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Sample records for intense laser irradiation

  1. Polyatomic molecules under intense femtosecond laser irradiation.

    PubMed

    Konar, Arkaprabha; Shu, Yinan; Lozovoy, Vadim V; Jackson, James E; Levine, Benjamin G; Dantus, Marcos

    2014-12-11

    Interaction of intense laser pulses with atoms and molecules is at the forefront of atomic, molecular, and optical physics. It is the gateway to powerful new tools that include above threshold ionization, high harmonic generation, electron diffraction, molecular tomography, and attosecond pulse generation. Intense laser pulses are ideal for probing and manipulating chemical bonding. Though the behavior of atoms in strong fields has been well studied, molecules under intense fields are not as well understood and current models have failed in certain important aspects. Molecules, as opposed to atoms, present confounding possibilities of nuclear and electronic motion upon excitation. The dynamics and fragmentation patterns in response to the laser field are structure sensitive; therefore, a molecule cannot simply be treated as a "bag of atoms" during field induced ionization. In this article we present a set of experiments and theoretical calculations exploring the behavior of a large collection of aryl alkyl ketones when irradiated with intense femtosecond pulses. Specifically, we consider to what extent molecules retain their molecular identity and properties under strong laser fields. Using time-of-flight mass spectrometry in conjunction with pump-probe techniques we study the dynamical behavior of these molecules, monitoring ion yield modulation caused by intramolecular motions post ionization. The set of molecules studied is further divided into smaller sets, sorted by type and position of functional groups. The pump-probe time-delay scans show that among positional isomers the variations in relative energies, which amount to only a few hundred millielectronvolts, influence the dynamical behavior of the molecules despite their having experienced such high fields (V/Å). High level ab initio quantum chemical calculations were performed to predict molecular dynamics along with single and multiphoton resonances in the neutral and ionic states. We propose the

  2. Irradiation effect of polarization direction and intensity of semiconductor laser on injured peripheral nerve

    NASA Astrophysics Data System (ADS)

    Guo-Xin, Xiong; Lei-lei, Xiong

    2016-08-01

    To investigate the irradiation effect of polarization direction and the intensity of a semiconductor laser on the injured peripheral nerve in rabbits, the model of the injured common peroneal nerve was established, the L5,6 spinal segments of the rabbits were irradiated, a uniform rotating polarizer was placed at the laser output which made the polarization direction and intensity of the output laser change according to the 80 Hz cosine law. The experimental results show that irradiating the spinal segment of injured nerves in rabbits with this changeable semiconductor laser can significantly promote the regeneration of injured peripheral nerves and the function recovery.

  3. Advances in endonasal low intensity laser irradiation therapy

    NASA Astrophysics Data System (ADS)

    Jiao, Jian-Ling; Liu, Timon C.; Liu, Jiang; Cui, Li-Ping; Liu, Song-hao

    2005-07-01

    Endonasal low intensity laser therapy (ELILT) began in China in 1998. Now in China it is widely applied to treat hyperlipidemia and brain diseases such as Alzheimer's disease, Parkinson's disease, insomnia, poststroke depression, intractable headache, ache in head or face, cerebral thrombosis, acute ischemic cerebrovascular disease, migraine, brain lesion and mild cognitive impairment. There are four pathways mediating EILILT, Yangming channel, autonomic nervous systems and blood cells. Two unhealth acupoints of Yangming channal inside nose might mediate the one as is low intensity laser acupuncture. Unbalance autonomic nervous systems might be modulated. Blood cells might mediate the one as is intravascular low intensity laser therapy. These three pathways are integrated in ELILT so that serum amyloid β protein, malformation rate of erythrocyte, CCK-8, the level of viscosity at lower shear rates and hematocrit, or serum lipid might decrease, and melanin production/SOD activity or β endorphin might increase after ELILT treatment. These results indicate ELILT might work, but it need to be verified by randomized placebo-controlled trial.

  4. Magneto-optical imaging of magnetic domain pattern produced by intense femtosecond laser pulse irradiation

    NASA Astrophysics Data System (ADS)

    Sinha, Jaivarhan; Mohan, Shyam; Banerjee, S. S.; Kahaly, S.; Kumar, G. Ravindra

    2009-03-01

    An important and intriguing area of research is laser plasma generated giant magnetic field pulses. Interaction of ultrashort high intensity laser pulses with matter involves several mechanisms for generating ultrastrong magnetic fields. By irradiating a magnetic recordable tape constituting of γ-Fe2O3 particles with an intense p-polarized femtosecond laser pulses (˜ 10^16 W cm-2, 100fs), we have found complex magnetic field patterns stored in the tape. We image the local magnetic field distribution around the irradiated region [1] using the high sensitivity magneto-optical imaging technique. We understand the complex magnetic domains patterns recoded on the tape in terms of interesting instabilities [1] generated in the plasma produced during the irradiation of the tape with intense laser pulses. [0pt] [1] Jaivardhan Sinha, Shyam Mohan, S. S Banerjee, S. Kahaly, G. Ravindra Kumar, Phys. Rev. E 77, 046118(2008). *satyajit@iitk.ac.in

  5. Spectroscopic study of gold nanoparticle formation through high intensity laser irradiation of solution

    SciTech Connect

    Nakamura, Takahiro Sato, Shunichi; Herbani, Yuliati; Ursescu, Daniel; Banici, Romeo; Dabu, Razvan Victor

    2013-08-15

    A spectroscopic study of the gold nanoparticle (NP) formation by high-intensity femtosecond laser irradiation of a gold ion solution was reported. The effect of varying energy density of the laser on the formation of gold NPs was also investigated. The surface plasmon resonance (SPR) peak of the gold nanocolloid in real-time UV-visible absorption spectra during laser irradiation showed a distinctive progress; the SPR absorption peak intensity increased after a certain irradiation time, reached a maximum and then gradually decreased. During this absorption variation, at the same time, the peak wavelength changed from 530 to 507 nm. According to an empirical equation derived from a large volume of experimental data, the estimated mean size of the gold NPs varied from 43.4 to 3.2 nm during the laser irradiation. The mean size of gold NPs formed at specific irradiation times by transmission electron microscopy showed the similar trend as that obtained in the spectroscopic analysis. From these observations, the formation mechanism of gold NPs during laser irradiation was considered to have two steps. The first is a reduction of gold ions by reactive species produced through a non-linear reaction during high intensity laser irradiation of the solution; the second is the laser fragmentation of produced gold particles into smaller pieces. The gold nanocolloid produced after the fragmentation by excess irradiation showed high stability for at least a week without the addition of any dispersant because of the negative charge on the surface of the nanoparticles probably due to the surface oxidation of gold nanoparticles. A higher laser intensity resulted in a higher efficiency of gold NPs fabrication, which was attributed to a larger effective volume of the reaction.

  6. Effects of low intensity laser irradiation during healing of infected skin lesions in the rat

    NASA Astrophysics Data System (ADS)

    Nussbaum, Ethne L.; Lilge, Lothar; Mazzulli, Tony; Pritzker, Kenneth P.

    2006-02-01

    Purpose: To determine the effect of low intensity laser therapy (LILT) on healing of infected skin wounds in the rat. Methods: Wounds on the dorsum of Sprague-Dawley rats (14 per group) were inoculated or sham-inoculated with P. aeruginosa. Wounds were irradiated or sham-irradiated three times weekly from Day 1-19 using 635nm or 808nm diode lasers at radiant exposure of 1 or 20 J/cm2 delivered in continuous wave (CW) or at an intensity modulation frequency of 3800Hz. Wound area and bacterial growth were evaluated three times weekly. Results: CW 808 nm (1 and 20 J/cm2) irradiation generally delayed healing in acute wounds. However, from Day 10 onwards CW 808 nm (1 J/cm2 and 20 J/cm2) and 808 nm 3800 Hz (1 J/cm2) irradiation improved healing in inoculated wounds. Healing in acute wounds improved using 635 nm irradiation at low radiant exposure (1 J/cm2); however, using 635 nm irradiation at high radiant exposure (20 J/cm2) delayed healing. Bacterial balance in wounds was significantly altered using 635 nm (20 J/cm2) and CW 808 nm irradiation (1 and 20 J/cm2). Conclusion: Clearing wounds of normal flora was not associated with improved healing. Proliferation of staphylococcal species in wounds was associated with delayed healing.

  7. Generation of strongly coupled Xe cluster nanoplasmas by low intensive soft x-ray laser irradiation

    SciTech Connect

    Namba, S.; Hasegawa, N.; Kishimoto, M.; Nishikino, M.; Kawachi, T.

    2012-07-11

    A seeding gas jet including Xe clusters was irradiated with a laser-driven plasma soft x-ray laser pulse ({lambda}=13.9 nm, {approx}7 ps, {<=}5 Multiplication-Sign 10{sup 9} W/cm{sup 2}), where the laser photon energy is high enough to ionize 4d core electrons. In order to clarify how the innershell ionization followed by the Auger electron emission is affected under the intense laser irradiation, the electron energy distribution was measured. Photoelectron spectra showed that the peak position attributed to 4d hole shifted to lower energy and the spectral width was broadened with increasing cluster size. Moreover, the energy distribution exhibited that a strongly coupled cluster nanoplasma with several eV was generated.

  8. Reaction of cells to local, regional, and general low-intensive laser irradiation

    NASA Astrophysics Data System (ADS)

    Baibekov, Iskander M.; Kasymov, A. S.; Musaev, Erkin S.; Vorojeikin, V. M.; Artikov, S. N.

    1993-07-01

    Local influence of low intensive laser irradiation (LILI) of Helium-Neon (HNL), Copper vapor (CVL), Nitrogen (UVL) and Arsenic Gallium (AGL) lasers cause stimulation of processes of physiological and reparative regeneration in intact skin, and mucous membrane of stomach and duodenum, dermatome wounds and gastroduodenal ulcers. Structural bases of these effects are the acceleration of cell proliferation and differentiation and also the activation of intracellular structures and intensification of cell secretion. Regional influence of the pointed types of LILI on hepar in cirrhosis and hepatitis causes decreasing of the inflammatory and cirrhotic changes. After endo- and exo-vascular laser irradiations of blood the decreasing of the number of pathological forms of erythrocytes and the increasing of their catalase activity, are indicated. General (total) laser irradiation of the organism--laser shower, increases the bone marrow cells proliferation, especially myeloid series. It is accompanied with acceleration of their differentiation and migration in circulation. It was revealed, that HNL to a considerable extent influences the epithelial cells and CVL the connective tissue cells. UVL increases the amount of microorganisms on cell surfaces (membrane bound microorganisms). Regional irradiation of the LILI causes both direct and indirect influence of cells. Structural changes of bone marrow cells and gut mucous membrane cells indicate intersystemic interaction.

  9. Intense short-pulse lasers irradiating wire and hollow plasma fibers.

    PubMed

    Zhou, C T; He, X T; Chew, L Y

    2011-03-15

    When an intense laser pulse irradiates a solid-density foil target, electrons produced at the relativistic critical density can be accelerated to relativistic energy by the ponderomotive force. When a plasma fiber is attached to the back of the foil, the produced relativistic electrons are guided to propagate along the fiber for a long distance, because the high-current electron beam induces strong radial electric fields in the fiber. Transport and heating of intense laser-driven relativistic electrons in both wire and hollow plasma fibers are compared theoretically and numerically. We found that the coupling efficiency from the laser to the plasma fiber depends on the fiber structure. Because of the enhanced return currents in the wire fiber, the temperature in the wire fiber is higher than that in the hollow fiber. PMID:21403730

  10. Photoionization of monocrystalline CVD diamond irradiated with ultrashort intense laser pulse

    NASA Astrophysics Data System (ADS)

    Lagomarsino, Stefano; Sciortino, Silvio; Obreshkov, Boyan; Apostolova, Tzveta; Corsi, Chiara; Bellini, Marco; Berdermann, Eleni; Schmidt, Christian J.

    2016-02-01

    Direct laser writing of conductive paths in synthetic diamond is of interest for implementation in radiation detection and clinical dosimetry. Unraveling the microscopic processes involved in laser irradiation of diamond below and close to the graphitization threshold under the same conditions as the experimental procedure used to produce three-dimensional devices is necessary to tune the laser parameters to optimal results. To this purpose a transient currents technique has been used to measure laser-induced current signals in monocrystalline diamond detectors in a wide range of laser intensities and at different bias voltages. The current transients vs time and the overall charge collected have been compared with theoretical simulations of the carrier dynamics along the duration and after the conclusion of the 30 fs laser pulse. The generated charge has been derived from the collected charge by evaluation of the lifetime of the carriers. The plasma volume has also been evaluated by measuring the modified region. The theoretical simulation has been implemented in the framework of the empirical pseudopotential method extended to include time-dependent couplings of valence electrons to the radiation field. The simulation, in the low-intensity regime, I ˜1 TW /cm2 , predicts substantial deviation from the traditional multiphoton ionization, due to nonperturbative effects involving electrons from degenerate valence bands. For strong field with intensity of about 50 TW /cm2, nonadiabatic effects of electron-hole pair excitation become prominent with high carrier densities eventually causing the optical breakdown of diamond. The comparison of theoretical prediction with experimental data of laser-generated charge vs laser energy density yields a good quantitative agreement over six orders of magnitude. At the highest intensities the change of slope in the trend is explained taking into account the dependence of the optical parameters and the carrier mobility on plasma

  11. Energetic proton beams from plastic targets irradiated by an ultra-intense laser pulse

    NASA Astrophysics Data System (ADS)

    Lee, Kitae; Lee, Ji-Young; Park, Seong Hee; Cha, Yong-Ho; Kim, Kyung-Nam; Jeong, Young Uk

    2011-05-01

    It has been found that more intense proton beams are generated from plastic foils than metal foils irradiated by an ultraintense laser pulse. The acceleration model, ARIE (Acceleration by a Resistively Induced Electric field) accounts for the experimental observations from plastic foils compared with metal foils. Proton beams on foil thickness and laser prepulse have been observed, which is also well described by the ARIE model. An experiment with an aluminum-coated plastic target strongly suggests that front side acceleration is a dominant acceleration process in plastic targets. We also suggest that a vacuum-sandwiched double layer target could effectively enhance the laser contrast ratio, which was investigated in the combination of a two-dimensional hydro code and a two-dimensional PIC (Particle-In-Cell) code.

  12. Size- and intensity-dependent photoelectron spectra from gas-phase gold nanoparticles irradiated by intense femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Powell, J.; Robatjazi, S. J.; Makhija, V.; Vajdi, A.; Li, X.; Malakar, Y.; Pearson, W. L.; Rudenko, A.; Sorensen, C.; Stierle, J.; Kling, M. F.

    2016-05-01

    Nanoparticles bridge the gap between atomic/molecular and bulk matter offering unique opportunities to study light interactions with complex systems, in particular, near-field enhancements and excitation of plasmons. Here we report on a systematic study of photoelectron emission from isolated gold nanoparticles irradiated by 800 nm, 25 fs laser pulses at 10-50 TW/ cm2 peak intensities. A combination of an aerodynamic lens nanoparticle injector, high-energy velocity-map imaging spectrometer and a high-speed, single-shot camera is employed to record shot by shot photoelectron emission patterns from individual particles. By sorting the recorded images according to the number of emitted electrons, we select the events from the regions of particular laser intensities within the laser focus, thus, essentially avoiding focal volume averaging. Using this approach, we study the intensity- and size-dependence of photoelectron energy and angular distributions for particle sizes ranging from 5 nm to 400 nm. This work is supported by NSF Award No. IIA-143049. JRML operations and personal are supported by the Chemical Sciences, Geosciences, and Biosciences Division, Office of BES, Office of Science, U. S. DOE.

  13. The effects of low-intensity laser irradiation on the fatigue induced by dysfunction of mitochondria

    NASA Astrophysics Data System (ADS)

    Xu, Xiao-Yang; Liu, Timon C.; Duan, Rui; Liu, Xiao-Guang

    2003-12-01

    Exercise-induced fatigue has long been an important field in sports medicine. The electron leak of mitochondrial respiratory chain during the ATP synthesis integrated with proton leak and O-.2 can decrease the efficiency of ATP synthesis in mitochondria. And the exercise-induced fatigue occur followed by the decrease of performance. If the dysfunction of mitochondria can be avoided, the fatigue during the exercise may be delayed and the performance may be enhanced. Indeed there are some kind of materials can partially prevent the decrease of ATP synthesis efficiency in mitochondria. But the side effects and safety of these materials is still needed to be studied. Low intensity laser can improve the mitochondria function. It is reasonable to consider that low intensity laser therapy may become the new and more effective way to delay or elimination the fatigue induced by dysfunction of mitochondria. Because the effect of laser irradiation may not be controlled exactly when study in vivo, we use electrical stimulation of C2C12 muscle cells in culture to define the effect of low intensity laser on the dysfunction of mitochondria, and to define the optimal laser intensity to prevent the decrease of ATP synthesis efficiency. Our study use the C2C12 muscle cells in culture to define some of the mechanisms involved in the contractile-induced changes of mitochondrial function firstly in sports medicine and may suggest a useful study way to other researchers. We also give a new way to delay or eliminating the fatigue induced by dysfunction of mitochondria without side effect.

  14. Microwave emission by nonlinear crystals irradiated with a high-intensity, mode-locked laser

    NASA Astrophysics Data System (ADS)

    Borghesani, A. F.; Braggio, C.; Guarise, M.

    2016-06-01

    We report on the experimental investigation of the efficiency of some nonlinear crystals to generate microwave (RF) radiation as a result of optical rectification (OR) when irradiated with intense pulse trains delivered by a mode-locked laser at 1064 nm. We have investigated lithium triborate (LBO), lithium niobate (LiNbO3), zinc selenide (ZnSe), and also potassium titanyl orthophosphate (KTP) for comparison with previous measurements. The results are in good agreement with the theoretical predictions based on the form of the second-order nonlinear susceptibility tensor. For some crystals we investigated also the second harmonic generation (SHG) to cross check the theoretical model. We confirm the theoretical prediction that OR leads to the production of higher order RF harmonics that are overtones of the laser repetition rate.

  15. Properties of metals during the heating by intense laser irradiation using ab initio simulations

    NASA Astrophysics Data System (ADS)

    Holst, Bastian; Recoules, Vanina; Torrent, Marc; Mazevet, Stephane

    2011-10-01

    Ultrashort laser pulses irradiating a target heat the electrons to very high temperatures. In contrast, the ionic lattice is unaffected on the time scale of the laser pulse since the heat capacity of electrons is much smaller than that of the lattice. This non-equilibrium system can be described as a composition of two subsystems: one consisting of hot electrons and the other of an ionic lattice at low temperature. We studied the effect of this intense electronic excitations on the optical properties of gold using ab initio simulations. We additionally use ab initio linear response to compute the phonon spectrum and the electron-phonon coupling constant within Density Functional Theory for several electronic temperatures of few eV. LULI, Ecole Polytechnique, CNRS, CEA, UPMC, 91128 Palaiseau, France.

  16. Ab initio calculation of the thermodynamic properties of InSb under intense laser irradiation

    SciTech Connect

    Feng, ShiQuan; Cheng, XinLu; Key Laboratory of High Energy Density Physics and Technology of Ministry of Education, Sichuan University, Chengdu, 610064 ; Zhao, JianLing; Zhang, Hong

    2013-07-28

    In this paper, phonon spectra of InSb at different electronic temperatures are presented. Based on the phonon dispersion relationship, we further perform a theoretical investigation of the thermodynamic properties of InSb under intense laser irradiation. The phonon entropy, phonon heat capacity, and phonon contribution to Helmholtz free energy and internal energy of InSb are calculated as functions of temperature at different electronic temperatures. The abrupt change in the phonon entropy- temperature curve from T{sub e} = 0.75 to 1.0 eV provides an indication of InSb undergoing a phase transition from solid to liquid. It can be considered as a collateral evidence of non-thermal melting for InSb under intense electronic excitation effect.

  17. Ion heating dynamics in solid buried layer targets irradiated by ultra-short intense laser pulses

    SciTech Connect

    Huang, L. G.; Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden; University of Chinese Academy of Sciences, 100049 Beijing ; Bussmann, M.; Kluge, T.; Lei, A. L.; Yu, W.; Cowan, T. E.; Technische Universität Dresden, 01062 Dresden

    2013-09-15

    We investigate bulk ion heating in solid buried layer targets irradiated by ultra-short laser pulses of relativistic intensities using particle-in-cell simulations. Our study focuses on a CD{sub 2}-Al-CD{sub 2} sandwich target geometry. We find enhanced deuteron ion heating in a layer compressed by the expanding aluminium layer. A pressure gradient created at the Al-CD{sub 2} interface pushes this layer of deuteron ions towards the outer regions of the target. During its passage through the target, deuteron ions are constantly injected into this layer. Our simulations suggest that the directed collective outward motion of the layer is converted into thermal motion inside the layer, leading to deuteron temperatures higher than those found in the rest of the target. This enhanced heating can already be observed at laser pulse durations as low as 100 fs. Thus, detailed experimental surveys at repetition rates of several ten laser shots per minute are in reach at current high-power laser systems, which would allow for probing and optimizing the heating dynamics.

  18. Effects of low-intensity laser irradiation on the apoptosis of rabbit vascular smooth muscle cells in culture

    NASA Astrophysics Data System (ADS)

    Li, S. D.; Chen, P.; Zhang, C. P.; Wen, J. X.; Liang, J.; Kang, H. X.; Gao, R. L.; Fu, X. B.

    2011-11-01

    Restenosis is a major complication after coronary intervention therapy. Excessive proliferation of vascular smooth muscle cells (VSMCs) and a decline in their apoptosis, which eventually leads to excessive neointimal thickening in coronary arteries, are the main causes of restenosis. Induction of the apoptosis of VSMCs and inhibition of excessive proliferation of VSMCs are therefore crucial for the prevention of restenosis, and low-intensity laser irradiation of coronary arteries may play a promising role in keeping this in balance. In this study, we used in vitro cultured rabbit VSMCs to investigate the effects of low-intensity laser irradiation at a wavelength of 532 nm on the apoptosis of VSMCs via morphological observation and molecular biology. The results showed that apoptotic bodies and obvious intranuclear apoptosis-positive particles formed within VSMCs 24 h after laser irradiation, suggesting that low-intensity laser irradiation at certain doses can inhibit the proliferation of VSMCs by promoting their apoptosis. This experiment provides evidences for further animal experiments and clinical trials on prevention and treatment of restenosis by intracoronary low-intensity laser irradiation at a wavelength of 532 nm.

  19. The hematologic effects of low intensity 650 nm laser irradiation on hypercholesterolemia rabbits

    PubMed Central

    Wang, Hong; Deng, Juan; Tu, Wenjun; Zhang, Lin; Chen, Hongli; Wu, Xiaoguang; Li, Yingxin; Sha, Hong

    2016-01-01

    Purpose: To test the hematologic effects of low intensity 650 nm laser irradiation on hypercholesterolemia rabbits. Methods: Ten male big-eared rabbits were selected from hypercholesterolemia animal model-making and divided into model group and laser treatment groups. Five normal rabbits were selected as control group. Auricle root irradiation of 650 nm laser 100 mW in 30 min were applied on treatment group twice a day, treatment of 6 days in one week, 20 weeks course of treatment. Changes in blood lipid, microcirculation, rheological properties, and aggregation morphology of erythrocytes were observed every two weeks. Histopathological examination were performed in the end of experiments. Results: After 20 weeks’ treatment, triglyceride (TG), cholesterol (CHO), high density lipoprotein (HDL) and low density lipoprotein (LDL) of serum in hypercholesterolemia groups showed less changes in the first 4 weeks, butdifferent decreasing trends were shownin the next 16 weeks’ therapy. Erythrocytes aggregation of model groups showed rouleau state, while red blood cells in control group showed fine homodisperse, erythrocytes in treatment group performed better dispersion than model groups. Erythrocyte deformation index (DI) and blood flow value showed a statistic improvement in treatment group than control and model group (P<0.01). Value of DI in treatment group decreased after 18 weeks than values before therapy (P<0.01). Varying degrees of Aorta plaque formation was observed for individual difference in model and treatment groups, while no plaque was found in control group. Conclusions: Low energy laser improve microcirculation, rheological properties and blood lipid that might be related with erythrocytes aggregation and deformability. PMID:27347336

  20. Profiling of genes central to human mitochondrial energy metabolism following low intensity laser irradiation

    NASA Astrophysics Data System (ADS)

    Houreld, Nicolette N.; Masha, Roland; Abrahamse, Heidi

    2012-09-01

    Background: Wound healing involves three overlapping phases: inflammation, granulation and tissue remodelling. If this process is disrupted, delayed wound healing ensues, a common complication seen in diabetic patients. Low intensity laser irradiation (LILI) has been found to promote healing in such patients. However, the exact mechanisms of action are poorly understood. Purpose: This study aimed to profile the expression of key genes involved in mitochondrial respiration. Materials and Methods: Diabetic wounded fibroblast cells were exposed to a wavelength of 660 nm and a fluence of 5 J/cm2 and incubated for 30 min. Total RNA was isolated and 1 μg reverse transcribed into cDNA which was used for real-time polymerase chain reaction (PCR) array analysis. The array contained genes important for each of the mitochondrial complexes involved in the electron transport chain (ETC). Adenosine triphosphate (ATP) levels were also determined post-irradiation by ATP luminescence. Results: Genes involved in complex IV (cytochrome c oxidase), COX6B2 and COX6C, and PPA1 which is involved in complex V (ATP synthase) were significantly up-regulated. There was a significant increase in ATP levels in diabetic wounded cells post-irradiation. Discussion and Conclusion: LILI stimulates the ETC at a transcriptional level, resulting in an increase in ATP. This study helps understand the mechanisms of LILI in diabetic wound healing, and gives information on activation of genes in response to LILI.

  1. Disassembly time of deuterium-cluster-fusion plasma irradiated by an intense laser pulse

    DOE PAGESBeta

    Bang, W.

    2015-07-02

    Energetic deuterium ions from large deuterium clusters (>10 nm diameter) irradiated by an intense laser pulse (>10¹⁶ W/cm²) produce DD fusion neutrons for a time interval determined by the geometry of the resulting fusion plasma. We show an analytical solution of this time interval, the plasma disassembly time, for deuterium plasmas that are cylindrical in shape. Assuming a symmetrically expanding deuterium plasma, we calculate the expected fusion neutron yield and compare with an independent calculation of the yield using the concept of a finite confinement time at a fixed plasma density. The calculated neutron yields agree quantitatively with the availablemore » experimental data. Our one-dimensional simulations indicate that one could expect a tenfold increase in total neutron yield by magnetically confining a 10 - keV deuterium fusion plasma for 10 ns.« less

  2. Disassembly time of deuterium-cluster-fusion plasma irradiated by an intense laser pulse

    SciTech Connect

    Bang, W.

    2015-07-02

    Energetic deuterium ions from large deuterium clusters (>10 nm diameter) irradiated by an intense laser pulse (>10¹⁶ W/cm²) produce DD fusion neutrons for a time interval determined by the geometry of the resulting fusion plasma. We show an analytical solution of this time interval, the plasma disassembly time, for deuterium plasmas that are cylindrical in shape. Assuming a symmetrically expanding deuterium plasma, we calculate the expected fusion neutron yield and compare with an independent calculation of the yield using the concept of a finite confinement time at a fixed plasma density. The calculated neutron yields agree quantitatively with the available experimental data. Our one-dimensional simulations indicate that one could expect a tenfold increase in total neutron yield by magnetically confining a 10 - keV deuterium fusion plasma for 10 ns.

  3. Evidence for ultra-fast heating in intense-laser irradiated reduced-mass targets

    SciTech Connect

    Neumayer, P.; Gumberidze, A.; Hochhaus, D. C.; Aurand, B.; Stoehlker, T.; Costa Fraga, R. A.; Kalinin, A.; Ecker, B.; Grisenti, R. E.; Kaluza, M. C.; Kuehl, T.; Polz, J.; Reuschl, R.; Winters, D.; Winters, N.; Yin, Z.

    2012-12-15

    We report on an experiment irradiating individual argon droplets of 20 {mu}m diameter with laser pulses of several Joule energy at intensities of 10{sup 19} W/cm{sup 2}. K-shell emission spectroscopy was employed to determine the hot electron energy fraction and the time-integrated charge-state distribution. Spectral fitting indicates that bulk temperatures up to 160 eV are reached. Modelling of the hot-electron relaxation and generation of K-shell emission with collisional hot-electron stopping only is incompatible with the experimental results, and the data suggest an additional ultra-fast (sub-ps) heating contribution. For example, including resistive heating in the modelling yields a much better agreement with the observed final bulk temperature and qualitatively reproduces the observed charge state distribution.

  4. Disassembly time of deuterium-cluster-fusion plasma irradiated by an intense laser pulse.

    PubMed

    Bang, W

    2015-07-01

    Energetic deuterium ions from large deuterium clusters (>10nm diameter) irradiated by an intense laser pulse (>10(16)W/cm(2)) produce DD fusion neutrons for a time interval determined by the geometry of the resulting fusion plasma. We present an analytical solution of this time interval, the plasma disassembly time, for deuterium plasmas that are cylindrical in shape. Assuming a symmetrically expanding deuterium plasma, we calculate the expected fusion neutron yield and compare with an independent calculation of the yield using the concept of a finite confinement time at a fixed plasma density. The calculated neutron yields agree quantitatively with the available experimental data. Our one-dimensional simulations indicate that one could expect a tenfold increase in total neutron yield by magnetically confining a 10-keV deuterium fusion plasma for 10ns. PMID:26274289

  5. Generation and Transport of Fast Electrons in Laser Irradiated Targets at Relativistic Intensities

    NASA Astrophysics Data System (ADS)

    Amiranoff, F.; Baton, S. D.; Gremillet, L.; Guilbaud, O.; Koenig, M.; Martinolli, E.; Santos, J. J.; Le Gloahec, M. Rabec; Rousseaux, C.; Hall, T.

    2002-10-01

    The transport of relativistic electrons in solid targets irradiated by a short laser pulse at relativistic intensities has been studied both experimentally and numerically. A Monte-Carlo collision code takes into account individual collisions with the ions and electrons in the target. A 3D-hybrid code takes into account these collisions as well as the generation of electric and magnetic fields and the self-consistent motion of the electrons in these fields. It predicts a magnetic guiding of a fraction of the fast electron current over long distances and a localized heating of the material along the propagation axis. In experiments performed at LULI on the 100 TW laser facility, several diagnostics have been implemented to diagnose the geometry of the fast electron transport and the target heating. The typical conditions were: E1 less-than-or-equal 20 J, lambda = 1 mum, tau approximately 300 fs, I approximately 1018-5.1019W/cm2. The results indicate a modest heating of the target (typically 20-40 eV over 20 mum to 50 mum), consistent with an acceleration of the electrons inside a wide aperture cone along the laser axis.

  6. Theory of absorption rate of carriers in fused silica under intense laser irradiation

    SciTech Connect

    Deng, Hongxiang; Xiang, Xia; Zheng, WG; Yuan, XD; Wu, SY; Jiang, XD; Gao, Fei; Zu, Xiaotao T.; Sun, Kai

    2010-11-15

    A quantum non-perturbation theory for phonon-assisted photon absorption of conduction band electron in intense laser was developed. By carrying out the calculation in fused silica at wavelengths from ultraviolet to infrared in terawatt intensity laser, we show that the Non-perturbation approach can make a uniform description of energy absorption rate at both short wavelengths and long wavelengths on TW / cm2 intensity laser.

  7. Effects of low intensity laser acupoint irradiation on inhibiting islet beta-cell apoptosis in rats with type 2 diabetes

    NASA Astrophysics Data System (ADS)

    Xiong, Guoxin; Xiong, Leilei; Li, Xinzhong

    2016-09-01

    To investigate the effects of low intensity semiconductor laser acupoint irradiation on inhibiting islet beta-cell apoptosis in rats with type 2 diabetes, a method using a high-fat diet and low-dose intraperitoneal injections of streptozotocin established a type 2 diabetes mellitus rat model. Model rats were randomly divided into a laser acupoint irradiation group, rosiglitazone control group, and placebo group; each group had 10 rats. In addition, 10 normal male rats were selected for the normal control group. The Housanli, Neiting and Yishu acupoints of the rats in the laser acupoint irradiation group were irradiated with a 10 mW semiconductor laser; each point was irradiated for 15 min, once every 2 d over 28 d, for a total of 14 episodes of irradiation. The rosiglitazone group rats were given rosiglitazone (0.2 mg kg‑1) intragastrically; the placebo group rats were given 0.9% brine (0.2 mg kg‑1) intragastrically, once daily, for four consecutive weeks. The change of fasting blood glucose was determined before and after each treatment. The islet beta-cell apoptosis was determined. The islet beta-cell apoptosis rates of the laser acupoint irradiation group and the rosiglitazone group were significantly lower than the rate of the placebo group. Even though the rate was lower in the laser acupoint irradiation group than in the rosiglitazone group, there was no significant difference between them. It is shown that acupoint irradiation with a semiconductor laser can effectively inhibit islet beta-cell apoptosis in rats with type 2 diabetes.

  8. [Morphometric differences in the normal and low-intensity laser-irradiated spinal neurons of the cat].

    PubMed

    Rusakov, D A; Klering, P G; Savich, V I

    1987-01-01

    Structural parameters of neurons of normal and low-intensity Ge-Ne laser irradiated cat spinal cords were investigated by the morphometrical technique. Observed statistical alterations of the soma volume and nuclear surface values as well as cellular nuclear space relations were associated with the evoked changes in the cell metabolism. PMID:3448495

  9. Temperature distribution in biotissues under cw low-intensity laser irradiation

    NASA Astrophysics Data System (ADS)

    Yakunin, Alexander N.; Scherbakov, Yury N.; Tuchin, Valery V.; Utz, Sergei R.; Yaroslavsky, Ilya V.

    1992-08-01

    The Monte Carlo method of statistical simulations was used to evaluate the effects of anisotropic scattering and refractive index mismatch at the boundaries of the medium on light and temperature distribution in the multilayered biotissues during laser irradiation. The influence of optical parameters of multilayered tissue on its stationary thermal response was examined by using an adaptive version of finite element solution of the heat conduction equation. Calculations were performed for two models of human skin and adjacent tissues for visible (five layer model) and UV (three layer model) ranges of wavelengths. The topic of this paper is especially pertinent to laser percutaneous irradiation of blood and laser PUVA therapy.

  10. Analysis of strained surface layers of ZnO single crystals after irradiation with intense femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Schneider, Andreas; Wolverson, Daniel; Sebald, Kathrin; Hodges, Chris; Kuball, Martin; Voss, Tobias

    2013-05-01

    Structural modifications of ZnO single crystals that were created by the irradiation with femtosecond laser pulses at fluences far above the ablation threshold were investigated with micro-Raman spectroscopy. After light-matter interaction on the femtosecond time scale, rapid cooling and the pronounced thermal expansion anisotropy of ZnO are likely to cause residual strains of up to 1.8% and also result in the formation of surface cracks. This process relaxes the strain only partially and a strained surface layer remains. Our findings demonstrate the significant role of thermoelastic effects for the irradiation of solids with intense femtosecond laser pulses.

  11. Dynamics of rare gas nanoclusters irradiated by short and intense laser pulses

    NASA Astrophysics Data System (ADS)

    Micheau, S.; Bonté, C.; Dorchies, F.; Fourment, C.; Harmand, M.; Jouin, H.; Peyrusse, O.; Pons, B.; Santos, J. J.

    2007-05-01

    We report on a joint experimental-theoretical effort to shed light on the dynamics of rare gas (Ar) nanoclusters irradiated by short and intense laser pulses. The experiments employ a streak camera coupled to a conical crystal to yield energy- and time-resolved X-ray spectra, in the keV range on picosecond scale. These spectra display ultrafast subpicosecond ionization dynamics, leading to highly charged states such as Ar 16+, and indicate that the duration of the energetic X-rays is less than the experimental 1.3 ps temporal resolution. The theoretical calculations rely on the well-known nanoplasma model, which has been improved to represent the collisional ionization processes that are of importance in nanoplasma dynamics. Allowance is made for high-order ionization transitions involving intermediate excited states. The simulations indicate significant populations of excited states of highly charged ions, in agreement with the experimental findings. Further, detailed collisional-radiative calculations indicate that the duration of the X-ray bursts is less than 100 fs.

  12. Biochemical responses of isolated lung CSCs after application of low intensity laser irradiation

    NASA Astrophysics Data System (ADS)

    Abrahamse, Heidi; Crous, Anine

    2016-03-01

    Studies have shown that using high fluences of Low Intensity Laser Irradiation (HF-LILI) produce apoptotic effects on normal and neoplastic cells. This study aimed to determine whether HF-LILI induce cell death in lung CSCs. Lung CSCs were isolated using the stem cell marker CD 133, characterized using flow cytometry, and applied in experiments which included treatment with LILI at wavelengths of 636, 825 and 1060 nm with fluences ranging from 5 J/cm2 to 40 J/cm2. Viability and proliferation studies, using Alamar blue assay and adenosine triphosphate luminescence (ATP), indicated an increase when treating lung CSCs with low fluences of 5 - 20 J/cm2 and a decrease in viability and proliferation as well as an increase in apoptosis when applying a fluence of 40 J/cm2 indicated by flow cytometry using Annexin V and propidium iodide (PI) dyes. Results indicate that LILI, when treating lung CSCs, can induce either a bio-stimulatory or bio-inhibitory effect depending on the wavelength and fluence used. This study indicated successful apoptotic induction of lung CSCs. Future experiments should be able to conclude the exact mechanism behind HF-LILI, which can be used in the targeted treatments of CSC elimination, implementing HF-LILI in the same manner as PDT in the absence of a photosensitizer.

  13. Ablation and transmission of thin solid targets irradiated by intense extreme ultraviolet laser radiation

    NASA Astrophysics Data System (ADS)

    Aslanyan, V.; Kuznetsov, I.; Bravo, H.; Woolston, M. R.; Rossall, A. K.; Menoni, C. S.; Rocca, J. J.; Tallents, G. J.

    2016-09-01

    The interaction of an extreme ultraviolet (EUV) laser beam with a parylene foil was studied by experiments and simulation. A single EUV laser pulse of nanosecond duration focused to an intensity of 3 × 1010 W cm-2 perforated micrometer thick targets. The same laser pulse was simultaneously used to diagnose the interaction by a transmission measurement. A combination of 2-dimensional radiation-hydrodynamic and diffraction calculations was used to model the ablation, leading to good agreement with experiment. This theoretical approach allows predictive modelling of the interaction with matter of intense EUV beams over a broad range of parameters.

  14. LASER METHODS IN MEDICINE: Light absorption in blood during low-intensity laser irradiation of skin

    NASA Astrophysics Data System (ADS)

    Barun, V. V.; Ivanov, A. P.

    2010-06-01

    An analytical procedure is proposed for describing optical fields in biological tissues inhomogeneous in the depth direction, such as human skin, with allowance for multiple scattering. The procedure is used to investigate the depth distribution of the optical power density in homogeneous and multilayer dermis when the skin is exposed to a laser beam. We calculate the absorbed laser power spectra for oxy- and deoxyhaemoglobin at different depths in relation to the absorption selectivity of these haemoglobin derivatives and the spectral dependence of the optical power density and demonstrate that the spectra vary considerably with depth. A simple exponential approximation is proposed for the depth distribution of the power density in the epidermis and dermis.

  15. Nonlocal electron transport in the presence of high-intensity laser irradiation

    SciTech Connect

    Epperlein, E.M.; Short, R.W. )

    1994-08-01

    We investigate electron transport in a plasma heated by spatially modulated laser irradiation. When the heating rate is greater than the electron-electron collision rate, the thermal conductivity is reduced by a factor of 3 to 4 from the Spitzer-Haerm [Phys. Rev. 89, 977 (1953)] value for [ital K][lambda][sub [ital e

  16. Resonant absorption and not-so-resonant absorption in short, intense laser irradiated plasma

    SciTech Connect

    Ge, Z. Y.; Zhuo, H. B.; Ma, Y. Y.; Yang, X. H.; Yu, T. P.; Zou, D. B.; Yin, Y.; Shao, F. Q.; Yu, W.; Luan, S. X.; Zhou, C. T.; Institute of Applied Physics and Computational Mathematics, Beijing 100088 ; Peng, X. J.

    2013-07-15

    An analytical model for laser-plasma interaction during the oblique incidence by an ultrashort ultraintense p-polarized laser on a solid-density plasma is proposed. Both the resonant absorption and not-so-resonant absorption are self-consistently included. Different from the previous theoretical works, the physics of resonant absorption is found to be valid in more general conditions as the steepening of the electron density profile is considered. Even for a relativistic intensity laser, resonant absorption can still exist under certain plasma scale length. For shorter plasma scale length or higher laser intensity, the not-so-resonant absorption tends to be dominant, since the electron density is steepened to a critical level by the ponderomotive force. The laser energy absorption rates for both mechanisms are discussed in detail, and the difference and transition between these two mechanisms are presented.

  17. A first principles study of the lattice stability of diamond-structure semiconductors under intense laser irradiation

    SciTech Connect

    Feng Shiquan; Zhao Jianling; Cheng Xinlu

    2013-01-14

    Using density-functional linear-response theory, we calculated the phonon dispersion curves for the diamond structural elemental semiconductors of Ge, C and zinc-blende structure semiconductors of GaAs, InSb at different electronic temperatures. We found that the transverse-acoustic phonon frequencies of C and Ge become imaginary as the electron temperature is elevated, which means the lattices of C and Ge become unstable under intense laser irradiation. These results are very similar with previous theoretical and experimental results for Si. For GaAs and InSb, not only can be obtained the similar results for their transverse-acoustic modes, but also their LO-TO splitting gradually decreases as the electronic temperature is increased. It means that the electronic excitation weakens the strength of the ionicity of ionic crystal under intense laser irradiation.

  18. [The use of ozone and low-intensive laser irradiation in complex treatment of complicated duodenal ulcer].

    PubMed

    Mamedov, R A; Agamirova, A N; Dadashev, A I; Gasymov, É M; Kurbanov, F S; Dobrovol'skiĭ, S R

    2011-01-01

    The study is based on the examination of 12 patients with perforative duodenal ulcer and 24 patients operated on recurrent bleeding duodenal ulcer. Some component of the immune system, such as T- and B-lymphocytes rates, immunoglobulin rate and macrophagal activity, were decreased prior the beginning of the complex treatment. Normalisation of humoral and cell immunity was registered on 10-12 days after the beginning of the ozone and low-intensive laser irradiation. PMID:21983535

  19. Energy absorption of free rare gas clusters irradiated by intense VUV pulses of a free electron laser

    NASA Astrophysics Data System (ADS)

    Schulz, J.; Wabnitz, H.; Laarmann, T.; Gürtler, P.; Laasch, W.; Swiderski, A.; Möller, Th.; de Castro, A. R. B.

    2003-07-01

    As one of the first experiments at the free electron laser of the TESLA Test Facility (TTF) the Coulomb explosion of Xenon clusters irradiated with high intensity pulses at a wavelength of 98 nm has been observed. Classical trajectory calculations have been performed in order to illuminate the energy absorption process. Comparison with typical parameters in the infrared regime shows that above barrier ionization is suppressed due to the fast oscillating field and thermionic ionization prevails.

  20. Intensity Scalings of Attosecond Pulse Generation by the Relativistic-irradiance Laser Pulses

    NASA Astrophysics Data System (ADS)

    Pirozhkov, Alexander S.; Bulanov, Sergei V.; Esirkepov, Timur Zh.; Sagisaka, Akito; Tajima, Toshiki; Daido, Hiroyuki

    We present the theoretical comparative analysis of different attosecond pulse generation techniques in which the relativistic-irradiance driver pulses are used. In particular, we concentrate on the intensity scalings of the attosecond pulse duration, wavelength, and conversion efficiency. We also discuss the optimum conditions and the major implementation challenges.

  1. Terahertz radiation from a wire target irradiated by an ultra-intense laser pulse

    SciTech Connect

    Li Zhichao; Zheng Jian

    2007-05-15

    When an ultra-intense laser pulse impacts the tip of a wire whose other end is grounded, a strong return current can be driven along the wire because some energetic electrons generated in ultra-intense laser matter interaction can escape from the target and an electric field builds up. The wire then behaves like a current-carrying antenna that can emit electromagnetic radiations. If the duration of the driving pulse is several tens of femtoseconds, the radiation spectrum reaches a maximum at terahertz region, and the radiation power per solid angle could be as high as 10{sup 9} W/rad.

  2. High-flux low-divergence positron beam generation from ultra-intense laser irradiated a tapered hollow target

    SciTech Connect

    Liu, Jian-Xun; Ma, Yan-Yun; Zhao, Jun; Yu, Tong-Pu Yang, Xiao-Hu; Gan, Long-Fei; Zhang, Guo-Bo; Yan, Jian-Feng; Zhuo, Hong-Bin; Liu, Jin-Jin; Zhao, Yuan; Kawata, Shigeo

    2015-10-15

    By using two-dimensional particle-in-cell simulations, we demonstrate high-flux dense positrons generation by irradiating an ultra-intense laser pulse onto a tapered hollow target. By using a laser with an intensity of 4 × 10{sup 23 }W/cm{sup 2}, it is shown that the Breit-Wheeler process dominates the positron production during the laser-target interaction and a positron beam with a total number >10{sup 15} is obtained, which is increased by five orders of magnitude than in the previous work at the same laser intensity. Due to the focusing effect of the transverse electric fields formed in the hollow cone wall, the divergence angle of the positron beam effectively decreases to ∼15° with an effective temperature of ∼674 MeV. When the laser intensity is doubled, both the positron flux (>10{sup 16}) and temperature (963 MeV) increase, while the divergence angle gets smaller (∼13°). The obtained high-flux low-divergence positron beam may have diverse applications in science, medicine, and engineering.

  3. High-flux low-divergence positron beam generation from ultra-intense laser irradiated a tapered hollow target

    NASA Astrophysics Data System (ADS)

    Liu, Jian-Xun; Ma, Yan-Yun; Zhao, Jun; Yu, Tong-Pu; Yang, Xiao-Hu; Gan, Long-Fei; Zhang, Guo-Bo; Yan, Jian-Feng; Zhuo, Hong-Bin; Liu, Jin-Jin; Zhao, Yuan; Kawata, Shigeo

    2015-10-01

    By using two-dimensional particle-in-cell simulations, we demonstrate high-flux dense positrons generation by irradiating an ultra-intense laser pulse onto a tapered hollow target. By using a laser with an intensity of 4 × 1023 W/cm2, it is shown that the Breit-Wheeler process dominates the positron production during the laser-target interaction and a positron beam with a total number >1015 is obtained, which is increased by five orders of magnitude than in the previous work at the same laser intensity. Due to the focusing effect of the transverse electric fields formed in the hollow cone wall, the divergence angle of the positron beam effectively decreases to ˜15° with an effective temperature of ˜674 MeV. When the laser intensity is doubled, both the positron flux (>1016) and temperature (963 MeV) increase, while the divergence angle gets smaller (˜13°). The obtained high-flux low-divergence positron beam may have diverse applications in science, medicine, and engineering.

  4. Enhanced dense attosecond electron bunch generation by irradiating an intense laser on a cone target

    SciTech Connect

    Hu, Li-Xiang; Yu, Tong-Pu Shao, Fu-Qiu; Zou, De-Bin; Yin, Yan

    2015-03-15

    By using two-dimensional particle-in-cell simulations, we demonstrate enhanced spatially periodic attosecond electron bunches generation with an average density of about 10n{sub c} and cut-off energy up to 380 MeV. These bunches are acquired from the interaction of an ultra-short ultra-intense laser pulse with a cone target. The laser oscillating field pulls out the cone surface electrons periodically and accelerates them forward via laser pondermotive force. The inner cone wall can effectively guide these bunches and lead to their stable propagation in the cone, resulting in overdense energetic attosecond electron generation. We also consider the influence of laser and cone target parameters on the bunch properties. It indicates that the attosecond electron bunch acceleration and propagation could be significantly enhanced without evident divergency by attaching a plasma capillary to the original cone tip.

  5. Enhanced dense attosecond electron bunch generation by irradiating an intense laser on a cone target

    NASA Astrophysics Data System (ADS)

    Hu, Li-Xiang; Yu, Tong-Pu; Shao, Fu-Qiu; Zou, De-Bin; Yin, Yan

    2015-03-01

    By using two-dimensional particle-in-cell simulations, we demonstrate enhanced spatially periodic attosecond electron bunches generation with an average density of about 10nc and cut-off energy up to 380 MeV. These bunches are acquired from the interaction of an ultra-short ultra-intense laser pulse with a cone target. The laser oscillating field pulls out the cone surface electrons periodically and accelerates them forward via laser pondermotive force. The inner cone wall can effectively guide these bunches and lead to their stable propagation in the cone, resulting in overdense energetic attosecond electron generation. We also consider the influence of laser and cone target parameters on the bunch properties. It indicates that the attosecond electron bunch acceleration and propagation could be significantly enhanced without evident divergency by attaching a plasma capillary to the original cone tip.

  6. Multielectron dissociative ionization of CH3I clusters under moderate intensity ps laser irradiation

    NASA Astrophysics Data System (ADS)

    Karras, G.; Kosmidis, C.

    2010-02-01

    The interaction of 35 ps laser pulses with methyl iodide clusters in the intensity region of 1012-3 × 1013 W/cm2 is studied at [lambda] = 266, 532 and 1064 nm by means of time-of-flight mass spectrometry. At [lambda] = 532 and 1064 nm the multielectron dissociative ionization (MEDI) of clusters results in highly charged atomic fragment (up to I7+) ion production of high kinetic energy. The explosion of the multiple charged cluster ions is found to be isotropic, while an asymmetric charge distribution prior to their fragmentation is observed. Moreover, negative ion formation is observed. The MEDI of clusters exhibits a dependence on laser polarization and the intensity thresholds for the observation of the fragment ions are determined for linear and circular laser polarization. These intensity thresholds are found to be about three orders of magnitude lower than those reported by experiments with 35 ps laser pulses on CH3I monomers. For the observed MEDI of (CH3I)n clusters a mechanism is proposed. According to this mechanism, the clusters are initially single ionized by multiphoton absorption and an internal electric field is created within the cluster, which distorts the potential barriers. This distortion increases the probability for electron tunneling even at relatively low laser intensities, giving thus rise to the formation of negatively charged moieties within the clusters, which prevent the cluster elongation and facile further the tunneling process. This procedure results in a higher distortion of the internal barriers and an increased ionization of the clusters, which, due to increased repulsive forces, finally fragment leading to multiple charged high kinetic energy fragment ion production.

  7. Emission of Thermally Activated Electrons from Rare Gas Clusters Irradiated with Intense VUV Light Pulses from a Free Electron Laser

    SciTech Connect

    Laarmann, T.; Rusek, M.; Schulz, J.; Castro, A.R.B. de; Guertler, P.; Laasch, W.; Moeller, T.

    2005-08-05

    The ionization dynamics of Ar and Xe clusters irradiated with intense vacuum ultraviolet light from a free-electron laser is investigated using photoelectron spectroscopy. Clusters comprising between 70 and 900 atoms were irradiated with femtosecond pulses at 95 nm wavelength ({approx}13 eV photon energy) and a peak intensity of {approx}4x10{sup 12} W/cm{sup 2}. A broad thermal distribution of emitted electrons from clusters with a maximum kinetic energy up to 30-40 eV is observed. The observation of relatively low-energy photoelectrons is in good agreement with calculations using a time-dependent Thomas-Fermi model and gives experimental evidence of an outer ionization process of the clusters, due to delayed thermoelectronic emission.

  8. Transient charge dynamics in argon-cluster nanoplasmas created by intense extreme-ultraviolet free-electron-laser irradiation

    NASA Astrophysics Data System (ADS)

    Iwayama, H.; Harries, J. R.; Shigemasa, E.

    2015-02-01

    We present extreme-ultraviolet (EUV) fluorescence spectra of Ar clusters irradiated by intense EUV free-electron-laser (FEL) pulses focused to intensities of up to 3 ×1013W /cm2 at a wavelength of 51 nm. The spectra reveal fluorescence at wavelengths shorter than that of the incident radiation, which can be assigned to EUV fluorescence lines from excited multiply charged ions A rz +* with z as high as 6. This demonstrates that charge states as high as 7+ are produced by the FEL irradiation. The dependence of the spectra on cluster size shows that the highly charged ions are generated at the cluster surface, indicating inhomogeneous charging. The FEL power dependencies of the spectral features suggest that the inhomogeneous distribution of charge within the clusters reduces ionization thresholds at the cluster surface.

  9. Simulation of generation of bremsstrahlung gamma quanta upon irradiation of thin metal films by ultra-intense femtosecond laser pulses

    SciTech Connect

    Andreev, Stepan N; Rukhadze, Anri A; Garanin, Sergey G; Yakutov, B P; Tarakanov, V P

    2010-06-23

    We report the results of simulations of generation of bremsstrahlung gamma quanta upon irradiation of a thin-film metal target by ultra-intense femtosecond laser pulses. It is shown by the example of a thin gold target that the mean electron energy is twenty five times higher than the mean energy of gamma quanta generated by them. A simple approximating formula is proposed, which establishes a one-to-one relation between these quantities. The angular distributions of electrons and gamma quanta are studied. It is shown that only the angular distribution of high-energy gamma quanta repeats the angular distribution of the electrons leaving the target. (interaction of laser radiation with matter. laser plasma)

  10. Enhancement of Efficiency of XUV Generation in Atomic Gases Irradiated by Intense Laser Fields

    NASA Astrophysics Data System (ADS)

    Andreev, A. V.; Stremoukhov, S. Y.; Shoutova, O. A.

    We present the results of the theoretical study of the high-order harmonic generation (HHG) in atomic gases. It is shown that the photoemission spectra exhibit unusual behavior when the laser field strength approaches near-atomic values. In subatomic field strength the cut-off frequency increases linearly with laser pulse intensity. However, when the field strength approaches near-atomic region firstly cut-off frequency slows down and then saturates. To interpret such kind of photoemission spectrum behavior we have proposed the light-atom interaction theory based on the use of eigenfunctions of boundary value problem for "an atom in the external field" instead of the traditional basis of the "free atom" eigenfunctions.

  11. Effects of laser-plasma interactions on terahertz radiation from solid targets irradiated by ultrashort intense laser pulses

    SciTech Connect

    Li Chun; Zhou Mulin; Ding Wenjun; Du Fei; Liu Feng; Li Yutong; Wang Weimin; Ma Jinglong; Chen Liming; Lu Xin; Dong Quanli; Wang Zhaohua; Wei Zhiyi; Sheng Zhengming; Zhang Jie; Lou Zheng; Shi Shengcai

    2011-09-15

    Interactions of 100-fs laser pulses with solid targets at intensities of 10{sup 18} W/cm{sup 2} and resultant terahertz (THz) radiation are studied under different laser contrast ratio conditions. THz emission is measured in the specular reflection direction, which appears to decrease as the laser contrast ratio varies from 10{sup -8} to 10{sup -6}. Correspondingly, the frequency spectra of the reflected light are observed changing from second harmonic dominant, three-halves harmonic dominant, to vanishing of both harmonics. Two-dimensional particle-in-cell simulation also suggests that this observation is correlated with the plasma density scale length change. The results demonstrate that the THz emission is closely related to the laser-plasma interaction processes. The emission is strong when resonance absorption is a key feature of the interaction, and becomes much weaker when parametric instabilities dominate.

  12. Ion acceleration in shell cylinders irradiated by a short intense laser pulse

    SciTech Connect

    Andreev, A.; Platonov, K.; Sharma, A.; Murakami, M.

    2015-09-15

    The interaction of a short high intensity laser pulse with homo and heterogeneous shell cylinders has been analyzed using particle-in-cell simulations and analytical modeling. We show that the shell cylinder is proficient of accelerating and focusing ions in a narrow region. In the case of shell cylinder, the ion energy exceeds the ion energy for a flat target of the same thickness. The constructed model enables the evaluation of the ion energy and the number of ions in the focusing region.

  13. Spectral analysis of x-ray emission created by intense laser irradiation of copper materials

    SciTech Connect

    Huntington, C. M.; Kuranz, C. C.; Drake, R. P.; Malamud, G.; Park, H.-S.; Maddox, B. R.

    2012-10-15

    We have measured the x-ray emission, primarily from K{sub {alpha}},K{sub {beta}}, and He{sub {alpha}} lines, of elemental copper foil and 'foam' targets irradiated with a mid-10{sup 16} W/cm{sup 2} laser pulse. The copper foam at 0.1 times solid density is observed to produce 50% greater He{sub {alpha}} line emission than copper foil, and the measured signal is well-fit by a sum of three synthetic spectra generated by the atomic physics code FLYCHK. Additionally, spectra from both targets reveal characteristic inner shell K{sub {alpha}} transitions from hot electron interaction with the bulk copper. However, only the larger-volume foam target produced significant K{sub {beta}} radiation, confirming a lower bulk temperature in the higher volume sample.

  14. Intravascular low-intensity He-Ne laser irradiation therapy on idiopathic edema

    NASA Astrophysics Data System (ADS)

    Gao, Yunqing; Liu, T. C.; Tang, Xiang-Jun

    1998-11-01

    194 patients with psoriasis were treated by intravascular low level laser irradiation combined with Vit C 2.0g iv and O2 inhale to the nose. An hour once a day, for 5-40 times, and 13.06 times in average, ten times with 4-7 days intervals. The results: cured 23 cases, good effected 61 cases, improved 110 cases, relapsed 10 cases. Curative effect was related to treatment times, cured and good effected 5 times 12.5 percent, 10 times 31 percent, 15 times 94 percent. A matched control group in 17 patients was treated by drug. The results: good effected 1 case, improved 13 cases, not effected 3 cases.

  15. Hot Electron and X-ray Production from Intense Laser Irradiation of Wavelength-scale Polystyrene Spheres

    NASA Astrophysics Data System (ADS)

    Ditmire, T.; Sumeruk, H. A.; Kneip, S.; Symes, D. R.; Churina, I. V.; Belolipetski, A. V.; Dyer, G.; Bernstein, A.; Donnelly, T. D.

    2008-04-01

    In an attempt to control the electric fields at the surface of a high intensity solid target we have studied hot electron generation and x-ray production from targets coated with microspheres. This work is motivated by the possibility that spheres with size comparable to the wavelength of the incident laser radiation can result in electric field enhancements through well know Mie resonances. This local field enhancement can then lead to more efficient electron generation. We investigated hard x-ray (above 100 keV) generation from copper and fused silica targets coated with a monolayer covering of polystyrene microspheres. We performed the experiment using the 20 TW THOR laser system at the University of Texas. We frequency doubled the laser to improve temporal contrast and irradiated the spheres with 400 nm pulses at an intensity of 2 x 1017 W/cm2. Hard X-ray emission from the plasma was observed using filtered NaI scintillation detectors and K-alpha emission was measured with a Von Hamos spectrometer. We illuminated polystyrene spheres of diameters 0.1 -2.9 microns on a glass substrate, with the 400 nm 100fs pulse, and find that there is a clear Mie enhancement in the field and hot electron generation for a specific range of sphere sizes.

  16. Stopping and Coulomb explosion of energetic carbon clusters in a plasma irradiated by an intense laser field

    NASA Astrophysics Data System (ADS)

    Wang, Guiqiu; Wang, Younian

    2015-09-01

    The interaction of a charged particle beam with a plasma is a very important subject of relevance for many fields of physics, such as inertial confinement fusion (ICF) driven by ion or electron beams, high energy density physics, and related astrophysical problems. Recently, a promising ICF scheme has been proposed, in which the plasma target is irradiated simultaneously by intense laser and ion beams. For molecular ion or cluster, slowing down process will company the Coulomb explosion phenomenon. In this paper, we present a study of the effects of intense radiation field (RF) on the interaction of energetic carbon clusters in a plasma. The emphasis is laid on the dynamic polarization and correlation effects of the constituent ions within the cluster in order to disclose the role of the vicinage effects on the Coulomb explosion and energy deposition of the clusters in plasma. On the other hand, affecting of a strong laser field on the cluster propagating in plasma is considered, the influence of a large range of laser parameters and plasma parameters on the Coulomb explosion and stopping power are discussed. This work is supported by the National Natural Science Foundation of China (11375034), and the Fundamental Research Funds for the Central Universities of China (3132015144, 3132014337).

  17. Dynamics and structure of self-generated magnetics fields on solids following high contrast, high intensity laser irradiation

    SciTech Connect

    Albertazzi, B.; Chen, S. N.; Fuchs, J.; Antici, P.; Böker, J.; Swantusch, M.; Willi, O.; Borghesi, M.; Breil, J.; Feugeas, J. L.; Nicolaï, Ph.; Tikhonchuk, V. T.; D'Humières, E.; Dervieux, V.; Nakatsutsumi, M.; Romagnagni, L.; Lancia, L.; Shepherd, R.; Sentoku, Y.; Starodubtsev, M.; and others

    2015-12-15

    The dynamics of self-generated magnetic B-fields produced following the interaction of a high contrast, high intensity (I > 10{sup 19 }W cm{sup −2}) laser beam with thin (3 μm thick) solid (Al or Au) targets is investigated experimentally and numerically. Two main sources drive the growth of B-fields on the target surfaces. B-fields are first driven by laser-generated hot electron currents that relax over ∼10–20 ps. Over longer timescales, the hydrodynamic expansion of the bulk of the target into vacuum also generates B-field induced by non-collinear gradients of density and temperature. The laser irradiation of the target front side strongly localizes the energy deposition at the target front, in contrast to the target rear side, which is heated by fast electrons over a much larger area. This induces an asymmetry in the hydrodynamic expansion between the front and rear target surfaces, and consequently the associated B-fields are found strongly asymmetric. The sole long-lasting (>30 ps) B-fields are the ones growing on the target front surface, where they remain of extremely high strength (∼8–10 MG). These B-fields have been recently put by us in practical use for focusing laser-accelerated protons [B. Albertazzi et al., Rev. Sci. Instrum. 86, 043502 (2015)]; here we analyze in detail their dynamics and structure.

  18. SPECT study of low intensity He-Ne laser intravascular irradiation therapy for brain infarction

    NASA Astrophysics Data System (ADS)

    Xiao, Xue-Chang; Dong, Jia-Zheng; Chu, Xiao-Fan; Jia, Shao-Wei; Liu, Timon C.; Jiao, Jian-Ling; Zheng, Xi-Yuan; Zhou, Ci-Xiong

    2003-12-01

    We used single photon emission computed tomography (SPECT) in brain perfusion imaging to study the changes of regional cerebral blood flow (rCBF) and cerebral function in brain infarction patients treated with intravascular laser irradiation of blood (ILIB). 17 of 35 patients with brain infarction were admitted to be treated by ILIB on the base of standard drug therapy, and SPECT brain perfusion imaging was performed before and after ILIB therapy with self-comparison. The results were analyzed in quantity with brain blood flow function change rate (BFCR%) model. Effect of ILIB during the therapy process in the other 18 patients were also observed. In the 18 patients, SPECT indicated an improvement of rCBF (both in focus and in total brain) and cerebral function after a 30 min-ILIB therapy. And the 17 patients showed an enhancement of total brain rCBF and cerebral function after ILIB therapy in comparison with that before, especially for the focus side of the brain. The enhancement for focus itself was extremely obvious with a higher significant difference (P<0.0001). The mirror regions had no significant change (P>0.05). BFCR% of foci was prominently higher than that of mirror regions (P<0.0001). In conclusion, the ILIB therapy can improve rCBF and cerebral function and activate brain cells of patients with brain infarction. The results denote new evidence of ILIB therapy for those patients with cerebral ischemia.

  19. Quasi-monoenergetic proton beam from a proton-layer embedded metal foil irradiated by an intense laser pulse

    NASA Astrophysics Data System (ADS)

    Kim, Kyung Nam; Lee, Kitae; Kumar, Manoj; Kim, Ha-Na; Park, Seong Hee; Jeong, Young Uk; Vinokurov, Nikolay; Kim, Yong Gi

    2016-03-01

    A target structure, ion-layer embedded foil (ILEF) is proposed for producing a quasi-monoenergetic proton beam by utilizing a bulk electrostatic field, which is generated by irradiating the target with an ultra-intense laser pulse, inside the plasma. Compared with the case of a single metal foil in which the proton layer is initially present on the surface, in the ILEF target, the proton layer is initially located inside a metal foil. A two-dimensional particle-in-cell (PIC) simulation shows that the target generates a proton beam with a narrow energy spread. With a laser intensity of 2 × 1019 W/cm2, a 22-MeV proton beam with an energy spread of 8% at the full-width-half-maximum (FWHM) is obtained when the proton layer is located at 0.4 μm inside the rear surface of a 2.4 μm-thick copper foil. When the proton layer moves toward the front side, a proton beam with a flat-top energy distribution ranging from 15 MeV to 35 MeV is obtained. Further, with a higher laser intensity of 1021 W/cm2, a proton beam with the maximum energy of 345 MeV and FWHM energy spread of 7.2% is obtained. The analysis of the PIC simulation with an aid of a fluid analysis shows that the spectrum is affected by the initial position of the proton layer, its initial spread during the formation of the sheath field, and the space charge effect.

  20. Effect of He-Ne laser irradiation and low-intensity millimeter waves on transplanted tumor growth

    NASA Astrophysics Data System (ADS)

    Brill, Gregory E.; Panina, Nadezda P.

    1995-01-01

    In experiments on white rats the influence of He-Ne laser radiation ((lambda) -- 632.8 nm, power density -- 1.5 mW/cm2) and electromagnetic field of extremely high frequency (42.0 - 43.3 GHz, 1 mW/cm2) on transplantability and growth of fibroadenomas of mammary glands, and influence of low power laser irradiation on transplantability and growth of Walker carcinosarcoma were investigated. Skin at the site of future transplantation underwent irradiation. He-Ne laser and EHF-radiation were stated to change properties of tissue accepting tumor cells. A single laser irradiation of the inoculation site of Walker carcinosarcoma cells produced no effect on tumor transplantability, but increased the average life span of animals. Laser and EHF irradiation increase the transplantability of fibroadeonomas but depress growth and rate of multiplication of tumor cells.

  1. Adaptation and penetration of resin-based root canal sealers in root canals irradiated with high-intensity lasers

    NASA Astrophysics Data System (ADS)

    Moura-Netto, Cacio; Mello-Moura, Anna Carolina Volpi; Palo, Renato Miotto; Prokopowitsch, Igor; Pameijer, Cornelis H.; Marques, Marcia Martins

    2015-03-01

    This research analyzed the quality of resin-based sealer adaptation after intracanal laser irradiation. Extracted teeth (n=168) were root canal treated and divided into four groups, according to dentin surface treatment: no laser; Nd:YAG laser (1.5 W, 100 mJ, 15 Hz) diode laser (2.5 W in CW), and Er:YAG laser (1 W, 100 mJ, 10 Hz). The teeth were divided into four subgroups according to the sealer used: AH Plus, EndoREZ, Epiphany, and EpiphanySE. For testing the sealing after root canal obturation, the penetration of silver nitrate solution was measured, whereas to evaluate the adaptation and penetration of the sealer into the dentin, environmental scanning electron microscopy (ESEM) was used. The ESEM images were analyzed using a four-grade criteria score by three evaluators. The inter-examiner agreement was confirmed by Kappa test and the scores statistically compared by the Kruskal-Wallis' test (p<0.05). Both adaptation and sealer penetration in root canals were not affected by the laser irradiation. Nd:YAG and diode laser decreased the tracer penetration for AH Plus, whereas EndoREZ and EpiphanySE performances were affected by Nd:YAG irradiation (p<0.05). It can be concluded that intracanal laser irradiation can be used as an adjunct in endodontic treatment; however, the use of hydrophilic resin sealers should be avoided when root canals were irradiated with Nd:YAG laser.

