K. Gouriet, T. Itina, S. Noël, J. Hermann, M. Sentis, L. Zhigilei
The main objective of this study is to explain the experimental observations. To simulate material ablation, plume formation and its evolution, we developed a combined molecular dynamics (MD) and direct simulation Monte Carlo (DSMC) computational study of laser ablation plume evolution. The first process of the material ablation is described by the MD method. The expansion of the ejected plume is modelled by the DSMC method. To better understand the formation and the evolution of nanoparticles present in the plume, we first used separate MD simulations to analyse the evolution of a cluster in the presence of background gas with different properties (density, temperature). In particular, we examine evaporation and growth reactions of a cluster with different size and initial temperature. As a result of MD calculations, we determinate the influence of the background gas parameters on the nanoparticles. The reactions rates such as evaporation/condensation, which are obtained by MD simulations, are directly transferred to the DSMC part of our combined model. Finally, several calculations performed by using MD-DSMC model demonstrate both plume dynamics and longer-time cluster evolution. Calculations results are compared with experimental findings.
{"title":"Formation of nanoparticles by short and ultra-short laser pulses","authors":"K. Gouriet, T. Itina, S. Noël, J. Hermann, M. Sentis, L. Zhigilei","doi":"10.1117/12.782711","DOIUrl":"https://doi.org/10.1117/12.782711","url":null,"abstract":"The main objective of this study is to explain the experimental observations. To simulate material ablation, plume formation and its evolution, we developed a combined molecular dynamics (MD) and direct simulation Monte Carlo (DSMC) computational study of laser ablation plume evolution. The first process of the material ablation is described by the MD method. The expansion of the ejected plume is modelled by the DSMC method. To better understand the formation and the evolution of nanoparticles present in the plume, we first used separate MD simulations to analyse the evolution of a cluster in the presence of background gas with different properties (density, temperature). In particular, we examine evaporation and growth reactions of a cluster with different size and initial temperature. As a result of MD calculations, we determinate the influence of the background gas parameters on the nanoparticles. The reactions rates such as evaporation/condensation, which are obtained by MD simulations, are directly transferred to the DSMC part of our combined model. Finally, several calculations performed by using MD-DSMC model demonstrate both plume dynamics and longer-time cluster evolution. Calculations results are compared with experimental findings.","PeriodicalId":249315,"journal":{"name":"High-Power Laser Ablation","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122249901","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
H. Urbassek, Christian Anders, Luis Sandoval, A. Upadhyay
The physical mechanisms and processes underlying the erosion of a surface induced by cluster bombardment or short-pulse laser irradiation are highlighted. When the average energy delivered per atom in the vicinity of the surface becomes comparable to the cohesive energy of the solid, sputtering from a so-called spike may result. Such a spike leads to abundant sputtering (surface erosion) and crater formation. Direct atomization in the region of highest energy deposition, as well as melt flow and gas flow contribute to the erosion. The materials phenomena occurring after ultra-fast laser irradiation of a metal in the ps- or fs-regime are reviewed. With increasing laser fluence, the film melts, voids are formed, the film tears (spallation), and finally fragments to form a multitude of clusters. These processes are universal in the sense that they occur in widely differing materials such as metals or van-der-Waals bonded materials. We investigate a Lennard-Jones solid as well as four different metals (Al, Cu, Ti, W), which vary widely in their cohesive energy, melting temperature, bulk modulus, and crystal structure. When the energy transfer starting the process is scaled to the cohesive energy of the material, the thresholds of these processes adopt similar values. A comparison of the similarities and differences of the mechanisms underlying surface erosion under cluster ion impact and ultrafast laser irradiation will be drawn.
