Science.gov

Sample records for ablative pulsed plasma

  1. Plasma acceleration processes in an ablative pulsed plasma thruster

    SciTech Connect

    Koizumi, Hiroyuki; Noji, Ryosuke; Komurasaki, Kimiya; Arakawa, Yoshihiro

    2007-03-15

    Plasma acceleration processes in an ablative pulsed plasma thruster (APPT) were investigated. APPTs are space propulsion options suitable for microspacecraft, and have recently attracted much attention because of their low electric power requirements and simple, compact propellant system. The plasma acceleration mechanism, however, has not been well understood. In the present work, emission spectroscopy, high speed photography, and magnetic field measurements are conducted inside the electrode channel of an APPT with rectangular geometry. The successive images of neutral particles and ions give us a comprehensive understanding of their behavior under electromagnetic acceleration. The magnetic field profile clarifies the location where the electromagnetic force takes effect. As a result, it is shown that high density, ablated neutral gas stays near the propellant surface, and only a fraction of the neutrals is converted into plasma and electromagnetically accelerated, leaving the residual neutrals behind.

  2. Plasma mediated ablation of biological tissues with ultrashort laser pulses

    SciTech Connect

    Oraevsky, A.A. |; DaSilva, L.B.; Feit, M.D.

    1995-03-08

    Plasma mediated ablation of collagen gels and porcine cornea was studied at various laser pulse durations in the range from 350 fs to 1 ns at 1,053 nm wavelength. A time resolved stress detection technique was employed to measure transient stress profiles and amplitudes. Optical microscopy was used to characterize ablation craters qualitatively, while a wide band acoustic transducer helped to quantify tissue mechanical response and the ablation threshold. The ablation threshold was measured as a function of laser pulse duration and linear absorption coefficient. For nanosecond pulses the ablation threshold was found to have a strong dependence on the linear absorption coefficient of the material. As the pulse length decreased into the subpicosecond regime the ablation threshold became insensitive to the linear absorption coefficient. The ablation efficiency was found to be insensitive to both the laser pulse duration and the linear absorption coefficient. High quality ablation craters with no thermal or mechanical damage to surrounding material were obtained with 350 fs laser pulses. The mechanism of optical breakdown at the tissue surface was theoretically investigated. In the nanosecond regime, optical breakdown proceeds as an electron collisional avalanche ionization initiated by thermal seed electrons. These seed electrons are created by heating of the tissue by linear absorption. In the ultrashort pulse range, optical breakdown is initiated by the multiphoton ionization of the irradiated medium (6 photons in case of tissue irradiated at 1,053 nm wavelength), and becomes less sensitive to the linear absorption coefficient. The energy deposition profile is insensitive to both the laser pulse duration and the linear absorption coefficient.

  3. Study of breakdown in an ablative pulsed plasma thruster

    NASA Astrophysics Data System (ADS)

    Huang, Tiankun; Wu, Zhiwen; Liu, Xiangyang; Xie, Kan; Wang, Ningfei; Cheng, Yue

    2015-10-01

    Breakdown in ablative pulsed plasma thrusters (APPTs) must be studied in order to design new types of APPTs and measure particular parameters. In this paper, we studied a parallel-plate ablative pulsed plasma thruster that used a coaxial semiconductor spark plug. By operating the APPT about 500 times with various capacitor voltages and electrode gaps, we measured and analyzed the voltage of the spark plug, the voltage between the electrodes, and the discharge current. These experiments revealed a time delay (˜1-10 μs) between spark plug ignition and capacitor discharge, which may affect the performance of high-pulsing-rate (>10 kHz) and double-discharge APPTs, and the measurements of some of the APPT parameters. The delay time decreased as the capacitor voltage increased, and it increased with an increasing electrode gap and increasing number of ignitions. We explain our results through a simple theoretical analysis.

  4. Study of breakdown in an ablative pulsed plasma thruster

    SciTech Connect

    Huang, Tiankun; Wu, Zhiwen; Liu, Xiangyang; Xie, Kan; Wang, Ningfei; Cheng, Yue

    2015-10-15

    Breakdown in ablative pulsed plasma thrusters (APPTs) must be studied in order to design new types of APPTs and measure particular parameters. In this paper, we studied a parallel-plate ablative pulsed plasma thruster that used a coaxial semiconductor spark plug. By operating the APPT about 500 times with various capacitor voltages and electrode gaps, we measured and analyzed the voltage of the spark plug, the voltage between the electrodes, and the discharge current. These experiments revealed a time delay (∼1–10 μs) between spark plug ignition and capacitor discharge, which may affect the performance of high-pulsing-rate (>10 kHz) and double-discharge APPTs, and the measurements of some of the APPT parameters. The delay time decreased as the capacitor voltage increased, and it increased with an increasing electrode gap and increasing number of ignitions. We explain our results through a simple theoretical analysis.

  5. Characteristics of plasma properties in an ablative pulsed plasma thruster

    SciTech Connect

    Schoenherr, Tony; Nees, Frank; Arakawa, Yoshihiro; Komurasaki, Kimiya; Herdrich, Georg

    2013-03-15

    Pulsed plasma thrusters are electric space propulsion devices which create a highly transient plasma bulk in a short-time arc discharge that is expelled to create thrust. The transitional character and the dependency on the discharge properties are yet to be elucidated. In this study, optical emission spectroscopy and Mach-Zehnder interferometry are applied to investigate the plasma properties in variation of time, space, and discharge energy. Electron temperature, electron density, and Knudsen numbers are derived for the plasma bulk and discussed. Temperatures were found to be in the order of 1.7 to 3.1 eV, whereas electron densities showed maximum values of more than 10{sup 17} cm{sup -3}. Both values showed strong dependency on the discharge voltage and were typically higher closer to the electrodes. Capacitance and time showed less influence. Knudsen numbers were derived to be in the order of 10{sup -3}-10{sup -2}, thus, indicating a continuum flow behavior in the main plasma bulk.

  6. Tracing the plasma interactions for pulsed reactive crossed-beam laser ablation

    SciTech Connect

    Chen, Jikun; Stender, Dieter; Pichler, Markus; Pergolesi, Daniele; Schneider, Christof W.; Wokaun, Alexander; Lippert, Thomas; Döbeli, Max

    2015-10-28

    Pulsed reactive crossed-beam laser ablation is an effective technique to govern the chemical activity of plasma species and background molecules during pulsed laser deposition. Instead of using a constant background pressure, a gas pulse with a reactive gas, synchronized with the laser beam, is injected into vacuum or a low background pressure near the ablated area of the target. It intercepts the initially generated plasma plume, thereby enhancing the physicochemical interactions between the gaseous environment and the plasma species. For this study, kinetic energy resolved mass-spectrometry and time-resolved plasma imaging were used to study the physicochemical processes occurring during the reactive crossed beam laser ablation of a partially {sup 18}O substituted La{sub 0.6}Sr{sub 0.4}MnO{sub 3} target using oxygen as gas pulse. The characteristics of the ablated plasma are compared with those observed during pulsed laser deposition in different oxygen background pressures.

  7. Tracing the plasma interactions for pulsed reactive crossed-beam laser ablation

    NASA Astrophysics Data System (ADS)

    Chen, Jikun; Stender, Dieter; Pichler, Markus; Döbeli, Max; Pergolesi, Daniele; Schneider, Christof W.; Wokaun, Alexander; Lippert, Thomas

    2015-10-01

    Pulsed reactive crossed-beam laser ablation is an effective technique to govern the chemical activity of plasma species and background molecules during pulsed laser deposition. Instead of using a constant background pressure, a gas pulse with a reactive gas, synchronized with the laser beam, is injected into vacuum or a low background pressure near the ablated area of the target. It intercepts the initially generated plasma plume, thereby enhancing the physicochemical interactions between the gaseous environment and the plasma species. For this study, kinetic energy resolved mass-spectrometry and time-resolved plasma imaging were used to study the physicochemical processes occurring during the reactive crossed beam laser ablation of a partially 18O substituted La0.6Sr0.4MnO3 target using oxygen as gas pulse. The characteristics of the ablated plasma are compared with those observed during pulsed laser deposition in different oxygen background pressures.

  8. Plasma luminescence feedback control system for precise ultrashort pulse laser tissue ablation

    NASA Astrophysics Data System (ADS)

    Kim, Beop-Min; Feit, Michael D.; Rubenchik, Alexander M.; Gold, David M.; Darrow, Christopher B.; Marion, John E., II; Da Silva, Luiz B.

    1998-05-01

    Plasma luminescence spectroscopy was used for precise ablation of bone tissue without damaging nearby soft tissue using an ultrashort pulse laser. Strong contrast of the luminescence spectra between bone marrow and spinal cord provided the real time feedback control so bone tissue is selectively ablated while preserving the spinal cord.

  9. Plasma luminescence feedback control system for precise ultrashort pulse laser tissue ablation

    SciTech Connect

    Kim, B.M.; Feit, M.D.; Rubenchick, A.M.; Gold, D.M.; Darrown, C.B.; Da Silva, L.B.

    1998-01-01

    Plasma luminescence spectroscopy was used for precise ablation of bone tissue without damaging nearby soft tissue using ultrashort pulse laser (USPL). Strong contrast of the luminescence spectra between bone marrow and spinal cord provided the real time feedback control so that only bone tissue can be selectively ablated while preserving the spinal cord.

  10. Numerical studies of wall-plasma interactions and ionization phenomena in an ablative pulsed plasma thruster

    NASA Astrophysics Data System (ADS)

    Yang, Lei; Zeng, Guangshang; Tang, Haibin; Huang, Yuping; Liu, Xiangyang

    2016-07-01

    Wall-plasma interactions excited by ablation controlled arcs are very critical physical processes in pulsed plasma thrusters (PPTs). Their effects on the ionization processes of ablated vapor into discharge plasma directly determine PPT performances. To reveal the physics governing the ionization phenomena in PPT discharge, a modified model taking into account the pyrolysis effect of heated polytetrafluoroethylene propellant on the wall-plasma interactions was developed. The feasibility of the modified model was analyzed by creating a one-dimensional simulation of a rectangular ablative PPT. The wall-plasma interaction results based on this modified model were found to be more realistic than for the unmodified model; this reflects the dynamic changes of the inflow parameters during discharge in our model. Furthermore, the temporal and spatial variations of the different plasma species in the discharge chamber were numerically studied. The numerical studies showed that polytetrafluoroethylene plasma was mainly composed of monovalent ions; carbon and fluorine ions were concentrated in the upstream and downstream discharge chamber, respectively. The results based on this modified model were in good agreement with the experimental formation times of the various plasma species. A large number of short-lived and highly ionized carbon and fluorine species (divalent and trivalent ions) were created during initial discharge. These highly ionized species reached their peak density earlier than the singly ionized species.

  11. Plasma effects during ablation and drilling using pulsed solid-state lasers

    NASA Astrophysics Data System (ADS)

    Breitling, Detlef; Ruf, Andreas; Berger, Peter W.; Dausinger, Friedrich H.; Klimentov, Sergei M.; Pivovarov, Paval A.; Kononenko, Taras V.; Konov, Vitali I.

    2003-09-01

    Plasma and vapor plumes generated by ultrashort laser pulses have been studied by various optical methods for both single pulse ablation as well as high-repetition rate drilling. Time-resolved shadow and resonance absorption photographs enable to determine the plume and vapor expansion behavior and, by means of an analytical shock wave model, allow to estimate an energy balance that can be refined by plasma transmission measurements. The results furthermore suggest that several types of laser-induced plasmas can be distinguished according to their origin: the material vapor plasma originating at the ablated surface even at moderate intensities, a breakdown plasma at increased power densities occurring in cold vapor or dust particles left from previous ablations during repetitively-pulsed processing and, finally, the optical breakdown in the pure atmosphere at high intensities. The latter also gives rise to nonlinear scattering phenomena resulting in a strong redistribution of the energy density in the beam profile.

  12. Representative sampling using single-pulse laser ablation withinductively coupled plasma mass spectroscopy

    SciTech Connect

    Liu, Haichen; Mao, Xianglei; Russo, Richard E.

    2001-04-02

    Single pulse laser ablation sampling with inductively coupled plasma mass spectrometry (ICP-MS) was assessed for accurate chemical analysis. Elemental fractionation (e.g. Pb/U), the quantity of ablated mass (crater volume), ICP-MS intensity and the particle contribution (spike signal) during single pulse ablation of NIST 610 glass were investigated. Pb/U fractionation significantly changed between the first and second laser pulse and showed strong irradiance dependence. The Pb/U ratio obtained by the first pulse was usually higher than that of the second pulse, with the average value close to the representative level. Segregation during laser ablation is proposed to explain the composition change between the first and second pulse. Crater volume measurements showed that the second pulse produced significantly more ablated mass. A roll-off of the crater depth occurred at {approx}750 GW/cm{sup 2}. The absolute ICP-MS intensity from the second pulse showed no correlation with crater depth. Particle induced spikes on the transit signal showed irradiance and elemental species dependence.

  13. Pulsed IR laser ablation of organic polymers in air: shielding effects and plasma pipe formation

    NASA Astrophysics Data System (ADS)

    Panchenko, A. N.; Shulepov, M. A.; Tel'minov, A. E.; Zakharov, L. A.; Paletsky, A. A.; Bulgakova, N. M.

    2011-09-01

    We report the effect of 'plasma pipe' formation on pulsed laser ablation of organic polymers in air under normal conditions. Ablation of polymers (PMMA, polyimide) is carried out in a wide range of CO2 laser fluences with special attention to plasma formation in the ablation products. Evolution of laser ablation plumes in air under different pressures is investigated with simultaneous registration of radiation spectra of the ablation products. An analysis based on thermo-chemical modelling is performed to elucidate the effects of laser light attenuation upon ablation, including plasma and chemical processes in a near-target space. The analysis has shown that the experimental observations of plume development in air can be explained by a combination of processes including formation of a pre-ionized channel along the laser beam propagation, laser-supported detonation wave and effective combustion of the polymer ablation products. A scenario of a streamer-like polymer plasma flow within an air plasma pipe created via laser-induced breakdown is proposed.

  14. Collective behavior of silver plasma during pulsed laser ablation

    NASA Astrophysics Data System (ADS)

    Dildar, I. M.; Rehman, S.; Khaleeq-ur-Rahman, M.; Bhatti, K. A.; Shuaib, A.

    2015-07-01

    The present work reports an electrical investigation of silver plasma using a self-fabricated Langmuir probe in air and under a low vacuum (~10-3 torr). A silver target was irradiated with a Q-switched Nd:YAG laser with the wavelength 1.064 µm, energy 10 mJ, pulse duration 9-14 ns and power 1.1 MW. The collective behavior of a silver plasma plume is studied using a Langmuir probe as an electrical diagnostic technique. By applying different positive and negative voltages to the probe, the respective signals are collected on a four channels digital storage oscilloscope having a frequency of 500 MHz. An I-V curve helps to measure electron temperature and electron density directly and plasma frequency, response time, Debye length and number of particles in ‘Debye’s sphere’ indirectly using the theory of Langmuir probe and mathematical formulas. The floating potential is measured as negative for laser induced silver plasma in air and vacuum, following the theory of plasma.

  15. Infrared nanosecond laser-metal ablation in atmosphere: Initial plasma during laser pulse and further expansion

    SciTech Connect

    Wu, Jian; Wei, Wenfu; Li, Xingwen; Jia, Shenli; Qiu, Aici

    2013-04-22

    We have investigated the dynamics of the nanosecond laser ablated plasma within and after the laser pulse irradiation using fast photography. A 1064 nm, 15 ns laser beam was focused onto a target made from various materials with an energy density in the order of J/mm{sup 2} in atmosphere. The plasma dynamics during the nanosecond laser pulse were observed, which could be divided into three stages: fast expansion, division into the primary plasma and the front plasma, and stagnation. After the laser terminated, a critical moment when the primary plasma expansion transited from the shock model to the drag model was resolved, and this phenomenon could be understood in terms of interactions between the primary and the front plasmas.

  16. Time-resolved diagnostics of excimer laser-generated ablation plasmas used for pulsed laser deposition

    SciTech Connect

    Geohegan, D.B.

    1994-09-01

    Characteristics of laser plasmas used for pulsed laser deposition (PLD) of thin films are examined with four in situ diagnostic techniques: Optical emission spectroscopy, optical absorption spectroscopy, ion probe studies, and gated ICCD (intensified charge-coupled-device array) fast photography. These four techniques are complementary and permit simultaneous views of the transport of ions, excited states, ground state neutrals and ions, and hot particulates following KrF laser ablation of YBCO, BN, graphite and Si in vacuum and background gases. The implementation and advantages of the four techniques are first described in order to introduce the key features of laser plasmas for pulsed laser deposition. Aspects of the interaction of the ablation plume with background gases (i.e., thermalization, attenuation, shock formation) and the collision of the plasma plume with the substrate heater are then summarized. The techniques of fast ICCD photography and gated photon counting are then applied to investigate the temperature, velocity, and spatial distribution of hot particles generated during KrF ablation of YBCO, BN, Si and graphite. Finally, key features of fast imaging of the laser ablation of graphite into high pressure rare gases are presented in order to elucidate internal reflected shocks within the plume, redeposition of material on a surface, and formation of hot nanoparticles within the plume.

  17. On the plume splitting of pulsed laser ablated Fe and Al plasmas

    NASA Astrophysics Data System (ADS)

    Mahmood, S.; Rawat, R. S.; Darby, M. S. B.; Zakaullah, M.; Springham, S. V.; Tan, T. L.; Lee, P.

    2010-10-01

    A time resolved imaging study of pulsed laser ablated Fe and Al plasma plumes with specific interest in the splitting of plumes into the slow and fast moving components as they expand through the background argon gas at different pressures is reported. The material ablation was achieved using a Q-switched Nd:YAG (yttrium aluminum garnet) laser operating at 532 nm with a pulse duration of ˜8 ns full width at half maximum and a fluence of 30 Jcm-2 at the target surface. Typical time resolved images with low magnification show that the splitting occurs at moderate background gas pressures (0.5 and 1.0 mbar for Fe, and 0.2 mbar for Al plasma plumes). The plume splitting did not occur for higher background gas pressures.

  18. On the plume splitting of pulsed laser ablated Fe and Al plasmas

    SciTech Connect

    Mahmood, S.; Rawat, R. S.; Springham, S. V.; Tan, T. L.; Lee, P.; Darby, M. S. B.; Zakaullah, M.

    2010-10-15

    A time resolved imaging study of pulsed laser ablated Fe and Al plasma plumes with specific interest in the splitting of plumes into the slow and fast moving components as they expand through the background argon gas at different pressures is reported. The material ablation was achieved using a Q-switched Nd:YAG (yttrium aluminum garnet) laser operating at 532 nm with a pulse duration of {approx}8 ns full width at half maximum and a fluence of 30 Jcm{sup -2} at the target surface. Typical time resolved images with low magnification show that the splitting occurs at moderate background gas pressures (0.5 and 1.0 mbar for Fe, and 0.2 mbar for Al plasma plumes). The plume splitting did not occur for higher background gas pressures.

  19. Surface modification of biomaterials by pulsed laser ablation deposition and plasma/gamma polymerization

    NASA Astrophysics Data System (ADS)

    Rau, Kaustubh R.

    Surface modification of stainless-steel was carried out by two different methods: pulsed laser ablation deposition (PLAD) and a combined plasma/gamma process. A potential application was the surface modification of endovascular stents, to enhance biocompatibility. The pulsed laser ablation deposition process, had not been previously reported for modifying stents and represented a unique and potentially important method for surface modification of biomaterials. Polydimethylsiloxane (PDMS) elatomer was studied using the PLAD technique. Cross- linked PDMS was deemed important because of its general use for biomedical implants and devices as well as in other fields. Furthermore, PDMS deposition using PLAD had not been previously studied and any information gained on its ablation characteristics could be important scientifically and technologically. The studies reported here showed that the deposited silicone film properties had a dependence on the laser energy density incident on the target. Smooth, hydrophobic, silicone-like films were deposited at low energy densities (100-150 mJ/cm2). At high energy densities (>200 mJ/cm2), the films had an higher oxygen content than PDMS, were hydrophilic and tended to show a more particulate morphology. It was also determined that (1)the deposited films were stable and extremely adherent to the substrate, (2)silicone deposition exhibited an `incubation effect' which led to the film properties changing with laser pulse number and (3)films deposited under high vacuum were similar to films deposited at low vacuum levels. The mechanical properties of the PLAD films were determined by nanomechanical measurements which are based on the Atomic Force Microscope (AFM). From these measurements, it was possible to determine the modulus of the films and also study their scratch resistance. Such measurement techniques represent a significant advance over current state-of-the-art thin film characterization methods. An empirical model for

  20. Measurement of electron density by Stark broadening in an ablative pulsed plasma thruster

    SciTech Connect

    Liu Feng; Nie Zongfu; Xu Xu; Zhou Qianhong; Li Linsen; Liang Rongqing

    2008-09-15

    Electron density was measured by Stark broadening in an ablative pulsed plasma thruster. The asymmetrical deconvolution is used to obtain Stark broadening. The result shows that the electron density in the discharge channel is 2.534x10{sup 22} m{sup -3} when the discharge energy is 5 J and the measured electron temperature is 18 000 K, and it is in excellent agreement with other experimental and theoretical data. The electron density in the discharge channel increases very minimally with increasing discharge energy.

  1. A new stage in the development of ablative pulsed plasma thrusters at the RIAME

    NASA Astrophysics Data System (ADS)

    Antropov, N. N.; Bogatyy, A. V.; Dyakonov, G. A.; Lyubinskaya, N. V.; Popov, G. A.; Semenikhin, S. A.; Tyutin, V. K.; Khrustalev, M. M.; Yakovlev, V. N.

    2012-12-01

    This paper presents an overview of the works on ablative pulsed plasma thrusters (APPTs) carried out at the Research Institute of Applied Mechanics and Electrodynamics (RIAME). The main features of next generation thrusters developed at the RIAME in the 2000s are discussed together with the optimization criteria for APPTs intended for use in correction propulsion systems of small spacecraft, e.g., MKA-FKI (developed by the Lavochkin Association) and Soyuz-Sat-O (developed by Maksimov Space Systems Research Institute and the Production Corporation Polyot).

  2. Pulsed laser ablation plasmas generated in CO2 under high-pressure conditions up to supercritical fluid

    NASA Astrophysics Data System (ADS)

    Kato, Toru; Stauss, Sven; Kato, Satoshi; Urabe, Keiichiro; Baba, Motoyoshi; Suemoto, Tohru; Terashima, Kazuo

    2012-11-01

    Pulsed laser ablation of solids in supercritical media has a large potential for nanomaterials fabrication. We investigated plasmas generated by pulsed laser ablation of Ni targets in CO2 at pressures ranging from 0.1 to 16 MPa at 304.5 K. Plasma species were characterized by optical emission spectroscopy, and the evolution of cavitation bubbles and shockwaves were observed by time-resolved shadowgraph imaging. Ni and O atomic emissions decreased with increasing gas pressure; however, near the critical point the intensities reached local maxima, probably due to the enhancement of the plasma excitation and effective quenching resulting from the large density fluctuation.

  3. Pulsed laser ablation plasmas generated in CO{sub 2} under high-pressure conditions up to supercritical fluid

    SciTech Connect

    Kato, Toru; Stauss, Sven; Kato, Satoshi; Urabe, Keiichiro; Terashima, Kazuo; Baba, Motoyoshi; Suemoto, Tohru

    2012-11-26

    Pulsed laser ablation of solids in supercritical media has a large potential for nanomaterials fabrication. We investigated plasmas generated by pulsed laser ablation of Ni targets in CO{sub 2} at pressures ranging from 0.1 to 16 MPa at 304.5 K. Plasma species were characterized by optical emission spectroscopy, and the evolution of cavitation bubbles and shockwaves were observed by time-resolved shadowgraph imaging. Ni and O atomic emissions decreased with increasing gas pressure; however, near the critical point the intensities reached local maxima, probably due to the enhancement of the plasma excitation and effective quenching resulting from the large density fluctuation.

  4. Simultaneous observation of nascent plasma and bubble induced by laser ablation in water with various pulse durations

    SciTech Connect

    Tamura, Ayaka Matsumoto, Ayumu; Nishi, Naoya; Sakka, Tetsuo; Fukami, Kazuhiro

    2015-05-07

    We investigate the effects of pulse duration on the dynamics of the nascent plasma and bubble induced by laser ablation in water. To examine the relationship between the nascent plasma and the bubble without disturbed by shot-to-shot fluctuation, we observe the images of the plasma and the bubble simultaneously by using two intensified charge coupled device detectors. We successfully observe the images of the plasma and bubble during the pulsed-irradiation, when the bubble size is as small as 20 μm. The light-emitting region of the plasma during the laser irradiation seems to exceed the bubble boundary in the case of the short-pulse (30-ns pulse) irradiation, while the size of the plasma is significantly smaller than that of the bubble in the case of the long-pulse (100-ns pulse) irradiation. The results suggest that the extent of the plasma quenching in the initial stage significantly depends on the pulse duration. Also, we investigate how the plasma-bubble relationship in the very early stage affects the shape of the atomic spectral lines observed at the later delay time of 600 ns. The present work gives important information to obtain high quality spectra in the application of underwater laser-induced breakdown spectroscopy, as well as to clarify the mechanism of liquid-phase laser ablation.