  2. Laser Irradiated Growth of Protein Crystal

    NASA Astrophysics Data System (ADS)

    Adachi, Hiroaki; Takano, Kazufumi; Hosokawa, Youichiroh; Inoue, Tsuyoshi; Mori, Yusuke; Matsumura, Hiroyoshi; Yoshimura, Masashi; Tsunaka, Yasuo; Morikawa, Masaaki; Kanaya, Shigenori; Masuhara, Hiroshi; Kai, Yasushi; Sasaki, Takatomo

    2003-07-01

    We succeeded in the first ever generation of protein crystals by laser irradiation. We call this process Laser Irradiated Growth Technique (LIGHT). Effective crystallization was confirmed by applying an intense femtosecond laser. The crystallization period was dramatically shortened by LIGHT. In addition, protein crystals were obtained by LIGHT from normally uncrystallized conditions. These results indicate that intense femtosecond laser irradiation generates crystal nuclei; protein crystals can then be grown from the nuclei that act as seeds in a supersaturated solution. The nuclei formation is possible primarily due to nonlinear nucleation processes of an intense femtosecond laser with a peak intensity of over a gigawatt (GW).

  3. Rayleigh scattering correlation spectroscopy on diffusion dynamics of nanoparticles under intense laser irradiation

    NASA Astrophysics Data System (ADS)

    Hee, Ping-Yu; Uwada, Takayuki; Okano, Kazunori; Miura, Atsushi; Masuhara, Hiroshi

    2013-09-01

    Rayleigh scattering correlation microspectroscopy is developed and applied to study diffusion dynamics of some nanospheres in water. It was clearly found that the diffusion constant of gold nanoparticles decreased with increasing excitation laser power at the excitation wavelength of higher absorption cross section. This behavior was explained in terms of a coupling between laser trapping by the scattering excitation laser itself and laser heating of the particle. In the case of non-absorbing nanospheres such as silica and polystyrene, the excitation power dependence can be ascribed only to the laser trapping. Experimental setup is introduced, theoretical formulation is described, and future development of this measurement is considered.

  4. Characteristic x-ray emission from undermines plasmas irradiated by ultra-intense lasers

    SciTech Connect

    Niemann, Christoph

    2012-05-05

    Between FY09 and FY11 we have conducted more than a dozen three-week experimental campaigns at high-power laser facilities around the world to investigate laser-channeling through x-ray and optical imaging and the conversion from laser-energy to xrays. We have performed simultaneous two-wavelength x-ray imaging (K-alpha and He-alpha) to distinguish the hot-plasma region (hot-spot) from the laser-produced electrons (K-alpha). In addition, we have initiated a new collaboration with SNL and have performed first shots on the 100 TW beamlet chamber to commission a fast x-ray streak camera to be used to investigate the temporal evolution of our K-alpha sources. We also collaborated on campaigns at the Rutherford Appleton Laboratory (UK) and the LANL Trident laser to employ laser produced x-ray sources for Thomson scattering off dense matter.

  5. Effective post-acceleration of ion bunches in foils irradiated by ultra-intense laser pulses

    SciTech Connect

    Andreev, A. A.; Nickles, P. V.; Platonov, K. Yu

    2014-08-15

    Two-step laser acceleration of protons with two foils and two laser pulses is modelled and optimized. It is shown that a nearly mono-energetic distribution of proton bunches can be realized by a suitable parameter choice. Two-step acceleration schemes make it possible to obtain both higher efficiency and energy as compared to the acceleration with only one laser pulse of an energy equal to the sum of the energy of the two pulses. With the aid of our analytical model, the optimal distance between the two targets, the delay between the two laser pulses, and the parameters of the laser pulses are determined. Estimates and results of the modelling are proven with 2D PIC simulations of the acceleration of proton bunches moving through the second target.

  6. Hot electron and x-ray production from intense laser irradiation of wavelength-scale polystyrene spheres

    SciTech Connect

    Sumeruk, H. A.; Kneip, S.; Symes, D. R.; Churina, I. V.; Belolipetski, A. V.; Dyer, G.; Landry, J.; Bansal, G.; Bernstein, A.; Donnelly, T. D.; Karmakar, A.; Pukhov, A.; Ditmire, T.

    2007-06-15

    Hot electron and x-ray production from solid targets coated with polystyrene-spheres which are irradiated with high-contrast, 100 fs, 400 nm light pulses at intensity up to 2x10{sup 17} W/cm{sup 2} have been studied. The peak hard x-ray signal from uncoated fused silica targets is an order of magnitude smaller than the signal from targets coated with submicron sized spheres. The temperature of the x-rays in the case of sphere-coated targets is twice as hot as that of uncoated glass. A sphere-size scan of the x-ray yield and observation of a peak in both the x-ray production and temperature at a sphere diameter of 0.26 {mu}m, indicate that these results are consistent with Mie enhancements of the laser field at the sphere surface and multipass stochastic heating of the hot electrons in the oscillating laser field. These results also match well with particle-in-cell simulations of the interaction.

  7. Simulations of thermal wave propagation in a target irradiated by high-intensity p-polarised laser radiation

    SciTech Connect

    Politov, V Yu

    2013-05-31

    In a one-dimensional hydrodynamic approximation the evolution of a hot dense plasma produced by a high-power subpicosecond laser pulse absorbed primarily due to the resonance mechanism is investigated numerically. The heated plasma parameters of light and heavy chemical elements are compared. A prediction is made concerning the feasibility of producing a thin uniform plasma layer of a heavy substance in experiments on the irradiation of compound targets. (interaction of laser radiation with matter. laser plasma)

  8. Light absorption in blood during low-intensity laser irradiation of skin

    SciTech Connect

    Barun, V V; Ivanov, A P

    2010-06-23

    An analytical procedure is proposed for describing optical fields in biological tissues inhomogeneous in the depth direction, such as human skin, with allowance for multiple scattering. The procedure is used to investigate the depth distribution of the optical power density in homogeneous and multilayer dermis when the skin is exposed to a laser beam. We calculate the absorbed laser power spectra for oxy- and deoxyhaemoglobin at different depths in relation to the absorption selectivity of these haemoglobin derivatives and the spectral dependence of the optical power density and demonstrate that the spectra vary considerably with depth. A simple exponential approximation is proposed for the depth distribution of the power density in the epidermis and dermis. (laser methods in medicine)

  9. Quasimonoenergetic Proton Bunch Generation by Dual-Peaked Electrostatic-Field Acceleration in Foils Irradiated by an Intense Linearly Polarized Laser

    NASA Astrophysics Data System (ADS)

    Zhuo, H. B.; Chen, Z. L.; Yu, W.; Sheng, Z. M.; Yu, M. Y.; Jin, Z.; Kodama, R.

    2010-08-01

    It is found that stable proton acceleration from a thin foil irradiated by a linearly polarized ultraintense laser can be realized for appropriate foil thickness and laser intensity. A dual-peaked electrostatic field, originating from the oscillating and nonoscillating components of the laser ponderomotive force, is formed around the foil surfaces. This field combines radiation-pressure acceleration and target normal sheath acceleration to produce a single quasimonoenergetic ion bunch. A criterion for this mechanism to be operative is obtained and verified by two-dimensional particle-in-cell simulation. At a laser intensity of ˜5.5×1022W/cm2, quasimonoenergetic GeV proton bunches are obtained with ˜100MeV energy spread, less than 4° spatial divergence, and ˜50% energy conversion efficiency from the laser.

  10. Conversion efficiency and spectral broadening of the K-{alpha} line emitted from planar titanium targets irradiated with ultra-short laser pulses of high intensity

    SciTech Connect

    Arora, V.; Singhal, H.; Naik, P. A.; Gupta, P. D.

    2011-10-15

    A study of the conversion efficiency and line shape of the K-{alpha} x-ray line radiation from a planar titanium target irradiated by an ultra-short laser pulse is performed. The conversion efficiency and spectral broadening are studied as a function of laser intensity (5 x 10{sup 16}-10{sup 18} W cm{sup -2}), laser pulse duration (45 fs-800 fs), and laser fluence (2 x 10{sup 3}-4.2 x 10{sup 4} J cm{sup -2}). The K-{alpha}{sub 1} line (4510 eV) is observed to be broadened (up to {approx}9 eV), predominantly towards the higher energy side and strongly depends on the laser fluence rather than on laser intensity. The reason for the spectral broadening is attributed to K-{alpha} emission in warm dense plasma. The role of hot electrons and direct laser heating on spectral broadening is outlined. In addition to this, our observations indicates that the presence of pre-plasma strongly contribute to the observed broadening through the inner-shell transitions in multiply charged titanium ions in the pre-plasma. The appropriate laser irradiation parameters to achieve high conversion efficiency and minimum spectral width of the K-{alpha} radiation are identified. The study is important, since the control of the spectral profile is of general interest for diffraction or scattering experiments in view of its potential in increasing temporal resolution.

  11. Temperature changes on the root surfaces of mandibular incisors after an 810-nm high-intensity intracanal diode laser irradiation

    NASA Astrophysics Data System (ADS)

    da Fonseca Alvarez, Andrea; Moura-Netto, Cacio; Daliberto Frugoli, Alexandre; Fernando, Casemiro; Correa Aranha, Ana Cecilia; Davidowicz, Harry

    2012-01-01

    Temperature changes caused by laser irradiation can promote damage to the surrounding dental tissues. In this study, we evaluated the temperature changes of recently extracted human mandibular incisors during intracanal irradiation with an 810-nm diode laser at different settings. Fifty mandibular incisors were enlarged up to an apical size of ISO No. 40 file. After the final rinse with 17% ethylenediaminetetraacetic acid, 0.2% lauryl sodium sulfate biologic detergent, and sterile water, samples were irradiated with circular movements from apex to crown through five different settings of output power (1.5, 2.0, 2.5, 3.0, and 3.5 W) in continuous mode. The temperature changes were measured on both sides of the apical and middle root thirds using two thermopar devices. A temperature increase of 7 °C was considered acceptable as a safe threshold when applying the diode laser. Results: The results showed that only 3.5-W output power increased the outer surface temperature above the critical value. Conclusion: The recommended output power can be stipulated as equal to or less than 3 W to avoid overheating during diode laser irradiation on thin dentin walls.

  12. Analytical description of attosecond pulse generation on a plasma surface irradiated by high-intense laser pulses

    NASA Astrophysics Data System (ADS)

    Cherednychek, M.; Pukhov, A.

    2016-04-01

    We study theoretically the process of turning a laser pulse into a train of attosecond or even zeptosecond pulses due to high harmonic generation (HHG) upon backreflection of intense laser radiation from a plasma surface. It is shown that under appropriate conditions these attosecond pulses may have an amplitude that is several orders of magnitude larger than that of the laser pulse. We study this process in detail, especially the nanobunching of the plasma electron density. We derive the analytical expression that describes the electron density profile and obtain a good agreement with particle-in-cell simulations. We investigate the most efficient case of HHG at a moderate laser intensity (normalised vector potential α0 = 10) on the overdense plasma slab with an exponential pre-plasma profile. Subsequently we calculate the spectra of single attosecond pulses from back radiation using our expression for density shape in combination with the equation for spectrum of nanobunch radiation.

  13. Specific features of microheterogeneous plasma produced by irradiation of a polymer aerogel target with an intense 500-ps-long laser pulse

    SciTech Connect

    Borisenko, N. G.; Merkul’ev, Yu. A.; Orekhov, A. S.; Chaurasia, S.; Tripathi, S.; Munda, D. S.; Dhareshwar, L. J.; Pimenov, V. G.; Sheveleva, E. E.

    2013-08-15

    The properties of microheterogeneous plasma produced by irradiation of a polymer aerogel target with an intense (10{sup 14} W/cm{sup 3}) short (0.5 ps) 1.064-μm laser pulse were studied. It is found that, even at plasma densities exceeding the critical density, a small fraction of the incident laser radiation penetrates through the plasma in which the processes of density and temperature equalization still take place. The intensification (as compared to plasmas produced from denser foams and solid films) of transport processes in such plasma along and across the laser beam can be caused by the initial microheterogeneity of the solid target. The replacement of a small (10% by mass) part of the polymer with copper nanoparticles leads to a nearly twofold increase in the intensity of the plasma X-ray emission.

  14. Effect of low intensity helium-neon (HeNe) laser irradiation on experimental paracoccidioidomycotic wound healing dynamics.

    PubMed

    Ferreira, Maria Carolina; Gameiro, Jacy; Nagib, Patrícia Resende Alo; Brito, Vânia Nieto; Vasconcellos, Elza da Costa Cruz; Verinaud, Liana

    2009-01-01

    The effect of HeNe laser on the extracellular matrix deposition, chemokine expression and angiogenesis in experimental paracoccidioidomycotic lesions was investigated. At days 7, 8 and 9 postinfection the wound of each animal was treated with a 632.8 nm HeNe laser at a dose of 3 J cm(-2). At day 10 postinfection, the wounds were examined by using histologic and immunohistochemical methods. Results revealed that laser-treated lesions were lesser extensive than untreated ones, and composed mainly by macrophages and lymphocytes. High IL-1beta expression was shown in the untreated group whereas in laser-treated animals the expression was scarce. On the other hand, the expression of CXCL-10 was found to be reduced in untreated animals and quite intensive and well distributed in the laser-treated ones. Also, untreated lesions presented vascular endothelial growth factor (VEGF) in a small area near the center of the lesion and high immunoreactivity for hypoxia-inducible factor-1 (HIF-1), whereas laser-treated lesions expressed VEGF surrounding blood vessels and little immunoreactivity for HIF-1. Laser-treated lesions presented much more reticular fibers and collagen deposition when compared with the untreated lesion. Our results show that laser was efficient in minimizing the local effects observed in paracoccidioidomycosis and can be an efficient tool in the treatment of this infection, accelerating the healing process. PMID:18764901

  15. Enhancement of K{sub {alpha}} emission through efficient hot electron generation in carbon nanotubes on intense laser pulse irradiation

    SciTech Connect

    Chakravarty, U.; Arora, V.; Naik, P. A.; Chakera, J. A.; Srivastava, H.; Srivastava, A.; Kumbhare, S. R.; Gupta, P. D.; Varma, G. D.

    2012-09-01

    Near complete absorption of the energy of intense ultra-short laser pulses (45 fs, intensity {approx}1.6 Multiplication-Sign 10{sup 16} to 2.5 Multiplication-Sign 10{sup 17} W/cm{sup 2}) is observed in carbon nanotubes deposited on a planar molybdenum substrate. The hollow structure of the nanotube plasma facilitates resonant electric field enhancement during its ionization phase. This resonantly enhanced localized field at a density much larger than the critical density n{sub c} leads to efficient hot electron generation, which results in enhanced K{sub {alpha}} emission of Mo at 17.5 keV. It is observed that for nanotubes, depending on the degree of hollowness, there is an optimum laser intensity for maximum x-ray enhancement compared to a planar uncoated target.

  16. X-ray generation by fast electrons propagating in nanofibres irradiated by a laser pulse of relativistic intensity

    NASA Astrophysics Data System (ADS)

    Andreev, A. A.; Platonov, K. Yu

    2016-02-01

    Numerical simulations were made of the interaction of a relativistically intense laser pulse with a target consisting of nanometre fibres. Fast electrons were shown to execute forced betatron oscillations in the electrostatic fibre field and the laser field. The fibre diameter was determined whereby the amplitude of betatron electron oscillations is resonantly increased. The power of coherent X-ray betatron radiation of the electron bunch was calculated outside of the resonance domain and in the resonance case. We showed that the laser-to-X-ray betatron radiation conversion coefficient in the resonance case amounts to a few percent and the target made up of nanometre fibres may be regarded as an efficient laser-driven source of coherent X- and gamma-ray radiation.

  17. Fast-Ion Energy-Flux Enhancement from Ultrathin Foils Irradiated by Intense and High-Contrast Short Laser Pulses

    SciTech Connect

    Andreev, A.; Platonov, K.; Levy, A.; Ceccotti, T.; Thaury, C.; Loch, R. A.; Martin, Ph.

    2008-10-10

    Recent significant improvements of the contrast ratio of chirped pulse amplified pulses allows us to extend the applicability domain of laser accelerated protons to very thin targets. In this framework, we propose an analytical model particularly suitable to reproducing ion laser acceleration experiments using high intensity and ultrahigh contrast pulses. The model is based on a self-consistent solution of the Poisson equation using an adiabatic approximation for laser generated fast electrons which allows one to find the target thickness maximizing the maximum proton (and ion) energies and population as a function of the laser parameters. Model furnished values show a good agreement with experimental data and 2D particle-in-cell simulation results.

  18. Conformational Transformations of Hemoglobin Molecules During in vivo Blood Irradiation by Low-Intensity Laser Radiation in the Red and Near IR Ranges

    NASA Astrophysics Data System (ADS)

    Zalesskaya, G. A.

    2014-07-01

    The effect of in vivo blood irradiation by low-intensity laser radiation on electronic-conformational interactions in hemoglobin molecules has been studied experimentally. The changes in the electronic and IR absorption spectra were followed for blood samples drawn at specific times during intravenous and supravascular irradiation, and also after dark reactions have occurred. The nature of the spectral changes observed is discussed. It is shown that the reversible photodissociation of hemoglobin-ligand complexes, initiated by blood irradiation, changes the oxyhemoglobin and deoxyhemoglobin levels, which leads to changes in the electronic absorption spectra of the blood and erythrocytes, and all the conformational transitions in the hemoglobin macromolecules accompanying ligand detachment and addition are responsible for the changes in their IR spectra.

  19. L-shell emission from high-Z solid targets by intense 10{sup 19}W/cm{sup 2} irradiation with a 248nm laser

    SciTech Connect

    Nelson, T.R.; Borisov, A.B.; Boyer, K.

    2000-01-05

    Efficient (1.2% yield) multikilovolt x-ray emission from Ba(L) (2.4--2.8{angstrom}) and Gd(L) (1.7--2.1{angstrom}) is produced by ultraviolet (248nm) laser-excited BaF{sub 2} and Gd solids. The high efficiency is attributed to an inner shell-selective collisional electron ejection. Much effort has been expended recently in attempts to develop an efficient coherent x-ray source suitable for high-resolution biological imaging. To this end, many experiments have been performed studying the x-ray emissions from high-Z materials under intense (>10{sup 18}W/cm{sup 2}) irradiation, with the most promising results coming from the irradiation of Xe clusters with a UV (248nm) laser at intensities of 10{sup 18}--10{sup 19}W/cm{sup 2}. In this paper the authors report the production of prompt x-rays with energies in excess of 5keV with efficiencies on the order of 1% as a result of intense irradiation of BaF{sub 2} and Gd targets with a terawatt 248nm laser. The efficiency is attributed to an inner shell-selective collisional electron ejection mechanism in which the previously photoionized electrons are ponderomotively driven into an ion while retaining a portion of their atomic phase and symmetry. This partial coherence of the laser-driven electrons has a pronounced effect on the collisional cross-section for the electron ion interaction.

  20. Microjet formation and hard x-ray production from a liquid metal target irradiated by intense femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Lar'kin, A.; Uryupina, D.; Ivanov, K.; Savel'ev, A.; Bonnet, T.; Gobet, F.; Hannachi, F.; Tarisien, M.; Versteegen, M.; Spohr, K.; Breil, J.; Chimier, B.; Dorchies, F.; Fourment, C.; Leguay, P.-M.; Tikhonchuk, V. T.

    2014-09-01

    By using a liquid metal as a target one may significantly enhance the yield of hard x-rays with a sequence of two intense femtosecond laser pulses. The influence of the time delay between the two pulses is studied experimentally and interpreted with numerical simulations. It was suggested that the first arbitrary weak pulse produces microjets from the target surface, while the second intense pulse provides an efficient electron heating and acceleration along the jet surface. These energetic electrons are the source of x-ray emission while striking the target surface. The microjet formation is explained based on the results given by both optical diagnostics and hydrodynamic modeling by a collision of shocks originated from two distinct zones of laser energy deposition.

  1. Microjet formation and hard x-ray production from a liquid metal target irradiated by intense femtosecond laser pulses

    SciTech Connect

    Lar'kin, A. Uryupina, D.; Ivanov, K.; Savel'ev, A.; Bonnet, T.; Gobet, F.; Hannachi, F.; Tarisien, M.; Versteegen, M.; Spohr, K.; Breil, J.; Chimier, B.; Dorchies, F.; Fourment, C.; Leguay, P.-M.; Tikhonchuk, V. T.

    2014-09-15

    By using a liquid metal as a target one may significantly enhance the yield of hard x-rays with a sequence of two intense femtosecond laser pulses. The influence of the time delay between the two pulses is studied experimentally and interpreted with numerical simulations. It was suggested that the first arbitrary weak pulse produces microjets from the target surface, while the second intense pulse provides an efficient electron heating and acceleration along the jet surface. These energetic electrons are the source of x-ray emission while striking the target surface. The microjet formation is explained based on the results given by both optical diagnostics and hydrodynamic modeling by a collision of shocks originated from two distinct zones of laser energy deposition.

  2. Hot Electron Generation in the Micro-Tipped Cone and Wedge Targets Irradiated with Ultra Intense Laser.

    NASA Astrophysics Data System (ADS)

    Cho, B. I.; Dyer, G. M.; Kneip, S.; Symes, D. R.; Bernstein, A. C.; Pikuz, S.; Sentoku, Y.; Le Galloudec, N.; Cowan, T. E.; Ditmire, T.

    2008-04-01

    By comparing Kα and bremsstrahlung x-rays yields, we have investigated hot electron generation from pyramidal-shaped reentrant micro-structured targets. We focused the THOR laser at the University of Texas at Austin (800nm, 40fs, 600mJ, 2 x 10^19 W/cm^2 ) into these cone and wedge shaped targets with various polarizations. We find that hot electron production is highest in the wedge targets when irradiated with transverse polarization, though Kα is maximized with wedge targets and parallel polarization. These results are explained with particle-in-cell simulations.

  3. Possibility of applying a hydrodynamic model to describe the laser erosion of metals irradiated by high-intensity nanosecond pulses

    SciTech Connect

    Kozadaev, K V

    2014-04-28

    We report the results of experimental investigations of the production and development of plasma-vapour plumes upon irradiation of metal targets by nanosecond (10–100 ns) pulses with a high (10{sup 8}–10{sup 10} W cm{sup -2}) power density under atmospheric conditions. The transition from a quasi-stationary thermal mechanism of metal erosion to an explosion hydrodynamic one takes place when the radiation power density increases from 10{sup 8} to 10{sup 9} W cm{sup -2}. The resultant experimental information is extremely important for the laser deposition of metal nanostructures under atmospheric conditions, which is possible only for power densities of 10{sup 8}–10{sup 9} W cm{sup -2}. (interaction of laser radiation with matter)

  4. Detection of surface changes of materials caused by intense irradiation with laser-plasma EUV source utilizing scattered or luminescent radiation excited with the EUV pulses

    NASA Astrophysics Data System (ADS)

    Bartnik, A.; Fiedorowicz, H.; Jarocki, R.; Kostecki, J.; Rakowski, R.; Szczurek, M.

    2008-04-01

    Extreme ultraviolet (EUV) radiation is absorbed in a thin surface layer of any material. Irradiation of material samples with intense EUV pulses may cause different surface changes. Some of them, especially connected with material desorption, can be clearly visible using an optical or electron microscope. Other changes concerning crystal structure or chemical composition may not be visible under the microscope. They can however be detected using the EUV radiation itself. In this paper a new method of measurement of surface changes by irradiation with a laser-plasma EUV source is presented. The radiation was collected and focused on a material surface using a specially designed multifoil collector. Radiation scattered or excited in the material was detected with the use of a Wolter-type mirror coupled to a back-illuminated CCD camera. Depending on material samples, images with different intensity distributions were registered. For some samples, the intensity distributions of the images obtained before and after irradiation were slightly different. The intensity differences in such cases allowed us to obtain differential images. The appearance of such images was assumed to be evidence of surface changes.

  5. Intense ion beams accelerated by ultra-intense laser pulses

    NASA Astrophysics Data System (ADS)

    Roth, Markus; Cowan, T. E.; Gauthier, J. C.; Vehn, J. Meyer-Ter; Allen, M.; Audebert, P.; Blazevic, A.; Fuchs, J.; Geissel, M.; Hegelich, M.; Karsch, S.; Pukhov, A.; Schlegel, T.

    2002-04-01

    The discovery of intense ion beams off solid targets irradiated by ultra-intense laser pulses has become the subject of extensive international interest. These highly collimated, energetic beams of protons and heavy ions are strongly depending on the laser parameters as well as on the properties of the irradiated targets. Therefore we have studied the influence of the target conditions on laser-accelerated ion beams generated by multi-terawatt lasers. The experiments were performed using the 100 TW laser facility at Laboratoire pour l'Utilisation des Laser Intense (LULI). The targets were irradiated by pulses up to 5×1019 W/cm2 (~300 fs,λ=1.05 μm) at normal incidence. A strong dependence on the surface conditions, conductivity, shape and purity was observed. The plasma density on the front and rear surface was determined by laser interferometry. We characterized the ion beam by means of magnetic spectrometers, radiochromic film, nuclear activation and Thompson parabolas. The strong dependence of the ion beam acceleration on the conditions on the target back surface was confirmed in agreement with predictions based on the target normal sheath acceleration (TNSA) mechanism. Finally shaping of the ion beam has been demonstrated by the appropriate tailoring of the target. .

  6. Nonlinear increase of X-ray intensities from thin foils irradiated with a 200 TW femtosecond laser

    NASA Astrophysics Data System (ADS)

    Faenov, A. Ya.; Colgan, J.; Hansen, S. B.; Zhidkov, A.; Pikuz, T. A.; Nishiuchi, M.; Pikuz, S. A.; Skobelev, I. Yu.; Abdallah, J.; Sakaki, H.; Sagisaka, A.; Pirozhkov, A. S.; Ogura, K.; Fukuda, Y.; Kanasaki, M.; Hasegawa, N.; Nishikino, M.; Kando, M.; Watanabe, Y.; Kawachi, T.; Masuda, S.; Hosokai, T.; Kodama, R.; Kondo, K.

    2015-09-01

    We report, for the first time, that the energy of femtosecond optical laser pulses, E, with relativistic intensities I > 1021  W/cm2 is efficiently converted to X-ray radiation, which is emitted by “hot” electron component in collision-less processes and heats the solid density plasma periphery. As shown by direct high-resolution spectroscopic measurements X-ray radiation from plasma periphery exhibits unusual non-linear growth ~E4-5 of its power. The non-linear power growth occurs far earlier than the known regime when the radiation reaction dominates particle motion (RDR). Nevertheless, the radiation is shown to dominate the kinetics of the plasma periphery, changing in this regime (now labeled RDKR) the physical picture of the laser plasma interaction. Although in the experiments reported here we demonstrated by observation of KK hollow ions that X-ray intensities in the keV range exceeds ~1017  W/cm2, there is no theoretical limit of the radiation power. Therefore, such powerful X-ray sources can produce and probe exotic material states with high densities and multiple inner-shell electron excitations even for higher Z elements. Femtosecond laser-produced plasmas may thus provide unique ultra-bright X-ray sources, for future studies of matter in extreme conditions, material science studies, and radiography of biological systems.

  7. Nonlinear increase of X-ray intensities from thin foils irradiated with a 200 TW femtosecond laser

    DOE PAGESBeta

    Faenov, A. Ya.; Colgan, J.; Hansen, S. B.; Zhidkov, A.; Pikuz, T. A.; Nishiuchi, M.; Pikuz, S. A.; Skobelev, I. Yu.; Abdallah, J.; Sakaki, H.; et al

    2015-09-02

    We report, for the first time, that the energy of femtosecond optical laser pulses, E, with relativistic intensities I > 1021 W/cm2 is efficiently converted to X-ray radiation, which is emitted by “hot” electron component in collision-less processes and heats the solid density plasma periphery. As shown by direct high-resolution spectroscopic measurements X-ray radiation from plasma periphery exhibits unusual non-linear growth ~E4–5 of its power. The non-linear power growth occurs far earlier than the known regime when the radiation reaction dominates particle motion (RDR). Nevertheless, the radiation is shown to dominate the kinetics of the plasma periphery, changing in thismore » regime (now labeled RDKR) the physical picture of the laser plasma interaction. Although in the experiments reported here we demonstrated by observation of KK hollow ions that X-ray intensities in the keV range exceeds ~1017 W/cm2, there is no theoretical limit of the radiation power. Therefore, such powerful X-ray sources can produce and probe exotic material states with high densities and multiple inner-shell electron excitations even for higher Z elements. As a result, femtosecond laser-produced plasmas may thus provide unique ultra-bright X-ray sources, for future studies of matter in extreme conditions, material science studies, and radiography of biological systems.« less

  8. Nonlinear increase of X-ray intensities from thin foils irradiated with a 200 TW femtosecond laser

    SciTech Connect

    Faenov, A. Ya.; Colgan, J.; Hansen, S. B.; Zhidkov, A.; Pikuz, T. A.; Nishiuchi, M.; Pikuz, S. A.; Skobelev, I. Yu.; Abdallah, J.; Sakaki, H.; Sagisaka, A.; Pirozhkov, A. S.; Ogura, K.; Fukuda, Y.; Kanasaki, M.; Hasegawa, N.; Nishikino, M.; Kando, M.; Watanabe, Y.; Kawachi, T.; Masuda, S.; Hosokai, T.; Kodama, R.; Kondo, K.

    2015-09-02

    We report, for the first time, that the energy of femtosecond optical laser pulses, E, with relativistic intensities I > 1021 W/cm2 is efficiently converted to X-ray radiation, which is emitted by “hot” electron component in collision-less processes and heats the solid density plasma periphery. As shown by direct high-resolution spectroscopic measurements X-ray radiation from plasma periphery exhibits unusual non-linear growth ~E4–5 of its power. The non-linear power growth occurs far earlier than the known regime when the radiation reaction dominates particle motion (RDR). Nevertheless, the radiation is shown to dominate the kinetics of the plasma periphery, changing in this regime (now labeled RDKR) the physical picture of the laser plasma interaction. Although in the experiments reported here we demonstrated by observation of KK hollow ions that X-ray intensities in the keV range exceeds ~1017 W/cm2, there is no theoretical limit of the radiation power. Therefore, such powerful X-ray sources can produce and probe exotic material states with high densities and multiple inner-shell electron excitations even for higher Z elements. As a result, femtosecond laser-produced plasmas may thus provide unique ultra-bright X-ray sources, for future studies of matter in extreme conditions, material science studies, and radiography of biological systems.

  9. Nonlinear increase of X-ray intensities from thin foils irradiated with a 200 TW femtosecond laser

    PubMed Central

    Faenov, A. Ya.; Colgan, J.; Hansen, S. B.; Zhidkov, A.; Pikuz, T. A.; Nishiuchi, M.; Pikuz, S. A.; Skobelev, I. Yu.; Abdallah, J.; Sakaki, H.; Sagisaka, A.; Pirozhkov, A. S.; Ogura, K.; Fukuda, Y.; Kanasaki, M.; Hasegawa, N.; Nishikino, M.; Kando, M.; Watanabe, Y.; Kawachi, T.; Masuda, S.; Hosokai, T.; Kodama, R.; Kondo, K.

    2015-01-01

    We report, for the first time, that the energy of femtosecond optical laser pulses, E, with relativistic intensities I > 1021  W/cm2 is efficiently converted to X-ray radiation, which is emitted by “hot” electron component in collision-less processes and heats the solid density plasma periphery. As shown by direct high-resolution spectroscopic measurements X-ray radiation from plasma periphery exhibits unusual non-linear growth ~E4–5 of its power. The non-linear power growth occurs far earlier than the known regime when the radiation reaction dominates particle motion (RDR). Nevertheless, the radiation is shown to dominate the kinetics of the plasma periphery, changing in this regime (now labeled RDKR) the physical picture of the laser plasma interaction. Although in the experiments reported here we demonstrated by observation of KK hollow ions that X-ray intensities in the keV range exceeds ~1017  W/cm2, there is no theoretical limit of the radiation power. Therefore, such powerful X-ray sources can produce and probe exotic material states with high densities and multiple inner-shell electron excitations even for higher Z elements. Femtosecond laser-produced plasmas may thus provide unique ultra-bright X-ray sources, for future studies of matter in extreme conditions, material science studies, and radiography of biological systems. PMID:26330230

  10. Nonlinear increase of X-ray intensities from thin foils irradiated with a 200 TW femtosecond laser.

    PubMed

    Faenov, A Ya; Colgan, J; Hansen, S B; Zhidkov, A; Pikuz, T A; Nishiuchi, M; Pikuz, S A; Skobelev, I Yu; Abdallah, J; Sakaki, H; Sagisaka, A; Pirozhkov, A S; Ogura, K; Fukuda, Y; Kanasaki, M; Hasegawa, N; Nishikino, M; Kando, M; Watanabe, Y; Kawachi, T; Masuda, S; Hosokai, T; Kodama, R; Kondo, K

    2015-01-01

    We report, for the first time, that the energy of femtosecond optical laser pulses, E, with relativistic intensities I > 10(21)  W/cm(2) is efficiently converted to X-ray radiation, which is emitted by "hot" electron component in collision-less processes and heats the solid density plasma periphery. As shown by direct high-resolution spectroscopic measurements X-ray radiation from plasma periphery exhibits unusual non-linear growth ~E(4-5) of its power. The non-linear power growth occurs far earlier than the known regime when the radiation reaction dominates particle motion (RDR). Nevertheless, the radiation is shown to dominate the kinetics of the plasma periphery, changing in this regime (now labeled RDKR) the physical picture of the laser plasma interaction. Although in the experiments reported here we demonstrated by observation of KK hollow ions that X-ray intensities in the keV range exceeds ~10(17)  W/cm(2), there is no theoretical limit of the radiation power. Therefore, such powerful X-ray sources can produce and probe exotic material states with high densities and multiple inner-shell electron excitations even for higher Z elements. Femtosecond laser-produced plasmas may thus provide unique ultra-bright X-ray sources, for future studies of matter in extreme conditions, material science studies, and radiography of biological systems. PMID:26330230

  11. Ionization and acceleration of heavy ions in high-Z solid target irradiated by high intensity laser

    NASA Astrophysics Data System (ADS)

    Kawahito, D.; Kishimoto, Y.

    2016-05-01

    In the interaction between high intensity laser and solid film, an ionization dynamics inside the solid is dominated by fast time scale convective propagation of the internal sheath field and the slow one by impact ionization due to heated high energy electrons coupled with nonlocal heat transport. Furthermore, ionization and acceleration due to the localized external sheath field which co- propagates with Al ions constituting the high energy front in the vacuum region. Through this process, the maximum charge state and then q/A increase in the rear side, so that ions near the front are further accelerated to high energy.

  12. Study of Acceleration, Transport and Dephasing of Hot Electrons in Solid Density Plasmas Irradiated with Ultra Intense Laser Pulses

    NASA Astrophysics Data System (ADS)

    Cho, B. I.; Osterholz, J.; Bernstein, A. C.; Dyer, G. M.; Ditmire, T.

    2008-04-01

    We have characterized the transport of hot electrons in solid targets by coherent transition radiation (CTR). CTR was observed from the rear side of aluminum foils irradiated with the THOR laser (800 nm, 40 fs, 600 mJ, 2 x 10^19 W/cm^2) at the University of Texas at Austin. In the experiment, two distinct beams of hot electrons are emitted simultaneously from the target rear side. This observation shows that two different mechanisms, namely resonance absorption and j x B heating, accelerate the electrons at the target front side. These two distinct beams propagate through aluminum foils with different spatial and temporal characteristics and electron temperatures. The interpretation is confirmed by calculations of the electron acceleration and transport inside the target.

  13. Resonance laser-plasma excitation of coherent terahertz phonons in the bulk of fluorine-bearing crystals under high-intensity femtosecond laser irradiation

    SciTech Connect

    Potemkin, F V; Mareev, E I; Khodakovskii, N G; Mikheev, P M

    2013-08-31

    The dynamics of coherent phonons in fluorine-containing crystals was investigated by pump-probe technique in the plasma production regime. Several phonon modes, whose frequencies are overtones of the 0.38-THz fundamental frequency, were simultaneously observed in a lithium fluoride crystal. Phonons with frequencies of 1 and 0.1 THz were discovered in a calcium fluoride crystal and coherent phonons with frequencies of 1 THz and 67 GHz were observed in a barium fluoride crystal. Furthermore, in the latter case the amplitudes of phonon mode oscillations were found to significantly increase 15 ps after laser irradiation. (interaction of laser radiation with matter)

  14. Enhanced water window x-ray emission from in situ formed carbon clusters irradiated by intense ultra-short laser pulses

    SciTech Connect

    Chakravarty, U.; Rao, B. S.; Arora, V.; Upadhyay, A.; Singhal, H.; Naik, P. A.; Chakera, J. A.; Mukherjee, C.; Gupta, P. D.

    2013-07-29

    Enhanced water window x-ray emission (23–44 Å) from carbon clusters, formed in situ using a pre-pulse, irradiated by intense (I > 10{sup 17} W/cm{sup 2}) ultra-short laser pulse, is demonstrated. An order of magnitude x-ray enhancement over planar graphite target is observed in carbon clusters, formed by a sub-ns pre-pulse, interacting with intense main pulse after a delay. The effect of the delay and the duration of the main pulse is studied for optimizing the x-ray emission in the water window region. This x-ray source has added advantages of being an efficient, high repetition rate, and low debris x-ray source.

  15. Low intensity laser treatment of nerve injuries

    NASA Astrophysics Data System (ADS)

    Liu, Xiao-Guang; Liu, Timon Cheng-Yi; Luo, Qing-Ming

    2007-05-01

    The neural regeneration and functional recovery after nerve injuries has long been an important field in neuroscience. Low intensity laser (LIL) irradiation is a novel and useful tool for the treatment of many injuries and disorders. The aim of this study was to assess the role of LIL irradiation in the treatment of peripheral and central nerve injuries. Some animal experiments and clinical investigations have shown beneficial effects of LIL irradiation on neural tissues, but its therapeutic value and efficacy are controversial. Reviewing the data of experimental and clinical studies by using the biological information model of photobiomodulation, we conclude that LIL irradiation in specific parameters can promote the regeneration of injured peripheral and central nerves and LIL therapy is a safe and valuable treatment for superficial peripheral nerve injuries and spinal cord injury. The biological effects of LIL treatment depend largely on laser wavelength, power and dose per site and effective irradiation doses are location-specific.

  16. Formation of Attosecond XUV Pulses via Resonance with Hydrogen-Like Atoms Irradiated by Intense Laser Field

    NASA Astrophysics Data System (ADS)

    Polovinkin, V. A.; Radeonychev, Y. V.; Kocharovskaya, Olga; Ryabikin, M. Yu.

    We show the possibility to produce a short bunch of few nearly bandwidth-limited few-cycle attosecond pulses via the time-dependent resonant interaction of an incident radiation pulse with the bound states of hydrogenlike atoms. Time-dependence of the resonant interaction is based on time-dependent tunnel ionization from the excited states and temporal adiabatic Stark splitting of the excited energy levels, provided by far-off-resonant laser pulse whose intensity is much below the atomic ionization threshold. Without external synchronization of the spectral components it is possible to produce pulses of XUV radiation with duration up to 80 as at the carrier wavelength 13.5 nm in Li2 +-plasma.

  17. Photoionization of helium atoms irradiated with intense vacuum ultraviolet free-electron laser light. Part I. Experimental study of multiphoton and single-photon processes

    SciTech Connect

    Laarmann, T.; Guertler, P.; Laasch, W.; Schulz, J.; Wabnitz, H.; Moeller, T.; Castro, A.R.B. de

    2005-08-15

    The interaction of He atoms with intense vacuum-ultraviolet light of a free-electron laser is investigated using time-of-flight mass spectroscopy and photoelectron spectroscopy. The atoms were irradiated with 100 fs pulses at 95 nm wavelength, which corresponds to {approx}13 eV photon energy. The ionization of He atoms is observed at a peak intensity of 10{sup 10}-10{sup 13} W/cm{sup 2}, which is due both to nonlinear multiphoton ionization with the fundamental wavelength and single-photon ionization with third harmonic radiation of the free-electron laser. The observation of two sharp photoelectron peaks in the kinetic energy spectra, that are separated by the photon energy, is in agreement with the numerical solution of the time-dependent Schroedinger equation. The calculation was done using the fully quantized field and a limited but representative set of basis states. The ionization rate dependence on the laser peak intensity indicates that: (a) The low-energy peak in the photoelectron spectra is mainly due to two-photon absorption of the fundamental, but (b) the high-energy peak at 15.4 eV is probably due to third harmonic FEL radiation. The theoretically predicted contribution from three-photon absorption of the fundamental is of about the same order of magnitude and could not be separated from the third harmonic background signal. Particularly, the photoelectron spectra and He{sup +} time-of-flight data give evidence that the intensity of third harmonic light is high enough to perform single-shot spectroscopy on gas phase samples.

  18. Experimental Study on Fast Electrons Transport in Ultra-intense Laser Irradiated Solid Targets by Transition Radiation

    NASA Astrophysics Data System (ADS)

    Zhijian, Zheng; Guangcan, Wang; Yuqiu, Gu

    2008-11-01

    The experiment was performed with SILEX laser facility(Ti-saphhire) at LFRC in China. The SILEX parameter: wavelength 0.8μm, duration 35fs, output power 280TW, contrast 5*105, The focal spot φ10μm(F/1.7), intensity on target surface 1*10^19W/cm^2(F/3). The main diagnostic equipments are the electron spectrometer, OMA spectrometer, optical streak camera. Some experimental results are given: The spectrum of optical emission from rear surface is rather narrow around some particular frequencies(1φ, 2φ, 3φ), We ascribe and confirm that the spike-like spectral line that is coherent transition radiation; The coherent light is also seen on time-integrated image with ring-patter due to Weibel instability of the fast electron transport; Obtained experimental cure of target thickness vs OTR image intensity is relative to mean free path of fast electron; The measuring optical transition radiation(OTR) duration of 171ps much longer than 1ps duration of fast electron transport target, the possible explanation is that the OTR duration to be determined magnetic diffusion time.

  19. Interference effects and Stark broadening in XUV intrashell transitions in aluminum under conditions of intense XUV free-electron-laser irradiation

    NASA Astrophysics Data System (ADS)

    Galtier, E.; Rosmej, F. B.; Calisti, A.; Talin, B.; Mossé, C.; Ferri, S.; Lisitsa, V. S.

    2013-03-01

    Quantum mechanical interference effects in the line broadening of intrashell transitions are investigated for dense plasma conditions. Simulations that involved LSJ-split level structure and intermediate coupling discovered unexpected strong line narrowing for intrashell transitions L-L while M-L transitions remained practically unaffected by interference effects. This behavior allows a robust study of line narrowing in dense plasmas. Simulations are carried out for XUV transitions of aluminum that have recently been observed in experiments with the FLASH free-electron laser in Hamburg irradiating solid aluminum samples with intensities greater than 1016 W/cm2. We explore the advantageous case of Al that allows, first, simultaneous observation of M-L transitions and L-L intrashell transitions with high-resolution grating spectrometers and, second, has a convenient threshold to study interference effects at densities much below solid. Finally, we present simulations at near solid density where the line emission transforms into a quasicontinuum.

  20. Influence of the fractioned irradiation energy in the phototherapy with low intensity laser on the growth of human dental pulp fibroblasts

    NASA Astrophysics Data System (ADS)

    Meneguzzo, D. T.; Eduardo, C. P.; Ribeiro, M. S.; Marques, M. M.

    2008-03-01

    Laser phototherapy has proven to improve treatment of several pathologies in dentistry. The aim of the present study was to analyze the low power laser phototherapy effects comparing multiple irradiations with the same total energy at once. This in vitro study focuses on the biostimulation of cellular growth of pulp fibroblasts (FP5 cell lineage). The cells were grown in Dulbecco's Modified Eagle's (DME) medium with either 5% (nutritional deficit) or 10% fetal bovine serum (FBS). Laser irradiation was carried out with diode lasers with the following parameters: 685 nm, 40 mW, spot size 0.019 cm2. The groups were: G1(6.3J/cm2, 3 s, 0.12J), G2 (12.6J/cm2, 6 s, 0.24J), G3 (18.9J/cm2, 9 s, 0.36J), G4 (2 irradiations of 6.3J/cm2, 0.24J), G5 (3 irradiations of 6.3J/cm2, 0.36J), G6 (5% SFB, negative control, without irradiation), and G7 (10% SFB, positive control, without irradiation). On groups G4 and G5 the irradiation was performed with 6h-intervals. For growth analysis, the MTT test was used 24 hours after the last irradiation. The data from spectrophotometer were analyzed by ANOVA followed by the Tukey's test. The groups submitted to multiple irradiations presented significantly higher cell growth than the groups with single irradiation. This cell growth was similar to that of positive control group. The laser phototherapy with multiple irradiations is more effective on cellular growth.

  1. Genetic expression of adipose derived stem cell and smooth muscle cell markers to monitor differentiation potential following low intensity laser irradiation

    NASA Astrophysics Data System (ADS)

    Abrahamse, Heidi

    2014-02-01

    Mesenchymal stem cells (MSCs) have the capacity to differentiate into a variety of cell types that could potentially be used in tissue engineering and regenerative medicine. Low intensity laser irradiation (LILI) has been shown to induce a significant increase in cell viability and proliferation. Growth factors such as retinoic acid (RA) and transforming growth factor β1 (TGF-β1) play important roles in the differentiation of cells. The aim of this study was to investigate whether LILI in combination with growth factors could induce the differentiation of adipose derived stem cells (ADSCs) cocultured with smooth muscle cells (SMCs). The study used primary and continuous ADSC cell lines and a SMC line (SKUT-1) as control. Cells were co-cultured directly at a ratio of 1:1 using established methods, with and without growth factors and then exposed to LILI at 5 J/cm2 using a 636 nm diode laser. The cellular morphology, viability and proliferation of the co-cultures were assessed over a period of one week. The study also monitored the expression of cell specific markers over the same period of time. Genetic expression of the markers for both adipose derived stem cells (β1 Integrin and Thymidine 1) and smooth muscle cells (Heavy Myosin Chain) was monitored using flow cytometry. Cell viability and proliferation increased significantly in the co-cultured groups that were exposed to laser alone, as well as in combination with growth factors. Furthermore, there was a significant decrease in the expression of stem cell markers in the ADSCs over time. The results indicate that LILI in combination with growth factors not only increases the viability and proliferation of co-cultured cells but also decreases the expression of ADSC stem cell markers. This could indicate the possible differentiation of ADSCs into SMCs.

  2. Intense transient magnetic-field generation by laser plasma

    SciTech Connect

    Benjamin, R.F.

    1981-08-18

    In a laser system, the return current of a laser generated plasma is conducted near a target to subject that target to the magnetic field thereof. In alternate embodiments the target may be either a small non-fusion object for testing under the magnetic field or a laser-fusion pellet. In the laser-fusion embodiment, the laser-fusion pellet is irradiated during the return current flow and the intense transient magnetic field is used to control the hot electrons thereof to hinder them from striking and heating the core of the irradiated laser-fusion pellet.

  3. Ultrafast laser and swift heavy ion irradiation: Response of Gd2O3 and ZrO2 to intense electronic excitation

    NASA Astrophysics Data System (ADS)

    Rittman, Dylan R.; Tracy, Cameron L.; Cusick, Alex B.; Abere, Michael J.; Torralva, Ben; Ewing, Rodney C.; Yalisove, Steven M.

    2015-04-01

    In order to investigate the response of materials to extreme conditions, there are several approaches to depositing extremely high concentrations of energy into very small volumes of material, including ultrafast laser and swift heavy ion (SHI) irradiation. In this study, crystalline-to-crystalline phase transformations in cubic Gd2O3 and monoclinic ZrO2 have been investigated using ultrafast laser irradiation. The phases produced by the extreme conditions of irradiation were characterized by grazing incidence x-ray diffraction (GIXRD) and Raman spectroscopy. Gd2O3 exhibited a cubic-to-monoclinic phase transformation, as evidenced by the appearance of the monoclinic (40 2 ¯ ), (003), (310), and (11 2 ¯ ) peaks in the GIXRD pattern and of four Ag and three Bg Raman modes. ZrO2 underwent a monoclinic-to-tetragonal phase transformation, as evidenced by the emergence of the tetragonal (101) peak in the GIXRD pattern and of Eg and A1g Raman modes. The new phases formed by ultrafast laser irradiation are high temperature polymorphs of the two materials. No evidence of amorphization was seen in the GIXRD data, though Raman spectroscopy indicated point defect accumulation. These results are identical to those produced by irradiation with SHIs, which also deposit energy in materials primarily through electronic excitation. The similarity in damage process and material response between ultrafast laser and SHI irradiation suggests a fundamental relationship between these two techniques.

  4. Modeling target bulk heating resulting from ultra-intense short pulse laser irradiation of solid density targets

    SciTech Connect

    Antici, P.; INRS-EMT, Varennes, Québec; Istituto Nazionale di Fisica Nucleare, Via E. Fermi, 40-00044 Frascati; LULI, École Polytechnique, CNRS, CEA, UPMC, route de Saclay, 91128 Palaiseau ; Gremillet, L.; Grismayer, T.; Audebert, P.; Mančic, A.; Fuchs, J.; Borghesi, M.; Cecchetti, C. A.

    2013-12-15

    Isochoric heating of solid-density matter up to a few tens of eV is of interest for investigating astrophysical or inertial fusion scenarios. Such ultra-fast heating can be achieved via the energy deposition of short-pulse laser generated electrons. Here, we report on experimental measurements of this process by means of time- and space-resolved optical interferometry. Our results are found in reasonable agreement with a simple numerical model of fast electron-induced heating.

  5. Energy transport and isochoric heating of a low-Z, reduced-mass target irradiated with a high intensity laser pulse

    SciTech Connect

    Nishimura, H.; Nakamura, H.; Tanabe, M.; Fujiwara, T.; Yamamoto, N.; Fujioka, S.; Mima, K.; Mishra, R.; Sentoku, Y.; Mancini, R.; Hakel, P.; Ohshima, S.; Batani, D.; Veltcheva, M.; Desai, T.; Jafer, R.; Kawamura, T.; Koike, F.

    2011-02-15

    Heat transport in reduced-mass targets irradiated with a high intensity laser pulse was studied. K{alpha} lines from partially ionized chlorine embedded in the middle of a triple-layered plastic target were measured to evaluate bulk electron temperature in the tracer region inside the target. Two groups of K{alpha} lines, one from Cl{sup +}-Cl{sup 6+} (hereby called ''cold K{alpha}''), and the other from Cl{sup 9+} and Cl{sup 10+} (''shifted K{alpha}'') are observed from different regions within the target. Two-dimensional collisional particle-in-cell simulations show two distinct heating mechanisms occurring concurrently: uniform heating by refluxing electrons and local heating by diffusive electrons in the central region. These two heating processes, which made the target temperature distribution nonuniform, are responsible for producing the two groups of K{alpha} lines in the experiment. The blue-shift of cold K{alpha} lines in the experiment is the signature of higher temperatures achieved by the refluxing heating in smaller-mass targets.

  6. Ultrafast laser and swift heavy ion irradiation: Response of Gd{sub 2}O{sub 3} and ZrO{sub 2} to intense electronic excitation

    SciTech Connect

    Rittman, Dylan R.; Tracy, Cameron L.; Cusick, Alex B.; Abere, Michael J.; Yalisove, Steven M.; Torralva, Ben; Ewing, Rodney C.

    2015-04-27

    In order to investigate the response of materials to extreme conditions, there are several approaches to depositing extremely high concentrations of energy into very small volumes of material, including ultrafast laser and swift heavy ion (SHI) irradiation. In this study, crystalline-to-crystalline phase transformations in cubic Gd{sub 2}O{sub 3} and monoclinic ZrO{sub 2} have been investigated using ultrafast laser irradiation. The phases produced by the extreme conditions of irradiation were characterized by grazing incidence x-ray diffraction (GIXRD) and Raman spectroscopy. Gd{sub 2}O{sub 3} exhibited a cubic-to-monoclinic phase transformation, as evidenced by the appearance of the monoclinic (402{sup ¯}), (003), (310), and (112{sup ¯}) peaks in the GIXRD pattern and of four A{sub g} and three B{sub g} Raman modes. ZrO{sub 2} underwent a monoclinic-to-tetragonal phase transformation, as evidenced by the emergence of the tetragonal (101) peak in the GIXRD pattern and of E{sub g} and A{sub 1g} Raman modes. The new phases formed by ultrafast laser irradiation are high temperature polymorphs of the two materials. No evidence of amorphization was seen in the GIXRD data, though Raman spectroscopy indicated point defect accumulation. These results are identical to those produced by irradiation with SHIs, which also deposit energy in materials primarily through electronic excitation. The similarity in damage process and material response between ultrafast laser and SHI irradiation suggests a fundamental relationship between these two techniques.

  7. Strain and mosaic deformation in laser irradiated silicon

    SciTech Connect

    Gupta, Mukul; Arora, V.; Bagchi, S.; Gupta, Ajay; Chakera, J. A.; Naik, P. A.; Chaddah, P.; Gupta, P. D.

    2012-06-05

    The effect of moderately intense ({approx}GWcm{sup -2} The effect of moderately intense ({approx}GWcm-2), 200 ps laser pulse irradiation on silicon single crystal is reported. The x-ray diffraction measurements performed on the irradiated samples reveal irreversible structural deformations. Raman spectroscopic measurements reveal substantial shift of the peak position as well as an overall broadening, pointing towards the presence of residual strain and formation of micromosaic structures on the laser induced shock recovered samples.

  8. Intravascular low-level laser irradiation in the treatment of psoriasis

    NASA Astrophysics Data System (ADS)

    Zhu, Jing; Shi, Hong-Min; Zhang, Hui-Guo; Zhang, Mei-Jue; Xu, Jian; Zhou, Min; Hu, Guo-Qiang

    1998-11-01

    Liu TCY et al have put forward the biological information model on low intensity laser irradiation (BIML): low intensity laser irradiation couples with intracellular messenger through the chromophore absorption in the cell membrane: hot-color laser irradiation activates cAMP phosphodiestererase through Gi protein, or activates phosphoinositide phospholipase C through G protein, or activates one of receptor-associated kinases: cAMP; cold- color laser irradiation activates adenylate cyclase through Gs protein: cAMP$ARUP. In this paper, under the guidance of BIML, we applied the intravascular low intensity He-He laser irradiation on blood to a patient of idiopathic edema, and succeeded.

  9. Feasibilty of exterior vascular laser irradiation therapy

    NASA Astrophysics Data System (ADS)

    Chen, Rong; Xie, Shusen; Li, Hui; Li, Buhong; Chen, Yanjiao; Zhang, Xiaodong; Chen, Huifang; Xia, Xiangnan; Lin, Aizhen

    1998-08-01

    In order to study the exterior vascular laser irradiation therapy for replacing the intravascular laser irradiation therapy, we measure the distribution of radiant fluence rate in exterior vascular laser irradiation in vivo and imitative intravascular laser irradiation. The result shows that the average radiant fluence rate of exterior vascular and intravascular is 1.11 and 10.81 respectively, which is ten times between them. In order to get the radiant fluence rate corresponding to the intravascular laser irradiation, we suggest that about 20 mW HeNe laser could be used in exterior vascular laser irradiation therapy, and the laser must irradiate on the vascular perpendicularly. The suitable patient with exposed vascular must be chosen, and the diameter of the irradiated vascular is about 6 mm. Our experiment result, especially the data measured in vivo, will be useful for the research of light transport in human tissue.

  10. Generation of ultrahigh intensity laser pulses

    NASA Astrophysics Data System (ADS)

    Fisch, N. J.; Malkin, V. M.

    2003-05-01

    Mainly due to the method of chirped pulse amplification, laser intensities have grown remarkably during recent years. However, the attaining of very much higher powers is limited by the material properties of gratings. These limitations might be overcome through the use of plasma, which is an ideal medium for processing very high power and very high total energy. A plasma can be irradiated by a long pump laser pulse, carrying significant energy, which is then quickly depleted in the plasma by a short counterpropagating pulse. This counterpropagating wave effect has already been employed in Raman amplifiers using gases or plasmas at low laser power. Of particular interest here are the new effects which enter in high power regimes. These new effects can be employed so that one high-energy optical system can be used like a flashlamp in what amounts to pumping the plasma, and a second low-power optical system can be used to extract quickly the energy from the plasma and focus it precisely. The combined system can be very compact. Thus, focused intensities more than 1025 W/cm2 can be contemplated using existing optical elements. These intensities are several orders of magnitude higher than what is currently available through chirped pump amplifiers.

  11. High intensity, argon ion laser-jet photochemistry

    NASA Astrophysics Data System (ADS)

    Wilson, R. Marshall; Schnapp, Karlyn A.; Hannemann, Klaus; Ho, Douglas M.; Memarian, Hamid R.; Azadnia, Ardeshir; Pinhas, Allan R.; Figley, Timothy M.

    A new technique for the study of high intensity solution photochemistry has been developed. With this laser-jet technique, a high velocity microjet is irradiated with the focussed output of an argon ion laser. Under these extremely high intensity conditions, photochemically generated transient species with suitable absorption properties are excited further and produce relatively large amounts of photoproducts which are not observed under low intensity conditions. The application of this laser-jet technique in the study of the photochemistry of radicals, biradicals, photoenols and the higher excited states of carbonyl and polycyclic aromatic compounds is described.

  12. Aluminium plasma production at high laser intensity

    SciTech Connect

    Torrisi, L.; Cutroneo, M.

    2014-02-28

    Thick and thin films of Al targets were irradiated in vacuum with iodine laser at 1315 nm wavelength, 300 ps pulse duration at a maximum intensity of about 10{sup 16} W/cm{sup 2} by varying the pulse energy and focal position. The laser-generated plasma was monitored in forward and backward directions by using ion collectors, SiC detectors, Thomson parabola spectrometer, and X-ray streak camera. Ion emission shows maximum proton energy of about 4 MeV in self-focusing conditions and a maximum Al ion energy of about 50 MeV. An evaluation of the electric field driving ions in conditions of target normal sheath acceleration is given.

  13. Advanced targets preparation for TNSA laser irradiation and their characterization

    NASA Astrophysics Data System (ADS)

    Ceccio, G.; Torrisi, L.; Cutroneo, M.

    2016-04-01

    Thin targets have been investigated at low laser intensity in order to prepare foils for TNSA (Target Normal Sheath Acceleration) laser irradiation at high intensity. Foils were prepared with different techniques, such as deposition of metallic nanoparticles on polymeric substrates. Polymer films were covered by solutions containing nanoparticles or embedded inside or covered by nanostructures. Such advanced targets permit to enhance the laser wavelength absorbance. Thick and thin targets were irradiated using laser radiation at 1010 W/cm2 intensity and prepared to be submitted to laser irradiation at higher intensity. The foils were characterized by optical measurements of absorbance and transmittance as a function of wavelength in the regions UV, VIS and IR. Laser irradiation measurements using a Nd:YAG laser simulate the prepulse of high laser intensity. Accelerated ions were measured with ion collectors using time of flight techniques. The protons and ions acceleration and their yields were measured as a function of the equivalent atomic number of the foils and of other characteristics, as it will be presented and discussed.

  14. Molecules and Clusters in Intense Laser Fields

    NASA Astrophysics Data System (ADS)

    Posthumus, Jan

    2009-09-01

    Preface; 1. Ultra-high intensity based on Ti:Sapphire Philip F. Taday and Andrew J. Langley; 2. Diatomic molecules in intense laser fields Jan H. Posthumus and James F. McCann; 3. Small polyatomic molecules in intense laser fields C. Cornaggia; 4. Coherent control in intense laser fields Eric Charron and Brian Sheehy; 5. Experimental studies of laser-heated rare gas clusters M. Lezius and M. Schmidt; 6. Single cluster explosions and high harmonic generation John W. G. Tisch and Emma Springate; 7. Intense laser interaction with extended cluster media Roland A. Smith and Todd Ditmire.

  15. Molecules and Clusters in Intense Laser Fields

    NASA Astrophysics Data System (ADS)

    Posthumus, Jan

    2001-06-01

    Preface; 1. Ultra-high intensity based on Ti:Sapphire Philip F. Taday and Andrew J. Langley; 2. Diatomic molecules in intense laser fields Jan H. Posthumus and James F. McCann; 3. Small polyatomic molecules in intense laser fields C. Cornaggia; 4. Coherent control in intense laser fields Eric Charron and Brian Sheehy; 5. Experimental studies of laser-heated rare gas clusters M. Lezius and M. Schmidt; 6. Single cluster explosions and high harmonic generation John W. G. Tisch and Emma Springate; 7. Intense laser interaction with extended cluster media Roland A. Smith and Todd Ditmire.

  16. Photoionization of isooctane and n-octane in intense laser fields: The effect of irradiance on ionization rates and electron dynamics

    NASA Astrophysics Data System (ADS)

    Healy, Andrew T.

    Thin path length jets (60 mum) of liquid isooctane and n-octane have been photoionized with 36-70 fs pulses of 3.1 eV photons. The population of electrons ejected post ionization is investigated over a large range of ionizing irradiance, Iex, though transient absorption (TA) measurements at wavelengths in the range 570 nm (2.17 eV) to 1315 nm (0.94 eV). As Iex is varied over a range from 3 TW/cm2 to 410 TW/cm2, the dependence of the TA intensity on Iex at time delays 0.7 ps and 2.5 ps exhibits the periodic structure theoretically predicted to develop as a result of multiphoton channel closings. At low Iex (< 9 TW/cm2), TA intensity in isooctane is proportional to Inex where n = 3, consistent with non-resonant, near threshold ionization (liquid phase ionization potential = 8.6 eV). At I ex > 9 TW/cm2, n declines with increasing Iex up to Iex = 13 TW/cm2, at which point n abruptly increases to 4. The pattern is repeated at Iex > 13 TW/cm 2, albeit with n declining from 4 and then abruptly increasing to 5 as Iex becomes greater than 100 TW/cm2. A similar trend is observed in n-octane. The decay of the TA intensity in both liquids has been measured from 0.50 ps to 180 ps over the same range of irradiance. Via comparison of the two liquids, and electron quenching studies, the TA at wavelengths longer than 800 nm has been assigned to be predominantly due to absorption by the electron. At the lowest irradiances, where n = 3 photons are required for photoionization, the TA decay in isooctane is characteristic of a geminate ion pair decaying via diffusive recombination in a Coulomb field. As the irradiance is increased, an early time, rapid, exponential decay of the TA begins to develop until an irradiance is reached (≅ 13 TW/cm2) at which our studies indicate that the n = 3 channel closes. At this irradiance, the TA decay returns to purely diffusive-like. As the irradiance is further increased, there is a reappearance of the early time exponential decay until the n = 4

  17. Ionization processes in the ultrashort, intense laser field interaction with large clusters

    NASA Astrophysics Data System (ADS)

    Shokri, B.; Niknam, A. R.; Smirnov, M.

    2004-03-01

    Multiple ionization of large clusters when they are irradiated by an intense ultrashort laser pulse is investigated. Different mechanisms, responsible for cluster ionization, are investigated. It is found that the ionization of large clusters, irradiated by a strong intense ultrashort laser pulse, is realized by means of the surface thermoemission.

  18. Dependence of terahertz power from laser-produced plasma on laser intensity

    SciTech Connect

    Shin, J.-H.; Zhidkov, A.; Jin, Z.; Hosokai, T.; Kodama, R.

    2012-07-11

    Power of terahertz radiation from plasma which is generated from air irradiated by coupled ({omega}, 2{omega}) femtosecond laser pulses is analyzed for high laser intensities, for which non-linear plasma effects on the pulse propagation become essential, with multidimensional particle-in-cell simulations including the self-consistent plasma kinetics. The growth rate of THz power becomes slower as the laser intensity increases. A reason of such a lowering of efficiency in THz emission is found to be ionization of air by the laser pulse, which results in poor focusing of laser pulses.

  19. SPECIAL ISSUE DEVOTED TO THE 80TH ANNIVERSARY OF ACADEMICIAN N G BASOV'S BIRTH: Emission spectra of a plasma observed upon irradiation of solid targets by high-intensity ultrashort laser pulses

    NASA Astrophysics Data System (ADS)

    Vergunova, G. A.; Ivanov, E. M.; Rozanov, Vladislav B.

    2003-02-01

    The spectral radiative losses are investigated in a plasma under conditions typical of a plasma produced upon irradiation of solid targets by high-intensity (up to 1017 W cm-2 ultrashort (10-13-10-9 s) laser pulses. The comparison of the calculated X-ray spectra with the experimental data for aluminum and carbon plasmas shows their satisfactory agreement. These studies made it possible to test the methods in use and to conclude that it is necessary to introduce supplements into the collision — radiation model for calculating the optical characteristics of a nonequilibrium plasma of complex chemical composition.

  20. Laser irradiation in Nd3+ doped strontium barium niobate glass

    NASA Astrophysics Data System (ADS)

    Haro-González, P.; Martín, I. R.; Arbelo-Jorge, E.; González-Pérez, S.; Cáceres, J. M.; Núñez, P.

    2008-07-01

    A local nanocrystalline formation in a neodymium doped strontium barium niobate (SBN) glass has been obtained under argon laser irradiation. The intense emission around 880 nm, originated from the F43/2 (F45/2) thermalized level when the glass structure changes to a glass ceramic structure due to the irradiation of the laser beam, has been studied. The intensities and lifetimes change from this level inside and outside the irradiated area made by the laser excitation. They have been analyzed and demonstrated that the desvitrification process has been successfully achieved. These results confirm that nanocrystals of SBN have been created by the laser action confirming that the transition from glass to glass ceramic has been completed. These results are in agreement with the emission properties of nanocrystals of the bulk glass ceramic sample. The present study also suggests that the SBN nanocrystal has a potential application as temperature detector.

  1. Influence of irradiation with {gamma}-ray photons on the photoluminescence of Cd{sub 0.9}Zn{sub 0.1}Te crystals preliminarily subjected to the intense radiation of a neodymium laser

    SciTech Connect

    Glinchuk, K. D.; Medvid', A. P.; Mychko, A. M.; Naseka, Yu. M.; Prokhorovich, A. V.; Strilchuk, O. M.

    2013-04-15

    The effect of the preliminary treatment of Cd{sub 0.9}Zn{sub 0.1}Te crystals with high-power pulses of neodymium laser radiation (the power density is {<=}1.8 MW/cm{sup 2}, at a wavelength of 532 nm) on the low-temperature (5 K) photoluminescence induced by {gamma}-ray radiation (the dose was {Phi}{sub {gamma}} = 5 kGy) is studied. The luminescence bands are related to radiation-stimulated donor-acceptor pairs, which include shallow neutral donors and neutral cadmium vacancies stimulated by {gamma}-ray irradiation, the transition of free electrons to neutral cadmium vacancies formed by radiation, and the annihilation of excitons bound to the above vacancies. It is shown that, in the crystals preliminarily treated with laser radiation, the intensity of the {gamma}-ray-stimulated luminescence bands is significantly lower than in crystals not subjected to laser radiation. This fact is accounted for by a decrease in the concentration of cadmium vacancies generated by the {gamma}-ray radiation as a result of their annihilation during the course of their interaction with laser-stimulated defects, in particular, as a consequence of their recombination at laser-stimulated interstitial cadmium atoms.

  2. PAPERS DEVOTED TO THE MEMORY OF ACADEMICIAN A M PROKHOROV: Dynamics of plasma production and development in gases and transparent solids irradiated by high-intensity, tightly focused picosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Garnov, Sergei V.; Konov, Vitalii I.; Malyutin, A. A.; Tsar'kova, O. G.; Yatskovskii, I. S.; Dausinger, F.

    2003-09-01

    The results of experimental studies of the dynamics of formation and development of a laser plasma produced in microvolumes of gases (air) and transparent solids (fused silica) by high-intensity [I⋍(1-2)×1014 W cm-2], ~22-ps, 539-nm laser pulses tightly focused in a region of diameter 4 μm are presented. The spatiotemporal distributions of the refractive index and the electron density are studied by the interferometric method with a spatial resolution of ~1.6 μm and a temporal resolution of ~3 ps directly during the action of excitation picosecond laser pulses. An almost complete ionisation of the initial gas was shown to occur even in the initial stage of air plasma formation, within a few picoseconds after plasma production. The irradiation of solid transparent dielectrics (fused silica) by picosecond laser pulses resulted in a reversible production of a plasma with an electron density above 1020 cm-3, which did not cause the damage of dielectrics.

