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High power Laser Science and Engineering 2024年第1期12卷 116-116页

作者： J.Goodman M.King E.J.Dolier R.Wilson R.J.Gray p.mckenna 不详

Due to an isolated error in the 3D simulation parameters,the laser energy and intensity(calculated using the energy)values were incorrectly stated as 10.9 J and 3×10^(22) W cm^(−2),respectively,in Sections 3.3,7 and *** correct values are 39.8 J and 1.1×10^(23) W cm^(−2).Similarly,the values stated for the higher energy case,109 J and 3×10^(23) W cm^(−2) in Section 7,should be 398 J and 1.1×10^(24) W cm^(−2),respectively.

关键词： Bayesian optimization gamma rays laser-solid interactions machine learning radiation reaction

Effects of monoculture-conditioned soils on common tallgrass prairie species productivity

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Journal of plant Ecology 2019年第3期12卷 474-484页

作者： Thomas p.mckenna Brian J.Darby Kathryn A.Yurkonis Kansas Biological Survey University of Kansas2101 Constant Ave.Takeru Higuchi HallLawrenceKS 66047USA Department of Biology University of North Dakota10 Cornell Street Stop 9019Grand ForksND 58202USA

Aims Within biodiversity-ecosystem function experiments,it is widely understood that yields of some species rapidly decline when planted in *** effect may arise due to decreased access to soil nutrients or an increase in detrimental soil patho-gens within monoculture *** determine whether or not soil conditioning affects tall grass prairie species biomass produc-tion,we conducted a field experiment to assess species growth in conspecifically and heterospecifically conditioned soils and a greenhouse experiment to elucidate how conspecific soil biota affected species *** To test for species-specific soil effects,seedlings of the legume Astragulus canadensis,the cool-season grass Elymus canaden-sis,the forb Helianthus maximiliani and the warm-season grass panicum virgatum were grown in field plots that had either been conspecifically or heterospecifically conditioned over 2 *** growth was recorded over a single growing season,and soils were assessed for differences in their nematode(mesofauna)*** of these species were additionally grown over a 6-week period in conspecifically conditioned soil that was either untreated,heated to 60°C,sterilized(autoclaved at 120°C)or heated to 60°C and reinoculated with conspecific soil *** two heating treatments were used to compare growth responses between a low-and high-temperature soil *** reinoculation treatment was used to assess the effect of soil biota in light of any nutrient changes that may have occurred with soil *** Findings Elymus canadensis,*** and *** growth was improved in field plots conditioned by the legume *** com-pared with their growth in conspecifically conditioned(home)*** variation(grass versus nongrass)in their soil nematode com-munities,there was no evidence to suggest that these three species were inhibited by conspecific or functionally conspecific soil condi-tioning in the ***

关键词： Astragulus canadensis diversity Elymus canadensis Helianthus maximiliani monoculture overyielding panicum virgatum productivity soil biota soil conditioning

Optimization and control of synchrotron emission in ultraintense laser–solid interactions using machine learning

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高功率激光科学与工程:英文版 2023年第3期11卷 15-31页

作者： J.Goodman M.King E.J.Dolier R.Wilson R.J.Gray p.mckenna SUpA Department of physics University of StrathclydeGlasgowUK The Cockcroft Institute Sci-Tech DaresburyWarringtonUK

The optimum parameters for the generation of synchrotron radiation in ultraintense laser pulse interactions with planar foils are investigated with the application of Bayesian optimization,via Gaussian process regression,to 2D particle-incell *** properties of the synchrotron emission,such as the yield,are maximized,and simultaneous mitigation of bremsstrahlung emission is achieved with multi-variate objective *** angle-of-incidence of the laser pulse onto the target is shown to strongly influence the synchrotron yield and angular profile,with oblique incidence producing the optimal *** is further explored in 3D simulations,in which additional control of the spatial profile of synchrotron emission is demonstrated by varying the polarization of the laser *** results demonstrate the utility of applying a machine learning-based optimization approach and provide new insights into the physics of radiation generation in laser-foil interactions,which will inform the design of experiments in the quantum electrodynamics(QED)-plasma regime.