  5. Optical time of flight studies of lithium plasma in double pulse laser ablation: Evidence of inverse Bremsstrahlung absorption

    SciTech Connect

    Sivakumaran, V.; Joshi, H. C.; Singh, R. K.; Kumar, Ajai

    2014-06-15

    The early stage of formation of lithium plasma in a collinear—double pulse laser ablation mode has been studied using optical time of flight (OTOF) spectroscopy as a function of inter-pulse delay time, the distance from the target surface and the fluence of the ablation lasers. The experimental TOF measurements were carried out for lithium neutral (670.8 nm and 610.3 nm), and ionic (548.4 nm and 478.8 nm) lines. These experimental observations have been compared with that for single pulse laser ablation mode. It is found that depending on the fluence and laser pulse shape of the first pre-ablation laser and the second main ablation laser, the plasma plume formation and its characteristic features can be described in terms of plume-plume or laser-plume interaction processes. Moreover, the enhancement in the intensity of Li neutral and ionic lines is observed when the laser-plume interaction is the dominant process. Here, we see the evidence of the role of inverse Bremsstrahlung absorption process in the initial stage of formation of lithium plasma in this case.

  6. Synthesis of higher diamondoids by pulsed laser ablation plasmas in supercritical CO2

    NASA Astrophysics Data System (ADS)

    Nakahara, Sho; Stauss, Sven; Kato, Toru; Sasaki, Takehiko; Terashima, Kazuo

    2011-06-01

    Pulsed laser ablation (wavelength 532 nm; fluence 18 J/cm2; pulse width 7 ns; repetition rate 10 Hz) of highly oriented pyrolytic graphite was conducted in adamantane-dissolved supercritical CO2 with and without cyclohexane as a cosolvent. Micro-Raman spectroscopy of the products revealed the presence of hydrocarbons possessing sp3-hybridized carbons similar to diamond structures. The synthesis of diamantane and other possible diamondoids consisting of up to 12 cages was confirmed by gas chromatography-mass spectrometry. Furthermore, gas chromatography-mass spectrometry measurements of samples before and after pyrolysis treatment indicate the synthesis of the most compact decamantane, namely, superadamantane. It is thought that oxidant species originating from CO2 during pulsed laser ablation might lead to the selective dissociation of C-H bonds, enabling the synthesis of low H/C ratio molecules. Therefore, laser ablation in supercritical CO2 is proposed as a practical method for synthesizing diamondoids.

  7. A study of ablation, spatial, and temporal characteristics of laser-induced plasmas generated by multiple collinear pulses.

    PubMed

    Galbács, G; Jedlinszki, N; Herrera, K; Omenetto, N; Smith, B W; Winefordner, J D

    2010-02-01

    Multi-pulse laser-induced breakdown spectroscopy (LIBS) in the collinear pulse configuration with time-integrating detection was performed on metallic samples in ambient air in an effort to clarify the contributing processes responsible for the signal enhancement observed in comparison with single-pulse excitation. Complementary experiments were also carried out on another LIBS setup using detection by an imaging spectrograph with high time resolution. The effects of laser bursts consisting of up to seven ns-range pulses from Nd-doped solid-state lasers operating at their fundamental wavelength and separated by 8.5-50 micros time gaps was studied. The ablation and emission characteristics of the generated plasmas were investigated using light profilometry, microscopy, plasma imaging, emission distribution mapping, time-resolved line emission monitoring, and plasma temperature calculations. The experimental data suggest that the two contributing processes mainly responsible for the signal enhancement effect are the plume reheating caused by the sequential laser pulses and, more dominantly, the increased material ablation attributed to the lower breakdown threshold for the preheated (molten) sample surface and/or the reduced background gas pressure behind the shockwave of preceding pulses. PMID:20149277

  8. Simulation of nanosecond pulsed laser ablation of copper samples: A focus on laser induced plasma radiation

    NASA Astrophysics Data System (ADS)

    Aghaei, M.; Mehrabian, S.; Tavassoli, S. H.

    2008-09-01

    A thermal model for nanosecond pulsed laser ablation of Cu in one dimension and in ambient gas, He at 1 atm, is proposed in which equations concerning heat conduction in the target and gas dynamics in the plume are solved. These equations are coupled to each other through the energy and mass balances at interface between the target and the vapor and also Knudsen layer conditions. By assumption of local thermal equilibrium, Saha-Eggert equations are used to investigate plasma formation. The shielding effect of the plasma, due to photoionization and inverse bremsstrahlung processes, is considered. Bremsstrahlung and blackbody radiation and spectral emissions of the plasma are also investigated. Spatial and temporal distribution of the target temperature, number densities of Cu and He, pressure and temperature of the plume, bremsstrahlung and blackbody radiation, and also spectral emissions of Cu at three wavelengths (510, 516, and 521 nm) are obtained. Results show that the spectral power of Cu lines has the same pattern as CuI relative intensities from National Institute of Standard and Technology. Investigation of spatially integrated bremsstrahlung and blackbody radiation, and also Cu spectral emissions indicates that although in early times the bremsstrahlung radiation dominates the two other radiations, the Copper spectral emission is the dominant radiation in later times. It should be mentioned that the blackbody radiation has the least values in both time intervals. The results can be used for prediction of the optimum time and position of the spectral line emission, which is applicable in some time resolved spectroscopic techniques such as laser induced breakdown spectroscopy. Furthermore, the results suggest that for distinguishing between the spectral emission and the bremsstrahlung radiation, a spatially resolved spectroscopy can be used instead of the time resolved one.

  9. Secondary plasma formation after single pulse laser ablation underwater and its advantages for laser induced breakdown spectroscopy (LIBS).

    PubMed

    Gavrilović, M R; Cvejić, M; Lazic, V; Jovićević, S

    2016-06-01

    In this work we present studies of spatial and temporal plasma evolution after single pulse ablation of an aluminium target in water. The laser ablation was performed using 20 ns long pulses emitted at 1064 nm. The plasma characterization was performed by fast photography, the Schlieren technique, shadowgraphy and optical emission spectroscopy. The experimental results indicate the existence of two distinct plasma stages: the first stage has a duration of approximately 500 ns from the laser pulse, and is followed by a new plasma growth starting from the crater center. The secondary plasma slowly evolves inside the growing vapor bubble, and its optical emission lasts over several tens of microseconds. Later, the hot glowing particles, trapped inside the vapor cavity, were detected during the whole cycle of the bubble, where the first collapse occurs after 475 μs from the laser pulse. Differences in the plasma properties during the two evolution phases are discussed, with an accent on the optical emission since its detection is of primary importance for LIBS. Here we demonstrate that the LIBS signal quality in single pulse excitation underwater can be greatly enhanced by detecting only the secondary plasma emission, and also by applying long acquisition gates (in the order of 10-100 μs). The presented results are of great importance for LIBS measurements inside a liquid environment, since they prove that a good analytical signal can be obtained by using nanosecond pulses from a single commercial laser source and by employing cost effective, not gated detectors. PMID:27180875

  10. Pulsed Laser Ablation of Soft Biological Tissues

    NASA Astrophysics Data System (ADS)

    Vogel, Alfred; Venugopalan, Vasan

    In this chapter we focus on the key elements that form our current understanding of the mechanisms of pulsed laser ablation of soft biological tissues. We present a conceptual framework providing mechanistic links between various ablation applications and the underlying thermodynamic and phase change processes [1]. We define pulsed laser ablation as the use of laser pulses with duration of ~1 ms or less for the incision or removal of tissue regardless of the photophysical or photochemical processes involved. However, we will confine this presentation to pulsed ablation performed on a tissue level that does not involve laser-induced plasma formation. Ablation processes within transparent tissues or cells resulting from non-linear absorption have been considered in reviews by Vogel and Venugopalan [1] and by Vogel and co-workers [2].

  11. Synthesis of higher diamondoids by pulsed laser ablation plasmas in supercritical CO{sub 2}

    SciTech Connect

    Nakahara, Sho; Stauss, Sven; Kato, Toru; Terashima, Kazuo; Sasaki, Takehiko

    2011-06-15

    Pulsed laser ablation (wavelength 532 nm; fluence 18 J/cm{sup 2}; pulse width 7 ns; repetition rate 10 Hz) of highly oriented pyrolytic graphite was conducted in adamantane-dissolved supercritical CO{sub 2} with and without cyclohexane as a cosolvent. Micro-Raman spectroscopy of the products revealed the presence of hydrocarbons possessing sp{sup 3}-hybridized carbons similar to diamond structures. The synthesis of diamantane and other possible diamondoids consisting of up to 12 cages was confirmed by gas chromatography-mass spectrometry. Furthermore, gas chromatography-mass spectrometry measurements of samples before and after pyrolysis treatment indicate the synthesis of the most compact decamantane, namely, superadamantane. It is thought that oxidant species originating from CO{sub 2} during pulsed laser ablation might lead to the selective dissociation of C-H bonds, enabling the synthesis of low H/C ratio molecules. Therefore, laser ablation in supercritical CO{sub 2} is proposed as a practical method for synthesizing diamondoids.

  12. Ad-hoc design of temporally shaped fs laser pulses based on plasma dynamics for deep ablation in fused silica

    NASA Astrophysics Data System (ADS)

    Hernandez-Rueda, J.; Siegel, J.; Puerto, D.; Galvan-Sosa, M.; Gawelda, W.; Solis, J.

    2013-07-01

    We have analyzed the ablation depth yield of fused silica irradiated with shaped pulse trains with a separation of 500 fs and increasing or decreasing intensity envelopes. This temporal separation value is extracted from previous studies on ablation dynamics upon irradiation with transform-limited 100 fs laser pulses. The use of decreasing intensity pulse trains leads to a strong increase of the induced ablation depth when compared to the behavior, at the same pulse fluence, of intensity increasing pulse trains. In addition, we have studied the material response under stretched (500 fs, FWHM) and transform-limited (100 fs, FWHM) pulses, for which avalanche or multiphoton ionization respectively dominates the carrier generation process. The comparison of the corresponding evolution of the ablated depth vs. fluence suggests that the use of pulse trains with decreasing intensity at high fluences should lead to enhanced single exposure ablation depths, beyond the limits corresponding to MPI- or AI-alone dominated processes.

  13. INTERACTION OF LASER RADIATION WITH MATTER. LASER PLASMA: Comparative study of the ablation of materials by femtosecond and pico- or nanosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Kononenko, Taras V.; Konov, Vitalii I.; Garnov, Sergei V.; Danielius, R.; Piskarskas, A.; Tamosauskas, G.; Dausinger, F.

    1999-08-01

    A series of studies was carried out on the ablation of steel, Si3N4 ceramic, and diamond in air by femtosecond (200 and 900 fs) pulses of different wavelengths (532 and 266 nm) and in a wide energy density range (1 — 103 J cm-2 ). The ablation rates were measured for different geometries of the irradiation surface [a shallow crater and a channel with a high (up to 10) aspect ratio]. The ablation rates (in a shallow crater) and the morphologies of the irradiated surface were compared for femtosecond and longer (220 ps, 7 ns) pulses. The role of the laser-generated plasma in the ablation of materials by subpicosecond pulses as well as the prospects for the practical application of ultrashort laser pulses in the processing of materials are analysed.

  14. Critical assessment of the issues in the modeling of ablation and plasma expansion processes in the pulsed laser deposition of metals

    SciTech Connect

    Marla, Deepak; Bhandarkar, Upendra V.; Joshi, Suhas S.

    2011-01-15

    This paper presents a review on the modeling of ablation and plasma expansion processes in the pulsed laser deposition of metals. The ablation of a target is the key process that determines the amount of material to be deposited; while, the plasma expansion governs the characteristics of the deposited material. The modeling of ablation process involves a study of two complex phenomena: (i) laser-target interaction and (ii) plasma formation and subsequent shielding of the incoming radiation. The laser-target interaction is a function of pulse duration, which is captured by various models that are described in this paper. The plasma produced as a result of laser-target interaction, further interacts with the incoming radiation, causing the shielding of the target. The shielding process has been modeled by considering the various photon absorption mechanisms operative inside the plasma, namely: inverse Bremsstrahlung, photoionization, and Mie absorption. Concurrently, the plasma expands freely until the ablated material gets deposited on the substrate. Various models describing the plasma expansion process have been presented. The ability of the theoretical models in predicting various ablation and plasma characteristics has also been compared with the relevant experimental data from the literature. The paper concludes with identification of critical issues and recommendations for future modeling endeavors.

  15. Atomic Processes in Emission Characteristics of a Lithium Plasma Plume Formed by Double-Pulse Laser Ablation

    NASA Astrophysics Data System (ADS)

    Sivakumaran, V.; Ajai, Kumar; K. Singh, R.; Prahlad, V.; C. Joshi, H.

    2013-03-01

    High resolution spectral analysis of lithium plasma formed by single and double laser ablation has been undertaken to understand the plume-laser interaction, especially at the early stages of the plasma plume. In order to identify different atomic processes in evolving plasma, time resolved spectral emission studies at different inter-pulse delays have been performed for ionic and neutral lithium lines emitting from different levels. Along with the enhancement in emission intensity, a large line broadening and spectral shift, especially in the case of excited state transition Li I 610.3 nm have been observed in the presence of the second pulse. This broadening and shift gradually decrease with increasing time delay. Another interesting feature is the appearance of a multi-component structure in the ionic line at 548.4 nm and these components change conversely into a single structure at the later stages of the plasma. The multi-component structures are correlated with the presence of different velocity (temperature) distributions in non-LTE conditions. Atomic analyses by computing photon emissivity coefficients with an ADAS code have been used to identify the above processes.

  16. Plasma-mediated ablation of biofilm contamination

    NASA Astrophysics Data System (ADS)

    Guo, Zhixiong; Wang, Xiaoliang; Huang, Huan

    2010-12-01

    Ultra-short pulsed laser removal of thin biofilm contamination on different substrates has been conducted via the use of plasma-mediated ablation. The biofilms were formed using sheep whole blood. The ablation was generated using a 1.2 ps ultra-short pulsed laser with wavelength centered at 1552 nm. The blood contamination was transformed into plasma and collected with a vacuum system. The single line ablation features have been measured. The ablation thresholds of blood contamination and bare substrates were determined. It is found that the ablation threshold of the blood contamination is lower than those of the beneath substrates including the glass slide, PDMS, and human dermal tissues. The ablation effects of different laser parameters (pulse overlap rate and pulse energy) were studied and ablation efficiency was measured. Proper ablation parameters were found to efficiently remove contamination with maximum efficiency and without damage to the substrate surface for the current laser system. Complete removal of blood contaminant from the glass substrate surface and freeze-dried dermis tissue surface was demonstrated by the USP laser ablation with repeated area scanning. No obvious thermal damage was found in the decontaminated glass and tissue samples.

  17. Ablation enhancement of silicon by ultrashort double-pulse laser ablation

    SciTech Connect

    Zhao, Xin; Shin, Yung C.

    2014-09-15

    In this study, the ultrashort double-pulse ablation of silicon is investigated. An atomistic simulation model is developed to analyze the underlying physics. It is revealed that the double-pulse ablation could significantly increase the ablation rate of silicon, compared with the single pulse ablation with the same total pulse energy, which is totally different from the case of metals. In the long pulse delay range (over 1 ps), the enhancement is caused by the metallic transition of melted silicon with the corresponding absorption efficiency. At ultrashort pulse delay (below 1 ps), the enhancement is due to the electron excitation by the first pulse. The enhancement only occurs at low and moderate laser fluence. The ablation is suppressed at high fluence due to the strong plasma shielding effect.

  18. Formation of diatomic molecular radicals in reactive nitrogen-carbon plasma generated by electron cyclotron resonance discharge and pulsed laser ablation

    SciTech Connect

    Liang, Peipei; Li, Yanli; You, Qinghu; Cai, Hua; Yang, Xu; Sun, Jian; Xu, Ning; Wu, Jiada

    2014-04-15

    The reactive nitrogen-carbon plasma generated by electron cyclotron resonance (ECR) microwave discharge of N{sub 2} gas and pulsed laser ablation of a graphite target was characterized spectroscopically by time-integrated and time-resolved optical emission spectroscopy with space resolution for a study of gas-phase reactions and molecular radical formation in the plasma. The plasma exhibits very high reactivity compared with the plasma generated solely by ECR discharge or by pulsed laser ablation and contains highly excited species originally present in the ambient gaseous environment and directly ablated from the target as well as formed as the products of gas-phase reactions occurring in the plasma. The space distribution and the time evolution of the plasma emission give an access to the gas-phase reactions for the formation of C{sub 2} and CN radicals, revealing that C{sub 2} radicals are formed mainly in the region near the target while CN radicals can be formed in a much larger region not only in the vicinity of the target, but especially in the region near a substrate far away from the target.

  19. Ultraviolet femtosecond and nanosecond laser ablation of silicon: Ablation efficiency and laser-induced plasma expansion

    SciTech Connect

    Zeng, Xianzhong; Mao, Xianglei; Greif, Ralph; Russo, Richard E.

    2004-03-23

    Femtosecond laser ablation of silicon in air was studied and compared with nanosecond laser ablation at ultraviolet wavelength (266 nm). Laser ablation efficiency was studied by measuring crater depth as a function of pulse number. For the same number of laser pulses, the fs-ablated crater was about two times deeper than the ns-crater. The temperature and electron number density of the pulsed laser-induced plasma were determined from spectroscopic measurements. The electron number density and temperature of fs-pulse plasmas decreased faster than ns-pulse plasmas due to different energy deposition mechanisms. Images of the laser-induced plasma were obtained with femtosecond time-resolved laser shadowgraph imaging. Plasma expansion in both the perpendicular and the lateral directions to the laser beam were compared for femtosecond and nanosecond laser ablation.

  20. Mechanism study of skin tissue ablation by nanosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Fang, Qiyin

    Understanding the fundamental mechanisms in laser tissue ablation is essential to improve clinical laser applications by reducing collateral damage and laser pulse energy requirement. The motive of this dissertation is to study skin tissue ablation by nanosecond laser pulses in a wide spectral region from near-infrared to ultraviolet for a clear understanding of the mechanism that can be used to improve future design of the pulsed lasers for dermatology and plastic surgery. Multiple laser and optical configurations have been constructed to generate 9 to 12ns laser pulses with similar profiles at 1064. 532, 266 and 213nm for this study of skin tissue ablation. Through measurements of ablation depth as a function cf laser pulse energy, the 589nm spectral line in the secondary radiation from ablated skin tissue samples was identified as the signature of the occurrence of ablation. Subsequently, this spectral signature has been used to investigate the probabilistic process of the ablation near the threshold at the four wavelengths. Measurements of the ablation probability were conducted as a function of the electrical field strength of the laser pulse and the ablation thresholds in a wide spectral range from 1064nm to 213nm were determined. Histology analysis and an optical transmission method were applied in assessing of the ablation depth per pulse to study the ablation process at irradiance levels higher than threshold. Because more than 70% of the wet weight of the skin tissue is water, optical breakdown and backscattering in water was also investigated along with a nonlinear refraction index measurement using a z-scan technique. Preliminary studies on ablation of a gelatin based tissue phantom are also reported. The current theoretical models describing ablation of soft tissue ablation by short laser pulses were critically reviewed. Since none of the existing models was found capable of explaining the experimental results, a new plasma-mediated model was developed

  1. Pulsed laser ablation and deposition of niobium carbide

    NASA Astrophysics Data System (ADS)

    Sansone, M.; De Bonis, A.; Santagata, A.; Rau, J. V.; Galasso, A.; Teghil, R.

    2016-06-01

    NbC crystalline films have been deposited in vacuum by ultra-short pulsed laser deposition technique. The films have been characterized by transmission and scanning electron microscopies and by X-ray diffraction. To clarify the ablation-deposition mechanism, the plasma produced by the ablation process has been characterized by optical emission spectroscopy and fast imaging. A comparison of the results with those obtained by ns pulsed deposition of the same target has been carried out.

  2. Simulation of Double-Pulse Laser Ablation

    SciTech Connect

    Povarnitsyn, Mikhail E.; Khishchenko, Konstantin V.; Levashov, Pavel R.; Itina, Tatian E.

    2010-10-08

    We investigate the physical reasons of a strange decrease in the ablation depth observed in femtosecond double-pulse experiments with increasing delay between the pulses. Two ultrashort pulses of the same energy produce the crater which is less than that created by a single pulse. Hydrodynamic simulation shows that the ablation mechanism is suppressed when the delay between the pulses exceeds the electron-ion relaxation time. In this case, the interaction of the second laser pulse with the expanding target material leads to the formation of the second shock wave suppressing the rarefaction wave created by the first pulse. The modeling of the double-pulse ablation for different delays between pulses confirms this explanation.

  3. Computational modeling of ultra-short-pulse ablation of enamel

    SciTech Connect

    London, R.A.; Bailey, D.S.; Young, D.A.

    1996-02-29

    A computational model for the ablation of tooth enamel by ultra-short laser pulses is presented. The role of simulations using this model in designing and understanding laser drilling systems is discussed. Pulses of duration 300 sec and intensity greater than 10{sup 12} W/cm{sup 2} are considered. Laser absorption proceeds via multi-photon initiated plasma mechanism. The hydrodynamic response is calculated with a finite difference method, using an equation of state constructed from thermodynamic functions including electronic, ion motion, and chemical binding terms. Results for the ablation efficiency are presented. An analytic model describing the ablation threshold and ablation depth is presented. Thermal coupling to the remaining tissue and long-time thermal conduction are calculated. Simulation results are compared to experimental measurements of the ablation efficiency. Desired improvements in the model are presented.

  4. Dynamics of pulsed laser ablation plasmas in high-density CO2 near the critical point investigated by time-resolved shadowgraph imaging

    NASA Astrophysics Data System (ADS)

    Urabe, Keiichiro; Kato, Toru; Himeno, Shohei; Kato, Satoshi; Stauss, Sven; Baba, Motoyoshi; Suemoto, Tohru; Terashima, Kazuo

    2013-09-01

    Pulsed laser ablation (PLA) plasmas generated in high-density gases and liquids are promising for the synthesis of nanomaterials. However, the characteristics of such plasmas are still not well understood. In order to improve the understandings of PLA plasmas in high-density fluids including gases, liquids, and supercritical fluids (SCFs), we have investigated the dynamics of PLA plasmas in high-density carbon dioxide (CO2) . We report on experimental results of time-resolved shadowgraph imaging, from the generation of plasma plume to the extinction of cavitation bubbles. Shadowgraph images revealed that the PLA plasma dynamics showed two distinct behaviors. These are divided by gas-liquid coexistence curve and the so-called Widom line, which separates gas-like and liquid-like SCF domains. Furthermore, cavitation bubble observed in liquid CO2 near the critical point showed peculiar characteristics, the formation of an inner bubble and an outer shell structure, which so far has never been reported. The experiments indicate that thermophysical properties of PLA plasmas can be tuned by controlling solvent temperature and pressure around the critical point, which may be useful for materials processing. This work was supported financially in part by a Grant-in-Aid for Scientific Research on Innovative Areas (No. 21110002) from the Ministry of Education, Culture, Sports, Science, and Technology of Japan.

  5. Optodynamic aspect of a pulsed laser ablation process

    NASA Astrophysics Data System (ADS)

    Hrovatin, Rok; Možina, Janez

    1995-02-01

    A study of a pulsed laser ablation process is presented from a novel, optodynamic aspect. By quantitative analysis of laser-induced bulk ultrasonic and blast waves in the air the ablation dynamics is characterized. In this way the influence of the laser pulse parameters and of the interacting material on the ablation process was assessed. By the analysis of the laser drilling process of thin layered samples the material influence was demonstrated. Besides the ultrasonic evaluation of the laser pulse power density the plasma shielding for 10 ns laser pulses was analyzed by the same method. All measurements were noncontact. Bulk waves in the solid and blast waves in the air were measured simultaneously, an interferometric and a probe beam deflection method were used, respectively.

  6. PULSED LASER ABLATION OF CEMENT AND CONCRETE

    EPA Science Inventory

    Laser ablation was investigated as a means of removing radioactive contaminants from the surface and near-surface regions of concrete from nuclear facilities. We present the results of ablation tests on cement and concrete samples using a pulsed Nd:YAG laser with fiber optic beam...