{"title":"Ultrafast laser irradiation vs cluster ion impact: molecular-dynamics comparison of materials processes in highly energized solids","authors":"H. Urbassek, Christian Anders, Luis Sandoval, A. Upadhyay","doi":"10.1117/12.784270","DOIUrl":"https://doi.org/10.1117/12.784270","url":null,"abstract":"The physical mechanisms and processes underlying the erosion of a surface induced by cluster bombardment or short-pulse laser irradiation are highlighted. When the average energy delivered per atom in the vicinity of the surface becomes comparable to the cohesive energy of the solid, sputtering from a so-called spike may result. Such a spike leads to abundant sputtering (surface erosion) and crater formation. Direct atomization in the region of highest energy deposition, as well as melt flow and gas flow contribute to the erosion. The materials phenomena occurring after ultra-fast laser irradiation of a metal in the ps- or fs-regime are reviewed. With increasing laser fluence, the film melts, voids are formed, the film tears (spallation), and finally fragments to form a multitude of clusters. These processes are universal in the sense that they occur in widely differing materials such as metals or van-der-Waals bonded materials. We investigate a Lennard-Jones solid as well as four different metals (Al, Cu, Ti, W), which vary widely in their cohesive energy, melting temperature, bulk modulus, and crystal structure. When the energy transfer starting the process is scaled to the cohesive energy of the material, the thresholds of these processes adopt similar values. A comparison of the similarities and differences of the mechanisms underlying surface erosion under cluster ion impact and ultrafast laser irradiation will be drawn.","PeriodicalId":249315,"journal":{"name":"High-Power Laser Ablation","volume":"28 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127801319","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
R. Stoian, A. Mermillod-Blondin, C. Mauclair, N. Huot, É. Audouard, I. M. Burakov, N. Bulgakova, Y. P. Meschcheryakov, A. Rosenfeld, A. Husakou, I. Hertel
Ultrafast lasers emerged as promising tools to process refractive index changes in band-gap materials, resulting in waveguiding functions. Positive refractive index changes were often reported in fused silica matrices. However, in glasses characterized by slow electronic relaxation and high thermal expansion, the refractive index change is usually negative, detrimental for waveguide writing. This relates to the formation of hot regions, where, due to thermal expansion, material is quenched in low-density phases. We discuss control mechanisms related to spatio-temporal heat-source design which may be tuned by temporally shaped laser radiation. Programmable temporal tailoring of pulse envelopes triggers transitions from thermal expansion to directional inelastic flow. Consequently, material compaction leads to a positive refractive index change and guiding structures may thus be created. From an application perspective, the structuring quality degrades with the focusing depth due to wavefront distortions generated at the air-dielectric interface inducing spatial energy dispersion. Spatial beam tailoring corrects beam propagation distortion, improving the structuring accuracy. The corrective process is becoming important when laser energy has to be transported without losses at arbitrary depths, with the purpose of triggering mechanisms of positive index change.
{"title":"Designing laser-induced refractive index changes in \"thermal\" glasses","authors":"R. Stoian, A. Mermillod-Blondin, C. Mauclair, N. Huot, É. Audouard, I. M. Burakov, N. Bulgakova, Y. P. Meschcheryakov, A. Rosenfeld, A. Husakou, I. Hertel","doi":"10.1117/12.783449","DOIUrl":"https://doi.org/10.1117/12.783449","url":null,"abstract":"Ultrafast lasers emerged as promising tools to process refractive index changes in band-gap materials, resulting in waveguiding functions. Positive refractive index changes were often reported in fused silica matrices. However, in glasses characterized by slow electronic relaxation and high thermal expansion, the refractive index change is usually negative, detrimental for waveguide writing. This relates to the formation of hot regions, where, due to thermal expansion, material is quenched in low-density phases. We discuss control mechanisms related to spatio-temporal heat-source design which may be tuned by temporally shaped laser radiation. Programmable temporal tailoring of pulse envelopes triggers transitions from thermal expansion to directional inelastic flow. Consequently, material compaction leads to a positive refractive index change and guiding structures may thus be created. From an application perspective, the structuring quality degrades with the focusing depth due to wavefront distortions generated at the air-dielectric interface inducing spatial energy dispersion. Spatial beam tailoring corrects beam propagation distortion, improving the structuring accuracy. The corrective process is becoming important when laser energy has to be transported without losses at arbitrary depths, with the purpose of triggering mechanisms of positive index change.","PeriodicalId":249315,"journal":{"name":"High-Power Laser Ablation","volume":"40 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114986832","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Y. Petrov, V. Zhakhovskiĭ, N. Inogamov, S. Ashitkov, V. Khokhlov, Arun K. Upadhyay, M. Agranat, S. Anisimov, K. Nishihara, B. Rethfeld, H. Urbassek
The motion of both Lennard-Jones solids and metals induced by ultrashort laser irradiation near the ablation threshold is investigated by molecular dynamics simulation. The universality of the ablation threshold fluence with respect to the cohesion energy of solids irradiated by femtosecond laser pulses is demonstrated for Lennard-Jones solid and metals simulated by many-body EAM potentials.
