, UP 2016. - 9781943580187 ; Part F20-UP 2016
  • Konferensbidrag (refereegranskat)abstract
    • We focused an intense attosecond pulse train into a neon gas target and observed Ne2+ resulting from two-photon double ionization. By modifying the photon spectrum we find that the process is dominated by the sequential ionization via the Ne+ ion.
  •  
37.
  • Manschwetus, B., et al. (författare)
  • Two-photon double ionization of neon using an intense attosecond pulse train
  • 2016
  • Ingår i: Physical Review A. - : American Physical Society (APS). - 2469-9926 .- 2469-9934. ; 93:6
  • Tidskriftsartikel (refereegranskat)abstract
    • We present a demonstration of two-photon double ionization of neon using an intense extreme ultraviolet (XUV) attosecond pulse train (APT) in a photon energy regime where both direct and sequential mechanisms are allowed. For an APT generated through high-order harmonic generation (HHG) in argon we achieve a total pulse energy close to 1μJ, a central energy of 35 eV, and a total bandwidth of ∼30 eV. The APT is focused by broadband optics in a neon gas target to an intensity of 3×1012Wcm−2. By tuning the photon energy across the threshold for the sequential process the double ionization signal can be turned on and off, indicating that the two-photon double ionization predominantly occurs through a sequential process. The demonstrated performance opens up possibilities for future XUV-XUV pump-probe experiments with attosecond temporal resolution in a photon energy range where it is possible to unravel the dynamics behind direct versus sequential double ionization and the associated electron correlation effects.
  •  
38.
  • Morlens, AS, et al. (författare)
  • Design and characterization of extreme-ultraviolet broadband mirrors for attosecond science
  • 2006
  • Ingår i: Optics Letters. - 0146-9592. ; 31:10, s. 1558-1560
  • Tidskriftsartikel (refereegranskat)abstract
    • A novel multilayer mirror was designed and fabricated based on a recently developed three-material technology aimed both at reaching reflectivities of about 20% and at controlling dispersion over a bandwidth covering photon energies between 35 and 50 eV. The spectral phase upon reflection was retrieved by measuring interferences in a two-color ionization process using high-order harmonics produced from a titanium: sapphire laser. We demonstrate the feasibility of designing and characterizing phase-controlled broadband optics in the extreme-ultraviolet domain, which should facilitate the manipulation of attosecond pulses for applications.
  •  
39.
  • Neidel, Ch, et al. (författare)
  • Probing Time-Dependent Molecular Dipoles on the Attosecond Time Scale
  • 2013
  • Ingår i: Physical Review Letters. - 1079-7114. ; 111:3
  • Tidskriftsartikel (refereegranskat)abstract
    • Photoinduced molecular processes start with the interaction of the instantaneous electric field of the incident light with the electronic degrees of freedom. This early attosecond electronic motion impacts the fate of the photoinduced reactions. We report the first observation of attosecond time scale electron dynamics in a series of small-and medium-sized neutral molecules (N-2, CO2, and C2H4), monitoring time-dependent variations of the parent molecular ion yield in the ionization by an attosecond pulse, and thereby probing the time-dependent dipole induced by a moderately strong near-infrared laser field. This approach can be generalized to other molecular species and may be regarded as a first example of molecular attosecond Stark spectroscopy.
  •  
40.
  • Puckett, A. J. R., et al. (författare)
  • Final analysis of proton form factor ratio data at Q(2)=4.0, 4.8, and 5.6 GeV2
  • 2012
  • Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 85:4
  • Tidskriftsartikel (refereegranskat)abstract
    • Precise measurements of the proton electromagnetic form factor ratio R = mu(p)G(E)(p)/G(M)(p) using the polarization transfer method at Jefferson Lab have revolutionized the understanding of nucleon structure by revealing the strong decrease of R with momentum transfer Q(2) for Q(2) greater than or similar to 1 GeV2, in strong disagreement with previous extractions of R from cross-section measurements. In particular, the polarization transfer results have exposed the limits of applicability of the one-photon-exchange approximation and highlighted the role of quark orbital angular momentum in the nucleon structure. The GEp-II experiment in Jefferson Lab's Hall A measured R at four Q(2) values in the range 3.5 GeV2 <= Q(2) <= 5.6 GeV2. A possible discrepancy between the originally published GEp-II results and more recent measurements at higher Q(2) motivated a new analysis of the GEp-II data. This article presents the final results of the GEp-II experiment, including details of the new analysis, an expanded description of the apparatus, and an overview of theoretical progress since the original publication. The key result of the final analysis is a systematic increase in the results for R, improving the consistency of the polarization transfer data in the high-Q(2) region. This increase is the result of an improved selection of elastic events which largely removes the systematic effect of the inelastic contamination, underestimated by the original analysis.