  7. Hydrodynamic Efficiency of Ablation Propulsion with Pulsed Ion Beam

    SciTech Connect

    Buttapeng, Chainarong; Yazawa, Masaru; Harada, Nobuhiro; Suematsu, Hisayuki; Jiang Weihua; Yatsui, Kiyoshi

    2006-05-02

    This paper presents the hydrodynamic efficiency of ablation plasma produced by pulsed ion beam on the basis of the ion beam-target interaction. We used a one-dimensional hydrodynamic fluid compressible to study the physics involved namely an ablation acceleration behavior and analyzed it as a rocketlike model in order to investigate its hydrodynamic variables for propulsion applications. These variables were estimated by the concept of ablation driven implosion in terms of ablated mass fraction, implosion efficiency, and hydrodynamic energy conversion. Herein, the energy conversion efficiency of 17.5% was achieved. In addition, the results show maximum energy efficiency of the ablation process (ablation efficiency) of 67% meaning the efficiency with which pulsed ion beam energy-ablation plasma conversion. The effects of ion beam energy deposition depth to hydrodynamic efficiency were briefly discussed. Further, an evaluation of propulsive force with high specific impulse of 4000s, total impulse of 34mN and momentum to energy ratio in the range of {mu}N/W was also analyzed.

  8. [INVITED] Control of femtosecond pulsed laser ablation and deposition by temporal pulse shaping

    NASA Astrophysics Data System (ADS)

    Garrelie, Florence; Bourquard, Florent; Loir, Anne--Sophie; Donnet, Christophe; Colombier, Jean-Philippe

    2016-04-01

    This study explores the effects of temporal laser pulse shaping on femtosecond pulsed laser deposition (PLD). The potential of laser pulses temporally tailored on ultrafast time scales is used to control the expansion and the excitation degree of ablation products including atomic species and nanoparticles. The ablation plume generated by temporally shaped femtosecond pulsed laser ablation of aluminum and graphite targets is studied by in situ optical diagnostic methods. Taking advantage of automated pulse shaping techniques, an adaptive procedure based on spectroscopic feedback regulates the irradiance for the enhancement of typical plasma features. Thin films elaborated by unshaped femtosecond laser pulses and by optimized sequence indicate that the nanoparticles generation efficiency is strongly influenced by the temporal shaping of the laser irradiation. The ablation processes leading either to the generation of the nanoparticles either to the formation of plasma can be favored by using a temporal shaping of the laser pulse. Insights are given on the possibility to control the quantity of the nanoparticles. The temporal laser pulse shaping is shown also to strongly modify the laser-induced plasma contents and kinetics for graphite ablation. Temporal pulse shaping proves its capability to reduce the number of slow radicals while increasing the proportion of monomers, with the addition of ionized species in front of the plume. This modification of the composition and kinetics of plumes in graphite ablation using temporal laser pulse shaping is discussed in terms of modification of the structural properties of deposited Diamond-Like Carbon films (DLC). This gives rise to a better understanding of the growth processes involved in femtosecond-PLD and picosecond-PLD of DLC suggesting the importance of neutral C atoms, which are responsible for the subplantation process.

  9. A Simulation of Laser Ablation During the Laser Pulse

    NASA Astrophysics Data System (ADS)

    Suzuki, Motoyuki; Ventzek, Peter L. G.; Sakai, Y.; Date, H.; Tagashira, H.; Kitamori, K.

    1996-10-01

    Charge damage considerations in plasma assisted etching are prompting the development of neutral beam sources. Already, anisotropic etching of has been demonstrated by neutral beams generated by exhausting heated ecthing gases into vacuum via a nozzle. Laser ablation of condensed etching gases may also be an attractive alternative means of generating neutral beams. Laser ablation coupled with electrical breakdown of the ablation plume may afford some degree of control over a neutral beam's dissociation fraction and ion content. Results from a Monte Carlo simulation of the laser ablation plume as it expands into vacuum at time-scales during the laser pulse will be presented. The model includes both heavy particle interactions and photochemistry. In particular, the influence of the initial particle angular distribution on the beam spread will be demonstrated as will the relationship between laser beam energy and initial ionization and dissociation fraction.

  10. CO2 Laser Absorption in Ablation Plasmas

    SciTech Connect

    Eckel, Hans-Albert; Tegel, Jochen; Schall, Wolfgang O.

    2006-05-02

    The impulse formation by laser ablation is limited by the premature absorption of the incident laser radiation in the initially produced cloud of ablation products. The power fraction of a CO2 laser pulse transmitted through a small hole in a POM sample for pulse energies of 35 to 150 J focused on a spot of 2 cm2 has been compared with the incident power. The plasma formation in vacuum and in air of 3500 Pa and the spread of the shock wave with velocities of 1.6 to 2.4 km/s in the low pressure air was observed by Schlieren photography. A sharp edged dark zone with a maximum extension of 10 to 12 mm away from the target surface develops within 5 {mu}s independently of the pressure and is assumed to be a plasma. In order to find out, if this is also the zone where the majority of the incident laser radiation is absorbed, a CO2 probe laser beam was directed through the expansion cloud parallel to and at various distances from the sample surface. The time behavior of the absorption signal of the probe beam has been measured and an absorption wave could be observed.

  11. Optical feedback signal for ultrashort laser pulse ablation of tissue

    SciTech Connect

    Kim, B.-M.; Feit, M.D.; Rubenchik, A.M.; Mammini, B.M.; Da Silva, L.B.

    1997-07-01

    An optical feedback system for controlled precise tissue ablation is discussed. Our setup includes an ultrashort pulse laser (USPL), and a diagnostic system using analysis of either tissue fluorescence or plasma emission luminescence. Current research is focused on discriminating hard and soft tissues such as bone and spinal cord during surgery using either technique. Our experimental observations exhibit considerable spectroscopic contrast between hard and soft tissue, and both techniques offer promise for a practical diagnostic system.

  12. Shadowgraph Imaging and Numerical Simulation of Cavitation Bubbles Formed in Pulsed Laser Ablation Plasmas in the Vicinity of the Critical Point of CO2

    NASA Astrophysics Data System (ADS)

    Muneoka, Hitoshi; Himeno, Shohei; Urabe, Keiichiro; Stauss, Sven; Baba, Motoyoshi; Suemoto, Tohru; Terashima, Kazuo

    2015-09-01

    The characteristic behavior of cavitation bubbles formed in pulsed laser ablation plasmas in supercritical CO2 were investigated by shadowgraph imaging and numerical simulations. The time evolution of the cavitation bubbles could be divided into three phases near the critical point: Expansion, Double layer formation, and Contraction. The distribution of the refractive index was estimated from the variation of the direction of the refracted light in the shockwave in the expansion phase. It was suggested that the cause of the reduction of the transmitted light in the outer shell in the double-layer phase was not due to refraction, and the contributions of nanoparticles and clusters generated in supercritical fluids were implied. The characteristics in time evolution of the bubble size in the contraction phase, in particular almost constant position of the interface in a relatively long time, was proposed to be due to zero surface tension by numerical simulations. The results suggest that the properties and fluid structure peculiar to SCF affect the structure of cavitation bubbles.

  13. Subsurface ablation of atherosclerotic plaque using ultrafast laser pulses

    PubMed Central

    Lanvin, Thomas; Conkey, Donald B.; Frobert, Aurelien; Valentin, Jeremy; Goy, Jean-Jacques; Cook, Stéphane; Giraud, Marie-Noelle; Psaltis, Demetri

    2015-01-01

    We perform subsurface ablation of atherosclerotic plaque using ultrafast pulses. Excised mouse aortas containing atherosclerotic plaque were ablated with ultrafast near-infrared (NIR) laser pulses. Optical coherence tomography (OCT) was used to observe the ablation result, while the physical damage was inspected in histological sections. We characterize the effects of incident pulse energy on surface damage, ablation hole size, and filament propagation. We find that it is possible to ablate plaque just below the surface without causing surface damage, which motivates further investigation of ultrafast ablation for subsurface atherosclerotic plaque removal. PMID:26203381

  14. Pulse laser ablation at water-air interface

    NASA Astrophysics Data System (ADS)

    Utsunomiya, Yuji; Kajiwara, Takashi; Nishiyama, Takashi; Nagayama, Kunihito; Kubota, Shiro

    2010-06-01

    We studied a new pulse laser ablation phenomenon on a liquid surface layer, which is caused by the difference between the refractive indices of the two materials involved. The present study was motivated by our previous study, which showed that laser ablation can occur at the interface between a transparent material and a gas or liquid medium when the laser pulse is focused through the transparent material. In this case, the ablation threshold fluence is reduced remarkably. In the present study, experiments were conducted in water and air in order to confirm this phenomenon for a combination of two fluid media with different refractive indices. This phenomenon was observed in detail by pulse laser shadowgraphy. A high-resolution film was used to record the phenomenon with a Nd:YAG pulse laser with 10-ns duration as a light source. The laser ablation phenomenon on the liquid surface layer caused by a focused Nd:YAG laser pulse with 1064-nm wavelength was found to be followed by the splashing of the liquid surface, inducing a liquid jet with many ligaments. The liquid jet extension velocity was around 1000 m/s in a typical case. The liquid jet decelerated drastically due to rapid atomization at the tips of the ligaments. The liquid jet phenomenon was found to depend on the pulse laser parameters such as the laser fluence on the liquid surface, laser energy, and laser beam pattern. The threshold laser fluence for the generation of a liquid jet was 20 J/cm2. By increasing the incident laser energy with a fixed laser fluence, the laser focused area increased, which eventually led to an increase in the size of the plasma column. The larger the laser energy, the larger the jet size and the longer the temporal behavior. The laser beam pattern was found to have significant effects on the liquid jet’s velocity, shape, and history.

  15. Plasma-mediated ablation: An optical tool for submicrometer surgery on neuronal and vascular systems

    PubMed Central

    Tsai, Philbert S.; Blinder, Pablo; Migliori, Benjamin J.; Neev, Joseph; Jin, Yishi; Squier, Jeffrey A.; Kleinfeld, David

    2009-01-01

    Plasma-mediated ablation makes use of high energy laser pulses to ionize molecules within the first few femtoseconds of the pulse. This process leads to a submicrometer-sized bubble of plasma that can ablate tissue with negligible heat transfer and collateral damage to neighboring tissue. We review the physics of plasma-mediated ablation and its use as a tool to generate targeted insults at the subcellular level to neurons and blood vessels deep within nervous tissue. Illustrative examples from axon regeneration and microvascular research illustrate the utility of this tool. We further discuss the use of ablation as an integral part of automated histology. PMID:19269159

  16. Magnetic Colloids By Pulsed Laser Ablation

    NASA Astrophysics Data System (ADS)

    Pandey, B. K.; Singh, M. K.; Agarwal, A.; Gopal, R.

    2011-06-01

    Colloidal magnetic nanoparticles have been successfully synthesized by nano second pules laser ablation of a cobalt slice immersed in liquid (distilled water) medium. The focused output of 1064 nm wavelength of pulsed Nd: YAG laser operating at 40 mJ/pulse is used for ablation. The liquid enviorment allows formation of colloids with nanoparticles in uniform particle diameter. Synchrotron X-ray powder diffraction (XRD) is used for the study of structural property of synthesized nanoparticles. The magnetic properties of cobalt nanoparticles are also investigated. The coercivity of is found to be 73 Oe. The optical properties have been determined by UV-visible absorption spectroscopy and band gap found to be 2.16 and 3.60 eV.

  17. Ablation of boron carbide for high-order harmonic generation of ultrafast pulses in laser-produced plasma

    NASA Astrophysics Data System (ADS)

    Ganeev, R. A.; Suzuki, M.; Kuroda, H.

    2016-07-01

    We demonstrate the generation of harmonics up to the 27th order (λ=29.9 nm) of 806 nm radiation in the boron carbide plasma. We analyze the advantages and disadvantages of this target compared with the ingredients comprising B4C (solid boron and graphite) by studying the plasma emission and harmonic spectra from three species. We compare different schemes of the two-color pump of B4C plasma, particularly using the second harmonics of 806 nm laser and optical parametric amplifier (1310 nm) as the assistant fields, as well as demonstrate the sum and difference frequency generation using the mixture of the wavelengths of two laser sources. These studies showed the advantages of the two-color pump of B4C plasma leading to the stable harmonic generation and the growth of harmonic conversion efficiency. We also show that the coincidence of harmonic and plasma emission wavelengths in most cases does not cause the enhancement or decrease of the conversion efficiency of this harmonic. Our spatial characterization of harmonics shows their on-axis modification depending on the conditions of frequency conversion.

  18. Performance and Controllability of Pulsed Ion Beam Ablation Propulsion

    SciTech Connect

    Yazawa, Masaru; Buttapeng, Chainarong; Harada, Nobuhiro; Suematsu, Hisayuki; Jiang Weihua; Yatsui, Kiyoshi

    2006-05-02

    We propose novel propulsion driven by ablation plasma pressures produced by the irradiation of pulsed ion beams onto a propellant. The ion beam ablation propulsion demonstrates by a thin foil (50 {mu}mt), and the flyer velocity of 7.7 km/s at the ion beam energy density of 2 kJ/cm2 adopted by using the Time-of-flight method is observed numerically and experimentally. We estimate the performance of the ion beam ablation propulsion as specific impulse of 3600 s and impulse bit density of 1700 Ns/m2 obtained from the demonstration results. In the numerical analysis, a one-dimensional hydrodynamic model with ion beam energy depositions is used. The control of the ion beam kinetic energy is only improvement of the performance but also propellant consumption. The spacecraft driven by the ion beam ablation provides high performance efficiency with short-pulsed ion beam irradiation. The numerical results of the advanced model explained latent heat and real gas equation of state agreed well with experimental ones over a wide range of the incident ion beam energy density.

  19. Comparative study of the ablation of materials by femtosecond and pico- or nanosecond laser pulses

    SciTech Connect

    Kononenko, Taras V; Konov, Vitalii I; Garnov, Sergei V; Danielius, R; Piskarskas, A; Tamosauskas, G; Dausinger, F

    1999-08-31

    A series of studies was carried out on the ablation of steel, Si{sub 3}N{sub 4} ceramic, and diamond in air by femtosecond (200 and 900 fs) pulses of different wavelengths (532 and 266 nm) and in a wide energy density range (1 - 10{sup 3} J cm{sup -2}). The ablation rates were measured for different geometries of the irradiation surface [a shallow crater and a channel with a high (up to 10) aspect ratio]. The ablation rates (in a shallow crater) and the morphologies of the irradiated surface were compared for femtosecond and longer (220 ps, 7 ns) pulses. The role of the laser-generated plasma in the ablation of materials by subpicosecond pulses as well as the prospects for the practical application of ultrashort laser pulses in the processing of materials are analysed. (interaction of laser radiation with matter. laser plasma)

  20. Laser ablation inductively coupled plasma mass spectrometry

    SciTech Connect

    Durrant, S.F.

    1996-07-01

    Laser ablation for solid sample introduction to inductively coupled plasma mass spectrometry for bulk and spatially-resolved elemental analysis is briefly reviewed. {copyright} {ital 1996 American Institute of Physics.}

  1. Optical ablation by high-power short-pulse lasers

    SciTech Connect

    Stuart, B.C.; Feit, M.D.; Herman, S.; Rubenchik, A.M.; Shore, B.W.; Perry, M.D.

    1996-02-01

    Laser-induced damage threshold measurements were performed on homogeneous and multilayer dielectrics and gold-coated optics at 1053 and 526 nm for pulse durations {tau} ranging from 140 fs to 1 ns. Gold coatings were found, both experimentally and theoretically, to be limited to 0.6 J/cm{sup 2} in the subpicosecond range for 1053-nm pulses. In dielectrics, we find qualitative differences in the morphology of damage and a departure from the diffusion-dominated {tau}{sup 1/2} scaling that indicate that damage results from plasma formation and ablation for {tau}{le}10 ps and from conventional heating and melting for {tau}{approx_gt}50 ps. A theoretical model based on electron production by multiphoton ionization, joule heating, and collisional (avalanche) ionization is in quantitative agreement with both the pulse-width and the wavelength scaling of experimental results. {copyright} {ital 1996 Optical Society of America.}

  2. Pulsed Plasma Thruster

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Dr. Tom Markusic, a propulsion research engineer at the Marshall Space Flight Center (MSFC), adjusts a diagnostic laser while a pulsed plasma thruster (PPT) fires in a vacuum chamber in the background. NASA/MSFC's Propulsion Research Center (PRC) is presently investigating plasma propulsion for potential use on future nuclear-powered spacecraft missions, such as human exploration of Mars.

  3. [Research on cells ablation characters by laser plasma].

    PubMed

    Han, Jing-hua; Zhang, Xin-gang; Cai, Xiao-tang; Duan, Tao; Feng, Guo-ying; Yang, Li-ming; Zhang, Ya-jun; Wang, Shao-peng; Li, Shi-wen

    2012-08-01

    The study on the mechanism of laser ablated cells is of importance to laser surgery and killing harmful cells. Three radiation modes were researched on the ablation characteristics of onion epidermal cells under: laser direct irradiation, focused irradiation and the laser plasma radiation. Based on the thermodynamic properties of the laser irradiation, the cell temperature rise and phase change have been analyzed. The experiments show that the cells damage under direct irradiation is not obvious at all, but the focused irradiation can cause cells to split and moisture removal. The removal shape is circular with larger area and rough fracture edges. The theoretical analysis found out that the laser plasma effects play a key role in the laser ablation. The thermal effects, radiation ionization and shock waves can increase the deposition of laser pulses energy and impact peeling of the cells, which will greatly increase the scope and efficiency of cell killing and is suitable for the cell destruction. PMID:23156745

  4. Short-wavelength ablation of solids: pulse duration and wavelength effects

    NASA Astrophysics Data System (ADS)

    Juha, Libor; Bittner, Michal; Chvostova, Dagmar; Letal, Vit; Krasa, Josef; Otcenasek, Zdenek; Kozlova, Michaela; Polan, Jiri; Prag, Ansgar R.; Rus, Bedrich; Stupka, Michal; Krzywinski, Jacek; Andrejczuk, Andrzej; Pelka, Jerzy B.; Sobierajski, Ryszard H.; Ryc, Leszek; Feldhaus, Josef; Boody, Frederick P.; Fiedorowicz, Henryk; Bartnik, Andrzej; Mikolajczyk, Janusz; Rakowski, Rafal; Kubat, P.; Pina, Ladislav; Grisham, Michael E.; Vaschenko, Georgiy O.; Menoni, Carmen S.; Rocca, Jorge J. G.

    2004-11-01

    For conventional wavelength (UV-Vis-IR) lasers delivering radiation energy to the surface of materials, ablation thresholds, ablation (etch) rates, and the quality of ablated structures often differ dramatically between short (typically nanosecond) and ultrashort (typically femtosecond) pulses. Various short-wavelength (l < 100 nm) lasers emitting pulses with durations ranging from ~ 10 fs to ~ 1 ns have recently been put into a routine operation. This makes it possible to investigate how the ablation characteristics depend on the pulse duration in the XUV spectral region. 1.2-ns pulses of 46.9-nm radiation delivered from a capillary-discharge Ne-like Ar laser (Colorado State University, Fort Collins), focused by a spherical Sc/Si multilayer-coated mirror were used for an ablation of organic polymers and silicon. Various materials were irradiated with ellipsoidal-mirror-focused XUV radiation (λ = 86 nm, τ = 30-100 fs) generated by the free-electron laser (FEL) operated at the TESLA Test Facility (TTF1 FEL) in Hamburg. The beam of the Ne-like Zn XUV laser (λ = 21.2 nm, τ < 100 ps) driven by the Prague Asterix Laser System (PALS) was also successfully focused by a spherical Si/Mo multilayer-coated mirror to ablate various materials. Based on the results of the experiments, the etch rates for three different pulse durations are compared using the XUV-ABLATOR code to compensate for the wavelength difference. Comparing the values of etch rates calculated for short pulses with those measured for ultrashort pulses, we can study the influence of pulse duration on XUV ablation efficiency. Ablation efficiencies measured with short pulses at various wavelengths (i.e. 86/46.9/21.2 nm from the above-mentioned lasers and ~ 1 nm from the double stream gas-puff Xe plasma source driven by PALS) show that the wavelength influences the etch rate mainly through the different attenuation lengths.

  5. Ultrashort pulse laser microsurgery system with plasma luminescence feedback control

    SciTech Connect

    Kim, B.M.; Feit, M.D.; Rubenchik, A.M.; Gold, D.M.; Darrow, C.B.; Da Silva, L.B.

    1997-11-10

    Plasma luminescence spectroscopy was used for precise ablation of bone tissue during ultrashort pulse laser (USPL) micro-spinal surgery. Strong contrast of the luminescence spectra between bone marrow and spinal cord provided the real time feedback control so that only bone tissue can be selectively ablated while preserving the spinal cord.

  6. Evaluation of ablation efficiency and surface morphology of human teeth upon irradiation with femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Shaheen, M. E.; Gagnon, J. E.; Fryer, B. J.

    2014-11-01

    This study investigates changes in ablation efficiency and surface morphology induced in human dental enamel and dentin upon interaction with femtosecond laser pulses at variable energies and number of laser pulses. Craters were created using a Ti:sapphire femtosecond laser ablation system operating at a wavelength of 785 nm, pulse width of 130 fs, and repetition rate of 20 Hz. Various techniques, such as optical and scanning electron microscopy and inductively coupled plasma mass spectrometry (ICP-MS), were used to evaluate ablation depth, amount of material ablated, and surface morphology of the craters. Ablation rate (ablation depth per pulse) was found to be lower in enamel than dentin with the maximum rate occurring at fluence of 12.4 J cm-2 in both materials. A drop in ablation rate was observed for fluence greater than 12.4 J cm-2 and was attributed to attenuation of laser energy due to interaction with the laser-generated particles. Above this fluence, signs of thermal effects, such as melting and formation of droplets of molten material at the sample surface, were observed. The response of the ICP-MS indicated that the amount of ablated material removed from dentin is greater than that removed from enamel by a factor of 1.5 or more at all investigated fluence.

  7. Hydrodynamic model for ultra-short pulse ablation of hard dental tissue

    SciTech Connect

    London, R.A.; Bailey, D.S.; Young, D.A.; Alley, W.E.; Feit, M.D.; Rubenchik, A.M.; Neev, J.

    1996-02-29

    A computational model for the ablation of tooth enamel by ultra-short laser pulses is presented. The role of simulations using this model in designing and understanding laser drilling systems is discussed. Pulses of duration 300 fsec and intensity greater than 10{sup 12} W/cm{sup 2} are considered. Laser absorption proceeds via multi-photon initiated plasma mechanism. The hydrodynamic response is calculated with a finite difference method, using an equation of state constructed from thermodynamic functions including electronic, ion motion, and chemical binding terms. Results for the ablation efficiency are presented. An analytic model describing the ablation threshold and ablation depth is presented. Thermal coupling to the remaining tissue and long-time thermal conduction are calculated. Simulation results are compared to experimental measurements of the ablation efficiency. Desired improvements in the model are presented.

  8. Ablation characteristics of quantum square pulse mode dental erbium laser

    NASA Astrophysics Data System (ADS)

    Lukač, Nejc; Suhovršnik, Tomaž; Lukač, Matjaž; Jezeršek, Matija

    2016-01-01

    Erbium lasers are by now an accepted tool for performing ablative medical procedures, especially when minimal invasiveness is desired. Ideally, a minimally invasive laser cutting procedure should be fast and precise, and with minimal pain and thermal side effects. All these characteristics are significantly influenced by laser pulse duration, albeit not in the same manner. For example, high cutting efficacy and low heat deposition are characteristics of short pulses, while vibrations and ejected debris screening are less pronounced at longer pulse durations. We report on a study of ablation characteristics on dental enamel and cementum, of a chopped-pulse Er:YAG [quantum square pulse (QSP)] mode, which was designed to reduce debris screening during an ablation process. It is shown that in comparison to other studied standard Er:YAG and Er,Cr:YSGG laser pulse duration modes, the QSP mode exhibits the highest ablation drilling efficacy with lowest heat deposition and reduced vibrations, demonstrating that debris screening has a considerable influence on the ablation process. By measuring single-pulse ablation depths, we also show that tissue desiccation during the consecutive delivery of laser pulses leads to a significant reduction of the intrinsic ablation efficacy that cannot be fully restored under clinical settings by rehydrating the tooth using an external water spray.

  9. Enhanced filament ablation of metals based on plasma grating in air

    NASA Astrophysics Data System (ADS)

    Wang, Di; Yuan, Shuai; Liu, Fengjiang; Ding, Liangen; Zeng, Heping

    2015-09-01

    We demonstrate efficient ablation of metals with filamentary plasma grating generated by two intense blue femtosecond filaments and a third focused infrared pulse. This scheme leads to significant promotion of ablation efficiency on metal targets in air in comparison with single infrared or blue filament with equal pulse energy. The reason is that the blue plasma grating firstly provides stronger intensity and a higher density of background electrons, then the delayed infrared pulse accelerates local electrons inside the plasma grating. These two processes finally results in robustly increased electron density and highly ionized metallic atoms.