关键词： Bayesian optimization gamma rays laser-solid interactions machine learning radiation reaction

High order modes of intense second harmonic light produced from a plasma aperture

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Matter and Radiation at Extremes 2022年第5期7卷 7-16页

作者： E.F.J.Bacon M.King R.Wilson T.p.Frazer R.J.Gray p.mckenna SUpA Department of physics University of StrathclydeGlasgow G40NGUnited Kingdom The Cockcroft Institute Sci-Tech DaresburyWarrington WA44ADUnited Kingdom

Because of their ability to sustain extremely high-amplitude electromagnetic fields and transient density and field profiles,plasma optical components are being developed to amplify,compress,and condition high-power laser *** recently demonstrated the potential to use a relativistic plasma aperture—produced during the interaction of a high-power laser pulse with an ultrathin foil target—to tailor the spatiotemporal properties of the intense fundamental and second-harmonic light generated[Duff et al.,***.10,105(2020)].Herein,we explore numerically the interaction of an intense laser pulse with a preformed aperture target to generate second-harmonic laser light with higher-order spatial *** maximum generation efficiency is found for an aperture diameter close to the full width at half maximum of the laser focus and for a micrometer-scale target *** spatial mode generated is shown to depend strongly on the polarization of the drive laser pulse,which enables changing between a linearly polarized TEM01 mode and a circularly polarized Laguerre–Gaussian LG01 *** demonstrates the use of a plasma aperture to generate intense higher-frequency light with selectable spatial mode structure.

关键词： polarization intense harmonic

EMp control and characterization on high-power laser systems

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High power Laser Science and Engineering 2018年第2期6卷 55-62页

作者： p.Bradford N.C.Woolsey G.G.Scott G.Liao H.Liu Y.Zhang B.Zhu C.Armstrong S.Astbury C.Brenner p.Brummitt F.Consoli I.East R.Gray D.Haddock E Huggard E J.R.Jones E.Montgomery I.Musgrave E Oliveira D.R.Rusby C.Spindloe B.Summers E.Zemaityte Z.Zhang Y.Li p.mckenna D.Neely Department of physics York Plasma InstituteUniversity of YorkHeslingtonYork YO10 5DDUK Central Laser Facility STFC Rutherford Appleton LaboratoryDidcot OX110QXUK Key Laboratory for Laser plasmas(Ministry of Education)and School of physics and Astronomy Shanghai Jiao Tong UniversityShanghai 200240China Beijing National Laboratory for Condensed Matter physics Institute of PhysicsChinese Academy of SciencesBeijing 100190China School of physical Sciences University of Chinese Academy of SciencesBeijing 100049China Department of physics SUpA University of StrathclydeGlasgow G40NGUK ENEA-C.R.Frascati-Dipartimento FSN Via E.Fermi 4500044 FrascatiItaly Space Science Department STFC Rutherford Appleton LaboratoryDidcot OX110QXUK

Giant electromagnetic pulses(EMp) generated during the interaction of high-power lasers with solid targets can seriously degrade electrical measurements and equipment. EMp emission is caused by the acceleration of hot electrons inside the target, which produce radiation across a wide band from DC to terahertz frequencies. Improved understanding and control of EMp is vital as we enter a new era of high repetition rate, high intensity lasers(e.g. the Extreme Light Infrastructure).We present recent data from the VULCAN laser facility that demonstrates how EMp can be readily and effectively reduced. Characterization of the EMp was achieved using B-dot and D-dot probes that took measurements for a range of different target and laser parameters. We demonstrate that target stalk geometry, material composition, geodesic path length and foil surface area can all play a significant role in the reduction of EMp. A combination of electromagnetic wave and 3 D particle-in-cell simulations is used to inform our conclusions about the effects of stalk geometry on EMp,providing an opportunity for comparison with existing charge separation models.