  •  
41.
  • Skantzakis, E., et al. (författare)
  • Non-linear Extreme Ultraviolet Applications with Attosecond Pulses
  • 2024
  • Ingår i: Topics in Applied Physics. - 1437-0859 .- 0303-4216. - 9783031554629 - 9783031554636 ; 151, s. 1-24
  • Bokkapitel (refereegranskat)abstract
    • In recent years laser driven attosecond sourcesAttosecond sources based on loose geometry high order harmonic generationHigh order harmonic generation reach focused intensities as high as to induce multi-photonMulti-photonmultiple ionizationMultiple ionization or even strong -field effectsEven strong-field effects in the extreme ultraviolet spectral range. In this chapter, we review four such sources developed through collaborative efforts between FORTH, ELI-ALPS and the University of Lund together with recent results obtained in the above mentioned topics utilizing these sources.
  •  
42.
  • Svanberg, Sune, et al. (författare)
  • Applications of terawatt lasers
  • 1994
  • Ingår i: LASER SPECTROSCOPY - XITH INTERNATIONAL CONFERENCE. - : AIP. - 1551-7616 .- 0094-243X. - 1563962624 ; :290, s. 264-269
  • Konferensbidrag (refereegranskat)
  •  
43.
  • Varju, Katalin, et al. (författare)
  • Frequency chirp of harmonic and attosecond pulses
  • 2005
  • Ingår i: Journal of Modern Optics. - : Informa UK Limited. - 0950-0340 .- 1362-3044. ; 52:2-3, s. 379-394
  • Tidskriftsartikel (refereegranskat)abstract
    • We study the phase of the atomic polarization in the process of high-order harmonic generation. Its dependence on the laser intensity and the harmonic order induce a frequency variation in time (chirp) respectively of the harmonic pulses and attosecond pulses. We review the recent experimental results on the temporal characterization of the harmonic emission and show that measurements performed using very different techniques (like XFROG and RABITT), probing the phase in different parameter spaces, can be connected through the mixed phase derivatives, demonstrating the common underlying physics
  •  
44.
  • Veyrinas, K., et al. (författare)
  • Chromatic aberrations correction of attosecond high-order harmonic beams by flat-top spatial shaping of the fundamental beam
  • 2023
  • Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 25:2
  • Tidskriftsartikel (refereegranskat)abstract
    • Attosecond pulses created by high-order harmonic generation in gases often exhibit strong chromatic aberrations, arising from the broad bandwidth and wavelength-dependent nonlinear light-matter interaction. When the driving laser intensity varies spatially, as for Gaussian driving beams, the apparent source position of the harmonics differs significantly from one order to the next, thus affecting the achievable intensity and duration of the attosecond pulses when they are focused on a target. We show that these chromatic aberrations can be reduced by spatially shaping the fundamental beam to generate high-order harmonics with a driver having a flat-top profile inside the gas medium. By measuring both the intensity profile and wavefront for each harmonic in a plane, we access the extreme ultra-violet (XUV) beam properties and investigate these properties near focus. We observe that controlling chromatic aberrations by flat-top spatial shaping strongly reduces the variation of the XUV spectrum on the beam axis during propagation and, in return, the longitudinal sensitivity of both the temporal profiles and the temporal shifts of the focused attosecond pulses.
  •  
45.
  • Veyrinas, K., et al. (författare)
  • High order harmonic generation with spatially shaped flat top driver to control XUV chromatic aberrations
  • 2023
  • Ingår i: 2023 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2023. - 9798350345995
  • Konferensbidrag (refereegranskat)abstract
    • The XUV beams generated via high order harmonic generation (HHG) in gases have spatial properties evolving with the harmonic order. It leads to chromatic aberrations when the harmonics are focussed so that, locally, the spectral content can change significantly during propagation [1-3] especially near focus.
  •  
46.