  10. Enhanced filament ablation of metals based on plasma grating in air

    SciTech Connect

    Wang, Di; Liu, Fengjiang; Ding, Liangen; Yuan, Shuai; Zeng, Heping

    2015-09-15

    We demonstrate efficient ablation of metals with filamentary plasma grating generated by two intense blue femtosecond filaments and a third focused infrared pulse. This scheme leads to significant promotion of ablation efficiency on metal targets in air in comparison with single infrared or blue filament with equal pulse energy. The reason is that the blue plasma grating firstly provides stronger intensity and a higher density of background electrons, then the delayed infrared pulse accelerates local electrons inside the plasma grating. These two processes finally results in robustly increased electron density and highly ionized metallic atoms.

  11. Low-order harmonic generation in metal ablation plasmas in nanosecond and picosecond laser regimes

    SciTech Connect

    Lopez-Arias, M.; Oujja, M.; Sanz, M.; Castillejo, M.; Ganeev, R. A.; Boltaev, G. S.; Satlikov, N. Kh.; Tugushev, R. I.; Usmanov, T.

    2012-02-15

    Low-order harmonics, third and fifth, of IR (1064 nm) laser emission have been produced in laser ablation plasmas of the metals manganese, copper and silver. The harmonics were generated in a process triggered by laser ablation followed by frequency up-conversion of a fundamental laser beam that propagates parallel to the target surface. These studies were carried out in two temporal regimes by creating the ablation plasma using either nanosecond or picosecond pulses and then probing the plasma plume with pulses of the same duration. The spatiotemporal behavior of the generated harmonics was characterized and reveals the distinct composition and dynamics of the plasma species that act as nonlinear media, allowing the comparison of different processes that control the generation efficiency. These results serve to guide the choice of laser ablation plasmas to be used for efficient high harmonic generation of laser radiation.

  12. Metallic targets ablation by laser plasma production in a vacuum

    NASA Astrophysics Data System (ADS)

    Beilis, I. I.

    2016-03-01

    A model of metallic target ablation and metallic plasma production by laser irradiation is reported. The model considers laser energy absorption by the plasma, electron emission from hot targets and ion flux to the target from the plasma as well as an electric sheath produced at the target-plasma interface. The proposed approach takes into account that the plasma, partially shields the laser radiation from the target, and also converts absorbed laser energy to kinetic and potential energies of the charged plasma particles, which they transport not only through the ambient vacuum but also through the electrostatic sheath to the solid surface. Therefore additional plasma heating by the accelerated emitted electrons and target heating caused by bombardment of it by the accelerated ions are considered. A system of equations, including equations for solid heat conduction, plasma generation, and plasma expansion, is solved self-consistently. The results of calculations explain the measured dependencies of ablation yield (μ g/pulse) for Al, Ni, and Ti targets on laser fluence in range of (5-21)J/cm2 published previously by Torrisi et al.

  13. Ultrasound generated by a femtosecond and a picosecond laser pulse near the ablation threshold

    NASA Astrophysics Data System (ADS)

    Hébert, H.; Vidal, F.; Martin, F.; Kieffer, J.-C.; Nadeau, A.; Johnston, T. W.; Blouin, A.; Moreau, A.; Monchalin, J.-P.

    2005-08-01

    We have investigated high-frequency ultrasound generated by single laser pulses in thin (50μm) aluminum foils as a function of the laser fluence. Laser-pulse durations of 80fs and 270ps were used to compare the ultrasound generated in two very different regimes: thermoelastic and ablation. The measured rear-surface displacement induced by the ultrasound pulse is similar after 50-μm propagation through the foils for the two laser-pulse durations in the fluence range of 0.1-0.7J/cm2. For fluences greater than the ablation threshold (0.25 and 0.63J/cm2 for the 80-fs and 270-ps pulses, respectively), the ultrasound amplitude generated by the 270-ps laser pulse is increased significantly due to absorption of laser energy by the ablating plasma. This is not observed for the 80-fs laser pulse since ablation is produced well after the laser-pulse irradiation of the target. The measured surface displacement as a function of laser fluence is compared to the calculations of a one-dimensional fluid code for both laser-pulse durations. The model calculations agree in many ways with the experimental results, but some discrepancies are observed.

  14. Laser ablation of electronic materials including the effects of energy coupling and plasma interactions

    SciTech Connect

    Zeng, Xianzhong

    2004-12-10

    Many laser ablation applications such as laser drilling and micromachining generate cavity structures. The study of laser ablation inside a cavity is of both fundamental and practical significance. In this dissertation, cavities with different aspect ratios (depth/diameter) were fabricated in fused silica by laser micromachining. Pulsed laser ablation in the cavities was studied and compared with laser ablation on a flat surface. The formation of laser-induced plasmas in the cavities and the effects of the cavities on the ablation processes were investigated. The temperatures and electron number densities of the resulting laser-induced plasmas in the cavities were determined from spectroscopic measurements. Reflection and confinement effects by the cavity walls and plasma shielding were discussed to explain the increased temperature and electron number density with respect to increasing cavity aspect ratio. The temporal variations of the plasma temperature and electron number density inside the cavity decreased more rapidly than outside the cavity. The effect of laser energy on formation of a plasma inside a cavity was also investigated. Propagation of the shock wave generated during pulsed laser ablation in cavities was measured using laser shadowgraph imaging and compared with laser ablation on a flat surface. It is found that outside the cavity, after about 30 ns the radius of the expanding shock wave was proportional to t2/5, which corresponds to a spherical blast wave. The calculated pressures and temperatures of the shocked air outside of the cavities were higher than those obtained on the flat surface. Lasers with femtosecond pulse duration are receiving much attention for direct fabrication of microstructures due to their capabilities of high-precision ablation with minimal damage to the sample. We have also performed experimental studies of pulsed femtosecond laser ablation on the flat surface of silicon samples and compared results with pulsed nanosecond

  15. Effects of Two-Pulse Sequencing on Characteristics of Elementary Propellants for Ablative Laser Propulsion

    NASA Technical Reports Server (NTRS)

    Thompson, M. Shane; Pakhomov, Andrew V.; Herren, Kenneth A.

    2003-01-01

    This work continues on previous investigations of elementary propellants for Ablative Laser Propulsion (ALP). This paper details the experimental methods used for alignment of a non-colinear temporal pulse splitting apparatus. Spatial coincidence of the separate pulses is established, the pulses are delayed, and first data is reported on this pulse spacing effect on time-of-fight (TOF) measurements. This includes ion velocity and number density measurements, and this data is compared to results from a previous work. Also, first data on the experimental determination of the time required for the laser-induced plasma to become purely reflective to incident pulses is presented.

  16. Flyer Acceleration by Pulsed Ion Beam Ablation and Application for Space Propulsion

    SciTech Connect

    Harada, Nobuhiro; Buttapeng, Chainarong; Yazawa, Masaru; Kashine, Kenji; Jiang Weihua; Yatsui, Kiyoshi

    2004-02-04

    Flyer acceleration by ablation plasma pressure produced by irradiation of intense pulsed ion beam has been studied. Acceleration process including expansion of ablation plasma was simulated based on fluid model. And interaction between incident pulsed ion beam and a flyer target was considered as accounting stopping power of it. In experiments, we used ETIGO-II intense pulsed ion beam generator with two kinds of diodes; 1) Magnetically Insulated Diode (MID, power densities of <100 J/cm2) and 2) Spherical-focused Plasma Focus Diode (SPFD, power densities of up to 4.3 kJ/cm2). Numerical results of accelerated flyer velocity agreed well with measured one over wide range of incident ion beam energy density. Flyer velocity of 5.6 km/s and ablation plasma pressure of 15 GPa was demonstrated by the present experiments. Acceleration of double-layer target consists of gold/aluminum was studied. For adequate layer thickness, such a flyer target could be much more accelerated than a single layer. Effect of waveform of ion beam was also examined. Parabolic waveform could accelerate more efficiently than rectangular waveform. Applicability of ablation propulsion was discussed. Specific impulse of 7000{approx}8000 seconds and time averaged thrust of up to 5000{approx}6000N can be expected. Their values can be controllable by changing power density of incident ion beam and pulse duration.

  17. Ablation driven by hot electrons generated during the ignitor laser pulse in shock ignition

    NASA Astrophysics Data System (ADS)

    Piriz, A. R.; Rodriguez Prieto, G.; Tahir, N. A.; Zhang, Y.; Liu, S. D.; Zhao, Y. T.

    2012-12-01

    An analytical model for the ablation driven by hot electrons is presented. The hot electrons are assumed to be generated during the high intensity laser spike used to produce the ignitor shock wave in the shock ignition driven inertial fusion concept, and to carry on the absorbed laser energy in its totality. Efficient energy coupling requires to keep the critical surface sufficiently close to the ablation front and this goal can be achieved for high laser intensities provided that the laser wavelength is short enough. Scaling laws for the ablation pressure and the other relevant magnitudes of the ablation cloud are found in terms of the laser and target parameters. The effect of the preformed plasma assembled by the compression pulse, previous to the ignitor, is also discussed. It is found that a minimum ratio between the compression and the ignitor pulses would be necessary for the adequate matching of the corresponding scale lengths.

  18. Pulsed Plasma Accelerator Modeling

    NASA Technical Reports Server (NTRS)

    Goodman, M.; Kazeminezhad, F.; Owens, T.

    2009-01-01

    This report presents the main results of the modeling task of the PPA project. The objective of this task is to make major progress towards developing a new computational tool with new capabilities for simulating cylindrically symmetric 2.5 dimensional (2.5 D) PPA's. This tool may be used for designing, optimizing, and understanding the operation of PPA s and other pulsed power devices. The foundation for this task is the 2-D, cylindrically symmetric, magnetohydrodynamic (MHD) code PCAPPS (Princeton Code for Advanced Plasma Propulsion Simulation). PCAPPS was originally developed by Sankaran (2001, 2005) to model Lithium Lorentz Force Accelerators (LLFA's), which are electrode based devices, and are typically operated in continuous magnetic field to the model, and implementing a first principles, self-consistent algorithm to couple the plasma and power circuit that drives the plasma dynamics.

  19. Experiments and Theory of Ablation Plasma Ion Implantation

    NASA Astrophysics Data System (ADS)

    Gilgenbach, R. M.; Qi, B.; Lau, Y. Y.; Johnston, M. D.; Doll, G. L.; Lazarides, A.

    2000-10-01

    Research is underway to accelerate laser ablation plume ions for implantation into substrates. Ablation plasma ion implantation (APII) biases the deposition substrate to a large negative voltage. APII has the advantages of direct acceleration and implantation of ions from metals or any other solid targets. This process is environmentally friendly because it avoids the use of toxic gaseous precursors. Initial experiments are directed towards the implantation of iron ions into silicon substrates at negative voltages from 2-10 kV. A KrF laser ablates iron targets at pulse energies up to 600 mJ and typical repetition rates of 10 Hz. Parameters which can be varied include laser fluence, relative timing of laser and high voltage pulse, and target-to-substrate distance. Spectroscopic diagnostics yield Fe plasma plume electron temperatures up to about 10 eV. Analysis of films will compare surface morphology, hardness and adhesion between deposited Vs accelerated-implanted plumes. A simple one dimensional theory is developed [1] to calculate the implanted ion current, extracted from the ion matrix sheath, as a function of time for various substrate-plume separations. This model accurately recovers Lieberman's classic results when the plume front is initially in contact with the substrate. [1] B. Qi, Y. Y. Lau, and R. M. Gilgenbach, Appl. Phys. Lett. (to be published). * This research is supported by the National Science Foundation.

  20. Experimental measurement of ablation effects in plasma armature railguns

    SciTech Connect

    Parker, J.V.; Parsons, W.M.

    1986-01-01

    Experimental evidence supporting the importance of ablation in plasma armature railguns is presented. Experiments conducted using the HYVAX and MIDI-2 railguns are described. Several indirect effects of ablation are identified from the experimental results. An improved ablation model of plasma armature dynamics is proposed which incorporates the restrike process.

  1. Experimental measurement of ablation effects in plasma armature railguns

    NASA Astrophysics Data System (ADS)

    Parker, J. V.; Parsons, W. M.

    Experimental evidence supporting the importance of ablation in plasma armature railguns is presented. Experiments conducted using the HYVAX and MIDI-2 railguns are described. Several indirect effects of ablation are identified from the experimental results. An improved ablation model of plasma armature dynamics is proposed which incorporates the restrike process.

  2. Control of laser-ablation plasma potential with external electrodes

    SciTech Connect

    Isono, Fumika Nakajima, Mitsuo; Hasegawa, Jun; Kawamura, Tohru; Horioka, Kazuhiko

    2015-08-15

    The potential of a laser-ablation plasma was controlled stably up to +2 kV by using external ring electrodes. A stable electron sheath was formed between the plasma and the external electrodes by placing the ring electrodes away from the boundary of the drifting plasma. The plasma kept the potential for a few μs regardless of the flux change of the ablation plasma. We also found that the plasma potential changed with the expansion angle of the plasma from the target. By changing the distance between the plasma boundary and the external electrodes, we succeeded in controlling the potential of laser-ablation plasma.

  3. Rail gun performance and plasma characteristics due to wall ablation

    NASA Technical Reports Server (NTRS)

    Ray, P. K.

    1986-01-01

    The experiment of Bauer, et al. (1982) is analyzed by considering wall ablation and viscous drag in the plasma. Plasma characteristics are evaluated through a simple fluid-mechanical analysis considering only wall ablation. By equating the energy dissipated in the plasma with the radiation heat loss, the average properties of the plasma are determined as a function of time.

  4. Investigation of different liquid media and ablation times on pulsed laser ablation synthesis of aluminum nanoparticles

    NASA Astrophysics Data System (ADS)

    Baladi, Arash; Sarraf Mamoory, Rasoul

    2010-10-01

    Aluminum nanoparticles were synthesized by pulsed laser ablation of Al targets in ethanol, acetone, and ethylene glycol. Transmission Electron Microscope (TEM) and Scanning Electron Microscope (SEM) images, Particle size distribution diagram from Laser Particle Size Analyzer (LPSA), UV-visible absorption spectra, and weight changes of targets were used for the characterization and comparison of products. The experiments demonstrated that ablation efficiency in ethylene glycol is too low, in ethanol is higher, and in acetone is highest. Comparison between ethanol and acetone clarified that acetone medium leads to finer nanoparticles (mean diameter of 30 nm) with narrower size distribution (from 10 to 100 nm). However, thin carbon layer coats some of them, which was not observed in ethanol medium. It was also revealed that higher ablation time resulted in higher ablated mass, but lower ablation rate. Finer nanoparticles, moreover, were synthesized in higher ablation times.

  5. Pulsed Plasma Thruster Technology

    NASA Technical Reports Server (NTRS)

    1996-01-01

    The continuing emphasis on reducing costs and downsizing spacecraft is forcing increased emphasis on reducing the subsystem mass and integration costs. For many commercial, scientific, and Department of Defense space missions, onboard propulsion is either the predominant spacecraft mass or it limits the spacecraft lifetime. Electromagnetic-pulsed-plasma thrusters (PPT's) offer the combined benefits of extremely low average electric power requirements (1 to 150 W), high specific impulse (approx. 1000 sec), and system simplicity derived from the use of an inert solid propellant. Potential applications range from orbit insertion and maintenance of small satellites to attitude control for large geostationary communications satellites.

  6. Evaluation of physical parameters during the plasma-induced ablation of teeth

    NASA Astrophysics Data System (ADS)

    Niemz, Markolf H.

    1995-01-01

    The physical parameters of the plasma-induced ablation mechanism were investigated using a picosecond Nd:YLF laser system. The laser consists of a diode-pumped oscillator and a lamp- pumped regenerative amplifier. It operates at a wavelength of 1.053 micrometers with pulse durations of 30 ps and pulse energies up to 1 mJ. The laser beam was expanded to a diameter of 4 mm and focussed to spot sizes of about 30 micrometers . At these high power densities a localized plasma was induced at the focal spot. Surfaces of extracted human teeth were used as target material. In order to study the effect of accompanying shock waves, dye penetration tests, hardness tests and polarized microscopy were performed. At moderate pulse energies no significant impact of shock waves was observed. Because of this result, the terms `plasma- induced ablation' or `plasma-mediated ablation' are more appropriate for ablations solely induced by plasma ionization, and should be distinguished from photodisruptive ablations. In another series of experiments the generated plasma sparks were spectroscopically analyzed. From the measured spectra, mean plasma temperatures of about 5 eV and mean electron densities of about 1018/cm3 were estimated.

  7. Ablation of Myocardial Tissue With Nanosecond Pulsed Electric Fields

    PubMed Central

    Xie, Fei; Varghese, Frency; Pakhomov, Andrei G.; Semenov, Iurii; Xiao, Shu; Philpott, Jonathan; Zemlin, Christian

    2015-01-01

    Background Ablation of cardiac tissue is an essential tool for the treatment of arrhythmias, particularly of atrial fibrillation, atrial flutter, and ventricular tachycardia. Current ablation technologies suffer from substantial recurrence rates, thermal side effects, and long procedure times. We demonstrate that ablation with nanosecond pulsed electric fields (nsPEFs) can potentially overcome these limitations. Methods We used optical mapping to monitor electrical activity in Langendorff-perfused New Zealand rabbit hearts (n = 12). We repeatedly inserted two shock electrodes, spaced 2–4 mm apart, into the ventricles (through the entire wall) and applied nanosecond pulsed electric fields (nsPEF) (5–20 kV/cm, 350 ns duration, at varying pulse numbers and frequencies) to create linear lesions of 12–18 mm length. Hearts were stained either with tetrazolium chloride (TTC) or propidium iodide (PI) to determine the extent of ablation. Some stained lesions were sectioned to obtain the three-dimensional geometry of the ablated volume. Results In all animals (12/12), we were able to create nonconducting lesions with less than 2 seconds of nsPEF application per site and minimal heating (< 0.2°C) of the tissue. The geometry of the ablated volume was smoother and more uniform throughout the wall than typical for RF ablation. The width of the lesions could be controlled up to 6 mm via the electrode spacing and the shock parameters. Conclusions Ablation with nsPEFs is a promising alternative to radiofrequency (RF) ablation of AF. It may dramatically reduce procedure times and produce more consistent lesion thickness than RF ablation. PMID:26658139

  8. Pulsed Plasma Thruster Contamination

    NASA Technical Reports Server (NTRS)

    Myers, Roger M.; Arrington, Lynn A.; Pencil, Eric J.; Carter, Justin; Heminger, Jason; Gatsonis, Nicolas

    1996-01-01

    Pulsed Plasma Thrusters (PPT's) are currently baselined for the Air Force Mightysat II.1 flight in 1999 and are under consideration for a number of other missions for primary propulsion, precision positioning, and attitude control functions. In this work, PPT plumes were characterized to assess their contamination characteristics. Diagnostics included planar and cylindrical Langmuir probes and a large number of collimated quartz contamination sensors. Measurements were made using a LES 8/9 flight PPT at 0.24, 0.39, 0.55, and 1.2 m from the thruster, as well as in the backflow region behind the thruster. Plasma measurements revealed a peak centerline ion density and velocity of approx. 6 x 10(exp 12) cm(exp -3) and 42,000 m/s, respectively. Optical transmittance measurements of the quartz sensors after 2 x 10(exp 5) pulses showed a rapid decrease in plume contamination with increasing angle from the plume axis, with a barely measurable transmittance decrease in the ultraviolet at 90 deg. No change in optical properties was detected for sensors in the backflow region.

  9. Spectroscopic characterization of laser ablated silicon plasma

    NASA Astrophysics Data System (ADS)

    Shakeel, Hira; Mumtaz, M.; Shahzada, S.; Nadeem, A.; Haq, S. U.

    2014-06-01

    We report plasma parameters of laser ablated silicon plasma using the fundamental (1064 nm) and second harmonics (532 nm) of a Nd : YAG laser. The electron temperature and electron number density are evaluated using the Boltzmann plot method and Stark broadened line profile, respectively. The electron temperature and electron number density are deduced using the same laser irradiance 2-16 GW cm-2 for 1064 nm and 532 nm as 6350-7000 K and (3.42-4.44) × 1016 cm-3 and 6000-6400 K and (4.20-5.72) × 1016 cm-3, respectively. The spatial distribution of plasma parameters shows a decreasing trend of 8200-6300 K and (4.00-3.60) × 1016 cm-3 for 1064 nm and 6400-5500 K and (5.10-4.50) × 1016 cm-3 for 532 nm laser ablation. Furthermore, plasma parameters are also investigated at low pressure from 45 to 550 mbar, yielding the electron temperature as 4580-5535 K and electron number density as (1.51-2.12) × 1016 cm-3. The trend of the above-mentioned results is in good agreement with previous investigations. However, wavelength-dependent studies and the spatial evolution of plasma parameters have been reported for the first time.

  10. Density profile of a line plasma generated by laser ablation for laser wakefield acceleration

    NASA Astrophysics Data System (ADS)

    Kim, J.; Hwangbo, Y.; Ryu, W.-J.; Kim, K. N.; Park, S. H.

    2016-03-01

    An elongated line plasma generated by a laser ablation of an aluminum target was investigated, which can be used in the laser wakefield acceleration (LWFA) by employing ultra-intense laser pulse through the longitudinal direction of the plasma. To generate a uniform and long plasma channel along the propagation of ultra-intense laser pulse (main pulse), a cylindrical lens combined with a biprism was used to shape the intensity of a ns Nd:YAG laser (pre-pulse) on the Al target. A uniformity of laser intensity can be manipulated by changing the distance between the biprism and the target. The density profile of the plasma generated by laser ablation was measured using two interferometers, indicating that a 3-mm long uniform line plasma with a density of 6 × 1017 cm-3 could be generated. The density with main pulse was also measured and the results indicated that the density would increase further due to additional ionization of the plasma by the main ultra-intense laser pulse. The resulting plasma density, which is a crucial parameter for the LWFA, can be controlled by the intensity of the pre-pulse, the time delay between the pre- and main pulse, and the distance of the main pulse from the target surface.

  11. Ablation Plasma Ion Implantation Optimization and Deposition of Compound Coatings

    NASA Astrophysics Data System (ADS)

    Jones, M. C.; Qi, B.; Gilgenbach, R. M.; Johnston, M. D.; Lau, Y. Y.; Doll, G. L.; Lazarides, A.

    2002-10-01

    Ablation Plasma Ion Implantation (APII) utilizes KrF laser ablation plasma plumes to implant ions into pulsed, negatively-biased substrates [1]. Ablation targets are Ti foils and TiN disks. Substrates are Si wafers and Al, biased from 0 to -10 kV. Optimization experiments address: 1) configurations that reduce arcing, 2) reduction of particulate, and 3) deposition/implantation of compounds (e.g. TiN). Arcing is suppressed by positioning the target perpendicular (previously parallel) to the substrate. Thus, bias voltage can be applied at the same time as the KrF laser, resulting in higher ion current. This geometry also yields lower particulate. APII with TiN has the goal of hardened coatings with excellent adhesion. SEM, AFM, XPS, TEM, and scratch tests characterize properties of the thin films. Ti APII films at - 4kV are smoother with lower friction. 1. B. Qi, R.M. Gilgenbach, Y.Y. Lau, M.D. Johnston, J. Lian, L.M. Wang, G. L. Doll and A. Lazarides, APL, 78, 3785 (2001) * Research funded by NSF

  12. Synchronized videography of plasma plume expansion during femtosecond laser ablation

    NASA Astrophysics Data System (ADS)

    Paolasini, Steven; Kietzig, Anne

    2014-03-01

    Femtosecond lasers are gaining industrial interest for surface patterning and structuring because of the reduced heat effects to the surrounding material, resulting in a good quality product with a high aspect ratio. Analysis of the plasma plume generated during ablation can provide useful information about the laser-material interactions and thereby the quality of the resulting surface patterns. As a low-cost alternative to rather complicated ICCD camera setups, presented here is an approach based on filming the laser machining process with a high speed camera and tuning the frame rate of the camera to slightly lower than the laser pulse frequency. The delay in frequency between the laser and camera results in frames taken from sequential pulses. Each frame represents a later phase of plume expansion although taken from different pulses. Assuming equal plume evolution processes from pulse to pulse, the sequence of images obtained completes a plume expansion video. To test the assumption of homogeneity between sequential plumes, the camera can be tuned to the frequency of the laser, as to capture consecutive plumes at the same phase in their evolution. This approach enables a relatively low-cost, high resolution visualization of plasma plume evolution suitable for industrial micromachining applications with femtosecond lasers. Using this approach we illustrate differences in plume expansion at the example of machining homogeneous surface patterns in different liquid and gaseous processing environments.

  13. Suppression of Ablation in Femtosecond Double-Pulse Experiments

    SciTech Connect

    Povarnitsyn, M. E.; Khishchenko, K. V.; Levashov, P. R.; Itina, T. E.

    2009-11-06

    We report the physical reasons of a curious decrease in the crater depth observed for long delays in experiments with two successive femtosecond pulses. Detailed hydrodynamic modeling demonstrates that the ablation mechanism is dumped when the delay between the pulses exceeds the electron-ion relaxation time. In this case, the interaction of the second laser pulse with the expanding target material leads to the formation of the second shock wave suppressing the rarefaction wave created by the first pulse. The evidence of this effect follows from the pressure and density profiles obtained at different delays after the first laser pulse.