  3. Excimer laser irradiation of metal surfaces

    NASA Astrophysics Data System (ADS)

    Kinsman, Grant

    In this work a new method of enhancing CO2 laser processing by modifying the radiative properties of a metal surface is studied. In this procedure, an excimer laser (XeCl) or KrF) exposes the metal surface to overlapping pulses of high intensity, 10(exp 8) - 10(exp 9) W cm(exp -2), and short pulse duration, 30 nsec FWHM (Full Width Half Maximum), to promote structural and chemical change. The major processing effect at these intensities is the production of a surface plasma which can lead to the formation of a laser supported detonation wave (LSD wave). This shock wave can interact with the thin molten layer on the metal surface influencing to a varying degree surface oxidation and roughness features. The possibility of the expulsion, oxidation and redeposition of molten droplets, leading to the formation of micron thick oxide layers, is related to bulk metal properties and the incident laser intensity. A correlation is found between the expulsion of molten droplets and a Reynolds number, showing the interaction is turbulent. The permanent effects of these interactions on metal surfaces are observed through scanning electron microscopy (SEM), transient calorimetric measurements and Fourier transform infrared (FTIR) spectroscopy. Observed surface textures are related to the scanning procedures used to irradiate the metal surface. Fundamental radiative properties of a metal surface, the total hemispherical emissivity, the near-normal spectral absorptivity, and others are examined in this study as they are affected by excimer laser radiation. It is determined that for heavily exposed Al surface, alpha' (10.6 microns) can be increased to values close to unity. Data relating to material removal rates and chemical surface modification for excimer laser radiation is also discussed. The resultant reduction in the near-normal reflectivity solves the fundamental problem of coupling laser radiation into highly reflective and conductive metals such as copper and aluminum. The

  4. Backscattering measuring system for optimization of intravenous laser irradiation dose

    NASA Astrophysics Data System (ADS)

    Rusina, Tatyana V.; Popov, V. D.; Melnik, Ivan S.; Dets, Sergiy M.

    1996-11-01

    Intravenous laser blood irradiation as an effective method of biostimulation and physiotherapy becomes a more popular procedure. Optimal irradiation conditions for each patient are needed to be established individually. A fiber optics feedback system combined with conventional intravenous laser irradiation system was developed to control of irradiation process. The system consists of He-Ne laser, fiber optics probe and signal analyzer. Intravenous blood irradiation was performed in 7 healthy volunteers and 19 patients with different diseases. Measurements in vivo were related to in vitro blood irradiation which was performed in the same conditions with force-circulated venous blood. Comparison of temporal variations of backscattered light during all irradiation procedures has shown a strong discrepancy on optical properties of blood in patients with various health disorders since second procedure. The best cure effect was achieved when intensity of backscattered light was constant during at least five minutes. As a result, the optical irradiation does was considered to be equal 20 minutes' exposure of 3 mW He-Ne laser light at the end of fourth procedure.

  5. Continuous wave laser irradiation of explosives

    SciTech Connect

    McGrane, Shawn D.; Moore, David S.

    2010-12-01

    Quantitative measurements of the levels of continuous wave (CW) laser light that can be safely applied to bare explosives during contact operations were obtained at 532 nm, 785 nm, and 1550 nm wavelengths. A thermal camera was used to record the temperature of explosive pressed pellets and single crystals while they were irradiated using a measured laser power and laser spot size. A visible light image of the sample surface was obtained before and after the laser irradiation. Laser irradiation thresholds were obtained for the onset of any visible change to the explosive sample and for the onset of any visible chemical reaction. Deflagration to detonation transitions were not observed using any of these CW laser wavelengths on single crystals or pressed pellets in the unconfined geometry tested. Except for the photochemistry of DAAF, TATB and PBX 9502, all reactions appeared to be thermal using a 532 nm wavelength laser. For a 1550 nm wavelength laser, no photochemistry was evident, but the laser power thresholds for thermal damage in some of the materials were significantly lower than for the 532 nm laser wavelength. No reactions were observed in any of the studied explosives using the available 300 mW laser at 785 nm wavelength. Tables of laser irradiance damage and reaction thresholds are presented for pressed pellets of PBX9501, PBX9502, Composition B, HMX, TATB, RDX, DAAF, PETN, and TNT and single crystals of RDX, HMX, and PETN for each of the laser wavelengths.

  6. Cluster ion control by simultaneous irradiations of femtosecond laser and nanosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Kamada, H.; Hiratani, Y.; Toyoda, K.

    2002-09-01

    Generation of multiply charged ions and molecular ions have been investigated using simultaneous irradiation of high intensity and ultrashort pulse of Ti:sapphire laser and fourth harmonics of Q-switched nanosecond pulse of Nd:YAG laser on carbon targets [Morimoto et al., in: Proceedings of the 13th International Conference on High-Power Particles Beams (BEAMS2000),Vol. PB-89, Nagaoka, 2000, p. 359; Toyoda et al., in: Proceedings of the 8th International Symposium on Gas Flow and Chemical Lasers and High-Power Laser Conference (GCL-HPL2000), Vol. P1.60, 2000, p. 101]. The ion current waveforms have been analyzed by means of time-of-flight (tof) mass measurement. Simultaneous irradiation of high intensity and ultrashort pulse of Ti:sapphire laser and fourth harmonics of Q-switched nanosecond pulse of Nd:YAG laser on carbon targets was found to generate molecular ions of carbon.

  7. Functional assessment of laser irradiation

    NASA Astrophysics Data System (ADS)

    Robbins, David O.

    1988-03-01

    Exposure of the fovea to intense coherent light can produce either transient or permanent changes in the eye's ability to resolve fine spatial detail. Permanent functional changes can occur in the absence of gross morphological damage and at power densities below the ED50 level. Furthermore, the eye may become increasingly susceptible to damage after repeated low-level exposures which initially produce only transient effects. Independent of any long-term hazards, laser exposures can also disrupt visual/motor behavior for periods of up to 96 hrs

  8. Surface plasma wave excitation via laser irradiated overdense plasma foil

    SciTech Connect

    Kumar, Pawan; Tripathi, V. K.

    2012-04-09

    A laser irradiated overdense plasma foil is seen to be susceptible to parametric excitation of surface plasma wave (SPW) and ion acoustic wave (IAW) on the ion plasma period time scale. The SPW is localised near the front surface of the foil while IAW extends upto the rear. The evanescent laser field and the SPW exert a ponderomotive force on electrons driving the IAW. The density perturbation associated with the latter beats with the laser induced oscillatory electron velocity to drive the SPW. At relativistic laser intensity, the growth rate is of the order of ion plasma frequency.

  9. Effect of laser intensity on the characteristic of inkjet-printed silver nanoparticles during continuous laser sintering.

    PubMed

    Moon, Yoon Jae; Kang, Heuiseok; Kang, Kyungtae; Hwang, Jun Young; Lee, Jae-Heon; Moon, Seung-Jae

    2014-11-01

    The variation in electric conductivity was examined for laser irradiation with various beam intensities. A 532-nm continuous wave laser was irradiated onto inkjet-printed silver lines on a glass substrate and the electrical resistance was measured in situ during the irradiation. The results demonstrate that electrical conductivity varies nonlinearly with laser intensity, and has a minimum specific resistance of 3.1 x 10(-8) Ωm at 4 kW/cm2 irradiation. These results are interesting because the specific resistance achieved by the present laser irradiation was approximately 1.9 times lower than the best value obtainable by oven heating, even though it was still higher by 1.9 times than that of bulk silver. It is also demonstrated that the irradiation time required to complete the sintering process decreases with laser intensity. The numerical simulation of laser heating shows that the heating temperature could be as high as 250 degrees C for laser sintering, while it is limited to 250 degrees C for oven sintering. The characteristics of sintering with laser intensity based on the results of field emission scanning electron microscope images are discussed. PMID:25958575

  10. He-Ne laser extravascular irradiation therapy

    NASA Astrophysics Data System (ADS)

    Chen, Rong; Chen, Huifang; Xie, Shusen; Chen, Yanjiao; Zhang, Yanrong

    2000-10-01

    Based on the study of tissue optics related with the laser irradiation blood therapy, a new treatment method, extravascular low-level laser irradiation therapy (ELLLI) is developed. The veins of 30 patients with cerebrovascular disease combined with diabetes, asthma were treated by He-Ne laser (632.8nm, 25mW) which was delivered by an optics fiber. The fiber was outside the patient's skin and the laser irradiated on the blood vessel perpendicularly. The therapy time was 60 minutes each time and about 7-10 times a course of the treatment. The values of blood sugar, blood- fat and hemorrheology were measured as the effective indexes. After the treatment the effective indexes and the symptoms of the patients were all improved. With the advantages of simplicity and safety (no medical infection), laser extravascular irradiation therapy is likely to be a new medical method for heart brain and other diseases.

  11. Direct heating of compressed core by ultra-intense laser

    NASA Astrophysics Data System (ADS)

    Sunahara, A.; Johzaki, T.; Sakagami, H.; Nagatomo, H.; Mima, K.; Abe, Y.; Arikawa, Y.; Fujioka, S.; Shiraga, H.; Azechi, H.; Mori, Y.; Sentoku, Y.; Kitagawa, Y.

    2016-05-01

    We propose a new scheme for heating an imploded core in the fast-ignition scheme. In this method, a heating laser irradiates an imploded core plasma directly. The accelerated fast-ions as well as fast-electrons heat the core. Two-dimensional particle in cell (PIC) simulation confirmed that carbon C6+ and deuteron D+ ions were accelerated as well as fast electrons when ultra-intense laser irradiates the CD plasma. In order to estimate the temperature scaling of the heated core in this scheme, we conducted transport simulations in the one-dimensional conical geometry. Our results show that 5 keV of ignition temperature can be achieved at the intensity of 1021 W/cm2, and 1.5 ps pulse for the compressed CD plasma with 10g/cm3 density.

  12. Intense laser ionization of transiently aligned CO

    SciTech Connect

    Pinkham, D.; Jones, R.R.

    2005-08-15

    We have measured the ionization rate for CO molecules exposed to intense 30 fsec 780 nm laser pulses as a function of the angle between the molecular and laser polarization axes. Nonionizing, 70 fsec laser pulses are used to coherently prepare the molecules, preferentially aligning them for the strong-field ionization experiments. We find a 2:1 ionization-rate ratio for molecules aligned parallel or perpendicular to the ionizing field.

  13. Study on elucidation of bactericidal effects induced by laser beam irradiation Measurement of dynamic stress on laser irradiated surface

    NASA Astrophysics Data System (ADS)

    Furumoto, Tatsuaki; Kasai, Atsushi; Tachiya, Hiroshi; Hosokawa, Akira; Ueda, Takashi

    2010-09-01

    In dental treatment, many types of laser beams have been used for various surgical treatments, and the influences of laser beam irradiation on bactericidal effect have been investigated. However, most of the work has been performed by irradiating to an agar plate with the colony of bacteria, and very few studies have been reported on the physical mechanism of bactericidal effects induced by laser beam irradiation. This paper deals with the measurement of dynamic stress induced in extracted human enamel by irradiation with Nd:YAG laser beams. Laser beams can be delivered to the enamel surface through a quartz optical fiber. Dynamic stress induced in the specimen using elastic wave propagation in a cylindrical long bar made of aluminum alloy is measured. Laser induced stress intensity is evaluated from dynamic strain measured by small semiconductor strain gauges. Carbon powder and titanium dioxide powder were applied to the human enamel surface as absorbents. Additionally, the phenomenon of laser beam irradiation to the human enamel surface was observed with an ultrahigh speed video camera. Results showed that a plasma was generated on the enamel surface during laser beam irradiation, and the melted tissues were scattered in the vertical direction against the enamel surface with a mushroom-like wave. Averaged scattering velocity of the melted tissues was 25.2 m/s. Induced dynamic stress on the enamel surface increased with increasing laser energy in each absorbent. Induced dynamic stresses with titanium dioxide powder were superior to those with carbon powder. Induced dynamic stress was related to volume of prepared cavity, and induced stress for the removal of unit volume of human enamel was 0.03 Pa/mm 3.

  14. Interaction of plasmas with intense lasers

    SciTech Connect

    Kruer, William L.

    2000-06-01

    The interaction of plasmas with intense lasers is an excellent example of how different fields of physics are interconnected. Invention of the laser and its ongoing development has allowed the creation and study of high temperature, dense matter in the laboratory. The results both advance the underlying plasma science and are relevant to many fields ranging from astrophysics to fusion and nonlinear physics. A brief overview of the interaction physics is given. Selected topics are discussed to illustrate the exciting progress in experimental, theoretical, and computational investigations with focused laser intensities up to 10{sup 21} W/cm{sup 2}. (c) 2000 American Institute of Physics.

  15. Optimal irradiance for sintering of inkjet-printed Ag electrodes with a 532nm CW laser

    NASA Astrophysics Data System (ADS)

    Moon, Yoon Jae; Kang, Heuiseok; Kang, Kyungtae; Hwang, Jun Young; Moon, Seung Jae

    2013-09-01

    Industrial solar cell fabrication generally adopts printing process to deposit the front electrodes, which needs additional heat treatment after printing to enhance electrical conductivity. As a heating method, laser irradiation draws attention not only because of its special selectivity, but also because of its intense heating to achieve high electric conductivity which is essential to reduce ohmic loss of solar cells. In this study, variation of electric conductivity was examined with laser irradiation having various beam intensity. 532 nm continuous wave (CW) laser was irradiated on inkjet-printed silver lines on glass substrate and electrical resistance was measured in situ during the irradiation. The results demonstrate that electric conductivity varies nonlinearly with laser intensity, having minimum specific resistance of 4.1 x 10-8 Ωm at 529 W/cm2 irradiation. The results is interesting because the specific resistance achieved by the present laser irradiation was about 1.8 times lower than the best value obtainable by oven heating, even though it was still higher by 2.5 times than that of bulk silver. It is also demonstrated that the irradiation time, needed to finish sintering process, decreases with laser intensity. The numerical simulation of laser heating showed that the optimal heating temperature could be as high as 300 oC for laser sintering, while it was limited to 250 oC for oven sintering. The nonlinear response of sintering with heating intensity was discussed, based on the results of FESEM images and XRD analysis.

  16. Nanoimprint lithography using IR laser irradiation

    NASA Astrophysics Data System (ADS)

    Grigaliūnas, V.; Tamulevičius, S.; Muehlberger, M.; Jucius, D.; Guobienė, A.; Kopustinskas, V.; Gudonytė, A.

    2006-11-01

    A new technique called "infrared laser-assisted nanoimprint lithography" was utilised to soften the thermoplastic polymer material mR-I 8020 during nanoimprint lithography. A laser setup and a sample holder with pressure and temperature control were designed for the imprint experiments. The polymer was spin coated onto crystalline Si <1 1 1> substrates. A prepatterned Si <1 1 1> substrate, which is transparent for the CO 2 laser irradiation, was used as an imprint stamp as well. It was shown, that the thermoplastic resist mR-I 8020 could be successfully imprinted using the infrared CW CO 2 laser irradiation ( λ = 10.6 μm). The etching rate of the CO 2 laser beam irradiated mR-I 8020 resist film under O 2 RF (13.56 MHz) plasma treatment and during O 2 reactive ion beam etching was investigated as well.

  17. Plasma optical modulators for intense lasers

    NASA Astrophysics Data System (ADS)

    Yu, Lu-Le; Zhao, Yao; Qian, Lie-Jia; Chen, Min; Weng, Su-Ming; Sheng, Zheng-Ming; Jaroszynski, D. A.; Mori, W. B.; Zhang, Jie

    2016-06-01

    Optical modulators can have high modulation speed and broad bandwidth, while being compact. However, these optical modulators usually work for low-intensity light beams. Here we present an ultrafast, plasma-based optical modulator, which can directly modulate high-power lasers with intensity up to 1016 W cm-2 to produce an extremely broad spectrum with a fractional bandwidth over 100%, extending to the mid-infrared regime in the low-frequency side. This concept relies on two co-propagating laser pulses in a sub-millimetre-scale underdense plasma, where a drive laser pulse first excites an electron plasma wave in its wake while a following carrier laser pulse is modulated by the plasma wave. The laser and plasma parameters suitable for the modulator to work are based on numerical simulations.

  18. Plasma optical modulators for intense lasers

    PubMed Central

    Yu, Lu-Le; Zhao, Yao; Qian, Lie-Jia; Chen, Min; Weng, Su-Ming; Sheng, Zheng-Ming; Jaroszynski, D. A.; Mori, W. B.; Zhang, Jie

    2016-01-01

    Optical modulators can have high modulation speed and broad bandwidth, while being compact. However, these optical modulators usually work for low-intensity light beams. Here we present an ultrafast, plasma-based optical modulator, which can directly modulate high-power lasers with intensity up to 1016 W cm−2 to produce an extremely broad spectrum with a fractional bandwidth over 100%, extending to the mid-infrared regime in the low-frequency side. This concept relies on two co-propagating laser pulses in a sub-millimetre-scale underdense plasma, where a drive laser pulse first excites an electron plasma wave in its wake while a following carrier laser pulse is modulated by the plasma wave. The laser and plasma parameters suitable for the modulator to work are based on numerical simulations. PMID:27283369

  19. Plasma optical modulators for intense lasers.

    PubMed

    Yu, Lu-Le; Zhao, Yao; Qian, Lie-Jia; Chen, Min; Weng, Su-Ming; Sheng, Zheng-Ming; Jaroszynski, D A; Mori, W B; Zhang, Jie

    2016-01-01

    Optical modulators can have high modulation speed and broad bandwidth, while being compact. However, these optical modulators usually work for low-intensity light beams. Here we present an ultrafast, plasma-based optical modulator, which can directly modulate high-power lasers with intensity up to 10(16) W cm(-2) to produce an extremely broad spectrum with a fractional bandwidth over 100%, extending to the mid-infrared regime in the low-frequency side. This concept relies on two co-propagating laser pulses in a sub-millimetre-scale underdense plasma, where a drive laser pulse first excites an electron plasma wave in its wake while a following carrier laser pulse is modulated by the plasma wave. The laser and plasma parameters suitable for the modulator to work are based on numerical simulations. PMID:27283369

  20. Plasma discreteness effects in the presence of an intense, ultrashort laser pulse

    SciTech Connect

    Savchenko, V.I.; Fisch, N.J.

    1996-03-01

    Discrete effects of the plasma irradiated by an ultrashort, intense laser pulse are investigated. Although, for most plasmas of interest, the damping of the laser pulse is due to collective plasma effects, in certain regimes the energy absorbed in the plasma microfields can be important. A scattering matrix is derived for an electron scattering off an ion in the presence of an intense laser field.

  1. Flexible gratings fabricated in polymeric plate using femtosecond laser irradiation

    NASA Astrophysics Data System (ADS)

    Park, Jung-Kyu; Cho, Sung-Hak

    2011-05-01

    Flexible gratings embedded in poly-dimethlysiloxane (PDMS) were fabricated using femtosecond laser pulses. Photo-induced gratings in a flexible PDMS plate were directly written by a high-intensity femtosecond (130 fs) Ti: Sapphire laser ( λp=800 nm). Refractive index modifications with 4 μm diameters were photo-induced after irradiation of the femtosecond pulses with peak intensities of more than 1×10 11 W/cm 2. The graded refractive index profile was fabricated to be symmetric around the center of the focal point. The diffraction efficiency of the grating samples is measured by an He-Ne laser. The maximum value of refractive index change (Δ n) in the laser-modified regions was estimated to be approximately 3.17×10 -3.

  2. Effects of Laser Irradiation on Peripheral Nerve

    NASA Astrophysics Data System (ADS)

    Baxter, G. D.; Chow, R.; Armati, P.; Bjordal, J. M.; Laakso, L.

    2009-06-01

    A literature review was undertaken to determine the electrophysiological effects of Laser Irradiation (LI) on peripheral mammalian nerves, as a means of elucidating the potential mechanisms underlying pain relief associated with laser therapy. Relevant computerized databases and reference lists were searched, and experts consulted for further articles. A total of 38 studies, comprising 82 separate experiments were identified. In human studies, all types of LI (red and infrared, pulsed and cw) slowed nerve conduction velocity, and reduced compound action potential of irradiated nerves. In animal studies, infrared LI suppressed conduction velocity, as well as noxious stimulation evoked potential. This review thus indicates the potential of laser irradiation to inhibit activity in peripheral nerves, and highlights one potential mechanism of action for laser-mediated pain relief.

  3. Zeeman effect induced by intense laser light.

    PubMed

    Stambulchik, E; Maron, Y

    2014-08-22

    We analyze spectral line shapes of hydrogenlike species subjected to fields of electromagnetic waves. It is shown that the magnetic component of an electromagnetic wave may significantly influence the spectra. In particular, the Zeeman effect induced by a visible or infrared light can be experimentally observed using present-day powerful lasers. In addition, the effect may be used for diagnostics of focused beam intensities achieved at existing and newly built laser facilities. PMID:25192094

  4. Detecting radiation reaction at moderate laser intensities.

    PubMed

    Heinzl, Thomas; Harvey, Chris; Ilderton, Anton; Marklund, Mattias; Bulanov, Stepan S; Rykovanov, Sergey; Schroeder, Carl B; Esarey, Eric; Leemans, Wim P

    2015-02-01

    We propose a new method of detecting radiation reaction effects in the motion of particles subjected to laser pulses of moderate intensity and long duration. The effect becomes sizable for particles that gain almost no energy through the interaction with the laser pulse. Hence, there are regions of parameter space in which radiation reaction is actually the dominant influence on charged particle motion. PMID:25768626

  5. Lasers and Intense Pulsed Light Hidradenitis Suppurativa.

    PubMed

    Saunte, Ditte M; Lapins, Jan

    2016-01-01

    Lasers and intense pulsed light (IPL) treatment are useful for the treatment of hidradenitis suppurativa (HS). Carbon dioxide lasers are used for cutting or vaporization of the affected area. It is a effective therapy for the management of severe and recalcitrant HS with persistent sinus tract and scarring, and can be performed under local anesthesia. HS has a follicular pathogenesis. Lasers and IPL targeting the hair have been found useful in treating HS by reducing the numbers of hairs in areas with HS. The methods have few side effects, but the studies are preliminary and need to be repeated. PMID:26617364

  6. Evaporation of solids by pulsed laser irradiation

    NASA Astrophysics Data System (ADS)

    Stafast, H.; Von Przychowski, M.

    The focused beam of a KrF laser (248 nm) has been applied to irradiate targets of Al 2O 3, SiC, graphite, Pb, Ni, Cr, quartz, and NaCl at variable laser energy flux is the range 0-13 J/cm 2. The amount of target material ejected into the vacuum (background pressure about 8 × 10 -4 Torr) was determined from the target weight before and after laser irradiation. The average number of particles (formula weight) evaporated per laser pulse and per unit of irradiated target area is non-linearly dependent on the laser energy flux. The evaporation of Al 2O 3, SiC, and graphite is showing a well-defined flux threshold while the vaporization of Pb, Ni and Cr is rising smoothly with increasing flux. With both groups of materials laser evaporation is monotonically increasing with the laser energy flux. NaCl and quartz, on the other hand, are showing an intermediate maximum in the laser vaporization efficiency.

  7. Fundamental Physics Explored with High Intensity Laser

    NASA Astrophysics Data System (ADS)

    Tajima, T.; Homma, K.

    2012-10-01

    Over the last century the method of particle acceleration to high energies has become the prime approach to explore the fundamental nature of matter in laboratory. It appears that the latest search of the contemporary accelerator based on the colliders shows a sign of saturation (or at least a slow-down) in increasing its energy and other necessary parameters to extend this frontier. We suggest two pronged approach enabled by the recent progress in high intensity lasers. First we envision the laser-driven plasma accelerator may be able to extend the reach of the collider. For this approach to bear fruit, we need to develop the technology of high averaged power laser in addition to the high intensity. For this we mention that the latest research effort of ICAN is an encouraging sign. In addition to this, we now introduce the concept of the noncollider paradigm in exploring fundamental physics with high intensity (and large energy) lasers. One of the examples we mention is the laser wakefield acceleration (LWFA) far beyond TeV without large luminosity. If we relax or do not require the large luminosity necessary for colliders, but solely in ultrahigh energy frontier, we are still capable of exploring such a fundamental issue. Given such a high energetic particle source and high-intensity laser fields simultaneously, we expect to be able to access new aspects on the matter and the vacuum structure from fundamental physical point of views. LWFA naturally exploits the nonlinear optical effects in the plasma when it becomes of relativistic intensity. Normally nonlinear optical effects are discussed based upon polarization susceptibility of matter to external fields. We suggest application of this concept even to the vacuum structure as a new kind of order parameter to discuss vacuum-originating phenomena at semimacroscopic scales. This viewpoint unifies the following observables with the unprecedented experimental environment we envision; the dispersion relation of

  8. LPI studies with grazing incidence irradiation at the Nike laser

    NASA Astrophysics Data System (ADS)

    Weaver, J.; Kehne, D.; Schmitt, A.; Obenschain, S.; Serlin, V.; Oh, J.; Lehmberg, R.; Seely, J.

    2013-10-01

    Studies of laser plasma instabilities (LPI) at the Nike laser facility at NRL have previously concentrated on planar targets irradiated with their surface normal aligned to the central axis of the laser. Shots with planar targets rotated up 60° to the laser have shown changes in thresholds for the two-plasmon decay instability and stimulated Raman scattering near the quarter critical region. In the case of rotated low-Z targets, spectra were observed to shift to lower wavelength and were substantially stronger in the visible and ultraviolet spectral ranges. The low-Z target data show growth at an incident intensity slightly below (~30%) the threshold values observed at normal incidence. A rapid rise in signal level over the same laser intensities was also observed in the hard x-ray data which serve as an overall indicator of LPI activity. Shots with rotated planar high-Z targets showed that the visible and ultraviolet emissions dropped significantly when compared to low-Z targets in the same geometry. This presentation will include results from upcoming experiments to determine the LPI signal for low-Z, high-Z, and high-Z coated targets at lower laser intensities for several angles of target rotation. Shots with widely separated laser beams are also planned to explore cross beam energy transport at Nike. Work supported by DoE/NNSA.

  9. Photoacoustic spectroscopy applied to the study of the influence of laser irradiation on corn seeds

    NASA Astrophysics Data System (ADS)

    Hernández Aguilar, C.; Carballo C., A.; Cruz-Orea, A.; Ivanov, R.; San Martín Martínez, E.; Michtchenko, A.

    2005-06-01

    In the present study we were interested in the effects of low intensity laser irradiation on hybrid corn seeds CL1 x CL4 when these seeds were exposed to different laser intensities and irradiation times. In order to observe qualitative differences in chlorophyll a and b optical absorption spectra of seedling’s leaves, whose seeds were irradiated and non irradiated, were obtained by using photoacoustic spectroscopy (PAS). A randomized complete blocks experimental design with three replications was used. The experimental unit included 10 seeds, from which we randomly choose three seedlings. The variance analysis (ANOVA) for both chlorophylls revealed significant (P < 0.05) differences among treatments

  10. Ion acceleration using high-contrast ultra-intense lasers

    NASA Astrophysics Data System (ADS)

    Fuchs, J.; Antici, P.; D'Humières, E.; Lefebvre, E.; Borghesi, M.; Brambrink, E.; Cecchetti, C.; Toncian, T.; Pépin, H.; Audebert, P.

    2006-06-01

    We have compared the acceleration of high-energy ions from the rear-surface of thin foils for various contrast conditions of the ultra-intense laser pulse irradiating the targets. The experiments were performed using the LULI 100 TW facility. We used Al targets of variable thicknesses and the laser pulse contrast ratio ahead of the main pulse was varied using either a fast Pockels cell or a single or double plasma mirror. The latter was installed at an intermediate field position, in between the focusing optics and the target, so that its effect was optimized. By improving with these two methods the laser pulse contrast, we have observed that we could significantly reduce the thickness of the target used for proton acceleration and at the same time increase both the cut-off energy of the accelerated protons and the energy conversion efficiency of the process.

  11. Radiative trapping in intense laser beams

    NASA Astrophysics Data System (ADS)

    Kirk, J. G.

    2016-08-01

    The dynamics of electrons in counter-propagating, circularly polarized laser beams are shown to exhibit attractors whose ability to trap particles depends on the ratio of the beam intensities and a single parameter describing radiation reaction. Analytical expressions are found for the underlying limit cycles and the parameter range in which they are stable. In high-intensity optical pulses, where radiation reaction strongly modifies the trajectories, the production of collimated gamma-rays and the initiation of non-linear cascades of electron–positron pairs can be optimized by a suitable choice of the intensity ratio.

  12. Molecular dynamic studies on anisotropic explosion of laser irradiated Xe cluster

    SciTech Connect

    Mishra, Gaurav; Gupta, N. K.

    2012-09-15

    A three dimensional molecular dynamic model is used to investigate the dynamics of Xe clusters of various radii irradiated by laser of moderate intensities ({approx}10{sup 14}-10{sup 16}W/cm{sup 2}). The FWHM pulse duration of the laser is varied from few laser cycles to hundreds of femtosecond. For cluster of radius 50 A irradiated by a laser of 170 fs pulse duration, it is observed that ion yield is more along the direction of laser polarization than perpendicular to it. This trend reverses (more ions are emitted along the direction perpendicular to laser polarization than parallel to it) when laser pulses of few cycles are used. This reversal of anisotropy is explained on the basis of spatial shielding of ions due to the oscillating inner electron cloud along direction of laser electric field. The nature of anisotropy remains same with variations in laser intensity and cluster size.

  13. Damage thresholds in laser irradiated optical materials

    SciTech Connect

    Guignard, F.; Autric, M.; Baudinaud, V.

    1997-12-01

    An experimental study on the damage induced by laser irradiation on different materials, borosilicate glass, fused silicate, moulded and stretched polymethylmethacrylate (PMMA), has been performed. The irradiation source is a 1KJ pulsed cold cathode electron gun preionized TEA CO{sub 2} laser. Damage mechanisms are controlled by the in-depth absorption of the 10,6 {mu}m radiation according to the Beer-Lambert law. The heating of the interaction area gives rise to thermal or thermo-mechanical damages. PMMA is damaged following a boiling process. Stretched PMMA is fractured first, releasing stresses, then boiled like moulded PMMA at higher energy. BK7 crazed after the irradiation due to thermomechanical stresses, silicate melt and vaporized. Optical damages have been characterized by measuring the contrast transfer function through the irradiated samples.

  14. Relativistic plasma astrophysics with intense lasers

    NASA Astrophysics Data System (ADS)

    Kuramitsu, Yasuhiro; Chu, Hsu-Hsin; Hau, Lin-Ni; Chen, Shih-Hung; Liu, Yao-Li; Hsieh, Chia-Ying; Sakawa, Youichi; Hideaki, Takabe; Wang, Jyhpyng

    2015-12-01

    Recent progresses of laser technologies enable us to investigate space and astrophysical phenomena in laboratories. In space plasmas the local observations by spacecrafts provide us the microscopic information of the plasma and electric/magnetic fields, however, it is difficult to obtain the global structures of the phenomena. In astrophysical plasmas, in contrast, global images provide us the macroscopic information, although there is no local observation and thus no microscopic information. Laboratory experiments on space and astrophysical phenomena provide us the local and global information simultaneously. We have investigated so far mostly non-relativistic phenomena in the universe with long laser pulses. Now we extend our research from non-relativistic to relativistic regime with an ultra intense laser, the 100 TW laser facility at National Central University. We introduce our facility and model relativistic phenomena in laboratory, focusing on the magnetic field generation and the magnetic reconnection in the universe.

  15. Polyethylene welding by pulsed visible laser irradiation

    NASA Astrophysics Data System (ADS)

    Torrisi, L.; Caridi, F.; Visco, A. M.; Campo, N.

    2011-01-01

    Laser welding of plastics is a relatively new process that induces locally a fast polymer heating. For most applications, the process involves directing a pulsed beam of visible light at the weld joint by going through one of the two parts. This is commonly referred to as “through transmission visible laser welding”. In this technique, the monochromatic visible light source uses a power ns pulsed laser in order to irradiate the joint through one part and the light is absorbed in the vicinity of the other part. In order to evaluate the mechanical resistance of the welded joint, mass quadrupole spectrometry, surface profilometry, microscopy techniques and mechanical shear tests were employed. The welding effect was investigated as a function of the laser irradiation time, nature of the polyethylene materials and temperature.

  16. Fourier transform infrared spectroscopy (FTIR) of laser-irradiated cementum

    NASA Astrophysics Data System (ADS)

    Rechmann, Peter; White, Joel M.; Cecchini, Silvia C. M.; Hennig, Thomas

    2003-06-01

    Utilizing Fourier Transform Infrared Spectroscopy (FTIR) in specular reflectance mode chemical changes of root cement surfaces due to laser radiation were investigated. A total of 18 samples of root cement were analyzed, six served as controls. In this study laser energies were set to those known for removal of calculus or for disinfection of periodontal pockets. Major changes in organic as well as inorganic components of the cementum were observed following Nd:YAG laser irradiation (wavelength 1064 nm, pulse duration 250 μs, free running, pulse repetition rate 20 Hz, fiber diameter 320 μm, contact mode; Iskra Twinlight, Fontona, Slovenia). Er:YAG laser irradiation (wavelength 2.94 μm, pulse duration 250 μs, free running, pulse repetition rate 6 Hz, focus diameter 620 μm, air water cooling 30 ml/min; Iskra Twinlight, Fontona, Slovenia) significantly reduced the Amid bands due to changes in the organic components. After irradiation with a frequency doubled Alexandrite laser (wavelength 377 nm, pulse duration 200 ns, q-switched, pulse repetition rate 20 Hz, beam diameter 800 μm, contact mode, water cooling 30 ml/min; laboratory prototype) only minimal reductions in the peak intensity of the Amide-II band were detected.

  17. Transverse intensity transformation by laser amplifiers

    NASA Astrophysics Data System (ADS)

    Litvin, Igor A.; King, Gary; Collett, Oliver J. P.; Strauss, Hencharl J.

    2015-03-01

    Lasers beams with a specific intensity profile such as super-Gaussian, Airy or Dougnut-like are desirable in many applications such as laser materials processing, medicine and communications. We propose a new technique for laser beam shaping by amplifying a beam in an end-pumped bulk amplifier that is pumped with a beam that has a modified intensity profile. Advantages of this method are that it is relatively easy to implement, has the ability to reshape multimode beams and is naturally suited to high power/energy beams. Both three and four level gain materials can be used as amplifier media. However, a big advantage of using three level materials is their ability to attenuate of the seed beam, which enhances the contrast of the shaping. We first developed a numerical method to obtain the required pump intensity for an arbitrary beam transformation. This method was subsequently experimentally verified using a three level system. The output of a 2.07 μm seed laser was amplified in a Ho:YLF bulk amplifier which was being pumped by a 1.89 μm Tm:YLF laser which had roughly a TEM10 Hermit Gaussian intensity profile. The seed beam was amplified from 0.3 W to 0.55 W at the full pump power of 35 W. More importantly, the beam profile in one transverse direction was significantly shaped from Gaussian to roughly flat-top, as the model predicted. The concept has therefore been shown to be viable and can be used to optimise the beam profile for a wide range of applications.

  18. Laser-induced fluorescence of fused silica irradiated by ArF excimer laser

    SciTech Connect

    Zhang Haibo; Yuan Zhijun; Zhou Jun; Dong Jingxing; Wei Yunrong; Lou Qihong

    2011-07-01

    Laser-induced fluorescence (LIF) of high-purity fused silica irradiated by ArF excimer laser is studied experimentally. LIF bands of the fused silica centered at 281 nm, 478 nm, and 650 nm are observed simultaneously. Furthermore, the angular distribution of the three fluorescence peaks is examined. Microscopic image of the laser modified fused silica indicates that scattering of the generated fluorescence by laser-induced damage sites is the main reason for the angular distribution of LIF signals. Finally, the dependence of LIF signals intensities of the fused silica on laser power densities is presented. LIF signals show a squared power density dependence, which indicates that laser-induced defects are formed mainly via two-photon absorption processes.

  19. Active diaphragm rupture with laser beam irradiation

    NASA Astrophysics Data System (ADS)

    Takahashi, T.; Torikai, H.; Yang, Q. S.; Watanabe, K.; Sasoh, A.

    We performed shock tube operations with a layer of diaphragm being ruptured by laser beam irradiation. Mylar or Cellophane was examined as the diaphragm material. It has been demonstrated that shock tube can be operated with this new technique. The absorbed energy depends on the material and thickness of the diaphragm and is an important control parameter.

  20. Strain engineering in graphene by laser irradiation

    SciTech Connect

    Papasimakis, N.; Mailis, S.; Huang, C. C.; Al-Saab, F.; Hewak, D. W.; Luo, Z.; Shen, Z. X.

    2015-02-09

    We demonstrate that the Raman spectrum of graphene on lithium niobate can be controlled locally by continuous exposure to laser irradiation. We interpret our results in terms of changes to doping and mechanical strain and show that our observations are consistent with light-induced gradual strain relaxation in the graphene layer.

  1. Heat profiles of laser-irradiated nails

    NASA Astrophysics Data System (ADS)

    Paasch, Uwe; Nenoff, Pietro; Seitz, Anna-Theresa; Wagner, Justinus A.; Kendler, Michael; Simon, Jan C.; Grunewald, Sonja

    2014-01-01

    Onychomycosis is a worldwide problem with no tendency for self-healing, and existing systemic treatments achieve disease-free nails in only 35 to 76% of cases. Recently, treatment of nail fungus with a near-infrared laser has been introduced. It is assumed that fungal eradication is mediated by local heat. To investigate if laser treatment has the potential to eradicate fungal hyphae and arthrospores, laser heat application and propagation needs to be studied in detail. This study aimed to measure nail temperatures using real-time videothermography during laser irradiation. Treatment was performed using 808- and 980-nm linear scanning diode lasers developed for hair removal, enabling contact-free homogeneous irradiation of a human nail plate in one pass. Average and peak temperatures increased pass by pass, while the laser beam moved along the nail plates. The achieved mean peak temperatures (808 nm: 74.1 to 112.4°C, 980 nm: 45.8 to 53.5°C), as well as the elevation of average temperatures (808 nm: 29.5 to 38.2°C, 980 nm: 27.1 to 32.6°C) were associated with pain that was equivalent to that of hair removal procedures and was not significantly different for various wavelengths. The linear scanning laser devices provide the benefits of contact-free homogeneous heating of the human nail while ensuring adequate temperature rises.

  2. System for obtaining smooth laser beams where intensity variations are reduced by spectral dispersion of the laser light (SSD)

    DOEpatents

    Skupsky, Stanley; Kessler, Terrance J.; Short, Robert W.; Craxton, Stephen; Letzring, Samuel A.; Soures, John

    1991-01-01

    In an SSD (smoothing by spectral dispersion) system which reduces the time-averaged spatial variations in intensity of the laser light to provide uniform illumination of a laser fusion target, an electro-optic phase modulator through which a laser beam passes produces a broadband output beam by imposing a frequency modulated bandwidth on the laser beam. A grating provides spatial and angular spectral dispersion of the beam. Due to the phase modulation, the frequencies ("colors") cycle across the beam. The dispersed beam may be amplified and frequency converted (e.g., tripled) in a plurality of beam lines. A distributed phase plate (DPP) in each line is irradiated by the spectrally dispersed beam and the beam is focused on the target where a smooth (uniform intensity) pattern is produced. The color cycling enhances smoothing and the use of a frequency modulated laser pulse prevents the formation of high intensity spikes which could damage the laser medium in the power amplifiers.

  3. Focusing of Intense Laser via Parabolic Plasma Concave Surface

    NASA Astrophysics Data System (ADS)

    Zhou, Weimin; Gu, Yuqiu; Wu, Fengjuan; Zhang, Zhimeng; Shan, Lianqiang; Cao, Leifeng; Zhang, Baohan

    2015-12-01

    Since laser intensity plays an important role in laser plasma interactions, a method of increasing laser intensity - focusing of an intense laser via a parabolic plasma concave surface - is proposed and investigated by three-dimensional particle-in-cell simulations. The geometric focusing via a parabolic concave surface and the temporal compression of high harmonics increased the peak intensity of the laser pulse by about two orders of magnitude. Compared with the improvement via laser optics approaches, this scheme is much more economic and appropriate for most femtosecond laser facilities. supported by National Natural Science Foundation of China (Nos. 11174259, 11175165), and the Dual Hundred Foundation of China Academy of Engineering Physics

  4. Generation of Ultra-high Intensity Laser Pulses

    SciTech Connect

    N.J. Fisch; V.M. Malkin

    2003-06-10

    Mainly due to the method of chirped pulse amplification, laser intensities have grown remarkably during recent years. However, the attaining of very much higher powers is limited by the material properties of gratings. These limitations might be overcome through the use of plasma, which is an ideal medium for processing very high power and very high total energy. A plasma can be irradiated by a long pump laser pulse, carrying significant energy, which is then quickly depleted in the plasma by a short counterpropagating pulse. This counterpropagating wave effect has already been employed in Raman amplifiers using gases or plasmas at low laser power. Of particular interest here are the new effects which enter in high power regimes. These new effects can be employed so that one high-energy optical system can be used like a flashlamp in what amounts to pumping the plasma, and a second low-power optical system can be used to extract quickly the energy from the plasma and focus it precisely. The combined system can be very compact. Thus, focused intensities more than 10{sup 25} W/cm{sup 2} can be contemplated using existing optical elements. These intensities are several orders of magnitude higher than what is currently available through chirped pump amplifiers.

  5. Propagation in compressed matter of hot electrons created by short intense lasers

    NASA Astrophysics Data System (ADS)

    Batani, D.; Bernardinello, A.; Masella, V.; Pisani, F.; Koenig, M.; Krishnan, J.; Benuzzi, A.; Ellwi, S.; Hall, T.; Norreys, P.; Djaoui, A.; Neely, D.; Rose, S.; Fews, P.; Key, M.

    1998-02-01

    We performed the first experimental study of propagation in compressed matter of hot electrons created by a short pulse intense laser. The experiment has been carried out with the VULCAN laser at Rutherford compressing plastic targets with two ns laser beams at an intensity ⩾1014W/cm2. A CPA beam with an intensity ⩾1016W/cm2 irradiated the rear side of the target and created hot electrons propagating through the compressed matter. K-α emission was used as diagnostics of hot electron penetration by putting a chloride plastic layer inside the target.

  6. Intensity dependence of relativistic focusing of intense laser beams propagating in plasmas

    SciTech Connect

    Liu Mingwei; Zhou Bingju; Yi Yougen; Liu Xiaojuan; Tang Liqiang

    2007-10-15

    Optical guiding of an intense laser beam propagating in uniform plasmas is analyzed by means of the variational method. The focusing properties of the beam are shown to be governed by the laser power as well as the laser intensity. An increase in the laser intensity leads to an enhancement of ponderomotive self-channeling but a stronger weakening of relativistic self-focusing. The oscillations of the beam spot size along the propagation distance come from the variability of the focusing force in terms of the laser intensity; and the dependence on the laser intensity is negligible in the weakly relativistic limit.

  7. Solar irradiance dictates settlement timing and intensity of marine mussels

    PubMed Central

    Fuentes-Santos, Isabel; Labarta, Uxío; Álvarez-Salgado, X. Antón; Fernández-Reiriz, Mª José

    2016-01-01

    Identifying the environmental factors driving larval settlement processes is crucial to understand the population dynamics of marine invertebrates. This work aims to go a step ahead and predict larval presence and intensity. For this purpose we consider the influence of solar irradiance, wind regime and continental runoff on the settlement processes. For the first time, we conducted a 5-years weekly monitoring of Mytilus galloprovincialis settlement on artificial suspended substrates, which allowed us to search for interannual variability in the settlement patterns. Comparison between the seasonal pattern of larval settlement and solar irradiance, as well as the well-known effect of solar irradiance on water temperature and food availability, suggest that solar irradiance indirectly influences the settlement process, and support the use of this meteorological variable to predict settlement occurrence. Our results show that solar irradiance allows predicting the beginning and end of the settlement cycle a month in advance: Particularly we have observed that solar irradiance during late winter indirectly drives the timing and intensity of the settlement onset, Finally, a functional generalise additive model, which considers the influence of solar irradiance and continental runoff on the settlement process, provides an accurate prediction of settlement intensity a fortnight in advance. PMID:27384527

  8. Solar irradiance dictates settlement timing and intensity of marine mussels.

    PubMed

    Fuentes-Santos, Isabel; Labarta, Uxío; Álvarez-Salgado, X Antón; Fernández-Reiriz, M José

    2016-01-01

    Identifying the environmental factors driving larval settlement processes is crucial to understand the population dynamics of marine invertebrates. This work aims to go a step ahead and predict larval presence and intensity. For this purpose we consider the influence of solar irradiance, wind regime and continental runoff on the settlement processes. For the first time, we conducted a 5-years weekly monitoring of Mytilus galloprovincialis settlement on artificial suspended substrates, which allowed us to search for interannual variability in the settlement patterns. Comparison between the seasonal pattern of larval settlement and solar irradiance, as well as the well-known effect of solar irradiance on water temperature and food availability, suggest that solar irradiance indirectly influences the settlement process, and support the use of this meteorological variable to predict settlement occurrence. Our results show that solar irradiance allows predicting the beginning and end of the settlement cycle a month in advance: Particularly we have observed that solar irradiance during late winter indirectly drives the timing and intensity of the settlement onset, Finally, a functional generalise additive model, which considers the influence of solar irradiance and continental runoff on the settlement process, provides an accurate prediction of settlement intensity a fortnight in advance. PMID:27384527

  9. Ultra-Intense Short-Pulse Pair Creation Using the Texas Petawatt Laser

    NASA Astrophysics Data System (ADS)

    Liang, Edison; Henderson, Alexander; Clarke, Taylor; Taylor, Devin; Chaguine, Petr; Serratto, Kristina; Riley, Nathan; Dyer, Gilliss; Donovan, Michael; Ditmire, Todd

    2013-10-01

    We report results from the 2012 pair creation experiment using the Texas Petawatt Laser. Up to 1011 positrons per steradian were detected using 100 Joule pulses from the Texas Petawatt Laser to irradiate gold targets, with peak laser intensities up to 1.9 × 1021W/cm2 and pulse durations as short as 130 fs. Positron-to-electron ratios exceeding 20% were measured on some shots. The positron energy, positron yield per unit laser energy, and inferred positron density are significantly higher than those reported in previous experiments. This confirms that, for a given laser energy, higher intensity and shorter pulses irradiating thicker targets are more favorable for pair creation. Narrow-band high-energy positrons up to 23 MeV were observed from thin targets. Supported by DOE Grant DE-SC-0001481 and Rice FIF.

  10. Liquid-xenon detector under the intensive pulse irradiation conditions

    NASA Astrophysics Data System (ADS)

    Kirsanov, M. A.

    2016-02-01

    The effect of intense pulsed irradiation on the operation of the liquid xenon spectrometer was studied. The ionization chamber filled with liquid xenon was irradiated by bremsstrahlung pulses of the microtron. The pulse repetition rate was 400 Hz. The absorbed dose ranged from 10-7 to 0.1 Gy per pulse. Stable operation of the liquid xenon spectrometer in the intervals between the pulses of the accelerator was shown for a long time.

  11. Review of Astrophysics Experiments on Intense Lasers

    SciTech Connect

    Remington, B A; Drake, R P; Takabe, H; Arnett, D

    2000-01-19

    Astrophysics has traditionally been pursued at astronomical observatories and on theorists' computers. Observations record images from space, and theoretical models are developed to explain the observations. A component often missing has been the ability to test theories and models in an experimental setting where the initial and final states are well characterized. Intense lasers are now being used to recreate aspects of astrophysical phenomena in the laboratory, allowing the creation of experimental testbeds where theory and modeling can be quantitatively tested against data. We describe here several areas of astrophysics--supernovae, supernova remnants, gamma-ray bursts, and giant planets--where laser experiments are under development to test our understanding of these phenomena.

  12. Central nervous system transplantation benefited by low-level laser irradiation

    NASA Astrophysics Data System (ADS)

    Rochkind, S.; Lubart, Rachel; Wollman, Yoram; Simantov, Rabi; Nissan, Moshe; Barr-Nea, Lilian

    1990-06-01

    Effect of low-level laser irradiation on the central nervous system transplantation is reported. Ernbryonal brain allografts were transplanted into the brain of 20 adult rats and peripheral nerve graft transplanted into the severely injured spinal cord of 16 dogs. The operated wound of 10 rats and 8 dogs were exposed daily for 21 days to lowpower laser irradiation CW HeNe laser (35 mW, 632.8 run, energy density of 30 J/cm2 at each point for rats and 70 J/cm2 at each point for dogs). This study shows that (i) the low-level laser irradiation prevents extensive glial scar formation (a limiting factor in CNS regeneration) between embryonal transplants and host brain; (ii) Dogs made paraplegic by spinal cord injury were able to walk 3-6 months later. Recovery of these dogs was effected by the implantation of a fragment of autologous sciatic nerve at the site of injury and subsequently exposing the dogs to low-level laser irradiation. The effect of laser irradiation on the embryonal nerve cells grown in tissue culture was also observed. We found that low-level laser irradiation induced intensive migration of neurites outward of the aggregates 15-22 The results of the present study and our previous investigations suggest that low-level laser irradiation is a novel tool for treatment of peripheral and central nervous system injuries.

  13. Membrane Protein Crystallization Using Laser Irradiation

    NASA Astrophysics Data System (ADS)

    Adachi, Hiroaki; Murakami, Satoshi; Niino, Ai; Matsumura, Hiroyoshi; Takano, Kazufumi; Inoue, Tsuyoshi; Mori, Yusuke; Yamaguchi, Akihito; Sasaki, Takatomo

    2004-10-01

    We demonstrate the crystallization of a membrane protein using femtosecond laser irradiation. This method, which we call the laser irradiated growth technique (LIGHT), is useful for producing AcrB crystals in a solution of low supersaturation range. LIGHT is characterized by reduced nucleation times. This feature is important for crystallizing membrane proteins because of their labile properties when solubilized as protein-detergent micelles. Using LIGHT, high-quality crystals of a membrane transporter protein, AcrB, were obtained. The resulting crystals were found to be of sufficiently high resolution for X-ray diffraction. The results reported here indicate that LIGHT is a powerful tool for membrane protein crystallization, as well as for the growth of soluble proteins.

  14. Laser Assisted Cancer Immunotherapy: Surface Irradiation

    NASA Astrophysics Data System (ADS)

    Wilson, Joshua; Chen, Hsin-Wei; Bandyopadhyay, Pradip

    2006-03-01

    Experiments in our laboratory incorporate a non-invasive approach to treat superficial tumors in animal models. Based on the concept of Laser Assisted Cancer Immunotherapy, surface irradiation provides good information to compare to invasive alternatives. The procedure involves injecting an immunoadjuvant (Glycated Chitosan) as well as a light absorbing dye (Indocyanine Green) directly into the tumor (5 to 7 mm in diameter). The temperature of the tumor is raised using an infrared diode laser operating at 804 nm, with a silica fiber tip placed a set distance away from the surface of the tumor. We monitor the surface temperature using non-invasive (infrared detector probe) as well as the internal temperature of the tumor using invasive (micro thermocouples) methods. This study aims at the success of the surface irradiation mode to treat solid tumors. * This work is supported by a grant from The National Institute of Health.

  15. Nanodot formation induced by femtosecond laser irradiation

    SciTech Connect

    Abere, M. J.; Kang, M.; Goldman, R. S.; Yalisove, S. M.; Chen, C.; Rittman, D. R.; Phillips, J. D.; Torralva, B.

    2014-10-20

    The femtosecond laser generation of ZnSe nanoscale features on ZnSe surfaces was studied. Irradiation with multiple exposures produces 10–100 nm agglomerations of nanocrystalline ZnSe while retaining the original single crystal structure of the underlying material. The structure of these nanodots was verified using a combination of scanning transmission electron microscopy, scanning electron microscopy, and atomic force microscopy. The nanodots continue to grow hours after irradiation through a combination of bulk and surface diffusion. We suggest that in nanodot formation the result of ultrafast laser induced point defect formation is more than an order of magnitude below the ZnSe ultrafast melt threshold fluence. This unique mechanism of point defect injection will be discussed.

  16. Experimental study using diode laser in discs: the healing process in discs and adjacent vertebrae after laser irradiation

    NASA Astrophysics Data System (ADS)

    Naga, Kumi; Nakai, Sadaaki; Maehara, Kazuyuki; Nishimoto, Seiji

    2004-09-01

    The direct and secondary changes following diode laser irradiation of intervertebral discs were studied in rabbits. A quartz fiber was inserted into the discs, and laser irradiation was applied. Subsequently, the lumbar vertebrae were extracted en bloc, and subjected to sagittal magnetic resonance (MR) imaging and histologic examination immediately after irradiation, and 3, 12, and 24 weeks after irradiation. MR images showed low signal intensity of the intervertebral discs on T2-weighted images 3 weeks after irradiation, which remained unchanged to 24 weeks. Although the signal intensity of the adjacent vertebral bodies remained unchanged on T1-weighted images, the intensity was high on T2-weighted images 3 weeks after irradiation, but had reverted to normal or was low 12 to 24 weeks after irradiation. On histologic examination, the inner layer of the annulus fibrosus was seen to protrude into the void created by vaporization of the nucleus pulposus 3 weeks after irradiation. Multinuclear chondrocytes were observed, as if the disc was being reconstructed. Fibrous tissue in the epiphysis and metaphysis was observed soon after irradiation but decreased over time and was replaced by normal bone marrow.

  17. Thermal Changes of Maize Seed by Laser Irradiation

    NASA Astrophysics Data System (ADS)

    Hernandez-Aguilar, C.; Dominguez-Pacheco, A.; Cruz-Orea, A.

    2015-09-01

    In this research, the thermal evolution in maize seeds ( Zea mays L.) was studied when low-intensity laser irradiation was applied during 60 s. The seeds were irradiated in three different conditions: suspended in air, placed on an aluminum surface, and finally placed on a cardboard; the evolution of the seed temperature was measured by an infrared camera. Photoacoustic spectroscopy and the Rosencwaig and Gersho model were used to determine the optical absorption coefficient (β ) of the seeds. The results indicate that using 650 nm laser light and 27.4 mW, it is possible to produce temperature changes (up to 9.06°C after 1 min) on the seeds. Comparing the mean temperature of the seeds, during and after the incidence of light from a laser, it was found that there were statistically significant differences (P≤ 0.05) from time t1 to time t_{16} (t1 to t_{16}) and t3 to t_{16}, for the laser turned on and off, respectively. The seed condition that had the highest temperature variation, relative to the initial temperature (during the irradiation laser exposure), involved the seeds suspended in air. With regard to the stage of decay of the temperature, it was found that the seed condition that decays more slowly was the seed placed on the cardboard. It was also found that black-dyed maize seeds are optically opaque in the 300 nm to 700 nm range Also, the thermal diffusion length is smaller than the optical penetration length. In the present investigation, it was shown that there is a thermal component associated with the mechanisms of laser biostimulation, which is also a function of the container materials of the seed. In this way, the effects of laser treatment on maize seeds involve at least a temperature effect. It is important to know the temperature changes in the seeds that have been irradiated with a laser beam since they could have substantial practical and theoretical importance.

  18. High-power, high-intensity laser propagation and interactions

    SciTech Connect

    Sprangle, Phillip; Hafizi, Bahman

    2014-05-15

    This paper presents overviews of a number of processes and applications associated with high-power, high-intensity lasers, and their interactions. These processes and applications include: free electron lasers, backward Raman amplification, atmospheric propagation of laser pulses, laser driven acceleration, atmospheric lasing, and remote detection of radioactivity. The interrelated physical mechanisms in the various processes are discussed.

  19. High-speed curing by laser irradiation

    NASA Astrophysics Data System (ADS)

    Decker, Christian

    1999-05-01

    Laser-assisted processing of multifunctional systems is a very efficient method for achieving high-speed curing of photosensitive resins. With acrylate functionalized monomers and polymers, crosslinking was achieved upon a few millisecond exposure to a UV laser beam, in the presence of a radical-type photoinitiator. The polymerization reaction was followed in real-time by infrared spectroscopy and shown to proceed with long kinetic chains (up to 20,000 functional groups polymerized per initiating radical). An acrylate functionalized polyester proved to be the most reactive system, with formation of a tightly cross-linked and strickly insoluble polymer. Its high sensitivity makes this photoresist particularly well suited for laser direct imaging applications. Similar results have been obtained with epoxy and vinyl ether functionalized polymers, which undergo a fast cationic polymerization in the presence of a photogenerated protonic acid. Interpenetrating polymer networks have been synthetized by laser irradiation of blends of acrylate and epoxy-functionalized oligomers to obtain polymers that combine the elastomeric character of cross-linked polyurethanes and the toughness of epoxy polymers. These laser-sensitive polymers are to be used as photoresists to produce microcircuits, as protective coatings of optical fibers, as recording media in holography and as photocurable resins in stereolithography.

  20. Effect of low-level laser irradiating point on immunity

    NASA Astrophysics Data System (ADS)

    Cai, ChangSong; Qi, Qiong-fang; Xin, Jiang

    1993-03-01

    This paper reports that cellular immune function was observed when He-Ne laser was used to irradiate `zusanli' point in rats using various power, time, and periods. The indicator was a lymphocyte transformation test (LTT) by MTT colorimetric analysis. The best irradiating condition was determined, the effect and both virtues and defects of the laser were compared with those of electropuncture. The results show (1) LTT was enhanced in the group of laser irradiating point, but LTT was not enhanced in non-point (t' test, P < 0.01). (2) Lower power -- 2 mW or 5 mW of irradiating for 15 - 20 min, was better; 10 mW or 20 mW of irradiating for 10 - 15 min was suitable. Prolonged irradiating time did not enhance the immune function of the rats. On the contrary, immune function was inhibited. (3) A 7-day period of irradiating was best (once a day, 10 mW for 10 min). Enhanced LTT was not seen when irradiation days were added (SNK, P > 0.05). (4) Laser irradiation point and electropuncture were compared with vehicle control, LTT in the former two groups was enhanced significantly (ANOVA, P < 0.01), and laser irradiating point and electropuncture had the same effect (SNK, P > 0.05). The data suggest that laser irradiating point was able to enhance cell immunity and the enhancement of LTT had a point specific characteristic. The best condition of laser irradiating point was 2 mW for 15 - 20 min, and 10 mW or 20 mW for 10 - 15 min. The best period was 7-day irradiation. The results show laser irradiating the point may activate the main and collateral channels system, then modify the immune function of the body. Our observations provide experimental evidence for proper clinical application of laser irradiating points. The paper theoretically discusses and analyzes the experiment results in detail.

  1. Interaction of high intensity laser with non-uniform clusters and enhanced X-ray emission

    SciTech Connect

    Liu, C. S.; Tripathi, V. K.; Kumar, Manoj

    2014-10-15

    Laser irradiated clusters with non-uniform density variation are shown to broaden surface plasmon resonance very significantly. As the clusters get heated and expand hydro-dynamically, the Bremsstrahlung X-ray emission yield passes through a maximum in time. The maximum yield decreases with increase in non-uniformity in the electron density inside the clusters. At higher laser intensity, the nonlinearity in laser cluster interaction may arise even prior to electron heating, via the relativistic mass variation and the nonlinear restoration force on electrons. For clusters with radius less than one tenth of the laser wavelength, the restoration force nonlinearity dominates.

  2. Fast Electron Generation in Cones with Ultra-Intense Laser Pulses

    SciTech Connect

    Mackinnon, A; VanWoerkom, L; Akli, K; Bartal, T; Beg, F; Chawla, S; Chen, C; Chowdhury, E; Freeman, R; Hey, D; Key, M; King, J; Link, A; MacPhee, A; Offermann, D; Ovchinnikov, V; Patel, P; Schumacher, D; Stephens, R; Tsui, Y; Ma, T

    2007-12-07

    Experimental results from copper cones irradiated with ultra-intense laser light are presented. Spatial images and total yields of Cu K{sub {alpha}} fluorescence were measured as a function of the laser focusing properties. The fluorescence emission extends into the cone approximately 300 {micro}m from the cone tip and cannot be explained by ray tracing including cone wall absorption. In addition the total fluorescence yield from cones is an order of magnitude higher than for equivalent mass foil targets. Indications are that the physics of the laser cone interaction is dominated by preplasma created from the long duration, low energy pre-pulse from the laser.

  3. Reply to 'Comment on 'Photoionization of helium atoms irradiated with intense vacuum ultraviolet free-electron laser light. Part I. Experimental study of multiphoton and single-photon processes''

    SciTech Connect

    Laarmann, T.; Guertler, P.; Laasch, W.; Schulz, J.; Wabnitz, H.; Moeller, T.; Castro, A. R. B. de

    2006-09-15

    We do not agree with the conclusion of the Comment by Charalambidis et al. questioning our observation of two-photon ionization of helium by intense radiation with 13 eV photons from a vuv free-electron laser. Two-photon ionization is clearly established by the detection of low-energy photoelectrons at {approx}1.7 eV, which agrees very well with the expected energy for a two-photon ionization process.

  4. Energetic electron propagation in solid targets driven by the intense electric fields of femtosecond laser pulses

    SciTech Connect

    Seely, J. F.; Szabo, C. I.; Audebert, P.; Brambrink, E.

    2011-06-15

    An analytical model is used to interpret experimental data on the propagation of energetic electrons perpendicular to and parallel to the propagation direction of intense femtosecond laser pulses that are incident on solid targets. The pulses with {approx_equal}10{sup 20} W/cm{sup 2} intensity are incident normal onto a gadolinium or tungsten wire embedded in an aluminum substrate, and MeV electrons generated in the focal spot propagate along the laser direction into the irradiated wire. Electrons also propagate laterally from the focal spot through the aluminum substrate and into a dysprosium or hafnium spectator wire at a distance up to 1 mm from the irradiated wire. The ratio of the K shell emission from the spectator and irradiated wires is a measure of the numbers and energies of the MeV electrons propagating parallel to and perpendicular to the intense oscillating electric field of the laser pulse. It is found that the angular distribution of electrons from the focal spot is highly non-isotropic, and approximately twice as many electrons are driven by the electric field toward the spectator wire as into the irradiated wire. This quantitative result is consistent with the qualitative experimental observation that the oscillating electric field of an intense femtosecond laser pulse, when interacting with a heavy metal target, preferentially drives energetic electrons in the electric field direction as compared to perpendicular to the field.

  5. The response of heat-shield materials to intense laser radiation

    NASA Technical Reports Server (NTRS)

    Lundell, J. H.; Dickey, R. R.

    1978-01-01

    Experimental results for the response of ATJ graphite, Carbitex 100, and carbon phenolic to intense continuous-wave laser radiation are presented. Both penetration and mass-loss test techniques are used and compared. The results are also compared with a simple ablation theory applicable to laser irradiation. Reasons for the disparity between experiment and theory, and applicability of the results to other heating situations, such as planetary entry, are discussed.

  6. Method for mounting laser fusion targets for irradiation

    DOEpatents

    Fries, R. Jay; Farnum, Eugene H.; McCall, Gene H.

    1977-07-26

    Methods for preparing laser fusion targets of the ball-and-disk type are disclosed. Such targets are suitable for irradiation with one or two laser beams to produce the requisite uniform compression of the fuel material.

  7. Charged-particle acceleration through laser irradiation of thin foils at Prague Asterix Laser System

    NASA Astrophysics Data System (ADS)

    Torrisi, Lorenzo; Cutroneo, Maria; Cavallaro, Salvatore; Musumeci, Paolo; Calcagno, Lucia; Wolowski, Jerzy; Rosinski, Marcin; Zaras-Szydlowska, Agnieszka; Ullschmied, Jiri; Krousky, Eduard; Pfeifer, Miroslav; Skala, Jiri; Velyhan, Andreiy

    2014-05-01

    Thin foils, 0.5-50 μm in thickness, have been irradiated in vacuum at Prague Asterix Laser System in Prague using 1015-16 W cm-2 laser intensity, 1315 nm wavelength, 300 ps pulse duration and different focal positions. Produced plasmas from metals and polymers films have been monitored in the forward and backward directions. Ion and electron accelerations have been investigated by using Thomson parabola spectrometer, x-ray streak camera, ion collectors and SiC semiconductor detectors, the latter employed in time-of-flight configuration. Ion acceleration up to about 3 MeV per charge state was measured in the forward direction. Ion and electron emissions were detected at different angles as a function of the irradiation conditions.

  8. Laser intensity modulation by nonabsorbing defects

    SciTech Connect

    Feit, M.D.; Rubenchik, A.M.

    1997-01-01

    Nonabsorbing bulk defects can initiate laser damage in transparent materials. Defects such as voids, microcracks and localized stress concentrations can serve as positive or negative lenses for the incident laser light. The resulting interference pattern between refracted and diffracted light can result in intensity increases on the order of a factor of 2 some distance away from a typical negative microlens, and even larger for a positive microlens. Thus, the initial damage site can be physically removed from the defect which initiates damage. The parameter that determines the strength of such lensing is (Ka){sup 2}{Delta}{epsilon}, where the wavenumber K is 2{pi}/{lambda} linear size of the defect and AF, is the difference in dielectric coefficient between matrix and scatterer. Thus, even a small change in refractive index results in a significant effect for a defect large compared to a wavelength. Geometry is also important. Three dimensional (eg. voids) as well as linear and planar (eg. cracks) microlenses can all have strong effects. The present paper evaluates the intensification due to spherical voids and high refractive index inclusions. We wish to particularly draw attention to the very large intensification that can occur at inclusions.

  9. Laser intensity modulation by nonabsorbing defects

    SciTech Connect

    Feit, M.D., Rubenchik, A.M.

    1996-11-20

    Nonabsorbing defects can lead to laser damage. Defects such as voids, microcracks, and localized stressed concentrations, even if they differ from the surrounding medium only by refractive index, can serve as positive or negative lenses for the incident laser light. The resulting interference pattern between refracted and diffracted light can result in intensity increases on the order of a factor of 2 some distance away from a typical negative microlens, and even larger for a positive microlens. Thus, the initial damage site can be physically removed from the defect which initiates damage. The parameter that determines the strength of such lensing is (Ka){sup 2}{Delta}{epsilon}, where the wavenumber K is 2{pi}/{lambda}, 2a is the linear size of the defect, and {Delta}{epsilon} is the difference in dielectric coefficient between matrix and scatterer. Thus, even a small change in refractive index results in a significant effect for a defect large compared to a wavelength. Geometry is also important. Three dimensional (e.g. voids) as well as linear and planar (e.g. cracks) microlenses can all have strong effects. This paper evaluates intensification due to spherical voids and high refractive index inclusions.

  10. Low intensity laser therapy: the clinical approach

    NASA Astrophysics Data System (ADS)

    Kahn, Fred

    2006-02-01

    Recently, there has been significant improvement in the process of research and application of Low Intensity Laser Therapy (LILT). Despite this positive direction, a wide discrepancy between the research component and clinical understanding of the technology remains. In our efforts to achieve better clinical results and more fully comprehend the mechanisms of interaction between light and cells, further studies are required. The clinical results presented in this paper are extrapolated from a wide range of musculoskeletal problems including degenerative osteoarthritis, repetitive motion injuries, sports injuries, etc. The paper includes three separate clinical studies comprising 151, 286 and 576 consecutive patient discharges at our clinic. Each patient studied received a specific course of treatment that was designed for that individual and was modified on a continuing basis as the healing process advanced. On each visit, clinical status correlation with the duration, dosage and other parameters was carried out. The essentials of the treatment consisted of a three stage approach. This involved a photon stream emanating from a number of specified gallium-aluminum-arsenide diodes; stage one, red light array, stage two consisting of an array of infrared diodes and stage three consisting of the application of an infrared laser diode probe. On average, each of these groups required less than 10 treatments per patient and resulted in a significant improvement / cure rate greater than 90% in all conditions treated. This report clearly demonstrates the benefits of LILT, indicating that it should be more widely adapted in all medical therapeutic settings.

  11. Laser irradiation of carbon nanotube films: Effects and heat dissipation probed by Raman spectroscopy

    SciTech Connect

    Mialichi, J. R.; Brasil, M. J. S. P.; Iikawa, F.; Verissimo, C.; Moshkalev, S. A.