{"title":"Equation of state of matter irradiated by short laser pulse and geometry of spalled cupola","authors":"Y. Petrov, V. Zhakhovskiĭ, N. Inogamov, S. Ashitkov, V. Khokhlov, Arun K. Upadhyay, M. Agranat, S. Anisimov, K. Nishihara, B. Rethfeld, H. Urbassek","doi":"10.1117/12.782612","DOIUrl":"https://doi.org/10.1117/12.782612","url":null,"abstract":"The motion of both Lennard-Jones solids and metals induced by ultrashort laser irradiation near the ablation threshold is investigated by molecular dynamics simulation. The universality of the ablation threshold fluence with respect to the cohesion energy of solids irradiated by femtosecond laser pulses is demonstrated for Lennard-Jones solid and metals simulated by many-body EAM potentials.","PeriodicalId":249315,"journal":{"name":"High-Power Laser Ablation","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114992342","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. Baudelet, Myriam G. Boueri, Jin Yu, X. Mao, R. Russo
Laser-Induced Breakdown Spectroscopy (LIBS) has been used since 40 years on typical samples such as metals, alloys, rocks. Detection of organic hazards or analysis of biological compounds under atmospheric pressure with LIBS represents a new challenge. For this purpose, we need better understandings of the physico-chemical properties of the plasma in atmosphere and their influences on the LIBS signal. As a model sample of organic materials, Nylon 6-6 has been studied under nanosecond ablation at different wavelengths (1064 nm and 266 nm) and energies (from 1 to 5 mJ) in order to observe the influence of these parameters. Shadowgraph technique is used to image the plasma at its early stage of expansion (0 to 40 ns). Time-resolved LIBS signal is recorded for longer times (50 ns to 5 μs). In the infrared regime, the expansion of the plume is faster along the laser axis, perpendicular to the sample surface. On the contrary, for UV ablation, the expansion of the plume is quite isotropic. We can also observe different regimes of expansion due to Laser-Supported Detonation Waves (LSDW) above 3 mJ in the UV regime. In particular, these observations provide us ideas to understand the kinetics of the CN emission in the LIBS signal. In the IR regime, a formation of CN due to carbon present in the sample and nitrogen in the air via the reaction 2C + N2 → 2CN can be observed. In the UV regime, the direct ablation of CN bonds is clearly seen but other effects like screening and recombination due to LSDW have also been observed.