  14. Precision ablation of dental enamel using a subpicosecond pulsed laser.

    PubMed

    Rode, A V; Gamaly, E G; Luther-Davies, B; Taylor, B T; Graessel, M; Dawes, J M; Chan, A; Lowe, R M; Hannaford, P

    2003-12-01

    In this study we report the use of ultra-short-pulsed near-infrared lasers for precision laser ablation of freshly extracted human teeth. The laser wavelength was approximately 800nm, with pulsewidths of 95 and 150fs, and pulse repetition rates of 1kHz. The laser beam was focused to an approximate diameter of 50microm and was scanned over the tooth surface. The rise in the intrapulpal temperature was monitored by embedded thermocouples, and was shown to remain below 5 degrees C when the tooth was air-cooled during laser treatment. The surface preparation of the ablated teeth, observed by optical and electron microscopy, showed no apparent cracking or heat effects, and the hardness and Raman spectra of the laser-treated enamel were not distinguishable from those of native enamel. This study indicates the potential for ultra-short-pulsed lasers to effect precision ablation of dental enamel. PMID:14738125

  15. Ablation of crystalline oxides by infrared femtosecond laser pulses

    SciTech Connect

    Watanabe, Fumiya; Cahill, David G.; Gundrum, Bryan; Averback, R. S.

    2006-10-15

    We use focused laser pulses with duration of 180 fs and wavelength of 800 nm to study the interactions of high power near-infrared light with the surfaces of single-crystal transparent oxides (sapphire, LaAlO{sub 3}, SrTiO{sub 3}, yttria-stabilized ZrO{sub 2}, and MgO); the morphologies of the ablation craters are studied by atomic force microscopy and scanning electron microscopy. With the exception of LaAlO{sub 3}, the high temperature annealing of these oxide crystals produces atomically flat starting surfaces that enable studies of the morphology of ablation craters with subnanometer precision. The threshold fluence for ablation is determined directly from atomic-force microscopy images and increases approximately linearly with the band gap of the oxide. For all oxides except sapphire, the depth of the ablation crater increases approximately as the square root of the difference between the peak laser fluence and the threshold fluence for ablation. Sapphire shows unique behavior: (i) at laser fluences within 1 J/cm{sup 2} of the threshold for ablation, the depth of the ablation crater increases gradually instead of abruptly with laser fluence, and (ii) the rms roughness of the ablation crater shows a pronounced minimum of <0.2 nm at a laser fluence of 1 J/cm{sup 2} above the threshold.

  16. Magneto-absorption effects in magnetic-field assisted laser ablation of silicon by UV nanosecond pulses

    NASA Astrophysics Data System (ADS)

    Farrokhi, H.; Gruzdev, V.; Zheng, H. Y.; Rawat, R. S.; Zhou, W.

    2016-06-01

    A constant magnetic field can significantly improve the quality and speed of ablation by nanosecond laser pulses. These improvements are usually attributed to the confinement of laser-produced plasma by the magnetic field and specific propagation effects in the magnetized plasma. Here we report a strong influence of constant axial magnetic field on the ablation of silicon by 20-ns laser pulses at wavelength 355 nm, which results in an increase of ablation depth by a factor of 1.3 to 69 depending on laser parameters and magnitude of the magnetic field. The traditional plasma effects do not explain this result, and magneto-absorption of silicon is proposed as one of the major mechanisms of the significant enhancement of ablation.

  17. Effect of Laser Wavelength and Ablation Time on Pulsed Laser Ablation Synthesis of AL Nanoparticles in Ethanol

    NASA Astrophysics Data System (ADS)

    Baladi, A.; Mamoory, R. Sarraf

    Aluminum nanoparticles were synthesized by pulsed laser ablation of Al targets in ethanol for 5-15 minutes using the 1064 and 533 nm wavelengths of a Nd:YAG laser with energies of 280-320 mJ per pulse. It has been found that higher wavelength leads to significantly higher ablation efficiency, and finer spherical nanoparticles are also synthesized. Besides, it was obvious that higher ablation time resulted in higher ablated mass, while lower ablation rate was observed. Finer nanoparticles, moreover, are synthesized in higher ablation times.

  18. Fast pulse nonthermal plasma reactor

    DOEpatents

    Rosocha, Louis A.

    2005-06-14

    A fast pulsed nonthermal plasma reactor includes a discharge cell and a charging assembly electrically connected thereto. The charging assembly provides plural high voltage pulses to the discharge cell. Each pulse has a rise time between one and ten nanoseconds and a duration of three to twenty nanoseconds. The pulses create nonthermal plasma discharge within the discharge cell. Accordingly, the nonthermal plasma discharge can be used to remove pollutants from gases or break the gases into smaller molecules so that they can be more efficiently combusted.

  19. Heating and ablation of tokamak graphite by pulsed nanosecond Nd-YAG lasers

    SciTech Connect

    Semerok, A.; Fomichev, S. V.; Weulersse, J.-M.; Brygo, F.; Thro, P.-Y.; Grisolia, C.

    2007-04-15

    The results on laser heating and ablation of graphite tiles of thermonuclear tokamaks are presented. Two pulsed Nd-YAG lasers (20 Hz repetition rate, 5 ns pulse duration and 10 kHz repetition rate, 100 ns pulse duration) were applied for ablation measurements. The ablation thresholds (1.0{+-}0.5 J/cm{sup 2} for 5 ns and 2.5{+-}0.5 J/cm{sup 2} for 100 ns laser pulses) were determined for the Tore Supra tokamak graphite tiles (backside) nonexposed to plasma. The high repetition rate Nd-YAG laser (10 kHz, 100 ns pulse duration) and the developed pyrometer system were applied for graphite heating measurements. Some unexpected features of laser heating of the graphite surface were observed. They were explained by the presence of a thin surface layer with the properties different from those of the bulk graphite. The theoretical models of laser heating and near-threshold ablation of graphite with imperfectly adhered layer were developed to interpret the experimental results.

  20. Femtosecond pulsed laser ablation of GaAs

    NASA Astrophysics Data System (ADS)

    Trelenberg, T. W.; Dinh, L. N.; Saw, C. K.; Stuart, B. C.; Balooch, M.

    2004-01-01

    The properties of femtosecond-pulsed laser deposited GaAs nanoclusters were investigated. Nanoclusters of GaAs were produced by laser ablating a single crystal GaAs target in vacuum or in a buffer gas using a Ti-sapphire laser with a 150 fs minimum pulse length. For in-vacuum deposition, X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM) revealed that the average cluster size was approximately 7 nm for laser pulse lengths between 150 fs and 25 ps. The average cluster size dropped to approximately 1.5 nm at a pulse length of 500 ps. It was also observed that film thickness decreased with increasing laser pulse length. A reflective coating, which accumulated on the laser admission window during ablation, reduced the amount of laser energy reaching the target for subsequent laser shots and developed more rapidly at longer pulse lengths. This observation indicates that non-stoichiometric (metallic) ablatants were produced more readily at longer pulse lengths. The angular distribution of ejected material about the target normal was well fitted to a bi-cosine distribution of cos 47 θ+ cos 4 θ for ablation in vacuum using 150 fs pulses. XPS and AES revealed that the vacuum-deposited films contained excess amorphous Ga or As in addition to the stoichiometric GaAs nanocrystals seen with XRD. However, films containing only the GaAs nanocrystals were produced when ablation was carried out in the presence of a buffer gas with a pressure in excess of 6.67 Pa. At buffer gas pressure on the order of 1 Torr, it was found that the stoichiometry of the ablated target was also preserved. These experiments indicate that both laser pulse length and buffer gas pressure play important roles in the formation of multi-element nanocrystals by laser ablation. The effects of gas pressure on the target's morphology and the size of the GaAs nanocrystals formed will also be discussed.

  1. Non-contact acoustic tests based on nanosecond laser ablation: Generation of a pulse sound source with a small amplitude

    NASA Astrophysics Data System (ADS)

    Hosoya, Naoki; Kajiwara, Itsuro; Inoue, Tatsuo; Umenai, Koh

    2014-09-01

    A method to generate a pulse sound source for acoustic tests based on nanosecond laser ablation with a plasma plume is discussed. Irradiating a solid surface with a laser beam expands a high-temperature plasma plume composed of free electrons, ionized atoms, etc. at a high velocity throughout ambient air. The shockwave generated by the plasma plume becomes the pulse sound source. A laser ablation sound source has two features. Because laser ablation is induced when the laser fluence reaches 1012-1014 W/m2, which is less than that for laser-induced breakdown (1015 W/m2), laser ablation can generate a lower sound pressure, and the sound source has a hemispherical radiation pattern on the surface where laser ablation is generated. Additionally, another feature is that laser-induced breakdown sound sources can fluctuate, whereas laser ablation sound sources do not because laser ablation is produced at a laser beam-irradiation point. We validate this laser ablation method for acoustic tests by comparing the measured and theoretical resonant frequencies of an impedance tube.

  2. Nickel Nanoparticles Production using Pulsed Laser Ablation under Pressurized CO2

    NASA Astrophysics Data System (ADS)

    Mardis, Mardiansyah; Takada, Noriharu; Machmudah, Siti; Diono, Wahyu; Kanda, Hideki; Sasaki, Koichi; Goto, Motonobu

    2014-10-01

    We used nickel (Ni) plate as a target and irradiated pulse laser ablation with a fundamental wavelength of 1064 nm under pressurized CO2. The Ni plate was ablated at various pressure (5-15 MPa), temperature (15-80°), and irradiation time (3-30 min). The method successfully generated Ni nanoparticles in various shape and size. Generated Ni nanoparticles collected on a Si wafer and the ablated Ni plate were analyzed by Field Emission Scanning Electron Microscope (FE-SEM). With changing pressure and temperature, the structures of Ni nanoparticles also changed. The shape of generated particles is sphere-like structure with diameter around 10--100 nm. Also it was observed that a network structure of smaller particles was fabricated. The mechanism of nanoparticles fabrication could be explained as follows. Ablated nickel plate melted during the ablation process and larger particles formed, then ejected smaller spherical nanoparticles, which formed nanoclusters attached on the large particles. This morphology of particles was also observed for gold and silver nanoparticles with same condition. Further, the optical emission intensity from ablation plasma and the volume of the ablated crater were also examined under pressurized CO2.

  3. Contribution of material's surface layer on charge state distribution in laser ablation plasma.

    PubMed

    Kumaki, Masafumi; Steski, Dannie; Ikeda, Shunsuke; Kanesue, Takeshi; Okamura, Masahiro; Washio, Masakazu

    2016-02-01

    To generate laser ablation plasma, a pulse laser is focused onto a solid target making a crater on the surface. However, not all the evaporated material is efficiently converted to hot plasma. Some portion of the evaporated material could be turned to low temperature plasma or just vapor. To investigate the mechanism, we prepared an aluminum target coated by thin carbon layers. Then, we measured the ablation plasma properties with different carbon thicknesses on the aluminum plate. The results showed that C(6+) ions were generated only from the surface layer. The deep layers (over 250 nm from the surface) did not provide high charge state ions. On the other hand, low charge state ions were mainly produced by the deeper layers of the target. Atoms deeper than 1000 nm did not contribute to the ablation plasma formation. PMID:26931982

  4. Hydrodynamic simulation of ultrashort pulse laser ablation of gold film

    NASA Astrophysics Data System (ADS)

    Yu, Dong; Jiang, Lan; Wang, Feng; Shi, Xuesong; Qu, Liangti; Lu, Yongfeng

    2015-06-01

    The electron collision frequency in a hydrodynamic model was improved to match the laser energy absorbed with experimental data. The model calculation was used to investigate the ablation depth and the dependence of the threshold fluence of gold film on pulse width and wavelength. Two methods for estimating the ablation depth are introduced here with their respective scope of application. The dependence of the threshold fluence of gold film on the pulse width of the laser with a 1053 nm center wavelength agreed well with the experimental data. It was also observed that for pulses shorter than ~200 ps, the threshold fluence showed linear dependence on the logarithm of pulse width and increased with the wavelength, which was different from previous results.

  5. Hydrogen alpha laser ablation plasma diagnostics.

    PubMed

    Parigger, C G; Surmick, D M; Gautam, G; El Sherbini, A M

    2015-08-01

    Spectral measurements of the H(α) Balmer series line and the continuum radiation are applied to draw inferences of electron density, temperature, and the level of self-absorption in laser ablation of a solid ice target in ambient air. Electron densities of 17 to 3.2×10(24) m(-3) are determined from absolute calibrated emission coefficients for time delays of 100-650 ns after generation of laser plasma using Q-switched Nd:YAG radiation. The corresponding temperatures of 4.5-0.95 eV were evaluated from the absolute spectral radiance of the continuum at the longer wavelengths. The redshifted, Stark-broadened hydrogen alpha line emerges from the continuum radiation after a time delay of 300 ns. The electron densities inferred from power law formulas agree with the values obtained from the plasma emission coefficients. PMID:26258326

  6. Pulsed laser ablation of pepsin on an inorganic substrate

    NASA Astrophysics Data System (ADS)

    Cicco, N.; Lopizzo, T.; Marotta, V.; Morone, A.; Verrastro, M.; Viggiano, V.

    2009-03-01

    Pressed pepsin pellets used as targets were ablated with the pulses of the Nd-YAG laser. The activity of the pepsin thin layer, deposited on a glass substrate, was successfully detected by analyzing the proteolytic degradation areas on the polyacrylamide gel (PA-gel) copolymerized with albumin from the hen egg white (ovalbumin), used as an enzymatic substrate.

  7. Laser ablation plasma-assisted stabilization of premixed methane/air flame

    NASA Astrophysics Data System (ADS)

    Li, Xiaohui; Yu, Yang; Peng, Jiangbo; Yu, Xin; Fan, Rongwei; Sun, Rui; Chen, Deying

    2016-01-01

    Laser ablation plasma has been applied to assist stabilization of premixed methane/air flames with a flow speed up to 15.3 m/s. The ablation plasma was generated using the 50 Hz, 1064 nm output of a Nd:YAG laser onto a tantalum slab. With the ablation plasma, the stabilization equivalence ratio has been extended to the fuel-leaner end and the blow off limits have been enhanced by from 3.6- to 14.8-folds for flames which can stabilize without the plasma. The laser pulse energy required for flameholding was reduced to 10 mJ, a 64 % reduction compared with that of gas breakdown plasma, which will ease the demand for high-power lasers for high-frequency plasma generation. The temporal evolutions of the flame kernels following the ablation plasma were investigated using the OH* chemiluminescence imaging approach, and the flame propagation speed ( v f) was measured from the flame kernel evolutions. With the ablation plasma, the v f with flow speed of 4.7-9.0 m/s and equivalence ratio of 1.4 has been enhanced from 0.175 m/s of laminar premixed methane/air flame to 2.79-4.52 and 1.59-5.46 m/s, respectively, in the early and late time following the ablation plasma. The increase in the combustion radical concentrations by the ablation plasma was thought to be responsible for the v f enhancement and the resulted flame stabilization.

  8. High-speed photographic studies of dye-assisted pulsed Nd:YAG laser ablation of dental hard tissues

    NASA Astrophysics Data System (ADS)

    Lu, Quiang; Wallace, David B.; Hayes, Donald J.

    1997-06-01

    We have been evaluating the use of a pulsed Nd:YAG laser for ablating hard dental tissue. For this application we apply dye-drops of an IR absorptive fluid on the enamel, then irradiate with a laser pulse from the laser. By using ink- jet technology to deliver the dye-drops, we can attain micron- and millisecond-scale precision in drop delivery, with a 'burst' of drops preceding each laser pulse. To gain better understanding of the ablation process we have used a high- speed CCD camera system with 1 microsecond(s) exposure and 1 microsecond(s) inter-exposure-interval capability. Fast photography of the ablation process showed the following typical events. (i) The laser induced plasma plume erupts immediately after pulse onset, expands to maximum within 50 microsecond(s) , and lasts up to 200 microsecond(s) . (ii) Ejected particles flying away from the site of laser pulse/dye-drop impact are detected within 30 microsecond(s) of laser pulse onset, and continue up to 10 ms. These particles attain velocities up to 50 m/s with lower velocities from lower pulse power. (iii) The plasma plume has a peak height that increases with increasing laser fluence, ranging up to 10 mm for a fluence of 242 J/cm2 on enamel. From this study, the dye-assisted ablation mechanisms are inferred to be plasma-mediated and explosion- mediated tissue removal.

  9. Ablation of carbon-doped liquid propellant in laser plasma propulsion

    NASA Astrophysics Data System (ADS)

    Zheng, Z. Y.; Liang, T.; Zhang, S. Q.; Gao, L.; Gao, H.; Zhang, Z. L.

    2016-04-01

    Carbon-doped liquid glycerol ablated by nanosecond pulse laser is investigated in laser plasma propulsion. It is found that the propulsion is much more correlated with the carbon content. The doped carbon can change the laser intensity and laser focal position so as to reduce the splashing quantity of the glycerol. Less consumption of the liquid volume results in a high specific impulse.

  10. Cluster Generation Under Pulsed Laser Ablation Of Compound Semiconductors

    SciTech Connect

    Bulgakov, Alexander V.; Evtushenko, Anton B.; Shukhov, Yuri G.; Ozerov, Igor; Marine, Wladimir

    2010-10-08

    A comparative experimental study of pulsed laser ablation in vacuum of two binary semiconductors, zinc oxide and indium phosphide, has been performed using IR- and visible laser pulses with particular attention to cluster generation. Neutral and cationic Zn{sub n}O{sub m} and In{sub n}P{sub m} particles of various stoichiometry have been produced and investigated by time-of-flight mass spectrometry. At ZnO ablation, large cationic (n>9) and all neutral clusters are mainly stoichiometric in the ablation plume. In contrast, indium phosphide clusters are strongly indium-rich with In{sub 4}P being a magic cluster. Analysis of the plume composition upon laser exposure has revealed congruent vaporization of ZnO and a disproportionate loss of phosphorus by the irradiated InP surface. Plume expansion conditions under ZnO ablation are shown to be favorable for stoichiometric cluster formation. A delayed vaporization of phosphorus under InP ablation has been observed that results in generation of off-stoichiometric clusters.

  11. Fundamental Mechanisms of Pulsed Laser Ablation of Biological Tissue

    NASA Astrophysics Data System (ADS)

    Albagli, Douglas

    The ability to cut and remove biological tissue with short pulsed laser light, a process called laser ablation, has the potential to revolutionize many surgical procedures. Ablation procedures using short pulsed lasers are currently being developed or used in many fields of medicine, including cardiology, ophthalmology, dermatology, dentistry, orthopedics, and urology. Despite this, the underlying physics of the ablation process is not well understood. In fact, there is wide disagreement over whether the fundamental mechanism is primarily photothermal, photomechanical, or photochemical. In this thesis, both experimental and theoretical techniques are developed to explore this issue. The photothermal model postulates that ablation proceeds through vaporization of the target material. The photomechanical model asserts that ablation is initiated when the laser-induced tensile stress exceeds the ultimate tensile strength of the target. I have developed a three dimensional model of the thermoelastic response of tissue to short pulsed laser irradiation which allows the time dependent stress distribution to be calculated given the optical, thermal and mechanical properties of the target. A complimentary experimental technique has been developed to verify this model, measure the needed physical properties of the tissue, and record the thermoelastic response of the tissue at the onset of ablation. The results of this work have been widely disseminated to the international research community and have led to significant findings which support the photomechanical model of ablation of tissue. First, the energy deposited in tissue is an order of magnitude less than that required for vaporization. Second, unlike the one-dimensional thermoelastic model of laser-induced stress generation that has appeared in the literature, the full three-dimensional model predicts the development of significant tensile stresses on the surface of the target, precisely where ablation is observed to

  12. Laser Ablation Inductively Coupled Plasma Mass Spectrometry

    PubMed Central

    Hutchinson, Robert W.; McLachlin, Katherine M.; Riquelme, Paloma; Haarer, Jan; Broichhausen, Christiane; Ritter, Uwe; Geissler, Edward K.; Hutchinson, James A.

    2015-01-01

    ABSTRACT New analytical techniques for multiparametric characterisation of individual cells are likely to reveal important information about the heterogeneity of immunological responses at the single-cell level. In this proof-of-principle study, laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was applied to the problem of concurrently detecting 24 lineage and activation markers expressed by human leucocytes. This approach was sufficiently sensitive and specific to identify subpopulations of isolated T, B, and natural killer cells. Leucocyte subsets were also accurately detected within unfractionated peripheral blood mononuclear cells preparations. Accordingly, we judge LA-ICP-MS to be a suitable method for assessing expression of multiple tissue antigens in solid-phase biological specimens, such as tissue sections, cytospins, or cells grown on slides. These results augur well for future development of LA-ICP-MS–based bioimaging instruments for general users. PMID:27500232

  13. Note: Low density and long plasma channels generated by laser transversely ignited ablative capillary discharges.

    PubMed

    Liu, Mingwei; Deng, Aihua; Liu, Jiansheng; Li, Ruxin; Xu, Jiancai; Xia, Changquan; Wang, Cheng; Shen, Baifei; Xu, Zhizhan; Nakajima, K

    2010-03-01

    A technique is developed to reduce the jitter associated with ablative capillary discharges. A laser pulse propagating perpendicularly to the axis of the capillary and focused onto a copper wire creates a plasma that initiates the discharge. This transverse laser ignition method has several advantages over previous techniques employing a laser pulse collinear with the capillary, including increased capillary lifetime and simpler arrangement of the igniting and the driving pulses for laser-wakefield acceleration. Using this technique long, low density plasma channels are produced with low jitter. PMID:20370230

  14. Absorption of a single 500 fs laser pulse at the surface of fused silica: Energy balance and ablation efficiency

    SciTech Connect

    Varkentina, N.; Sanner, N.; Lebugle, M.; Sentis, M.; Utéza, O.

    2013-11-07

    Ablation of fused silica by a single femtosecond laser pulse of 500 fs pulse duration is investigated from the perspective of efficiency of incident photons to remove matter. We measure the reflected and transmitted fractions of the incident pulse energy as a function of fluence, allowing us to recover the evolution of absorption at the material surface. At the ablation threshold fluence, 25% of incident energy is absorbed. At high fluences, this ratio saturates around 70% due to the appearance of a self-triggered plasma mirror (or shielding) effect. By using the energy balance retrieved experimentally and measurements of the ablated volume, we show that the amount of absorbed energy is far above the bonding energy of fused silica at rest and also above the energy barrier to ablate the material under non-equilibrium thermodynamic conditions. Our results emphasize the crucial role of transient plasma properties during the laser pulse and suggest that the major part of the absorbed energy has been used to heat the plasma formed at the surface of the material. A fluence range yielding an efficient and high quality ablation is also defined, which makes the results relevant for femtosecond micromachining processes.

  15. Investigation and spectral analysis of the plasma-induced ablation mechanism of dental hydroxyapatite

    NASA Astrophysics Data System (ADS)

    Niemz, M. H.

    1994-04-01

    Experiments on the ablation of dental substance performed with picosecond laser pulses are reported for the first time. A mode locked Nd:YLF oscillator laser was used to generate 25 ps pulses at a wavelength of 1.053 µm. These were seeded and amplified to pulse energies up to 1 mJ in a regenerative amplifier laser at repetition rates up to 1 kHz. Very precise cavities were ablated in the enamel of extracted human teeth by mounting the probes onto a computer controlled 3D translation stage. Scanning electron microscopy and dye penetration tests were performed there-after. In contrast to longer pulse durations, picosecond pulses ablate with no signs of thermal damage, if the laser pulses are spatially distributed over the target. Definitions of the physical mechanisms “plasma-induced ablation” and “photodisruption” are given. Furthermore, the generated plasma spark has been spectroscopically analyzed. Excitations of calcium and sodium have been observed. From the spectra, the plasma temperature and free electron density could be estimated. By converting part of the laser energy into the second harmonic using a LiNbO3 crystal, a reference amplitude was achieved for the spectra. With this reference signal, a clear distinction could be made between spectra obtained from healthy and caries infected teeth, thus enabling a better control of caries removal in the near future.

  16. Filamentation due to the Weibel Instability in two counterstreaming laser ablated plasmas

    NASA Astrophysics Data System (ADS)

    Dong, Quan-Li; Yuan, Dawei; Gao, Lan; Liu, Xun; Chen, Yangao; Jia, Qing; Hua, Neng; Qiao, Zhanfeng; Chen, Ming; Zhu, Baoqiang; Zhu, Jianqiang; Zhao, Gang; Ji, Hantao; Sheng, Zheng-Ming; Zhang, Jie

    2016-05-01

    Weibel-type filamentation instability was observed in the interaction of two counter streaming laser ablated plasma flows, which were supersonic, collisionless, and closely relevant to astrophysical conditions. The plasma flows were created by irradiating a pair of oppositely standing plastic (CH) foils with 1ns-pulsed laser beams of total energy of 1.7 kJ in two laser spots. With characteristics diagnosed in experiments, the calculated features of Weibel-type filaments are in good agreement with measurements.

