If Michelson were to answer the question posed in the title, given the line of reasoning he used in 1881, Michelson would seat at his desktop computer to calculate the expected fringeshifts for several solar speeds ar...If Michelson were to answer the question posed in the title, given the line of reasoning he used in 1881, Michelson would seat at his desktop computer to calculate the expected fringeshifts for several solar speeds around 400 km/s and various directions of motion. Present author did exactly the same in 2001 to plan his repetition of Michelson and Morley’s (MM) 1887 experiment. The paper sketchedly summarizes the procedure to calculate expected fringeshifts in the MM interferometer for solar speeds available at Miller’s epoch. In a pre-relativistic context, amplitudes of several fringeshifts may be expected in both MM and Miller experiments. However, all interferometer experiments up to 1930 were designed under the (incorrect from a modern viewpoint) assumption that fringeshifts would be smaller than one fringe-width. The inescapable conclusion is that those experiments were not appropriate to measure the true value of solar motion, always yielding a small, but lower than expected, value for solar speed. The ensuing “negative” interpretation led to the birth of relativity theory and to a new series of experiments implicitly designed to test the relativistic hypothesis of length-contraction, while the earlier “positive” experiments were designed to test a different hypothesis: whether the motion of Earth relative to some preferred frame can be measured using an interferometer of constant dimensions. With the benefit of hindsight this writer repeated the MM experiment, correcting main weaknesses identified up to the Michelson-Morley-Miller (MMM) measurements at Mount Wilson from April 1925 to February 1926. A new possible reinterpretation of the MMM data as a sequence of stationary measurements is pointed out. Our Michelson-Morley-Miller-Munera (MMMM) experiment at Bogota (Colombia) from January 2003 to June 2005 gave values for solar absolute velocity in the same range as those obtained by astronomical means. Surprisingly, our results are compatible with modern third-party MM-type experiments designed and interpreted within relativistic contexts. Thus, a so far unexplored possibility arises: can interferometric experiments distinguish between pre-relativistic and relativistic theories? Our answer is negative.展开更多
There are several petawatt-scale laser facilities around the world and the fidelity of the pulses to target is critical in achieving the highest focused intensities and the highest possible contrast. The United Kingdo...There are several petawatt-scale laser facilities around the world and the fidelity of the pulses to target is critical in achieving the highest focused intensities and the highest possible contrast. The United Kingdom has three such laser facilities which are currently open for access to the academic community: Orion at AWE, Aldermaston and Vulcan & Astra-Gemini at the Central Laser Facility(CLF), STFC(Science and Technology Facilities Council)Rutherford Appleton Laboratory(RAL). These facilities represent the two main classes of petawatt facilities: the mixed OPCPA/Nd:glass high-energy systems of Orion and Vulcan and the ultra-short-pulse Ti:Sapphire system of AstraGemini. Many of the techniques used to enhance and control the pulse generation and delivery to target have been pioneered on these facilities. In this paper, we present the system designs which make this possible and discuss the contrast enhancement schemes that have been implemented.展开更多
Introduction:According to the empirical regularity called Taylor’s law,the variance of population density in samples of populations is a power of the mean population density.The exponent is often between 1 and 2.Our ...Introduction:According to the empirical regularity called Taylor’s law,the variance of population density in samples of populations is a power of the mean population density.The exponent is often between 1 and 2.Our experiments investigated how genetics,evolution,and environment shape Taylor’s law.Methods:Genetically different strains(wild type and hypermutator)of the bacterium Pseudomonas fluorescens evolved and were assayed under different environmental conditions(with and without antibiotic rifampicin and bacteriophage SBW252,separately and in combination).Results:Experimental treatments altered the exponent b,but not the power law form,of the relation between variance and mean population density.Bacterial populations treated only with rifampicin had a narrow range of mean population densities and exponent b=5.43.Populations exposed to rifampicin plus phage had b=1.51.In ancestral,control,and phage-exposed populations,mean abundance varied widely and b was not significantly different from 2.Evolutionary factors(mutation rate,selection)and ecological factors(abiotic,biotic)jointly influenced b.Conclusions:Taylor’s power law relationship accurately and robustly described variance as a function of mean population density,with overall exponent b=1.89.These and other experiments with different factors acting on bacterial population size support the relevance of models that predict‘universal’patterns of fluctuation scaling.展开更多