{"title":"Correlation between early-stage expansion and spectral emission of a nanosecond laser-induced plasma from organic material","authors":"M. Baudelet, Myriam G. Boueri, Jin Yu, X. Mao, R. Russo","doi":"10.1117/12.785218","DOIUrl":"https://doi.org/10.1117/12.785218","url":null,"abstract":"Laser-Induced Breakdown Spectroscopy (LIBS) has been used since 40 years on typical samples such as metals, alloys, rocks. Detection of organic hazards or analysis of biological compounds under atmospheric pressure with LIBS represents a new challenge. For this purpose, we need better understandings of the physico-chemical properties of the plasma in atmosphere and their influences on the LIBS signal. As a model sample of organic materials, Nylon 6-6 has been studied under nanosecond ablation at different wavelengths (1064 nm and 266 nm) and energies (from 1 to 5 mJ) in order to observe the influence of these parameters. Shadowgraph technique is used to image the plasma at its early stage of expansion (0 to 40 ns). Time-resolved LIBS signal is recorded for longer times (50 ns to 5 μs). In the infrared regime, the expansion of the plume is faster along the laser axis, perpendicular to the sample surface. On the contrary, for UV ablation, the expansion of the plume is quite isotropic. We can also observe different regimes of expansion due to Laser-Supported Detonation Waves (LSDW) above 3 mJ in the UV regime. In particular, these observations provide us ideas to understand the kinetics of the CN emission in the LIBS signal. In the IR regime, a formation of CN due to carbon present in the sample and nitrogen in the air via the reaction 2C + N2 → 2CN can be observed. In the UV regime, the direct ablation of CN bonds is clearly seen but other effects like screening and recombination due to LSDW have also been observed.","PeriodicalId":249315,"journal":{"name":"High-Power Laser Ablation","volume":"7005 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129427924","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
B. Rethfeld, S. Linden, L. Englert, M. Wollenhaupt, L. Haag, C. Sarpe-Tudoran, T. Baumert
Transparent solids may absorb energy from a laser beam of sufficient high intensity. Several models are under consideration to describe the evolution of the free-electron density. Some of these models keep track of the energy distribution of the electrons. In this work we compare different models and give rules to estimate which one is applicable. We present the inclusion of a term in the multiple rate equation approach, recently introduced, describing fast recombination processes to exciton states. Moreover, we present experimental results with temporally asymmetric femtosecond laser pulses, impinging on a surface of fused silica. We found different thresholds for surface material modification with respect to an asymetric pulse and its time reversed counterpart. This difference is due to a different time-and-intensity dependence of the main ionization processes, which can be controlled with help of femtosecond shaped laser pulses.
{"title":"Electron generation in laser-irradiated insulators: theoretical descriptions and their application","authors":"B. Rethfeld, S. Linden, L. Englert, M. Wollenhaupt, L. Haag, C. Sarpe-Tudoran, T. Baumert","doi":"10.1117/12.784630","DOIUrl":"https://doi.org/10.1117/12.784630","url":null,"abstract":"Transparent solids may absorb energy from a laser beam of sufficient high intensity. Several models are under consideration to describe the evolution of the free-electron density. Some of these models keep track of the energy distribution of the electrons. In this work we compare different models and give rules to estimate which one is applicable. We present the inclusion of a term in the multiple rate equation approach, recently introduced, describing fast recombination processes to exciton states. Moreover, we present experimental results with temporally asymmetric femtosecond laser pulses, impinging on a surface of fused silica. We found different thresholds for surface material modification with respect to an asymetric pulse and its time reversed counterpart. This difference is due to a different time-and-intensity dependence of the main ionization processes, which can be controlled with help of femtosecond shaped laser pulses.","PeriodicalId":249315,"journal":{"name":"High-Power Laser Ablation","volume":"26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121451170","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper describes the status of the stadium-sized National Ignition Facility (NIF), the world's largest laser system and first operational multi-megajoule laser. The 192-beam NIF, located at Lawrence Livermore National Laboratory (LLNL), is 96% complete and scheduled for completion in March 2009. The NIF laser will produce nanosecond laser pulses with energies up to approximately 4 MJ in the infrared (laser wavelength = 1.053-μm) and 2MJ in the ultraviolet (laser wavelength = 0.35-μ m). With these energies NIF will access conditions of pressure and temperature not previously available on earth, allowing it to conduct experiments in support of the nation's national security, energy, and fundamental science goals. First ignition experiments at NIF are scheduled for FY2010. This paper will provide an overview of the NIF laser and the ignition, energy, and fundamental science activities at NIF.