  • Wahlström, Claes-Göran, et al. (författare)
  • High-order Harmonic-generation In Rare-gases With An Intense Short-pulse Laser
  • 1993
  • Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 48:6, s. 4709-4720
  • Tidskriftsartikel (refereegranskat)abstract
    • We present experimental studies of high-order harmonic generation in the rare gases performed with a short-pulse titanium sapphire laser operating at 794 nm in the 10(14)-10(15) W/cm2 range. The harmonic yields generated in neon and in argon are studied for all orders as a function of the laser intensity. They vary first rather steeply, in the cutoff region, then much more slowly in the plateau region, and, finally, they saturate when the medium gets ionized. The dependence of the high-order harmonic cutoff with the laser intensity in neon and argon is found to be lower than that predicted in single-atom theories. We observe high-order harmonics in argon and xenon (up to the 65th and 45th, respectively) at 10(15) W/cm2, which we attribute to harmonic generation from ions. We also show how the harmonic and fundamental spectra get blueshifted when the medium becomes ionized.
  •  
47.
  • Alexandridi, C., et al. (författare)
  • Attosecond photoionization dynamics in the vicinity of the Cooper minima in argon
  • 2021
  • Ingår i: Physical Review Research. - 2643-1564. ; 3:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Using a spectrally resolved electron interferometry technique, we measure photoionization time delays between the 3s and 3p subshells of argon over a large 34-eV energy range covering the Cooper minima in both subshells. The observed strong variations of the 3s−3p delay difference, including a sign change, are well reproduced by theoretical calculations using the two-photon two-color random-phase approximation with exchange. Strong shake-up channels lead to photoelectrons spectrally overlapping with those emitted from the 3s subshell. These channels need to be included in our analysis to reproduce the experimental data. Our measurements provide a benchmark for multielectronic theoretical models aiming at an accurate description of interchannel correlation.
  •  
48.
  • Antoine, P, et al. (författare)
  • Attosecond pulse trains using high-order harmonics
  • 1996
  • Ingår i: Physical Review Letters. - 1079-7114. ; 77:7, s. 1234-1237
  • Tidskriftsartikel (refereegranskat)abstract
    • We demonstrate that high-order harmonics generated by an atom in intense laser field form trains of ultrashort pulses corresponding to different trajectories of electrons that tunnel out of the atom and recombine. Propagation in an atomic jet allows us to select one of these trajectories, leading to a train of pulses of extremely short duration.
  •  
49.
  • Antoine, P, et al. (författare)
  • Polarization of high-order harmonics
  • 1997
  • Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 55:2, s. 1314-1324
  • Tidskriftsartikel (refereegranskat)abstract
    • We report measurements and calculations of the polarization state of high-order harmonics generated by a 790-nm Ti:sapphire laser. The problem of completely characterizing the polarization state of a partially polarized radiation in the XUV range is discussed in detail. The comparison between several gases, xenon, argon and neon, and different orders, from the 17th to the 33rd, shows that the rotation angle and ellipticity strongly depends on the position of the harmonic in the spectrum, and in particular, whether it is in the cutoff or in the plateau. In the plateau, the rotation angle is quite large, and the ellipticity follows that of the fundamental, remaining, however, smaller. The radiation is only partially polarized. In contrast, in the cutoff, both rotation angle and ellipticity remain small, independently of the laser ellipticity. Our experimental results compare well with theoretical predictions including the single-atom response and propagation effects.
  •  
50.
  • Appi, E., et al. (författare)
  • Two phase-matching regimes in high-order harmonic generation
  • 2023
  • Ingår i: Optics Express. - 1094-4087. ; 31:20, s. 31687-31697
  • Tidskriftsartikel (refereegranskat)abstract
    • High-order harmonic generation (HHG) provides scalable sources of coherent extreme ultraviolet radiation with pulse duration down to the attosecond time scale. Efficient HHG requires the constructive interplay between microscopic and macroscopic effects in the generation volume, which can be achieved over a large range of experimental parameters from the driving field properties to those of the generating medium. Here, we present a systematic study of the harmonic yield as a function of gas pressure and medium length. Two regimes for optimum yield are identified, supporting the predictions of a recently proposed analytical model. Our observations are independent on the focusing geometry and, to a large extent, on the pulse duration and laser intensity, providing a versatile approach to HHG optimization.
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