  17. Micro-ablation with high power pulsed copper vapor lasers.

    PubMed

    Knowles, M

    2000-07-17

    Visible and UV lasers with nanosecond pulse durations, diffraction-limited beam quality and high pulse repetition rates have demonstrated micro-ablation in a wide variety of materials with sub-micron precision and sub-micron-sized heat-affected zones. The copper vapour laser (CVL) is one of the important industrial lasers for micro-ablation applications. Manufacturing applications for the CVL include orifice drilling in fuel injection components and inkjet printers, micro-milling of micromoulds, via hole drilling in printed circuit boards and silicon machining. Recent advances in higher power (100W visible, 5W UV), diffraction-limited, compact CVLs are opening new possibilities for manufacturing with this class of nanosecond laser. PMID:19404369

  18. Growth of epitaxial thin films by pulsed laser ablation

    SciTech Connect

    Lowndes, D.H.

    1992-01-01

    High-quality, high-temperature superconductor (HTSc) films can be grown by the pulsed laser ablation (PLA) process. This article provides a detailed introduction to the advantages and curent limitations of PLA for epitaxial film growth. Emphasis is placed on experimental methods and on exploitation of PLA to control epitaxial growth at either the unit cell or the atomic-layer level. Examples are taken from recent HTSc film growth. 33 figs, 127 refs. (DLC)

  19. Growth of epitaxial thin films by pulsed laser ablation

    SciTech Connect

    Lowndes, D.H.

    1992-10-01

    High-quality, high-temperature superconductor (HTSc) films can be grown by the pulsed laser ablation (PLA) process. This article provides a detailed introduction to the advantages and curent limitations of PLA for epitaxial film growth. Emphasis is placed on experimental methods and on exploitation of PLA to control epitaxial growth at either the unit cell or the atomic-layer level. Examples are taken from recent HTSc film growth. 33 figs, 127 refs. (DLC)

  20. Pulsed welding plasma source

    NASA Astrophysics Data System (ADS)

    Knyaz'kov, A.; Pustovykh, O.; Verevkin, A.; Terekhin, V.; Shachek, A.; Tyasto, A.

    2016-04-01

    It is shown that in order to form the current pulse of a near rectangular shape, which provides conversion of the welding arc into a dynamic mode, it is rational to connect a forming element made on the basis of an artificial forming line in series to the welding DC circuit. The paper presents a diagram of a pulsed device for welding with a non-consumable electrode in argon which was developed using the forming element. The conversion of the arc into the dynamic mode is illustrated by the current and voltage oscillograms of the arc gap and the dynamic characteristic of the arc within the interval of one pulse generation time in the arc gap. The background current travels in the interpulse interval.

  1. The absorption and radiation of a tungsten plasma plume during nanosecond laser ablation

    SciTech Connect

    Moscicki, T. Hoffman, J.; Chrzanowska, J.

    2015-10-15

    In this paper, the effect of absorption of the laser beam and subsequent radiation on the dynamics of a tungsten plasma plume during pulsed laser ablation is analyzed. Different laser wavelengths are taken into consideration. The absorption and emission coefficients of tungsten plasma in a pressure range of 0.1–100 MPa and temperature up to 70 000 K are presented. The shielding effects due to the absorption and radiation of plasma may have an impact on the course of ablation. The numerical model that describes the tungsten target heating and the formation of the plasma and its expansion were made for 355 nm and 1064 nm wavelengths of a Nd:YAG laser. The laser beam with a Gaussian profile was focused to a spot size of 0.055 mm{sup 2} with a power density of 1 × 10{sup 9 }W/cm{sup 2} (10 ns full width half maximum pulse duration). The plasma expands into air at ambient pressure of 1 mPa. The use of the shorter wavelength causes faster heating of the target, thus the higher ablation rate. The consequences of a higher ablation rate are slower expansion and smaller dimensions of the plasma plume. The higher plasma temperature in the case of 1064 nm is due to the lower density and lower plasma radiation. In the initial phase of propagation of the plasma plume, when both the temperature and pressure are very high, the dominant radiation is emission due to photo-recombination. However, for a 1064 nm laser wavelength after 100 ns of plasma expansion, the radiation of the spectral lines is up to 46.5% of the total plasma radiation and should not be neglected.

  2. Experimental study on double-pulse laser ablation of steel upon multiple parallel-polarized ultrashort-pulse irradiations

    NASA Astrophysics Data System (ADS)

    Schille, Joerg; Schneider, Lutz; Kraft, Sebastian; Hartwig, Lars; Loeschner, Udo

    2016-07-01

    In this paper, double-pulse laser processing is experimentally studied with the aim to explore the influence of ultrashort pulses with very short time intervals on ablation efficiency and quality. For this, sequences of 50 double pulses of varied energy and inter-pulse delay, as adjusted between 400 fs and 18 ns by splitting the laser beam into two optical paths of different length, were irradiated to technical-grade stainless steel. The depth and the volume of the craters produced were measured in order to evaluate the efficiency of the ablation process; the crater quality was analyzed by SEM micrographs. The results obtained were compared with craters produced with sequences of 50 single pulses and energies equal to the double pulse. It is demonstrated that double-pulse processing cannot exceed the ablation efficiency of single pulses of optimal fluence, but the ablation crater surface formed smoother if inter-pulse delay was in the range between 10 ns and 18 ns. In addition, the influence of pulse duration and energy distribution between the individual pulses of the double pulse on ablation was studied. For very short inter-pulse delay, no significant effect of energy variation within the double pulse on removal rate was found, indicating that the double pulse acts as a big single pulse of equal energy. Further, the higher removal efficiency was achieved when double-pulse processing using femtosecond pulses instead of picosecond pulses.

  3. Optical Emission Spectroscopy of the Laser Ablation Plume Controled by RF Plasma

    NASA Astrophysics Data System (ADS)

    Suda, Yoshiyuki; Nishimura, Takuma; Mizuno, Manabu; Bratescu, Maria Antoaneta; Sakai, Yosuke

    1999-10-01

    Recently, film deposition has been investigated using laser ablation methods which have a lot of advantages. For the purpose of control of the laser ablation plume, we introduced a radio frequency (RF) plasma. In this report we present position resolved optical emission spectra of the plume observed by an OMA (optical multichannel analyzer). The plume current is also measured. The RF plasma is generated in a helical coil installed between the substrate and the target. An ArF excimer laser (wavelength 193 nm, pulse duration time 20 ns) is used as a light source, and the target material is sintered carbon graphite. The laser fluence on the target surface is changed in a range from 1.2 to 6.4 J/cm^2. Ar gas is introduced to sustain the RF plasma. When the plume goes through the RF plasma, interaction of the plume with the plasma is expected. The possibility of control of the plume behavior is discussed.

  4. Microwave ablation energy delivery: Influence of power pulsing on ablation results in an ex vivo and in vivo liver model

    PubMed Central

    Bedoya, Mariajose; del Rio, Alejandro Muñoz; Chiang, Jason; Brace, Christopher L.

    2014-01-01

    Purpose: The purpose of this study was to compare the impact of continuous and pulsed energy deliveries on microwave ablation growth and shape in unperfused and perfused liver models. Methods: A total of 15 kJ at 2.45 GHz was applied to ex vivo bovine liver using one of five delivery methods (n = 50 total, 10 per group): 25 W continuous for 10 min (25 W average), 50 W continuous for 5 min (50 W average), 100 W continuous for 2.5 min (100 W average), 100 W pulsed for 10 min (25 W average), and 100 W pulsed for 5 min (50 W average). A total of 30 kJ was applied to in vivo porcine livers (n = 35, 7 per group) using delivery methods similar to the ex vivo study, but with twice the total ablation time to offset heat loss to blood perfusion. Temperatures were monitored 5–20 mm from the ablation antenna, with values over 60 °C indicating acute cellular necrosis. Comparisons of ablation size and shape were made between experimental groups based on total energy delivery, average power applied, and peak power using ANOVA with post-hoc pairwise tests. Results: No significant differences were noted in ablation sizes or circularities between pulsed and continuous groups in ex vivo tissue. Temperature data demonstrated more rapid heating in pulsed ablations, suggesting that pulsing may overcome blood perfusion and coagulate tissues more rapidly in vivo. Differences in ablation size and shape were noted in vivo despite equivalent energy delivery among all groups. Overall, the largest ablation volume in vivo was produced with 100 W continuous for 5 min (265.7 ± 208.1 cm3). At 25 W average, pulsed-power ablation volumes were larger than continuous-power ablations (67.4 ± 34.5 cm3 versus 23.6 ± 26.5 cm3, P = 0.43). Similarly, pulsed ablations produced significantly greater length (P ≤ 0.01), with increase in diameter (P = 0.09) and a slight decrease in circularity (P = 0.97). When comparing 50 W average power groups, moderate differences in size were noted (P ≥ 0.06) and

  5. Adjustment of ablation shapes and subwavelength ripples based on electron dynamics control by designing femtosecond laser pulse trains

    SciTech Connect

    Yuan Yanping; Jiang Lan; Li Xin; Wang Cong

    2012-11-15

    A quantum model is proposed to investigate femtosecond laser pulse trains processing of dielectrics by including the plasma model with the consideration of laser particle-wave duality. Central wavelengths (400 nm and 800 nm) strongly impact the surface plasmon field distribution, the coupling field intensity distribution (between the absorbed intensity and the surface plasma), and the distribution of transient localized free electron density in the material. This, in turn, significantly changes the localized transient optical/thermal properties during laser materials processing. The effects of central wavelengths on ablation shapes and subwavelength ripples are discussed. The simulation results show that: (1) ablation shapes and the spacing of subwavelength ripples can be adjusted by localized transient electron dynamics control using femtosecond laser pulse trains; (2) the adjustment of the radii of ablation shapes is stronger than that of the periods of subwavelength ripples.

  6. Femtosecond pulsed laser ablation to enhance drug delivery across the skin.

    PubMed

    Garvie-Cook, Hazel; Stone, James M; Yu, Fei; Guy, Richard H; Gordeev, Sergey N

    2016-01-01

    Laser poration of the skin locally removes its outermost, barrier layer, and thereby provides a route for the diffusion of topically applied drugs. Ideally, no thermal damage would surround the pores created in the skin, as tissue coagulation would be expected to limit drug diffusion. Here, a femtosecond pulsed fiber laser is used to porate mammalian skin ex vivo. This first application of a hollow core negative curvature fiber (HC-NCF) to convey a femtosecond pulsed, visible laser beam results in reproducible skin poration. The effect of applying ink to the skin surface, prior to ultra-short pulsed ablation, has been examined and Raman spectroscopy reveals that the least, collateral thermal damage occurs in inked skin. Pre-application of ink reduces the laser power threshold for poration, an effect attributed to the initiation of plasma formation by thermionic electron emission from the dye in the ink. Poration under these conditions significantly increases the percutaneous permeation of caffeine in vitro. Dye-enhanced, plasma-mediated ablation of the skin is therefore a potentially advantageous approach to enhance topical/transdermal drug absorption. The combination of a fiber laser and a HC-NCF, capable of emitting and delivering femtosecond pulsed, visible light, may permit a compact poration device to be developed. PMID:26449289

  7. In Situ Characterization of Laser Ablation by Pulsed Photoacoustics: The Case of Organic Nanocrystal Synthesis

    NASA Astrophysics Data System (ADS)

    Alba-Rosales, J. E.; Ramos-Ortiz, G.; Rodríguez, M.; Polo-Parada, L.; Gutiérrez-Juárez, G.

    2013-09-01

    Here, a new methodology based on the pulsed photoacoustic (PA) technique for real-time monitoring of the ablation process used to synthesize organic nanocrystals is described. The methodology is implemented by ablating microcrystals grown from an organic chromophore with nonlinear optical properties. It was determined that the PA signal from the ablation process increases in amplitude and is time-shifted as the ablation process advances. Comparing the PA signals generated at different ablation times under different laser fluences with the nanocrystal characterization obtained through light scattering, optical microscopy, and AFM, it was demonstrated that the pulsed PA technique can be useful for monitoring the process and determining the threshold of ablation.

  8. Critical Fluences And Modeling Of CO{sub 2} Laser Ablation Of Polyoxymethylene From Vaporization To The Plasma Regime

    SciTech Connect

    Sinko, John E.; Phipps, Claude R.; Tsukiyama, Yosuke; Ogita, Naoya; Sasoh, Akihiro; Umehara, Noritsugu; Gregory, Don A.

    2010-05-06

    A CO{sub 2} laser was operated at pulse energies up to 10 J to ablate polyoxymethylene targets in air and vacuum conditions. Critical effects predicted by ablation models are discussed in relation to the experimental data, including specifically the threshold fluences for vaporization and critical plasma formation, and the fluence at which the optimal momentum coupling coefficient is found. Finally, we discuss a new approach for modeling polymers at long wavelengths, including a connection formula that links the vaporization and plasma regimes for laser ablation propulsion.

  9. Nanosecond laser ablation for pulsed laser deposition of yttria

    NASA Astrophysics Data System (ADS)

    Sinha, Sucharita

    2013-09-01

    A thermal model to describe high-power nanosecond pulsed laser ablation of yttria (Y2O3) has been developed. This model simulates ablation of material occurring primarily through vaporization and also accounts for attenuation of the incident laser beam in the evolving vapor plume. Theoretical estimates of process features such as time evolution of target temperature distribution, melt depth and ablation rate and their dependence on laser parameters particularly for laser fluences in the range of 6 to 30 J/cm2 are investigated. Calculated maximum surface temperatures when compared with the estimated critical temperature for yttria indicate absence of explosive boiling at typical laser fluxes of 10 to 30 J/cm2. Material ejection in large fragments associated with explosive boiling of the target needs to be avoided when depositing thin films via the pulsed laser deposition (PLD) technique as it leads to coatings with high residual porosity and poor compaction restricting the protective quality of such corrosion-resistant yttria coatings. Our model calculations facilitate proper selection of laser parameters to be employed for deposition of PLD yttria corrosion-resistive coatings. Such coatings have been found to be highly effective in handling and containment of liquid uranium.

  10. Electronegative Plasma Instabilities in Pulsed Plasmas

    NASA Astrophysics Data System (ADS)

    Pribyl, Patrick; Gekelman, Walter

    2015-09-01

    Modern inductively coupled plasma reactors can all be operated in unstable configurations, although in many cases normal precautions result in quiescent stable operation. However, electronegative gases that are important for etch processes have a series of instabilities that occur at process relevant conditions. These have been studied since the 1990s, but are becoming a much more important today as plasma reactors are being pushed to produce ever finer features, and tight control of the etch process is becoming crucial. A device at UCLA was designed to simulate industrial reactors used in semiconductor processing. Various gas mixtures are programmable (Ar, SF6, O2). ICP coils in different configurations are driven by pulsed RF generators operating separately from 400 kHz to 40 MHz. A stainless steel ``chuck'' assembly can be positioned at a variable height, either with a wafer and RF bias, or with direct DC bias to directly program sheath voltage. A computer controlled automated probe drive can access the entire volume above the substrate. The probe can be a Langmuir probe, a ``Bdot'' probe, or an emissive probe the latter used for more accurate determination of plasma potential. A microwave interferometer is available to measure line-averaged electron density. Optical emission can be diagnosed using a half or 1 meter spectrometer. We describe work with electronegative gases to characterize and potentially stabilize the plasma against ionization instabilities using pulsed plasmas. Work supported by NSF and done at the Basic Plasma Science Facility.

  11. Comparison of soft and hard tissue ablation with sub-ps and ns pulse lasers

    SciTech Connect

    Da Silva, L.B.; Stuart, B.C.; Celliers, P.M.; Feit, M.D.; Glinsky, M.E.; Heredia, N.J.; Herman, S.; Lane, S.M.; London, R.A.; Matthews, D.L.; Perry, M.D.; Rubenchik, A.M.; Chang, T.D.; Neev, J.

    1996-05-01

    Tissue ablation with ultrashort laser pulses offers several unique advantages. The nonlinear energy deposition is insensitive to tissue type, allowing this tool to be used for soft and hard tissue ablation. The localized energy deposition lead to precise ablation depth and minimal collateral damage. This paper reports on efforts to study and demonstrate tissue ablation using an ultrashort pulse laser. Ablation efficiency and extent of collateral damage for 0.3 ps and 1000 ps duration laser pulses are compared. Temperature measurements of the rear surface of a tooth section is also presented.

  12. Pulsed Electromagnetic Acceleration of Plasmas

    NASA Technical Reports Server (NTRS)

    Thio, Y. C. Francis; Cassibry, Jason T.; Markusic, Tom E.; Rodgers, Stephen L. (Technical Monitor)

    2002-01-01

    A major shift in paradigm in driving pulsed plasma thruster is necessary if the original goal of accelerating a plasma sheet efficiently to high velocities as a plasma "slug" is to be realized. Firstly, the plasma interior needs to be highly collisional so that it can be dammed by the plasma edge layer not (upstream) adjacent to the driving 'vacuum' magnetic field. Secondly, the plasma edge layer needs to be strongly magnetized so that its Hall parameter is of the order of unity in this region to ensure excellent coupling of the Lorentz force to the plasma. Thirdly, to prevent and/or suppress the occurrence of secondary arcs or restrike behind the plasma, the region behind the plasma needs to be collisionless and extremely magnetized with sufficiently large Hall parameter. This places a vacuum requirement on the bore conditions prior to the shot. These requirements are quantified in the paper and lead to the introduction of three new design parameters corresponding to these three plasma requirements. The first parameter, labeled in the paper as gamma (sub 1), pertains to the permissible ratio of the diffusive excursion of the plasma during the course of the acceleration to the plasma longitudinal dimension. The second parameter is the required Hall parameter of the edge plasma region, and the third parameter the required Hall parameter of the region behind the plasma. Experimental research is required to quantify the values of these design parameters. Based upon fundamental theory of the transport processes in plasma, some theoretical guidance on the choice of these parameters are provided to help designing the necessary experiments to acquire these data.

  13. Pulsed CO2 laser ablation of graphite and polymers

    NASA Astrophysics Data System (ADS)

    Wong, K. H.; Tou, T. Y.; Low, K. S.

    1998-02-01

    Spectroscopic analysis of the emission plumes of graphite, polyimide, polyethylene terepthalate, and polymethylmethacrylate that have been ablated by using a pulsed CO2 laser operating at 10.6 μm shows the presence of CN and C2, species not previously reported for CO2 laser ablation. The gross dynamics of the luminous plume, which was studied by using a streak camera, compares favorably with predictions from the snowplow model, which also accurately forecasts the time history of the plume expansion for a wide range of background gas pressures and laser fluences. Framing shadowgraphy reveals the onset of laser-supported detonation waves at approximately 50 mbar Ar, thus somewhat limiting the validity of this model.

  14. Coupling effects of the number of pulses, pulse repetition rate and fluence during laser PMMA ablation

    NASA Astrophysics Data System (ADS)

    Liu, Z. Q.; Feng, Y.; Yi, X.-S.

    2000-10-01

    Poly(methyl methacrylate) (PMMA) was ablated using a 248-nm long-pulsed KrF excimer laser operating at a pulse repetition rate (PRR) of 2 and 10 Hz, and fluence varying from 0.4 to 2 J/cm 2. The coupling effects of multiple shots, PRR, and fluence are found and discussed on the etching depth data and topography of PMMA. An increase in either PRR, or fluence or the number of pulses can accelerate the etching efficiency in terms of ablation rate, as a result of strengthened thermal effects. Quality of the craters such as roughness, porosity and contamination is sensitively dependent on the specific laser operating conditions. Basically, increasing the PRR and the number of pulses gives rise to a crater with smoother and less porous bottom.

  15. Ablation of hard dental tissues with an ArF-pulsed excimer laser

    NASA Astrophysics Data System (ADS)

    Neev, Joseph; Raney, Daniel; Whalen, William E.; Fujishige, Jack T.; Ho, Peter D.; McGrann, John V.; Berns, Michael W.

    1991-06-01

    The interaction of 15 ns pulses from an ArF excimer laser with hard dental tissue was investigated for the purpose of obtaining practical information on the ablation process. Dark field fast photography utilizing an auxiliary, 15 ns Nd:Yag laser 'probe', was used to study the ablation plume dynamics as a function of time, luminescence were studied at different fluence levels and prr. Dentin ablation was found to be about four times as efficient as ablation of enamel in the higher fluence levels tested (> 10 J/cm2) and about twice as efficient as the ablation in the lower fluence regime (approximately equals 1 J/cm2). The dentin etch depth per pulse was found to increase exponentially with fluence (at least up to the tested level of 11 J/cm2), while in enamel the etch depth per pulse appears to increase logarithmically with fluence. Dentin ablation yields a larger, more dense plume which can be ejected (depending on the fluence level) to a height of several millimeters above the surface with observed ejection velocity in access of 1200 m/s. The dentin plume consisted of a relatively uniform particle size distribution (0.1 micrometers to 10 micrometers in diameter). Enamel ablation, on the other hand, yields a smaller observed ejection velocities (about 800 m/s), and a much smaller plume of fine particles (about 0.1 micrometers in diameter) and gases, confined to within 0.5 mm of the surface. In addition, an even smaller amount of highly non-uniform debris, (from ten to several hundred micrometers in size) is observed to be ejected to higher levels, and reach roughly half the height of the corresponding dentin plume for similar fluence levels. Although both dentin and enamel yield lower ablation efficiencies at 1 Hz, no significant difference is detected between the ablation efficiency at 5 Hz and ablation 10 Hz prr. Both materials remained within 20 degree(s)C of room temperature even at fluences as high as 20 J/cm2 and prr as high as 10 Hz for enamel and 20 Hz for

  16. Ultrarelativistic electromagnetic pulses in plasmas

    NASA Technical Reports Server (NTRS)

    Ashour-Abdalla, M.; Leboeuf, J. N.; Tajima, T.; Dawson, J. M.; Kennel, C. F.

    1981-01-01

    The physical processes of a linearly polarized electromagnetic pulse of highly relativistic amplitude in an underdense plasma accelerating particles to very high energies are studied through computer simulation. An electron-positron plasma is considered first. The maximum momenta achieved scale as the square of the wave amplitude. This acceleration stops when the bulk of the wave energy is converted to particle energy. The pulse leaves behind as a wake a vacuum region whose length scales as the amplitude of the wave. The results can be explained in terms of a snow plow or piston-like action of the radiation on the plasma. When a mass ratio other than unity is chosen and electrostatic effects begin to play a role, first the ion energy increases faster than the electron energy and then the electron energy catches up later, eventually reaching the same value.

  17. Aerospace applications of pulsed plasmas

    NASA Astrophysics Data System (ADS)

    Starikovskiy, Andrey

    2012-10-01

    The use of a thermal equilibrium plasma for combustion control dates back more than a hundred years to the advent of internal combustion (IC) engines and spark ignition systems. The same principles are still applied today to achieve high efficiency in various applications. Recently, the potential use of nonequilibrium plasma for ignition and combustion control has garnered increasing interest due to the possibility of plasma-assisted approaches for ignition and flame stabilization. During the past decade, significant progress has been made toward understanding the mechanisms of plasma chemistry interactions, energy redistribution and the nonequilibrium initiation of combustion. In addition, a wide variety of fuels have been examined using various types of discharge plasmas. Plasma application has been shown to provide additional combustion control, which is necessary for ultra-lean flames, high-speed flows, cold low-pressure conditions of high-altitude gas turbine engine (GTE) relight, detonation initiation in pulsed detonation engines (PDE) and distributed ignition control in homogeneous charge-compression ignition (HCCI) engines, among others. The present paper describes the current understanding of the nonequilibrium excitation of combustible mixtures by electrical discharges and plasma-assisted ignition and combustion. Nonequilibrium plasma demonstrates an ability to control ultra-lean, ultra-fast, low-temperature flames and appears to be an extremely promising technology for a wide range of applications, including aviation GTEs, piston engines, ramjets, scramjets and detonation initiation for pulsed detonation engines. To use nonequilibrium plasma for ignition and combustion in real energetic systems, one must understand the mechanisms of plasma-assisted ignition and combustion and be able to numerically simulate the discharge and combustion processes under various conditions.

  18. Demonstration of periodic nanostructure formation with less ablation by double-pulse laser irradiation on titanium

    NASA Astrophysics Data System (ADS)

    Furukawa, Yuki; Sakata, Ryoichi; Konishi, Kazuki; Ono, Koki; Matsuoka, Shusaku; Watanabe, Kota; Inoue, Shunsuke; Hashida, Masaki; Sakabe, Shuji

    2016-06-01

    By pairing femtosecond laser pulses (duration ˜40 fs and central wavelength ˜810 nm) at an appropriate time interval, a laser-induced periodic surface structure (LIPSS) is formed with much less ablation than one formed with a single pulse. On a titanium plate, a pair of laser pulses with fluences of 70 and 140 mJ/cm2 and a rather large time interval (>10 ps) creates a LIPSS with an interspace of 600 nm, the same as that formed by a single pulse of 210 mJ/cm2, while the double pulse ablates only 4 nm, a quarter of the ablation depth of a single pulse.