{"title":"Multi-megajoule NIF: ushering in a new era in high energy density science","authors":"E. Moses","doi":"10.1117/12.782724","DOIUrl":"https://doi.org/10.1117/12.782724","url":null,"abstract":"This paper describes the status of the stadium-sized National Ignition Facility (NIF), the world's largest laser system and first operational multi-megajoule laser. The 192-beam NIF, located at Lawrence Livermore National Laboratory (LLNL), is 96% complete and scheduled for completion in March 2009. The NIF laser will produce nanosecond laser pulses with energies up to approximately 4 MJ in the infrared (laser wavelength = 1.053-μm) and 2MJ in the ultraviolet (laser wavelength = 0.35-μ m). With these energies NIF will access conditions of pressure and temperature not previously available on earth, allowing it to conduct experiments in support of the nation's national security, energy, and fundamental science goals. First ignition experiments at NIF are scheduled for FY2010. This paper will provide an overview of the NIF laser and the ignition, energy, and fundamental science activities at NIF.","PeriodicalId":249315,"journal":{"name":"High-Power Laser Ablation","volume":"73 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116237175","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Recently, using a femtosecond laser surface structuring technique we turned highly reflective metals to highly absorptive, creating the so-called "black metals". In this study, we made an even more significant advancement. Here, we demonstrate that our femtosecond laser structuring technique not only allows us to create black metals but also gray and even color metals. We show that our technique essentially provides a controllable modification of optical properties of metals from the UV to THz spectral range via surface structuring on the nano-, micro-, and submillimeter-scales.
{"title":"Metal colorization with femtosecond laser pulses","authors":"A. Vorobyev, Chunlei Guo","doi":"10.1117/12.782699","DOIUrl":"https://doi.org/10.1117/12.782699","url":null,"abstract":"Recently, using a femtosecond laser surface structuring technique we turned highly reflective metals to highly absorptive, creating the so-called \"black metals\". In this study, we made an even more significant advancement. Here, we demonstrate that our femtosecond laser structuring technique not only allows us to create black metals but also gray and even color metals. We show that our technique essentially provides a controllable modification of optical properties of metals from the UV to THz spectral range via surface structuring on the nano-, micro-, and submillimeter-scales.","PeriodicalId":249315,"journal":{"name":"High-Power Laser Ablation","volume":"595 ","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114003460","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
B. Woodard, J. W. Zimmerman, J. Verdeyen, D. Carroll, T. Field, G. Benavides, A. Palla, W. Solomon
Experimental investigations of radio-frequency discharges in O2/He/NO mixtures in the pressure range of 1-100 Torr and power range of 0.1-2.5 kW have indicated that O2(a1Δ) production is a strong function of geometry, pressure and diluent ratio. The goal of these investigations was maximization of both the yield and flow rate (power flux) of O2(a1Δ) in order to produce favorable conditions for application to an electric oxygen-iodine laser (EOIL). As pressure is increased, yield performance is dominated by the influence of geometry and diluent ratio. Numerous measurements of O2(a1Δ), oxygen atoms, and discharge excited states are made in order to describe the discharge performance dependence on various parameters.