This paper provides an up-to-date review of the problems related to the generation,detection and mitigation of strong electromagnetic pulses created in the interaction of high-power,high-energy laser pulses with diffe...This paper provides an up-to-date review of the problems related to the generation,detection and mitigation of strong electromagnetic pulses created in the interaction of high-power,high-energy laser pulses with different types of solid targets.It includes new experimental data obtained independently at several international laboratories.The mechanisms of electromagnetic field generation are analyzed and considered as a function of the intensity and the spectral range of emissions they produce.The major emphasis is put on the GHz frequency domain,which is the most damaging for electronics and may have important applications.The physics of electromagnetic emissions in other spectral domains,in particular THz and MHz,is also discussed.The theoretical models and numerical simulations are compared with the results of experimental measurements,with special attention to the methodology of measurements and complementary diagnostics.Understanding the underlying physical processes is the basis for developing techniques to mitigate the electromagnetic threat and to harness electromagnetic emissions,which may have promising applications.展开更多
In the 2015 review paper‘Petawatt Class Lasers Worldwide’a comprehensive overview of the current status of highpower facilities of>200 TW was presented.This was largely based on facility specifications,with some ...In the 2015 review paper‘Petawatt Class Lasers Worldwide’a comprehensive overview of the current status of highpower facilities of>200 TW was presented.This was largely based on facility specifications,with some description of their uses,for instance in fundamental ultra-high-intensity interactions,secondary source generation,and inertial confinement fusion(ICF).With the 2018 Nobel Prize in Physics being awarded to Professors Donna Strickland and Gerard Mourou for the development of the technique of chirped pulse amplification(CPA),which made these lasers possible,we celebrate by providing a comprehensive update of the current status of ultra-high-power lasers and demonstrate how the technology has developed.We are now in the era of multi-petawatt facilities coming online,with 100 PW lasers being proposed and even under construction.In addition to this there is a pull towards development of industrial and multi-disciplinary applications,which demands much higher repetition rates,delivering high-average powers with higher efficiencies and the use of alternative wavelengths:mid-IR facilities.So apart from a comprehensive update of the current global status,we want to look at what technologies are to be deployed to get to these new regimes,and some of the critical issues facing their development.展开更多
David Neely was an internationally recognised scientist who formed collaborations and friendships across the world. His passion for his work always shone through. He always made time for early-career scientists and be...David Neely was an internationally recognised scientist who formed collaborations and friendships across the world. His passion for his work always shone through. He always made time for early-career scientists and became a mentor and supervisor to many. He was an active Editorial Board Member of the international journal High Power Laser Science and Engineering. Sadly, David was taken from us much too early. In this Editorial we pay tribute to his work through his publications in the journal.展开更多
In 2017 the journal High Power Laser Science and Engineering produced a Special Issue on Target Fabrication.The scope of the special issue was to span the latest developments and reviews on topics related to their dep...In 2017 the journal High Power Laser Science and Engineering produced a Special Issue on Target Fabrication.The scope of the special issue was to span the latest developments and reviews on topics related to their deployment on ultrahigh-energy/power laser facilities.The topics invited for inclusion were:·Target assembly·Novel characterization展开更多