    2013-07-14

    We investigate the thermal properties of thin films formed by single- and multi-walled carbon nanotubes submitted to laser irradiation using Raman scattering as a probe of both the tube morphology and the local temperature. The nanotubes were submitted to heating/cooling cycles attaining high laser intensities ({approx}1.4 MW/cm{sup 2}) under vacuum and in the presence of an atmosphere, with and without oxygen. We investigate the heat diffusion of the irradiated nanotubes to their surroundings and the effect of laser annealing on their properties. The presence of oxygen during laser irradiation gives rise to an irreversible increase of the Raman efficiency of the carbon nanotubes and to a remarkable increase of the thermal conductivity of multi-walled films. The second effect can be applied to design thermal conductive channels in devices based on carbon nanotube films using laser beams.

  12. Time-resolved measurement of x-ray heating in plastic foils irradiated by intense soft-x-ray pulses

    SciTech Connect

    Edwards, J.; Dunne, M.; Riley, D.; Taylor, R.; Willi, O. ); Rose, S.J. )

    1991-12-30

    Intense, soft-x-ray pulses, generated from separate laser-irradiated converters, were used to irradiate plane plastic foils. The x-ray heating was investigated by measuring the temperature histories of chlorinated tracer layers buried at different depths in the targets. The temperature diagonistic was a time-resolved extreme-UV absorption spectroscopy technique using chlorine {ital L}-shell transitions. The temporal temperature profiles were reasonably well reproduced by radiation-hydrocode simulations.

  13. Laser Ion Acceleration from the Interaction of Ultra-Intense laser Pulse with thi foils

    SciTech Connect

    Allen, M

    2004-03-12

    The discovery that ultra-intense laser pulses (I > 10{sup 18} W/cm{sup 2}) can produce short pulse, high energy proton beams has renewed interest in the fundamental mechanisms that govern particle acceleration from laser-solid interactions. Experiments have shown that protons present as hydrocarbon contaminants on laser targets can be accelerated up to energies > 50 MeV. Different theoretical models that explain the observed results have been proposed. One model describes a front-surface acceleration mechanism based on the ponderomotive potential of the laser pulse. At high intensities (I > 10{sup 18} W/cm{sup 2}), the quiver energy of an electron oscillating in the electric field of the laser pulse exceeds the electron rest mass, requiring the consideration of relativistic effects. The relativistically correct ponderomotive potential is given by U{sub p} = ([1 + I{lambda}{sup 2}/1.3 x 10{sup 18}]{sup 1/2} - 1) m{sub o}c{sup 2}, where I{lambda}{sup 2} is the irradiance in W{micro}m{sup 2}/cm{sup 2} and m{sub o}c{sup 2} is the electron rest mass.At laser irradiance of I{lambda}{sup 2} {approx} 10{sup 20} W{micro}m{sup 2}/cm{sup 2}, the ponderomotive potential can be of order several MeV. A few recent experiments--discussed in Chapter 3 of this thesis--consider this ponderomotive potential sufficiently strong to accelerate protons from the front surface of the target to energies up to tens of MeV. Another model, known as Target Normal Sheath Acceleration (TNSA), describes the mechanism as an electrostatic sheath on the back surface of the laser target. According to the TNSA model, relativistic hot electrons created at the laser-solid interaction penetrate the foil where a few escape to infinity. The remaining hot electrons are retained by the target potential and establish an electrostatic sheath on the back surface of the target.

  14. Femtosecond laser irradiation of metallic surfaces: effects of laser parameters on superhydrophobicity

    NASA Astrophysics Data System (ADS)

    Moradi, Sona; Kamal, Saeid; Englezos, Peter; Hatzikiriakos, Savvas G.

    2013-10-01

    This work studies in detail the effect of femtosecond laser irradiation process parameters (fluence and scanning speed) on the hydrophobicity of the resulting micro/nano-patterned morphologies on stainless steel. Depending on the laser parameters, four distinctly different nano-patterns were produced, namely nano-rippled, parabolic-pillared, elongated sinusoidal-pillared and triple roughness nano-structures. All of the produced structures were classified according to a newly defined parameter, the laser intensity factor (LIF); by increasing the LIF, the ablation rate and periodicity of the asperities increase. In order to decrease the surface energy, all of the surfaces were coated with a fluoroalkylsilane agent. Analysis of the wettability revealed enhanced superhydrophobicity for most of these structures, particularly those possessing the triple roughness pattern that also exhibited low contact angle hysteresis. The high permanent superhydrophobicity of this pattern is due to the special micro/nano-structure of the surface that facilitates the Cassie-Baxter state.

  15. Effect of laser irradiation of nanoparticles in aqueous uranium salt solutions on nuclide activity

    SciTech Connect

    Simakin, Aleksandr V; Shafeev, Georgii A

    2011-07-31

    This paper presents an experimental study of the effect of laser irradiation of aqueous uranyl chloride solutions containing gold nanoparticles on the activity of the uranium series radionuclides {sup 234}Th, {sup 234m}Pa, and {sup 235}U. The solutions were exposed to femtosecond Ti:sapphire laser pulses and to the second or third harmonic of a Nd:YAG laser (150-ps pulses) at a peak intensity in the medium of {approx}10{sup 12} W cm{sup -2}. The activities of the radionuclides in the irradiated solutions were shown to differ markedly from their equilibrium values. The sign of the deviation depends on the laser wavelength. The measured activity deviations can be interpreted as evidence that laser exposure of nanoparticles accelerates the alpha and beta decays of the radionuclides. The observed effects are accounted for in terms of a mechanism that involves resonant enhancement of optical waves by metallic nanoparticles. (interaction of laser radiation with matter)

  16. The dynamics of Al/Pt reactive multilayer ignition via pulsed-laser irradiation

    SciTech Connect

    Murphy, Ryan D.; Reeves, Robert V.; Yarrington, Cole D.; Adams, David P.

    2015-12-07

    Reactive multilayers consisting of alternating layers of Al and Pt were irradiated by single laser pulses ranging from 100 μs to 100 ms in duration, resulting in the initiation of rapid, self-propagating reactions. The threshold intensities for ignition vary with the focused laser beam diameter, bilayer thickness, and pulse length and are affected by solid state reactions and conduction of heat away from the irradiated regions. High-speed photography was used to observe ignition dynamics during irradiation and elucidate the effects of heat transfer into a multilayer foil. For an increasing laser pulse length, the ignition process transitioned from a more uniform to a less uniform temperature profile within the laser-heated zone. A more uniform temperature profile is attributed to rapid heating rates and heat localization for shorter laser pulses, and a less uniform temperature profile is due to slower heating of reactants and conduction during irradiation by longer laser pulses. Finite element simulations of laser heating using measured threshold intensities indicate that micron-scale ignition of Al/Pt occurs at low temperatures, below the melting point of both reactants.

  17. Isochoric heating of reduced mass targets by ultra-intense laser produced relativistic electrons

    SciTech Connect

    Neumayer, P; Lee, H J; Offerman, D; Shipton, E; Kemp, A; Kritcher, A L; Doppner, T; Back, C A; Glenzer, S H

    2009-02-04

    We present measurements of the chlorine K-alpha emission from reduced mass targets, irradiated with ultra-high intensity laser pulses. Chlorinated plastic targets with diameters down to 50 micrometers and mass of a few 10{sup -8} g were irradiated with up to 7 J of laser energy focused to intensities of several 10{sup 19} W/cm{sup 2}. The conversion of laser energy to K-alpha radiation is measured, as well as high resolution spectra that allow observation of line shifts, indicating isochoric heating of the target up to 18 eV. A zero-dimensional 2-temperature equilibration model, combined with electron impact K-shell ionization and post processed spectra from collisional radiative calculations reproduces the observed K-alpha yields and line shifts, and shows the importance of target expansion due to the hot electron pressure.

  18. Color changes in CR-39 nuclear track detector by gamma and laser irradiation

    NASA Astrophysics Data System (ADS)

    Nouh, S. A.; Said, A. F.; Atta, M. R.; El-Melleegy, W. M.; El-Meniawy, S.

    2006-07-01

    A study of the effect of gamma and laser irradiation on the color changes of polyallyl diglycol (CR-39) solid-state nuclear track detector was performed. CR-39 detector samples were classified into two main groups. The first group was irradiated with gamma doses at levels between 20 and 300 kGy, whereas the second group was exposed to infrared laser radiation with energy fluences at levels between 0.71 and 8.53 J/cm(2) . The transmission of these samples in the wavelength range 300-2500 nm, as well as any color changes, was studied. Using the transmission data, both the tristimulus and the coordinate values of the Commission Internationale de l'Eclairage (CIE) LAB were calculated. Also, the color differences between the non-irradiated samples and those irradiated with different gamma or laser doses were calculated. The results indicate that the CR-39 detector acquires color changes under gamma or laser irradiation, but it has more response to color changes by gamma irradiation. In addition, structural property studies using infrared spectroscopy were performed. The results indicate that the irradiation of a CR-39 detector with gamma or laser radiations causes the cleavage of the carbonate linkage that can be attributed to the H abstraction from the backbone of the polymer, associated with the formation of CO 2 and OH with varying intensities.

  19. Effects of low-intensity laser therapy over mini-implants success rate in pigs.

    PubMed

    Garcez, Aguinaldo S; Suzuki, Selly Sayuri; Martinez, Elisabeth Ferreira; Iemini, Mylene Garcez; Suzuki, Hideo

    2015-02-01

    The success rate of miniscrews when used as temporary orthodontic anchorage is relatively high, but some factors could affect its clinical success such as inflammation around the miniscrew. Low-intensity laser therapy has been widely used for biostimulation of tissue and wound healing specially for its anti-inflammatory effects. The purpose of this study was to evaluate the effect of low-intensity laser therapy over the miniscrew success rate. Five Landrace's pigs received 50 miniscrews on the buccal side of the mandible and on the palate of the maxilla. All the miniscrews were immediately loaded with 250 gf. The laser group were irradiated with a 780-nm diode laser with 70 mWs for 1 min (dose = 34 J/cm(2)); the contralateral side was used as the control group. The miniscrews were photographed and analyzed clinically every week to determine their stability and presence of local inflammation. After 3 weeks, histological analysis and fluorescent microscopy were performed to compare the laser and the control side. Clinical results showed a success rate of 60% for the control group and 80% for the laser-treated group. The histological analysis and fluorescent microscopy demonstrated that the laser group had less inflammatory cells than the control group and the bone neoformation around the miniscrew was more intense. Low-intensity laser therapy increased the success rate of orthodontic miniscrews, probably due to anti-inflammatory effect and bone stimulation. PMID:23929562

  20. Laser annealing of neutron irradiated boron-10 isotope doped diamond

    SciTech Connect

    Jagannadham, K.; Butler, J. E.

    2011-01-01

    10B isotope doped p-type diamond epilayer grown by chemical vapor deposition on (110) oriented type IIa diamond single crystal substrate was subjected to neutron transmutation at a fluence of 2.4 9 1020 thermal and 2.4 9 1020 fast neutrons. After neutron irradiation, the epilayer and the diamond substrate were laser annealed using Nd YAG laser irradiation with wave length, 266 nm and energy, 150 mJ per pulse. The neutron irradiated diamond epilayer and the substrate were characterized before and after laser annealing using different techniques. The characterization techniques include optical microscopy, secondary ion mass spectrometry, X-ray diffraction, Raman, photoluminescence and Fourier Transform Infrared spectroscopy, and electrical sheet conductance measurement. The results indicate that the structure of the irradiation induced amorphous epilayer changes to disordered graphite upon laser annealing. The irradiated substrate retains the (110) crystalline structure with neutron irradiation induced defects.

  1. Intensity clamping in the filament of femtosecond laser radiation

    SciTech Connect

    Kandidov, V P; Fedorov, V Yu; Tverskoi, O V; Kosareva, O G; Chin, S L

    2011-04-30

    We have studied numerically the evolution of the light field intensity and induced refractive index of a medium upon filamentation of femtosecond laser radiation in air. It is shown that the intensity clamping results from the dynamic balance of optical powers of nonlinear lenses, induced by radiation due to the Kerr nonlinearity of air, and laser plasma produced during photoionisation. We have found the relation between the peak values of the light field intensity and the electron density in laser-produced plasma, as well as the transverse sizes of the filament and the plasma channel. (effects of laser radiation on matter)

  2. Nonlinear physics of laser-irradiated microclusters

    SciTech Connect

    Breizman, Boris N.; Arefiev, Alexey V.; Fomyts'kyi, Mykhailo V.

    2005-05-15

    A nonlinear theory has been developed to describe electron response and ion acceleration in dense clusters that are smaller in size than the laser wavelength. This work is motivated by high-intensity laser-cluster interaction experiments. The theory reveals that the breakdown of quasineutrality affects the cluster dynamics in a dramatic way: the laser can create a positively charged ion shell that expands due to its own space charge much faster than the central part of the cluster. The developed theory also shows a trend for the electron population to have a two-component distribution function: a cold core that responds to the laser field coherently and a hot halo that undergoes stochastic heating. The hot electrons expand together with the equal number of ions that are accelerated to supersonic velocities in a double layer at the cluster edge. This mechanism produces fast ions with energies much greater than the ponderomotive potential and it suggests that larger deuterium clusters can significantly enhance the neutron yield in future experiments.

  3. High-intensity laser heating in liquids: Multiphoton absorption

    SciTech Connect

    Longtin, J.P.; Tien, C.L.

    1995-12-31

    At high laser intensities, otherwise transparent liquids can absorb strongly by the mechanism of multiphoton absorption, resulting in absorption and heating several orders of magnitude greater than classical, low-intensity mechanisms. The use of multiphoton absorption provides a new mechanism for strong, controlled energy deposition in liquids without bulk plasma formation, shock waves, liquid ejection, etc., which is of interest for many laser-liquid applications, including laser desorption of liquid films, laser particle removal, and laser water removal from microdevices. This work develops a microscopically based model of the heating during multiphoton absorption in liquids. The dependence on pulse duration, intensity, wavelength, repetition rate, and liquid properties is discussed. Pure water exposed to 266 nm laser radiation is investigated, and a novel heating mechanism for water is proposed that uses multiple-wavelength laser pulses.

  4. Large aperture adaptive optics for intense lasers

    NASA Astrophysics Data System (ADS)

    Deneuville, François; Ropert, Laurent; Sauvageot, Paul; Theis, Sébastien

    2015-05-01

    ISP SYSTEM has developed a range of large aperture electro-mechanical deformable mirrors (DM) suitable for ultra short pulsed intense lasers. The design of the MD-AME deformable mirror is based on force application on numerous locations thanks to electromechanical actuators driven by stepper motors. DM design and assembly method have been adapted to large aperture beams and the performances were evaluated on a first application for a beam with a diameter of 250mm at 45° angle of incidence. A Strehl ratio above 0.9 was reached for this application. Simulations were correlated with measurements on optical bench and the design has been validated by calculation for very large aperture (up to Ø550mm). Optical aberrations up to Zernike order 5 can be corrected with a very low residual error as for actual MD-AME mirror. Amplitude can reach up to several hundreds of μm for low order corrections. Hysteresis is lower than 0.1% and linearity better than 99%. Contrary to piezo-electric actuators, the μ-AME actuators avoid print-through effects and they permit to keep the mirror shape stable even unpowered, providing a high resistance to electro-magnetic pulses. The MD-AME mirrors can be adapted to circular, square or elliptical beams and they are compatible with all dielectric or metallic coatings.

  5. Suppressed tuberculin reaction in guinea pigs following laser irradiation

    SciTech Connect

    Inoue, K.; Nishioka, J.; Hukuda, S.

    1989-01-01

    Tuberculin reactions were tested at the bilateral sites of the backs of sensitized guinea pigs. Laser irradiation at an energy fluence of 3.6 J at one site of reaction suppressed the reaction not only at the irradiated site but also at the contralateral nonirradiated site. These phenomena were observed when mononuclear cells were dominant in the perivascular cellular infiltration. The results indicate that local irradiation with a low-power laser has systemic inhibitory effects on delayed hypersensitivity reactions.

  6. Directed fast electron beams in ultraintense picosecond laser irradiated solid targets

    SciTech Connect

    Ge, X. L.; Lin, X. X.; Yuan, X. H. E-mail: ytli@iphy.ac.cn; Sheng, Z. M.; Carroll, D. C.; Neely, D.; Gray, R. J.; Tresca, O.; McKenna, P.; Yu, T. P.; Chen, M.; Liu, F.; Zhuo, H. B.; Zielbauer, B.; and others

    2015-08-31

    We report on fast electron transport and emission patterns from solid targets irradiated by s-polarized, relativistically intense, picosecond laser pulses. A beam of multi-MeV electrons is found to be transported along the target surface in the laser polarization direction. The spatial-intensity and energy distributions of this beam are compared with the beam produced along the laser propagation axis. It is shown that even for peak laser intensities an order of magnitude higher than the relativistic threshold, laser polarization still plays an important role in electron energy transport. Results from 3D particle-in-cell simulations confirm the findings. The characterization of directional beam emission is important for applications requiring efficient energy transfer, including secondary photon and ion source development.

  7. Propagation of intense short-pulse laser in homogeneous near-critical density plasmas

    NASA Astrophysics Data System (ADS)

    Habara, H.; Nakaguchi, S.; Uematsu, Y.; Baton, S. D.; Chen, S. N.; Fuchs, J.; Iwawaki, T.; MacDonald, M.; Nazarov, W.; Rousseaux, C.; Tanaka, K. A.

    2016-05-01

    Ultra intense laser light propagation in a homogeneous overdense plasma was investigated using a plastic foam target filling a polyimide tube. Laser propagation into overdense plasma was measured via Doppler red shift of the reflected laser light from the moving plasma at 0.3-0.4 of speed of light. We also observed strongly collimated electron beam possibly caused by the magnetic field surrounding the plasma channel, and high energy X-rays emitted via synchrotron radiation by the oscillating electrons inside the channel. These features imply that UIL propagates inside the overdense plasma as predicted in PIC calculation, and are very important for direct irradiation scheme of fast ignition.

  8. [The state of autonomic homeostasis during the use of a low-intensity helium-neon laser as a component of combined anesthesia].

    PubMed

    Avrutskiĭ, M Ia; Musikhin, L V; Finkel'shteĭn, I E; Katkovskiĭ, D G; Guseĭnov, T Iu

    1992-01-01

    The effect of intravenous blood irradiation, using helium-neon laser, on vegetative homeostasis during surgery was studied. It has been established that the introduction of low-intensity laser blood irradiation into a complex of anesthesiologic procedures ensures a more effective protection of patients from the surgical stress. PMID:1524243

  9. On-line measurement of wavefront aberration on optics caused by intense lasers

    NASA Astrophysics Data System (ADS)

    Xu, Zuodong; Liu, Fuhua; Jiang, Chang; Wang, Fei; Shao, Bibo; Ji, Yunfeng

    2015-05-01

    It is presented that the thermally induced transmitted wavefront aberration of a high-reflectivity sampling mirror was detected on line using a Shack-Hartmann wavefront sensor (SHWS) in the beam quality measurement of an intense laser. As a result of heat absorption in the sampling mirror with active aperture of 120 mm, thermally induced wavefront aberration emerged when the mirror was exposed to high laser intensity of several kilowatts per centimeter square. Time-dependent wavefront aberration curves were acquired, and the transmitted wavefronts were reconstructed based on Zernike mode reconstruction theory. The experimental results indicate that the magnitude of the dynamic transmitted wavefront aberration increases gradually with the growing heat deposit during laser irradiation. The maximum of wavefront aberration observed after irradiation for 5 seconds reaches 0.11 μm of root-mean-square value. After further analysis, the experimental results of dynamic aberration can be applied in modifications for the measurement results of intense laser beam quality or tests for the thermal stability of optics used in the intense laser systems.

  10. Application of a transmission crystal x-ray spectrometer to moderate-intensity laser driven sources

    SciTech Connect

    Mao, J. Y.; Chen, L. M.; Zhang, L.; Sun, Y. Q.; Lin, X. X.; Hudson, L. T.; Seely, J. F.; Zhang, J.

    2012-04-15

    In the pursuit of novel, laser-produced x-ray sources for medical imaging applications, appropriate instrumental diagnostics need to be developed concurrently. A type of transmission crystal spectroscopy has previously been demonstrated as a survey tool for sources produced by high-power and high-energy lasers. The present work demonstrates the extension of this method into the study of medium-intensity laser driven hard x-ray sources with a design that preserves resolving power while maintaining high sensitivity. Specifically, spectroscopic measurements of characteristic K{alpha} and K{beta} emissions were studied from Mo targets irradiated by a 100 fs, 200 mJ, Ti: sapphire laser with intensity of 10{sup 17} W/cm{sup 2} to 10{sup 18} W/cm{sup 2} per shot. Using a transmission curved crystal spectrometer and off-Rowland circle imaging, resolving powers (E/{Delta}E) of around 300 for Mo K{alpha}{sub 2} at 17.37 keV were obtained with an end-to-end spectrometer efficiency of (1.13 {+-} 0.10) x 10{sup -5}. This sensitivity is sufficient for registering x-ray lines with high signal to background from targets following irradiation by a single laser pulse, demonstrating the utility of this method in the study of the development of medium-intensity laser driven x-ray sources.

  11. Control of light backscattering in blood during intravenous laser irradiation

    NASA Astrophysics Data System (ADS)

    Melnik, Ivan S.; Popov, V. D.; Rusina, Tatyana V.; Dets, Sergiy M.

    1997-02-01

    One of the most important problems in modern laser medicine is the determination of system response on laser treatment. Reaction of living system is significant during many kinds of laser procedures like surgery, therapy and biostimulation. Our study was aimed to optimize laser exposure using feed-back fiber system for intravenous laser irradiation of blood (ILIB). This system consisted of helium-neon laser (633 nm, 5 mW) with coupled fiber unit, photodetector and PC interface. Photodetector signals produced due to light backscattering were storaged and processed during all blood irradiation procedure. Significant time-dependent variations were observed within 9-15 min after beginning of treatment procedure and were correlated with number of trials, stage and character of disease. The designed feed-back system allows us to register a human blood response on laser irradiation to achieve better cure effect.

  12. Effect of the laser intensity profile on the shock non-uniformity in a directly driven spherical target

    NASA Astrophysics Data System (ADS)

    Temporal, Mauro; Canaud, Benoit; Garbett, Warren J.; Ramis, Rafael

    2015-10-01

    > An axially symmetric laser beam configuration irradiating a spherical capsule has been considered in the context of inertial confinement fusion (ICF). The laser beams are located at co-latitudes 49° and 131° and mimic the quad positions in the second cone of the Laser Mégajoule Facility. The capsule is directly irradiated by the laser beams whose energy deposition generates a nearly spherical shock wave. Two-dimensional hydrodynamic numerical simulations have been performed to analyse the non-uniformity of the shock wavefront launched inward throughout the target. Different laser intensity profiles, calculated by the illumination model, have been tested. The performance, in terms of shock non-uniformity, has been compared, and it is found that with an appropriate choice of the laser intensity profile it is possible to control the shock non-uniformity at early times.

  13. Reshaping of intense laser pulse with a capillary

    SciTech Connect

    Cao Lihua; Yu Wei; Yu, M. Y.; Wang Xin; Gu Yuqiu; He, X. T.

    2009-09-15

    The reshaping of intense laser pulse by vacuum capillary is studied by particle-in-cell simulation. It is shown that as an intense laser pulse propagates from free space into a capillary, its profile is reshaped due to laser-plasma interaction near the entrance of capillary. As a result, the free-space mode is self-consistently converted into a capillary mode. Only the relatively low-intensity periphery of the reshaped pulse interacts with the capillary-wall plasma, so that the high-intensity center of the pulse can propagate in the narrow vacuum channel over a distance much larger than the Rayleigh length. The mechanism is then applied to reshape a radially imperfect laser pulse having two wings around the center spot. Most of the output light energy is concentrated in the center spot, and the wings are almost completely removed. That is, the quality of the laser pulse can be greatly improved by a capillary.

  14. Effect of green laser irradiation on hydrogen production

    NASA Astrophysics Data System (ADS)

    Bidin, Noriah; Razak, Siti Noraiza A.; Radiana Azni, Siti; Nguroho, Waskito; Mohsin, Ali Kamel; Abdullah, Mundzir; Krishnan, Ganesan; Bakhtiar, Hazri

    2014-06-01

    The effect of green laser irradiation on hydrogen production via water electrolysis was investigated. Diode pumped solid-state laser operating in second harmonic generation was employed as a source of irradiation. The hydrogen production system was also irradiated by a conventional light, a halogen source, for comparison. The best catalyst was identified by mixing distilled water with two types of salt: NaCl and Na2SO4. Optimization of hydrogen production from water electrolysis was realized by using NaCl and green laser irradiation. The power of green laser irradiation and the concentration of NaCl in water contribute to hydrogen production. The hydrogen yield also depends on the distance and direction of the green beam to the electrode.

  15. Multigraphene growth on lead-pencil drawn sliver halide print paper irradiated by scanning femtosecond laser

    NASA Astrophysics Data System (ADS)

    Kaneko, Satoru; Shimizu, Yoshitada; Rachi, Takeshi; Kato, Chihiro; Tanaka, Satomi; Naganuma, Yasuhiro; Katakura, Toru; Satoh, Kazuo; Ushiyama, Mikio; Konuma, Seiji; Itou, Yuko; Takikawa, Hirofumi; Tan, Goon; Matsuda, Akifumi; Yoshimoto, Mamoru

    2016-01-01

    Drawings were made on various types of paper using lead pencils of grades from 4H through 10B. Raman spectroscopy verified both G and D peaks on all the drawings on PC print paper, PC photopaper, kent paper, and paper for silver halide print. After irradiation with a scanning femtosecond laser, silver halide paper drawn on with a 10B lead pencil maintained its surface flatness compared with the other types of paper. Raman spectroscopy on silver print paper showed a high-intensity G peak and a low-intensity D peak. After irradiating the scanning femtosecond laser on silver halide paper drawn on with a 10B lead pencil, Raman spectroscopy showed a high-intensity G peak and less intense of D peak together with a 2D peak around 2,700 cm-1 corresponding to the existence of multigraphene.

  16. Measurements of Intense Femtosecond Laser Pulse Propagation in Air

    NASA Astrophysics Data System (ADS)

    Ting, Antonio

    2004-11-01

    Intense femtosecond pulses generated from chirped pulse amplification (CPA) lasers can deliver laser powers many times above the critical power for self-focusing in air. Catastrophic collapse of the laser pulse is usually prevented by the defocusing of the plasma column formed when the laser intensity gets above the threshold for multiphoton ionization. The resultant laser/plasma filament can extend many meters as the laser pulse propagates in the atmosphere. We have carried out a series of experiments both for understanding the formation mechanisms of the filaments and the nonlinear effects such as white light and harmonics generation associated with them. Many applications of these filaments such as remote atmospheric breakdown, laser induced electrical discharge and femtosecond laser material interactions require direct measurements of their characteristics. Direct measurements of these filaments had been difficult because the high laser intensity ( ˜10^13 W/cm^2) can damage practically any optical diagnostics. A novel technique was invented to obtain the first absolute measurements of laser energy, transverse profile, fluence and spectral content of the filaments. We are investigating a ``remote atmospheric breakdown'' concept of remotely sensing chemical and biological compounds. A short intense laser pulse can be generated at a remote position by using the group velocity dispersion (GVD) of the air to compress an initially long, frequency negatively chirped laser pulse to generate the air breakdown and filaments. We have observed that nonlinear contributions to the laser spectrum through self-phase modulation can lead to modification of the linear GVD compression. We have also observed the generation of ultraviolet (UV) radiations from these filaments in air and the induced fluorescence by the UV radiation of a surrogate biological agent. These and other results such as laser induced electrical discharges will be presented.

  17. Morphological analysis of the retrofilled apical dentin surfaces irradiated with CO2 laser

    NASA Astrophysics Data System (ADS)

    Aun, Carlos E.; Lage-Marques, Jose L.; Gavini, Giulio; Clasen, Naya F.; Matsumoto, Koukichi

    1998-04-01

    Countless researches conducted in these last years have compared the sealing capacity of various materials for retrofillings. Besides, the association of laser irradiation to traditional procedures inquires to increase the success of this kind of treatment. The purpose of this study was to evaluate the morphological changes on dentin surface and the junction between retrofilling material and apical cavity, with different materials irradiated or not with CO2 laser, in scanning electron microscopy. The following materials were used: Group A yields Super EBA; group B yields Super EBA and CO2 laser irradiation (Luxar System); group C yields Glass Ionomer Cement; group D yields Glass Ionomer Cement and CO2 laser. In groups B and D the power set was 2 watts, 20 msec, with a CT3105 ceramic point, and the power density for the CO2 laser application was 397,93 w/cm2. The morphological analysis permitted to conclude that the dentin laser irradiation showed different and less intense superficial alteration when compared with retrofilling materials. In most cases, the alterations to the material surfaces showed cavities and craters. Group B presented more irregular and affected surfaces, creating blank spaces in the adjacent areas to the radicular dentinal surfaces after laser application, probably because of the carbonization.

  18. Effect of different laser irradiation on the dysentery bacilli

    NASA Astrophysics Data System (ADS)

    Ou, Lin; Chen, Rong; Chen, Yanjiao; Li, Depin; Wen, Caixia

    1998-08-01

    The S. flexnesi, which have high drug-resistance especially in Cm, Sm, Tc, SD, were irradiated by Ar+ laser at 488 nm and semiconductor laser at 808 nm. The experiment results have shown that both Ar+ laser and semiconductor laser with power density of 1.7 w/cm2 and irradiation dose of 2000 J/cm2 can conduce to the bacterial lethality and increase the mutation rates of the bacterial drug-sensitivity, and 'Colony Count' method have the superiority over the 'Inhibacteria Ring' method. At the mean time it further indicate that the high power semiconductor laser would play an important role in the sciences of laser biological medicine. But the effect of the near infrared semiconductor laser is far lower than that of Ar+ laser of shorter wavelength at the same irradiation dose. It is clear that the output and irradiation dose of near infrared semiconductor laser shall be increased in order to get the same rates of the bacterial lethality and the drug-sensitivity mutation as Ar+ laser's.

  19. System for obtaining smooth laser beams where intensity variations are reduced by spectral dispersion of the laser light (SSD)

    DOEpatents

    Skupsky, S.; Kessler, T.J.; Short, R.W.; Craxton, S.; Letzring, S.A.; Soures, J.

    1991-09-10

    In an SSD (smoothing by spectral dispersion) system which reduces the time-averaged spatial variations in intensity of the laser light to provide uniform illumination of a laser fusion target, an electro-optic phase modulator through which a laser beam passes produces a broadband output beam by imposing a frequency modulated bandwidth on the laser beam. A grating provides spatial and angular spectral dispersion of the beam. Due to the phase modulation, the frequencies (''colors'') cycle across the beam. The dispersed beam may be amplified and frequency converted (e.g., tripled) in a plurality of beam lines. A distributed phase plate (DPP) in each line is irradiated by the spectrally dispersed beam and the beam is focused on the target where a smooth (uniform intensity) pattern is produced. The color cycling enhances smoothing and the use of a frequency modulated laser pulse prevents the formation of high intensity spikes which could damage the laser medium in the power amplifiers. 8 figures.

  20. Time-resolved analysis of thickness-dependent dewetting and ablation of silver films upon nanosecond laser irradiation

    NASA Astrophysics Data System (ADS)

    Qi, Dongfeng; Paeng, Dongwoo; Yeo, Junyeob; Kim, Eunpa; Wang, Letian; Chen, Songyan; Grigoropoulos, Costas P.

    2016-05-01

    Nanosecond pulsed laser dewetting and ablation of thin silver films is investigated by time-resolved imaging. Laser pulses of 532 nm wavelength and 5 ns temporal width are irradiated on silver films of different thicknesses (50 nm, 80 nm, and 350 nm). Below the ablation threshold, it is observed that the dewetting process does not conclude until 630 ns after the laser irradiation for all samples, forming droplet-like particles in the spot central region. At higher laser intensities, ablative material removal occurs in the spot center. Cylindrical rims are formed in the peripheral dewetting zone due to the solidification of transported matter at about 700 ns following the laser pulse exposure. In addition to these features, droplet fingers are superposed upon irradiation of 350-nm thick silver films with higher intensity.

  1. Relativistic focusing and ponderomotive channeling of intense laser beams

    PubMed

    Hafizi; Ting; Sprangle; Hubbard

    2000-09-01

    The ponderomotive force associated with an intense laser beam expels electrons radially and can lead to cavitation in plasma. Relativistic effects as well as ponderomotive expulsion of electrons modify the refractive index. An envelope equation for the laser spot size is derived, using the source-dependent expansion method with Laguerre-Gaussian eigenfunctions, and reduced to quadrature. The envelope equation is valid for arbitrary laser intensity within the long pulse, quasistatic approximation and neglects instabilities. Solutions of the envelope equation are discussed in terms of an effective potential for the laser spot size. An analytical expression for the effective potential is given. For laser powers exceeding the critical power for relativistic self-focusing the analysis indicates that a significant contraction of the spot size and a corresponding increase in intensity is possible. PMID:11088939

  2. Relativistic focusing and ponderomotive channeling of intense laser beams

    SciTech Connect

    Hafizi, B.; Ting, A.; Sprangle, P.; Hubbard, R. F.

    2000-09-01

    The ponderomotive force associated with an intense laser beam expels electrons radially and can lead to cavitation in plasma. Relativistic effects as well as ponderomotive expulsion of electrons modify the refractive index. An envelope equation for the laser spot size is derived, using the source-dependent expansion method with Laguerre-Gaussian eigenfunctions, and reduced to quadrature. The envelope equation is valid for arbitrary laser intensity within the long pulse, quasistatic approximation and neglects instabilities. Solutions of the envelope equation are discussed in terms of an effective potential for the laser spot size. An analytical expression for the effective potential is given. For laser powers exceeding the critical power for relativistic self-focusing the analysis indicates that a significant contraction of the spot size and a corresponding increase in intensity is possible. (c) 2000 The American Physical Society.

  3. Scaling Laws for Proton Acceleration from the Rear Surface of Laser-Irradiated Thin Foils

    SciTech Connect

    Fuchs, J.; Antici, P.; D'Humieres, E.; Lefebvre, E.; Borghesi, M.; Cecchetti, C. A.; Brambrink, E.; Audebert, P.; Kaluza, M.; Schreiber, J.; Malka, V.; Manclossi, M.; Meyroneinc, S.; Mora, P.; Toncian, T.; Pepin, H.

    2006-04-07

    In the last few years, intense research has been conducted on the topic of laser-accelerated ion sources and their applications. Ultra-bright beams of multi-MeV protons are produced by irradiating thin metallic foils with ultra-intense short laser pulses. These sources open new opportunities for ion beam generation and control, and could stimulate development of compact ion accelerators for many applications, in particular proton therapy of deep-seated tumours. Here we show that scaling laws deduced from fluid models reproduce well the acceleration of proton beams for a large range of laser and target parameters. These scaling laws show that, in our regime, there is an optimum in the laser pulse duration of {approx}200 fs-1 ps, with a needed laser energy level of 30 to 100 J, in order to achieve e.g. 200 MeV energy protons necessary for proton therapy.

  4. Microengineering Laser Plasma Interactions at Relativistic Intensities.

    PubMed

    Jiang, S; Ji, L L; Audesirk, H; George, K M; Snyder, J; Krygier, A; Poole, P; Willis, C; Daskalova, R; Chowdhury, E; Lewis, N S; Schumacher, D W; Pukhov, A; Freeman, R R; Akli, K U

    2016-02-26

    We report on the first successful proof-of-principle experiment to manipulate laser-matter interactions on microscales using highly ordered Si microwire arrays. The interaction of a high-contrast short-pulse laser with a flat target via periodic Si microwires yields a substantial enhancement in both the total and cutoff energies of the produced electron beam. The self-generated electric and magnetic fields behave as an electromagnetic lens that confines and guides electrons between the microwires as they acquire relativistic energies via direct laser acceleration. PMID:26967419

  5. Microengineering Laser Plasma Interactions at Relativistic Intensities

    NASA Astrophysics Data System (ADS)

    Jiang, S.; Ji, L. L.; Audesirk, H.; George, K. M.; Snyder, J.; Krygier, A.; Poole, P.; Willis, C.; Daskalova, R.; Chowdhury, E.; Lewis, N. S.; Schumacher, D. W.; Pukhov, A.; Freeman, R. R.; Akli, K. U.

    2016-02-01

    We report on the first successful proof-of-principle experiment to manipulate laser-matter interactions on microscales using highly ordered Si microwire arrays. The interaction of a high-contrast short-pulse laser with a flat target via periodic Si microwires yields a substantial enhancement in both the total and cutoff energies of the produced electron beam. The self-generated electric and magnetic fields behave as an electromagnetic lens that confines and guides electrons between the microwires as they acquire relativistic energies via direct laser acceleration.

  6. The interaction of intense femtosecond laser pulses with solid targets

    SciTech Connect

    Klem, D.E.; Darrow, C.; Lane, S.; Perry, M.D.

    1992-12-30

    The absorption of 800 fsec Nd-glass laser pulses obliquely incident on solid targets is measured at intensities up to 10[sup 18] W/cm[sup 2]. The associated production of hard x-rays is also measured.

  7. The interaction of intense femtosecond laser pulses with solid targets

    SciTech Connect

    Klem, D.E.; Darrow, C.; Lane, S.; Perry, M.D.

    1992-12-30

    The absorption of 800 fsec Nd-glass laser pulses obliquely incident on solid targets is measured at intensities up to 10{sup 18} W/cm{sup 2}. The associated production of hard x-rays is also measured.

  8. Laser Irradiation of Aqueous Solutions for Application in Inductively Coupled Plasma Spectrometry

    NASA Astrophysics Data System (ADS)

    Su, H.; Xu, L.; Chen, J.; Li, X.; Wang, Y.

    2016-01-01

    The sensitivity of detection of trace heavy metal elements in water samples by inductively coupled plasma (ICP) spectrometry has been improved applying a 10.6 μm infrared laser to irradiate the aqueous solution. With optimal laser power density and irradiation time, the surface tension and viscosity of the aqueous solution were reduced by 38.09 and 11.35%, respectively. The nebulization efficiency of the processed solution in ICP was increased by 47.14%. The spectral intensity and signal-to-noise ratio (SNR) of the trace heavy metal elements including As, Cd, Cr, Cu, Hg, and Pb in the treated aqueous solution were both increased. Our experiment demonstrated that irradiation using an infrared laser at 10.6 μm is a simple and effective method to improve the detection sensitivity of ICP spectrometry for trace heavy metal elements.

  9. Formation of the uniform irradiation of a target in high-power laser facilities

    SciTech Connect

    Garanin, Sergey G; Derkach, Vladimir N; Shnyagin, Roman A

    2004-05-31

    The methods are developed for obtaining highly uniform laser beams for direct irradiation of targets in high-power laser facilities being designed. The methods are based on the optimisation of the mutual arrangement of the beams irradiating a target, the use of stationary phase plates for the formation of the specified radiation intensity distribution on the target, and the employment of the spatiotemporal beam smoothing to suppress small-scale inhomogeneities. The requirements on different systems of the facility are considered which provide the necessary accuracy of the beam steering on a target and the admissible difference in the intensities of the beams. A method is proposed for the spatiotemporal beam smoothing using the nonstationary properties of a laser plasma. The possibilities of this method are studied experimentally. (invited paper)

  10. Ablation experiment and threshold calculation of titanium alloy irradiated by ultra-fast pulse laser

    SciTech Connect

    Zheng, Buxiang; Jiang, Gedong; Wang, Wenjun Wang, Kedian; Mei, Xuesong

    2014-03-15

    The interaction between an ultra-fast pulse laser and a material's surface has become a research hotspot in recent years. Micromachining of titanium alloy with an ultra-fast pulse laser is a very important research direction, and it has very important theoretical significance and application value in investigating the ablation threshold of titanium alloy irradiated by ultra-fast pulse lasers. Irradiated by a picosecond pulse laser with wavelengths of 1064 nm and 532 nm, the surface morphology and feature sizes, including ablation crater width (i.e. diameter), ablation depth, ablation area, ablation volume, single pulse ablation rate, and so forth, of the titanium alloy were studied, and their ablation distributions were obtained. The experimental results show that titanium alloy irradiated by a picosecond pulse infrared laser with a 1064 nm wavelength has better ablation morphology than that of the green picosecond pulse laser with a 532 nm wavelength. The feature sizes are approximately linearly dependent on the laser pulse energy density at low energy density and the monotonic increase in laser pulse energy density. With the increase in energy density, the ablation feature sizes are increased. The rate of increase in the feature sizes slows down gradually once the energy density reaches a certain value, and gradually saturated trends occur at a relatively high energy density. Based on the linear relation between the laser pulse energy density and the crater area of the titanium alloy surface, and the Gaussian distribution of the laser intensity on the cross section, the ablation threshold of titanium alloy irradiated by an ultra-fast pulse laser was calculated to be about 0.109 J/cm{sup 2}.

  11. Toward attosecond electron pulses using ultra-intense lasers

    NASA Astrophysics Data System (ADS)

    Varin, Charles; Fortin, Pierre-Louis; Piché, Michel

    2008-06-01

    In many countries around the world, ultra-intense laser facilities are being built. These state-of-the-art lasers are intended for innovative medical and technological applications, as well as for basic experiments at the frontiers of fundamental science. Laser particle acceleration is a promising new endeavor. Recently developed schemes using radially polarized beams could help in reaching unprecedentedly short electron pulse durations, well in the attosecond range and potentially in the subattosecond range.

  12. Platinum nanostructures formed by femtosecond laser irradiation in water

    SciTech Connect

    Huo Haibin; Shen Mengyan

    2012-11-15

    Platinum nanostructures with various morphologies, such as spike-like, ripple-like and array-like structures, have been fabricated by 400 nm and 800 nm femtosecond laser irradiation in water. Different structures can be formed on the surfaces as a function of the laser wavelength, the fluence and scan methods. The reflectance measurements of these structures show much larger absorption on the irradiated surfaces than untreated platinum surfaces.

  13. Monoenergetic proton emission from nuclear reaction induced by high intensity laser-generated plasma

    SciTech Connect

    Torrisi, L.; Cavallaro, S.; Giuffrida, L.; Cutroneo, M.; Krasa, J.; Margarone, D.; Velyhan, A.; Ullschmied, J.; Kravarik, J.; Wolowski, J.; Szydlowski, A.; Rosinski, M.

    2012-02-15

    A 10{sup 16} W/cm{sup 2} Asterix laser pulse intensity, 1315 nm at the fundamental frequency, 300 ps pulse duration, was employed at PALS laboratory of Prague, to irradiate thick and thin primary CD{sub 2} targets placed inside a high vacuum chamber. The laser irradiation produces non-equilibrium plasma with deutons and carbon ions emission with energy of up to about 4 MeV per charge state, as measured by time-of-flight (TOF) techniques by using ion collectors and silicon carbide detectors. Accelerated deutons may induce high D-D cross section for fusion processes generating 3 MeV protons and 2.5 MeV neutrons, as measured by TOF analyses. In order to increase the mono-energetic proton yield, secondary CD{sub 2} targets can be employed to be irradiated by the plasma-accelerated deutons. Experiments demonstrated that high intensity laser pulses can be employed to promote nuclear reactions from which characteristic ion streams may be developed. Results open new scenario for applications of laser-generated plasma to the fields of ion sources and ion accelerators.

  14. Theoretical Studies on Intense Laser Produced Quasi-Monoenergetic Particle Beams

    SciTech Connect

    Sheng, Z. M.; Zhang, J.; Wang, W. M.; Yan, X. Q.; Chen, M.; Chen, J. E.

    2009-07-25

    A brief review is presented on our recent theoretical studies on the quasi-monoenergetic electron and proton beam generation by intense laser pulses. For the electron beam generation from laser wakefields, the mechanisms of electron injection by a laser pulse in the colliding geometry are investigated. It shows that there exist two mechanisms, which are called collective injection and stochastic injection. The number of injection electrons is studied as a function of the injection pulse intensity, pulse duration, as well as laser polarization. The injection by a transverse intersecting laser pulse is also investigated, which appears relatively easy for experimental setup. The required laser parameters are comparable to the colliding geometry. The proton acceleration by collisionless electrostatic shock waves is investigated and shock wave propagation through the interface of two targets with different ion species is simulated. It is found that ions with a relatively large charge-to-mass ratio can be accelerated successively in two counter-propagating shocks when they are overtaken by shock fronts until their energy is larger than the scalar potential of the shock waves. A scheme of ion acceleration in the new parameter regime called phase stable acceleration is proposed with the use of circularly-polarized laser pulses irradiating on very thin solid targets, which would enable one to obtain quasi-monoenergetic proton beams of multi-100 MeV with 100 TW-class lasers.

  15. Experimental study on photodiode damage by millisecond pulse laser irradiation

    NASA Astrophysics Data System (ADS)

    Wei, Zhi; Jin, Guangyong; Tan, Yong; Wang, Di

    2015-10-01

    The photoelectric detector is a very significance part in laser and its application system, but when photoelectric detector irradiated by high energy laser, the laser may cause thermal damage to the photoelectric detector, when the temperature more than its melting point and vaporization point, there will be a permanent damage in PIN photodetector, leading to the failure of photoelectric detector. In order to study the photodiode damage mechanism by millisecond pulse laser irradiation, a set of experimental system has been built, choosing appropriate pulsed laser parameters to irradiate silicon-based PIN photodiode and monitoring the surface temperature in the process of irradiation, until the PIN photodiode complete failure. The measurement results of real-time temperature, responsivity change and damage morphology were analyzed to conclude the failure reason of the PIN photodiode. The results showed that with the increase of laser energy, the PIN photodiode surface temperature would be also increased accordingly. Before the laser irradiation, the responsivity of PIN photodiode was the same. But after the laser irradiation, the responsivity of the PIN photodiode would be changed and with the increase of laser energy, the decline extent of responsivity would be also increased. Judging from the ablation, crack and fold zone on the surface of PIN photodiode after the laser irradiation, the damage was for thermal stress effect. The continuity of material confined its free expansion. Therefore, the uneven thermal expansion induced the great thermal stress. At the same time, the silicon transited from brittle to ductile and the yield strength dramatically decreased. Once the maximum thermal stress exceeded the critical stress, the plastic deformation and the brittle cracks of silicon would be generated. With the increase of laser energy, the thermal stress damage extent of PIN photodiode would be also increased accordingly and the black area of laser ablation would be

  16. Implantation of Organic Molecules into Biotissue by Pulsed Laser Irradiation

    NASA Astrophysics Data System (ADS)

    Goto, Masahiro; Ichinose, Nobuyuki; Kawanishi, Shunichi; Fukumura, Hiroshi

    1999-01-01

    Zinc tetraphenyl porphyrin (ZnTPP) molecules were implanted into a piece of chicken skin by irradiation with KrF laser pulses. The study of the implanted ZnTPP at the skin surface using a fluorescence microscope indicated that the molecules are space-selectively introduced at the irradiated area.

  17. Homogeneous focusing with a transient soft X-ray laser for irradiation experiments

    NASA Astrophysics Data System (ADS)

    Kazamias, S.; Cassou, K.; Guilbaud, O.; Klisnick, A.; Ros, D.; Plé, F.; Jamelot, G.; Rus, B.; Koslová, M.; Stupka, M.; Mocek, T.; Douillet, D.; Zeitoun, Ph.; Joyeux, D.; Phalippou, D.

    2006-07-01

    We report the work done on a transient soft X-ray laser (SXRL) beam to deliver a proper extreme UV irradiation source for applications. The same optical tool was first demonstrated on a quasi stationnary state (QSS) soft X-Ray laser at the PALS Institute in Prague. The problem set by the transient soft X-Ray laser developed by the LIXAM at the LULI installation in Palaiseau is more crucial, first because the beam spatial profile is more irregular secondly because high repetition rate soft X-ray laser facilities in the future are based on this SXRL type. The spots obtained show a 20 micron average diameter and a rather homogeneous and smooth profile that make them a realistic irradiation source to interact with targets requiring relatively high fluence (near 1 J/cm 2) or intensity (near 10 11 W/cm 2) in the extreme UV domain.

  18. Effect of laser intensity on radio frequency emissions from laser induced breakdown of atmospheric air

    NASA Astrophysics Data System (ADS)

    Vinoth Kumar, L.; Manikanta, E.; Leela, Ch.; Prem Kiran, P.

    2016-06-01

    The studies on the effect of input laser intensity, through the variation of laser focusing geometry, on radio frequency (RF) emissions, over 30-1000 MHz from nanosecond (ns) and picosecond (ps) laser induced breakdown (LIB) of atmospheric air are presented. The RF emissions from the ns and ps LIB were observed to be decreasing and increasing, respectively, when traversed from tight to loose focusing conditions. The angular and radial intensities of the RF emissions from the ns and ps LIB are found to be consistent with sin2θ/r2 dependence of the electric dipole radiation. The normalized RF emissions were observed to vary with incident laser intensity (Iλ2), indicating the increase in the induced dipole moment at moderate input laser intensities and the damping of radiation due to higher recombination rate of plasma at higher input laser intensities.

  19. Viability of fibroblasts cultured under nutritional stress irradiated with red laser, infrared laser, and red light-emitting diode

    NASA Astrophysics Data System (ADS)

    Volpato, Luiz Evaristo Ricci; de Oliveira, Rodrigo Cardoso; Espinosa, Mariano Martinez; Bagnato, Vanderley Salvador; Machado, Maria A. A. M.

    2011-07-01

    Phototherapy is noninvasive, painless and has no known side effect. However, for its incorporation into clinical practice, more well-designed studies are necessary to define optimal parameters for its application. The viability of fibroblasts cultured under nutritional stress irradiated with either a red laser, an infrared laser, or a red light-emitting diode (LED) was analyzed. Irradiation parameters were: red laser (660 nm, 40 mW, 1 W/cm2), infrared laser (780 nm, 40 mW, 1 W/cm2), and red LED (637 +/- 15 nm, 40 mW, 1 W/cm2). All applications were punctual and performed with a spot with 0.4 mm2 of diameter for 4 or 8 s. The Kruskal-Wallis test and analysis of variance of the general linear model (p <= 0.05) were used for statistical analysis. After 72 h, phototherapy with low-intensity laser and LED showed no toxicity at the cellular level. It even stimulated methylthiazol tetrazolium assay (MTT) conversion and neutral red uptake of fibroblasts cultured under nutritional stress, especially in the group irradiated with infrared laser (p = 0.004 for MTT conversion and p < 0.001 for neutral red uptake). Considering the parameters and protocol of phototherapy used, it can be concluded that phototherapy stimulated the viability of fibroblasts cultured under nutritional deficit resembling those found in traumatized tissue in which cell viability is reduced.

  20. Vacuum electron acceleration by an intense laser

    SciTech Connect

    Wang, P.X.; Ho, Y.K.; Yuan, X.Q.; Kong, Q.; Sessler, A.M.; Esarey, E.; Nishida, Y.

    2001-01-12

    Using 3D test particle simulations, the characteristics and essential conditions under which an electron, in a vacuum laser beam, can undergo a capture and acceleration scenario (CAS). When a{sub 0} {approx}> 100 the electron can be captured and violently accelerated to energies {approx}> 1 GeV, with an acceleration gradient {approx}> 10 GeV/cm, where a{sub 0} = eE{sub 0}/m{sub e}{omega}c is the normalized laser field amplitude. The physical mechanism behind the CAS is that diffraction of the focused laser beam leads to a slowing down of the effective wave phase velocity along the captured electron trajectory, such that the electron can be trapped in the acceleration phase of the wave for a longer time and thus gain significant energy from the field.

  1. Injection locking and saturation intensity of a cadmium iodide laser.

    PubMed

    Greene, D P; Eden, J G

    1985-02-01

    A discharge-pumped cadmium monoiodide (CdI) laser utilizing isotopically pure CdI(2) ((114)CdI(2)) has been injection locked with a flashlamp-pumped dye laser having a linewidth of 0.3 cm(-1). Complete locking of the slave oscillator occurs for wavelengths between 655 and 660 nm and for injection intensities of ~5 W cm(-2). The saturation intensity for the B ? X band of CdI has been directly measured with an excimer-pumped dye laser to be (125 +/- 60) kW cm(-2). PMID:19724345

  2. Hybrid proton acceleration scheme using relativistic intense laser light

    SciTech Connect

    Andreev, A. A.; Platonov, K. Yu.; Schnuerer, M.; Prasad, R.; Ter-Avetisyan, S.

    2013-03-15

    Ion acceleration phenomena at relativistic intense laser interaction with thin foil targets are studied to find an efficient laser-target interaction concept at the conditions, where neither the ponderomotive pressure of the laser light nor the hot electron pressure is negligible. Particle in cell simulations and the analytical model are allowing to predict optimum laser-target parameters and suggesting a significant increase of proton energy if a hybrid proton acceleration scheme is used. In the proposed scenario, the laser polarisation is changed during the acceleration process: First with circularly polarised laser light the target is accelerated as a whole by the ponderamotive pressure, and then with linearly polarised laser light the electrons are heated which additionally increases the accelerating field. The calculations are in good agreement with experimental findings.

  3. Dynamics of intense laser propagation in underdense plasma: Polarization dependence

    SciTech Connect

    Singh, D. K.; Fiuza, F.; Silva, L. O.; Davies, J. R.; Sarri, G.

    2012-07-15

    We present a comprehensive numerical study of the dynamics of an intense laser pulse as it propagates through an underdense plasma in two and three dimensions. By varying the background plasma density and the polarization of the laser beam, significant differences are found in terms of energy transport and dissipation, in agreement with recently reported experimental results. Below the threshold for relativistic self-focusing, the plasma and laser dynamics are observed to be substantially insensitive to the initial laser polarization, since laser transport is dominated by ponderomotive effects. Above this threshold, relativistic effects become important, and laser energy is dissipated either by plasma heating (p-polarization) or by trapping of electromagnetic energy into plasma cavities (s-polarization) or by a combination of both (circular polarization). Besides the fundamental interest of this study, the results presented are relevant to applications such as plasma-based accelerators, x-ray lasers, and fast-ignition inertial confinement fusion.

  4. MeV negative ion source from ultra-intense laser-matter interaction

    SciTech Connect

    Ter-Avetisyan, S.; Ramakrishna, B.; Doria, D.; Prasad, R.; Borghesi, M.; Andreev, A. A.; Steinke, S.; Schnuerer, M.; Nickles, P. V.; Tikhonchuk, V.

    2012-02-15

    Experimental demonstration of negative ion acceleration to MeV energies from sub-micron size droplets of water spray irradiated by ultra-intense laser pulses is presented. Thanks to the specific target configuration and laser parameters, more than 10{sup 9} negative ions per steradian solid angle in 5% energy bandwidth are accelerated in a stable and reliable manner. To our knowledge, by virtue of the ultra-short duration of the emission, this is by far the brightest negative ion source reported. The data also indicate the existence of beams of neutrals with at least similar numbers and energies.

  5. MeV negative ion generation from ultra-intense laser interaction with a water spray

    SciTech Connect

    Ter-Avetisyan, S.; Ramakrishna, B.; Borghesi, M.; Doria, D.; Zepf, M.; Sarri, G.; Ehrentraut, L.; Steinke, S.; Sandner, W.; Schnuerer, M.; Andreev, A.; Nickles, P. V.; Tikhonchuk, V.

    2011-08-01

    MeV negative oxygen ions are obtained from a water spray target irradiated by high intensity (5 x 10{sup 19} W/cm{sup 2}) and ultrashort (50 fs) laser pulses. Generation of negative ions is ascribed to electron-capture processes that the laser-accelerated high-energy positive ion experiences when it interacts with atoms in the spray. This mechanism implies the existence of a large number of MeV neutral oxygen atoms, which is consistent with indirect experimental evidence.

  6. Kinetic energy of ions after Coulomb explosion of clusters induced by an intense laser pulse

    SciTech Connect

    Islam, Md. Ranaul; Saalmann, Ulf; Rost, Jan M.

    2006-04-15

    It is shown that the kinetic-energy distribution of ions emerging from a cluster target irradiated by an intense laser pulse arises from three main effects: (1) the spatial profile of the laser beam (2) the cluster size distribution in the experiment, and (3) possible saturation effects in the cluster ionization. Our model reveals that each of these effects leaves a characteristic fingerprint in the ion kinetic-energy spectrum. Moreover, it provides a quantitative link between observable ion spectra under experimental conditions and the ideal single-cluster result of a typical calculation.

  7. Recent experiment on fast electron transport in ultra-high intensity laser interaction

    NASA Astrophysics Data System (ADS)

    Batani, D.; Baton, S.; Koenig, M.; Guillou, P.; Loupias, B.; Vinci, T.; Rousseaux, C.; Gremillet, L.; Morace, A.; Redaelli, R.; Nakatsutsumi, M.; Kodama, R.; Ozaki, N.; Norimatsu, T.; Rassuchine, J.; Cowan, T.; Dorchies, F.; Fourment, C.; Santos, J. J.

    2008-05-01

    We performed an experiment with cone targets in planar geometry devoted to the study of fast electron generation, propagation, and target heating. This was done at LULI with the 100 TW laser at intensities up to 1019 W/cm2. Fast electrons penetration, with and without cones, was studied with different diagnostics (Kα imaging, Kα spectroscopy, visible emission) for ω or 2ω irradiation. At ω, the pre-plasma generated by the laser pedestal fills the cone and prevents the beam from reaching the tip.

  8. Effect of Relativistic Plasma on Extreme-Ultraviolet Harmonic Emission from Intense Laser-Matter Interactions

    SciTech Connect

    Krushelnick, K.; Dangor, A. E.; Mangles, S. P. D.; Rozmus, W.; Wagner, U.; Habara, H.; Norreys, P. A.; Beg, F. N.; Wei, M. S.; Bochkarev, S. G.; Clark, E. L.; Gopal, A.; Evans, R. G.; Robinson, A. P. L.; Tatarakis, M.; Zepf, M.

    2008-03-28

    Experiments were performed in which intense laser pulses (up to 9x10{sup 19} W/cm{sup 2}) were used to irradiate very thin (submicron) mass-limited aluminum foil targets. Such interactions generated high-order harmonic radiation (greater than the 25th order) which was detected at the rear of the target and which was significantly broadened, modulated, and depolarized because of passage through the dense relativistic plasma. The spectral modifications are shown to be due to the laser absorption into hot electrons and the subsequent sharply increasing relativistic electron component within the dense plasma.

  9. Observations of the filamentation of high-intensity laser-produced electron beams

    SciTech Connect

    Wei, M.S.; Beg, F.N.; Dangor, A.E.; Gopal, A.; Tatarakis, M.; Krushelnick, K.; Clark, E.L.; Evans, R.G.; Ledingham, K.W.D.; McKenna, P.; Norreys, P.A.; Zepf, M.

    2004-11-01

    Filamented electron beams have been observed to be emitted from the rear of thin solid targets irradiated by a high-intensity short-pulse laser when there is low-density plasma present at the back of the target. These observations are consistent with a laser-generated beam of relativistic electrons propagating through the target, which is subsequently fragmented by a Weibel-like instability in the low-density plasma at the rear. These measurements are in agreement with particle-in-cell simulations and theory, since the filamentation instability is predicted to be dramatically enhanced when the electron beam density approaches that of the background plasma.

  10. High-intensity laser therapy during chronic degenerative tenosynovitis experimentally induced in broiler chickens

    NASA Astrophysics Data System (ADS)

    Fortuna, Damiano; Rossi, Giacomo; Bilotta, Teresa W.; Zati, Allesandro; Gazzotti, Valeria; Venturini, Antonio; Pinna, Stefania; Serra, Christian; Masotti, Leonardo

    2002-10-01

    The aims of this study was the safety and the efficacy of High Intensity Laser Therapy (HILT) on chronic degenerative tenosynovitis. We have effectuated the histological evaluation and seroassay (C reactive protein) on 18 chickens affect by chronic degenerative tenosynovitis experimentally induced. We have been employed a Nd:YAG laser pulsed wave; all irradiated subjects received the same total energy (270 Joule) with a fluence of 7,7 J/cm2 and intensity of 10,7 W/cm2. The histological findings revealed a distinct reduction of the mineralization of the choral matrix, the anti-inflammatory effect of the laser, the hyperplasia of the synoviocytes and ectasia of the lymphatic vessels.

  11. Lip and oral venous varices treated by photocoagulation with high-intensity diode laser.

    PubMed

    Azevedo, Luciane H; Del Vechio, Aluana; Nakajima, Edgar; Galletto, Vivian; Migliari, Dante A

    2013-02-01

    Lip and oral venous varices are acquired benign vascular lesions characterized by a darkblue to violaceous papule or nodule, commonly found on the ventral tongue and lower lip. Although these lesions are usually asymptomatic, they can bleed if injured. This study assessed the effectiveness of photocoagulation with high-intensity diode laser in the treatment of these lesions. Thirty-two patients (14 men and 18 women; mean age, 56 years) with lip and oral venous varices were examined and treated with a noncontact diode laser. With one exception, all cases were successfully treated with a single irradiation exposure session. Healing was complete in about 2 to 3 weeks; none of the patients experienced complications or recurrence. Photocoagulation with high-intensity diode laser was proven to be safe and effective for the treatment of lip and oral venous varices, with consistent results. PMID:23444183

  12. Short-pulse, high-intensity lasers at Los Alamos

    SciTech Connect

    Taylor, A.J.; Roberts, J.P.; Rodriguez, G.; Fulton, R.D.; Kyrala, G.A.; Schappert, G.T.

    1994-03-01

    Advances in ultrafast lasers and optical amplifiers have spurred the development of terawatt-class laser systems capable of delivering focal spot intensities approaching 10{sup 20} W/cm{sup 2}. At these extremely high intensities, the optical field strength is more than twenty times larger than the Bohr electric field, permitting investigations of the optical properties of matter in a previously unexplored regime. The authors describe two laser systems for high intensity laser interaction experiments: The first is a terawatt system based on amplification of femtosecond pulses in XeCl which yields 250 mJ in 275 fs and routinely produces intensifies on target in excess of 10{sup 18} W/cm{sup 2}. The second system is based on chirped pulse amplification of 100-fs pulses in Ti:sapphire.

  13. Spatial intensity profiling of an industrial laser welding system

    SciTech Connect

    Milewski, J.O.

    1991-12-31

    A investigation was conducted to devise a method to sense the laser beam intensity profile of an industrial laser welding system. The research focuses on monitoring methods and assessing locations within the system where data can be taken which reveal the relationship between the laser beam intensity profile and the input system parameters of the laser beam welding process. Emphasis has been placed on the configuration of a distributed computing environment to acquire, analyze and display the results of the sensed beam profile. Conventional image processing techniques are demonstrated. It was found that a distributed computing environment was useful for processing the large volumes of data generated by this process characterization method, and the distributed computing environment provided the computing power required for computationally intensive analysis and display techniques. The mathematical techniques used to discriminate one data set from another and relate the results to processing conditions are discussed.

  14. Vacuum aperture isolator for retroreflection from laser-irradiated target

    DOEpatents

    Benjamin, Robert F.; Mitchell, Kenneth B.

    1980-01-01

    The disclosure is directed to a vacuum aperture isolator for retroreflection of a laser-irradiated target. Within a vacuum chamber are disposed a beam focusing element, a disc having an aperture and a recollimating element. The edge of the focused beam impinges on the edge of the aperture to produce a plasma which refracts any retroreflected light from the laser's target.

  15. Relative intensity noise in high speed microcavity laser

    NASA Astrophysics Data System (ADS)

    Tan, F.; Wu, M. K.; Liu, M.; Feng, M.; Holonyak, N.

    2013-09-01

    We have fabricated a high speed single mode microcavity laser of the form of oxide-confined vertical cavity surface emitting laser (VCSEL) and achieved an ultralow threshold current (ITH = 0.13 mA at 20 °C) with lasing wavelength at 837 nm. The optical spectrum of the microcavity VCSEL exhibits a mode spacing of 3.1 nm, which is corresponding to an optical modal cavity dimension of 2.5 μm. The device exhibits an enhanced modulation bandwidth of 22.6 GHz and a thermal noise limited laser intensity noise (electrical power spectral density of laser intensity noise below the thermal noise floor -174 dBm/Hz) as a consequence of low power laser operation and reduced mode competition in the microcavity.

  16. Radial smoothing for improving laser-beam irradiance uniformity.

    PubMed

    Zhong, Zheqiang; Hou, Pengcheng; Zhang, Bin

    2015-12-15

    Laser-beam irradiation uniformity is a key issue in inertial confinement fusion research. We propose a radial smoothing (RS) approach in which the speckle in a focal plane is smoothed by the radial redistribution through fast focal zooming. This focal zooming is generated by introducing the periodical spherical wavefront modulation to the laser beam, based on an optical Kerr medium and its pump laser with the temporal profile of a Gaussian pulse train. The utilization of RS significantly improves the laser-beam uniformity without obvious impact on the performance of the high-power laser system. PMID:26670528

  17. Transient stress evolution and crystallization in laser-irradiated amorphous titania sol-gel films

    SciTech Connect

    Exarhos, G.J.; Hess, N.J. ); Wood, S. . Dept. of Physics)

    1991-10-01

    Amorphous TiO{sub 2} sol-gel films are irreversibly transformed to a crystalline anatase phase when heated to temperatures in excess of 575 K or subjected to intense pulsed or CW laser irradiation. The laser-induced transformation is initiated as a result of impurity absorption and subsequent heating, and results in densification and relative changes in compressive stress of the film. Isothermally annealed films exhibit a decrease in compressive stress as crystallization proceeds while an increase in compressive stress followed by a decrease in stress is observed when crystallization is laser-induced. Raman spectroscopy has been used to characterize the crystallization ingrowth kinetics and is used in this work as a real time probe of both film temperature and localized stress which can be evaluated from shifts in lattice phonon frequencies measured in real time during laser irradiation. The laser not only induces the phase transformation but excites inelastic Raman scattering from which film stress and temperature can be estimated. A second approach for the determination of these parameters requires incorporation of a thin ruby film between the titania and silica substrate. Here, the wavelength shift of the laser-induced ruby fluorescence can be used to quantify interfacial stress; the fluorescence lifetime measurements are used to determine temperature. The advantages and limitations of these techniques for evaluating transient stress and temperature evolution in thin titania films subjected to CW laser irradiation will be discussed.

  18. Photoelectric performance degradation of several laser-irradiated Si detectors

    NASA Astrophysics Data System (ADS)

    Moeglin, Jean-Pierre; Gautier, Bernard; Joeckle, Rene C.; Bolmont, Dominique

    1998-04-01

    The modifications of the basic photoelectric properties in visible Si photodiodes irradiated by laser pulses have been measured and an attempt to link them to the observed/computed dopant distribution has been performed. These detectors have been irradiated 'in band' with two types of lasers: 1) a Q-switched Nd:YAG laser, frequency doubled with a 'short' pulse duration of 4 ns and 2) dye laser R6G with a 'long' pulse of 2 microsecond(s) . The single pulse fluence range extended form 0.4 to 50 J/cm2 well above the surface melting fluence threshold. Specially manufactured detectors have been tested. These detectors have a linearly graded junction with different resistivities. The detector responsivity decrease (DRD) vs applied irradiation fluence has been measured for both irradiation types. SIMS has been used to measure the changes in the dopant profile. It has been shown that a large spreading with a 'plateau like shape' of the boron distribution is obtained, resulting from a gas phase diffusion of dopant during the vaporization/condensation cycle. A relationship between DRD and boron profile has been established for Si detectors irradiated by the dye laser. A local sensitivity drop of 70 percent inside the damaged area location has been measured. Furthermore, it has been shown that high irradiation fluences induce a sequential loss of the different photoelectric properties rather than a complete detector breakdown at a prescribed fluence threshold.