  19. Experimental scaling law for mass ablation rate from a Sn plasma generated by a 1064 nm laser

    SciTech Connect

    Burdt, Russell A.; Yuspeh, Sam; Najmabadi, Farrokh; Sequoia, Kevin L.; Tao Yezheng; Tillack, Mark S.

    2009-08-01

    The ablation depth in planar Sn targets irradiated with a pulsed 1064 nm laser was investigated over laser intensities from 3x10{sup 11} to 2x10{sup 12} W/cm{sup 2}. The ablation depth was measured by irradiating a thin layer of Sn evaporated onto a Si wafer, and looking for signatures of Si ions in the expanding plasma with spectroscopic and particle diagnostics. It was found that ablation depth scales with laser intensity to the (5/9)th power, which is consistent with analytical models of steady-state laser ablation, as well as empirical formulae from previous studies of mass ablation rate in overlapping parameter space. In addition, the scaling of mass ablation rate with atomic number of the target as given by empirical formulae in previous studies using targets such as C and Al, are shown to remain valid for the higher atomic number of the target (Z=50) used in these experiments.

  20. Ion extraction from positively biased laser-ablation plasma

    NASA Astrophysics Data System (ADS)

    Isono, Fumika; Nakajima, Mitsuo; Hasegawa, Jun; Horioka, Kazuhiko

    2016-07-01

    Ions were extracted through a grounded grid from a positively biased laser-ablation plasma and the behaviors were investigated. Since the plasma was positively biased against the grounded wall, we could extract the ions without insulated gap. We confirmed formation of a virtual anode when we increased the distance between the grid and the ion collector. Results also indicated that when the ion flux from the ablation plasma exceeded a critical value, the current was strongly suppressed to the space charge limited level due to the formation of virtual anode.

  1. Third harmonic generation in air ambient and laser ablated carbon plasma

    SciTech Connect

    Singh, Ravi Pratap Gupta, Shyam L.; Thareja, Raj K.

    2015-12-15

    We report the third harmonic generation of a nanosecond laser pulse (1.06 μm) in air ambient and in the presence of nanoparticles from laser ablated carbon plasma. Significant decrease in the threshold of third harmonic generation and multi-fold increment in the intensity of generated third harmonic is observed in presence of carbon plasma. The third harmonic in air is due to the quasi-resonant four photon process involving vibrationally excited states of molecular ion of nitrogen due to electron impact ionization and laser pulse. Following optical emission spectroscopic observations we conclude that the presence of C{sub 2} and CN in the ablated plume play a vital role in the observed third harmonic signals.

  2. Surface Modification of ICF Target Capsules by Pulsed Laser Ablation

    DOE PAGESBeta

    Carlson, Lane C.; Johnson, Michael A.; Bunn, Thomas L.

    2016-06-30

    Topographical modifications of spherical surfaces are imprinted on National Ignition Facility (NIF) target capsules by extending the capabilities of a recently developed full surface (4π) laser ablation and mapping apparatus. The laser ablation method combines the precision, energy density and long reach of a focused laser beam to pre-impose sinusoidal modulations on the outside surface of High Density Carbon (HDC) capsules and the inside surface of Glow Discharge Polymer (GDP) capsules. Sinusoidal modulations described in this paper have sub-micron to 10’s of microns vertical scale and wavelengths as small as 30 μm and as large as 200 μm. The modulatedmore » patterns are created by rastering a focused laser fired at discrete capsule surface locations for a specified number of pulses. The computer program developed to create these raster patterns uses inputs such as laser beam intensity profile, the material removal function, the starting surface figure and the desired surface figure. The patterns are optimized to minimize surface roughness. Lastly, in this paper, simulated surfaces are compared with actual ablated surfaces measured using confocal microscopy.« less

  3. Plasma shape control by pulsed solenoid on laser ion source

    NASA Astrophysics Data System (ADS)

    Sekine, M.; Ikeda, S.; Romanelli, M.; Kumaki, M.; Fuwa, Y.; Kanesue, T.; Hayashizaki, N.; Lambiase, R.; Okamura, M.

    2015-09-01

    A Laser ion source (LIS) provides high current heavy ion beams with a very simple mechanical structure. Plasma is produced by a pulsed laser ablation of a solid state target and ions are extracted by an electric field. However, it was difficult to manipulate the beam parameters of a LIS, since the plasma condition could only be adjusted by the laser irradiation condition. To enhance flexibility of LIS operation, we employed a pulsed solenoid in the plasma drift section and investigated the effect of the solenoid field on singly charged iron beams. The experimentally obtained current profile was satisfactorily controlled by the pulsed magnetic field. This approach may also be useful to reduce beam emittance of a LIS.

  4. Plasma shape control by pulsed solenoid on laser ion source

    DOE PAGESBeta

    Sekine, M.; Ikeda, S.; Romanelli, M.; Kumaki, M.; Fuwa, Y.; Kanesue, T.; Hayashizaki, N.; Lambiase, R.; Okamura, M.

    2015-05-28

    A Laser ion source (LIS) provides high current heavy ion beams with a very simple mechanical structure. Plasma is produced by a pulsed laser ablation of a solid state target and ions are extracted by an electric field. It was difficult to manipulate the beam parameters of a LIS, since the plasma condition could only be adjusted by the laser irradiation condition. To enhance flexibility of LIS operation, we employed a pulsed solenoid in the plasma drift section and investigated the effect of the solenoid field on singly charged iron beams. The experimentally obtained current profile was satisfactorily controlled bymore » the pulsed magnetic field. Thus, this approach may also be useful to reduce beam emittance of a LIS.« less

  5. Plasma shape control by pulsed solenoid on laser ion source

    SciTech Connect

    Sekine, M.; Ikeda, S.; Romanelli, M.; Kumaki, M.; Fuwa, Y.; Kanesue, T.; Hayashizaki, N.; Lambiase, R.; Okamura, M.

    2015-05-28

    A Laser ion source (LIS) provides high current heavy ion beams with a very simple mechanical structure. Plasma is produced by a pulsed laser ablation of a solid state target and ions are extracted by an electric field. It was difficult to manipulate the beam parameters of a LIS, since the plasma condition could only be adjusted by the laser irradiation condition. To enhance flexibility of LIS operation, we employed a pulsed solenoid in the plasma drift section and investigated the effect of the solenoid field on singly charged iron beams. The experimentally obtained current profile was satisfactorily controlled by the pulsed magnetic field. Thus, this approach may also be useful to reduce beam emittance of a LIS.

  6. A survey of pulse shape options for a revised plastic ablator ignition design

    SciTech Connect

    Clark, D. S.; Milovich, J. L.; Hinkel, D. E.; Salmonson, J. D.; Peterson, J. L.; Berzak Hopkins, L. F.; Eder, D. C.; Haan, S. W.; Jones, O. S.; Marinak, M. M.; Robey, H. F.; Smalyuk, V. A.; Weber, C. R.

    2014-11-15

    Recent experimental results using the “high foot” pulse shape for inertial confinement fusion ignition experiments on the National Ignition Facility (NIF) [Moses et al., Phys. Plasmas 16, 041006 (2009)] have shown encouraging progress compared to earlier “low foot” experiments. These results strongly suggest that controlling ablation front instability growth can significantly improve implosion performance even in the presence of persistent, large, low-mode distortions. Simultaneously, hydrodynamic growth radiography experiments have confirmed that ablation front instability growth is being modeled fairly well in NIF experiments. It is timely then to combine these two results and ask how current ignition pulse shapes could be modified to improve one-dimensional implosion performance while maintaining the stability properties demonstrated with the high foot. This paper presents such a survey of pulse shapes intermediate between the low and high foot extremes in search of an intermediate foot optimum. Of the design space surveyed, it is found that a higher picket version of the low foot pulse shape shows the most promise for improved compression without loss of stability.

  7. Pulsed metallic-plasma generators.

    NASA Technical Reports Server (NTRS)

    Gilmour, A. S., Jr.; Lockwood, D. L.

    1972-01-01

    A pulsed metallic-plasma generator is described which utilizes a vacuum arc as the plasma source. The arc is initiated on the surface of a consumable cathode which can be any electrically conductive material. Ignition is accomplished by using a current pulse to vaporize a portion of a conductive film on the surface of an insulator separating the cathode from the ignition electrode. The film is regenerated during the ensuing arc. Over 100 million ignition cycles have been accomplished by using four 0.125-in. diameter zinc cathodes operating in parallel and high-density aluminum-oxide insulators. Among the applications being investigated for the generator are metal deposition, vacuum pumping, electric propulsion, and high-power dc arc interruption.

  8. Pulsed laser ablation growth and doping of epitaxial compound semiconductor films

    SciTech Connect

    Lowndes, D.H.; Rouleau, C.M.; Geohegan, D.B.; Budai, J.D.; Poker, D.B.; Puretzky, A.A.; Strauss, M.A.; Pedraza, A.J.; Park, J.W.

    1995-12-01

    Pulsed laser ablation (PLA) has several characteristics that are potentially attractive for the growth and doping of chemically complex compound semiconductors including (1) stoichiometric (congruent) transfer of composition from target to film, (2) the use of reactive gases to control film composition and/or doping via energetic-beam-induced reactions, and (3) low-temperature nonequilibrium phase formation in the laser-generated plasma ``plume.`` However, the electrical properties of compound semiconductors are far more sensitive to low concentrations of defects than are the oxide metals/ceramics for which PLA has been so successful. Only recently have doped epitaxial compound semiconductor films been grown by PLA. Fundamental studies are being carried out to relate film electrical and microstructural properties to the energy distribution of ablated species, to the temporal evolution of the ablation pulse in ambient gases, and to beam assisted surface and/or gas-phase reactions. In this paper the authors describe results of ex situ Hall effect, high-resolution x-ray diffraction, transmission electron microscopy, and Rutherford backscattering measurements that are being used in combination with in situ RHEED and time-resolved ion probe measurements to evaluate PLA for growth of doped epitaxial compound semiconductor films and heterostructures. Examples are presented and results analyzed for doped II-VI, I-III-VI, and column-III nitride materials grown recently in this and other laboratories.

  9. Synthesis of silver nanoparticles and antimony oxide nanocrystals by pulsed laser ablation in liquid media

    NASA Astrophysics Data System (ADS)

    Mendivil, M. I.; Krishnan, B.; Sanchez, F. A.; Martinez, S.; Aguilar-Martinez, J. A.; Castillo, G. A.; Garcia-Gutierrez, D. I.; Shaji, S.

    2013-03-01

    Pulsed laser ablation in liquid media (PLALM) is a prominent technique for the controlled fabrication of nanomaterials via rapid reactive quenching of ablated species at the interface between the plasma and liquid. Results on nanoparticles and nanocrystals formed by PLALM of silver (Ag) and antimony (Sb) solid targets in different liquid environments (Sodium Dodecyl Sulfate, distilled water) are presented. These experiments were done by irradiating solid targets of Ag and Sb with a nanosecond pulsed Nd:YAG laser output of wavelength 532 nm. Nanoparticles of silver and nanocrystals of antimony oxide (Sb2O3) obtained were characterized using UV-Vis spectrometry, Scanning Electron Microscopy (SEM), transmission electron microscopy (TEM), X-ray Energy Dispersion Analysis (EDAX) and X-ray diffractometry (XRD). The morphology of nanomaterials formed is studied as a function of surfactant environment. The silver nanoparticles obtained were spherical of size in the order of 10-35 nm in solution of SDS having different concentrations. In case of the Sb target, ablation was performed in two different molarities of SDS solution and distilled water. Nanocrystals of Sb2O3 in powder form having cubic and orthorhombic phases were formed in SDS solution and as fibers of nanocrystals of cubic Sb2O3 in distilled water.

  10. Molecular signatures in femtosecond laser-induced organic plasmas: comparison with nanosecond laser ablation.

    PubMed

    Serrano, Jorge; Moros, Javier; Laserna, J Javier

    2016-01-28

    During the last few years, laser-induced breakdown spectroscopy (LIBS) has evolved significantly in the molecular sensing area through the optical monitoring of emissions from organic plasmas. Large efforts have been made to study the formation pathways of diatomic radicals as well as their connections with the bonding framework of molecular solids. Together with the structural and chemical-physical properties of molecules, laser ablation parameters seem to be closely tied to the observed spectral signatures. This research focuses on evaluating the impact of laser pulse duration on the production of diatomic species that populate plasmas of organic materials. Differences in relative intensities of spectral signatures from the plasmas of several organic molecules induced in femtosecond (fs) and nanosecond (ns) ablation regimes have been studied. Beyond the abundance and origin of diatomic radicals that seed the plasma, findings reveal the crucial role of the ablation regime in the breakage pattern of the molecule. The laser pulse duration dictates the fragments and atoms resulting from the vaporized molecules, promoting some formation routes at the expense of other paths. The larger amount of fragments formed by fs pulses advocates a direct release of native bonds and a subsequent seeding of the plasma with diatomic species. In contrast, in the ns ablation regime, the atomic recombinations and single displacement processes dominate the contribution to diatomic radicals, as long as atomization of molecules prevails over their progressive decomposition. Consequently, fs-LIBS better reflects correlations between strengths of emissions from diatomic species and molecular structure as compared to ns-LIBS. These new results entail a further step towards the specificity in the analysis of molecular solids by fs-LIBS. PMID:26695078

  11. Imaging the ultrafast Kerr effect, free carrier generation, relaxation and ablation dynamics of Lithium Niobate irradiated with femtosecond laser pulses

    SciTech Connect

    Garcia-Lechuga, Mario Siegel, Jan Hernandez-Rueda, Javier; Solis, Javier

    2014-09-21

    The interaction of high-power single 130 femtosecond (fs) laser pulses with the surface of Lithium Niobate is experimentally investigated in this work. The use of fs-resolution time-resolved microscopy allows us to separately observe the instantaneous optical Kerr effect induced by the pulse and the generation of a free electron plasma. The maximum electron density is reached 550 fs after the peak of the Kerr effect, confirming the presence of a delayed carrier generation mechanism. We have also observed the appearance of transient Newton rings during the ablation process, related to optical interference of the probe beam reflected at the front and back surface of the ablating layer. Finally, we have analyzed the dynamics of the photorefractive effect on a much longer time scale by measuring the evolution of the transmittance of the irradiated area for different fluences below the ablation threshold.

  12. Single-shot ablation threshold of chromium using UV femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Banerjee, S. P.; Fedosejevs, R.

    2014-07-01

    Single-shot ablation threshold for thin chromium film was studied using 266 nm, femtosecond laser pulses. Chromium is a useful material in the nanotechnology industry and information on ablation threshold using UV femtosecond pulses would help in precise micromachining of the material. The ablation threshold was determined by measuring the ablation crater diameters as a function of incident laser pulse energy. Absorption of 266 nm light on the chromium film was also measured under our experimental conditions, and the absorbed energy single-shot ablation threshold fluence was 46 ± 5 mJ/cm2. The experimental ablation threshold fluence value was compared to time-dependent heat flow calculations based on the two temperature model for ultrafast laser pulses. The model predicts a value of 31.6 mJ/cm2 which is qualitatively consistent with the experimentally obtained value, given the simplicity of the model.

  13. Optical probe investigation of laser ablated carbon plasma plume in nitrogen ambient

    SciTech Connect

    Singh, Ravi Pratap; Gupta, Shyam L.; Thareja, Raj K.

    2013-12-15

    We report the study of carbon plasma produced using 1064 nm laser in nitrogen ambient at atmospheric pressure using 2-dimensional fast imaging of ablated plume, optical emission spectroscopy, and optical probe at 532 nm for interferometry and shadowgraphy. The dominance of C{sub 2} and CN molecules over ionic species at later stages of expanding carbon plasma plume is reported. The observed ring structure in shadowgrams and change in the direction of fringe shift from positive to negative in recorded interferograms are correlated with the relative abundance of different species in the plasma plume as function of time delay with respect to ablating pulse. An agreement in observed onset time of formation of clusters/atomic species or low ionic species using different diagnostic techniques has been reported.

  14. Effects of pulsed CO2 laser in caries selective ablation

    NASA Astrophysics Data System (ADS)

    Colojoara, Carmen; David, Ion; Marinovici, Mariana

    1995-03-01

    We have evaluated the effect of pulsed carbon dioxide laser in the treatment for deep carious decay. The so called `caries profonda' is still a problem for conservative dentistry. A `Valvfivre' Master 20S carbon dioxide laser was pulsed to determine the effects on dentine and for testing the properties of softened dentine in selective ablation. Laser treatment parameters were from 1 to 2 W, 50 to 150 ms, 200 to 320 Hz. Fifteen human teeth samples were exposed to irradiation: extracted third molar were exposed to CO2 pulsed laser to determine in vitro the effects on pulp morphology. The tissue samples were analyzed histologically and by means of scanning electron microscopy for evidence of thermal damage. Next, we have evaluated the morphologic changes in vivo on 10 cases in patients with deep carious decay. Pulsed infrared lasers are capable of inducing physical and chemical changes in dentine structure. The results showed an artificially sclerosing and micro-hardness on the remaining dentine. CO2 laser can vaporized carious dentine.

  15. 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}.

  16. Investigation of Early Plasma Evolution Induced by Ultrashort Laser Pulses

    PubMed Central

    Hu, Wenqian; Shin, Yung C.; King, Galen B.

    2012-01-01

    Early plasma is generated owing to high intensity laser irradiation of target and the subsequent target material ionization. Its dynamics plays a significant role in laser-material interaction, especially in the air environment1-11. Early plasma evolution has been captured through pump-probe shadowgraphy1-3 and interferometry1,4-7. However, the studied time frames and applied laser parameter ranges are limited. For example, direct examinations of plasma front locations and electron number densities within a delay time of 100 picosecond (ps) with respect to the laser pulse peak are still very few, especially for the ultrashort pulse of a duration around 100 femtosecond (fs) and a low power density around 1014 W/cm2. Early plasma generated under these conditions has only been captured recently with high temporal and spatial resolutions12. The detailed setup strategy and procedures of this high precision measurement will be illustrated in this paper. The rationale of the measurement is optical pump-probe shadowgraphy: one ultrashort laser pulse is split to a pump pulse and a probe pulse, while the delay time between them can be adjusted by changing their beam path lengths. The pump pulse ablates the target and generates the early plasma, and the probe pulse propagates through the plasma region and detects the non-uniformity of electron number density. In addition, animations are generated using the calculated results from the simulation model of Ref. 12 to illustrate the plasma formation and evolution with a very high resolution (0.04 ~ 1 ps). Both the experimental method and the simulation method can be applied to a broad range of time frames and laser parameters. These methods can be used to examine the early plasma generated not only from metals, but also from semiconductors and insulators. PMID:22806170

  17. Sampling modulation technique in radio-frequency helium glow discharge emission source by use of pulsed laser ablation.

    PubMed

    Naeem, Tariq Mahmood; Matsuta, Hideyuki; Wagatsuma, Kazuaki

    2004-05-01

    An emission excitation source comprising a high-frequency diode-pumped Q-switched Nd:YAG laser and a radio-frequency powered glow discharge lamp is proposed. In this system sample atoms ablated by the laser irradiation are introduced into the lamp chamber and subsequently excited by the helium glow discharge plasma. The pulsed operation of the laser can produce a cyclic variation in the emission intensities of the sample atoms whereas the plasma gas species emit the radiation continuously. The salient feature of the proposed technique is the selective detection of the laser modulation signal from the rest of the continuous background emissions, which can be achieved with the phase sensitive detection of the lock-in amplifier. The arrangement may be used to estimate the emission intensity of the laser ablated atom, free from the interference of other species present in the plasma. The experiments were conducted with a 13.56 MHz radio-frequency (rf) generator operated at 80 W power to produce plasma and the laser at a wavelength of 1064 nm (pulse duration:34 ns, repetition rate:7 kHz and average pulse energy of about 0.36 mJ) was employed for sample ablation. The measurements resulted in almost complete removal of nitrogen molecular bands (N(2)(+) 391.44 nm). Considerable reduction (about 75%) in the emission intensity of a carbon atomic line (C I 193.03 nm) was also observed. PMID:15034707

  18. Fast surface temperature measurement of Teflon propellant-in-pulsed ablative discharges using HgCdTe photovoltaic cells

    SciTech Connect

    Antonsen, Erik L.; Burton, Rodney L.; Reed, Garrett A.; Spanjers, Gregory G.

    2006-10-15

    High-speed mercury cadmium telluride photovoltaic detectors, sensitive to infrared emission, are investigated as a means of measuring surface temperature on a microsecond time frame during pulsed ablative discharges with Teflon trade mark sign as the ablated material. Analysis is used to derive a governing equation for detector output voltage for materials with wavelength dependent emissivity. The detector output voltage is experimentally calibrated against thermocouples embedded in heated Teflon. Experimental calibration is performed with Teflon that has been exposed to {approx}200 pulsed discharges and non-plasma-exposed Teflon and is compared to theoretical predictions to analyze emissivity differences. The diagnostic capability is evaluated with measurements of surface temperature from the Teflon propellant of electric micropulsed plasma thrusters. During the pulsed current discharge, there is insufficient information to claim that the surface temperature is accurately measured. However, immediately following the discharge, the postpulse cooling curve is measured. The statistical spread of postpulse surface temperature from shot to shot, most likely due to arc constriction and localization, is investigated to determine an operational envelope for postpulse temperature and mass ablation. This information is useful for determining postpulse ablation contributions to mass loss as well as evaluation of theoretical discharge models currently under development.

  19. A new sealed RF-excited CO2 laser for enamel ablation operating at 9.4μm with pulse duration of 26 μs

    NASA Astrophysics Data System (ADS)

    Chan, Kenneth H.; Jew, Jamison M.; Fried, Daniel

    2016-02-01

    Several studies over the past 20 years have identified that carbon dioxide lasers operating at wavelengths between 9.3 and 9.6-μm with pulse durations near 20-µs are ideal for hard tissue ablation. Those wavelengths are coincident with the peak absorption of the mineral phase and the pulse duration is close to the thermal relaxation time of the deposited energy of a few microseconds to minimize peripheral thermal damage and long enough to minimize plasma shielding effects to allow efficient ablation at practical rates. The desired pulse duration near 20-μs has been difficult to achieve since it is too long for TEA lasers and too short for RF-excited lasers for efficient operation. Recently, Coherent Inc. (Santa Clara, CA) developed the J5-V laser for microvia drilling which can produce laser pulses greater than 100 mJ in energy at 9.4-μm with a pulse duration of 26-µs and it can achieve pulse repetition rates of 3 KHz. We report the first results using this laser to ablate enamel and dentin. The onset of plasma shielding does not occur until the fluence exceeds 100 J/cm2 allowing efficient ablation at rates exceeding 50-μm per pulse. This laser is ideally suited for the selective ablation of carious lesions.

  20. Dynamics of ultrashort pulsed laser radiation induced non-thermal ablation of graphite

    NASA Astrophysics Data System (ADS)

    Reininghaus, M.; Kalupka, C.; Faley, O.; Holtum, T.; Finger, J.; Stampfer, C.

    2014-12-01

    We report on the dependence of a laser radiation induced ablation process of graphite on the applied pulse duration of ultrashort pulsed laser radiation smaller than 4 ps. The emerging so-called non-thermal ablation process of graphite has been confirmed to be capable to physically separate ultrathin graphitic layers from the surface of pristine graphite bulk crystal. This allows the deposition of ablated graphitic flakes on a substrate in the vicinity of the target. The observed ablation threshold determined at different pulse durations shows a modulation, which we ascribe to lattice motions along the c axis that are theoretically predicted to induce the non-thermal ablation process. In a simple approach, the ablation threshold can be described as a function of the energy penetration depth and the absorption of the applied ultrashort pulsed laser radiation. Based on the analysis of the pulse duration dependence of those two determining factors and the assumption of an invariant ablation process, we are able to reproduce the pulse duration dependence of the ablation threshold. Furthermore, the observed pulse duration dependences confirm the assumption of a fast material specific response of graphite target subsequent to optical excitation within the first 2 ps.