文摘If Michelson were to answer the question posed in the title, given the line of reasoning he used in 1881, Michelson would seat at his desktop computer to calculate the expected fringeshifts for several solar speeds around 400 km/s and various directions of motion. Present author did exactly the same in 2001 to plan his repetition of Michelson and Morley’s (MM) 1887 experiment. The paper sketchedly summarizes the procedure to calculate expected fringeshifts in the MM interferometer for solar speeds available at Miller’s epoch. In a pre-relativistic context, amplitudes of several fringeshifts may be expected in both MM and Miller experiments. However, all interferometer experiments up to 1930 were designed under the (incorrect from a modern viewpoint) assumption that fringeshifts would be smaller than one fringe-width. The inescapable conclusion is that those experiments were not appropriate to measure the true value of solar motion, always yielding a small, but lower than expected, value for solar speed. The ensuing “negative” interpretation led to the birth of relativity theory and to a new series of experiments implicitly designed to test the relativistic hypothesis of length-contraction, while the earlier “positive” experiments were designed to test a different hypothesis: whether the motion of Earth relative to some preferred frame can be measured using an interferometer of constant dimensions. With the benefit of hindsight this writer repeated the MM experiment, correcting main weaknesses identified up to the Michelson-Morley-Miller (MMM) measurements at Mount Wilson from April 1925 to February 1926. A new possible reinterpretation of the MMM data as a sequence of stationary measurements is pointed out. Our Michelson-Morley-Miller-Munera (MMMM) experiment at Bogota (Colombia) from January 2003 to June 2005 gave values for solar absolute velocity in the same range as those obtained by astronomical means. Surprisingly, our results are compatible with modern third-party MM-type experiments designed and interpreted within relativistic contexts. Thus, a so far unexplored possibility arises: can interferometric experiments distinguish between pre-relativistic and relativistic theories? Our answer is negative.
文摘There are several petawatt-scale laser facilities around the world and the fidelity of the pulses to target is critical in achieving the highest focused intensities and the highest possible contrast. The United Kingdom has three such laser facilities which are currently open for access to the academic community: Orion at AWE, Aldermaston and Vulcan & Astra-Gemini at the Central Laser Facility(CLF), STFC(Science and Technology Facilities Council)Rutherford Appleton Laboratory(RAL). These facilities represent the two main classes of petawatt facilities: the mixed OPCPA/Nd:glass high-energy systems of Orion and Vulcan and the ultra-short-pulse Ti:Sapphire system of AstraGemini. Many of the techniques used to enhance and control the pulse generation and delivery to target have been pioneered on these facilities. In this paper, we present the system designs which make this possible and discuss the contrast enhancement schemes that have been implemented.
基金The collection of the data analyzed here was funded by grants from the French Agence National de la Recherche(ANR)‘CoMute’(ANR-06-BLAN-0164)and‘EvolStress’(ANR-09-BLAN-099-01)MEH and OK were supported by grants‘EvolStress’(ANR-09-BLAN-099-01)and‘EvoRange’(ANR-09-PEXT-011)JEC was supported in part by grant EF-1038337 from the U.S.National Science Foundation,a grant from the region of Languedoc-Roussillon through the University of Montpellier 2,the assistance of Priscilla K.Rogerson,and the hospitality of Michael E.Hochberg and family during this work.Two referees provided helpful criticisms and suggestions.This is publication ISE-M 2012-032.
文摘Introduction:According to the empirical regularity called Taylor’s law,the variance of population density in samples of populations is a power of the mean population density.The exponent is often between 1 and 2.Our experiments investigated how genetics,evolution,and environment shape Taylor’s law.Methods:Genetically different strains(wild type and hypermutator)of the bacterium Pseudomonas fluorescens evolved and were assayed under different environmental conditions(with and without antibiotic rifampicin and bacteriophage SBW252,separately and in combination).Results:Experimental treatments altered the exponent b,but not the power law form,of the relation between variance and mean population density.Bacterial populations treated only with rifampicin had a narrow range of mean population densities and exponent b=5.43.Populations exposed to rifampicin plus phage had b=1.51.In ancestral,control,and phage-exposed populations,mean abundance varied widely and b was not significantly different from 2.Evolutionary factors(mutation rate,selection)and ecological factors(abiotic,biotic)jointly influenced b.Conclusions:Taylor’s power law relationship accurately and robustly described variance as a function of mean population density,with overall exponent b=1.89.These and other experiments with different factors acting on bacterial population size support the relevance of models that predict‘universal’patterns of fluctuation scaling.