  19. The collimation of intense relativistic electron beams generated by ultra-intense femtosecond laser in nanometer-scale solid fiber array

    SciTech Connect

    Liao, Leng; Wu, Weidong; Wang, Chaoyang; Zhou, Minjie; Fu, Zhibing; Tang, Yongjian

    2014-02-24

    A scheme to collimate the ultra-intense laser generated MeV electrons by nanometer-scale solid fiber array is proposed. Unlike previous resistivity-structured target schemes, not the magnetic field but the electric field due to the anisotropic resistivity acts to collimate the divergent fast electrons. This concept is well supported by analytical estimation and numerical calculation. The measurements of collimated MeV electron beams at rear of carbon nanotube arrays irradiated by intense femtosecond laser show the viability of this scheme. These results indicate that potential applications include radiography, fast electron beam focusing, and perhaps the electron collimation for fast ignition of inertial confined fusion.

  20. The collimation of intense relativistic electron beams generated by ultra-intense femtosecond laser in nanometer-scale solid fiber array

    NASA Astrophysics Data System (ADS)

    Liao, Leng; Wu, Weidong; Wang, Chaoyang; Zhou, Minjie; Fu, Zhibing; Tang, Yongjian

    2014-02-01

    A scheme to collimate the ultra-intense laser generated MeV electrons by nanometer-scale solid fiber array is proposed. Unlike previous resistivity-structured target schemes, not the magnetic field but the electric field due to the anisotropic resistivity acts to collimate the divergent fast electrons. This concept is well supported by analytical estimation and numerical calculation. The measurements of collimated MeV electron beams at rear of carbon nanotube arrays irradiated by intense femtosecond laser show the viability of this scheme. These results indicate that potential applications include radiography, fast electron beam focusing, and perhaps the electron collimation for fast ignition of inertial confined fusion.

  1. [Morphologic examination of the urothelium after irradiation with laser energy].

    PubMed

    Hofmann, R; Hartung, R; Geissdörfer, K; Ascherl, R; Erhardt, W; Schmidt-Kloiber, H; Reichel, E; Schöffmann, H

    1987-01-01

    The energy of a Nd-YAG laser (1,064 nm wave length, 8 ns pulse duration) was used to irradiate the urothelium of the ureter or bladder and kidney parenchyma in pigs. Single pulse energy was 50-120 mJ with a 20-Hz repetition rate. The horizontal laser beam was reflected 90 degrees down by a 100% mirror and with a specially designed apparatus focussed on the surface of the tissue. Laser light from a quartz glass fiber was also focussed directly onto the tissue. Urothelium and kidney parenchyma were irradiated in 7 pigs. Tissue samples were examined histologically and raster electron microscopically 2, 4, 8 and 12 days after irradiation. No macroscopic lesion could be found. Maximum energy caused a small cone of 40 micron depth. No thermic effects or necrosis resulted, so that no harm is to be expected with unintentional irradiation. PMID:2896407

  2. The interaction of intense subpicosecond laser pulses with underdense plasmas

    SciTech Connect

    Coverdale, C.A.

    1995-05-11

    Laser-plasma interactions have been of interest for many years not only from a basic physics standpoint, but also for their relevance to numerous applications. Advances in laser technology in recent years have resulted in compact laser systems capable of generating (psec), 10{sup 16} W/cm{sup 2} laser pulses. These lasers have provided a new regime in which to study laser-plasma interactions, a regime characterized by L{sub plasma} {ge} 2L{sub Rayleigh} > c{tau}. The goal of this dissertation is to experimentally characterize the interaction of a short pulse, high intensity laser with an underdense plasma (n{sub o} {le} 0.05n{sub cr}). Specifically, the parametric instability known as stimulated Raman scatter (SRS) is investigated to determine its behavior when driven by a short, intense laser pulse. Both the forward Raman scatter instability and backscattered Raman instability are studied. The coupled partial differential equations which describe the growth of SRS are reviewed and solved for typical experimental laser and plasma parameters. This solution shows the growth of the waves (electron plasma and scattered light) generated via stimulated Raman scatter. The dispersion relation is also derived and solved for experimentally accessible parameters. The solution of the dispersion relation is used to predict where (in k-space) and at what frequency (in {omega}-space) the instability will grow. Both the nonrelativistic and relativistic regimes of the instability are considered.

  3. Improved field emission property of graphene by laser irradiation

    NASA Astrophysics Data System (ADS)

    Cai, Wenbo; Zeng, Baoqing; Liu, Jianlong; Guo, Jing; Li, Nannan; Chen, Lei; Chen, Hongwei

    2013-11-01

    Graphene oxide (GO) can be reduced to graphene by either laser irradiation or thermal annealing. To improve the field emission (FE) property, a pulse CO2 laser has been employed to irradiate GO films prepared by electrophoretic deposition (EPD). By varying the laser irradiation time, we were able to fabricate emitters with varied field enhancement factor. It has been found that the FE properties of laser irradiated films with optimized time 15 s were better than that of thermal annealed samples. The turn-on field (Eto) at 0.01 mA/cm2 was reduced from 3.4 to 2.4 V/μm, and the threshold field (Eth) at 1 mA/cm2 was reduced from 6.8 to 5.1 V/μm. Scanning electron microscopy (SEM) was taken to reveal the change of morphology after laser ablation, and it shows that the laser irradiation made great deal of graphene edges vertical to the substrate, which remarkably enhanced the FE properties. This kind of effective and convenience method made the graphene films as a potential field emitter for vacuum microelectronic devices.

  4. Research activities on high-intensity laser and high field physics at APRI-GIST

    NASA Astrophysics Data System (ADS)

    Jeong, Tae Moon

    2015-05-01

    The performance of a 0.1-Hz-repetition-rate, 30-fs, 1.5-PW Ti:sapphire laser which is using for research on high field physics in APRI-GIST is presented. The charged particles (electrons and protons) are accelerated and an efficient x-ray generation is demonstrated using the PW laser. Protons are accelerated up to 80 MeV when an ultra-thin polymer target is irradiated by a circularly-polarized PW laser pulse. Electrons are accelerated to multi-GeV level with a help of injector and accelerator scheme. In the relativistic harmonic generation experiment, the harmonic order is dramatically extended, by optimizing the intensity of pre-pulse level, up to 164th that corresponds to 4.9 nm in wavelength and the experimental results can be explained by the oscillatory flying mirror model. The upgrade of the PW laser to the multi-PW level is under way.

  5. Tight focusing of ultra-intense laser pulses by innovative plasma optics toward extreme intensity

    NASA Astrophysics Data System (ADS)

    Nakatsutsumi, M.; Kon, A.; Fuchs, J.; Buffechoux, S.; Audebert, P.; Kodama, R.

    2009-11-01

    With rapid advances in laser technology, laser beams are now available that can be routinely focused to intensities approaching >10^21 Wcm-2. Enhancement of laser intensity is achieved by truncating the pulse width, increasing the laser-energy, or reducing the focal spot size. Although the reduction of the spot size is the simplest among those, by using low f-number optics, this method is not frequently employed because of the difficulty in avoiding damage from target debris or complexity of alignment procedure. We developed for the first time very compact (<1 cm^3) extremely low f-number (0.4) plasma-based, confocal ellipsoid focusing systems. Direct measurement of the laser focal spot using low-energy laser indicates 1/5 reduction of spot size compared to standard focusing (using a f/3 optics). Around tenfold enhancement of laser intensity by reduction of the spot size for high power shots is clearly evidenced by remarkable enhancement of proton energy. The experiment was performed at LULI 100TW laser facility.

  6. Effects of laser irradiation on the morphology of Cu(110)

    SciTech Connect

    Brandstetter, T.; Draxler, M.; Hohage, M.; Zeppenfeld, P.; Stehrer, T.; Heitz, J.; Georgiev, N.; Martinotti, D.; Ernst, H.-J.

    2008-07-15

    The effects of pulsed laser irradiation on the morphology of the Cu(110) surface were investigated by means of reflectance difference spectroscopy (RDS) and spot profile analysis low-energy electron diffraction (SPA-LEED). The laser light induces surface defects (adatoms and islands) as well as subsurface dislocation lines. The high surface mobility leads to efficient annealing of the surface defects even at room temperature, whereas the subsurface dislocation lines persist up to temperatures T>800 K. SPA-LEED profiles of the (00) diffraction spot from the laser irradiated surface suggest an anisotropic distribution of the subsurface line defects related to the geometry of the fcc easy glide system, which is corroborated by STM measurements. Comparative experiments using conventional Ar ion bombardment point out the distinctiveness of the morphological changes induced by laser irradiation.

  7. Effect of laser irradiation on neutrophils metabolism in stress

    NASA Astrophysics Data System (ADS)

    Brill, Gregory E.; Grigoriev, Sergei N.; Romanova, Tatyana P.; Petrisheva, Svetlana G.

    1994-02-01

    In experiments on male mice of CBA line the alteration of neutrophils cytochemical profile in peripheral blood He-Ne laser irradiation in vitro (4 mW/cm2, 15 min) and modification of metabolic disturbances in polymorphonuclear leucocytes in stress by laser radiation were studied. It was found that direct laser irradiation of blood results in the decrease of glycogen and lipids content, the increase of ATP-ase, succinate dehydrogenase and myeloperoxidase activity, rise of lysosomal cationic proteins level, and membrane oxidase systems of neutrophils stimulation. In short-term immobilization stress conditions transcutaneous laser irradiation in vivo (19 mW/cm2, 15 min) prevents the development of stress induced changes of metabolism and function of neutrophils.

  8. Effect of low power laser irradiation on macrophage phagocytic capacity

    NASA Astrophysics Data System (ADS)

    Lu, Cuixia; Song, Sheng; Tang, Yu; Zhou, Feifan

    2011-03-01

    Phagocytosis and subsequent degradation of pathogens by macrophages play a pivotal role in host innate immunity in mammals. Laser irradiation has been found to produce photobiological effects with evidence of interference with immunological functions. However, the effects of laser on the immune response have not been extensively characterized. In this study, we focused our attention on the effects of He-Ne laser on the phagocytic activity of macrophages by using flow cytometry (FCM). After irradiating at fluence of 0, 1, 2 J/cm2 with He-Ne laser (632.8 nm, 3mw), the cells were incubated with microsphere and then subjected to FACS analysis. The results showed that Low-power laser irradiation (LPLI) leads to an increase in phagocytosis on both mouse peritoneal macrophages and the murine macrophage-like cell line RAW264.7. In addition, we demonstrated that LPLI increased phagocytosis of microsphere in a dose-dependent manner, reaching a maximum at fluence of 2 J/cm2. Taken together, our results indicated that Low-power laser irradiation with appropriate dosage can enhance the phagocytosis of macrophage, and provided a theoretical base for the clinical use of the He-Ne laser.

  9. Lateral propagation of MeV electrons generated by femtosecond laser irradiation

    SciTech Connect

    Seely, J. F.; Szabo, C. I.; Audebert, P.; Brambrink, E.; Tabakhoff, E.; Hudson, L. T.

    2010-02-15

    The propagation of MeV electrons generated by intense (approx =10{sup 20} W/cm{sup 2}) femtosecond laser irradiation, in the lateral direction perpendicular to the incident laser beam, was studied using targets consisting of irradiated metal wires and neighboring spectator wires embedded in electrically conductive (aluminum) or resistive (Teflon) substrates. The K shell spectra in the energy range 40-60 keV from wires of Gd, Dy, Hf, and W were recorded by a transmission crystal spectrometer. The spectra were produced by 1s electron ionization in the irradiated wire and by energetic electron propagation through the substrate material to the spectator wire of a different metal. The electron range and energy were determined from the relative K shell emissions from the irradiated and spectator wires separated by varying substrate lateral distances of up to 1 mm. It was found that electron propagation through Teflon was inhibited, compared to aluminum, implying a relatively weak return current and incomplete space-charge neutralization. The energetic electron propagation in the direction parallel to the electric field of the laser beam was larger than perpendicular to the electric field. Energetic electron production was lower when directly irradiating aluminum or Teflon compared to irradiating the heavy metal wires. These experiments are important for the determination of the energetic electron production mechanism and for understanding lateral electron propagation that can be detrimental to fast-ignition fusion and hard x-ray backlighter radiography.

  10. Decomposition of cyclohexane ion induced by intense femtosecond laser fields by ion-trap time-of-flight mass spectrometry

    NASA Astrophysics Data System (ADS)

    Yamazaki, Takao; Watanabe, Yusuke; Kanya, Reika; Yamanouchi, Kaoru

    2016-01-01

    Decomposition of cyclohexane cations induced by intense femtosecond laser fields at the wavelength of 800 nm is investigated by ion-trap time-of-flight mass spectrometry in which cyclohexane cations C6H12+ stored in an ion trap are irradiated with intense femtosecond laser pulses and the generated fragment ions are recorded by time-of-flight mass spectrometry. The various fragment ion species, C5Hn+ (n = 7, 9), C4Hn+ (n = 5-8), C3Hn+ (n = 3-7), C2Hn+ (n = 2-6), and CH3+, identified in the mass spectra show that decomposition of C6H12+ proceeds efficiently by the photo-irradiation. From the laser intensity dependences of the yields of the fragment ion species, the numbers of photons required for producing the respective fragment ions are estimated.

  11. Ultra-high intensity laser plasma interactions

    NASA Astrophysics Data System (ADS)

    Langdon, A. Bruce; Hinkel, D. E.; Lasinski, Barbara F.; Still, C. H.

    1997-11-01

    In current studies of plasma interactions relevant to the fast ignitor concept,footnote M. Tabak, et al., Phys. Plasmas 1, 1626 (1994). an ultra-high intensity beam propagates through underdense, relativistically transparent, and then near solid density plasmas to create a channel. The ultra-high intensity beam propagates through this channel toward the compressed core where it creates hot electrons as it is absorbed. Three-dimensional fluid simulation(R. L. Berger et al), Phys. Fluids B, 2243 (1993). (with relativistic enhancements) studies of self-focusing in the underdense plasma will be reported and compared to PIC simulations in the same parameter regime. Beam structure near focus detracts from channel formation. Modeling in support of upcoming 100TW will be presented.

  12. Importance of pulsed laser intensity in porphyrin-sensitized NADH photo-oxidation

    NASA Astrophysics Data System (ADS)

    Kirveliene, V.; Rotomskis, Ricardas; Juodka, B.; Piskarskas, Algis S.

    1991-05-01

    Porphyrin-type photosensitizers are the subject of intensive studies because of their successful use in photodynamic therapy. The suggestion that singlet molecular oxygen 1o2(1g),produced after the primary photophysical process, is the active agent in the cytotoxic action of porphyrin and light has gained general acceptance. However, this suggestion may not be relevant to the mechanism of intracellular photodamage to cells, where high concentration of reducing agent (i. e. NAD(P)H) and prevailing oxygen levels should favor the pathway, in which semi-oxidized substrate radical and semi-reduced dye radicals are generated. Excitation of the dye using a pulsed laser might lead to biphotonic processes and radical reactions not involving oxygen in the primary steps, thus overcoming tumor anoxia. The main documented results of the use of high peak power laser for photosensitized reactions were: 1, HP-sensitized tryptophan photodegradation induced by 20 MW cm2 peak intensity pulses (5 ns, 630 nm) was identical with that induced by cw light;1 2, protoporphyrin IX dimethyl ether irradiated with 2 GW cm peak intensity pulses (30 ps, 530 nm) showed a yield of photodecomposition substantially higher than that induced by cw irradiation. It is assumed that multi-step excitation is responsible for photodecomposition under powerful picosecond pulses;2 3, irradiation of Rose Bengal and red blood cells suspension with increasing intensities (40 ps, 532 nm) resulted in a decrease in acetyicholinesterase inhibition.3 On the other side the law of time-intensity reciprocity was verified in a wide range using cw irradiation sources.4

  13. Prepulse effect on intense femtosecond laser pulse propagation in gas

    SciTech Connect

    Giulietti, Antonio; Tomassini, Paolo; Galimberti, Marco; Giulietti, Danilo; Gizzi, Leonida A.; Koester, Petra; Labate, Luca; Ceccotti, Tiberio; D'Oliveira, Pascal; Auguste, Thierry; Monot, Pascal; Martin, Philippe

    2006-09-15

    The propagation of an ultrashort laser pulse can be affected by the light reaching the medium before the pulse. This can cause a serious drawback to possible applications. The propagation in He of an intense 60-fs pulse delivered by a Ti:sapphire laser in the chirped pulse amplification (CPA) mode has been investigated in conditions of interest for laser-plasma acceleration of electrons. The effects of both nanosecond amplified spontaneous emission and picosecond pedestals have been clearly identified. There is evidence that such effects are basically of refractive nature and that they are not detrimental for the propagation of a CPA pulse focused to moderately relativistic intensity. The observations are fully consistent with numerical simulations and can contribute to the search of a stable regime for laser acceleration.

  14. Intense tera-hertz laser driven proton acceleration in plasmas

    NASA Astrophysics Data System (ADS)

    Sharma, A.; Tibai, Z.; Hebling, J.

    2016-06-01

    We investigate the acceleration of a proton beam driven by intense tera-hertz (THz) laser field from a near critical density hydrogen plasma. Two-dimension-in-space and three-dimension-in-velocity particle-in-cell simulation results show that a relatively long wavelength and an intense THz laser can be employed for proton acceleration to high energies from near critical density plasmas. We adopt here the electromagnetic field in a long wavelength (0.33 THz) regime in contrast to the optical and/or near infrared wavelength regime, which offers distinct advantages due to their long wavelength ( λ = 350 μ m ), such as the λ 2 scaling of the electron ponderomotive energy. Simulation study delineates the evolution of THz laser field in a near critical plasma reflecting the enhancement in the electric field of laser, which can be of high relevance for staged or post ion acceleration.

  15. Thomson scattering in high-intensity chirped laser pulses

    NASA Astrophysics Data System (ADS)

    Holkundkar, Amol R.; Harvey, Chris; Marklund, Mattias

    2015-10-01

    We consider the Thomson scattering of an electron in an ultra-intense laser pulse. It is well known that at high laser intensities, the frequency and brilliance of the emitted radiation will be greatly reduced due to the electron losing energy before it reaches the peak field. In this work, we investigate the use of a small frequency chirp in the laser pulse in order to mitigate this effect of radiation reaction. It is found that the introduction of a negative chirp means the electron enters a high frequency region of the field while it still has a large proportion of its original energy. This results in a significant enhancement of the frequency and intensity of the emitted radiation as compared to the case without chirping.

  16. Thomson scattering in high-intensity chirped laser pulses

    SciTech Connect

    Holkundkar, Amol R.; Harvey, Chris Marklund, Mattias

    2015-10-15

    We consider the Thomson scattering of an electron in an ultra-intense laser pulse. It is well known that at high laser intensities, the frequency and brilliance of the emitted radiation will be greatly reduced due to the electron losing energy before it reaches the peak field. In this work, we investigate the use of a small frequency chirp in the laser pulse in order to mitigate this effect of radiation reaction. It is found that the introduction of a negative chirp means the electron enters a high frequency region of the field while it still has a large proportion of its original energy. This results in a significant enhancement of the frequency and intensity of the emitted radiation as compared to the case without chirping.

  17. Research of metallic materials irradiation with high energy pulsed laser impact

    NASA Astrophysics Data System (ADS)

    Blesman, A. I.; Postnikov, D. V.; Seropyan, G. M.; Tkachenko, E. A.; Teplouhov, A. A.; Polonyankin, D. A.

    2016-02-01

    In the process of metallic materials treatment by pulsed laser beams with nanosecond duration occurs extremely rapid and intensive heating of their surface. In this case a thin surface layer of material is heated to the boiling point and rapidly evaporates. This leads to arising substantial forces of reactive nature which significantly influence on the shape of the solidified melt and in some cases may cause deformation of the underlying layers. The considered question is relevant in the research of precision treatment of miniature products by laser beams. A metallic powder with microfine material structure was selected as the object of research and was exposed to laser irradiation with nanosecond duration. At the core of reactive forces calculation used the approach similar for laser rocket engines. The paper also presents the model and the results of the forces and the reactive recoil impulse calculation occurring during laser impact to the microfine metallic powder.

  18. Bursts of Terahertz Radiation from Large-Scale Plasmas Irradiated by Relativistic Picosecond Laser Pulses.

    PubMed

    Liao, G Q; Li, Y T; Li, C; Su, L N; Zheng, Y; Liu, M; Wang, W M; Hu, Z D; Yan, W C; Dunn, J; Nilsen, J; Hunter, J; Liu, Y; Wang, X; Chen, L M; Ma, J L; Lu, X; Jin, Z; Kodama, R; Sheng, Z M; Zhang, J

    2015-06-26

    Powerful terahertz (THz) radiation is observed from large-scale underdense preplasmas in front of a solid target irradiated obliquely with picosecond relativistic intense laser pulses. The radiation covers an extremely broad spectrum with about 70% of its energy located in the high frequency regime over 10 THz. The pulse energy of the radiation is found to be above 100  μJ per steradian in the laser specular direction at an optimal preplasma scale length around 40-50  μm. Particle-in-cell simulations indicate that the radiation is mainly produced by linear mode conversion from electron plasma waves, which are excited successively via stimulated Raman scattering instability and self-modulated laser wakefields during the laser propagation in the preplasma. This radiation can be used not only as a powerful source for applications, but also as a unique diagnostic of parametric instabilities of laser propagation in plasmas. PMID:26197129

  19. Treatment of acute pancreatitis with mexidol and low-intensity laser radiation

    NASA Astrophysics Data System (ADS)

    Parzyan, G. R.; Geinits, A. V.

    2001-04-01

    This article presents the results of treatment of 54 patients with acute pancreatitis. The patients were divided into two groups according to the method of treatment. The control group (26 patients) received a conventional therapy, whereas the experimental group (28 patients) received mexidol in combination with the intravenous laser irradiation of blood. Clinical and laboratory tests confirmed a high efficiency of the combined therapy based on the administration of mexidol antioxidant and low-intensity (lambda) equals 0.63 micrometers diode laser irradiation of blood. This therapeutic technique produced an influence on the basic pathogenetic mechanisms of acute pancreatitis. The application of this method of treatment improved the course and prognosis of acute pancreatitis.

  20. Infrared nanosecond pulsed laser irradiation of stainless steel: micro iron-oxide zones generation.

    PubMed

    Ortiz-Morales, M; Frausto-Reyes, C; Soto-Bernal, J J; Acosta-Ortiz, S E; Gonzalez-Mota, R; Rosales-Candelas, I

    2014-07-15

    Nanosecond-pulsed, infrared (1064 nm) laser irradiation was used to create periodic metal oxide coatings on the surface of two samples of commercial stainless steel at ambient conditions. A pattern of four different metal oxide zones was created using a galvanometer scanning head and a focused laser beam over each sample. This pattern is related to traverse direction of the laser beam scanning. Energy-dispersive X-ray spectroscopy (EDS) was used to find the elemental composition and Raman spectroscopy to characterize each oxide zone. Pulsed laser irradiation modified the composition of the stainless steel samples, affecting the concentration of the main components within each heat affected zone. The Raman spectra of the generated oxides have different intensity profiles, which suggest different oxide phases such as magnetite and maghemite. In addition, these oxides are not sensible to the laser power of the Raman system, as are the iron oxide powders reported in the literature. These experiments show that it is possible to generate periodic patterns of various iron oxide zones by laser irradiation, of stainless steel at ambient conditions, and that Raman spectroscopy is a useful punctual technique for the analysis and inspection of small oxide areas. PMID:24699286

  1. Infrared nanosecond pulsed laser irradiation of stainless steel: Micro iron-oxide zones generation

    NASA Astrophysics Data System (ADS)

    Ortiz-Morales, M.; Frausto-Reyes, C.; Soto-Bernal, J. J.; Acosta-Ortiz, S. E.; Gonzalez-Mota, R.; Rosales-Candelas, I.

    2014-07-01

    Nanosecond-pulsed, infrared (1064 nm) laser irradiation was used to create periodic metal oxide coatings on the surface of two samples of commercial stainless steel at ambient conditions. A pattern of four different metal oxide zones was created using a galvanometer scanning head and a focused laser beam over each sample. This pattern is related to traverse direction of the laser beam scanning. Energy-dispersive X-ray spectroscopy (EDS) was used to find the elemental composition and Raman spectroscopy to characterize each oxide zone. Pulsed laser irradiation modified the composition of the stainless steel samples, affecting the concentration of the main components within each heat affected zone. The Raman spectra of the generated oxides have different intensity profiles, which suggest different oxide phases such as magnetite and maghemite. In addition, these oxides are not sensible to the laser power of the Raman system, as are the iron oxide powders reported in the literature. These experiments show that it is possible to generate periodic patterns of various iron oxide zones by laser irradiation, of stainless steel at ambient conditions, and that Raman spectroscopy is a useful punctual technique for the analysis and inspection of small oxide areas.

  2. Intense excitation source of blue-green laser

    NASA Astrophysics Data System (ADS)

    Han, Kwang S.

    1986-10-01

    An intense and efficient source for blue green laser useful for the space-based satellite laser applications, underwater strategic communication, and measurement of ocean bottom profile is being developed. The source in use, the hypocycloidal pinch plasma (HCP), and the dense plasma focus (DPF) can produce intense uv photons (200 to 400nm) which match the absorption spectra of both near UV and blue green dye lasers (300 to 400nm). As a result of optimization of the DPF light at 355nm, the blue green dye (LD490) laser output exceeding 4mJ was obtained at the best cavity tunning of the laser system. With the HCP pumped system a significant enhancement of the blue green laser outputs with dye LD490 and coumarin 503 has been achieved through the spectrum conversion of the pumping light by mixing a converter dye BBQ. The maximum increase of laser output with the dye mixture of LD490+BBQ and coumarin 503+BBQ was greater than 80%. In addition, the untunned near UV lasers were also obtained. The near UV laser output energy of P-terphenyl dye was 0.5mJ at lambda sub C=337nm with the bandwidth of 3n m for the pulse duration of 0.2us. Another near UV laser output energy obtained with BBQ dye was 25 mJ at lambda sub C=383nm with the bandwidth of 3nm for the pulse duration of 0.2us. Another near UV laser output energy obtained with BBQ dye was 25 mJ at lambda sub C=383nm with the bandwidth of 3nm for the pulse duration of 0.2microsec.

  3. Intense excitation source of blue-green laser

    NASA Astrophysics Data System (ADS)

    Han, K. S.

    1985-10-01

    An intense and efficient excitation source for blue-green lasers useful for the space-based satellite laser applications, underwater strategic communication, and measurement of ocean bottom profile is being developed. The source in use, hypocycloidal pinch plasma (HCP), and a newly designed dense-plasma focus (DPF) can produce intense UV photons (200 to 300 nm) which match the absorption spectra of both near UV and blue green dye lasers (300 to 400 nm). During the current project period, the successful enhancement of blue-green laser output of both Coumarin 503 and LD490 dye through the spectral conversion of the HCP pumping light has been achieved with a converter dye BBQ. The factor of enhancement in the blue-green laser output energy of both Coumarin 503 and LD490 is almost 73%. This enhancement will definitely be helpful in achieving the direct high power blue-green laser (> 1 MW) with the existing blue green dye laser. On the other hand the dense-plasma focus (DPF) with new optical coupling has been designed and constructed. For the optimization of the DPF device as the UV pumping light source, the velocity of current sheath and the formation of plasma focus have been measured as function of argon or argon-deuterium fill gas pressure. Finally, the blue-green dye laser (LD490) has been pumped with the DPF device for preliminary tests. Experimental results with the DPF device show that the velocity of the current sheath follows the inverse relation of sq st. of pressure as expected. The blue-green dye (LD490) laser output exceeded 3.1 m at the best cavity tuning of laser system. This corresponds to 3J/1 cu cm laser energy extraction.

  4. Photogenerated charges and surface potential variations investigated on single Si nanorods by electrostatic force microscopy combined with laser irradiation

    PubMed Central

    2014-01-01

    Photogenerated charging properties of single Si nanorods (Si NRs) are investigated by electrostatic force microscopy (EFM) combined with laser irradiation. Under laser irradiation, Si NRs are positively charged. The amount of the charges trapped in single NRs as well as the contact potential difference between the tip and NRs' surface is achieved from an analytical fitting of the phase shift - voltage curve. Both of them significantly vary with the laser intensity and the NR's size and construction. The photogenerated charging and decharging rates are obtained at a timescale of seconds or slower, indicating that the Si NRs are promising candidates in photovoltaic applications. PMID:24940176

  5. Communication: Mode bifurcation of droplet motion under stationary laser irradiation

    SciTech Connect

    Takabatake, Fumi; Yoshikawa, Kenichi; Ichikawa, Masatoshi

    2014-08-07

    The self-propelled motion of a mm-sized oil droplet floating on water, induced by a local temperature gradient generated by CW laser irradiation is reported. The circular droplet exhibits two types of regular periodic motion, reciprocal and circular, around the laser spot under suitable laser power. With an increase in laser power, a mode bifurcation from rectilinear reciprocal motion to circular motion is caused. The essential aspects of this mode bifurcation are discussed in terms of spontaneous symmetry-breaking under temperature-induced interfacial instability, and are theoretically reproduced with simple coupled differential equations.

  6. Relativistic intensity laser interactions with low-density plasmas

    NASA Astrophysics Data System (ADS)

    Willingale, L.; Nilson, P. M.; Zulick, C.; Chen, H.; Craxton, R. S.; Cobble, J.; Maksimchuk, A.; Norreys, P. A.; Sangster, T. C.; Scott, R. H. H.; Stoeckl, C.

    2016-03-01

    We perform relativistic-intensity laser experiments using the Omega EP laser to investigate channeling phenomena and particle acceleration in underdense plasmas. A fundamental understanding of these processes is of importance to the hole-boring fast ignition scheme for inertial confinement fusion. Proton probing was used to image the electromagnetic fields formed as the Omega EP laser pulse generated a channel through underdense plasma. Filamentation of the channel was observed, followed by self-correction into a single channel. The channel radius as a function of time was found to be in reasonable agreement with momentum- conserving snowplough models.

  7. Propagation of intense laser pulses in strongly magnetized plasmas

    SciTech Connect

    Yang, X. H. Ge, Z. Y.; Xu, B. B.; Zhuo, H. B.; Ma, Y. Y.; Shao, F. Q.; Yu, W.; Xu, H.; Yu, M. Y.; Borghesi, M.

    2015-06-01

    Propagation of intense circularly polarized laser pulses in strongly magnetized inhomogeneous plasmas is investigated. It is shown that a left-hand circularly polarized laser pulse propagating up the density gradient of the plasma along the magnetic field is reflected at the left-cutoff density. However, a right-hand circularly polarized laser can penetrate up the density gradient deep into the plasma without cutoff or resonance and turbulently heat the electrons trapped in its wake. Results from particle-in-cell simulations are in good agreement with that from the theory.

  8. Particle acceleration studies with intense lasers and advanced light sources

    NASA Astrophysics Data System (ADS)

    Murphy, C. D.; Gray, R. J.; MacLellan, D. A.; Rusby, D.; McKenna, P.; Ridgers, C. P.; Booth, N.; Robinson, A. P. L.; Wilson, L.; Green, J. S.

    2013-10-01

    The interaction of lasers with matter is a subject which has progressed rapidly over the last two decades as higher intensity lasers are found to have possible applications in inertial fusion, laboratory astrophysics and ion acceleration for oncology or ultrafast proton probing. All of these applications require a good understanding of laser-electron coupling and fast electron transport in solid targets which has proven difficult to diagnose. Here we present data from an experiment carried out on the Astra Gemini laser system at STFC-Rutherford Appleton Laboratory, where novel targets and diagnostics illuminate the complex processes at play. An outline of how x-ray free electron lasers may further expand our understanding of such processes will also be described.

  9. Laser versus intense pulsed light: Competing technologies in dermatology.

    PubMed

    Ross, E Victor

    2006-04-01

    Lasers have been competing with non-laser intense pulsed light (IPL) sources in the cosmetic arena over the past 10 years. Initially IPLs were somewhat cumbersome and accepted by a minority of "serious" practitioners. Recently, however, the popularity of full-face visible light skin rejuvenation, enhanced engineering of IPLs, and favorable cost versus many lasers, have lead to a proliferation of IPL devices. No longer a stepchild in the rejuvenation market, IPLs may overtake lasers as the devices of choice among most physicians. We review the pros and cons of lasers and IPLs within the context of design, cost, and other practical concerns for a typical office-based practice. PMID:16596659

  10. Effects of a Low-Intensity Laser on Dental Implant Osseointegration: Removal Torque and Resonance Frequency Analysis in Rabbits.

    PubMed

    Blay, Alberto; Blay, Claudia C; Tunchel, Samy; Gehrke, Sergio Alexandre; Shibli, Jamil Awad; Groth, Eduardo B; Zezell, Denise M

    2016-08-01

    The objective of this study was to investigate how a low-intensity laser affects the stability and reverse torque resistance of dental implants installed in the tibia of rabbits. Thirty rabbits received 60 dental implants with the same design and surface treatment, one in each proximal metaphysis of the tibia. Three groups were prepared (n = 10 animals each): conventional osseointegration without treatment (control group), surgical sites irradiated with a laser beam emitted in the visible range of 680 nm (Lg1 group), surgical sites irradiated with a laser beam with a wavelength in the infrared range of 830 nm (Lg2 group). Ten irradiation sessions were performed 48 hours apart; the first session was during the immediate postoperative period. Irradiation energy density was 4 J/cm(2) per point in 2 points on each side of the tibias. The resonance frequency and removal torque values were measured at 2 time points after the implantations (3 and 6 weeks). Both laser groups (Lg1 and Lg2) presented a significant difference between resonance frequency analysis values at the baseline and the values obtained after 3 and 6 weeks (P > .05). Although the removal torque values of all groups increased after 6 weeks (P < .05), both laser groups presented greater mean values than those of the control group (P < .01). Photobiomodulation using laser irradiation with wavelengths of 680 and 830 nm had a better degree of bone integration than the control group after 6 weeks of observation time. PMID:26652735

  11. Investigating the QED vacuum with ultra-intense laser fields

    NASA Astrophysics Data System (ADS)

    King, B.; Di Piazza, A.

    2014-05-01

    In view of the increasingly stronger available laser fields it is becoming feasible to employ them to probe the nonlinear dielectric properties of the vacuum as predicted by quantum electrodynamics (QED) and to test QED in the presence of intense laser beams. First, we discuss vacuum-polarization effects that arise in the collision of a high-energy proton beam with a strong laser field. In addition, we investigate the process of light-by-light diffraction mediated by the virtual electron-positrons of the vacuum. A strong laser beam "diffracts" a probe laser field due to vacuum polarization effects, and changes its polarization. This change of the polarization is shown to be in principle measurable. Also, the possibility of generating harmonics by exploiting vacuum-polarization effects in the collision in vacuum of two ultra-strong laser beams is discussed. Moreover, when two strong parallel laser beams collide with a probe electromagnetic field, each photon of the probe may interact through the "polarized" quantum vacuum with the photons of the other two fields. Analogously to "ordinary" double-slit set-ups involving matter, the vacuum-scattered probe photons produce a diffraction pattern, which is the envisaged observable to measure the quantum interaction between the probe and strong field photons. We have shown that the diffraction pattern becomes visible in a few operating hours, if the strong fields have an intensity exceeding 1024W/cm2.

  12. Low-intensity infrared laser effects on zymosan-induced articular inflammatory response

    NASA Astrophysics Data System (ADS)

    Januária dos Anjos, Lúcia Mara; da Fonseca, Adenilson d. S.; Gameiro, Jacy; de Paoli, Flávia

    2015-03-01

    Low-level therapy laser is a phototherapy treatment that involves the application of low power light in the red or infrared wavelengths in various diseases such as arthritis. In this work, we investigated whether low-intensity infrared laser therapy could cause death by caspase-6 apoptosis or DNA damage pathways in cartilage cells after zymosaninduced articular inflammatory process. Inflammatory process was induced in C57BL/6 mouse by intra-articular injection of zymosan into rear tibio-tarsal joints. Thirty animals were divided in five groups: (I) control, (II) laser, (III) zymosan-induced, (IV) zymosan-induced + laser and (V). Laser exposure was performed after zymosan administration with low-intensity infrared laser (830 nm), power 10 mW, fluence 3.0 J/cm2 at continuous mode emission, in five doses. Twenty-four hours after last irradiation, the animals were sacrificed and the right joints fixed and demineralized. Morphological analysis was observed by hematoxylin and eosin stain, pro-apoptotic (caspase-6) was analyzed by immunocytochemistry and DNA fragmentation was performed by TUNEL assay in articular cartilage cells. Inflammatory process was observed in connective tissue near to articular cartilage, in IV and V groups, indicating zymosan effect. This process was decreased in both groups after laser treatment and dexamethasone. Although groups III and IV presented higher caspase-6 and DNA fragmentation percentages, statistical differences were not observed when compared to groups I and II. Our results suggest that therapies based on low-intensity infrared lasers could reduce inflammatory process and could not cause death by caspase-6 apoptosis or DNA damage pathways in cartilage cells after zymosan-induced articular inflammatory process.

  13. Singlet Oxygen Generation by Laser Irradiation of Gold Nanoparticles

    PubMed Central

    2016-01-01

    The formation of singlet oxygen by irradiation of gold nanoparticles in their plasmon resonance band with continuous or pulsed laser light has been investigated. Citrate-stabilized nanoparticles were found to facilitate the photogeneration of singlet oxygen, albeit with low quantum yield. The reaction caused by pulsed laser irradiation makes use of the equilibrated hot electrons that can reach temperatures of several thousand degrees during the laser pulse. Although less efficient, continuous irradiation, which acts via the short-lived directly excited primary “hot” electrons only, can produce enough singlet oxygen for photodynamic cancer therapy and has significant advantages for practical applications. However, careful design of the nanoparticles is needed, since even a moderately thick capping layer can completely inhibit singlet oxygen formation. Moreover, the efficiency of the process also depends on the nanoparticle size. PMID:27239247

  14. Atomic electron correlations in intense laser fields

    SciTech Connect

    DiMauro, L.F.; Sheehy, B.; Walker, B.; Agostini, P.A.; Kulander, K.C.

    1998-11-01

    This talk examines two distinct cases in strong optical fields where electron correlation plays an important role in the dynamics. In the first example, strong coupling in a two-electron-like system is manifested as an intensity-dependent splitting in the ionized electron energy distribution. This two-electron phenomenon (dubbed continuum-continuum Autler-Townes effect) is analogous to a strongly coupled two-level, one-electron atom but raises some intriguing questions regarding the exact nature of electron-electron correlation. The second case examines the evidence for two-electron ionization in the strong-field tunneling limit. Although their ability to describe the one-electron dynamics has obtained a quantitative level of understanding, a description of the two (multiple) electron ionization remains unclear.

  15. Atomic electron correlations in intense laser fields

    SciTech Connect

    DiMauro, L.F.; Sheehy, B.; Walker, B. Agostini, P.A. Kulander, K.C.

    1999-06-01

    This talk examines two distinct cases in strong optical fields where electron correlation plays an important role in the dynamics. In the first example, strong coupling in a two-electron-like system is manifested as an intensity-dependent splitting in the ionized electron energy distribution. This two-electron phenomenon (dubbed continuum-continuum Autler-Townes effect) is analogous to a strongly coupled two-level, one-electron atom but raises some intriguing questions regarding the exact nature of electron-electron correlation. The second case examines the evidence for two-electron ionization in the strong-field tunneling limit. Although our ability to describe the one-electron dynamics has obtained a quantitative level of understanding, a description of the two (multiple) electron ionization remains unclear. {copyright} {ital 1999 American Institute of Physics.}

  16. Atomic electron correlations in intense laser fields

    SciTech Connect

    DiMauro, L. F.; Sheehy, B.; Walker, B.; Agostini, P. A.; Kulander, K. C.

    1999-06-11

    This talk examines two distinct cases in strong optical fields where electron correlation plays an important role in the dynamics. In the first example, strong coupling in a two-electron-like system is manifested as an intensity-dependent splitting in the ionized electron energy distribution. This two-electron phenomenon (dubbed continuum-continuum Autler-Townes effect) is analogous to a strongly coupled two-level, one-electron atom but raises some intriguing questions regarding the exact nature of electron-electron correlation. The second case examines the evidence for two-electron ionization in the strong-field tunneling limit. Although our ability to describe the one-electron dynamics has obtained a quantitative level of understanding, a description of the two (multiple) electron ionization remains unclear.

  17. Atomic electron correlations in intense laser fields

    SciTech Connect

    Agostini, P A; DiMauro, L F; Kulander, K; Sheehy, B; Walker, B

    1998-09-03

    Abstract. This talk examines two distinct cases in strong opbical fields where electron correlation plays an important role in the dynamic.s. In the first. example, strong coupling in a two-electron-like system is manifested as an intensity-dependent splitting in the ionized electron energy distribution. This two-electron phenomenon (dubbed continuum-continuum Autler-Townes effect) is analogous to a strongly coupled two- level, one-electron atom but raises some intriguing questions regarding the exact nature of electron-electron correlation. The second case examines the evidence for two-electron ionization in the strong-field tunneling limit. Although our ability to describe the one- electron dynamics has obtained a quantitative level of understanding, a description of the two (multiple) electron ionization remains unc

  18. Damage thresholds in laser-irradiated optical materials

    NASA Astrophysics Data System (ADS)

    Guignard, Franck; Autric, Michel L.; Baudinaud, Vincent

    1997-05-01

    An experimental study on the damage induced by laser irradiation on different materials, borosilicate glass, fused silicate, molded and stretched polymethylmethacrylate (PMMA), has been performed. The irradiation source is a 1KL pulsed cold cathode electron gun preionized TEA CO2 laser. Damage mechanisms are controlled by the in-depth absorption of the 10.6 micrometers radiation according to the Beer-Lambert law. PMMA is damaged following a boiling process. Stretched PMMA is fractured first, releasing stresses, then boiled like molded PMMA at a higher energy. BK7 crazed after the irradiation due to thermomechanical stresses, silicate melt and vaporized. Optical damages have been characterized by measuring the contrast transfer function through the irradiated samples.

  19. Submicro foaming in biopolymers by UV pulsed laser irradiation

    NASA Astrophysics Data System (ADS)

    Oujja, Mohamed; Rebollar, Esther; Gaspard, Solenne; Abrusci, Concepción; Catalina, Fernando; Lazare, Sylvain; Castillejo, Marta

    2006-05-01

    Microstructuring of polymers and biopolymers is of application in medical technology and biotechnology. Using different fabrication techniques three-dimensionally shaped and micro structured constructs can be developed for drug release and tissue engineering. As an alternative method, laser microstructuring offers a series of advantages including high resolution capability, low heat deposition in the substrate and high level of flexibility. In this work we present evidence of laser microfoam formation in collagen and gelatine by nanosecond pulsed laser irradiation in the UV at 248 and 266 nm. Irradiation at 355 nm produces melting followed by resolidification of the substrate, whereas irradiation at 532 and 1064 nm induces the formation of craters of irregular contours. Single pulse irradiation of a collagen film with an homogenized KrF microbeam yields a 20 μm thick expanded layer, which displays the interesting features of a nanofibrous 3-dimensional network with open cells. In gelatine, irradiation at 248 and 266 nm produces similar morphological modifications. The effect of the structural properties of the substrate on the laser induced microfoam is studied by comparing gelatines differing in gel strength (Bloom values 225 and 75) and in crosslinking degree. While results are discussed on the basis of thermal and photomechanical mechanisms and of the role played by the water content of the substrates, it is thought that such structures could have a biomimic function in future 3D cell culture devices for research.

  20. Distinct photoresponse in graphene induced by laser irradiation

    SciTech Connect

    Wang, Wen Hui; Nan, Hai Yan; Liu, Qi; Ni, Zhen Hua; Liang, Zheng; Yu, Zhi Hao; Liu, Feng Yuan; Wang, Xin Ran; Hu, Wei Da; Zhang, Wei

    2015-01-12

    The graphene-based photodetector with tunable p-p{sup +}-p junctions was fabricated through a simple laser irradiation process. Distinct photoresponse was observed at the graphene (G)-laser irradiated graphene (LIG) junction by scanning photocurrent measurements, and its magnitude can be modulated as a result of a positive correlation between the photocurrent and doping concentration in LIG region. Detailed investigation suggests that the photo-thermoelectric effect, instead of the photovoltaic effect, dominates the photocurrent generation at the G-LIG junctions. Such a simple and low-cost technique offers an alternative way for the fabrication of graphene-based optoelectronic devices.

  1. Evaluation of phase, microstructure and composition of human dentine after Er,Cr:YSGG laser irradiation.

    PubMed

    Lin, Shi; Pan, Danmei; Lin, Qi; Yin, Shungao; Chen, Dagui; Liu, Qinghua; Yu, Lili; Lin, Zhang

    2011-03-01

    This study aims to evaluate the composition, micro-structure and inorganic phase alternations of human dentine irradiated by Er,Cr:YSGG laser with water cooling spray system. X-ray diffraction (XRD) analysis indicated that the main inorganic phase of dentine before and after laser irradiation were all Hydroxyapatite (HA) structure, approximately 30 nm in size. No significant changes occurred in the average particle size after irradiation in four energy densities (6.18 J/cm2, 8.04 J/cm2, 9.89 J/cm2, 11.1 J/cm2). Atomic force microscope (AFM) phase image and the energy-dispersive spectroscope (EDS) analysis, however, demonstrated that the thermal effects of Er,Cr:YSGG laser with water-cooling spray system on the dentin surface was intense enough to induce notable decrease of the organic matter. Both scanning electron microscopy (SEM) and AFM analysis showed that the irradiated dentine presented rough surface morphology. The surface is clean and dentinal tubules are completely open. The ablation rate of both peri- and intertubular dentine increased at higher energy densities but no significant changes of gross appearance took place. Chemical analysis reveals that laser photothermal effect would decrease significantly the organic content of superficial dentinal layer. We conclude that the Er,Cr:YSGG laser, as a new type clinic laser, would not significantly influence the inorganic phase structure of the surface dentine layer, however, thermal ablation was occurred in organic component. Moreover, the rough ablated surface as well as the opened dentinal tubules induced by irradiation, might be advantageous to the infiltration of the adhesive materials, thus the adhesion of dental restoration could be enhanced. Further studies should focus on the correlation between bond strength and Er,Cr:YSGG lased dentine. PMID:21449402

  2. Dynamic optical limiting experiments on vanadium dioxide and vanadium pentoxide thin films irradiated by a laser beam

    SciTech Connect

    Wang Weiping; Luo Yongquan; Zhang Dayong; Luo Fei

    2006-05-10

    Vanadium dioxide (VO2) and vanadium pentoxide (V2O5) thin films are irradiated by a near-infrared continuous-wave laser beam and the dynamic optical limiting performance is measured. The temperature varying with time of the films induced by a laser beam is also recorded by an IR thermal sensor. Under the irradiation of a laser beam with an intensity of 255 W/cm2 and a spot diameter of 2 mm, the laser beam transmittance of the VO2 film decreases from 47% before phase transition to 28% after phase transition, and the response time is {approx}200 ms; the laser beam transmittance of the V2O5 film decreases from 51% before phase transition to 24% after phase transition, and the response time is {approx}40 ms. The optical limiting is realized by this laser heating-induced phase transition.

  3. Radiation protection for an ultra-high intensity laser.

    PubMed

    Borne, F; Delacroix, D; Gelé, J M; Massé, D; Amiranoff, F

    2002-01-01

    Radiological characterisation of an experimental chamber and other areas of an ultra-high intensity laser facility (-terawatt) revealed significant levels of X ray, gamma and neutron radiation. Different techniques were used to detect and measure this radiation: TLD. photographic film, bubble detectors and germanium spectrometry. A test series of radiological measurements was made for 150 laser shots (300 femtoseconds) with energies in the 1 to 20 J range and a target illuminance of 10(19) W.cm2. Gamma dose equivalents in the vicinity of the chamber varied between 0.7 and 73 mSv. The dose equivalent due to the neutron component was evaluated to be 1% of the gamma dose equivalent. The amount of radiation generated depends on the laser energy and the nature of the target. No activation or contamination of the chamber or target holder were observed. Ultra-high intensity lasers are being extensively developed at the present time and the investigations performed demonstrate that it is necessary to take radiological risks into consideration in the design of ultra-high intensity laser facilities and to define personnel access conditions. PMID:12212903

  4. Photochemical and thermal changes in tissue autofluorescence during excimer laser irradiation

    NASA Astrophysics Data System (ADS)

    McAuliffe, Daniel J., Sr.; Jacques, Steven L.; Hayes, Amy S.

    1990-06-01

    A striking consequence of 248-nm excimer laser irradiation of skin is a stable vivid blue fluorescence easily visualized under UVA illumination. Its spectral properties (excitation maximum at "335 nm; emission maximum at ''43O nm) are somewhat similar to those of the fluorescent pigments associated with aging of tissue and peroxidation of lipids, and the fluorescent pigments formed during exposure to high temperatures. This study explores the spectral properties, magnitude, dose response, and laser pulse intensity dependence of this phenomenon in both isolated stratum corneum and epidermal cell suspensions from human skin.

  5. [Effect of intravenous laser irradiation of blood on the homeostasis in patients with hemorrhagic pancreatitis].

    PubMed

    Dedenko, I K

    1989-08-01

    After intravenous blood exposure to low-intensity radiation of Helium-Neon laser patients with haemorrhagic pancreatitis exhibited inhibition of the blood proteolytic activity; enhancement of free-radical oxidation, kallikrein-kinin system activity, blood oxygen transport, correction of endotoxic pancreatogenic syndrome. In addition, the positive shifts were also observed in the immunological status, morphofunctional characteristics of the red blood cells and hemoglobin, hepatic and renal functions. In severe pancreatogenic endotoxicosis the highest response was achieved with combined use of hemosorption and intravenous laser irradiation. PMID:2811243

  6. Influence Of Low Intensity Laser Therapy On Diabetic Polyneuropathy

    NASA Astrophysics Data System (ADS)

    Abdel-Raoof, N. A.; Elnhas, N. G.; Elsayed, I. M.

    2011-09-01

    Diabetic peripheral neuropathy is a consequence of diabetes-mediated impairment of blood flow, and resultant hypoxia of nerves that may develop within 10 years of the onset of diabetes in 40-50% of people with type 1 or type 2 diabetes. Low Intensity Laser Therapy (LILT) has been advocated for the treatment of chronic pain disorders as blood flow is an important determinant for pain relief. Comparing the effect of Helium-Neon Laser therapy versus Infrared laser therapy on blood vessels diameter and flow as well as level of sensation for neuropathy. Twenty diabetic patients suffering from neuropathy were enrolled in the study with age 45-55 years. They were assigned randomly into two equal groups in number; Group A underwent an application of He-Neon laser while Group B underwent an application of Infrared laser. Both groups received laser for 2 months. Blood flow velocity, and blood vessel diameter were investigated by using duplex Doppler ultrasound and peripheral neuropathy parameters were investigated by Semmes-Weinstein monofilament assessment. The results revealed that He-Neon laser as well as Infrared laser groups showed significant improvement in blood flow velocity, blood vessel diameter & neuropathy tested parameters after treatment but there was no significance difference between the two types of LILT. LILT is a safe, non-invasive and drug free method for improving blood flow & sensation in patients suffering from diabetic polyneuropathy in addition to preventing one of the most threatening microvascular complications of diabetes.

  7. Ultrafast Charge Dynamics Initiated by High-Intensity, Ultrashort Laser-Matter Interaction

    SciTech Connect

    Borghesi, Marco; Romagnani, Lorenzo; Kar, Satyabrata; Cecchetti, Carlo A.; Toncian, Toma; Jung, Ralph; Osterholtz, Jens; Willi, Oswald; Antici, Patrizio; Audebert, Patrick; Brambrink, Erik; Fuchs, Julien; Ceccherini, Francesco; Macchi, Andrea; Galimberti, Marco; Gizzi, Leonida A.; Grismayer, Thomas; Mora, Patrick; Schiavi, Angelo

    2006-04-07

    The interaction of high-intensity laser pulses with matter releases instantaneously ultra-large currents of highly energetic electrons, leading to the generation of highly-transient, large-amplitude electric and magnetic fields. We report results of recent experiment in which such charge dynamics have been studied by using proton probing techniques able to provide maps of the electrostatic fields with high spatial and temporal resolution. The dynamics of ponderomotive channelling in underdense plasmas have been studied in this way, as also the processes of Debye sheath formation and MeV ion front expansion at the rear of laser-irradiated thin metallic foils. An application employing laser-driven impulsive fields for energy-selective ion beam focusing is also presented.

  8. Influence of low-intensity laser radiation on degree of oxygenation and speed microcirculation of blood

    NASA Astrophysics Data System (ADS)

    Korolevich, Alexander N.; Dubina, Natali S.; Vecherinski, Sergei I.

    2000-11-01

    The paper investigated in vivo the influence of low-intensity laser radiation (he-Ne laser with wavelength 0,63 nm) on the mean velocity of their movement. It is known that characteristic of cardiovascular diseases (CVD) are microcirculation disturbances and disorder in rheological properties of blood. Therefore these investigations were carried out on cardiac ischemia patients. The blood perfusion valve and the mean velocity were measured by the method of photon correlation spectroscopy with the use of fiber optic cables. As the radiation source, a semiconductor laser with wavelength 780 nm (0,8 mW) was used. It has been found that, between the erythrocytes and the mean velocity of their movement there is an inverse dependence on the time of irradiation of patients.

  9. Ultrafast Charge Dynamics Initiated by High-Intensity, Ultrashort Laser-Matter Interaction

    NASA Astrophysics Data System (ADS)

    Borghesi, Marco; Romagnani, Lorenzo; Kar, Satyabrata; Toncian, Toma; Antici, Patrizio; Audebert, Patrick; Brambrink, Erik; Ceccherini, Francesco; Cecchetti, Carlo A.; Fuchs, Julien; Galimberti, Marco; Gizzi, Leonida A.; Grismayer, Thomas; Jung, Ralph; Macchi, Andrea; Mora, Patrick; Osterholtz, Jens; Schiavi, Angelo; Willi, Oswald

    2006-04-01

    The interaction of high-intensity laser pulses with matter releases instantaneously ultra-large currents of highly energetic electrons, leading to the generation of highly-transient, large-amplitude electric and magnetic fields. We report results of recent experiment in which such charge dynamics have been studied by using proton probing techniques able to provide maps of the electrostatic fields with high spatial and temporal resolution. The dynamics of ponderomotive channelling in underdense plasmas have been studied in this way, as also the processes of Debye sheath formation and MeV ion front expansion at the rear of laser-irradiated thin metallic foils. An application employing laser-driven impulsive fields for energy-selective ion beam focusing is also presented.

  10. Proton acceleration with high-intensity ultrahigh-contrast laser pulses.

    PubMed

    Ceccotti, T; Lévy, A; Popescu, H; Réau, F; D'Oliveira, P; Monot, P; Geindre, J P; Lefebvre, E; Martin, Ph

    2007-11-01

    We report on simultaneous measurements of backward- and forward-accelerated protons spectra when an ultrahigh intensity (approximately 5 x 10(18) W/cm(20), ultrahigh contrast (>10(10)) laser pulse interacts with foils of thickness ranging from 0.08 to 105 microm. Under such conditions, free of preplasma originating from ionization of the laser-irradiated surface, we show that the maximum proton energies are proportional to the p component of the laser electric field only and not to the ponderomotive force and that the characteristics of the proton beams originating from both target sides are almost identical. All these points have been corroborated by extensive 1D and 2D particle-in-cell simulations showing a very good agreement with the experimental data. PMID:17995415

  11. Proton Acceleration with High-Intensity Ultrahigh-Contrast Laser Pulses

    SciTech Connect

    Ceccotti, T.; Levy, A.; Popescu, H.; Reau, F.; D'Oliveira, P.; Monot, P.; Martin, Ph.; Lefebvre, E.

    2007-11-02

    We report on simultaneous measurements of backward- and forward-accelerated protons spectra when an ultrahigh intensity ({approx}5x10{sup 18} W/cm{sup 2}), ultrahigh contrast (>10{sup 10}) laser pulse interacts with foils of thickness ranging from 0.08 to 105 {mu}m. Under such conditions, free of preplasma originating from ionization of the laser-irradiated surface, we show that the maximum proton energies are proportional to the p component of the laser electric field only and not to the ponderomotive force and that the characteristics of the proton beams originating from both target sides are almost identical. All these points have been corroborated by extensive 1D and 2D particle-in-cell simulations showing a very good agreement with the experimental data.

  12. Study of fast electron jet produced from interaction of intense laser beam with solid target at oblique incidence

    SciTech Connect

    Sanyasi Rao, Bobbili; Arora, Vipul; Anant Naik, Prasad; Dass Gupta, Parshotam

    2012-11-15

    Fast electrons generated along target normal direction from the interaction of intense ultrashort Ti:sapphire laser pulses ({lambda}{sub 0} = 800 nm) with planar copper target at 45 Degree-Sign incidence angle have been experimentally studied under different interaction conditions. Angular spread and energy spectrum of the fast electrons was measured for both p- and s-polarized laser irradiation at intensities in the range 4 Multiplication-Sign 10{sup 16}- 4 Multiplication-Sign 10{sup 17} W/cm{sup 2} (for a fixed pulse duration of 45 fs) and for pulse duration in the range 45 fs-1.2 ps (for a fixed laser fluence of 1.8 Multiplication-Sign 10{sup 4} J/cm{sup 2}). The fast electrons were observed consistently along the target normal direction over the entire range of interaction conditions in the form of a collimated jet, within a half cone angle of 20 Degree-Sign . The fast electrons have continuous energy spectrum with effective temperature 290 keV and 160 keV, respectively, for p- and s-polarized 45 fs laser pulse irradiation at intensity 4 Multiplication-Sign 10{sup 17} W/cm{sup 2}. Scaling laws for temperature of fast electrons with laser intensity and pulse duration were obtained. The experimental results have been explained on the basis of laser absorption and fast electron generation through the resonance absorption mechanism.

  13. Explosive photodissociation of methane induced by ultrafast intense laser

    SciTech Connect

    Kong Fanao; Luo Qi; Xu Huailiang; Sharifi, Mehdi; Song Di; Chin, See Leang

    2006-10-07

    A new type of molecular fragmentation induced by femtosecond intense laser at the intensity of 2x10{sup 14} W/cm{sup 2} is reported. For the parent molecule of methane, ethylene, n-butane, and 1-butene, fluorescence from H (n=3{yields}2), CH (A {sup 2}{delta}, B {sup 2}{sigma}{sup -}, and C {sup 2}{sigma}{sup +}{yields}X {sup 2}{pi}), or C{sub 2} (d {sup 3}{pi}{sub g}{yields}a {sup 3}{pi}{sub u}) is observed in the spectrum. It shows that the fragmentation is a universal property of neutral molecule in the intense laser field. Unlike breaking only one or two chemical bonds in conventional UV photodissociation, the fragmentation caused by the intense laser undergoes vigorous changes, breaking most of the bonds in the molecule, like an explosion. The fragments are neutral species and cannot be produced through Coulomb explosion of multiply charged ion. The laser power dependence of CH (A{yields}X) emission of methane on a log-log scale has a slope of 10{+-}1. The fragmentation is thus explained as multiple channel dissociation of the superexcited state of parent molecule, which is created by multiphoton excitation.

  14. Responses of astrocytes in culture after low dose laser irradiation

    SciTech Connect

    Yew, D.T.; Zheng, D.R.; Au, C.; Li, W.W. )

    1990-03-01

    The effect of Helium-Neon low dose laser on astrocytes was investigated in cultures of isolated astrocytes from albino neonatal rats. The laser appeared to inhibit the growth of astrocytes as exemplified by the smaller sizes of the cells and the decreased leucine uptake in each cell after treatment. Temporary decrease in the number of mitoses was also observed, but this trend was reversed soon after. Electron microscopic studies revealed an increase in buddings from cell bodies and processes (branches) after irradiation.

  15. Electron emission and fragmentation of molecules in intense laser fields

    NASA Astrophysics Data System (ADS)

    Ueda, K.; Prümper, G.; Hatamoto, T.; Okunishi, M.; Mathur, D.

    2007-06-01

    We have constructed an apparatus for high-resolution electron spectroscopy and electron-ion coincidence experiments on gas-phase molecules in intense laser fields. The apparatus comprises an electron time-of-flight (TOF) spectrometer and an ion TOF spectrometer with a position detector, placed on either side of an effusive molecular beam. The ionizing radiation is either the fundamental (800 nm wavelength) of a Ti:sapphire laser or frequency doubled 400-nm light, with pulse durations of ~ 150 fs and the repetition rate of 1 kHz. We have investigated the electron emission and fragmentation of linear alcohol molecules, methanol, ethanol and 1-propanol, in laser fields with peak intensities up to ~ 1×10 14 W/cm2. Details of our apparatus are described along with an overview of some recent results.

  16. The TEA CO2-Lasers with High Output Emission Intensity

    NASA Astrophysics Data System (ADS)

    Panchenko, Yu. N.; Losev, V. F.; Puchikin, А. V.; Jun, Yao

    2014-03-01

    TEA CO2-lasers generating short pulse radiation and operating in a pulse-periodic mode with the repetition rate up to 10 Hz have been developed. It is shown that the addition of nitrogen up to 8% in the mixture of molecular gases СО2:H2 = 500:50 at a total pressure of P = 0.6 bar enhances the peak emission power maintaining the temporary pulse shape. An output beam intensity of 12.3 MW/cm2 was obtained for the 30 ns pulse at a laser efficiency of 2.8%. In a compact TEA СО2-laser with an active medium volume of 6 cm3, a beam with an output intensity of 24 MW/cm2 at pulse duration of 70 ns was obtained.

  17. Comparison of hot wire/laser velocimeter turbulence intensity measurements

    NASA Technical Reports Server (NTRS)

    Meyers, J. F.; Wilkinson, S. P.

    1982-01-01

    The question of whether a random measure of particle velocities yields a good statistical estimate of the stationary condition of the turbulence flow field was investigated by comparing hot-wire and laser velocimeter turbulence intensity measurements. Great care was taken to insure that the instrument precision of both the laser velocimeter and hot wire was maximized. In this attempt to reduce the measurement uncertainties in the hot wire, direct digitization of the analog output signal was performed with point-by-point conversion to velocity through a spline fit calibration curve and the turbulence intensity function was calculated statistically. Frequent calibrations of the hot wire were performed using the laser velocimeter as the velocity standard to account for the presence of the small seed particles in the air flow and signal drift in the hot wire.

  18. Transition of proton energy scaling using an ultrathin target irradiated by linearly polarized femtosecond laser pulses.

    PubMed

    Kim, I Jong; Pae, Ki Hong; Kim, Chul Min; Kim, Hyung Taek; Sung, Jae Hee; Lee, Seong Ku; Yu, Tae Jun; Choi, Il Woo; Lee, Chang-Lyoul; Nam, Kee Hwan; Nickles, Peter V; Jeong, Tae Moon; Lee, Jongmin

    2013-10-18

    Particle acceleration using ultraintense, ultrashort laser pulses is one of the most attractive topics in relativistic laser-plasma research. We report proton and/or ion acceleration in the intensity range of 5×10(19) to 3.3×10(20) W/cm2 by irradiating linearly polarized, 30-fs laser pulses on 10-to 100-nm-thick polymer targets. The proton energy scaling with respect to the intensity and target thickness is examined, and a maximum proton energy of 45 MeV is obtained when a 10-nm-thick target is irradiated by a laser intensity of 3.3×10(20) W/cm2. The proton acceleration is explained by a hybrid acceleration mechanism including target normal sheath acceleration, radiation pressure acceleration, and Coulomb explosion assisted-free expansion. The transition of proton energy scaling from I(1/2) to I is observed as a consequence of the hybrid acceleration mechanism. The experimental results are supported by two- and three-dimensional particle-in-cell simulations. PMID:24182274

  19. Intra-pulse transition between ion acceleration mechanisms in intense laser-foil interactions

    NASA Astrophysics Data System (ADS)

    Padda, H.; King, M.; Gray, R. J.; Powell, H. W.; Gonzalez-Izquierdo, B.; Stockhausen, L. C.; Wilson, R.; Carroll, D. C.; Dance, R. J.; MacLellan, D. A.; Yuan, X. H.; Butler, N. M. H.; Capdessus, R.; Borghesi, M.; Neely, D.; McKenna, P.

    2016-06-01

    Multiple ion acceleration mechanisms can occur when an ultrathin foil is irradiated with an intense laser pulse, with the dominant mechanism changing over the course of the interaction. Measurement of the spatial-intensity distribution of the beam of energetic protons is used to investigate the transition from radiation pressure acceleration to transparency-driven processes. It is shown numerically that radiation pressure drives an increased expansion of the target ions within the spatial extent of the laser focal spot, which induces a radial deflection of relatively low energy sheath-accelerated protons to form an annular distribution. Through variation of the target foil thickness, the opening angle of the ring is shown to be correlated to the point in time transparency occurs during the interaction and is maximized when it occurs at the peak of the laser intensity profile. Corresponding experimental measurements of the ring size variation with target thickness exhibit the same trends and provide insight into the intra-pulse laser-plasma evolution.

  20. High Intensity Particle Physics at PW-class laser facilities

    NASA Astrophysics Data System (ADS)

    Bulanov, Stepan; Schroeder, Carl; Esarey, Eric; Esirkepov, Timur; Kando, Masaki; Rosanov, Nikolay; Korn, Georg; Bulanov, Sergey V.; Leemans, Wim P.

    2015-11-01

    The processes typical for high intensity particle physics, i.e., the interactions of charged particles with strong electromagnetic fields, have attracted considerable interest recently. Some of these processes, previously believed to be of theoretical interest only, are now becoming experimentally accessible. High intensity electromagnetic (EM) fields significantly modify the interactions of particles and EM fields, giving rise to the phenomena that are not encountered either in classical or perturbative quantum theory of these interactions. One of such phenomena is the radiation reaction, which radically influences the electron motion in an electromagnetic standing wave formed by two super-intense counter-propagating laser pulses. Depending on the laser intensity and wavelength, either classical or quantum mode of radiation reaction prevail, or both are strong. When radiation reaction dominates, electron motion evolves to limit cycles and strange attractors. This creates a new framework for high energy physics experiments on an interaction of energetic charged particle beams and colliding super-intense laser pulses. Work supported by U.S. DOE under Contract No. DE-AC02-05CH11231.

  1. Proton beam generation by ultra-high intensity laser-solid interaction

    NASA Astrophysics Data System (ADS)

    Manclossi, M.; Guemnie-Tafo, A.; Batani, D.; Malka, V.; Fritzler, S.; Lefebvre, E.; D'Humieres, E.

    2005-10-01

    We report on some recent experimental results on proton production from ultra-intense laser pulse interaction with thin aluminium and plastic foil targets. These results were obtained at Laboratoire d'Optique Appliquee with the 100TW 'salle jaune' laser system, delivering 35 fs laser pulses at 0.8 mu m, reaching a maximum intensity on target of a few 10(19) W/cm(2). In such extreme interaction conditions, an intense and collimated relativistic electron current is injected from the plasma created on the laser focal spot into the cold interior of the target. Its transport through dense matter, ruled by both collisions and self-induced (electro-magnetic) field effects, is the driving mechanism for proton acceleration from the rear side of thin foils: when reaching and leaving the foil rear-side, the fast electrons create a large charge separation and a huge electrostatic field with a maximum value of few TV/m, capable of accelerating protons. A parametric study as a function of the laser driver and target parameters indicates an optimal value for target thickness, which strongly depends on the laser prepulse duration. In our experiments, we did irradiate targets of various materials (CH, Al, Au) changing the prepulse duration by using fast Pockels cells in the laser chain. CR-39 nuclear track detectors with Al filters of different thickness and a Thomson parabola were used to detect proton generation. The best results were obtained for 2 mu m Al targets, leading to the generation of proton energies with energies up to 12 MeV.