关键词： high energy density physics high-power laser related laser components laser plasmas interaction target design and fabrication

Effects of target pre-heating and expansion on terahertz radiation production from intense laser-solid interactions

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High power Laser Science and Engineering 2014年第1期2卷 13-17页

作者： X.H.Yuan Y.Fang D.C.Carroll D.A.MacLellan F.Du N.Booth M.Burza M.Chen R.J.Gray Y.F.Jin Y.T.Li Y.Liu D.Neely H.powell G.Scott C.-G.Wahlstrm J.Zhang p.mckenna Z.M.Sheng Key Laboratory for Laser plasmas (Ministry of Education) and Department of physics and Astronomy Shanghai Jiao Tong University Beijing National Laboratory of Condensed Matter physics Institute of Physics Chinese Academy of Sciences SUpA Department of physics University of Strathclyde Central Laser Facility Rutherford Appleton Laboratory Department of physics Lund University

The first experimental measurements of intense(～7 × 1019 W cm-2) laser-driven terahertz(THz) radiation from a solid target which is preheated by an intense pulse of laser-accelerated protons is reported. The total energy of the THz radiation is found to decrease by approximately a factor of 2 compared to a cold target reference. This is attributed to an increase in the scale length of the preformed plasma, driven by proton heating, at the front surface of the target,where the THz radiation is generated. The results show the importance of controlling the preplasma scale length for THz production.

关键词： target heating terahertz radiation

Effect of rear surface fields on hot, refluxing and escaping electron populations via numerical simulations

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High power Laser Science and Engineering 2019年第3期7卷 76-86页

作者： D.R.Rusby C.D.Armstrong G.G.Scott M.King p.mckenna D.Neely Central Laser Facility STFCRutherford Appleton LaboratoryChiltonDidcot 0X11 OQXUK SUpA Department of PhysicsUniversity of StrathclydeGlasgow G4 ONGUK

After a population of laser-driven hot electrons traverses a limited thickness solid target,these electrons will encounter the rear surface,creating TV/m fields that heavily influence the subsequent hot-electron *** that fail to overcome the electrostatic potential reflux back into the *** electrons that do overcome the field will escape the ***,using the particle-in-cell(pIC)code EpOCH and particle tracking of a large population of macro-particles,we investigate the refluxing and escaping electron populations,as well as the magnitude,spatial and temporal evolution of the rear surface electrostatic *** temperature of both the escaping and refluxing electrons is reduced by 30%–50%when compared to the initial hot-electron temperature as a function of intensity between 1019 and 1021 W/cm^*** particle tracking we conclude that the highest energy internal hot electrons are guaranteed to escape up to a threshold energy,below which only a small fraction are able to escape the *** also examine the temporal characteristic of energy changes of the refluxing and escaping electrons and show that the majority of the energy change is as a result of the temporally evolving electric field that forms on the rear surface.

关键词： electron transport high power laser particle-in-cell simulations

Reflection of intense laser light from microstructured targets as a potential diagnostic of laser focus and plasma temperature

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High power Laser Science and Engineering 2019年第1期7卷 10-16页

作者： J.Jarrett M.King R.J.Gray N.Neumann L.Dhl C.D.Baird T.Ebert M.Hesse A.Tebartz D.R.Rusby N.C.Woolsey D.Neely M.Roth p.mckenna Department of physics SUpA University of Strathclyde Institut f¨ur Kernphysik Technische Universit?t Darmstadt York plasma Institute University of York STFC-Rutherford Appleton Laboratory Institut fur Kernphysik Technische Universit?t Darmstadt

The spatial-intensity profile of light reflected during the interaction of an intense laser pulse with a microstructured target is investigated experimentally and the potential to apply this as a diagnostic of the interaction physics is explored numerically. Diffraction and speckle patterns are measured in the specularly reflected light in the cases of targets with regular groove and needle-like structures, respectively, highlighting the potential to use this as a diagnostic of the evolving plasma surface. It is shown, via ray-tracing and numerical modelling, that for a laser focal spot diameter smaller than the periodicity of the target structure, the reflected light patterns can potentially be used to diagnose the degree of plasma expansion, and by extension the local plasma temperature, at the focus of the intense laser light. The reflected patterns could also be used to diagnose the size of the laser focal spot during a high-intensity interaction when using a regular structure with known spacing.