基金the framework of the EUROfusion Consortium and funded from the Euratom research and training programme 2014–2018 and 2019– 2020 under grant agreement No. 633053the ELI Beamlines Projects LQ1606 and 19-02545S with financial support from the Czech Science Foundation and the Ministry of Education, Youth and Sports of the Czech Republic+6 种基金support from the European Regional Development Fund, the project ELITAS CZ.02.1.01/0.0/0.0/16 013/0001793the National Programme of ‘Sustainability Ⅱ’ and ELI phase 2 CZ.02.1.01/0.0/0.0/15008/0000162The PETAL project was designed and built by the CEA under the financial auspices of the Region Nouvelle Aquitaine, the French Government and the European Unionsupported by EPSRC grants EP/K022415/1 and EP/R006202supported by the European Cluster of Advanced Laser Light Sources, EUCALL, which has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 654220funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 654148 Laserlab-Europethe use of the EPOCH PIC code (developed under EPSRC grant EP/G054940/1).
文摘This paper provides an up-to-date review of the problems related to the generation,detection and mitigation of strong electromagnetic pulses created in the interaction of high-power,high-energy laser pulses with different types of solid targets.It includes new experimental data obtained independently at several international laboratories.The mechanisms of electromagnetic field generation are analyzed and considered as a function of the intensity and the spectral range of emissions they produce.The major emphasis is put on the GHz frequency domain,which is the most damaging for electronics and may have important applications.The physics of electromagnetic emissions in other spectral domains,in particular THz and MHz,is also discussed.The theoretical models and numerical simulations are compared with the results of experimental measurements,with special attention to the methodology of measurements and complementary diagnostics.Understanding the underlying physical processes is the basis for developing techniques to mitigate the electromagnetic threat and to harness electromagnetic emissions,which may have promising applications.
文摘In the 2015 review paper‘Petawatt Class Lasers Worldwide’a comprehensive overview of the current status of highpower facilities of>200 TW was presented.This was largely based on facility specifications,with some description of their uses,for instance in fundamental ultra-high-intensity interactions,secondary source generation,and inertial confinement fusion(ICF).With the 2018 Nobel Prize in Physics being awarded to Professors Donna Strickland and Gerard Mourou for the development of the technique of chirped pulse amplification(CPA),which made these lasers possible,we celebrate by providing a comprehensive update of the current status of ultra-high-power lasers and demonstrate how the technology has developed.We are now in the era of multi-petawatt facilities coming online,with 100 PW lasers being proposed and even under construction.In addition to this there is a pull towards development of industrial and multi-disciplinary applications,which demands much higher repetition rates,delivering high-average powers with higher efficiencies and the use of alternative wavelengths:mid-IR facilities.So apart from a comprehensive update of the current global status,we want to look at what technologies are to be deployed to get to these new regimes,and some of the critical issues facing their development.
文摘David Neely was an internationally recognised scientist who formed collaborations and friendships across the world. His passion for his work always shone through. He always made time for early-career scientists and became a mentor and supervisor to many. He was an active Editorial Board Member of the international journal High Power Laser Science and Engineering. Sadly, David was taken from us much too early. In this Editorial we pay tribute to his work through his publications in the journal.
文摘In 2017 the journal High Power Laser Science and Engineering produced a Special Issue on Target Fabrication.The scope of the special issue was to span the latest developments and reviews on topics related to their deployment on ultrahigh-energy/power laser facilities.The topics invited for inclusion were:·Target assembly·Novel characterization