  2. The thermodynamic response of soft biological tissues to pulsed ultraviolet laser irradiation.

    PubMed Central

    Venugopalan, V; Nishioka, N S; Mikić, B B

    1995-01-01

    The physical mechanisms that enable short pulses of high-intensity ultraviolet laser radiation to remove tissue, in a process known as laser ablation, remain obscure. The thermodynamic response of biological tissue to pulsed laser irradiation was investigated by measuring and subsequently analyzing the stress transients generated by pulsed argon fluorine (ArF, lambda = 193 nm) and krypton fluorine (KrF, lambda = 248 nm) excimer laser irradiation of porcine dermis using thin-film piezoelectric transducers. For radiant exposures that do not cause material removal, the stress transients are consistent with rapid thermal expansion of the tissue. At the threshold radiant exposure for ablation, the peak stress amplitude generated by 248 nm irradiation is more than an order of magnitude larger than that produced by 193 nm irradiation. For radiant exposures where material removal is achieved, the temporal structure of the stress transient indicates that the onset of material removal occurs during irradiation. In this regime, the variation of the peak compressive stress with radiant exposure is consistent with laser-induced rapid surface vaporization. For 193 nm irradiation, ionization of the ablated material occurs at even greater radiant exposures and is accompanied by a change in the variation of peak stress with radiant exposure consistent with a plasma-mediated ablation process. These results suggest that absorption of ultraviolet laser radiation by the extracellular matrix of tissue leads to decomposition of tissue on the time scale of the laser pulse. The difference in volumetric energy density at ablation threshold between the two wavelengths indicates that the larger stresses generated by 248 nm irradiation may facilitate the onset of material removal. However, once material removal is achieved, the stress measurements demonstrate that energy not directly responsible for target decomposition contributes to increasing the specific energy of the plume (and plasma

  3. Energy distribution of fast electrons accelerated by high intensity laser pulse depending on laser pulse duration

    NASA Astrophysics Data System (ADS)

    Kojima, Sadaoki; Arikawa, Yasunobu; Morace, Alessio; Hata, Masayasu; Nagatomo, Hideo; Ozaki, Tetsuo; Sakata, Shohei; Lee, Seung Ho; Matsuo, Kazuki; Farley Law, King Fai; Tosaki, Shota; Yogo, Akifumi; Johzaki, Tomoyuki; Sunahara, Atsushi; Sakagami, Hitoshi; Nakai, Mitsuo; Nishimura, Hiroaki; Shiraga, Hiroyuki; Fujioka, Shinsuke; Azechi, Hiroshi

    2016-05-01

    The dependence of high-energy electron generation on the pulse duration of a high intensity LFEX laser was experimentally investigated. The LFEX laser (λ = 1.054 and intensity = 2.5 – 3 x 1018 W/cm2) pulses were focused on a 1 mm3 gold cubic block after reducing the intensities of the foot pulse and pedestal by using a plasma mirror. The full width at half maximum (FWHM) duration of the intense laser pulse could be set to either 1.2 ps or 4 ps by temporally stacking four beams of the LFEX laser, for which the slope temperature of the high-energy electron distribution was 0.7 MeV and 1.4 MeV, respectively. The slope temperature increment cannot be explained without considering pulse duration effects on fast electron generation.

  4. Initial design of a beamline for ultra-intense laser-matter interactions at the BELLA-i PW laser user facility

    NASA Astrophysics Data System (ADS)

    Steinke, Sven; Bulanov, Stepan; Ji, Qing; Schenkel, Thomas; Esarey, Eric; Leemens, Wim

    2015-11-01

    BELLA, the Berkeley Lab laser accelerator center hosts a 1 PW Ti:sapp laser with 1 Hz repetition rate, where electron acceleration to 4.5 GeV was demonstrated recently. For electron acceleration, irradiances of up to 1019 W/cm2 are desired and these are implemented with a long focal length laser beamline and beam spots of w0 = 52 μm. Much higher irradiances of 1022 W/cm2 can be achieved when the laser beam is focus more tightly, to a spot of w0<5 μm in a shorter focal length beamline. A key requirement for many application of laser-matter interaction in this regime, such as laser-ion acceleration or the generation of relativistic surface high harmonics is the ultra-high intensity contrast of the laser pulse. We will describe our design for a short focal lengths beamline, BELLA-i, including multiple plasma mirrors for ultra-high contrast in the laser pulse. The resulting laser pulses will enable reliable access to many exciting aspects of high energy density laboratory physics and laser-matter interactions in the relativistic regime for a community of users. This work was supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.

  5. Emittance of positron beams produced in intense laser plasma interaction

    SciTech Connect

    Chen Hui; Hazi, A.; Link, A.; Anderson, S.; Gronberg, J.; Izumi, N.; Tommasini, R.; Wilks, S.; Sheppard, J. C.; Meyerhofer, D. D.; Baldis, H. A.; Marley, E.; Park, J.; Williams, G. J.; Fedosejev, R.; Kerr, S.

    2013-01-15

    The first measurement of the emittance of intense laser-produced positron beams has been made. The emittance values were derived through measurements of positron beam divergence and source size for different peak positron energies under various laser conditions. For one of these laser conditions, we used a one dimensional pepper-pot technique to refine the emittance value. The laser-produced positrons have a geometric emittance between 100 and 500 mm{center_dot}mrad, comparable to the positron sources used at existing accelerators. With 10{sup 10}-10{sup 12} positrons per bunch, this low emittance beam, which is quasi-monoenergetic in the energy range of 5-20 MeV, may be useful as an alternative positron source for future accelerators.

  6. Effect of low level laser therapy and high intensity laser therapy on endothelial cell proliferation in vitro: preliminary communication

    NASA Astrophysics Data System (ADS)

    Lukowicz, Malgorzata; Szymanska, Justyna; Goralczyk, Krzysztof; Zajac, Andrzej; Rość, Danuta

    2013-01-01

    Background: The main purpose of this study was to analyze the influence of power intensity and wavelength of Low Level Laser Therapy (LLLT) and HILT (High Intensity Laser Therapy) on endothelial cell proliferation. Material and methods: The tests were done on human umbilical vein endothelial cells (HUVEC). Cultures were exposed to laser irradiation of 660 nm and 670 nm at different dosages, power output was 10 - 40 mW as well as 820 nm with power 100 mW and 808 nm with power 1500 mW. Energy density was from 0.28 to 11,43 J/cm2. Cell proliferation of a control and tested culture was evaluated with a colorimetric device to detect live cells. The tests were repeated 8 times. Results: We observed good effects of LLLT on live isolated ECs and no effects in experiments on previous deep-frozen cultures. Also HILT stimulated the proliferation of HUVEC. Conclusion: Endothelial cells play a key role in vascular homeostasis in humans. We observed the stimulatory effect of LLLT and HILT on proliferation of HUVEC. Many factors influence the proliferation of EC, so is it necessary to continue the experiment with different doses, intensity and cell concentration.

  7. Calculations of population transfer during intense laser pulses

    SciTech Connect

    Schafer, K.J.; Kulander, K.C.

    1993-08-01

    Recent experiments by several groups have examined the question of population transfer to resonantly excited states during intense short laser pulses, in particular the amount of population that remains ``trapped`` in excited states at the end of a laser pulse. In this chapter we present calculations of population transfer and resonant ionization in xenon at both 660 and 620 nm. At the longer wavelength, the seven photon channel closes at 2.5{times}10{sup 13} W/cm{sup 2}. Pulses with peak intensities higher than this result in ``Rydberg trapping``, the resonant transfer of population to a broad range of high-lying states. The amount of population transferred depends on both the peak intensity and pulse duration. At 620 mm there are numerous possible six photon resonances to states with p or f angular momentum. We have done a large number of calculations for 40 fs pulses at different peak intensities and have examined the population transferred to these low-lying resonant states as a function of the peak laser intensity. We do not have room to comment upon the resonantly enhanced ionized electron energy spectra that we also determine in the same calculations. Our calculations involve the direct numerical integration of the time-dependent Schroedinger equation for an atom interacting with a strong laser field. The time-dependent wave function of a given valence electron is calculated on a spatial grid using a one-electron pseudo potential. This single active electron approximation (SAE) has been shown to be a good approximation for the rare gases at the intensities and wavelengths that we will consider. The SAE potential we use has an explicit angular momentum dependence which allows us to reproduce all of the excited state energies for xenon quite well.

  8. Giant irradiance spikes in laser beam propagation in volume turbulence: analysis and impact

    NASA Astrophysics Data System (ADS)

    Lachinova, Svetlana L.; Vorontsov, Mikhail A.

    2016-02-01

    In the wave-optics numerical simulations of laser beam propagation in volume atmospheric turbulence, we observe irregular appearance of giant intensity spikes with amplitudes exceeding the diffraction-limited intensity value by a factor of ten or even more. The presence of giant spikes may explain the existing significant difference between the scintillation index theoretical prediction and the results obtained in numerical simulation and experimental measurements. The giant spikes’ physics-based origin, probability of appearance, and impact on irradiance scintillation index are analyzed.

  9. Ion formation in laser-irradiated cesium vapor

    NASA Astrophysics Data System (ADS)

    Mahmoud, M. A.; Gamal, Y. E. E.; Abd El-Rahman, H. A.

    2006-11-01

    We study theoretically the formation of Cs and Cs2+ during cw laser radiation resonant with 6s-7p transition of Cs atomic vapor. This is done by numerically solving rate equations for the evolution of atomic state and electron populations. The results of calculations for the atomic and molecular ions density at different values of laser power clarified that the associative ionization and Penning ionization process play an important role for producing the Cs2+ and Cs, respectively, during the plasma formation. Also, the results showed that laser power of the order of 150 mW and 40 50 ns irradiation time are optimal in producing a fully ionized plasma.

  10. Polymer hydrophilicity and hydrophobicity induced by femtosecond laser direct irradiation

    NASA Astrophysics Data System (ADS)

    Wang, Z. K.; Zheng, H. Y.; Lim, C. P.; Lam, Y. C.

    2009-09-01

    Controlled modification of surface wettability of polymethyl methacrylate (PMMA) was achieved by irradiation of PMMA surface with femtosecond laser pulses at various laser fluences and focus distances. Fluences from 0.40 to 2.1 J/cm2 produced a hydrophobic surface and 2.1 to 52.7 J/cm2 (maximum investigated) produced a hydrophilic surface. Fluences less than 0.31 J/cm2 had no effect on the wettability of the raw PMMA. This change in wettability was caused dominantly by laser induced chemical structure modification and not by a change in surface roughness.

  11. The Effect of Intense Laser Radiation on Atomic Collisions

    NASA Astrophysics Data System (ADS)

    Young, Stephen Michael Radley

    1991-02-01

    Available from UMI in association with The British Library. Requires signed TDF. We have carried out theoretical and experimental studies into the effect of intense laser radiation on atomic collisions. The first experiment used neon. Excitation by electron impact in a gas discharge demanded a pressure of at least 0.075 Torr. Measurement of the intensity of 3^1S_0to 3^1P_1 fluorescence has been made for the case where high intensity ASE wings in the laser profile and background laser scatter are unimportant, with the laser tuned to resonance. The field intensity required to produce strong field fluorescence (exemplified by the Mollow triplet) was found to give rise to complications capable of screening the effects sought. Our theoretical model has suggested that at finite detunings, line-centre fluorescence will dominate Rayleigh scatter and omega_3 fluorescence. Our measurements provide information on the saturation of neon fluorescence but not of the variation of the intense field collision rate. Absorption of weak field 253.7 nm laser photons by ground state mercury atoms yielded a high 6 ^3P_1 population at a lower pressure of 0.02 Torr. The Mollow triplet has been observed in the self-broadened mercury system. Dressing of the upper transition (6^3P_1rightarrow 7^3S_1) by an intense laser close to 435.8 nm yielded the strong field signal. Polarisation studies were made possible by the 3-level mercury system (radiation trapping in a 2-level system would depolarise fluorescence) perturbed by argon. The studies yielded results that were explainable in terms of the selective population of Stark shifted dressed states by a detuned, weak probe field. Use has been made of the electric-dipole radiation selection rule m_{J}=0 rightarrow m_{J^' } = 0 unless J=J^' to devise a 'Stark shift collision switch'. The competition between collision and radiation induced transitions within the mercury atom has then been studied. The resonant, strong lambda 435.8 nm field was used

  12. High-order harmonics from laser-irradiated plasma surfaces

    SciTech Connect

    Teubner, U.; Gibbon, P.

    2009-04-15

    The investigation of high-order harmonic generation (HHG) of femtosecond laser pulses by means of laser-produced plasmas is surveyed. This kind of harmonic generation is an alternative to the HHG in gases and shows significantly higher conversion efficiency. Furthermore, with plasma targets there is no limitation on applicable laser intensity and thus the generated harmonics can be much more intense. In principle, harmonic light may also be generated at relativistic laser intensity, in which case their harmonic intensities may even exceed that of the focused laser pulse by many orders of magnitude. This phenomenon presents new opportunities for applications such as nonlinear optics in the extreme ultraviolet region, photoelectron spectroscopy, and opacity measurements of high-density matter with high temporal and spatial resolution. On the other hand, HHG is strongly influenced by the laser-plasma interaction itself. In particular, recent results show a strong correlation with high-energy electrons generated during the interaction process. The harmonics are a promising tool for obtaining information not only on plasma parameters such as the local electron density, but also on the presence of large electric and magnetic fields, plasma waves, and the (electron) transport inside the target. This paper reviews the theoretical and experimental progress on HHG via laser-plasma interactions and discusses the prospects for applying HHG as a short-wavelength, coherent optical tool.

  13. Measurements of forward scattered laser radiation from intense sub-ps laser interactions with underdense plasmas

    SciTech Connect

    Walton, B. R.; Mangles, S. P. D.; Najmudin, Z.; Tatarakis, M.; Wei, M. S.; Gopal, A.; Marle, C.; Dangor, A. E.; Krushelnick, K.; Fritzler, S.; Malka, V.; Clarke, R. J.; Hernandez-Gomez, C.

    2006-11-15

    Two experiments studying the interaction of high intensity laser pulses (1x10{sup 19}-5x10{sup 20} W/cm{sup 2}) with underdense plasma are compared. The experiments used lasers that differed in power and focused intensity but had similar pulse duration ({approx}1 ps). Spectroscopic measurements of the forward scattered light (sidebands) near the fundamental laser frequency produced by the self-modulation instability were performed and the energies of electrons accelerated in the interaction are measured and compared. It is found that at high intensities the sideband intensities and the electron energies were not directly correlated, implying that relativistic plasma wave generation is not the most important mechanism for electron acceleration in the ultrahigh intensity regime. Simulation results for the forward scattered spectrum agree well with experimental results.

  14. Numerical study of the ablative Richtmyer-Meshkov instability of laser-irradiated deuterium and deuterium-tritium targets

    NASA Astrophysics Data System (ADS)

    Marocchino, Alberto; Atzeni, Stefano; Schiavi, Angelo

    2010-11-01

    The Richtmyer-Meshkov instability (RMI) at the ablation front of laser-irradiated planar targets is investigated by two-dimensional numerical hydrodynamics simulations. The linear evolution of perturbations seeded either by surface roughness or target inhomogeneity is studied for perturbation wavelengths in the range 10≤λ≤400 μm and laser intensity 4×1012≤I≤4×1014 W/cm2 (with laser wavelength λlaser=0.35 μm). Thin and thick cryogenic deuterium or deuterium-tritium (DT) planar targets are considered. For targets irradiated at constant intensity, it is found that perturbations with wavelength below a given threshold perform damped oscillations, while perturbations above such a threshold are unstable and oscillate with growing amplitude. This is qualitatively in agreement with theoretical predictions by Goncharov et al. [Phys. Plasmas 13, 012702 (2006)], according to which ablation related processes stabilize perturbations with kDc≫1, where Dc is the distance between the ablation front and critical density for laser propagation. For kDc<1 a weakly growing Landau-Darrieus instability (LDI) is instead excited. The stability threshold increases substantially with laser intensity, given the dependence of Dc on laser intensity I (roughly Dc∝I, according to the present simulations). Direct-drive laser fusion targets are irradiated by time-shaped pulses, with a low intensity initial foot. In this case, perturbations with wavelengths below some threshold (about 10 μm, for typical ignition-class all-DT targets) are damped after an initial growth. In a thin target, initial perturbations, either damped or amplified by RMI and LDI, seed the subsequent Rayleigh-Taylor instability. Finally, it is shown that RMI growth of fusion targets can be reduced by using laser pulses including an initial adiabat-shaping picket (originally proposed to reduce the growth of Rayleigh-Taylor instability).

  15. The interaction of 193-nm excimer laser irradiation with single-crystal zinc oxide: Neutral atomic zinc and oxygen emission

    SciTech Connect

    Kahn, E. H.; Langford, S. C.; Dickinson, J. T.; Boatner, Lynn A

    2013-01-01

    We report mass-resolved time-of-flight measurements of neutral particles from the surface of single-crystal ZnO during pulsed 193-nm irradiation at laser fluences below the threshold for avalanche breakdown. The major species emitted are atomic Zn and O. We examine the emissions of atomic Zn as a function of laser fluence and laser exposure. Defects at the ZnO surface appear necessary for the detection of these emissions. Our results suggest that the production of defects is necessary to explain intense sustained emissions at higher fluence. Rapid, clean surface etching and high atomic zinc kinetic energies seen at higher laser fluences are also discussed.

  16. Atoms, molecules and clusters in intense laser fields

    NASA Astrophysics Data System (ADS)

    Walters, Zachary B.

    Recent advances in the technology of intense, short laser pulses have opened the possibility of investigating processes in atoms, molecules and clusters in which the normal intramolecular forces between electrons and nuclei, and between different electrons, are rivaled in strength by interactions with the driving laser, or with a cluster plasma. Experiments using rescattered electrons offer a means of probing atomic and molecular processes on ultrafast timescales. This thesis extends techniques and concepts of atomic and molecular physics to describe physics in the strong field regime. This involves investigating how electron scattering from atoms and molecules is affected by the intense and time-varying electric field of the laser, the effect of such scattering on experimental observables, and the role of intramolecular structure on strong field processes. Also investigated is the evolution of van derWaals atomic clusters when subject to intense laser pulses in the VUV regime. Here processes such as photoionization, inverse bremsstrahlung heating, and collisional ionization and recombination are affected both by the non-hydrogenic nature of the relevant atomic potentials but also by the screening of these potentials by the cluster plasma.

  17. New target for high-intensity laser-matter interaction: Gravitational flow of micrometer-sized powders

    SciTech Connect

    Servol, M.; Quere, F.; Bougeard, M.; Monot, P.; Martin, Ph.; Faenov, A.Ya; Pikuz, T.A.; Audebert, P.; Francucci, M.; Petrocelli, G.

    2005-08-15

    The design of efficient targets for high-intensity laser-matter interaction is essential to fully exploit the advantages of laser-induced photons or particles sources. We present an advantageous kind of target, consisting in a free gravitational flow of micrometer-sized powder, and describe its main technical characteristics. We demonstrate a laser-induced keV x-ray source using this target, and show that the photon flux obtained for the K{alpha} line of Si by irradiating different silica powders is comparable to the one obtained with a bulk silica target.

  18. Challenges of PIC Simulations at High Laser Intensity

    NASA Astrophysics Data System (ADS)

    Luedtke, Scott V.; Arefiev, Alexey V.; Toncian, Toma; Hegelich, Bjorn Manuel

    2015-11-01

    New lasers with very high intensity pulses (I >1022 W/cm2) are being commissioned to explore new regimes of laser-matter interactions. These lasers require accurate particle-in-cell (PIC) simulations, which may require new computational approaches to efficiently produce physically accurate results. We examine the constraints on PIC simulations at high field intensity imposed by both the particle pusher and field solver. As proposed by Arefiev, et al. (Physics of Plasmas 22, 013103 (2015)), we implement adaptive sub-cycling in the Boris pusher of the EPOCH code and demonstrate its effectiveness in efficiently reducing errors from the pusher. It is well know that the use of a finite-difference scheme also modifies the electromagnetic wave dispersion relation. We examine the effect of the resulting discrepancy in the phase velocity on electron acceleration, and demonstrate that relatively small errors in the phase velocity lead to substantial changes in the electron energy gain from the laser pulse. We discuss the corresponding conditions for the field solver. These results are relevant to direct laser acceleration and underdense ionization experiments. This work was supported by NNSA cooperative agreement DE-NA0002008, the Defense Advanced Research Projects Agency's PULSE program (12-63-PULSE-FP014) and the Air Force Office of Scientific Research (FA9550-14-1-0045).

  19. Making Relativistic Positrons Using Ultra-Intense Short Pulse Lasers

    SciTech Connect

    Chen, H; Wilks, S; Bonlie, J; Chen, C; Chen, S; Cone, K; Elberson, L; Gregori, G; Liang, E; Price, D; Van Maren, R; Meyerhofer, D D; Mithen, J; Murphy, C V; Myatt, J; Schneider, M; Shepherd, R; Stafford, D; Tommasini, R; Beiersdorfer, P

    2009-08-24

    This paper describes a new positron source produced using ultra-intense short pulse lasers. Although it has been studied in theory since as early as the 1970s, the use of lasers as a valuable new positron source was not demonstrated experimentally until recent years, when the petawatt-class short pulse lasers were developed. In 2008 and 2009, in a series of experiments performed at Lawrence Livermore National Laboratory, a large number of positrons were observed after shooting a millimeter thick solid gold target. Up to 2 x 10{sup 10} positrons per steradian ejected out the back of {approx}mm thick gold targets were detected. The targets were illuminated with short ({approx}1 ps) ultra-intense ({approx}1 x 10{sup 20} W/cm{sup 2}) laser pulses. These positrons are produced predominantly by the Bethe-Heitler process, and have an effective temperature of 2-4 MeV, with the distribution peaking at 4-7 MeV. The angular distribution of the positrons is anisotropic. For a wide range of applications, this new laser based positron source with its unique characteristics may complements the existing sources using radioactive isotopes and accelerators.

  20. Segmental irradiation of the bladder with neodymium YAG laser irradiation

    SciTech Connect

    McPhee, M.S.; Mador, D.R.; Tulip, J.; Ritchie, B.; Moore, R.; Lakey, W.H.

    1982-11-01

    The Neodymium YAG laser energy source can be readily adapted for cystoscopic use by some simple modifications of existing urologic equipment. Both the fiberoptic resectoscope and a deflecting cystourethroscope have been adapted for this purpose. Fixation of the fiber tip 1 cm. from the target and use of a divergent beam of 36 degrees allows the delivery of standardized dosage to a relatively large bladder tissue volume. Animal experiments involving 35 mongrel dogs established that repetitive overlapping doses of 200 joules ech can successfully treat a large area of bladder resulting in a full thickness bladder wall injury. This technique has been used in 4 high risk patients with infiltrating bladder cancer without adverse sequelae. The ability to reliably produce a full thickness lesion may give this modality a therapeutic advantage over conventional cautery techniques especially for the treatment of residual infiltrative carcinoma.

  1. Plasmas and Short-Pulse, High-Intensity Lasers

    NASA Astrophysics Data System (ADS)

    Clark, Thomas

    1999-11-01

    Many of the applications of short-pulse, high-intensity laser systems, including coherent UV and X-ray generation, compact particle accelerators, and non-perturbative nonlinear optics as well as the study of laser-matter interaction physics, require large intensity-interaction length products. In recent years, plasma structures resulting from the hydrodynamic evolution of laser-produced plasma filaments have proven to be attractive media for guiding pulses with peak powers approaching the terawatt level over lengths many times the vacuum Rayleigh range. The hydrodynamics of plasma waveguides have been characterized using time- and space-resolved interferometry measurements of electron density profiles. The laser-driven ionization and heating phase of the plasma filament creation is followed by hot electron driven plasma expansion. Density profiles suitable for optical guiding develop within the first few hundred picoseconds after plasma creation, during which rapid cooling occurs. At longer times the plasma expansion closely follows that of a cylindrical blast wave, with further cooling due to expansion work. The observed guided intensity profiles of end-coupled and tunnel-coupled pulses compare favorably with calculations of the quasi-bound waveguide modes based on the measured electron density profiles. Time- and space-resolved electron density measurements of a laser-driven concentric implosion were also performed. The implosion is the result of the interaction of a second laser pulse with an existing plasma waveguide. The two-pulse absorption and ionization significantly exceed that due to a single pulse of the same total energy. The author would like to acknowledge the significant contributions of Prof. Howard M. Milchberg to the work being presented.

  2. Er:YAG laser irradiation on dentin: FT-Raman and SEM studies

    NASA Astrophysics Data System (ADS)

    Soares, Luís Eduardo Silva; Bitar, Renata Andrade; Brugnera, Aldo; Zanin, Fatima A. A.; Resende, Erick B. P. S.; Jara, Walter A. A.; Martin, Airton A.

    2007-02-01

    This study evaluated the molecular and morphological changes on dentin elements after the Er:YAG laser irradiation. Six human third molars were selected and the occlusal one-third of the crown was removed. The dentin surface was schematically divided into areas corresponding to four surface treatments groups: Control (Group C): 37% phosphoric acid etching; Group I: Er:YAG laser 80mJ; Group II: Er:YAG laser 120mJ; Group III: Er:YAG laser 180mJ. The characterization was performed by Scanning Electron Microscopy (SEM) and Fourier-Transformed Raman Spectroscopy (FT-Raman) before and after the treatments. A reduction of the relative intensity for the spectra was observed in the Group II and III samples. The SEM photomicrographies revealed open dentin tubules in the control group specimens. The groups I, II and III presented partially open dentin tubules. SEM images showed that the laser-irradiated dentin surface was not favorable to the diffusion of monomers. The chemical information obtained by Raman spectroscopy showed that higher laser energies (180 mJ) affected more the phosphate, carbonate and the organic components of dentin.

  3. Analgesic effect of high intensity laser therapy in knee osteoarthritis.

    PubMed

    Stiglić-Rogoznica, Nives; Stamenković, Doris; Frlan-Vrgoc, Ljubinka; Avancini-Dobrović, Viviana; Vrbanić, Tea Schnurrer-Luke

    2011-09-01

    Knee osteoarthritis (KOA), the most common type of osteoarthritis (OA), is associated with pain and inflammation of the joint capsule, impaired muscular stabilization, reduced range of motion and functional disability. High-intensity laser therapy (HILT) involves higher-intensity laser radiation and causes minor and slow light absorption by chromophores. Light stimulation of the deep structures, due to high intensity laser therapy, activates cell metabolism through photochemical effect. The transmissions of pain stimulus are slowed down and result in a quick achievement of pain relief. The aim of our research was to investigate the prompt analgesic effect of HILT on patients with KOA. Knee radiographs were performed on all patients and consequently graded using the Kellgren-Lawrence grading scale (K/L). A group of 96 patients (75 female, 21 male, mean age 59.2) with K/L 2 and 3 were submitted to HILT therapy. Pain intensity was evaluated with visual analogue scale (VAS) before and after the treatment. HILT consisted in one daily application, over a period of ten days, using protocol wavelength, frequency and duration. The results showed statistically significant decrease in VAS after the treatment (p < 0.001). Considering these results, HILT enables prompt analgesic effects in KOA treatment. Therefore HILT is a reliable option in KOA physical therapy. PMID:22220431

  4. Bactericidal effect of Nd:YAG laser irradiation in endodontics

    NASA Astrophysics Data System (ADS)

    Aun, Carlos E.; Barberini, Alexandre F.; Camargo, Selma C. C.; Silva Kfouri, Luciana; Lorenzetti Simionato, Maria R.

    1999-05-01

    The success of endodontic therapy is based on the elimination of bacterial colonization from the endodontic system and periapical tissues. Recent studies have been showing the bactericidal effect of laser in root canal treatment. The propose of the study is to evaluate the effect of Nd:YAG laser irradiation in contaminated root canal treatment. The propose of the study is to evaluate the effect of Nd:YAG laser irradiation in contaminated root canals from upper central incisor. For the experiment 12 teeth were selected, respect at the apical third, sterilized, and 10 μm Streptococcus sanguis liquid culture were inoculated in the root canals. The laser test groups were irradiated with Nd:YAG laser at standard setting of 15Hz, 100mj and 1,5 W for 10, 20 and 30 seconds each in slow helicoidal movements from the apex to the top using a 300 micrometers fiber. After the procedure the specimens were placed in Tryptic Soy Agar, the number of colony forming units was evaluated. The experiment showed a significant reduction on viability of Streptococcus sanguis at the respective time of 20 and 30 seconds.

  5. Functional assessment of high-level laser irradiation. Annual progress report, 1 August 1983-31 December 1984

    SciTech Connect

    Robbins, D.O.

    1985-01-01

    High-energy, Q-switched pulses from a laser are known to produce punctate lesions on the retina. The structural alterations often extend well beyond the primary area of exposure. This report examines the changes in visual sensitivity following single pulses of 532 nm light several orders of magnitude above the ED 50 level. Both temporary and long-term changes in spectral acuity and contrast sensitivity indicate the functional consequences of intense laser irradiation of minute areas of the central fovea.

  6. Acceleration of electrons by a tightly focused intense laser beam.

    PubMed

    Li, Jian-Xing; Zang, Wei-Ping; Li, Ya-Dong; Tian, Jian-Guo

    2009-07-01

    The recent proposal to use Weinger transformation field (WTF) [Opt. Express 17, 4959-4969 (2009)] for describing tightly focused laser beams is investigated here in detail. In order to validate the accuracy of WTF, we derive the numerical field (NF) from the plane wave spectrum method. WTF is compared with NF and Lax series field (LSF). Results show that LSF is accurate close to the beam axis and divergent far from the beam axis, and WTF is always accurate. Moreover, electron dynamics in a tightly focused intense laser beam are simulated by LSF, WTF and NF, respectively. The results obtained by WTF are shown to be accurate. PMID:19582099

  7. Relativistic Positron Creation Using Ultra-Intense Short Pulse Lasers

    SciTech Connect

    Chen, H; Wilks, S; Bonlie, J; Liang, E; Myatt, J; Price, D; Meyerhofer, D; Beiersdorfer, P

    2008-08-25

    We measure up to 2 x 10{sup 10} positrons per steradian ejected out the back of {approx}mm thick gold targets when illuminated with short ({approx} 1 ps) ultra-intense ({approx} 1 x 10{sup 20} W/cm{sup 2}) laser pulses. Positrons produced predominately by the Bethe-Heitler process and have an effective temperature of 2-4 MeV, with the distribution peaking at 4-7 MeV. The angular distribution of the positrons is anisotropic. The measurements indicate the laser produced, relativistic positron densities ({approx} 10{sup 16} positrons/cm{sup 3}) are the highest ever created in the laboratory.

  8. Nonlinear properties of relativistically intense laser in plasmas

    SciTech Connect

    Qiao Bin; Lai, C. H.; Zhou, C. T.; He, X. T.; Wang, X. G.; Yu, M. Y.

    2007-11-15

    Nonlinear characteristics including spatial chaos and patterns associated with relativistically intense laser-plasma interaction are studied theoretically and numerically using a model relativistic nonlinear Schroedinger equation. It is shown that in the phase space irregular homoclinic orbit crossings exist. The latter are verified and investigated numerically. The spatial chaos and complex patterns of the laser wave field can be attributed to the relativistic electron mass variation as well as the ponderomotive-force driven electron-density modulation. The formation of complex patterns results from stochastic partition of energy in the Fourier modes.

  9. Thermodynamic response of soft biological tissues to pulsed infrared-laser irradiation.

    PubMed Central

    Venugopalan, V; Nishioka, N S; Mikić, B B

    1996-01-01

    The physical mechanisms that achieve tissue removal through the delivery of short pulses of high-intensity infrared laser radiation, in a process known as laser ablation, remain obscure. The thermodynamic response of biological tissue to pulsed infrared laser irradiation was investigated by measuring and analyzing the stress transients generated by Q-sw Er:YSGG (lambda = 2.79 microns) and TEA CO2 (lambda = 10.6 microns) laser irradiation of porcine dermis using thin-film piezoelectric transducers. For radiant exposures that do not produce material removal, the stress transients are consistent with thermal expansion of the tissue samples. The temporal structure of the stress transients generated at the threshold radiant exposure for ablation indicates that the onset of material removal is delayed with respect to irradiation. Once material removal is achieved, the magnitude of the peak compressive stress and its variation with radiant exposure are consistent with a model that considers this process as an explosive event occurring after the laser pulse. This mechanism is different from ArF- and KrF-excimer laser ablation where absorption of ultraviolet radiation by the collagenous tissue matrix leads to tissue decomposition during irradiation and results in material removal via rapid surface vaporization. It appears that under the conditions examined in this study, explosive boiling of tissue water is the process that mediates the ablation event. This study provides evidence that the dynamics and mechanism of tissue ablation processes can be altered by targeting tissue water rather than the tissue structural matrix. Images FIGURE 6 PMID:8744336

  10. Compact energy selector for use with intense, short-pulse laser produced proton beams

    NASA Astrophysics Data System (ADS)

    Hazi, Andrew; Chen, Hui; Perez, Frederic; Marley, Edward; Park, Jaebum; Williams, Jackson; Vassura, Laura; Fuchs, Julien; Chen, Sophia; Shepherd, Ronnie

    2012-10-01

    Irradiation of thin solid targets with short, intense laser pulses produces energetic charged particles. The proton and ion beams generated from such laser-plasma interactions have several attractive features, but usually exhibit a broad energy distribution extending up to tens of MeV. However for some applications, such as energy-loss measurements in plasmas or injection into high-energy accelerators, quasi-mono energetic beams are preferred [1]. We have designed, built and tested a small (9 x 7 x 5 cm^3) energy selector for use with laser-produced proton beams in beam-plasma interaction experiments that utilize multiple laser beams. The device uses permanent magnets in a dipole configuration, with a fixed entrance aperture and an adjustable exit slit to select a narrow portion of the broad energy distribution in the beam. The energy selector was tested in a recent experiment at the Titan laser at Livermore. Sample data from the experiment and simulations of the device's characteristics will be presented. [4pt] [1] T. Toncian, et al., ``Ultrafast Laser--Driven Microlens to Focus and Energy-Select Mega--Electron Volt Protons,'' Science, 312, 410 (2006).

  11. Effects of CO/sub 2/ laser irradiation on gingiva

    SciTech Connect

    Rossmann, J.A.; Gottlieb, S.; Koudelka, B.M.; McQuade, M.J.

    1987-06-01

    A CO/sub 2/ laser (Coherent Medical Model 400) was used to irradiate the gingival tissue of a cynomolgous monkey to determine laser effects on the epithelium and underlying connective tissue. A focal length of 400 mm and a 10-watt power setting at 0.2- and 0.5-second exposure was used. Biopsy results indicated that a 0.2-second duration of CO/sub 2/ laser irradiation was inadequate to completely de-epithelialize the gingival tissue. A 0.5-second exposure exhibited complete epithelial destruction with little or no disturbance of the underlying connective tissue layer and viable connective tissue 1.0 mm below the impact site.

  12. Photoswitches operating upon ns pulsed laser irradiation

    NASA Astrophysics Data System (ADS)

    Athanassiou, A.; Lakiotaki, K.; Kalyva, M.; Georgiou, S.; Fotakis, C.

    2005-07-01

    We present a potential photoswitch, which undergoes reversible mechanical actuation induced exclusively by photons. The photoswitch is a polymer-based film doped with spiropyran photochromic molecules. It undergoes repeatable mechanical cycles controlled by ns laser pulses of specific wavelengths. The polymer matrix is mechanically activated due to particular photoisomerization processes of the incorporated photochromic molecules, resulting in its contraction and lengthening in a highly controllable manner. We present herein the way that the switching time of this novel photoswitch depends on different laser parameters such as the energy and the repetition rate.

  13. Optimum laser intensity for the production of energetic deuterium ions from laser-cluster interaction

    NASA Astrophysics Data System (ADS)

    Bang, W.; Dyer, G.; Quevedo, H. J.; Bernstein, A. C.; Gaul, E.; Rougk, J.; Aymond, F.; Donovan, M. E.; Ditmire, T.

    2013-09-01

    We measured, using Petawatt-level pulses, the average ion energy and neutron yield in high-intensity laser interactions with molecular clusters as a function of laser intensity. The interaction volume over which fusion occurred (1-10 mm3) was larger than previous investigations, owing to the high laser power. Possible effects of prepulses were examined by implementing a pair of plasma mirrors. Our results show an optimum laser intensity for the production of energetic deuterium ions both with and without the use of the plasma mirrors. We measured deuterium plasmas with 14 keV average ion energies, which produced 7.2 × 106 and 1.6 × 107 neutrons in a single shot with and without plasma mirrors, respectively. The measured neutron yields qualitatively matched the expected yields calculated using a cylindrical plasma model.

  14. Optimum laser intensity for the production of energetic deuterium ions from laser-cluster interaction

    SciTech Connect

    Bang, W.; Dyer, G.; Quevedo, H. J.; Bernstein, A. C.; Gaul, E.; Rougk, J.; Aymond, F.; Donovan, M. E.; Ditmire, T.

    2013-09-15

    We measured, using Petawatt-level pulses, the average ion energy and neutron yield in high-intensity laser interactions with molecular clusters as a function of laser intensity. The interaction volume over which fusion occurred (1–10 mm{sup 3}) was larger than previous investigations, owing to the high laser power. Possible effects of prepulses were examined by implementing a pair of plasma mirrors. Our results show an optimum laser intensity for the production of energetic deuterium ions both with and without the use of the plasma mirrors. We measured deuterium plasmas with 14 keV average ion energies, which produced 7.2 × 10{sup 6} and 1.6 × 10{sup 7} neutrons in a single shot with and without plasma mirrors, respectively. The measured neutron yields qualitatively matched the expected yields calculated using a cylindrical plasma model.

  15. Spectrum line intensity as a surrogate for solar irradiance variations.

    PubMed

    Livingston, W C; Wallace, L; White, O R

    1988-06-24

    Active Cavity Radiometer Irradiance Monitor (ACRIM) solar constant measurements from 1980 to 1986 are compared with ground-based, irradiance spectrophotometry of selected Fraunhofer lines. Both data sets were identically sampled and smoothed with an 85-day running mean, and the ACRIM total solar irradiance (S) values were corrected for sunspot blocking (S(c)). The strength of the mid-photospheric manganese 539.4-nanometer line tracks almost perfectly with ACRIM S(e), Other spectral features formed high in the photosphere and chromosphere also track well. These comparisons independently confirm the variability in the ACRIM S(e), signal, indicate that the source of irradiance is faculae, and indicate that ACRIM S(e), follows the 11-year activity cycle. PMID:17842428

  16. Generation of a quasi-monoergetic proton beam from laser-irradiated sub-micron droplets

    SciTech Connect

    Ter-Avetisyan, S.; Ramakrishna, B.; Prasad, R.; Borghesi, M.; Nickles, P. V.; Steinke, S.; Schnuerer, M.; Popov, K. I.; Ramunno, L.; Zmitrenko, N. V.; Bychenkov, V. Yu.

    2012-07-15

    Proton bursts with a narrow spectrum at an energy of (2.8 {+-} 0.3 MeV) are accelerated from sub-micron water spray droplets irradiated by high-intensity ({approx}5 Multiplication-Sign 10{sup 19} W/cm{sup 2}), high-contrast ({approx}10{sup 10}), ultra-short (40 fs) laser pulses. The acceleration is preferentially in the laser propagation direction. The explosion dynamics is governed by a residual ps-scale laser pulse pedestal which 'mildly' preheats the droplet and changes its density profile before the arrival of the high intensity laser pulse peak. As a result, the energetic electrons extracted from the modified target by the high-intensity part of the laser pulse establish an anisotropic electrostatic field which results in anisotropic Coulomb explosion and proton acceleration predominantly in the forward direction. Hydrodynamic simulations of the target pre-expansion and 3D particle-in-cell simulations of the measured energy and anisotropy of the proton emission have confirmed the proposed acceleration scenario.

  17. Self-organized, gratinglike nanostructures in polymer films with embedded metal nanoparticles induced by femtosecond laser irradiation

    NASA Astrophysics Data System (ADS)

    Loeschner, K.; Seifert, G.; Heilmann, A.

    2010-10-01

    The self-organized formation of periodic superstructures in thin plasma polymer films containing noble metal nanoparticles upon femtosecond laser irradiation has been studied in detail. By applying several hundred laser pulses on average per spot, the nanostructure of the metal layer is persistently changed into an approximate line grating with periodical changes in particle size and shape as observed by scanning and transmission electron microscopy. The formation of the structures is only possible within rather narrow ranges of laser intensity and metal content. The orientation of the lines is given by the laser polarization, while their spatial periodicity depends on laser wavelength and incidence angle. These observations give evidence that interference of incident light with light scattered into the film plane is the main mechanism controlling the nanostructure formation. We also discuss the optical spectra of the irradiated regions, in particular the observed dichroism and its relation to the prepared periodic structures.

  18. The Effect of Laser Irradiation on Adipose Derived Stem Cell Proliferation and Differentiation

    NASA Astrophysics Data System (ADS)

    Abrahamse, H.; de Villiers, J.; Mvula, B.

    2009-06-01

    There are two fundamental types of stem cells: Embryonic Stem cells and Adult Stem cells. Adult Stem cells have a more restricted potential and can usually differentiate into a few different cell types. In the body these cells facilitate the replacement or repair of damaged or diseased cells in organs. Low intensity laser irradiation was shown to increase stem cell migration and stimulate proliferation and it is thought that treatment of these cells with laser irradiation may increase the stem cell harvest and have a positive effect on the viability and proliferation. Our research is aimed at determining the effect of laser irradiation on differentiation of Adipose Derived Stem Cells (ADSCs) into different cell types using a diode laser with a wavelength of 636 nm and at 5 J/cm2. Confirmation of stem cell characteristics and well as subsequent differentiation were assessed using Western blot analysis and cellular morphology supported by fluorescent live cell imaging. Functionality of subsequent differentiated cells was confirmed by measuring adenosine triphosphate (ATP) production and cell viability.

  19. Short Pulse Laser Absorption and Energy Partition at Relativistic Laser Intensities

    SciTech Connect

    Shepherd, R; Chen, H; Ping, Y; Dyer, G; Wilks, S; Chung, H; Kemp, A; Hanson, S; Widmann, K; Fournier, K; Faenov, A; Pikuz, T; Niles, A; Beiersdorfer, P

    2007-02-27

    We have performed experiments at the COMET and Calisto short pulse laser facilities to make the first comprehensive measurements of the laser absorption and energy partition in solid targets heated with an ultrashort laser pulse focused to relativistic laser intensities (>10 10{sup 17} W/cm{sup 2}). The measurements show an exceedingly high absorption for P polarized laser-target interactions above 10{sup 19} W/cm{sup 2}. Additionally, the hot electron population is observed to markedly increase at the same intensity range. An investigation of the relaxation process was initiated u using time sing time-resolved K{sub {alpha}} spectroscopy. Measurements of the time time-resolved K{sub {alpha}} radiation suggest a 10-20 ps relativistic electron relaxation time. However modeling difficulties of these data are apparent and a more detailed investigation on this subject matter is warranted.

  20. Temporal dispersion induced commercial laser in speckle free intense imaging

    NASA Astrophysics Data System (ADS)

    Kalyan Manna, Suman; Nguyen, Giang-Nam; Le Gall, Stephen

    2016-01-01

    Coherent imaging suffers from speckle, which is basically some uncorrelated intensity distribution and bears no obvious relationship to the macroscopic properties of the object illuminated. Reducing the spatial coherence of the illuminating beam, usually improves the quality of imaging by paying the penalty for reducing intensity, and directionality as well. Here, we demonstrate an alternative way of resolving the speckle issue by inducing temporal dispersion onto the commercial He-Ne laser beam, devising with a dispersive slope available near to the edge of the 1-D organic photonic band gap Cholesteric Liquid Crystal (CLC).

  1. Simulations of Foils Irradiated by Finite Laser Spots

    NASA Astrophysics Data System (ADS)

    Phillips, Lee

    2006-10-01

    Recent proposed designs (Obenchain et al., Phys. Plasmas 13 056320 (2006)) for direct-drive ICF targets for energy applications involve high implosion velocities with lower laser energies combined with higher irradiances. The use of high irradiances increases the likelihood of deleterious laser plasma instabilities (LPI) that may lead, for example, to the generation of fast electrons. The proposed use of a 248 nm KrF laser is expected to minimize LPI, and this is being studied by experiments on NRL's NIKE laser. Here we report on simulations aimed at designing and interpreting these experiments. The 2d simulations employ a modification of the FAST code to ablate plasma from CH and DT foils using laser pulses with arbitrary spatial and temporal profiles. These include the customary hypergaussian NIKE profile, gaussian profiles, and combinations of these. The simulations model the structure of the ablating plasma and the absorption of the laser light, providing parameters for design of the experiment and indicating where the relevant LPI (two-plasmon, Raman) may be observed.

  2. Platelet derived growth factor secretion and bone healing after Er:YAG laser bone irradiation.

    PubMed

    Kesler, Gavriel; Shvero, Dana Kesler; Tov, Yariv Siman; Romanos, George

    2011-03-01

    Er:YAG laser irradiation has been reported to enhance wound healing. However, no studies have evaluated the synthesis of growth factors after laser irradiation. The present study investigated the effects of laser irradiation on the amount of secretion of platelet derived growth factor (PDGF) in the wound, clarifying the effects of the Er:YAG laser on the bone healing. Osteotomies were prepared in the tibiae of 28 rats using an Er:YAG laser (test group). Maximum power of 8 watts, energy per pulse of 700 mJ, and frequency up to 50 Hz were used. The laser was used with external water irrigation, a spot size of 2 mm, energy per pulse of 500 to 1000 mJ/pulse, and energy density of 32 J/cm(2). Twenty eight additional rats served as a control group and their osteotomies were prepared with a drill 1.3 mm in diameter at 1000 rpm, with simultaneous saline irrigation. Two rats from the tested group and 2 from the control group were sacrificed on each day following surgery (1-14 days), and the tissue specimens were prepared for histologic evaluation. Immunohistochemical staining with anti-PDGF was performed after histologic examination. The difference between the PDGF staining intensities of the 2 treatment groups was analyzed using a multivariate logistic regression test. A significant rise in PDGF staining occurred in both groups 2-3 days following surgery. However, while high PDGF counts remained for the 2-week experimental period in the laser group, PDGF levels in the control group returned to baseline levels 8 days post surgery. The 2 groups (laser and control) were found to be different throughout the experiment, and the rat type was found to be a significant predictor (P  =  .000011). The present study demonstrated that Er:YAG laser irradiation seems to stimulate the secretion of PDGF in osteotomy sites in a rat model. It is possible that the high levels of PDGF are part of the mechanism that Er:YAG irradiation enhances and improves the healing of

  3. Influence of irradiation conditions on plasma evolution in laser-surface interaction

    NASA Astrophysics Data System (ADS)

    Hermann, J.; Boulmer-Leborgne, C.; Dubreuil, B.; Mihailescu, I. N.

    1993-09-01

    The plasma plume induced by pulsed CO2 laser irradiation of a Ti target at power densities up to 4×108 W cm-2 was studied by emission spectroscopy. Time- and space-resolved measurements were performed by varying laser intensity, laser temporal pulse shape, ambient gas pressure, and the nature of the ambient gas. Experimental results are discussed by comparison with usual models. We show that shock wave and plasma propagation depend critically on the ratio Ivap/Ii, Ivap being the intensity threshold for surface vaporization and Ii the plasma ignition threshold of the ambient gas. Spectroscopic diagnostics of the helium breakdown plasma show maximum values of electron temperature and electron density in the order of kTe˜10 eV and ne=1018 cm-3, respectively. The plasma cannot be described by local thermodynamic equilibrium modeling. Nevertheless, excited metal atoms appear to be in equilibrium with electrons, hence, they can be used like a probe to measure the electron temperature. In order to get information on the role of the plasma in the laser-surface interaction, Ti surfaces were investigated by microscopy after irradiation. Thus an enhanced momentum transfer from the plasma to the target due to the recoil pressure of the breakdown plasma could be evidenced.

  4. A Review of Astrophysics Experiments on Intense Lasers

    SciTech Connect

    Remington, B.A.; Arnett, D.; Drake, R.P.; Takabe, H.

    1999-03-03

    Astrophysics traditionally has been the domain of large astronomical observatories and theorists' computers, the former producing images from deep space, and the latter constructing intricate models to explain the observations. A component often missing has been the ability to quantitatively test the theories and models in an experimental setting where the initial and final states are well characterized. In a new development, intense lasers are being used to recreate aspects of astrophysical phenomena in the laboratory, allowing the creation of experimental testbeds where theory and modeling can be quantitatively compared with data. We summarize here several areas of astrophysics: supernovae, supernova remnants, gamma-ray bursts, and giant planets. In each of these areas, experiments are under development at intense laser facilities to test and refine our understanding of these phenomena.

  5. Electron Dynamics in Intense Laser Fields: A Bohmian Mechanics Study

    NASA Astrophysics Data System (ADS)

    Jooya, Hossein Z.; Telnov, Dmitry A.; Chu, Shih-I.

    2016-05-01

    We study the electron quantum dynamics of atomic hydrogen under intense near infrared laser fields by means of the De Broglie-Bohm's framework of Bohmian mechanics. This method is used to study the mechanism of the multiple plateau generation and the cut-off extension, as the main characteristic features of high order harmonic generation spectrum. Electron multiple recollision dynamics under intense mid-infrared laser fields is also investigated. In this case, the resulting patterns in the high-order harmonic generation and the above-threshold ionization spectra are analyzed by comprehensive picture provided by Bohmian mechanics. The time evolution of individual trajectories is closely studied to address some of the major structural features of the photoelectron angular distributions. This work is partially supported by DOE.

  6. Sudden perturbation of hydrogen atoms by intense ultrashort laser pulses

    SciTech Connect

    Lugovskoy, A. V.; Bray, I.

    2005-12-15

    We study theoretically how hydrogen atoms respond to intense ultrashort laser pulses of duration {tau} shorter than the inverse of the initial-state energy {epsilon}{sub i}{sup -1}. An analytical expression for the evolution operator S is derived up to the first order of the sudden perturbation approximation. This approximation treats the laser-atom interaction beyond the dipole approximation and yields S as a series in the small parameter {epsilon}{sub i}{tau}. It is shown that the effect of realistic laser pulses on atoms begins at the first order of {epsilon}{sub i}{tau}. Transitions between atomic (nlm) states of different m become possible due to the action of the pulse's magnetic field. Transitions between states of same m and arbitrary l become possible if the static Coulomb potential is taken into account during the pulse.

  7. Experimental results to study astrophysical plasma jets using Intense Lasers

    NASA Astrophysics Data System (ADS)

    Loupias, B.; Gregory, C. D.; Falize, E.; Waugh, J.; Seiichi, D.; Pikuz, S.; Kuramitsu, Y.; Ravasio, A.; Bouquet, S.; Michaut, C.; Barroso, P.; Rabec Le Gloahec, M.; Nazarov, W.; Takabe, H.; Sakawa, Y.; Woolsey, N.; Koenig, M.

    2009-08-01

    We present experimental results of plasma jet, interacted with an ambient medium, using intense lasers to investigate the complex features of astrophysical jets. This experiment was performed in France at the LULI facility, Ecole Polytechnique, using one long pulse laser to generate the jet and a short pulse laser to probe it by proton radiography. A foam filled cone target was used to generate high velocity plasma jet, and a gas jet nozzle produced the well known ambient medium. Using visible pyrometry and interferometry, we were able to measure the jet velocity and electronic density. We get a panel of measurements at various gas density and time delay. From these measurements, we could underline the growth of a perturbed shape of the jet interaction with the ambient medium. The reason of this last observation is still in debate and will be presented in the article.

  8. Optical properties of a multibarrier structure under intense laser fields

    NASA Astrophysics Data System (ADS)

    Ospina, D. A.; Akimov, V.; Mora-Ramos, M. E.; Morales, A. L.; Tulupenko, V.; Duque, C. A.

    2015-11-01

    Using the diagonalization method and within the effective mass and parabolic band approximations, the energy spectrum and the wave functions are investigated in biased multibarrier structure taking into account the effects of nonresonant intense laser fields. We calculated the optical properties from the susceptibility using a nonperturbative formalism recently reported. We study the changes in the intersubband optical absorption coefficients and refraction index for several values of the dressing laser parameter and for some specific values of the electric field applied along the growth direction of the heterostructure. It is concluded from our study that the peaks in the optical absorption spectrum have redshifts or blueshifts as a function of the laser parameter and the electric field. These parameters could be suitable tools for tuning the electronic and optical properties of the multibarrier structure.

  9. Propagation of intense laser pulse in cold underdense plasma

    SciTech Connect

    Chen, X.L.; Sudan, R.N.

    1994-10-05

    We have derived a simplified set of three dimensional equations for the propagation of an intense laser pulse in cold underdense plasma [Phys. Fluids, {bold B}5, 1336 (1993)]. A three dimensional code has recently been developed to study this set of equations. Here we report on some of the preliminary results from the 3-d code. {copyright} 1994 {ital American} {ital Institute} {ital of} {ital Physics}

  10. Measurement of ultrafast dynamics in the interaction of intense laser pulses with gases, atomic clusters, and plasmas

    NASA Astrophysics Data System (ADS)

    Kim, Ki-Yong

    2003-10-01

    We have investigated the time resolved dynamics of intense, ultrashort pulse laser interactions with gases, nanometer-size clusters, and plasma waveguides. To probe the ultrafast dynamics in these interactions, we developed a new femtosecond optical diagnostic, single-shot supercontinuum spectral interferometry (SSSI), which measures ultra-rapid transients induced by an intense laser pulse in the complex index of refraction. The measurement of the transient refractive index in intense laser-heated materials provides a direct view of how the laser-produced perturbation evolves in time and space. Our SSSI diagnostic is capable of ˜10 fs temporal resolution on a temporal window ˜1.5 ps long, along with ˜7 mum one-dimensional (1D) spatial resolution. SSSI was first applied to probe the ionization dynamics of helium gas under the irradiation of high intensity (˜1017 W/cm 2) laser pulses. It revealed a characteristic stepwise transition process He → He+ → He2+, in agreement with the optical field ionization model. This measurement was used as a test case to demonstrate that finite laser-target interaction lengths can strongly affect the interpretation of all measurements involving extraction of transient phases. The time-resolved explosion dynamics of intense (˜1015 W/cm2) laser-heated clusters was also studied with SSSI and additional ultrafast optical diagnostics. Here, the ultrafast processes are ionization and rapid cluster plasma explosion. The measurement strongly supports our laser-cluster interaction scenario in which laser-heated clusters explode layer-by-layer, and the laser is strongly coupled at critical density. For the cluster sizes and laser intensities of this experiment, the measured several hundred-femtosecond evolution timescale of laser-heated clusters can be understood in terms of plasma hydrodynamics. A major implication of our understanding of microscopic cluster dynamics was the prediction and observation of self-focusing in clustered

  11. Characterization of material ablation driven by laser generated intense extreme ultraviolet light

    NASA Astrophysics Data System (ADS)

    Tanaka, Nozomi; Masuda, Masaya; Deguchi, Ryo; Murakami, Masakatsu; Sunahara, Atsushi; Fujioka, Shinsuke; Yogo, Akifumi; Nishimura, Hiroaki

    2015-09-01

    We present a comparative study on the hydrodynamic behaviour of plasmas generated by material ablation by the irradiation of nanosecond extreme ultraviolet (EUV or XUV) or infrared laser pulses on solid samples. It was clarified that the difference in the photon energy deposition and following material heating mechanism between these two lights result in the difference in the plasma parameters and plasma expansion characteristics. Silicon plate was ablated by either focused intense EUV pulse (λ = 9-25 nm, 10 ns) or laser pulse (λ = 1064 nm, 10 ns), both with an intensity of ˜109 W/cm2. Both the angular distributions and energy spectra of the expanding ions revealed that the photoionized plasma generated by the EUV light differs significantly from that produced by the laser. The laser-generated plasma undergoes spherical expansion, whereas the EUV-generated plasma undergoes planar expansion in a comparatively narrow angular range. It is presumed that the EUV radiation is transmitted through the expanding plasma and directly photoionizes the samples in the solid phase, consequently forming a high-density and high-pressure plasma. Due to a steep pressure gradient along the direction of the target normal, the EUV plasma expands straightforward resulting in the narrower angular distribution observed.

  12. The study towards high intensity high charge state laser ion sources.

    PubMed

    Zhao, H Y; Jin, Q Y; Sha, S; Zhang, J J; Li, Z M; Liu, W; Sun, L T; Zhang, X Z; Zhao, H W

    2014-02-01

    As one of the candidate ion sources for a planned project, the High Intensity heavy-ion Accelerator Facility, a laser ion source has been being intensively studied at the Institute of Modern Physics in the past two years. The charge state distributions of ions produced by irradiating a pulsed 3 J/8 ns Nd:YAG laser on solid targets of a wide range of elements (C, Al, Ti, Ni, Ag, Ta, and Pb) were measured with an electrostatic ion analyzer spectrometer, which indicates that highly charged ions could be generated from low-to-medium mass elements with the present laser system, while the charge state distributions for high mass elements were relatively low. The shot-to-shot stability of ion pulses was monitored with a Faraday cup for carbon target. The fluctuations within ±2.5% for the peak current and total charge and ±6% for pulse duration were demonstrated with the present setup of the laser ion source, the suppression of which is still possible. PMID:24593615

  13. Characterization of material ablation driven by laser generated intense extreme ultraviolet light

    SciTech Connect

    Tanaka, Nozomi Masuda, Masaya; Deguchi, Ryo; Murakami, Masakatsu; Fujioka, Shinsuke; Yogo, Akifumi; Nishimura, Hiroaki; Sunahara, Atsushi

    2015-09-14

    We present a comparative study on the hydrodynamic behaviour of plasmas generated by material ablation by the irradiation of nanosecond extreme ultraviolet (EUV or XUV) or infrared laser pulses on solid samples. It was clarified that the difference in the photon energy deposition and following material heating mechanism between these two lights result in the difference in the plasma parameters and plasma expansion characteristics. Silicon plate was ablated by either focused intense EUV pulse (λ = 9–25 nm, 10 ns) or laser pulse (λ = 1064 nm, 10 ns), both with an intensity of ∼10{sup 9 }W/cm{sup 2}. Both the angular distributions and energy spectra of the expanding ions revealed that the photoionized plasma generated by the EUV light differs significantly from that produced by the laser. The laser-generated plasma undergoes spherical expansion, whereas the EUV-generated plasma undergoes planar expansion in a comparatively narrow angular range. It is presumed that the EUV radiation is transmitted through the expanding plasma and directly photoionizes the samples in the solid phase, consequently forming a high-density and high-pressure plasma. Due to a steep pressure gradient along the direction of the target normal, the EUV plasma expands straightforward resulting in the narrower angular distribution observed.

  14. Physical and Chemical Changes of Polystyrene Nanospheres Irradiated with Laser

    SciTech Connect

    Mustafa, Mohd Ubaidillah; Juremi, Nor Rashidah Md.; Mohamad, Farizan; Wibawa, Pratama Jujur; Agam, Mohd Arif; Ali, Ahmad Hadi

    2011-05-25

    It has been reported that polymer resist such as PMMA (Poly(methyl methacrylate) which is a well known and commonly used polymer resist for fabrication of electronic devices can show zwitter characteristic due to over exposure to electron beam radiation. Overexposed PMMA tend to changes their molecular structure to either become negative or positive resist corresponded to electron beam irradiation doses. These characteristic was due to crosslinking and scissors of the PMMA molecular structures, but till now the understanding of crosslinking and scissors of the polymer resist molecular structure due to electron beam exposure were still unknown to researchers. Previously we have over exposed polystyrene nanospheres to various radiation sources, such as electron beam, solar radiation and laser, which is another compound that can act as polymer resist. We investigated the physical and chemical structures of the irradiated polystyrene nanospheres with FTIR analysis. It is found that the physical and chemical changes of the irradiated polystyrene were found to be corresponded with the radiation dosages. Later, combining Laser irradiation and Reactive Ion Etching manipulation, created a facile technique that we called as LARIEA NSL (Laser and Reactive Ion Etching Assisted Nanosphere Lithography) which can be a facile technique to fabricate controllable carbonaceous nanoparticles for applications such as lithographic mask, catalysts and heavy metal absorbers.

  15. Proton shock acceleration using a high contrast high intensity laser

    NASA Astrophysics Data System (ADS)

    Gauthier, Maxence; Roedel, Christian; Kim, Jongjin; Aurand, Bastian; Curry, Chandra; Goede, Sebastian; Propp, Adrienne; Goyon, Clement; Pak, Art; Kerr, Shaun; Ramakrishna, Bhuvanesh; Ruby, John; William, Jackson; Glenzer, Siegfried

    2015-11-01

    Laser-driven proton acceleration is a field of intense research due to the interesting characteristics of this novel particle source including high brightness, high maximum energy, high laminarity, and short duration. Although the ion beam characteristics are promising for many future applications, such as in the medical field or hybrid accelerators, the ion beam generated using TNSA, the acceleration mechanism commonly achieved, still need to be significantly improved. Several new alternative mechanisms have been proposed such as collisionless shock acceleration (CSA) in order to produce a mono-energetic ion beam favorable for those applications. We report the first results of an experiment performed with the TITAN laser system (JLF, LLNL) dedicated to the study of CSA using a high intensity (5x1019W/cm2) high contrast ps laser pulse focused on 55 μm thick CH and CD targets. We show that the proton spectrum generated during the interaction exhibits high-energy mono-energetic features along the laser axis, characteristic of a shock mechanism.

  16. Molecular Ionization at High Intensities: Characterizing OPA Laser Pulses

    NASA Astrophysics Data System (ADS)

    McAcy, Collin; Karnemaat, Ryan; Marsh, Skyler; Foote, David; Uiterwaal, Cornelis

    2012-06-01

    Ultrashort laser pulses have long been the primary instruments of probing and analyzing intense-field molecular dynamics on femtosecond timescales. In particular, processes involving resonance-enhanced multiphoton ionization (REMPI) have provided insight into ionization and dissociation dynamics. Typically the scope of REMPI is limited by the laser properties; namely, REMPI is limited by the transition energies accessible by an integer number of photons. However, the ability to tune the energies of these photons adds flexibility to the available resonances and, for longer wavelengths, makes tunneling the dominant ionization process. Optical parametric amplification (OPA) provides these changes, but the nonlinear processes required for OPA could have complicating effects on pulse duration and focusability, distorting beam quality and compromising experiments. We present the parametric amplification of 800-nm, 50-fs laser pulses in a TOPAS-C system: we use autocorrelation, power measurements, and knife-edging techniques to determine output pulse duration, intensity, and focal characteristics as a function of wavelength. We also report on the effects such changes will have on the practicality of various techniques requiring high-intensity processes.

  17. Model experiment of cosmic ray acceleration due to an incoherent wakefield induced by an intense laser pulse

    SciTech Connect

    Kuramitsu, Y.; Sakawa, Y.; Takeda, K.; Tampo, M.; Takabe, H.; Nakanii, N.; Kondo, K.; Tsuji, K.; Kimura, K.; Fukumochi, S.; Kashihara, M.; Tanimoto, T.; Nakamura, H.; Ishikura, T.; Kodama, R.; Mima, K.; Tanaka, K. A.; Mori, Y.; Miura, E.; Kitagawa, Y.

    2011-01-15

    The first report on a model experiment of cosmic ray acceleration by using intense laser pulses is presented. Large amplitude light waves are considered to be excited in the upstream regions of relativistic astrophysical shocks and the wakefield acceleration of cosmic rays can take place. By substituting an intense laser pulse for the large amplitude light waves, such shock environments were modeled in a laboratory plasma. A plasma tube, which is created by imploding a hollow polystyrene cylinder, was irradiated by an intense laser pulse. Nonthermal electrons were generated by the wakefield acceleration and the energy distribution functions of the electrons have a power-law component with an index of {approx}2. The maximum attainable energy of the electrons in the experiment is discussed by a simple analytic model. In the incoherent wakefield the maximum energy can be much larger than one in the coherent field due to the momentum space diffusion or the energy diffusion of electrons.

  18. Application of Laser-Induced Bone Therapy by Carbon Dioxide Laser Irradiation in Implant Therapy

    PubMed Central

    Naka, Takahiro; Yokose, Satoshi

    2012-01-01

    This study evaluated the application of laser-induced bone therapy (LIBT) to reduce implant healing time in rat tibia. Twenty 10-week-old female Sprague-Dawlay rats were used. The rats received laser irradiation (laser group) or sham operation (control group) on either side of the tibia. Five days after invasion, titanium implants were inserted in proximal tibia. Five, 10, and 20 days after implant placement, tibiae were collected. After taking micro-CT and performing a torque test, the tibiae were decalcified and 8-μm-thick sections were prepared. Specimens were stained with hematoxylin and eosin. Results. Micro-CT images, removal torque values, and histomorphometric analysis data demonstrated a significantly accelerated bone formation in the laser group earlier in the healing process. Conclusion. The use of laser irradiation was effective in promoting bone formation and acquiring osseointegration of titanium implants inserted in rat tibia. LIBT may be suitable for use in implant therapy. PMID:22505900

  19. Energy of a shock wave generated in different metals under irradiation by a high-power laser pulse

    SciTech Connect

    Gus'kov, S. Yu. Kasperczuk, A.; Pisarczyk, T.; Borodziuk, S.; Ullschmied, J.; Krousky, E.; Masek, K.; Pfeifer, M.; Skala, J.; Pisarczyk, P.

    2007-10-15

    The energies of a shock wave generated in different metals under irradiation by a high-power laser beam were determined experimentally. The experiments were performed with the use of targets prepared from a number of metals, such as aluminum, copper, silver and lead (which belong to different periods of the periodic table) under irradiation by pulses of the first and third harmonics of the PALS iodine laser at a radiation intensity of approximately 10{sup 14} W/cm{sup 2}. It was found that, for heavy metals, like for light solid materials, the fraction of laser radiation energy converted into the energy of a shock wave under irradiation by a laser pulse of the third harmonic considerably (by a factor of 2-3) exceeds the fraction of laser radiation energy converted under irradiation by a laser pulse of the first harmonic. The influence of radiation processes on the efficiency of conversion of the laser energy into the energy of the shock wave was analyzed.

  20. Is there a stimulation of blood microcirculation at low level laser irradiation

    NASA Astrophysics Data System (ADS)

    Rogatkin, Dmitry; Dunaev, Andrey

    2014-05-01

    In 1980-2000 besides the laser surgery an intensive evolution of Low Level Laser Therapy (LLLT) had started in medicine, especially in Russia as well as in several other East-European countries. At the same time the biophysical mechanisms of LLLT are still the subject of disputes. One of the most popular clinical effects at Low Level Laser Irradiation (LLLI) being mentioned in medical publications for justification of the LLLT healing outcome is a stimulation of blood microcirculation in irradiated area. It was declared a priori at a dawn of LLLT and is now a basis of medical interpretation of healing mechanisms of LLLT at least in Russia. But in past 20 years a lot of investigation was carried out on optical registration of microhaemodynamic parameters in vivo as well as a number of noninvasive diagnostic tools was created for that. So, today it is possible to experimentally check the blood microcirculation stimulation hypothesis. Our study was aimed on that during the past 10 years. The most precision and accurate experiments we have carried out recently using simultaneously three different noninvasive diagnostic techniques: Laser Doppler Flowmetry, Tissue Reflectance Oximetry and Infrared Thermography. All these methods didn't confirm the effect on the blood microcirculation stimulation in skin or mucosa at irradiation with the power density below 50 mW/cm2 and irradiation time up to 5-6 minutes. Above this threshold the heating on 0,8…1 °C of tissue in the field of irradiation and the corresponding synchronous increase of all parameters of microhemodynamics were observed.

  1. Photodynamic therapy with laser scanning mode of tumor irradiation

    NASA Astrophysics Data System (ADS)

    Chepurna, Oksana; Shton, Irina; Kholin, Vladimir; Voytsehovich, Valerii; Popov, Viacheslav; Pavlov, Sergii; Gamaleia, Nikolai; Wójcik, Waldemar; Zhassandykyzy, Maral

    2015-12-01

    In this study we propose a new version of photodynamic therapy performed by laser scanning. The method consists in tumor treatment by a light beam of a small cross section which incrementally moves through the chosen area with a defined delay at each point and repetitively re-scans a zone starting from the initial position. Experimental evaluation of the method in vitro on murine tumor model showed that despite the dose, applied by scanning irradiation mode, was 400 times lower, the tumor inhibition rate conceded to attained with continuous irradiation mode by only 20%.