关键词： high power laser laser-solid interactions plasma temperature diagnosis

Bremsstrahlung emission from high power laser interactions with constrained targets for industrial radiography

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High power Laser Science and Engineering 2019年第2期7卷 27-33页

作者： C.D.Armstrong C.M.Brenner C.Jones D.R.Rusby Z.E.Davidson Y.Zhang J.Wragg S.Richards C.Spindloe p.Oliveira M.Notley R.Clarke S.R.Mirfayzi S.Kar Y.Li T.Scott p.mckenna D.Neely Department of physics SUpA University of StrathclydeGlasgow G4ONGUK Central Laser Facility STFC Rutherford Appleton LaboratoryHarwellOxford0X11OQXUK Interface Analysis Centre HH Wills Physics LaboratoryTyndall AvenueBristol BS81TLUK Beijing National Laboratory for Condensed Matter physics Institute of PhysicsChinese Academy of SciencesBeijing100190China Centre for plasma physics Queen's University BelfastBelfast BT7INNUK

Laser-solid interactions are highly suited as a potential source of high energy X-rays for nondestructive imaging.A bright,energetic X-ray pulse can be driven from a small source,making it ideal for high resolution X-ray *** limiting the lateral dimensions of the target we are able to confine the region over which X-rays are produced,enabling imaging with enhanced resolution and *** constrained targets we demonstrate experimentally a(20±3)μm X-ray source,improving the image quality compared to unconstrained foil *** demonstrates that a larger sheath field envelope around the perimeter of the constrained targets increases the proportion of electron current that recirculates through the target,driving a brighter source of X-rays.

关键词： bremsstrahlung high power laser nondestructive imaging radiography X-ray

Optimization of a laser plasma-based x-ray source according to WDM absorption spectroscopy requirements

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Matter and Radiation at Extremes 2021年第1期6卷 37-44页

作者： A.S.Martynenko S.A.pikuz I.Yu.Skobelev S.N.Ryazantsev C.D.Baird N.Booth L.N.K.Dohl p.Durey A.Ya.Faenov D.Farley R.Kodama K.Lancaster p.mckenna C.D.Murphy C.Spindloe T.A.pikuz N.Woolsey Joint Institute for High Temperatures of the Russian Academy of Sciences 125412 MoscowRussia National Research Nuclear University MEphI Kashirskoe Sh.31115409 MoscowRussia York plasma Institute Department of PhysicsUniversity of YorkYork YO105DDUnited Kingdom Central Laser Facility STFC Rutherford Appleton LaboratoryDidcot OX110QXUnited Kingdom Open and Transdisciplinary Research Initiative Osaka UniversityOsaka 565-0871Japan Institute of Laser Engineering Osaka UniversitySuita 565-0871Japan Department of physics SUPAUniversity of StrathclydeGlasgow G40NGUnited Kingdom

X-ray absorption spectroscopy is a well-accepted diagnostic for experimental studies of warm dense *** requires a short-lived X-ray source of sufficiently high emissivity and without characteristic lines in the spectral range of *** the present work,we discuss how to choose an optimum material and thickness to get a bright source in the wavelength range 2A–6A(∼2 keV to 6 keV)by considering relatively low-Z *** demonstrate that the highest emissivity of solid aluminum and silicon foil targets irradiated with a 1-ps high-contrast sub-kJ laser pulse is achieved when the target thickness is close to 10μ*** outer plastic layer can increase the emissivity even further.

关键词： laser WDM source