{"title":"Improved production of O2(a1Δ) in transverse radio-frequency discharges","authors":"B. Woodard, J. W. Zimmerman, J. Verdeyen, D. Carroll, T. Field, G. Benavides, A. Palla, W. Solomon","doi":"10.1117/12.782665","DOIUrl":"https://doi.org/10.1117/12.782665","url":null,"abstract":"Experimental investigations of radio-frequency discharges in O2/He/NO mixtures in the pressure range of 1-100 Torr and power range of 0.1-2.5 kW have indicated that O2(a1Δ) production is a strong function of geometry, pressure and diluent ratio. The goal of these investigations was maximization of both the yield and flow rate (power flux) of O2(a1Δ) in order to produce favorable conditions for application to an electric oxygen-iodine laser (EOIL). As pressure is increased, yield performance is dominated by the influence of geometry and diluent ratio. Numerous measurements of O2(a1Δ), oxygen atoms, and discharge excited states are made in order to describe the discharge performance dependence on various parameters.","PeriodicalId":249315,"journal":{"name":"High-Power Laser Ablation","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122933819","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
An impulse measurement device and analysis package was conceived, designed, constructed, tested, and demonstrated to be capable of: measuring nanoNewton-seconds to milliNewton-seconds of impulse due to laser-ablation; being transported as carry-on baggage; set-up and tear-down times of less than an hour; target exchange times of less than two minutes (targets can be ablated at multiple positions for thousands of shots); measurements in air and in vacuum; error of just a few percent; repeatability over a wide range of potential systematic error sources; and time between measurements, including ring-down and analysis, of less than 30 seconds. The instrument consists of a cantilever (i.e. leaf spring), whose time-dependent displacement/oscillation is measured and analyzed to determine the impulse imparted by a laser pulse to a target. These shapes are readily/commercially available, and any target material can be used, provided it can be fashioned in the form of a cantilever, or as a coating/film/tape, suitable for mounting on a cantilever of known geometry. The instrument was calibrated both statically and dynamically, and measurements were performed on brass, steel, and Aluminum, using laser pulses of ~7ns, ~500ps, and ~500fs. The results agree well with those published in the literature, with surface effects, atmosphere, and pre-/post-pulses demonstrating interesting effects and indicating areas for further study. In addition to exploring space-propulsion applications, measurements were performed to explore the strong beneficial effects of depositing lines of energy ahead of supersonic and hypersonic vehicles. This deposition creates a low-density channel, through which a vehicle can travel with dramatically reduced drag. Temperature and pressure are both also reduced on the front surfaces of the vehicle, while density and pressure are increased at the vehicle base. When applied off-center, this technique can be used to control the vehicle, employing the entire body as the control surface and eliminating the need for actuators. Numerical results for drag-reduction, temperature-reduction, and control forces are indicated here.
{"title":"Ultrashort pulse lasers applied to propulsion/control in space- and atmospheric-flight","authors":"K. Kremeyer","doi":"10.1117/12.786468","DOIUrl":"https://doi.org/10.1117/12.786468","url":null,"abstract":"An impulse measurement device and analysis package was conceived, designed, constructed, tested, and demonstrated to be capable of: measuring nanoNewton-seconds to milliNewton-seconds of impulse due to laser-ablation; being transported as carry-on baggage; set-up and tear-down times of less than an hour; target exchange times of less than two minutes (targets can be ablated at multiple positions for thousands of shots); measurements in air and in vacuum; error of just a few percent; repeatability over a wide range of potential systematic error sources; and time between measurements, including ring-down and analysis, of less than 30 seconds. The instrument consists of a cantilever (i.e. leaf spring), whose time-dependent displacement/oscillation is measured and analyzed to determine the impulse imparted by a laser pulse to a target. These shapes are readily/commercially available, and any target material can be used, provided it can be fashioned in the form of a cantilever, or as a coating/film/tape, suitable for mounting on a cantilever of known geometry. The instrument was calibrated both statically and dynamically, and measurements were performed on brass, steel, and Aluminum, using laser pulses of ~7ns, ~500ps, and ~500fs. The results agree well with those published in the literature, with surface effects, atmosphere, and pre-/post-pulses demonstrating interesting effects and indicating areas for further study. In addition to exploring space-propulsion applications, measurements were performed to explore the strong beneficial effects of depositing lines of energy ahead of supersonic and hypersonic vehicles. This deposition creates a low-density channel, through which a vehicle can travel with dramatically reduced drag. Temperature and pressure are both also reduced on the front surfaces of the vehicle, while density and pressure are increased at the vehicle base. When applied off-center, this technique can be used to control the vehicle, employing the entire body as the control surface and eliminating the need for actuators. Numerical results for drag-reduction, temperature-reduction, and control forces are indicated here.","PeriodicalId":249315,"journal":{"name":"High-Power Laser Ablation","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125868132","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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