  2. Improving the intensity of the HELEN Laser at AWE

    NASA Astrophysics Data System (ADS)

    Hopps, Nicholas; Nolan, Jonathan; Girling, Mark; Kopec, Maria; Harvey, Ewan

    2005-04-01

    The HELEN laser is a three-beam, large aperture Nd:glass laser, used for plasma physics studies at the Atomic Weapons Establishment in the UK. Two of the beams nominally deliver 500 J each in 1 ns at the second harmonic (527 nm). The third beam, the "backlighter", has recently been upgraded to operate as a chirped pulse amplification system and it now routinely delivers 70 J to target in 500 fs. Optimal focal spot performance is achieved using a closed-loop adaptive optics system, which ensures good wavefront characteristics, irrespective of whether previous firing of the amplifiers has induced refractive index variations in the laser glass. The system uses a 32 element bimorph mirror with 98 mm aperture, roughly half way through the laser chain. A Shack-Hartman wavefront sensor, positioned at the output of the laser is the diagnostic used to provide feedback to the deformable mirror. Correction of the static and slowly varying aberrations on the beam has been demonstrated. The fast aberrations induced during the flashlamp discharge have been evaluated. The improved focal spot characteristics result in an intensity on target of significantly greater than 1019 Wcm-2.

  3. Three-body fragmentation of CO{sub 2} driven by intense laser pulses

    SciTech Connect

    Wu, Chengyin Liu, Yunquan; Gong, Qihuang; Wu, Cong; Fan, Yameng; Xie, Xiguo; Wang, Peng; Deng, Yongkai

    2015-03-28

    Dissociative ionization dynamics were studied experimentally for CO{sub 2} driven by intense laser pulses. Three-dimensional momentum vectors of correlated atomic ions were obtained for each three-body fragmentation event using triple ion coincidence measurement. Newton diagram demonstrated that three-body fragmentation of CO{sub 2}{sup n+} (n = 3-6) can occur through Coulomb explosion process and sequential fragmentation process depending on the fragmentation channels. The experimental data from these two processes were disentangled by using correlation diagram of correlated ions. Based on the accurate Coulomb explosion data, we reconstructed the bond angle distributions of CO{sub 2}{sup n+} at the moment of fragmentation, which are close to that of neutral CO{sub 2} before laser irradiation.

  4. Heating of thin foils with a relativistic-intensity short-pulse laser.

    PubMed

    Audebert, P; Shepherd, R; Fournier, K B; Peyrusse, O; Price, D; Lee, R; Springer, P; Gauthier, J-C; Klein, L

    2002-12-23

    K-shell x-ray spectroscopy of sub-100 nm Al foils irradiated by high contrast, spatially uniform, 150 fs, Ilambda (2)=2 x 10(18) W microm(2)/cm(2), laser pulses is obtained with 500 fs time resolution. Two distinct phases occur: At /=500 fs the resonance transitions dominate. Initial satellites arise from a large area, high density, low temperature (approximately 100 eV) plasma created by fast electrons. Thus, contrary to predictions, a short, high intensity laser incident on a thin foil does not create a uniform, hot dense plasma. PMID:12484827

  5. Design and testing of low intensity laser biostimulator

    PubMed Central

    Valchinov, Emil S; Pallikarakis, Nicolas E

    2005-01-01

    -wave retardation plate. The proposed method for testing the device efficiency employs a biofeedback from the subject by recording the biopotentials evoked by the laser stimulus at related distant SLB sites. Therefore measuring of SLB biopotentials caused by the stimulus would indicate that a biopotential has been evoked at the irradiated site and has propagated to the measurement sites, rather than being caused by local changes of the electrical skin conductivity. Results A prototype device was built according to the proposed design using relatively inexpensive and commercially available components. The laser output can be pulse modulated from 0.1 to 1000 Hz with a duty factor from 10 to 90 %. The average output power density can be adjusted in the range 24 – 480 mW/cm2, where the total irradiation is limited to 2 Joule per stimulation session. The device is controlled by an 8-bit RISC Flash microcontroller with internal RAM and EEPROM memory, which allows for a wide range of different stimulation protocols to be implemented and memorized. The integrated laser diode driver with its onboard light power control loop provides safe and consistent laser modulation. The prototype was tested on the right Tri-Heater (TH) acupuncture meridian according to the proposed method. Laser evoked potentials were recorded from most of the easily accessible SLB along the meridian under study. They appear like periodical spikes with a repetition rate from 0.05 to 10 Hz and amplitude range 0.1 – 1 mV. Conclusion The prototype's specifications were found to be better or comparable to those of other existing devices. It features low component count, small size and low power consumption. Because of the low power levels used the possibility of sensory nerve stimulation via the phenomenon of shock or heat is excluded. Thus senseless optical stimulation is achieved. The optical system presented offers simple and cost effective way for beam collimation and polarization change. The novel method proposed

  6. Weakening of dentin from cracks resulting from laser irradiation

    PubMed Central

    Staninec, Michal; Meshkin, Neda; Manesh, Saman K.; Ritchie, R. O.; Fried, Daniel

    2011-01-01

    Cracking of tooth structure is a frequent mechanism of clinical failure necessitating treatment. Some laser conditions, particularly those without sufficient water cooling, may cause surface cracking of dentin. Surface cracks may serve as initiation sites for the onset of catastrophic fracture under mechanical stress, resulting in failure of the dentin. In this study, the hypothesis that laser initiated cracks result in lower bending strength of dentin was tested. Dentin beam specimens were prepared from human molar teeth, 1.1 × 1.1 × ~9 mm, and divided into groups C (control), W (wet), D (dry) of 12 beams each. In groups W, D, the middle of each beam on one surface (buccal) was irradiated with either a Er-YAG or Q-switched Er-YSGG laser and measured under a microscope, noting the dimensions in the irradiated area and immediately adjacent to irradiated area. Each beam was placed in a mechanical testing machine in a four-point bend jig and tested each with a monotonically increasing load at a displacement rate of 1 mm/min until failure. The bending strengths for groups C, W (Er-YAG laser) and D (Q-switched Er-YSGG laser) were, respectively, 141.6, 114.0, and 90.9 MPa. A one-way ANOVA determined a significant difference between groups C and D, p<0.001. Conclusion The Q-switched Er-YSGG laser without water caused cracks in the surface that significantly decreased the bending strength of dentin. PMID:19062088

  7. Laser irradiation for central-type lung cancer

    NASA Astrophysics Data System (ADS)

    Sun, Kai

    1993-03-01

    Based on laser irradiation experiments on isolated lung specimens of animals done in 1989, 8 patients with central type lung cancer were treated with Nd:YAG laser irradiation via fiberoptic bronchoscope from January 1990 to August 1991 in our hospital. The patients recruited were all diagnosed by fiberoptic bronchoscopy and histology as having central type bronchopulmonary cancer without distal metastasis. All patients were male with a mean age of 64 (range 57 - 72). Of 8 patients, 4 had squamous cell carcinoma, 3 adenocarcinoma, and 1 undifferentiated small cell carcinoma, all being stage TUM 3. After laser treatment, 6 cases had a result of significant response and 2 had minor response. Among 6 cases of atelectasis, 4 were completely cured or partially improved and 4 recovered from their hemoptysis. The subjective symptoms in all cases remitted. A combined chemotherapy was carried out accompanying laser therapy for all, 6 of whom had a shrink of focus over 25%. Six cases were re-examined with fiberoptic bronchoscopy, showing a distinct reduction of the tumor. Four cases expectorated black charring tissues and residual tumorous tissues persistently as an outcome. Two typical cases are reported, the characteristics, indications, techniques, and side effects of laser therapy are analyzed and factors affecting efficacy discussed, indicating that the technique has such advantages as easy operation, accurate orientation, and safe outcome. The procedure is really an effective one for treating central type lung cancer in intermediate or late stage.

  8. Au-C allotrope nano-composite films at extreme conditions generated by intense ultra-short laser

    NASA Astrophysics Data System (ADS)

    Khan, Saif A.; Saravanan, K.; Tayyab, M.; Bagchi, S.; Avasthi, D. K.

    2016-07-01

    Structural evolution of gold-carbon allotrope nano-composite films under relativistically intense, ultra-short laser pulse irradiation is studied in this work. Au-C nano-composite films, having 4 and 10 at.% of Au, were deposited by co-sputtering technique on silicon substrates. Au-C60 NC films with 2.5 at.% Au were deposited on 12 μm thick Al foil using co-evaporation technique. These samples were radiated with single pulse from 45 fs, 10 TW Ti:Sapphire Laser at RRCAT at an intensity of 3 × 1018 W cm-2. The morphological and compositional changes were investigated using scanning electron microscopy (SEM) and Rutherford back-scattering spectrometry (RBS) techniques. Laser pulse created three morphologically distinct zones around the point of impact on samples with silicon substrates. The gold content in 600 μm circular region around a point of impact is found to reduce by a factor of five. Annular rings of ∼70 nm in diameter were observed in case of Au-C NC film after irradiation. Laser pulse created a hole of about 400 μm in the sample with Al foil as substrate and wavy structures of 6 μm wavelength are found to be created around this hole. The study shows radial variation in nano-structure formation with varying local intensity of laser pulse.

  9. Hydrogen migration in methanol studied under asymmetric fs laser irradiation

    NASA Astrophysics Data System (ADS)

    Kotsina, N.; Kaziannis, S.; Kosmidis, C.

    2014-06-01

    Hydrogen migration processes in deuterated methanol (CH3OD) under the irradiation of ultrashort (30 fs) two color (400/800 nm) laser field have been investigated by means of time-of-flight mass spectrometry. The utilization of an asymmetric ω/2ω laser field contributes to a better understanding of hydrogen migration processes. Based on the comparative study of the asymmetry dependence and the angular distributions of the H2D+, HOD+ and H2OD+ fragment ions, whose formation requires hydrogen migration, it was feasible to distinguish the most probable site of the molecular skeleton where the hydrogen migrates from.

  10. Short-pulse high intensity laser thin foil interaction

    NASA Astrophysics Data System (ADS)

    Audebert, Patrick

    2003-10-01

    The technology of ultrashort pulse laser generation has progressed to the point that optical pulses larger than 10 J, 300 fs duration or shorter are routinely produced. Such pulses can be focused to intensities exceeding 10^18 W/cm^2. With high contrast pulses, these focused intensities can be used to heat solid matter to high temperatures with minimal hydrodynamic expansion, producing an extremely high energy-density state of matter for a short period of time. This high density, high temperature plasma can be studied by x-ray spectroscopy. We have performed experiments on thin foils of different elements under well controlled conditions at the 100 Terawatt laser at LULI to study the characteristics X-ray emission of laser heated solids. To suppress the ASE effect, the laser was frequency doubled. S-polarized light with a peak intensity of 10^19W/cm^2 was used to minimize resonance absorption. To decrease the effect of longitudinal temperature gradients very thin (800 μ) aluminum foil targets were used. We have also studied the effect of radial gradient by limiting the measured x-ray emission zone using 50μ or 100μ pinhole on target. The spectra, in the range 7-8Å, were recorded using a conical crystal spectrometer coupled to a 800 fs resolution streak camera. A Fourier Domain Interferometry (FDI) of the back of the foil was also performed providing a measurement of the hydrodynamic expansion as function of time for each shot. To simulate the experiment, we used the 1D hydrodynamic code FILM with a given set of plasma parameter (ρ, Te) as initial conditions. The X-ray emission was calculated by post processing hydrodynamic results with a collisional-radiative model which uses super-configuration average atomic data. The simulation reproduces the main features of the experimental time resolved spectrum.

  11. Intense Laser Ionization and Acceleration of Electrons in Highly-Charged Ions Using Vortex Laser Beams

    NASA Astrophysics Data System (ADS)

    Pi, Liang-Wen; Vikartofsky, Andrew; Starace, Anthony F.

    2016-05-01

    Recent advances in laser technology have led to the development of high-power petawatt lasers, making possible laser intensities of the order of 1022 W /cm2 . An electron in a highly-charged ion can be ionized in a laser field at its peak intensity and swiftly accelerated to GeV energies. Our prior investigation of laser acceleration of electrons using linearly-polarized Gaussian beams (with zero orbital angular momentum) has revealed that the final-state energies and ejection angles of the electrons depend on the initial target ion positions relative to the laser focus. We report here recent simulations of laser ionization and acceleration of electrons using linearly-polarized vortex laser beams (i.e., Laguerre-Gaussian beams), which carry orbital angular momentum and can spin microscopic objects. These simulations show that the inherent spiral phase structure of the vortex beams leads to improved final-state energy and ejection angle distributions of the electrons. This work is supported in part by DOE, Office of Science, Division of Chemical Sciences, Geosciences, and Biosciences, under Grant No. DE-FG02-96ER14646.

  12. Target Material Irradiation Studies for High-Intensity Accelerator Beams

    SciTech Connect

    Simos, N.; Kirk, H.; Ludewig, H.; Thieberger, P.; Weng, W.T.; McDonald, K.; Sheppard, J.; Evangelakis, G.; Yoshimura, K.; /KEK, Tsukuba

    2005-08-16

    This paper presents results of recent experimental studies focusing on the behavior of special materials and composites under irradiation conditions and their potential use as accelerator targets. The paper also discusses the approach and goals of on-going investigations on an expanded material matrix geared toward the neutrino superbeam and muon collider initiatives.

  13. Laser irradiation effects: A functional assessment

    NASA Astrophysics Data System (ADS)

    Robbins, David O.

    1994-08-01

    Specification of damage criteria and establishment of morphological data resulting from laser exposure has been an important mission for biomedical researchers and strategic planners. Equally important, however, from a military standpoint is the impact that this alteration, whether temporary or permanent, has on the ability of a soldier to complete a visually guided mission. Furthermore, while permanent visual loss associated with distinct morphological damage is of course serious it must also be recognized that temporary shifts in visual acuity or contrast sensitivity can occur at energy densities below those associated with distinct tissue damage. These temporary visual performance shifts could themselves be life threatening and may be the result of reversible or minute physical changes that are undetectable using current damage criteria. Our result suggests that significant shifts in visual sensitivity does occur at or below the ED50 level and that these shifts can be long lasting. Using a behavioral technique to measure on-going visual acuity, we have exposed awake, task-oriented rhesus monkeys to a variety of laser exposures which vary in energy density and temporal and spatial distribution on the retina. Our preliminary results in this project are consistent with the results of our previous studies and have extended the various exposure and performance criteria already established.

  14. Structural and optical properties of laser irradiated nano structured cadmium oxide thin film synthesized by sol-gel spin coating method

    NASA Astrophysics Data System (ADS)

    Farooq, W. A.; Al Saud, M.; Alahmed, Z. A.

    2016-05-01

    Cadmium oxide CdO nanostructured thin films are synthesized using sol-gel spin coating method. The prepared samples of CdO thin films are irradiated with 10 mJ laser from pulsed Q-Switched Nd:YAG laser at 1064 and 532 nm wavelength. The samples were exposed to 45 pulses of 7 ns pulse duration. Morphology and structural analysis were carried out with scanning electron microscope (SEM) micrographs and X-ray diffraction (XRD) patterns. Optical investigations were obtained with spectrometer and fluorospectrometer from Shimadzu. SEM micrographs confirm the nanostructure of the CdO film and indicate agglomeration of nanoparticles with laser irradiation. XRD patterns show decrease in the intensity of orientation peaks after laser irradiation. Variation in band gap energy, absorption peaks, and photoluminescence spectra with laser irradiation are observed.

  15. Resonant high-order harmonic generation from plasma ablation: Laser intensity dependence of the harmonic intensity and phase

    SciTech Connect

    Milosevic, D. B.

    2010-02-15

    Experimentally observed strong enhancement of a single high-order harmonic in harmonic generation from low-ionized laser plasma ablation is explained as resonant harmonic generation. The resonant harmonic intensity increases regularly with the increase of the laser intensity, while the phase of the resonant harmonic is almost independent of the laser intensity. This is in sharp contrast with the usual plateau and cutoff harmonics, the intensity of which exhibits wild oscillations while its phase changes rapidly with the laser intensity. The temporal profile of a group of harmonics, which includes the resonant harmonic, has the form of a broad peak in each laser-field half cycle. These characteristics of resonant harmonics can have an important application in attoscience. We illustrate our results using examples of Sn and Sb plasmas.

  16. Effect of free electron laser (FEL) irradiation on tooth dentine

    NASA Astrophysics Data System (ADS)

    Ogino, Seiji; Awazu, Kunio; Tomimasu, Takio

    1996-12-01

    Free electron laser (FEL) gives high efficiency for the photo-induced effects when the laser is tuned to the absorption maximum of target materials. The effect on dentine was investigated using the FEL tuned to 9.4 micrometers , which is an absorption maximum of phosphoric acid in infrared region. As a result, irradiated dentine surface which was amorphous had changed to the recrystalized structure by the spectroscopic analysis of IR absorption and x-ray diffraction. Furthermore, the atomic ratio of P/Ca had reduced from 0.65 to 0.60. These results indicated that 9.4micrometers -FEL irradiation caused the selective ablation of phosphoric acid ion and the reconstruction of disordered atoms.

  17. Laser stand for irradiation of targets by laser pulses from the Iskra-5 facility at a repetition rate of 100 MHz

    SciTech Connect

    Annenkov, V I; Garanin, Sergey G; Eroshenko, V A; Zhidkov, N V; Zubkov, A V; Kalipanov, S V; Kalmykov, N A; Kovalenko, V P; Krotov, V A; Lapin, S G; Martynenko, S P; Pankratov, V I; Faizullin, V S; Khrustalev, V A; Khudikov, N M; Chebotar, V S

    2009-08-31

    A train of a few tens of high-power subnanosecond laser pulses with a repetition period of 10 ns is generated in the Iskra-5 facility. The laser pulse train has an energy of up to 300 J and contains up to 40 pulses (by the 0.15 intensity level), the single pulse duration in the train being {approx}0.5 ns. The results of experiments on conversion of a train of laser pulses to a train of X-ray pulses are presented. Upon irradiation of a tungsten target, a train of X-ray pulses is generated with the shape of an envelope in the spectral band from 0.18 to 0.28 keV similar to that of the envelope of the laser pulse train. The duration of a single X-ray pulse in the train is equal to that of a single laser pulse. (lasers)

  18. Intense isolated few-cycle attosecond XUV pulses from overdense plasmas driven by tailored laser pulses

    NASA Astrophysics Data System (ADS)

    Chen, Zi-Yu; Li, Xiao-Ya; Chen, Li-Ming; Li, Yu-Tong; Zhu, Wen-Jun

    2014-06-01

    A method to generate an intense isolated few-cycle attosecond XUV pulse is demonstrated using particle-in-cell simulations. When a tailored laser pulse with a sharp edge irradiates a foil target, a strong transverse net current can be excited, which emits a few-cycle XUV pulse from the target rear side. The isolated pulse is ultrashort in the time domain with a duration of several hundred attoseconds. It also has a narrow bandwidth in the spectral domain compared to other XUV sources of high-order harmonics. It has most energy confined around the plasma frequency and no low-harmonic orders below the plasma frequency. It is also shown that XUV pulse of peak field strength up to $ 8\\times 10^{12} $ V$\\mathrm{m}^{-1}$ can be produced. Without the need for pulse selecting and spectral filtering, such an intense few-cycle XUV pulse is better suited to a number of applications.

  19. Nonlinear broadband photoluminescence of graphene induced by femtosecond laser irradiation

    SciTech Connect

    Liu, Wei-Tao; Wu, S.W.; Schuck, P.J.; Salmeron, Miquel; Shen, Y.R.; Wang, F.

    2010-07-01

    Upon femtosecond laser irradiation, a bright, broadband photoluminescence is observed from graphene at frequencies well above the excitation frequency. Analyses show that it arises from radiative recombination of a broad distribution of nonequilibrium electrons and holes, generated by rapid scattering between photoexcited carriers within tens of femtoseconds after the optical excitation. Its highly unusual characteristics come from the unique electronic and structural properties of graphene.

  20. Ptychographic measurements of ultrahigh-intensity laser-plasma interactions

    NASA Astrophysics Data System (ADS)

    Leblanc, A.; Monchocé, S.; Bourassin-Bouchet, C.; Kahaly, S.; Quéré, F.

    2016-04-01

    The extreme intensities now delivered by femtosecond lasers make it possible to drive and control relativistic motion of charged particles with light, opening a path to compact particle accelerators and coherent X-ray sources. Accurately characterizing the dynamics of ultrahigh-intensity laser-plasma interactions as well as the resulting light and particle emissions is an essential step towards such achievements. This remains a considerable challenge, as the relevant scales typically range from picoseconds to attoseconds in time, and from micrometres to nanometres in space. In these experiments, owing to the extreme prevalent physical conditions, measurements can be performed only at macroscopic distances from the targets, yielding only partial information at these microscopic scales. This letter presents a major advance by applying the concepts of ptychography to such measurements, and thus retrieving microscopic information hardly accessible until now. This paves the way to a general approach for the metrology of extreme laser-plasma interactions on very small spatial and temporal scales.

  1. Nonlinear Compton scattering of ultrashort intense laser pulses

    SciTech Connect

    Seipt, D.; Kaempfer, B.

    2011-02-15

    The scattering of temporally shaped intense laser pulses off electrons is discussed by means of manifestly covariant quantum electrodynamics. We employ a framework based on Volkov states with a time-dependent laser envelope in light-cone coordinates within the Furry picture. An expression for the cross section is constructed unambiguously in respect of the pulse length. A broad distribution of scattered photons with a rich pattern of subpeaks like that obtained in Thomson scattering is found. These broad peaks may overlap at sufficiently high laser intensity, rendering inappropriate the notion of individual harmonics. The limit of monochromatic plane waves as well as the classical limit of Thomson scattering are discussed. As a main result, a scaling law is presented connecting the Thomson limit with the general result for arbitrary kinematics. In the overlapping regions of the spectral density, the classical and quantum calculations give different results, even in the Thomson limit. Thus, a phase-space region is identified where the differential photon distribution is strongly modified by quantum effects.

  2. Effect of laser irradiation for healing of the skin-muscle wounds of animals

    NASA Astrophysics Data System (ADS)

    Lapina, Victoria A.; Veremei, Eduard I.; Pancovets, Evgeniy A.

    2000-05-01

    The purpose of our investigation was to study the medical effect of low-intensity laser influence on healing of skin- muscle wounds of agricultural animals. We used the laser radiation of low intensity for cub's therapy: to sucking-pigs after herniotomy and castration, to cattle cubs after skin- muscle wounds. The animals were kept under clinical observation up to their recovery. The recuperation dynamic was observed by changing of blood quotients, leukograms, sizes of inflammatory edema, general behavior of animals. The positive dynamic of blood quotients of the experimental animal groups was really higher than that in control. The analysis of wound healing after laser influence shows that wound surface of experimental group was to a great extent smaller in comparison with control group of animals. So, these facts testify about anti-inflammatory action of laser radiation, which hastens regenerative and rehabilitative processes. Analysis of the obtained experimental data has revealed the positive influence of laser irradiation on the dynamics of wound adhesion of agricultural animals.

  3. Recent High-Intensity Experiments at the Trident Laser

    NASA Astrophysics Data System (ADS)

    Cobble, James; Palaniyappan, Sasikumar; Gautier, Cort; Kim, Yongho; Huang, Chengkun

    2014-10-01

    With near-diffraction-limited irradiance of 2 × 1020 W/cm2 on target and prelase contrast better than 10-8, we have accessed the regime of relativistic transparency (RT) at the Trident Laser. The goal was to assess electron debris emitted from the target rear surface with phase-contrast imaging (PCI) and current density measurements (hence, the total electron current). Companion diagnostics show whether the experiments are in the target-normal-sheath-acceleration mode or in the RT regime. The superb laser contrast allows us to shoot targets as thin as 50 nm. PCI at 527 nm is temporally resolved to 600 fs. It has shown the evolution of electron behavior over tens of ps, including thermal electrons accompanying the ion jet, accelerated to many tens of MeV earlier in time. Faraday-cup measurements indicate the transfer of many microC of charge during the laser drive. As a ride-along experiment using a gas Cherenkov detector (GCD), we have detected gamma rays of energy >5 MeV. This radiation has a prompt component and a lesser source, driven by accelerated ions, that is time resolved by the GCD. The ion time of flight is compared to Thomson parabola data. Electron energy spectra are also collected. This work is supported by US DOE/NNSA, performed at LANL, operated by LANS LLC under Contract DE-AC52-06NA25396.

  4. Acceleration of highly charged GeV Fe ions from a low-Z substrate by intense femtosecond laser

    NASA Astrophysics Data System (ADS)

    Nishiuchi, M.; Sakaki, H.; Esirkepov, T. Zh.; Nishio, K.; Pikuz, T. A.; Faenov, A. Ya.; Skobelev, I. Yu.; Orlandi, R.; Sako, H.; Pirozhkov, A. S.; Matsukawa, K.; Sagisaka, A.; Ogura, K.; Kanasaki, M.; Kiriyama, H.; Fukuda, Y.; Koura, H.; Kando, M.; Yamauchi, T.; Watanabe, Y.; Bulanov, S. V.; Kondo, K.; Imai, K.; Nagamiya, S.

    2015-03-01

    Almost fully stripped Fe ions accelerated up to 0.9 GeV are demonstrated with a 200 TW femtosecond high-intensity laser irradiating a micron-thick Al foil with Fe impurity on the surface. An energetic low-emittance high-density beam of heavy ions with a large charge-to-mass ratio can be obtained, which is useful for many applications, such as a compact radio isotope source in combination with conventional technology.

  5. Acceleration of highly charged GeV Fe ions from a low-Z substrate by intense femtosecond laser

    SciTech Connect

    Nishiuchi, M. Sakaki, H.; Esirkepov, T. Zh.; Pirozhkov, A. S.; Sagisaka, A.; Ogura, K.; Kiriyama, H.; Fukuda, Y.; Kando, M.; Bulanov, S. V.; Kondo, K.; Nishio, K.; Orlandi, R.; Koura, H.; Imai, K.; Pikuz, T. A.; Faenov, A. Ya.; Skobelev, I. Yu.; Sako, H.; Matsukawa, K.; and others

    2015-03-15

    Almost fully stripped Fe ions accelerated up to 0.9 GeV are demonstrated with a 200 TW femtosecond high-intensity laser irradiating a micron-thick Al foil with Fe impurity on the surface. An energetic low-emittance high-density beam of heavy ions with a large charge-to-mass ratio can be obtained, which is useful for many applications, such as a compact radio isotope source in combination with conventional technology.

  6. Photoacoustic transients generated by laser irradiation of thin films.

    PubMed

    Xiong, Lian; Ruddock, Jennifer M; Diebold, Gerald J

    2015-06-01

    Irradiation of an optically thin layer immersed in a transparent fluid with pulsed laser radiation can generate photoacoustic waves through two mechanisms. The first of these is the conventional optical heating of the layer followed by thermal expansion, in which the mechanical motion of the expansion launches a pair of oppositely directed sound waves. A second, recently reported mechanism, is operative when heat is conducted to the transparent medium raising its temperature, while at the same time reducing the temperature in the absorbing body. The latter mechanism has been shown to result in compressive transients at the leading edges of the photoacoustic waveforms. Here the photoacoustic effect produced by irradiating thin metal films which undergo negligible thermal expansion under optical irradiation, but which generate sound solely by the heat transfer mechanism is investigated. Solution to the wave equation for the photoacoustic effect from the heat transfer mechanism is given and compared with the results of experiments using nanosecond laser pulses to irradiate thin metal films. PMID:26236642

  7. Double ionization of H2 by intense attosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Lee, Teck-Ghee; Pindzola, M. S.; Robicheaux, F.

    2010-08-01

    We present calculations of the double ionization of H2 induced by an intense attosecond laser pulse at a photon energy of 40 eV using the time-dependent close-coupling method within the fixed nuclei approximation. We focus on two-photon absorption processes and examine how the response of the ejected electrons, in particular the single- and the double-energy differential probabilities, is affected by linear and circular polarizations at laser-field intensities ranging from 10^{15}\\; \\rm W\\,cm^{-2} to 10^{16}\\; \\rm W\\,cm^{-2} . In general, we find that for both linearly and circularly polarized pulses, sequential peaks and non-sequential wells that appear in both the single- and double-energy differential probabilities are akin to the analogous two-electron photoemission processes in the helium atom driven by intense attosecond pulses. In addition, for the case of a linearly polarized pulse, a clear signature of the sequential double-electron above the threshold ionization process can be seen in these spectra.

  8. Double Ionization of Hydrogen Molecule by Intense Attosecond Laser Pulses

    NASA Astrophysics Data System (ADS)

    Lee, Teck-Ghee; Pindzola, M. S.; Robicheaux, F.

    2010-03-01

    Time-dependent close-coupling calculations within the fixed nuclei approximation are carried out for the double ionization of H2 induced by an intense attosecond laser pulse at a photon energy of 40 eV. We consider here the two-photon absorption processes and examine the response of the ejected electrons, particularly the single- and the double-electron energy distributions, to linearly and circularly polarized pulse at laser intensities between 10^15 W/cm^2 and 10^16 W/cm^2. We find that, for both the linearly and circularly polarized pulses, sequential peaks and non-sequential wells appear in both the single- and double-electron energy distributions that are generally akin to the analogous two electrons photoemission processes in He atom driven by a linearly polarized intense attosecond pulse [1,2]. Furthermore, a clear signature of the sequential double-electron above threshold ionization process can be seen in the single- and double-electron energy distributions when a linearly polarized pulse is being used.[4pt] [1] I. F. Barna, J. Wang, and J. Burgdorfer, Phys. Rev. A. 73, 023402 (2006) [0pt] [2] T-G Lee, M. S. Pindzola and F. Robicheaux, Phys. Rev. A. 79, 053420 (2009)

  9. Toxicity of laser irradiated photoactive fluoride PrF3 nanoparticles toward bacteria

    NASA Astrophysics Data System (ADS)

    Pudovkin, M. S.; Korableva, S. L.; Krasheninnicova, A. O.; Nizamutdinov, A. S.; Semashko, V. V.; Zelenihin, P. V.; Alakshin, E. M.; Nevzorova, T. A.

    2014-11-01

    The article is devoted to exploration of biological effects of crystalline PrF3 nanoparticles toward Salmonella typhimurium TA 98 bacteria under the laser irradiation. Obtained results show bactericidal activity of PrF3 nanoparticles and optimal parameters of laser irradiation (power of laser irradiation, wavelength, diameter of the laser spoil, and exposure time) have been found under which the effects of bactericidal activity become the most significant. Survival of bacterial cells under laser irradiation with wavelength 532 nm in colloidal solution of PrF3 nanoparticles was 39%, 34%, 20% for exposure times 5 minutes, 15 minutes and 30 minutes, correspondingly.

  10. Electron spectra of xenon clusters irradiated with a laser-driven plasma soft-x-ray laser pulse

    SciTech Connect

    Namba, S.; Takiyama, K.; Hasegawa, N.; Kishimoto, M.; Nishikino, M.; Kawachi, T.

    2011-11-15

    Xenon clusters were irradiated with plasma soft-x-ray laser pulses (having a wavelength of 13.9 nm, time duration of 7 ps, and intensities of up to 10 GW/cm{sup 2}). The laser photon energy was high enough to photoionize 4d core electrons. The cross section is large due to a giant resonance. The interaction was investigated by measuring the electron energy spectra. The photoelectron spectra for small clusters indicate that the spectral width due to the 4d hole significantly broadens with increasing cluster size. For larger clusters, the electron energy spectra evolve into a Maxwell-Boltzmann distribution, as a strongly coupled cluster nanoplasma is generated.

  11. Laser induced damage of sapphire and titanium doped sapphire crystals under femtosecond to nanosecond laser irradiation

    NASA Astrophysics Data System (ADS)

    Bussière, B.; Utéza, O.; Sanner, N.; Sentis, M.; Riboulet, G.; Vigroux, L.; Commandré, M.; Wagner, F.; Natoli, J.-Y.; Chambaret, J.-P.

    2009-10-01

    The use of large Ti:Sapphire crystals in ultra fast high peak power laser amplifiers makes crucial the problem of crystal laser induced damage. These works aim to quantify the laser induced damage threshold (LIDT) of Sapphire and Ti:Sapphire crystals under femtosecond, picosecond and nanosecond laser pulse irradiations, which are typically encountered in such laser chains. Furthermore, a study of the influence of cryogenic conditions on the LIDT of Ti:Sapphire crystals and of their anti-reflection coating has been performed. The results are important to understand the mechanisms leading to the damage, and to reveal the key parameters which will have to be optimized in future high peak power laser chains.

  12. Propagation of intense subpicosecond laser pulses through underdense plasmas

    SciTech Connect

    Coverdale, C.A.; Darrow, C.B.; Decker, C.D.; Mori, W.B.; Tzeng, K.; Marsh, K.A.; Clayton, C.E.; Joshi, C.

    1995-06-05

    The propagation of an intense, subpicosecond laser pulse through a substantial length ({ital L}/{lambda}{similar_to}10{sup 3}) of an underdense plasma ({ital n}/{ital n}{sub {ital c}}{similar_to}1%) is studied through experiments and computer simulations. For {ital I}=8{times}10{sup 17} W/cm{sup 2} only 55% of the incident laser light was transmitted through the plasma within the focal cone angle. The decrease in transmission was accompanied by Raman forward scattering as evidenced by the generation of anti-Stokes sidebands and up to 2 MeV electrons. Simulations show that the majority of the reduction in transmission could be due to Raman forward and side scattering.

  13. Remote intensity fluctuation measurements with a laser Doppler radar

    NASA Technical Reports Server (NTRS)

    Kennedy, L. Z.; Bilbro, J. W.

    1976-01-01

    A coaxial focused CW scanning laser Doppler velocimeter (SLDV) radar equipment applying heterodyne detection at 10.6 microns can measure intensity fluctuations under field conditions. The set includes a 20 W CO2 laser, a coaxial Cassegrainian telescope, standard heterodyne equipment, and a SAW spectrum analyzer with 100 kHz signal resolution. Operation of the equipment and techniques for taking remote measurements are described briefly. Applications to remote measurements of transverse component of wind speed, as a complement to the traditional Doppler method of determining axial velocity, are under study. SLDV equipment has been used in detection, tracking, and measurements of atmospheric turbulence associated with aircraft wing-tip vortices or with dust devils, and in measurement of general atmospheric wind profiles.

  14. Venous Lake of the Lips Treated Using Photocoagulation with High-Intensity Diode Laser

    PubMed Central

    Galletta, Vivian C.; de Paula Eduardo, Carlos; Migliari, Dante A.

    2010-01-01

    Abstract Objective: To evaluate the effectiveness of photocoagulation with high-intensity diode laser in the treatment of venous lake (VL) lesions. Background Data: VL is a common vascular lesion characterized by elevated, usually dome-shaped papules, ranging in color from dark blue to dark purple, seen more frequently in elderly patients. They often occur as single lesions on the ears, face, lips, or neck. Once formed, lesions persist throughout life. Although these lesions are usually asymptomatic, they can bleed if injured. Methods: Seventeen patients (7 men and 10 women) with VL on the lip were treated using a noncontact diode laser (wavelength 808 nm, power output 2–3 W in continuous wave). Results: After only one irradiation exposure, all lesions were successfully treated. Healing was completed in approximately 2 to 3 weeks, and none of the patients experienced complications. Postoperative discomfort and scarring were not present or were minimal. Conclusion: Photocoagulation with high-intensity diode laser is an effective, bloodless procedure for the treatment of VL. PMID:19811083

  15. Trident as an ultrahigh irradiance laser

    SciTech Connect

    Johnson, R.P.; Moncur, N.K.; Cobble, J.A.; Watt, R.G.; Gibson, R.B.

    1995-02-01

    The Trident Nd:glass ICF laser at Los Alamos may be operated in a mode that produces high ultrashort pulses by the chirp/compression method. The 125-ps pulses from a standard moderated, ND:YLF oscillator are first frequency-broadened to 3-nm bandwidth, chirped in a quartz fiber, and then compressed with a grating pair to 1.5 ps. A second quartz fiber then provides nonlinear polarization rotation for background and satellite suppression and to further broaden the spectrum to >7 nm. Pulses are chirped again to 1 ns width with a second grating pair and amplified in a ND:YAG pumped Ti:sapphire regenerative amplifier. Millijoule-level output is then amplified through the existing phosphate glass Trident amplifier chain before compression to <400 fs. Energy {>=}1 J with excellent beam quality and contrast ratio is routinely produced by compressing after three rod amplifier stages. Higher energies are possible by compression further along the amplifier chain. Simultaneous use of long ({approximately}1 ns) pulses for plasma formation is also possible.

  16. Activity of respiratory system during laser irradiation of brain structures

    NASA Astrophysics Data System (ADS)

    Merkulova, N. A.; Sergeyeva, L. I.

    1984-06-01

    The performance of one of the principal links of the respiratory system, the respiratory center, was studied as a function of the exposure of the medulla oblongata and the sensomotor zone of the cerebral hemisphere cortex to low level laser irradiation in the red wavelength of the spectrum. Experiments were done on white rats under barbital anesthesia. Under such conditions a substantial effect was observed on the activity of the respiratory center. Laser light may display activating or inhibitory influences, in some cases the bilateral symmetry of the activity of the respiratory center is affected indicating deep changes in the integrative mechanism of the functioning of the right and left sides of the hemispheres. The laser beam effect depends on many factors: specific light properties, duration of the exposure, repetition of exposures, initial functional state of the CNS, etc.

  17. Study of the effects of semiconductor laser irradiation on peripheral nerve injury

    NASA Astrophysics Data System (ADS)

    Xiong, G. X.; Li, P.

    2012-11-01

    In order to study to what extent diode laser irradiation effects peripheral nerve injury, the experimental research was made on rabbits. Experimental results show that low-energy semiconductor laser can promote axonal regeneration and improve nervous function. It is also found that simultaneous exposure of the injured peripheral nerve and corresponding spinal segments to laser irradiation may achieve the most significant results.

  18. Frequency conversion of high-intensity, femtosecond laser pulses

    SciTech Connect

    Banks, P S

    1997-06-01

    Almost since the invention of the laser, frequency conversion of optical pulses via non- linear processes has been an area of active interest. However, third harmonic generation using ~(~1 (THG) in solids is an area that has not received much attention because of ma- terial damage limits. Recently, the short, high-intensity pulses possible with chirped-pulse amplification (CPA) laser systems allow the use of intensities on the order of 1 TW/cm2 in thin solids without damage. As a light source to examine single-crystal THG in solids and other high field inter- actions, the design and construction of a Ti:sapphire-based CPA laser system capable of ultimately producing peak powers of 100 TW is presented. Of special interest is a novel, all-reflective pulse stretcher design which can stretch a pulse temporally by a factor of 20,000. The stretcher design can also compensate for the added material dispersion due to propagation through the amplifier chain and produce transform-limited 45 fs pulses upon compression. A series of laser-pumped amplifiers brings the peak power up to the terawatt level at 10 Hz, and the design calls for additional amplifiers to bring the power level to the 100 TW level for single shot operation. The theory for frequency conversion of these short pulses is presented, focusing on conversion to the third harmonic in single crystals of BBO, KD*P, and d-LAP (deuterated I-arginine phosphate). Conversion efficiencies of up to 6% are obtained with 500 fs pulses at 1053 nm in a 3 mm thick BBO crystal at 200 GW/cm 2. Contributions to this process by unphasematched, cascaded second harmonic generation and sum frequency generation are shown to be very significant. The angular relationship between the two orders is used to measure the tensor elements of C = xt3)/4 with Crs = -1.8 x 1O-23 m2/V2 and .15Cri + .54Crs = 4.0 x 1O-23 m2/V2. Conversion efficiency in d-LAP is about 20% that in BBO and conversion efficiency in KD*P is 1% that of BBO. It is calculated

  19. The effect of low-intensity laser therapy on wound healing in Streptozotocin-induced diabetic rats

    NASA Astrophysics Data System (ADS)

    Rabelo, Sylvia B.; Villaverde, Antonio G. J. B.; Salgado, Miguel A. C.; Melo, Milene d. S.; Nicolau, Renata A.; Pacheco, Marcos T. T.

    2004-10-01

    Diabetes Mellitus is a condition that results in a delay of the wound healing process, that is associated with an insufficient production of collagen, a decrease of the amount of collagen fibrils and deficient blood flow in the wound area. It is sugested that Low Intensity Laser Therapy acts by improving wound healing in normal organisms, accelerating tissue regeneration. The aim of this work was to investigate the biostimulatory effect of the HeNe laser irradiation, at 632.8 nm, on wound healing in 15 male rats suffering from diabetes induced by Streptozotocin, compared to 15 control diabetic animals. Irradiation parameters were: laser power of 15mW, exposition time of 17 s., irradiated area of 0.025 cm2 and laser energy density of 10 J/cm2. Full-thickness skin squared samples, with 5 mm of non-injured tissue around the wound, were obtained at 4, 7 and 15 days after wounding procedure (5 treated and 5 control animals each time). The histopathologic analysis performed by haematoxylin-cosin staining. Results suggested that the irradiation of diabetic rats was efficient for wound healing. Treated group presented better quality of the wound tissues by the macroscopic observation than control group and the microscopic analysis demonstrated that treated animals had better histopathologic evaluation than non treated.

  20. Coherent combs in ionization by intense and short laser pulses

    NASA Astrophysics Data System (ADS)

    Krajewska, K.; Kamiński, J. Z.

    2016-03-01

    Photoionization of positive ions by a train of intense, short laser pulses is investigated within the relativistic strong field approximation, using the velocity gauge. The formation of broad peak structures in the high-energy domain of photoelectrons is observed and interpreted. The emergence of coherent photoelectron energy combs within these structures is demonstrated, and it is interpreted as the consequence of the Fraunhofer-type interference/diffraction of probability amplitudes of ionization from individual pulses comprising the train. Extensions to the coherent angular combs are also studied, and effects related to the radiation pressure are presented.

  1. Luminescence properties of mechanically milled and laser irradiated ZnO

    NASA Astrophysics Data System (ADS)

    Radoi, R.; Fernández, P.; Piqueras, J.; Wiggins, M. S.; Solis, J.

    2003-07-01

    The effect of mechanical milling on the luminescence properties of ZnO microcrystalline samples has been studied by means of cathodoluminescence in a scanning electron microscope. The samples consisted of pressed pellets of commercially available ZnO powder which were ball milled to investigate the possibility of nanocrystalline ZnO formation. Changes observed in the relative intensities of the characteristic ultraviolet and green band of ZnO are discussed in terms of defects generated during milling. The effect of nano- and picosecond pulsed laser irradiation on the particle size and luminescence of the milled samples has been also investigated.

  2. Production of proton beams with narrow-band energy spectra from laser-irradiated ultrathin foils

    SciTech Connect

    Robinson, A. P. L; Gibbon, P.

    2007-01-15

    Three-dimensional gridless particle simulations of proton acceleration via irradiation of a very thin foil by a short-pulse, high-intensity laser have been performed to evaluate recently proposed microstructured target configurations. It is found that a pure proton microdot target does not by itself result in a quasimonoenergetic proton beam. Such a beam can only be produced with a very lightly doped target, in qualitative agreement with one-dimensional theory. The simulations suggest that beam quality in current experiments could be dramatically improved by choosing microdot compositions with a 5-10 times lower proton fraction.

  3. Spatially resolved x-ray spectroscopy investigation of femtosecond laser irradiated Ar clusters.

    PubMed

    Junkel-Vives, G C; Abdallah, J; Auguste, T; D'Oliveira, P; Hulin, S; Monot, P; Dobosz, S; Faenov, A Ya; Magunov, A I; Pikuz, T A; Skobelev, I Yu; Boldarev, A S; Gasilov, V A

    2002-03-01

    High temperature plasmas have been created by irradiating Ar clusters with high intensity 60-fs laser pulses. Detailed spectroscopic analysis of spatially resolved, high resolution x-ray data near the He(alpha) line of Ar is consistent with a two-temperature collisional-radiative model incorporating the effects of highly energetic electrons. The results of the spectral analysis are compared with a theoretical hydrodynamic model of cluster production, as well as interferometric data. The plasma parameters are notably uniform over one Rayleigh length (600 microm). PMID:11909265

  4. Cellular immunological effects of laser irradiation and immunoadjuvant application

    NASA Astrophysics Data System (ADS)

    Chen, Wei R.; Mohamed, Abdiwahab; Naylor, Mark F.; Bartels, Kenneth E.; Ritchey, Jerry W.; Liu, Hong; Nordquist, Robert E.

    2007-02-01

    Immune system is critical in the fight against cancer. Particular important is the responses through immune cells that regulate immunological functions. Certain cytokines enhance cancer immunity (such as IL12 and interferon gamma) and others interfere or impede cancer immunity (such as IL10). The clinical outcome can be linked to the balance of these cytokines, such as IL10 to IL12 ratio. Effective treatments often reduce the IL10:IL12 ratio, indicating higher levels of the cancer fighting IL12. To enhance immune responses, a combination of laser irradiation and concurrent use of immunostimulants has been applied for the treatment of tumors. In a recent study, an 805-nm laser in conjunction with indocyanine green (ICG) has been used to treat EMT6 mammary tumors in mice. An immunoadjuvant, glycated chitosan (GC), was intratumoral injected after the laser irradiation. Our preliminary results showed that tumor-bearing mice treated either with the immunoadjuvant alone or with the combination of laser and immunoadjuvant had lower IL10:IL12 ratios than animals that received no treatment. This may play an important in the treatment to decrease tumor size and to increase survival times of mice. Cellular activities after laser-ICG-GC treatment of DBMA-4 mammary tumors in rats also showed infiltration of immune cells to the treatment sites, indicating a possible induced immunity. The combination of laser treatment and immunotherapy has been used to treat late-stage melanoma patients; the responses, both treated primary tumors and the metastases, to the treatment have been promising. The histology of two patients, before and after treatment, is presented to show the effects of this novel treatment method.

  5. Different photodynamic effect between continuous wave and pulsed laser irradiation modes in k562 cells in vitro

    NASA Astrophysics Data System (ADS)

    Klimenko, V. V.; Bogdanov, A. A.; Knyazev, N. A.; Rusanov, A. A.; Dubina, M. V.

    2014-10-01

    Photodynamic therapy is a cancer treatment method is used primarily continuous mode laser radiation. At high power density irradiation occurs intense consumption of molecular oxygen and this caused hypoxic tumor tissue, which leads to inefficiency PDT. In this paper, pulsed and continuous irradiation modes during PDT photosensitizer Radachlorin were compared. A mathematical model for the generation of singlet oxygen 1O2 in tumor cells during photodynamic therapy with tissue oxygenation was developed. Our study theoretically and experimentally demonstrates the increased singlet oxygen generation efficiency in a pulsed irradiation mode compared to continuous wave mode with the same power density 20mW/cm2. Experimental in vitro showed that pulsed irradiation mode mostly induces apoptosis k562 tumor cells at irradiation doses of k562 1.25 - 2.5J/cm2 while the continuous mode induced necrosis.

  6. Measurement of the relaxation time of hot electrons in laser-solid interaction at relativistic laser intensities

    SciTech Connect

    Chen, H; Shepherd, R; Chung, H K; Dyer, G; Faenov, A; Fournier, K B; Hansen, S B; Hunter, J; Kemp, A; Pikuz, T; Ping, Y; Widmann, K; Wilks, S C; Beiersdorfer, P

    2006-08-22

    The authors have measured the relaxation time of hot electrons in short pulse laser-solid interactions using a picosecond time-resolved x-ray spectrometer and a time-integrated electron spectrometer. Employing laser intensities of 10{sup 17}, 10{sup 18}, and 10{sup 19} W/cm{sup 2}, they find increased laser coupling to hot electrons as the laser intensity becomes relativistic and thermalization of hot electrons at timescales on the order of 10 ps at all laser intensities. They propose a simple model based on collisional coupling and plasma expansion to describe the rapid relaxation of hot electrons. The agreement between the resulting K{sub {alpha}} time-history from this model with the experiments is best at highest laser intensity and less satisfactory at the two lower laser intensities.

  7. Densification of silica glass induced by 0.8 and 1.5 {mu}m intense femtosecond laser pulses

    SciTech Connect

    Saliminia, A.; Nguyen, N.T.; Chin, S.L.; Vallee, R.

    2006-05-01

    We investigate the physical mechanisms responsible for waveguide formation in silica glass induced by 1 kHz intense femtosecond laser pulses from a Ti-sapphire laser at 0.8 {mu}m as well as from a femtosecond optical parametric amplifier at 1.5 {mu}m. It is demonstrated that the densification taking place at the irradiated region is the principal cause for refractive index change in the waveguides written with both 0.8 and 1.5 {mu}m pulses. The birefringence induced by the stress arising from such densification and its behavior against thermal annealing are also studied.

  8. Controllable generation of reactive oxygen species by femtosecond-laser irradiation

    SciTech Connect

    Yan, Wei; He, Hao Wang, Yintao; Wang, Yisen; Hu, Minglie; Wang, Chingyue

    2014-02-24

    Femtosecond lasers have been advancing Biophotonics research in the past two decades with multiphoton microscopy, microsurgery, and photodynamic therapy. Nevertheless, laser irradiation is identified to bring photodamage to cells via reactive oxygen species (ROS) generation with unclear mechanism. Meanwhile, currently in biological researches, there is no effective method to provide controllable ROS production precisely, which originally is leaked from mitochondria during respiration and plays a key role in a lot of important cellular processes and cellular signaling pathways. In this study, we show the process of how the tightly focused femtosecond-laser induces ROS generation solely in mitochondria at the very beginning and then release to cytosol if the stimulus is intense enough. At certain weak power levels, the laser pulses induce merely moderate Ca{sup 2+} release but this is necessary for the laser to generate ROS in mitochondria. Cellular original ROS are also involved with a small contribution. When the power is above a threshold, ROS are then released to cytosol, indicating photodamage overwhelming cellular repair ability. The mechanisms in those two cases are quite different. Those results clarify parts of the mechanism in laser-induced ROS generation. Hence, it is possible to further this optical scheme to provide controllable ROS generation for ROS-related biological researches including mitochondrial diseases and aging.

  9. Controllable generation of reactive oxygen species by femtosecond-laser irradiation

    NASA Astrophysics Data System (ADS)

    Yan, Wei; He, Hao; Wang, Yintao; Wang, Yisen; Hu, Minglie; Wang, Chingyue

    2014-02-01

    Femtosecond lasers have been advancing Biophotonics research in the past two decades with multiphoton microscopy, microsurgery, and photodynamic therapy. Nevertheless, laser irradiation is identified to bring photodamage to cells via reactive oxygen species (ROS) generation with unclear mechanism. Meanwhile, currently in biological researches, there is no effective method to provide controllable ROS production precisely, which originally is leaked from mitochondria during respiration and plays a key role in a lot of important cellular processes and cellular signaling pathways. In this study, we show the process of how the tightly focused femtosecond-laser induces ROS generation solely in mitochondria at the very beginning and then release to cytosol if the stimulus is intense enough. At certain weak power levels, the laser pulses induce merely moderate Ca2+ release but this is necessary for the laser to generate ROS in mitochondria. Cellular original ROS are also involved with a small contribution. When the power is above a threshold, ROS are then released to cytosol, indicating photodamage overwhelming cellular repair ability. The mechanisms in those two cases are quite different. Those results clarify parts of the mechanism in laser-induced ROS generation. Hence, it is possible to further this optical scheme to provide controllable ROS generation for ROS-related biological researches including mitochondrial diseases and aging.

  10. Ultlra-intense laser-matter interactions at extreme parameters

    SciTech Connect

    Hegellich, Bjorn M

    2010-11-24

    thinnest of these at less than 3nm, i.e. 1/300 of the laser wavelength, are even thinner than the plasma skin depth. This drastically changes the laser-matter interaction physics leading to the emergence of new particle acceleration mechanisms, like Break-Out Afterburner (BOA) Acceleration, driven by a relativistic, kinetic plasma instability or Radiation Pressure Acceleration (RPA), driven by stabilized charge separation. Furthermore, these interactions also produce relativistic high harmonics in forward direction as well as mono-en,ergetic electron pulses which might lend itself as a source for fully coherent Thomson scattering in the mulit-keV regime. In this talk I will present an overview over the laser developments leading to this paradigm change as well as over the theoretical and experimental results following from it. Specifically we were able for the first time to demonstrate BOA acceleration of Carbon ions to up to 0.5 GeV using a laser pulse with {approx}10{sup 20} W/cm{sup 2} intensity and showing the scalability of this mechanism into regimes relevant for Hadron Therapy. We were further able to demonstrate mono-energetic electron break-out from ultrathin targets, as a first step towards a flying mirror.

  11. Spectroscopic monitoring on irradiation-induced formation of AuAg alloy nanoparticles by femtosecond laser

    NASA Astrophysics Data System (ADS)

    Herbani, Yuliati; Nakamura, Takahiro; Sato, Shunichi

    2016-02-01

    The interaction of an intense femtosecond laser pulses with a neat liquid solvent has been known to produce a number of highly reactive species that are useful to induce chemical reactions in the solution through the nonlinear absorption processes. When metal ions are present in the solution, they are assumed to readily reduce by ions, radicals, molecules or excited states generated photolytically from the solvent resulting in the formation of zerovalent metal nanoalloys. If two kinds of metal precursors are involved in a reduction process, the alloying process is expected. In this work, irradiation-induced synthesis of AuAg bimetallic nanoparticle at different laser-pulse energies was examined to investigate the formation mechanism in the presence of NH4OH in the initial solution. At a given laser pulse energy (5.8 mJ/pulse), the time evolution of the UV-visible absorption spectra showed that the formation of AuAg nanoalloys most likely begin with the formation of Ag-riched alloy nanoparticles. As the reduction is started, the absorption spectrum of solution was closer to that of pure Ag nanoparticles. This indicates that the reduction rate of Ag is relatively greater than that of Au nanoparticle in the presence of ammonia. The single peak position then shifts to the red region as the irradiation time increases. After 10 min, the peak positions are between pure silver and gold peaks indicating the alloying process occurs at this stage. At low pulse energy (1.0 mJ/pulse), there was an induction time for several minutes before the absorption is detectable, and hence the alloying process is also delayed (after 20 minutes irradiation). While the formation rate of nanoparticles is more pronounced at high laser pulse energy, the formation yield is relatively the same for both laser pulse energies.

  12. A Method for Monitoring Enamel Erosion Using Laser Irradiated Surfaces and Optical Coherence Tomography

    PubMed Central

    Chan, Kenneth H.; Tom, Henry; Darling, Cynthia L.; Fried, Daniel

    2015-01-01

    Introduction Since optical coherence tomography (OCT) is well suited for measuring small dimensional changes on tooth surfaces, OCT has great potential for monitoring tooth erosion. Previous studies have shown that enamel areas ablated by a carbon dioxide laser manifested lower rates of erosion compared to the non-ablated areas. The purpose of this study was to develop a model to monitor erosion in vitro that could potentially be used in vivo. Methods Thirteen bovine enamel blocks were used in this in vitro study. Each 10 mm × 2 mm block was partitioned into five regions, the central region was unprotected, the adjacent windows were irradiated by a CO2 laser operating at 9.3 μm with a fluence of 2.4J/cm2, and the outermost windows were coated with acid resistant varnish. The samples were exposed to a pH cycling regimen that caused both erosion and subsurface demineralization for 2, 4 and 6 days. The surfaces were scanned using a time-domain polarization sensitive optical coherence tomography (PS-OCT) system and the degree of surface loss (erosion) and the integrated reflectivity with lesion depth was calculated for each window. Results There was a large and significant reduction in the depth of surface loss (erosion) and the severity of demineralization in the areas irradiated by the laser. Conclusion Irradiation of the enamel surface with a pulsed carbon dioxide laser at sub-ablative intensities results in significant inhibition of erosion and demineralization under the acid challenge employed in this study. In addition, these results suggest that it may be feasible to modify regions of the enamel surface using the laser to serve as reference marks to monitor the rate of erosion in vivo. PMID:25147133

  13. Histology of porcine nasal cartilage grafts following Nd:YAG (1320 nm) laser-mediated reshaping: effects of sequential irradiation

    NASA Astrophysics Data System (ADS)

    Kim, Hong K.; Wong, Brian J.; Benton, Hilary P.; Liaw, Lih-Huei L.; Nelson, J. Stuart; Milner, Thomas E.

    2001-07-01

    Mechanically deformed morphologic cartilage grafts undergo temperature dependent stress relaxation during sustained laser irradiation resulting in stable shape changes. In this study, the porcine nasal septal cartilage specimens were evaluated histologically following laser mediated reshaping using H&E. Cartilage specimens were irradiated with light emitted from a Nd:YAG laser (25 W/cm2, 1 = 1.32 mm) while recording simultaneously radiometric surface temperature, internal stress, and backscattered light intensity from a probe laser. Each specimen received one, two, or three sequential laser exposures. The duration of each exposure was determined from real-time measurements of characteristic changes in backscattered light intensity that correlate with accelerated stress relaxation. A five minute time interval between each laser exposures allowed the cartilage specimen to return to thermal equilibrium. Specimens were then fixed in formalin, serially dehydrated in ethanol, embedded in paraffin, and sectioned with a microtome for histologic examination using light microscopy. Large variation in native tissue histology was observed among individual tissue samples, and vascular were identified in several specimens. Large lacunae with shrunken chondrocytes were identified along with cells with pyknotic nuclei, although these histologic observations did not correlate with the degree of laser exposure. These observations are discussed.

  14. A preliminary investigation of cell growth after irradiation using a modulated x-ray intensity pattern

    NASA Astrophysics Data System (ADS)

    Bromley, Regina; Davey, Ross; Oliver, Lyn; Harvie, Rozelle; Baldock, Clive

    2006-08-01

    In this study we have investigated a spatial distribution of cell growth after their irradiation using a modulated x-ray intensity pattern. An A549 human non-small cell lung cancer cell line was grown in a 6-well culture. Two of the wells were the unirradiated control wells, whilst another two wells were irradiated with a modulated x-ray intensity pattern and the third two wells were uniformly irradiated. A number of plates were incubated for various times after irradiation and stained with crystal violet. The spatial distribution of the stained cells within each well was determined by measurement of the crystal violet optical density at multiple positions in the plate using a microplate photospectrometer. The crystal violet optical density for a range of cell densities was measured for the unirradiated well and this correlated with cell viability as determined by the MTT cell viability assay. An exponential dose response curve was measured for A549 cells from the average crystal violet optical density in the uniformly irradiated well up to a dose of 30 Gy. By measuring the crystal violet optical density distribution within a well the spatial distribution of cell growth after irradiation with a modulated x-ray intensity pattern can be plotted. This method can be used for in vitro investigation into the changes in radiation response associated with treatment using intensity modulated radiation therapy (IMRT).

  15. The Irradiation Effect of a Simultaneous Laser and Electron Dual-beam on Void Formation

    PubMed Central

    Yang, Zhanbing; Watanabe, Seiichi; Kato, Takahiko

    2013-01-01

    Randomly distributed lattice point defects such as supersaturated vacancies (SVs) and Frenkel-pairs (FPs, an interstitial and a vacancy) can be simultaneously introduced into the crystal by energetic beam irradiation in outer space and/or nuclear reactors, but their behavior has not been fully understood. Using a high-voltage electron microscope equipped with a laser (laser-HVEM), we show the striking effects of simultaneous laser-electron (photon-electron) dual-beam irradiation on void formation. Our results reveal that during laser-electron sequential irradiation, pre-laser irradiation enhanced void nucleation and subsequent electron irradiation enhanced void growth. However, the laser-electron dual-beam irradiation was analyzed to depress void swelling remarkably because the recombination of SVs and interstitials was enhanced. The results provide insight into the mechanism underlying the dual-beam radiation-induced depression of void swelling in solids. PMID:23383371

  16. Probing Ultrafast Processes in Intense Laser--Matter Interactions

    NASA Astrophysics Data System (ADS)

    Hu, S. X.

    2012-06-01

    This talk reports on computational studies of using sub-femtosecond/attosecond extreme ultraviolet and soft-x-ray pulses to probe ultrafast processes in intense laser interactions with atoms, molecules, and plasmas. By developing and optimizing the finite-element discrete-variable-representation (FEDVR) combined with the real-space product (RSP) algorithm, a powerful computational method is generated, enabling one to explore transient processes in quantum, few-body systems non-perturbatively driven by strong electromagnetic fields. These studies include attosecond photoelectron microscopy of molecular structures, ultrafast probing ion--atom collisions, as well as exploring electron correlations in single-/double-ionization of helium in intense laser fields. Detailed discussions on what has been learned and what can be done in experiments will be presented. This work was partially supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC52-08NA28302, the University of Rochester, and the New York State Energy Research and Development Authority. The support of DOE does not constitute an endorsement by DOE of the views expressed in this article. Computations have been conducted utilizing the Kraken Supercomputer of the National Institute of Computational Sciences (NICS) at Oak Ridge National Laboratory.

  17. Estimates of slope erosion intensity utilizing terrestrial laser scanning

    NASA Astrophysics Data System (ADS)

    Usmanov, B.; Yermolaev, O.; Gafurov, A.

    2015-03-01

    Despite the large variety of methods for estimating slope erosion intensity, it is still difficult to obtain accurate erosion rates. Therefore, our goal was to develop a method to provide accurate estimates of sheet and rill erosion intensities, and evaluate denudation quantities due to abrasion, landslides and talus processes using a high-precision laser scanning system (Trimble® GX). Differential maps between all stages of surveying and TIN-models were built directly on point clouds in "Trimble® RealWorks" software. Inspection and cross-section tools were used for detailed study of ground movements on the slope surface and the development of linear erosion forms. A new method for accurate estimates of the erosion has been developed using terrestrial laser scanning techniques. It makes it possible to assess the denudation-accumulation balance on erosive slopes, determine the dynamics of the volume of material moved on different parts of the slope in various surface runoff events, and identify spatial regularities forming rill washouts.

  18. Laser cooling at low intensity in a strong magnetic field

    NASA Astrophysics Data System (ADS)

    van der Straten, P.; Shang, S.-Q.; Sheehy, B.; Metcalf, H.; Nienhuis, G.

    1993-05-01

    We have studied theoretically and experimentally the effect of a relatively strong magnetic field on sub-Doppler laser cooling in a one-dimensional optical molasses. We used the operator description of laser cooling with the Larmor precession frequency ωZ being much higher than the optical pumping rate. We found velocity-selective resonances (VSR) in the force at velocities vr=nωZ, with n=0,+/-1,+/-2 for both the scattering and redistribution force operators. These depend on the relative direction of the magnetic field and the polarization vectors of the light beams. Analytical results for the force on the atom are obtained in two cases that illustrate the effect of the VSR on the force. These formulas are compared with numerical calculations of the force. We also discovered a redistribution mechanism that relies on the gradient of the eigenstates of the light-shift operator, with eigenvalues that are independent of position so that a ``Sisyphus cooling'' picture does not apply. The theory is compared with many experimental results and excellent agreement is found. We believe that all essential features of laser cooling at low intensity are well described by this operator theory.

  19. Holographic optical elements as laser irradiation sensor components

    NASA Astrophysics Data System (ADS)

    Leib, Kenneth G.; Pernick, Benjamin J.

    1991-12-01

    The use of holographic optical elements (HOEs) to discriminate between coherent irradiation and broadband, noncoherent light has been experimentally demonstrated under adverse scattering and attenuating conditions. As a passive sensor component in a laser irradiation detection system, an HOE can be used in several application areas, e.g., data transmission systems, aircraft warning system, underwater communications, and alignment systems, where wavelength and direction of arrival information can be used. The efficient concentration or focusing of laser light by an HOE onto a detector stage and, of equal importance, the ability to form bright, unique geometric patterns are characteristics that establish the HOE's use as a readily compatible irradiation sensor component. In addition, there is a considerable size and weight advantage over other functionally comparable optical components. Finally, as a passive element, an HOE can fmd use with CW or pulsed illumination. The properties and advantages, pros and cons, of the use of HOEs as sensor elements are discussed in the paper and illustrated in several laboratory experiments and a field test.

  20. Ageing of optical components under laser irradiation at 532nm

    NASA Astrophysics Data System (ADS)

    Becker, S.; Delrive, L.; Bouchut, P.; Andre, B.; Geffraye, F.

    2005-09-01

    The pulsed Laser Induced Damage Threshold (LIDT) of optical components usually reaches several hundreds of MW/cm2. When exposed to laser power several order of magnitude below their LIDT, the optical component lifetime is, by default, considered infinite. Under specific conditions, the accumulation of laser pulses may lead to a contamination of the surface and a degradation of its optical properties and LIDT. In the first order, these phenomena depend on the experimental conditions such as the irradiation time, the laser power, and the environment. In order to better understand the physics emphasizing this degradation, we developed an experimental cell with an in-situ spectroscopic ellipsometry diagnostic. The dry-pumped cell sheltering the sample is associated with a mass spectrometer that enables us to follow the environmental conditions in which we experiment the ageing. Anti-reflection coatings on fused silica were tested under 10 kHz-532 nm laser ageing. We present first results of degradation obtained in these conditions.

  1. Enhancement of peak intensity in a filament core with spatiotemporally focused femtosecond laser pulses

    SciTech Connect

    Zeng Bin; Chu Wei; Li Guihua; Zhang Haisu; Ni Jielei; Gao Hui; Liu Weiwei; Yao Jinping; Cheng Ya; Xu Zhizhan; Chin, See Leang

    2011-12-15

    We demonstrate that the peak intensity in the filament core, which is inherently limited by the intensity clamping effect during femtosecond laser filamentation, can be significantly enhanced using spatiotemporally focused femtosecond laser pulses. In addition, the filament length obtained by spatiotemporally focused femtosecond laser pulses is {approx}25 times shorter than that obtained by a conventional focusing scheme, resulting in improved high spatial resolution.

  2. Measurements of X-ray spectra from irradiated gold foils at the OMEGA Laser facility

    NASA Astrophysics Data System (ADS)

    Davis, Joshua; Keiter, Paul; Drake, Paul; Klein, Sallee; Fein, Jeff

    2014-10-01

    In many HED systems high intensity x-rays can be used to measure plasma properties such as density and temperature. At the OMEGA laser facility, these X-rays are produced by irradiating a metal foil with high-intensity lasers, which heats the foil and causes it to act as a quasi-continuum x-ray source for radiography or absorption spectroscopy. As this emission is quasi-continuous and the transmission of x-rays through a material varies with photon energy a well-characterized x-ray source is vital. Therefore, in order to optimize diagnostics reliant upon x-rays it is necessary to gain a better understanding of how the x-ray emission from these targets varies over time and varying beam energy. We will present experimental results studying the effect that beam energy and pulse length have on M-band and sub-keV x-ray emission generated from a 5 μm thick gold disk using time-resolved spectroscopy and a Henway crystal spectrometer. This work is funded by the U.S. Department of Energy, through the NNSA-DS and SC-OFES Joint Program in High-Energy-Density Laboratory Plasmas, Grant Number DE-NA0001840, and the National Laser User Facility Program, Grant Number DE-NA0000850, and through the Laboratory for Laser Energetics, University of Rochester by the NNSA/OICF under Cooperative Agreement No. DE-FC52-08NA28302.

  3. Generation of high-quality mega-electron volt proton beams with intense-laser-driven nanotube accelerator

    SciTech Connect

    Murakami, M.; Tanaka, M.

    2013-04-22

    An ion acceleration scheme using carbon nanotubes (CNTs) is proposed, in which embedded fragments of low-Z materials are irradiated by an ultrashort intense laser to eject substantial numbers of electrons. Due to the resultant characteristic electrostatic field, the nanotube and embedded materials play the roles of the barrel and bullets of a gun, respectively, to produce highly collimated and quasimonoenergetic ion beams. Three-dimensional particle simulations, that take all the two-body Coulomb interactions into account, demonstrate generation of quasimonoenergetic MeV-order proton beams using nanometer-size CNT under a super-intense electrostatic field {approx}10{sup 14} V m{sup -1}.

  4. Air leak seal for lung dissection plane with diode laser irradiation: monitoring heat-denature with auto-fluorescence

    NASA Astrophysics Data System (ADS)

    Gotoh, Maya; Arai, Tsunenori

    2008-02-01

    We studied the monitoring of heat-denature by autofluorescence spectrum from lung dissection plane during laser air leak sealing procedure. In order to seal the air leakage from lung in thoracotomy, we proposed novel laser sealing method with the combination of the diode laser (810nm wavelength) irradiation and indocyanine green staining (peak absorption wavelength: 805 nm). This sealing method is expected to preserve the postoperative ventilatory capacity and achieve minimally invasive surgery. We previously reported that this laser sealing only requires thin sealing margin (less than 300 μm in thickness) compared with that of the suturing or stapling. The most serious issue on the laser air leak sealing might be re-air-leakage due to rigid surface layer caused by excessive heat-denature, such as carbonization. We should achieve laser air leak sealing minimizing the degree of heat denature. Dissection planes of isolated porcine lung with /without the diode laser irradiation were prepared as samples. We measured the auto-fluorescence from these samples using a spectrometer. When the diode laser was irradiated with 400J/cm2, the surface of diode laser irradiated lung was fully carbonized. The ration of auto-fluorescence emission of 450nm / 500 nm, with 280 nm excitation wavelength was decreased less tha 50 % of initial value. That of 600 nm / 500 nm was increased over 700 % of initial value. The decreasing of the 450 nm auto-fluorescence intensity might be attributed to the heat-denaturing of the interstitial collagen in lung. However, increasing of the 600 nm didn't specify the origins, we suppose it might be originated from heat-denature substance, like carbonization. We could establish the useful monitoring for lung heat-denaturing with simple methodology. We think the auto-fluorescence measurement can be helpful not only for understanding the sealing mechanism, but also for controlling the degree of heat-denaturing during the procedure.

  5. Modification of structural and optical properties of polyvinyl alcohol/polyethylene glycol thin film by laser irradiation

    NASA Astrophysics Data System (ADS)

    Nouh, S. A.; Benthami, K.; Abutalib, M. M.

    2016-02-01

    The effect of infrared laser irradiation on the structural and the optical properties of polyvinyl alcohol/polyethylene glycol (PVA/PEG) co-polymer has been investigated. Thin films of PVA/PEG (nearly 50 µm thickness) were irradiated up to 15 J/cm2 of Ga-As laser pulses of 904 nm, 5 W power, and 200-ns pulse duration. The resultant effect of laser irradiation on the structural properties of PVA/PEG has been investigated using X-ray diffraction and Fourier transform infrared spectroscopy (FTIR). Further, the refractive index and the color difference between the exposed samples and the pristine have been studied. FTIR spectroscopy showed that the PVA/PEG samples exhibited degradation under the effect of laser irradiation up to 9 J/cm2, where crosslinking started and continued until 15 J/cm2. The refractive index had a minimum value of 1.5020 at 9 J/cm2, accompanied by a high degree of ordering and maximum value of 1.5640 at 15 J/cm2, with an increase in disordering character due to the degradation and crosslinking formation inside the sample, respectively. Moreover, the color intensity ΔE was greatly increased with increasing the laser fluence, accompanied by a significant increase in the yellow color component.

  6. Lymphoid tissue during irradiation of tumors with pulsing laser's radiation

    NASA Astrophysics Data System (ADS)

    Moskalik, Konstantin G.

    2002-06-01

    The structure of the regional lymph nodes and the thymus was studied in the experiments upon the mice of the line C57BL with the subcutaneous interwoven melanoma B16 in the periods from one hour to 12 days after the radiation of melanoma with one irradiation impulse of the Nd laser with the energy density of 400 J/cm2. During the first 3 days after the irradiation of tumor with laser radiation the impoverishment of lymph nodes and thymus with lymphocytes takes place because of their intensified migration from these organs to the blood channel. Then one can see the restoration of the lymph nodes and thymus structure. The restoration of lymphopoiesis in the lymph nodes went on in the first place because of the poiesis in the follicles which consist of B-lymphocytes. Consequently, the lymphoid tissue plays a great role in the reorganization of the immunological status of the organism. Reorganization can be seen during the treatment of tumors with laser radiation, and it takes place in the first instance because of the reinforcement of the humoral immunity.

  7. Laser-induced breakdown spectroscopy with laser irradiation resonant with vibrational transitions

    SciTech Connect

    Khachatrian, Ani; Dagdigian, Paul J.

    2010-05-01

    An investigation of laser-induced breakdown spectroscopy (LIBS) of polymers, both in bulk form and spin coated on Si wafers, with laser irradiation in the mid-infrared spectral region is presented. Of particular interest is whether the LIBS signals are enhanced when the laser wavelength is resonant with a fundamental vibrational transition of the polymer. Significant increases in the LIBS signals were observed for irradiation on hydride stretch fundamental transitions, and the magnitude of the enhancement showed a strong dependence on the mode excited. The role of the substrate was investigated by comparison of results for bulk and spin-coated samples. The polymers investigated were Nylon 12 and poly(vinyl alcohol-co-ethylene).

  8. Observation and analysis of structural changes in fused silica by continuous irradiation with femtosecond laser light having an energy density below the laser-induced damage threshold.

    PubMed

    Nomura, Wataru; Kawazoe, Tadashi; Yatsui, Takashi; Naruse, Makoto; Ohtsu, Motoichi

    2014-01-01

    The laser-induced damage threshold (LIDT) is widely used as an index for evaluating an optical component's resistance to laser light. However, a degradation in the performance of an optical component is also caused by continuous irradiation with laser light having an energy density below the LIDT. Therefore, here we focused on the degradation in performance of an optical component caused by continuous irradiation with femtosecond laser light having a low energy density, i.e., laser-induced degradation. We performed an in situ observation and analysis of an increase in scattering light intensity in fused silica substrates. In experiments conducted using a pulsed laser with a wavelength of 800 nm, a pulse width of 160 fs and pulse repetition rate of 1 kHz, we found that the scattered light intensity increased starting from a specific accumulated fluence, namely, that the laser-induced degradation had a threshold. We evaluated the threshold fluence F t as 6.27 J/cm(2) and 9.21 J/cm(2) for the fused silica substrates with surface roughnesses of 0.20 nm and 0.13 nm in R a value, respectively, showing that the threshold decreased as the surface roughness increased. In addition, we found that the reflected light spectrum changed as degradation proceeded. We analyzed the details of the degradation by measuring instantaneous reflectance changes with a pump-probe method; we observed an increase in the generation probability of photogenerated carriers in a degraded silica substrate and a damaged silica substrate and observed a Raman signal originating from a specific molecular structure of silica. From these findings, we concluded that compositional changes in the molecular structure occurred during degradation due to femtosecond laser irradiation having an energy density below the LIDT. PMID:25247116

  9. Laser ablation of liquid surface in air induced by laser irradiation through liquid medium

    NASA Astrophysics Data System (ADS)

    Utsunomiya, Yuji; Kajiwara, Takashi; Nishiyama, Takashi; Nagayama, Kunihito; Kubota, Shiro; Nakahara, Motonao

    2010-10-01

    The pulse laser ablation of a liquid surface in air when induced by laser irradiation through a liquid medium has been experimentally investigated. A supersonic liquid jet is observed at the liquid-air interface. The liquid surface layer is driven by a plasma plume that is produced by laser ablation at the layer, resulting in a liquid jet. This phenomenon occurs only when an Nd:YAG laser pulse (wavelength: 1064 nm) is focused from the liquid onto air at a low fluence of 20 J/cm2. In this case, as Fresnel’s law shows, the incident and reflected electric fields near the liquid surface layer are superposed constructively. In contrast, when the incident laser is focused from air onto the liquid, a liquid jet is produced only at an extremely high fluence, several times larger than that in the former case. The similarities and differences in the liquid jets and atomization processes are studied for several liquid samples, including water, ethanol, and vacuum oil. The laser ablation of the liquid surface is found to depend on the incident laser energy and laser fluence. A pulse laser light source and high-resolution film are required to observe the detailed structure of a liquid jet.

  10. Analytical model for interaction of short intense laser pulse with solid target

    SciTech Connect

    Luan, S. X.; Ma, G. J.; Yu, Wei; Yu, M. Y.; Zhang, Q. J.; Sheng, Z. M.; Murakami, M.

    2011-04-15

    A simple but comprehensive two-dimensional analytical model for the interaction of a normally incident short intense laser pulse with a solid-density plasma is proposed. Electron cavitation near the target surface by the laser ponderomotive force induces a strong local electrostatic charge-separation field. The cavitation makes possible mode conversion of the laser light into longitudinal electron oscillation at laser frequency, even for initial normal incidence of laser pulse. The intense charge-separation field in the cavity can significantly enhance the laser induced uxB electron oscillation at twice laser frequency to density levels even higher than that of the initial target.

  11. LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Dynamics of splashing of molten metals during irradiation with single CO2 laser pulses

    NASA Astrophysics Data System (ADS)

    Arutyunyan, R. V.; Baranov, V. Yu; Bol'shov, Leonid A.; Dolgov, V. A.; Malyuta, D. D.; Mezhevov, V. S.; Semak, V. V.

    1988-03-01

    An experimental investigation was made of the dynamics of the loss of the melt as a result of interaction with single-mode CO2 laser radiation pulses of 5-35 μs duration. The dynamics of splashing of the melt during irradiation with short pulses characterized by a Gaussian intensity distribution differed from that predicted by models in which the distribution of the vapor pressure was assumed to be radially homogeneous.

  12. Low-fluence carbon dioxide laser irradiation of lentigines

    SciTech Connect

    Dover, J.S.; Smoller, B.R.; Stern, R.S.; Rosen, S.; Arndt, K.A.

    1988-08-01

    Low-fluence carbon dioxide (CO2) laser irradiation of skin has previously been shown to induce damage limited primarily to the epidermis. To evaluate whether this technique was therapeutically effective for pigmented epidermal lesions, ten lentigines caused by methoxsalen and ultraviolet light therapy were treated in one patient using the CO2 laser at fluences ranging from 3.0 to 7.7 J/cm2 for 0.1-s exposures with 4.5-mm spot size. Based on substantial clearing in seven of ten lesions treated, 146 solar lentigines were treated in five patients at fluences of 3.0, 3.7, or 4.4 J/cm2. Biopsies were performed on a total of 30 lesions immediately and 24 hours, seven days, and six weeks after irradiation. Of 125 lesions followed up clinically for six weeks, 12 cleared completely, 81 lightened substantially, and 28 remained unchanged. Only two demonstrated atrophic change. Hyperpigmentation or hypopigmentation did not occur. All lesions that improved had been treated at 3.7 or 4.4 J/cm2. Immediate histologic injury consisted of vacuolar and spindly change and subsequent vesiculation limited to the basilar epidermis. Twenty-four hours later there was epidermal necrosis with regeneration, 0.1 mm of dermal basophilia and stromal condensation, and a mild inflammatory infiltrate. These alterations were dose-dependent, with near complete epidermal necrosis and superficial dermal involvement at the highest fluence, and only focal epidermal necrosis at the lowest. At seven days, epidermal regeneration was complete with traces of melanin remaining in keratinocytes. Melanophages first appeared at seven days and persisted at six weeks, by which time the inflammatory infiltrate had cleared. No lentiginous proliferation was evident and epidermal pigmentation had become normal. Low-fluence CO2 laser irradiation is an effective means of damaging the epidermis with only minimal dermal change.

  13. Measurements of the divergence of fast electrons in laser-irradiated spherical targets

    SciTech Connect

    Yaakobi, B.; Solodov, A. A.; Myatt, J. F.; Delettrez, J. A.; Stoeckl, C.; Froula, D. H.

    2013-09-15

    In recent experiments using directly driven spherical targets on the OMEGA laser system, the energy in fast electrons was found to reach ∼1% of the laser energy at an irradiance of ∼1.1 × 10{sup 15} W/cm{sup 2}. The fraction of these fast electrons absorbed in the compressed fuel shell depends on their angular divergence. This paper describes measurements of this divergence deduced from a series of shots where Mo-coated shells of increasing diameter (D) were suspended within an outer CH shell. The intensity of the Mo–Kα line and the hard x-ray radiation were found to increase approximately as ∼D{sup 2}, indicating wide divergence of the fast electrons. Alternative interpretations of these results (electron scattering, radiation excitation of Kα, and an electric field due to return current) are shown to be unimportant.

  14. Nanoscale Ultradense Z -Pinch Formation from Laser-Irradiated Nanowire Arrays

    NASA Astrophysics Data System (ADS)

    Kaymak, Vural; Pukhov, Alexander; Shlyaptsev, Vyacheslav N.; Rocca, Jorge J.

    2016-07-01

    We show that ultradense Z pinches with nanoscale dimensions can be generated by irradiating aligned nanowires with femtosecond laser pulses of relativistic intensity. Using fully three-dimensional relativistic particle-in-cell simulations, we demonstrate that the laser pulse drives a forward electron current in the area around the wires. This forward current induces return current densities of ˜0.1 GA per μ m2 through the wires. The resulting strong, quasistatic, self-generated azimuthal magnetic field pinches the nanowires into hot plasmas with a peak electron density of >9 ×1 024 cm-3 , exceeding 1000 times the critical density. Arrays of these new ultradense nanopinches can be expected to lead to efficient microfusion and other applications.

  15. Direct experimental evidence of back-surface ion acceleration from laser-irradiated gold foils.

    PubMed

    Allen, Matthew; Patel, Pravesh K; Mackinnon, Andrew; Price, Dwight; Wilks, Scott; Morse, Edward

    2004-12-31

    Au foils were irradiated with a 100-TW, 100-fs laser at intensities greater than 10(20) W/cm2 producing proton beams with a total yield of approximately 10(11) and maximum proton energy of >9 MeV. Removing contamination from the back surface of Au foils with an Ar-ion sputter gun reduced the total yield of accelerated protons to less than 1% of the yield observed without removing contamination. Removing contamination from the front surface (laser-interaction side) of the target had no observable effect on the proton beam. We present a one-dimensional particle-in-cell simulation that models the experiment. Both experimental and simulation results are consistent with the back-surface acceleration mechanism described in the text. PMID:15697987

  16. Preparation of nanodiamonds by laser irradiation of graphite

    NASA Astrophysics Data System (ADS)

    Sun, Jing; Lei, Yiwen; Zhai, Qi; Yang, Xing; Yang, Jing; Du, Xiwen

    2005-05-01

    Graphite powders were irradiated by pulsed laser at room temperature and normal pressure and then boiled in perchloric acid. Samples were characterized by high-resolution transmission electron microscopy (HRTEM), electron diffraction pattern (EDP), X-ray diffraction (XRD) pattern, and Raman spectroscopy. The analyses on the HRTEM images, EDP, and XRD show that the diamond particles with a size of about 5 nm are obtained. The shifting and broadening of the diamond peak in Raman spectrum indicate that there are high defect density and residual internal stress in synthetic diamond.

  17. Ultra-Intense Laser Pulse Propagation in Gas and Plasma

    SciTech Connect

    Antonsen, T. M.

    2004-10-26

    It is proposed here to continue their program in the development of theories and models capable of describing the varied phenomena expected to influence the propagation of ultra-intense, ultra-short laser pulses with particular emphasis on guided propagation. This program builds upon expertise already developed over the years through collaborations with the NSF funded experimental effort lead by Professor Howard Milchberg here at Maryland, and in addition the research group at the Ecole Polytechnique in France. As in the past, close coupling between theory and experiment will continue. The main effort of the proposed research will center on the development of computational models and analytic theories of intense laser pulse propagation and guiding structures. In particular, they will use their simulation code WAKE to study propagation in plasma channels, in dielectric capillaries and in gases where self focusing is important. At present this code simulates the two-dimensional propagation (radial coordinate, axial coordinate and time) of short pulses in gas/plasma media. The plasma is treated either as an ensemble of particles which respond to the ponderomotive force of the laser and the self consistent electric and magnetic fields created in the wake of pulse or as a fluid. the plasma particle motion is treated kinetically and relativistically allowing for study of intense pulses that result in complete cavitation of the plasma. The gas is treated as a nonlinear medium with rate equations describing the various stages of ionization. A number of important physics issues will be addressed during the program. These include (1) studies of propagation in plasma channels, (2) investigation of plasma channel nonuniformities caused by parametric excitation of channel modes, (3) propagation in dielectric capillaries including harmonic generation and ionization scattering, (4) self guided propagation in gas, (5) studies of the ionization scattering instability recently

  18. The Effects of Laser Irradiation of Cartilage on Chondrocyte Gene Expression and the Collagen Matrix

    PubMed Central

    Holden, Paul K.; Li, Chao; Da Costa, Victor; Sun, Chung-Ho; Bryant, Susan V.; Gardiner, David M.; Wong, Brian J.F.

    2014-01-01

    Objectives Laser reshaping of cartilage is an emerging technology aimed at replacing conventional techniques for aesthetic and reconstructive surgery. Little is known about the mechanisms of wound healing following the photothermal heating during laser reshaping and, ultimately, how collagen remodels in the irradiated tissue. Healthy hyaline and elastic cartilage as found in the ear, nose, larynx, and trachea does not express collagen type I which is characteristic of fibro-cartilage and scar tissue. The aim of the study was to determine if collagen I and II gene expression occurs within laser irradiated rabbit septal cartilage. Methods Nasal septum harvested from freshly euthanized New Zealand White rabbits were irradiated with an Nd:YAG laser. After 2 weeks in culture, the laser spot and surrounding non-irradiated regions were imaged using immunofluorescence staining and evaluated using reverse transcription polymerase chain reaction (RT-PCR) to determine the presence of collagen I and II, and ascertain collagen I and II gene expression, respectively. Results All laser irradiated specimens showed a cessation in collagen II gene expression within the center of the laser spot. Collagen II was expressed in the surrounding region encircling the laser spot and within the non-irradiated periphery in all specimens. Immunohistochemistry identified only type II collagen. Neither collagen I gene expression nor immunoreactivity were identified in any specimens regardless or irradiation parameters. Conclusions Laser irradiation of rabbit septal cartilage using dosimetry parameters similar to those used in laser reshaping does not result in the detection of either collagen I gene expression or immunoreactivity. Only collagen type II was noted after laser exposure in vitro following cell culture, which suggests that the cellular response to laser irradiation is distinct from that observed in conventional wound healing. Laser irradiation of cartilage can leave an intact

  19. Deterioration of performance of neutron moderators under intense irradiation

    SciTech Connect

    Carpenter, J.M.; Cudrnak, S.S.; DeCusatis, C.M.

    1986-01-01

    In pulsed neutron sources, fixed moderators such as polyethylene and solid methane slow down fast (MeV) neutrons from the primary source to energies of use for spectroscopy (less than or equal to10 eV). Radiation-induced changes in their composition alter their spectral and pulse characteristics. We report the results of fitting time-average spectra from polyethylene and solid methane moderators in Argonne's Intense Pulsed Neutron Source as a function of total fast-neutron radiation dose. The thermal-to-epithermal flux ratio varies most significantly, while the Maxwellian energy and the parameters describing the epithermal component change only slightly. We have used modified forms of Westcott's joining function for this purpose. We provide an integral of the spectrum that is useful for determining the delayed neutron background.

  20. Explosive Boiling In Carbon Target Irradiated By Third Harmonic Of Nd :YAG Laser

    SciTech Connect

    Yahiaoui, K.; Kerdja, T.; Malek, S.

    2008-09-23

    In order to identify the physical phenomena responsible to the formation of droplets onto thin films grown during laser ablation, and to correlate between the appearance of those droplets versus the laser flux, we have measured the amount of ejected matter for carbon target irradiated by a third harmonic of Nd:YAG laser by changing laser flux. The measurement was achieved by a quartz microbalance placed in front of the target. The obtained results show at first a linear increase of the ejected material followed by a saturation behavior, and then an abrupt increase of the ablated mass beyond a laser Intensity of 3,64x10{sup 10} W/cm{sup 2}. This increasing is assigned to the homogeneous nucleation of bubbles in a layer of the molten material, also called phase explosion, the surface temperature of the target will approaches the critical thermodynamic temperature (T{sub tc}). We have also measured time-of-flight (TOF) distributions of positives ions of carbons in the plasma using a charge collector. The TOF signals have been fitted with a shifted Maxwellian distribution function. This has allowed us to estimate the critical temperature T{sub tc} of the material.

  1. Anomalous transport of Sb in laser irradiated Ge

    SciTech Connect

    Bruno, E.; Scapellato, G. G.; Boninelli, S.; Priolo, F.; Privitera, V.; La Magna, A.; Cuscuna, M.; Fortunato, G.; Napolitani, E.

    2012-10-22

    Excimer laser annealing is shown to be very promising to promote Sb incorporation in Ge up to concentrations as high as 1 Multiplication-Sign 10{sup 21} at./cm{sup 3}. However, we demonstrate that when Ge is melted by laser irradiation, a high excess of vacancies is generated in the molten region. These vacancies induce Sb electrical deactivation at the melt depth through the formation of Sb{sub m}-V{sub n} complexes that act as a sink for further Sb atoms, even leading Sb to back-diffuse towards the surface, against the concentration gradient. These results are fundamental for the realization of new generation Ge-based micro and optoelectronic devices.

  2. Thermal behavior of the STM tip under laser irradiation

    NASA Astrophysics Data System (ADS)

    Reilly, Christopher G.

    This thesis discusses the thermal behavior of the STM tip under laser irradiation. The thermal expansion of the tip was researched with varying laser spot size, frequency, location, and power. In order to determine the thermal expansion of the STM tip, the behavior in both the time and frequency domain were investigated. By employing the FFT analysis, the noise of the thermal behavior in the frequency domain was greatly reduced when compared to the time domain behavior, allowing for higher resolution expansions. With noise reduced, a thermal expansion of 1 nm, equating to a 0.03 K average temperature rise across the tip was found. Besides the heating and expansion of the STM tip, the thermal diffusivity of the PtIr STM tip was calculated using the TET and Characteristic Point methods, and found to be within 3% of the expected value.

  3. Reducing wall plasma expansion with gold foam irradiated by laser

    NASA Astrophysics Data System (ADS)

    Zhang, Lu; Ding, Yongkun; Jiang, Shaoen; Yang, Jiamin; Li, Hang; Kuang, Longyu; Lin, Zhiwei; Jing, Longfei; Li, Liling; Deng, Bo; Yuan, Zheng; Chen, Tao; Yuan, Guanghui; Tan, Xiulan; Li, Ping

    2015-11-01

    The experimental study on the expanding plasma movement of low-density gold foam (˜1% solid density) irradiated by a high power laser is reported in this paper. Experiments were conducted using the SG-III prototype laser. Compared to solid gold with 19.3 g/cc density, the velocities of X-ray emission fronts moving off the wall are much smaller for gold foam with 0.3 g/cc density. Theoretical analysis and MULTI 1D simulation results also show less plasma blow-off, and that the density contour movement velocities of gold foam are smaller than those of solid gold, agreeing with experimental results. These results indicate that foam walls have advantages in symmetry control and lowering plasma fill when used in ignition hohlraum.

  4. Reducing wall plasma expansion with gold foam irradiated by laser

    SciTech Connect

    Zhang, Lu; Ding, Yongkun Jiang, Shaoen Yang, Jiamin; Li, Hang; Kuang, Longyu; Lin, Zhiwei; Jing, Longfei; Li, Liling; Deng, Bo; Yuan, Zheng; Chen, Tao; Yuan, Guanghui; Tan, Xiulan; Li, Ping

    2015-11-15

    The experimental study on the expanding plasma movement of low-density gold foam (∼1% solid density) irradiated by a high power laser is reported in this paper. Experiments were conducted using the SG-III prototype laser. Compared to solid gold with 19.3 g/cc density, the velocities of X-ray emission fronts moving off the wall are much smaller for gold foam with 0.3 g/cc density. Theoretical analysis and MULTI 1D simulation results also show less plasma blow-off, and that the density contour movement velocities of gold foam are smaller than those of solid gold, agreeing with experimental results. These results indicate that foam walls have advantages in symmetry control and lowering plasma fill when used in ignition hohlraum.

  5. Investigation on the Influence of Different Laser Beam Intensity Distributions on Keyhole Geometry During Laser Welding

    NASA Astrophysics Data System (ADS)

    Volpp, J.

    An analytical quasi-static model of the keyhole during laser deep penetration welding is introduced. This model is used to calculate the keyhole geometry depending on spatial laser beam intensity. Keyhole shapes can be found solving the energy and pressure equations. All necessary physical effects like Fresnel and plasma absorption, heat conduction and vaporization are implemented in the model. For evaluation a Gaussian and a top hat beam profile were used. Experimental measurements of the keyhole shape using copper inlays in aluminum base material show good agreement with the results of the modeling.

  6. Persistent Conductivity in Post-Growth Doped ZnO Films Following Pulsed UV Laser Irradiation

    SciTech Connect

    Wang, Lisa J.; Exarhos, Gregory J.

    2010-12-30

    Solution and rf sputter deposited doped ZnO films were subjected to cumulative 4-nsec pulses of 355 nm light from a pulsed Nd:YAG laser at fluences between 5 and 150 mJ/cm2. Film densification, change in refractive index, and an increase in conductivity were observed following room temperature irradiation in air, a carbon monoxide reducing environment, or under vacuum. At fluences between 20 and 80 mJ/cm2, the films did not damage catastrophically under irradiation and high visible transparency persisted. The increase in conductivity is attributed to creation of oxygen vacancies and subsequent promotion of free carriers into the conduction band. Effects were most pronounced in films treated in vacuum. All treated films became insulating again upon equilibration in air at room temperature after several days. Films were characterized by means of UV-VIS-NIR transmission spectroscopy, Raman spectroscopy and Hall measurements. Analysis of interference fringes in measured transmission spectra allowed evaluation of optical properties. Raman measurements showed an increase of LO mode intensity with respect to TO mode intensity as the films became more conducting in accord with previous work. Results of this study are not only important for continued development of transparent conducting oxides, but also provide compelling evidence for the role of free carriers as initiators of the laser damage process in these wide bandgap metal oxide films.

  7. Time-dependent intensity and phase measurements of ultrashort laser pulses as short as 10 fs

    SciTech Connect

    DeLong, K.W.; Fittinghoff, D.N.; Ladera, C.L.; Trebino, R.; Taft, G.; Rundquist, A.; Murnane, M.M.; Kapteyn, H.C.; Christov, I.P.

    1995-05-01

    Frequency-Resolved Optical Gating (FROG) measures the time-dependent intensity and phase of an ultrashort laser pulse. Using FROG, we have tested theories for the operation of sub{minus}10 fs laser oscillators.

  8. Resonant absorption effects induced by polarized laser light irradiating thin foils in the TNSA regime of ion acceleration

    NASA Astrophysics Data System (ADS)

    Torrisi, L.; Badziak, J.; Rosinski, M.; Zaras-Szydlowska, A.; Pfeifer, M.; Torrisi, A.

    2016-04-01

    Thin foils were irradiated by short pulsed lasers at intensities of 1016‑19W/cm2 in order to produce non-equilibrium plasmas and ion acceleration from the target-normal-sheath-acceleration (TNSA) regime. Ion acceleration in forward direction was measured by SiC detectors and ion collectors used in the time-of-flight configuration. Laser irradiations were employed using p-polarized light at different incidence angles with respect to the target surface and at different focal distances from the target surface. Measurements demonstrate that resonant absorption effects, due to the plasma wave excitations, enhance the plasma temperature and the ion acceleration with respect to those performed without to use of p-polarized light. Dependences of the ion flux characteristics on the laser energy, wavelength, focal distance and incidence angle will be reported and discussed.

  9. Far-Field Patterns from Dye-Doped Planar-Aligned Nematic Liquid Crystals Under nanosecond Laser Irradiation

    SciTech Connect

    Lukishova, S.G.; Lepeshkin, N.; Boyd, R.W.; Marshall, K.L.

    2006-08-18

    High-definition patterns were observed under 10-Hz-pulse-repetition-rate, nanosecond laser irradiation of azodye-doped planar-nematic liquid crystal layers at incident intensities I ~ 5-10 MW/cm^2 in a single beam configuration and without any feedback involved. An incident polarization parallel to the nematic director was used. Under periodic pulsed laser irradiation, far-field beam patterns at the output of a dye-doped liquid crystal layer changed kaleidoscopically from rings and stripes to multiple hexagons. This pattern-formation regime had a buildup time of several seconds to minutes. We explain the observed effect by diffraction of the laser beam on light-induced micrometer-size inhomogeneities inside the liquid crystal layer with absorption and refraction properties different from the surrounding area. Possible mechanisms of the formation of the inhomogeneities are discussed.

  10. Analytical model for calibrating laser intensity in strong-field-ionization experiments

    NASA Astrophysics Data System (ADS)

    Zhao, Song-Feng; Le, Anh-Thu; Jin, Cheng; Wang, Xu; Lin, C. D.

    2016-02-01

    The interaction of an intense laser pulse with atoms and molecules depends extremely nonlinearly on the laser intensity. Yet experimentally there still exists no simple reliable methods for determining the peak laser intensity within the focused volume. Here we present a simple method, based on an improved Perelomov-Popov-Terent'ev model, that would allow the calibration of laser intensities from the measured ionization signals of atoms or molecules. The model is first examined by comparing ionization probabilities (or signals) of atoms and several simple diatomic molecules with those from solving the time-dependent Schrödinger equation. We then show the possibility of using this method to calibrate laser intensities for atoms, diatomic molecules as well as large polyatomic molecules, for laser intensities from the multiphoton ionization to tunneling ionization regimes.

  11. The Intravenous Laser Blood Irradiation in Chronic Pain and Fibromyalgia

    PubMed Central

    Momenzadeh, Sirous; Abbasi, Mohammadzaki; Ebadifar, Asghar; Aryani, Mohammadreza; Bayrami, Jafar; Nematollahi, Fatemeh

    2015-01-01

    Intravenous laser blood irradiation was first introduced into therapy by the Soviet scientists EN.Meschalkin and VS.Sergiewski in 1981. Originally this method was developed for the treatment of cardiovascular diseases. Improvement of rheologic properties of the blood as well as improvement of microcirculation and reduction of the area of infarction has been proved. Further, reduction of dysrhythmia and sudden cardiac death was achieved. At first, only the Helium-Neon laser (632.8 nm) was used in this therapy. For that, a power of 1-3mW and a period of exposure of 20-60 minutes were applied. The treatments were carried out once or twice a day up to ten appointments in all1. In the years after, many, and for the most part Russian studies showed that helium-neon laser had various effects on many organs and on the hematologic and immunologic system. The studies were published mainly in Russian which were little known in the West because of decades of political separation, and were regarded with disapproval. Besides clinical research and application for patients, the cell biological basis was developed by the Estonian cell biologist Tiina Karu at the same time. An abstract is to be found in her work "The Science of Low-Power Laser-Therapy" PMID:25699161

  12. The intravenous laser blood irradiation in chronic pain and fibromyalgia.

    PubMed

    Momenzadeh, Sirous; Abbasi, Mohammadzaki; Ebadifar, Asghar; Aryani, Mohammadreza; Bayrami, Jafar; Nematollahi, Fatemeh

    2015-01-01

    Intravenous laser blood irradiation was first introduced into therapy by the Soviet scientists EN.Meschalkin and VS.Sergiewski in 1981. Originally this method was developed for the treatment of cardiovascular diseases. Improvement of rheologic properties of the blood as well as improvement of microcirculation and reduction of the area of infarction has been proved. Further, reduction of dysrhythmia and sudden cardiac death was achieved. At first, only the Helium-Neon laser (632.8 nm) was used in this therapy. For that, a power of 1-3mW and a period of exposure of 20-60 minutes were applied. The treatments were carried out once or twice a day up to ten appointments in all1. In the years after, many, and for the most part Russian studies showed that helium-neon laser had various effects on many organs and on the hematologic and immunologic system. The studies were published mainly in Russian which were little known in the West because of decades of political separation, and were regarded with disapproval. Besides clinical research and application for patients, the cell biological basis was developed by the Estonian cell biologist Tiina Karu at the same time. An abstract is to be found in her work "The Science of Low-Power Laser-Therapy" PMID:25699161

  13. Coherence effects in the ultra-intense laser-induced ultrafast response of complex atoms

    NASA Astrophysics Data System (ADS)

    Li, Yongqiang; Yuan, Jianmin

    2016-05-01

    Both coherent pumping and energy relaxation play important roles in understanding physical processes of ultra-intense coherent light-matter interactions. Here, using a large-scale quantum master equation approach, we describe dynamical processes of practical open quantum systems driven by both coherent and stochastic interactions. As examples, two typical cases of light-matter interactions are studied. First, we investigate coherent dynamics of inner-shell electrons of a neon gas irradiated by a high intensity X-ray laser along with vast number of decaying channels. In these single-photon dominated processes, we find that, due to coherence-induced Rabi oscillations and power broadening effects, the photon absorptions of a neon gas can be suppressed resulting in differences in ionization processes and final ion-stage distributions. Second, we take helium as an example of multi-photon and multichannel interference dominated electron dynamics, by investigating the transient absorption of an isolated atto-second pulse in the presence of a femto-second infrared laser pulse.

  14. Simulation of the thermal effect of laser irradiation to optimize laser epilation

    NASA Astrophysics Data System (ADS)

    Russ, Detlef; Kienle, Alwin; Falkenstein, Werner; Steiner, Rudolf W.

    2000-11-01

    For hair removal commonly lasers are used with wavelengths being selectively absorbed by melanin .As a consequence, laser radiation leads to an increase of the temperature not only in melanin containing structures of the hair but also in the epidermis. Therefore, we simulated and studied the laser induced temperature development in tissue for various laser wavelengths and various pulse profiles. Modifying the beam parameters can improve the selectivity of the method. Monte- Carlo-Simulations were used to calculate light absorption in dermal structures, considering the tissue specific optical properties. The thermal diffusion in tissue was calculated by a finite difference method. The biological reaction due to the temperature rise was determined by an Arrhenius formalism and depends on temperature and time of laser-tissue interaction. The simulation program allows to calculate the temperature distribution and thermal damage for various temporal pulse profiles, fluence rates and irradiation geometries. Superficial cooling has an important influence and has been considered in the calculations. The results of our simulations for various laser types show differences in the thermal reaction which can be used to optimize the treatment modalities. The potential and limits of laser epilation can be estimated from these results. For example, a series of laser pulses has some advantages compared to a longer single pulse.

  15. Basic studies on intravascular low-intensity laser therapy

    NASA Astrophysics Data System (ADS)

    Liu, Timon Cheng-Yi; Duan, Rui; Wang, Shuang-Xi; Liu, Jiang; Cui, Li-Ping; Jin, Hua; Liu, Song-Hao

    2006-09-01

    Intravascular low intensity laser therapy (ILILT) was originally put forward in USA in 1982, but popularized in Russia in 1980s and in China in 1990s, respectively. A randomized placebo-controlled study has shown ILILT clinical efficacy in patients suffering from rheumatoid arthritis. As Chinese therapeutic applications of ILILT were the most widely in the world, its basic research, such as intracellular signal transduction research, blood research in vitro, animal blood research in vivo, human blood research in vivo and traditional Chinese medicine research, was also very progressive in China. Its basic studies will be reviewed in terms of the biological information model of photobiomodulation in this paper. ILILT might work in view of its basic studies, but the further randomized placebo-controlled trial and the further safety research should be done.

  16. Intense laser-controlled quenching of molecular fragmentation

    SciTech Connect

    Lefebvre, C.; Nguyen-Dang, T. T.; Atabek, O.

    2007-02-15

    We show how efficient control can be exerted on molecular dissociation by adiabatic shaping of an intense, single laser pulse in a very simplified way, involving a few parameters (e.g., peak amplitude, carrier-wave, and modulation phases and frequencies). The strategy takes advantage of an appropriate combination of basic multiphoton mechanisms: bond softening (BS), vibrational trapping (VT), and dynamical dissociation quenching (DDQ). The resulting stabilization enhancement with respect to dissociation may increase up to a factor of 5, while simultaneously inhibiting the BS mechanism and reenforcing the VT mechanism, using DDQ. The photodissociation of H{sub 2}{sup +} submitted to a uv-visible field modulated by an IR periodic envelope, on which the consequences of a DDQ-type mechanism has recently experimentally been checked, is taken as an illustrative example.

  17. Dominant deuteron acceleration with a high-intensity laser for isotope production and neutron generation

    SciTech Connect

    Maksimchuk, A.; Raymond, A.; Yu, F.; Dollar, F.; Willingale, L.; Zulick, C.; Krushelnick, K.; Petrov, G. M.; Davis, J.

    2013-05-13

    Experiments on the interaction of an ultra-short pulse laser with heavy-water, ice-covered copper targets, at an intensity of 2 Multiplication-Sign 10{sup 19} W/cm{sup 2}, were performed demonstrating the generation of a 'pure' deuteron beam with a divergence of 20 Degree-Sign , maximum energy of 8 MeV, and a total of 3 Multiplication-Sign 10{sup 11} deuterons with energy above 1 MeV-equivalent to a conversion efficiency of 1.5%{+-} 0.2%. Subsequent experiments on irradiation of a {sup 10}B sample with deuterons and neutron generation from d-d reactions in a pitcher-catcher geometry, resulted in the production of {approx}10{sup 6} atoms of the positron emitter {sup 11}C and a neutron flux of (4{+-}1) Multiplication-Sign 10{sup 5} neutrons/sterad, respectively.

  18. Spectroscopic Analysis of High Intensity Laser Beam Jets Interaction Experiments on the Leopard Laser at UNR

    NASA Astrophysics Data System (ADS)

    Petkov, E. E.; Weller, M. E.; Kantsyrev, V. L.; Safronova, A. S.; Moschella, J. J.; Shrestha, I.; Shlyapsteva, V. V.; Stafford, A.; Keim, S. F.; University of Nevada Reno Team

    2013-10-01

    Results of Ar gas-puff experiments performed on the high power Leopard laser at UNR are presented. Flux density of laser radiation in focal spot was up to 2 × 1016 W/cm2 (pulse duration was 0.8 ns and laser wavelength was 1.057 μm). Specifically, spectroscopic analysis of K-shell Ar spectra are investigated and compared as functions of the orientation of the laser beam to linear gas jet. The laser beam axis was positioned either along the jet plane or orthogonal to it at a distance of 1 mm from the nozzle output. The diagnostics used included a time-integrated x-ray spectrometer along with a set of filtered Si diodes with various cutoff energies. In order to identify lines, a non-local thermodynamic equilibrium (non-LTE) kinetic model was utilized and was also used to determine plasma parameters such as electron temperature and density. The importance of the spectroscopic study of high intensity laser beam-jets interaction experiments is discussed. This work was supported by the Defense Threat Reduction Agency, Basic Research Award # HDTRA1-13-1-0033, to University of Nevada, Reno, and in part by the DOE/NNSA Cooperative agreements DE-NA0001984 and DE-FC52-06NA27616.

  19. Apparatus for laser-assisted electron scattering in femtosecond intense laser fields.

    PubMed

    Kanya, Reika; Morimoto, Yuya; Yamanouchi, Kaoru

    2011-12-01

    An apparatus for observation of laser-assisted electron scattering (LAES) in femtosecond intense laser fields was developed. The unique apparatus has three essential components, i.e., a photocathode-type ultrashort pulsed-electron gun, a toroidal-type electron energy analyzer enabling simultaneous detection of energy and angular distributions of scattered electrons with high efficiency, and a high repetition-rate data acquisition system combined with a high power 5 kHz Ti:sapphire laser system. These advantages make extremely weak femtosecond-LAES signals distinguishable from the huge elastic scattering signals. A precise method for securing a spatial overlap between three beams, that is, an atomic beam, an electron beam, and a laser beam, and synchronization between the electron and laser pulses is described. As a demonstration of this apparatus, an electron energy spectrum of the LAES signals with 1.4 × 10(12) W/cm(2), 795 nm, 50 fs laser pulses was observed, and the detection limit and further improvements of the apparatus are examined. PMID:22225197

  20. Wound healing after irradiation of bone tissues by Er:YAG laser

    NASA Astrophysics Data System (ADS)

    Watanabe, Hisashi; Yoshino, Toshiaki; Aoki, Akira; Ishikawa, Isao

    1997-05-01

    Clinical applications of Er:YAG laser are now developing in periodontics and restorative dentistry. To date, there have been few studies indicating safety criteria for intraoral usage of the Er:YAG laser. The present study examined the effects of the Er:YAG laser on bone tissues, supposing mis- irradiation in the oral cavity during dental application, especially periodontal surgery. The experiments were performed using the newly-developed Er:YAG laser apparatus equipped with a contact probe. In experiment 1, 10 pulses of laser irradiation were administered to the parietal bone of a rat at 50, 150 and 300 mJ/pulse with and without water irrigation, changing the irradiation distance to 0, 5, 10 and 20 mm, respectively. As a control, electric knife was employed. Macroscopic and SEM observations of the wound surface were performed. In experiment 2, laser irradiation in a straight line was performed at 150 mJ/pulse, 1- pps and 0,5, 10 mm irradiation distance without water irrigation. Wound healing was observed histologically at 0, 3, 7, 14 and 28 days after laser irradiation and compared with that of the control. Non-contact irradiation by Er:YAG laser did not cause severe damage to the parietal bone tissue under water irrigation. Contact irradiation induced a limited wound, however, new bone formation was observed 28 days after laser irradiation, while osseous defect with thermal degenerative tissue remained at the control site. In conclusion, irradiation with an Er:YAG laser would not cause severe damage to surrounding bone tissues in the oral cavity when used within the usual power settings for dental treatment. Furthermore, this laser may be applicable for osseous surgery because of its high ablation efficiency and good wound healing after irradiation.

  1. Mapping of laser diode radiation intensity by atomic-force microscopy

    NASA Astrophysics Data System (ADS)

    Alekseev, P. A.; Dunaevskii, M. S.; Slipchenko, S. O.; Podoskin, A. A.; Tarasov, I. S.

    2015-09-01

    The distribution of the intensity of laser diode radiation has been studied using an original method based on atomic-force microscopy (AFM). It is shown that the laser radiation intensity in both the near field and transition zone of a high-power semiconductor laser under room-temperature conditions can be mapped by AFM at a subwavelength resolution. The obtained patterns of radiation intensity distribution agree with the data of modeling and the results of near-field optical microscopy measurements.

  2. A laser speckle contrast analysis (LSCA) study of the effect of curing irradiance on composite polymerization kinetics

    NASA Astrophysics Data System (ADS)

    Wells-Gray, Elaine M.; Kirkpatrick, Sean J.; Duncan, Don D.

    2011-03-01

    The kinetics of resin composite polymerization plays an important, though not well understood, role it the development of shrinkage stress and the resultant integrity of the final restoration. In this report we investigate the effect of curing irradiance on the polymerization kinetics using a dynamic light scattering technique known as laser speckle contrast analysis (LSCA). Thin layer samples are considered with focus given to the effect of sample thickness on the rate results obtained with this method. We present results for the intensity fluctuation rate as a function of irradiance for two statistical models of intensity decorrelation: Lorentzian and Gaussian. Results indicate that the rate of scatterer motion varies approximately with the square root of irradiance, which agrees well with theory and previous results in the literature. Our results suggest that dynamic light scattering techniques, and LSCA in particular, provide an effective, non-contact means of assessing polymerization kinetics.

  3. Possibilities for Nuclear Photo-Science with Intense Lasers

    SciTech Connect

    Barty, C J; Hartemann, F V; McNabb, D P; Messerly, M; Siders, C; Anderson, S; Barnes, P; Betts, S; Gibson, D; Hagmann, C; Hernandez, J; Johnson, M; Jovanovic, I; Norman, R; Pruet, J; Rosenswieg, J; Shverdin, M; Tremaine, A

    2006-06-26

    The interaction of intense laser light with relativistic electrons can produce unique sources of high-energy x rays and gamma rays via Thomson scattering. ''Thomson-Radiated Extreme X-ray'' (T-REX) sources with peak photon brightness (photons per unit time per unit bandwidth per unit solid angle per unit area) that exceed that available from world's largest synchrotrons by more than 15 orders of magnitude are possible from optimally designed systems. Such sources offer the potential for development of ''nuclear photo-science'' applications in which the primary photon-atom interaction is with the nucleons and not the valence electrons. Applications include isotope-specific detection and imaging of materials, inverse density radiography, transmutation of nuclear waste and fundamental studies of nuclear structure. Because Thomson scattering cross sections are small, < 1 barn, the output from a T-REX source is optimized when the laser spot size and the electron spot size are minimized and when the electron and laser pulse durations are similar and short compared to the transit time through the focal region. The principle limitation to increased x-ray or gamma-ray brightness is ability to focus the electron beam. The effects of space charge on electron beam focus decrease approximately linearly with electron beam energy. For this reason, T-REX brightness increases rapidly as a function of the electron beam energy. As illustrated in Figure 1, above 100 keV these sources are unique in their ability to produce bright, narrow-beam, tunable, narrow-band gamma rays. New, intense, short-pulse, laser technologies for advanced T-REX sources are currently being developed at LLNL. The construction of a {approx}1 MeV-class machine with this technology is underway and will be used to excite nuclear resonance fluorescence in variety of materials. Nuclear resonance fluorescent spectra are unique signatures of each isotope and provide an ideal mechanism for identification of nuclear

  4. Ion Acceleration from the Interaction of Ultra-Intense Lasers with Solid Foils

    SciTech Connect

    Allen, M

    2004-11-24

    The discovery that ultra-intense laser pulses (I > 10{sup 18} W/cm{sup 2}) can produce short pulse, high energy proton beams has renewed interest in the fundamental mechanisms that govern particle acceleration from laser-solid interactions. Experiments have shown that protons present as hydrocarbon contaminants on laser targets can be accelerated up to energies > 50 MeV. Different theoretical models that explain the observed results have been proposed. One model describes a front-surface acceleration mechanism based on the ponderomotive potential of the laser pulse. At high intensities (I > 10{sup 18} W/cm{sup 2}), the quiver energy of an electron oscillating in the electric field of the laser pulse exceeds the electron rest mass, requiring the consideration of relativistic effects. The relativistically correct ponderomotive potential is given by U{sub p} = ([1 + I{lambda}{sup 2}/1.3 x 10{sup 18}]{sup 1/2} - 1) m{sub o}c{sup 2}, where I{lambda}{sup 2} is the irradiance in W {micro}m{sup 2}/cm{sup 2} and m{sub o}c{sup 2} is the electron rest mass. At laser irradiance of I{lambda}{sup 2} {approx} 10{sup 20} W {micro}m{sup 2}/cm{sup 2}, the ponderomotive potential can be of order several MeV. A few recent experiments--discussed in Chapter 3 of this thesis--consider this ponderomotive potential sufficiently strong to accelerate protons from the front surface of the target to energies up to tens of MeV. Another model, known as Target Normal Sheath Acceleration (TNSA), describes the mechanism as an electrostatic sheath on the back surface of the laser target. According to the TNSA model, relativistic hot electrons created at the laser-solid interaction penetrate the foil where a few escape to infinity. The remaining hot electrons are retained by the target potential and establish an electrostatic sheath on the back surface of the target. In this thesis we present several experiments that study the accelerated ions by affecting the contamination layer from which they

  5. Ionization of the hydrogen atom by intense ultrashort laser pulses

    NASA Astrophysics Data System (ADS)

    Borbély, S.; Tőkési, K.; Nagy, L.

    2008-03-01

    The ionization of atomic hydrogen in intense laser fields is studied theoretically by both quantum-mechanical and classical approaches. In the quantum-mechanical treatment we apply a momentum-space strong-field approximation (MSSFA) and the Coulomb potential is taken into account as a perturbation. The classical calculations are performed within the framework of the classical trajectory Monte Carlo method. The energy and angular distributions of the ionization probabilities of the photoelectrons are presented for different laser pulses. While for the case of low electron energies larger discrepancies can be observed between the theories in the double-differential ionization probabilities, at high electron energies the agreement is excellent. This indicates that the generation of low-energy electrons is of quantum type and it is strongly influenced by the Coulomb potential, while the production of high-energy electrons is of classical type and it is less influenced by the Coulomb interaction. Our MSSFA results are in good agreement with the most reliable calculations based on a numerical solution of the time-dependent Schrödinger equation for high momentum transfers.

  6. Low Intensity Laser Therapy Applied in the Healing of Wounds

    NASA Astrophysics Data System (ADS)

    Kahn, Fred; Matthews, Jeffrey

    2009-06-01

    Objective: The aim of this study was to determine the outcomes of Low Intensity Laser Therapy (LILT) on wound healing for patients presenting with pain, compromised neurological and physical function and tissue damage associated with vascular/diabetic ulcerations of the lower extremity. Methods: A retrospective case review of six patients treated with LILT (GaAlAs SLD, 660 nm, 750 mW, 3.6 J/cm2; GaAlAs SLD, 840 nm, 1,500 mW, 6.48 J/cm2; GaAlAs laser, 830 nm, 75 mW, 270 J/cm2) was conducted of clinical features including pain, measured by visual analogue scale (VAS), motor function, measured by range of motion (ROM) and visual outcome, measured by wound dimensions for six patients (n = 6; 5 males, 1 female; age = 67.83 years). Results: Significant progress with regard to alleviation of pain (ΔVAS = -5), improvements in motor function (ΔROM = +40%), epithelialization (wound closure rate = 3%/week) and complete wound closure was achieved. No recurrence of pathology at least one month post cessation of therapy was evident (x¯% reduction in wound area = 100%). Conclusions: LILT achieved consistent, effective and clear endpoints, was cost effective, created no adverse effects and ultimately led to the salvage of extremities.

  7. Theory and computation of atoms in intense laser fields

    NASA Astrophysics Data System (ADS)

    Smyth, Edward Stuart

    This thesis has involved performing various modifications to the HELIUM program and using the HELIUM program to study the dynamics of laser-atom interactions. The HELIUM program is a portable code for the numerical solution of the full 5-dimensional time-dependent Schrödinger Equation for 2 electron atoms in a very intense, linearly polarized, laser pulse. A finite-difference grid is used to model the two radial co-ordinates and a basis set of coupled spherical harmonics handles the three angular variables of the system. The HELIUM program was modified to incorporate a new propagator based on Krylov-subspace techniques, thus allowing a substantial increase in performance. A modular structure was implemented within the HELIUM program, separating the source code into 5 layers. This allows the program to be optimized for particular computer architectures while remaining portable across a wide variety of massively-parallel and vector supercomputers. It also greatly aids the task of program testing and verification. The breadth of output from the code was greatly extended. Numerous runs were performed for a wide variety of laser pulse parameters, enabling various observables such as ionization rates and harmonic generation to be studied. Comparisons with the results of other models have been performed and a new single active electron model has been developed. The full five-dimensional wavefunction can now be output to disk using an efficient parallel I/O strategy for subsequent analysis using the latest graphical visualization techniques. The study of magnesium, a quasi two electron system, was started using a time-independent screening potential to model the effect of the inner closed electron shells.

  8. Effect of low intensity laser therapy in an experimental model of cranio-encephalic trauma in rats

    NASA Astrophysics Data System (ADS)

    Meneguzzo, Daiane T.; Okada, Cristina Y.; Koike, Márcia K.; Silva, Bomfim A., Jr.; Moreira, Maria S.; Eduardo, Carlos d. P.; Martins Marques, Marcia

    2007-02-01

    The aim of this study was to analyze the effects of phototherapy with low intensity laser on the inflammatory reaction after rat brain injury. Cryogenic injury was performed at the brain of 16 male Wistar rats (250-300g) using a cooper probe at -80º C. Immediately, 24 h and 48 h later, the rats received laser irradiation using a GaAlAs laser (830 nm, 100 mW). The samples were randomly divided into four groups (n= 4 per group): A: control (non- irradiated); B: energy density of 14.28 J/cm2; C: 28.57 J/cm2; D: 42.85 J/cm2. Three days later, the cerebral vascular permeability and the inflammatory cells at the trauma site were evaluated. For vascular permeability analysis, 2 h prior sacrifice an intra vascular injection of Evans blue stain was done in the rats. For inflammatory cells counting, frozen samples were sectioned and the histological slides were stained with Giemsa. The data were compared by either ANOVA or Kruskall-Wallis complemented by the Dunn's test. The irradiated groups presented higher cerebral vascular permeability than controls (A: 2.6 +/- 0.8; B:12.0 +/- 2.0; C: 13.1 +/- 4.1, and D: 12.4 +/- 1.8; p=0.016). The inflammatory cell numbers of irradiated samples were similar to controls (A: 65 +/- 6; B:85 +/- 9; C: 84 +/-14, and D: 83 +/- 3; p=0.443). The data showed that phototherapy with low intensity laser modulates the inflammatory reaction in the brain by increasing the cerebral vascular permeability after a cryogenic trauma.

  9. Volumetric Heating of Ultra-High Energy Density Relativistic Plasmas by Ultrafast Laser Irradiation of Aligned Nanowire Arrays

    NASA Astrophysics Data System (ADS)

    Bargsten, Clayton; Hollinger, Reed; Shlyaptsev, Vyacheslav; Pukhov, Alexander; Keiss, David; Townsend, Amanda; Wang, Yong; Wang, Shoujun; Prieto, Amy; Rocca, Jorge

    2014-10-01

    We have demonstrated the volumetric heating of near-solid density plasmas to keV temperatures by ultra-high contrast femtosecond laser irradiation of arrays of vertically aligned nanowires with an average density up to 30% solid density. X-ray spectra show that irradiation of Ni and Au nanowire arrays with laser pulses of relativistic intensities ionizes plasma volumes several micrometers in depth to the He-like and Co-like (Au 52 +) stages respectively. The penetration depth of the heat into the nanowire array was measured monitoring He-like Co lines from irradiated arrays in which the nanowires are composed of a Co segment buried under a selected length of Ni. The measurement shows the ionization reaches He-like Co for depth of up to 5 μm within the target. This volumetric plasma heating approach creates a new laboratory plasma regime in which extreme plasma parameters can be accessed with table-top lasers. Scaling to higher laser intensities promises to create plasmas with temperatures and pressures approaching those in the center of the sun. Work supported by the U.S Department of Energy, Fusion Energy Sciences and the Defense Threat Reduction Agency grant HDTRA-1-10-1-0079. A.P was supported by of DFG-funded project TR18.

  10. Effects of surface ligands and solvents on quantum dot photostability under pulsed UV laser irradiation

    NASA Astrophysics Data System (ADS)

    Krivenkov, Victor A.; Samokhvalov, Pavel S.; Linkov, Pavel A.; Prokhorov, Sergey D.; Martynov, Igor L.; Chistyakov, Alexander A.; Nabiev, Igor

    2015-05-01

    The organic ligands passivating the surface of semiconductor quantum dots (QDs) and the solvents used strongly determine the photostability of QD solutions. Highly purified QD solutions in chloroform have been shown to photodegrade upon pulsed ultraviolet (UV) irradiation, irrespectively of the type of surface ligand. However, the photostability of QDs dissolved in n-octane, a more photochemically inert solvent, strongly depends on the ligands passivating their surface. In n-octane, hexadecylamine-coated QDs are completely stable and display no photochemical response to pulsed UV laser irradiation. In solutions of octanethiol-capped QDs, the photoluminescence intensity slightly decreases under irradiation. QDs coated with trioctylphosphine oxide exhibit a more complex pattern of photobleaching, which depends on the initial value of fluorescence quantum yield of QDs. This complex pattern may be accounted for by two competing processes: (1) ligand photodesorption accompanied by photobleaching due to specific alignment of the band levels of QDs and highest occupied molecular orbital of the ligand and (2) photoinduced decrease in the population of trapping states. Furthermore, practically no thermodynamic degradation of QD solutions has been observed for the micromolar QD concentration used in the study, in contrast to lower concentrations, thus confirming the photoinduced origin of the changes caused by UV irradiation. Obtained results show that the photostability of QDs may be strongly increased by careful selection of the ligands passivating their surface and the solvents used in the experiments.

  11. [Use of the thermal laser effect of laser irradiation for cardiovascular applications exemplified by the Nd:YAG laser].

    PubMed

    Ischinger, T; Coppenrath, K; Weber, H; Enders, S; Unsöld, E; Hessel, S

    1989-11-01

    Techniques of percutaneous transluminal application of laser energy for vessel recanalization have been used clinically since 1983. The commonly used Nd:YAG and argon lasers achieve ablation of atherosclerotic plaques by thermal action (vaporization). In order to reduce undesirable thermal damage in the neighborhood of the target tissue and to avoid vessel perforation, optimal irradiation parameters, modified (atraumatic) fiber tips (hot tips, sapphires), and steerable catheter systems needed to be implemented. Favorable results from peripheral application have encouraged use in the coronary circulation. More recently, coagulative tissue effects of circumferential irradiation of the vessel wall during balloon dilatation have been used for stabilization of acute and late results after mechanical balloon angioplasty. Enhancement of the differential light absorption of atherosclerotic plaque by use of biological dyes may further improve selective intravascular laser application. Intraoperative ECG-guided laser coagulation of arrhythmogenic areas of myocardium is a method for treatment of malignant arrhythmias. Transluminal non-operative application of myocardial laser photocoagulation has now been tested experimentally and shown to be safe and effective. There was no arrhythmogenicity or thermal damage of coronary arteries associated with this method. Innovative techniques such as nanosecond pulsed excimer lasers (athermal action) and development of "intelligent" lasers--which are equipped with spectroscopy-guided feedback systems for plaque recognition--have opened new perspectives and will further improve safety and efficacy of clinical laser application. However, according to current experience, the thermally acting Nd:YAG laser is an effective and versatile mode of laser therapy for selected cardiovascular indications. PMID:2532812

  12. 3D nanotube-based composites produced by laser irradiation

    SciTech Connect

    Ageeva, S A; Bobrinetskii, I I; Nevolin, Vladimir K; Podgaetskii, Vitalii M; Selishchev, S V; Simunin, M M; Konov, Vitalii I; Savranskii, V V; Ponomareva, O V

    2009-04-30

    3D nanocomposites have been fabricated through self-assembly under near-IR cw laser irradiation, using four types of multiwalled and single-walled carbon nanotubes produced by chemical vapour deposition, disproportionation on Fe clusters and cathode sputtering in an inert gas. The composites were prepared by laser irradiation of aqueous solutions of bovine serum albumin until the solvent was evaporated off and a homogeneous black material was obtained: modified albumin reinforced with nanotubes. The consistency of the composites ranged from paste-like to glass-like. Atomic force microscopy was used to study the surface morphology of the nanomaterials. The nanocomposites had a 3D quasi-periodic structure formed by almost spherical or toroidal particles 200-500 nm in diameter and 30-40 nm in visible height. Their inner, quasi-periodic structure was occasionally seen through surface microfractures. The density and hardness of the nanocomposites exceed those of microcrystalline albumin powder by 20% and by a factor of 3-5, respectively. (nanostructures)

  13. Appearance of Density Cavitations in the Laser Wake in Simulations of High Intensity Laser-Plasma Interactions

    SciTech Connect

    Wang, T.-L.

    2009-01-22

    Nonlinear interactions of high intensity, ultrashort laser pulses with underdense plasmas produce many interesting features that may appear in computer simulations. One of these features commonly observed in Particle-In-Cell (PIC) simulations is the spontaneous appearance of long-lived density cavitations in the plasma wake region behind the laser pulse. To study these cavitations, several small 2D PIC simulations are run in which plasma density, density ramps, total simulation time, laser pulsewidth, laser intensity, and laser polarization parameters have been varied. Based on the simulation results, some possible aspects of an experiment designed to directly detect these structures are discussed.

  14. Ho:YAG laser irradiation in blood vessel as a vasodilator: ex vivo study

    NASA Astrophysics Data System (ADS)

    Nakatani, E.; Iwasaki, T.; Kaneko, K.; Shimazaki, N.; Arai, T.

    2007-02-01

    We studied Ho:YAG laser irradiation in blood vessel as a vasodilator ex vivo. We thought that the Ho:YAG laser-induced bubble expansion might be able to dilate the vessel because we found the vessel wall expansion after the Ho:YAG laser irradiation, that is steady deformation, in the vessel ex vivo. There have been many reports regarding to the Ho:YAG laser irradiation in the vessel. Most of studies concentrated on the interaction between Ho:YAG laser irradiation and vessel wall to investigate side effect on Ho:YAG laser angioplasty. We proposed to use the Ho:YAG laser-induced bubble expansion as a vasodilator. We studied vasodilation effect of the Ho:YAG laser-induced bubble ex vivo. The flash lamp excited Ho:YAG laser surgical unit (IH102, NIIC, Japan) (λ=2.1μm) was used. The laser energy was delivered by a silica glass fiber (outer diameter: 1000μm, core diameter: 600μm). The laser-induced bubble was generated in the extracted fresh porcine carotid artery with the warmed saline perfusion. The laser energy at the fiber tip was ranging from 170-1300mJ per pulse. Number of the laser irradiation was ranged from 20pulses to 100pulses. The outer diameter of the vessel was observed. To examine the change in mechanical properties of the vessel wall, the stress-strain curve of the laser-irradiated vessel was measured. Birefringence observation and microscopic observation of staining specimen were performed. When the laser energy was set to 1300mJ per pulse, the outer diameter of the vessel after the laser irradiation was expanded by 1.4 times comparing with that of before the laser irradiation and the dilatation effect was kept even at 10minutes after the irradiation. The elasticity modulus of the artery by collagen was changed by the laser irradiation. In the polarized microscopic observation, the brightness of the intimal side of the vessel is increased comparing with that of the normal. We think this brightness increasing may be attributed to birefringence change

  15. Geometry- and diffraction-independent ionization probabilities in intense laser fields: Probing atomic ionization mechanisms with effective intensity matching

    SciTech Connect

    Bryan, W. A.; Stebbings, S. L.; English, E. M. L.; Goodworth, T. R. J.; Newell, W. R.; McKenna, J.; Suresh, M.; Srigengan, B.; Williams, I. D.; Turcu, I. C. E.; Smith, J. M.; Divall, E. J.; Hooker, C. J.; Langley, A. J.

    2006-01-15

    We report an experimental technique for the comparison of ionization processes in ultrafast laser pulses irrespective of pulse ellipticity. Multiple ionization of xenon by 50 fs 790 nm, linearly and circularly polarized laser pulses is observed over the intensity range 10 TW/cm{sup 2} to 10 PW/cm{sup 2} using effective intensity matching (EIM), which is coupled with intensity selective scanning (ISS) to recover the geometry-independent probability of ionization. Such measurements, made possible by quantifying diffraction effects in the laser focus, are compared directly to theoretical predictions of multiphoton, tunnel and field ionization, and a remarkable agreement demonstrated. EIM-ISS allows the straightforward quantification of the probability of recollision ionization in a linearly polarized laser pulse. Furthermore, the probability of ionization is discussed in terms of the Keldysh adiabaticity parameter {gamma}, and the influence of the precursor ionic states present in recollision ionization is observed.

  16. γ-H2AX and phosphorylated ATM focus formation in cancer cells after laser plasma X irradiation.

    PubMed

    Sato, Katsutoshi; Nishikino, Masaharu; Okano, Yasuaki; Ohshima, Shinsuke; Hasegawa, Noboru; Ishino, Masahiko; Kawachi, Tetsuya; Numasaki, Hodaka; Teshima, Teruki; Nishimura, Hiroaki

    2010-10-01

    The usefulness of laser plasma X-ray pulses for medical and radiation biological studies was investigated, and the effects of laser plasma X rays were compared with those of conventional sources such as a linear accelerator. A cell irradiation system was developed that used copper-Kα (8 keV) lines from an ultrashort high-intensity laser to produce plasma. The absorbed dose of the 8 keV laser plasma X-ray pulse was estimated accurately with Gafchromic® EBT film. When the cells were irradiated with approximately 2 Gy of laser plasma X rays, the circular regions on γ-H2AX-positive cells could be clearly identified. Moreover, the numbers of γ-H2AX and phosphorylated ataxia telangiectasia mutated (ATM) foci induced by 8 keV laser plasma X rays were comparable to those induced by 4 MV X rays. These results indicate that the laser plasma X ray source may be useful for radiation biology studies. PMID:20718602

  17. Hyperspectral and gated ICCD imagery for laser irradiated carbon materials

    NASA Astrophysics Data System (ADS)

    Roberts, Charles D.; Acosta, Roberto A.; Marciniak, Michael A.; Perram, Glen P.

    2013-02-01

    New optical diagnostics for studying laser ablation and induced combustion for carbon materials are key to monitoring the evolving, spatial distribution of the gas plume. We are developing high speed imaging FTIR and gated ICCD imagery for materials processing, manufacture process control, and high energy laser applications. The results from two projects will be discussed. First, an imaging Fourier Transform Spectrometer with a 320 x 256 InSb focal plane array frames at 1.9 kHz with a spatial resolution of 1 mm and spectral resolution of up to 0.25 cm-1. Gas phase plumes above the surface of laser-irradiated black plexiglass, fiberglass and painted thin metals have been spectrally resolved. Molecular emission from CO, CO2, H2O, and hydrocarbons is readily identified. A line-by-line radiative transfer model is used to derive movies for specie concentrations and temperatures. Second, excimer laser pulsed ablation of bulk graphite into low-pressure (0.05 - 1 Torr) argon generates highly ionized, high speed (M>40) plumes. A gated, intensified CCD camera with band pass filtering has been used to generate plume imagery with temporal resolution of 10ns. The Sedov-Taylor shock model characterizes the propagation of the shock front if the dimensionality of the plume is allowed to deviate from ideal spherical expansion. A drag model is more appropriate when the plume approaches extinction (~10 μs) and extends the characterization into the far field. Conversion of laser pulse energy to the shock is efficient.

  18. X-ray generation in cryogenic targets irradiated by 1 {mu}m pulse laser

    SciTech Connect

    Shimoura, A.; Amano, S.; Miyamoto, S.; Mochizuki, T.

    1998-01-01

    Soft x-ray spectral radiations from Xe, H{sub 2}O, and CO{sub 2} cryogenic targets irradiated by a 1 {mu}m neodymium doped YAG-slab laser at pulse widths of 12{endash}20 ns and at laser intensities of 5{times}10{sup 10}{endash}10{sup 12}W/cm{sup 2} have been observed. These targets radiate soft x-rays in a wavelength range of 10{endash}13 nm which is useful for projection microlithography. We have found a strong x-ray spectral peak at {lambda}=10.8nm with a Xe cryogenic target. The measured x-ray conversion efficiency with the Xe target was 0.8{percent}/sr({lambda}=10.8{plus_minus}0.27nm) at a laser intensity of 1{times}10{sup 12}W/cm{sup 2}. This was ten times or more efficient than that with H{sub 2}O and CO{sub 2} targets. {copyright} {ital 1998 American Institute of Physics.}

  19. On the formation of nanostructures on a CdTe surface, stimulated by surface acoustic waves under nanosecond laser irradiation

    SciTech Connect

    Vlasenko, A. I.; Baidullaeva, A.; Veleschuk, V. P. Mozol, P. E.; Boiko, N. I.; Litvin, O. S.

    2015-02-15

    The formation of nanoscale structures in the unirradiated part of a p-CdTe crystal surface irradiated by a nanosecond ruby laser is revealed and investigated. It is shown that their formation is caused by the effect of the long-range action of a laser pulse with an intensity of I = 20 MW/cm{sup 2}. Nanoscale-structure formation is explained by the influence of the pressure gradient of the surface acoustic wave, in particular, within the “vacancy-pump” mechanism on the surface.

  20. Laser shaping of a relativistic intense, short Gaussian pulse by a plasma lens.

    PubMed

    Wang, H Y; Lin, C; Sheng, Z M; Liu, B; Zhao, S; Guo, Z Y; Lu, Y R; He, X T; Chen, J E; Yan, X Q

    2011-12-23

    By 3D particle-in-cell simulation and analysis, we propose a plasma lens to make high intensity, high contrast laser pulses with a steep front. When an intense, short Gaussian laser pulse of circular polarization propagates in near-critical plasma, it drives strong currents of relativistic electrons which magnetize the plasma. Three pulse shaping effects are synchronously observed when the laser passes through the plasma lens. The laser intensity is increased by more than 1 order of magnitude while the initial Gaussian profile undergoes self-modulation longitudinally and develops a steep front. Meanwhile, a nonrelativistic prepulse can be absorbed by the overcritical plasma lens, which can improve the laser contrast without affecting laser shaping of the main pulse. If the plasma skin length is properly chosen and kept fixed, the plasma lens can be used for varied laser intensity above 10(19) W/cm(2). PMID:22243161