  1. Nanosecond pulsed laser ablation of Ge investigated by employing photoacoustic deflection technique and SEM analysis

    NASA Astrophysics Data System (ADS)

    Yaseen, Nazish; Bashir, Shazia; Shabbir, Muhammad Kaif; Jalil, Sohail Abdul; Akram, Mahreen; Hayat, Asma; Mahmood, Khaliq; Haq, Faizan-ul; Ahmad, Riaz; Hussain, Tousif

    2016-06-01

    Nanosecond pulsed laser ablation phenomena of single crystal Ge (100) has been investigated by employing photoacoustic deflection as well as SEM analysis techniques. Nd: YAG laser (1064 nm, 10 ns, 1-10 Hz) at various laser fluences ranging from 0.2 to 11 J cm-2 is employed as pump beam to ablate Ge targets. In order to evaluate in-situe ablation threshold fluence of Ge by photoacoustic deflection technique, Continuous Wave (CW) He-Ne laser (632 nm, power 10 mW) is employed as a probe beam. It travels parallel to the target surface at a distance of 3 mm and after passing through Ge plasma it causes deflection due to density gradient of acoustic waves. The deflected signal is detected by photodiode and is recorded by oscilloscope. The threshold fluence of Ge, the velocity of ablated species and the amplitude of the deflected signal are evaluated. The threshold fluence of Ge comes out to be 0.5 J cm-2 and is comparable with the analytical value. In order to compare the estimated value of threshold with ex-situe measurements, the quantitative analysis of laser irradiated Ge is performed by using SEM analysis. For this purpose Ge is exposed to single and multiple shots of 5, 10, 50 and 100 at various laser fluences ranging from 0.2 to 11 J cm-2. The threshold fluence for single and multiple shots as well as incubation coefficients are evaluated. It is observed that the value of incubation co-efficient decreases with increasing number of pulses and is therefore responsible for lowering the threshold fluence of Ge. SEM analysis also reveals the growth of various features such as porous structures, non-uniform ripples and blisters on the laser irradiated Ge. It is observed that both the fluence as well as number of laser shots plays a significant role for the growth of these structures.

  2. Femtosecond pulse laser ablation of metallic, semiconducting, ceramic, and biological materials

    NASA Astrophysics Data System (ADS)

    Kautek, Wolfgang; Krueger, Joerg

    1994-09-01

    Production of holes and grooves of < 30 micrometers diameter with high aspect ratio value is a delicate task either for mechanical tools, or for conventional nanosecond pulse lasers like e.g. pulsed Nd:YAG or excimer lasers. They later tend to cause microcracks extending from an annular melting zone, or substantial disruption, respectively. Experimental results are presented which demonstrate that the development of intense ultrashort pulse laser systems (>> 1012 W cm-2, (tau) < 1 ps) opens up possibilities for materials processing by cold plasma generation and ablation of metals, semiconductors, ceramics, composites, and biological materials. A femtosecond and a nanosecond dye laser with pulse durations of 300 fs (< 200 (mu) J) and 7 ns (< 10 mJ), and center wavelengths at 612 and 600 nm, respectively, both focused on an area of the order of 10-5 cm2, have been applied either to absorbing substrates, like polycrystalline gold, silicon (111), aluminum nitride ceramics, or transparent materials, like synthetic and human dental hydroxyapatite composites, bone material, and human cornea transplants. The fs-laser generates its own absorption in transparent materials by a multiphoton absorption process, and thus forces the absorption of visible radiation. Because the time is too short (< ps) for significant transport of mass and energy, the beam interaction generally results in the formation of a thin plasma layer of approximately solid state density. Only after the end of the subpicosecond laser pulse, it expands rapidly away from the surface without any light absorption and further plasma heating. Therefore, energy transfer (heat and impulse) to the target material, and thermal and mechanical disruption are minimized. In contrast to heat- affected zones (HAZ's) generated by conventional nanosecond pulse lasers of the order of 1 - 10 micrometers , HAZ's of less than 0.02 micrometers were observed.

  3. Pulsed plasma thruster contamination studies

    NASA Technical Reports Server (NTRS)

    Rudolph, L. K.; Jones, R. M.

    1979-01-01

    The exhaust plume of the one millipound pulsed plasma thruster has a measurable backflow upstream of the nozzle exit plane which may deposit on and degrade the performance of exposed spacecraft surfaces. High speed photographs and Faraday cup measurements suggest that this backflow is predominantly an electrically neutral, relatively low energy vapor. Articulated collimator quartz crystal microbalance measurements of this backflow were made for a thruster with a radically modified nozzle and a flat plate backflow shield, to determine the backflow sensitivity to nozzle design changes. The results are compared with the original nozzle backflow and show a measurable reduction in the backflow directly upstream of the shield.

  4. Pulsed plasma etching for semiconductor manufacturing

    NASA Astrophysics Data System (ADS)

    Economou, Demetre J.

    2014-07-01

    Power-modulated (pulsed) plasmas have demonstrated several advantages compared to continuous wave (CW) plasmas. Specifically, pulsed plasmas can result in a higher etching rate, better uniformity, and less structural, electrical or radiation (e.g. vacuum ultraviolet) damage. Pulsed plasmas can also ameliorate unwanted artefacts in etched micro-features such as notching, bowing, micro-trenching and aspect ratio dependent etching. As such, pulsed plasmas may be indispensable in etching of the next generation of micro-devices with a characteristic feature size in the sub-10 nm regime. This work provides an overview of principles and applications of pulsed plasmas in both electropositive (e.g. argon) and electronegative (e.g. chlorine) gases. The effect of pulsing the plasma source power (source pulsing), the electrode bias power (bias pulsing), or both source and bias power (synchronous pulsing), on the time evolution of species densities, electron energy distribution function and ion energy and angular distributions on the substrate is discussed. The resulting pulsed plasma process output (etching rate, uniformity, damage, etc) is compared, whenever possible, to that of CW plasma, under otherwise the same or similar conditions.

  5. Resonant laser ablation of metals detected by atomic emission in a microwave plasma and by inductively coupled plasma mass spectrometry.

    PubMed

    Cleveland, Danielle; Stchur, Peter; Hou, Xiandeng; Yang, Karl X; Zhou, Jack; Michel, Robert G

    2005-12-01

    It has been shown that an increase in sensitivity and selectivity of detection of an analyte can be achieved by tuning the ablation laser wavelength to match that of a resonant gas-phase transition of that analyte. This has been termed resonant laser ablation (RLA). For a pulsed tunable nanosecond laser, the data presented here illustrate the resonant enhancement effect in pure copper and aluminum samples, chromium oxide thin films, and for trace molybdenum in stainless steel samples, and indicate two main characteristics of the RLA phenomenon. The first is that there is an increase in the number of atoms ablated from the surface. The second is that the bandwidth of the wavelength dependence of the ablation is on the order of 1 nm. The effect was found to be virtually identical whether the atoms were detected by use of a microwave-induced plasma with atomic emission detection, by an inductively coupled plasma with mass spectrometric detection, or by observation of the number of laser pulses required to penetrate through thin films. The data indicate that a distinct ablation laser wavelength dependence exists, probably initiated via resonant radiation trapping, and accompanied by collisional broadening. Desorption contributions through radiation trapping are substantiated by changes in crater morphology as a function of wavelength and by the relatively broad linewidth of the ablation laser wavelength scans, compared to gas-phase excitation spectra. Also, other experiments with thin films demonstrate the existence of a distinct laser-material interaction and suggest that a combination of desorption induced by electronic transition (DIET) with resonant radiation trapping could assist in the enhancement of desorption yields. These results were obtained by a detailed inspection of the effect of the wavelength of the ablation laser over a narrow range of energy densities that lie between the threshold of laser-induced desorption of species and the usual analytical

  6. Dual beam optical system for pulsed laser ablation film deposition

    DOEpatents

    Mashburn, D.N.

    1996-09-24

    A laser ablation apparatus having a laser source outputting a laser ablation beam includes an ablation chamber having a sidewall, a beam divider for dividing the laser ablation beam into two substantially equal halves, and a pair of mirrors for converging the two halves on a surface of the target from complementary angles relative to the target surface normal, thereby generating a plume of ablated material emanating from the target. 3 figs.

  7. Performance loss due to wall ablation in plasma armature railguns

    NASA Astrophysics Data System (ADS)

    Parker, J. V.; Parsons, W. M.; Cummings, C. E.; Fox, W. E.

    1985-07-01

    Parametric measurements have been performed on a plasma armature railgun at Los Alamos. The railgun is extensively instrumented for studies of the projectile motion and its interaction with the plasma armature. The most important parameter, driving current, was varied from 100 kA to 400 kA. Additional parameters investigated include current waveform, injection velocity, injection gas, wall insulation material, and initial pressure. For all combinations of parameters investigated, the measured performance was substantially below theoretical predictions. A strong correlation was found between performance loss and abnormal plasma armature features such as multiple arc formation, or separation of the armature from the projectile. In extreme cases, the plasma armature was observed to come to rest inside the railgun. A plasma armature model has been developed which successfully accounts for the measured performance loss and for many of the abnormal plasma armature features. By incorporating the ablation of wall material into the armature plasma this model predicts two parasitic forces that dominate the motion of the armature at high velocity. One force is the inertial drag term m dot sub a v. The other is frictional drag between the hot, turbulent plasma and the walls, which increases M sub a v squared. Simple scaling relations, which incorporate the plasma armature model, show that velocities less than 10 km/s will be extremely difficult to achieve with plasma armature railguns unless the effects of ablation are eliminated or carefully controlled.

  8. Ablation and analysis of small cell populations and single cells by consecutive laser pulses

    NASA Astrophysics Data System (ADS)

    Shrestha, Bindesh; Nemes, Peter; Vertes, Akos

    2010-10-01

    Laser ablation of single cells through a sharpened optical fiber is used for the detection of metabolites by laser ablation electrospray ionization (LAESI) mass spectrometry (MS). Ablation of the same Allium cepa epidermal cell by consecutive pulses indicates the rupture of the cell wall by the second shot. Intracellular sucrose heterogeneity is detected by subsequent laser pulses pointing to rupturing the vacuolar membrane by the third exposure. Ion production by bursts of laser pulses shows that the drying of ruptured A. cepa cells occurs in ˜50 s at low pulse rates (10 pulses/s bursts) and significantly faster at high pulse rates (100 pulses/s bursts). These results point to the competing role of cytoplasm ejection and evaporative drying in diminishing the LAESI-MS signal in ˜50 s or 100 laser pulses, whichever occurs first.

  9. Laser ablation inductively coupled plasma mass spectrometry measurement of isotope ratios in depleted uranium contaminated soils.

    PubMed

    Seltzer, Michael D

    2003-09-01

    Laser ablation of pressed soil pellets was examined as a means of direct sample introduction to enable inductively coupled plasma mass spectrometry (ICP-MS) screening of soils for residual depleted uranium (DU) contamination. Differentiation between depleted uranium, an anthropogenic contaminant, and naturally occurring uranium was accomplished on the basis of measured 235U/238U isotope ratios. The amount of sample preparation required for laser ablation is considerably less than that typically required for aqueous sample introduction. The amount of hazardous laboratory waste generated is diminished accordingly. During the present investigation, 235U/238U isotope ratios measured for field samples were in good agreement with those derived from gamma spectrometry measurements. However, substantial compensation was required to mitigate the effects of impaired pulse counting attributed to sample inhomogeneity and sporadic introduction of uranium analyte into the plasma. PMID:14611049

  10. Growth of metal oxide nanoparticles using pulsed laser ablation technique

    NASA Astrophysics Data System (ADS)

    Gondal, M. A.; Drmosh, Q. A.; Saleh, Tawfik A.; Yamani, Z. H.

    2011-02-01

    Nano particles exhibit physical and chemical properties distinctively different from that of bulk due to high number of surface atoms, surface energy and surface area to volume ratio. Laser is a unique source of radiation and has been applied in the synthesis of nano structured metal oxides. The pulsed laser ablation (PLA) technique in liquid medium has been proven an effective and simple technique for preparing nanoparticles of high purity. Pulsed laser deposition (PLD) is another way to fabricate nano structured single crystal thin films of metal oxides. PLA technique has been applied in our laboratory for the growth of metal oxides such as nano-ZnO, nano-ZnO2 nano- SnO2, nano-Bi2O3, nano-NiO and nano-MnO2. Different techniques such as AFM, UV, FT-IR, PL and XRD were applied to characterize these materials. We will present our latest development in the growth of nano metal oxides using PLA and PLD.

  11. Ultrashort laser pulse ablation of copper, silicon and gelatin: effect of the pulse duration on the ablation thresholds and the incubation coefficients

    NASA Astrophysics Data System (ADS)

    Nathala, Chandra S. R.; Ajami, Ali; Husinsky, Wolfgang; Farooq, Bilal; Kudryashov, Sergey I.; Daskalova, Albena; Bliznakova, Irina; Assion, Andreas

    2016-02-01

    In this paper, the influence of the pulse duration on the ablation threshold and the incubation coefficient was investigated for three different types of materials: metal (copper), semiconductor (silicon) and biopolymer (gelatin). Ablation threshold values and the incubation coefficients have been measured for multiple Ti:sapphire laser pulses (3 to 1000 pulses) and for four different pulse durations (10, 30, 250 and 550 fs). The ablation threshold fluence was determined by extrapolation of curves from squared crater diameter versus fluence plots. For copper and silicon, the experiments were conducted in vacuum and for gelatin in air. For all materials, the ablation threshold fluence increases with the pulse duration. For copper, the threshold increases as τ 0.05, for silicon as τ 0.12 and for gelatin as τ 0.22. By extrapolating the curves of the threshold fluence versus number of pulses, the single-shot threshold fluence was determined for each sample. For 30 fs pulses, the single-shot threshold fluences were found to be 0.79, 0.35, and 0.99 J/cm2 and the incubation coefficients were found to be 0.75, 0.83 and 0.68 for copper, silicon and gelatin, respectively.

  12. Morphological effects of nanosecond- and femtosecond-pulsed laser ablation on human middle ear ossicles

    NASA Astrophysics Data System (ADS)

    Ilgner, Justus F. R.; Wehner, Martin M.; Lorenzen, Johann; Bovi, Manfred; Westhofen, Martin

    2006-01-01

    We evaluate the feasibility of nanosecond-pulsed and femtosecond-pulsed lasers for otologic surgery. The outcome parameters are cutting precision (in micrometers), ablation rate (in micrometers per second), scanning speed (in millimeters per second), and morphological effects on human middle ear ossicles. We examine single-spot ablations by a nanosecond-pulsed, frequency-tripled Nd:YAG laser (355 nm, beam diameter 10µm, pulse rate 2 kHz, power 250 mW) on isolated human mallei. A similar system (355 nm, beam diameter 20µm, pulse rate 10 kHz, power 160-1500 mW) and a femtosecond-pulsed CrLi:SAF-Laser (850 nm, pulse duration 100 fs, pulse energy 40 µJ, beam diameter 36 µm, pulse rate 1 kHz) are coupled to a scanner to perform bone surface ablation over a defined area. In our setups 1 and 2, marginal carbonization is visible in all single-spot ablations of 1-s exposures and longer: With an exposure time of 0.5 s, precise cutting margins without carbonization are observed. Cooling with saline solution result is in no carbonization at 1500 mW and a scan speed of 500 mm/s. Our third setup shows no carbonization but greater cutting precision, although the ablation volume is lower. Nanosecond- and femtosecond-pulsed laser systems bear the potential to increase cutting precision in otologic surgery.

  13. Computational study of nanosecond pulsed laser ablation and the application to momentum coupling

    SciTech Connect

    Yuan Hong; Tong Huifeng; Li Mu; Sun Chengwei

    2012-07-15

    During the evaporation and ablation of a matter induced by intensive laser radiation, the vapor plasma is ejected from the surface of the target which induces the recoil pressure and impulse in the target. Impulse coupling of laser beams with matter has been extensively studied as the basis of laser propulsion and laser clearing space debris. A one-dimensional (1D) bulk absorption model to simulate the solid target ablated directly by the laser beam is presented; numerical calculation of impulse acting on the target in vacuum with different laser parameters is performed with fluid dynamics theory and 1D Lagrange difference scheme. The calculated results of the impulse coupling coefficients are in good agreement with the experimental results and Phipps' empirical value. The simulated results show that the mechanical coupling coefficients decrease with the increment of laser intensity when the laser pulses generate plasma. The present model can be applied when the laser intensity is 10{sup 8} - 10{sup 10} W/cm{sup 2}, which will provide a guide to the study of momentum coupling of laser beams with matter.

  14. Laser ablation in a liquid-confined environment using a nanosecond laser pulse

    NASA Astrophysics Data System (ADS)

    Kang, Hyun Wook; Lee, Ho; Welch, Ashley J.

    2008-04-01

    Laser ablation of aluminum metal with 1ns, 800nm pulse at low radiant exposures was investigated in air (dry) and water (wet) environments. Compared to dry ablation, an approximately eight times increase in material removal rate was associated with wet ablation. Based on optical reflectance and scanning electron microscope images, bubble formation/collapse was responsible for augmented acoustic pressure and ablation performance. Numerically simulated temperature distributions during wet ablation were consistent with the occurrence of explosive water vaporization near the critical temperature of water. Strong pressure emission during liquid vaporization and jet formation can account for enhanced ablation process. Radial expansion of bubbles minimized the redeposition of debris, leading to improvements in energy coupling to the target and ablation performance.

  15. Pulse-width-dependent surface ablation of copper and silver by ultrashort laser pulses

    NASA Astrophysics Data System (ADS)

    Zayarny, Dmitry A.; Ionin, Andrey A.; Kudryashov, Sergey I.; Makarov, Sergey V.; Kuchmizhak, Alexander A.; Vitrik, Oleg B.; Kulchin, Yury N.

    2016-07-01

    The single-shot spallation thresholds for copper and silver surfaces demonstrate a considerable IR-laser (1030 nm) pulse-width dependent increase over a range of 0.2–12 ps for the former material and a very weak increase for the latter one, while the corresponding thresholds for visible (515 nm) laser pulses remain almost constant. The IR-laser increase of the ablation thresholds is related to two-photon interband (d–s) absorption in copper, contrasting with the linear absorption of visible laser pulses in this material. In silver, common weakly sublinear dependences on the laser pulsewidth were observed, ruling out possible multi-photon—either three(four)-photon in IR, or two-photon in the visible range—interband transitions in this material. Moreover, electron-lattice thermalization times of 1–2 ps were evaluated for these materials in the spallative ablation regime, contrasting strongly with the previously theoretically predicted multi-picosecond thermalization times.

  16. An observation of ablation effect of soft biotissue by pulsed Er:YAG laser

    NASA Astrophysics Data System (ADS)

    Zhang, Xianzeng; Xie, Shusen; Ye, Qing; Zhan, Zhenlin

    2007-02-01

    Because of the unique properties with regard to the absorption in organic tissue, pulsed Er:YAG laser has found most interest for various application in medicine, such as dermatology, dentistry, and cosmetic surgery. However, consensus regarding the optimal parameters for clinical use of this tool has not been reached. In this paper, the laser ablation characteristics of soft tissue by Er:YAG laser irradiation was studied. Porcine skin tissue in vitro was used in the experiment. Laser fluences ranged from 25mJ/mm2 to 200mJ/mm2, repetition rates was 5Hz, spot sizes on the tissue surface was 2mm. The ablation effects were assessed by the means of optical microscope, ablation diameters and depths were measured with reading microscope. It was shown that the ablation of soft biotissue by pulsed Er:YAG laser was a threshold process. With appropriate choice of irradiation parameters, high quality ablation with clean, sharp cuts following closely the spatial contour of the incident beam can be achieved. The curves of ablation crater diameter and depth versus laser fluence were obtained, then the ablation threshold and ablation yield were calculated subsequently, and the influence of the number of pulses fired into a crater on ablation crater depth was also discussed.

  17. Experimental investigation of vapor shielding effects induced by ELM-like pulsed plasma loads using the double plasma gun device

    NASA Astrophysics Data System (ADS)

    Sakuma, I.; Kikuchi, Y.; Kitagawa, Y.; Asai, Y.; Onishi, K.; Fukumoto, N.; Nagata, M.

    2015-08-01

    We have developed a unique experimental device of so-called double plasma gun, which consists of two magnetized coaxial plasma gun (MCPG) devices, in order to clarify effects of vapor shielding on material erosion due to transient events in magnetically confined fusion devices. Two ELM-like pulsed plasmas produced by the two MCPG devices were injected into a target chamber with a variable time difference. For generating ablated plasmas in front of a target material, an aluminum foil sample in the target chamber was exposed to a pulsed plasma produced by the 1st MCPG device. The 2nd pulsed plasma was produced with a time delay of 70 μs. It was found that a surface absorbed energy measured by a calorimeter was reduced to ∼66% of that without the Al foil sample. Thus, the reduction of the incoming plasma energy by the vapor shielding effect was successfully demonstrated in the present experiment.

  18. Ablation of high-Z material dust grains in edge plasmas of magnetic fusion devices

    SciTech Connect

    Marenkov, E. D.; Krasheninnikov, S. I.

    2014-12-15

    The model, including shielding effects of high-Z dust grain ablation in tokamak edge plasma, is presented. In a contrast to shielding models developed for pellets ablation in a hot plasma core, this model deals with the dust grain ablation in relatively cold edge plasma. Using some simplifications, a closed set of equations determining the grain ablation rate Γ is derived and analyzed both analytically and numerically. The scaling law for Γ versus grain radius and ambient plasma parameters is obtained and confirmed by the results of numerical solutions. The results obtained are compared with both dust grain models containing no shielding effects and the pellet ablation models.

  19. Ablation of high-Z material dust grains in edge plasmas of magnetic fusion devices

    NASA Astrophysics Data System (ADS)

    Marenkov, E. D.; Krasheninnikov, S. I.

    2014-12-01

    The model, including shielding effects of high-Z dust grain ablation in tokamak edge plasma, is presented. In a contrast to shielding models developed for pellets ablation in a hot plasma core, this model deals with the dust grain ablation in relatively cold edge plasma. Using some simplifications, a closed set of equations determining the grain ablation rate Γ is derived and analyzed both analytically and numerically. The scaling law for Γ versus grain radius and ambient plasma parameters is obtained and confirmed by the results of numerical solutions. The results obtained are compared with both dust grain models containing no shielding effects and the pellet ablation models.

  20. A multiphase model for pulsed ns-laser ablation of copper in an ambient gas

    SciTech Connect

    Autrique, D.; Chen, Z.; Alexiades, V.; Bogaerts, A.; Rethfeld, B.

    2012-07-30

    Laser ablation in an ambient gas is nowadays used in a growing number of applications, such as chemical analysis and pulsed laser deposition. Despite the many applications, the technique is still poorly understood. Therefore models describing the material evolution in time during short pulse laser irradiation can be helpful to unravel the puzzle and finally result in the optimization of the related applications. In the present work, a copper target is immersed in helium, initially set at atmospheric pressure and room temperature. Calculations are performed for a Gaussian-shaped laser pulse with a wavelength of 532 nm, full width at half maximum of 6 ns, and laser fluences up to 10 J/cm{sup 2}. In order to describe the transient behaviour in and above the copper target, hydrodynamic equations are solved. An internal energy method accounting for pressure relaxation is applied for the description of the target. In the plume domain a set of conservation equations is solved, assuming local thermodynamic equilibrium. Calculated crater depths and transmission profiles are compared with experimental results and similar trends are found. Our calculations indicate that for the laser fluence regime under study, explosive boiling could play a fundamental role in the plasma formation of metals under ns-pulsed laser irradiation.

  1. Dependence of gold nanoparticle production on pulse duration by laser ablation in liquid media

    NASA Astrophysics Data System (ADS)

    Riabinina, Daria; Chaker, Mohamed; Margot, Joëlle

    2012-04-01

    The dependence on laser fluence and laser pulse duration of size, size distribution and concentration of gold nanoparticles synthesized by laser ablation in liquid media was investigated. It was demonstrated that increasing laser energy from 1 to 5 mJ/pulse enhances the ablation rate by a factor of 100. The behavior of the ablation rate, hence of the nanoparticle concentration, as a function of pulse duration (varied from 40 fs to 200 ps) was found to strongly differ from that in air, which can be explained by photoionization and important losses of laser energy in the femtosecond regime. The optimal pulse duration for maximum ablation rate in liquid media was found to be equal to 2 ps.

  2. Effect of nanosecond pulse laser ablation on the surface morphology of Zr-based metallic glass

    NASA Astrophysics Data System (ADS)

    Zhu, Yunhu; Fu, Jie; Zheng, Chao; Ji, Zhong

    2016-09-01

    In this study, we investigated the ripple patterns formation on the surface of Zr41.2Ti13.8Cu12.5Ni10Be22.5 (vit1) bulk metallic glass using a nanosecond pulse laser ablation in air with a wavelength of 1064 nm. The strong thermal ablation phenomenon could be observed on vit1 BMG surface at laser energy of 200 mJ as a result of the adhibition of confining overlay. Many periodic ripples had formed on the edge of the ablated area at laser energy of 400 mJ because of the high intensity pulsed laser beam. The underlying mechanism of the periodic ripples formation could be explained by the K-H hydrodynamic instability theory. It had been shown that laser ablation with 600 mJ and 200 pulses results in the formation of many micro-cracks on the ablated area. Further analysis showed that the spatial occupation of the laser ablated area and the spacing between two adjacent ripples increased as the laser energy and the number of incident laser pulses increasing. The surface ripples feature on the edge of ablated area became more obvious with increasing laser pulses, but it was not correlated closely with the laser energies variation.

  3. Development of double-pulse lasers ablation system for generating gold ion source under applying an electric field

    NASA Astrophysics Data System (ADS)

    Khalil, A. A. I.

    2015-12-01

    Double-pulse lasers ablation (DPLA) technique was developed to generate gold (Au) ion source and produce high current under applying an electric potential in an argon ambient gas environment. Two Q-switched Nd:YAG lasers operating at 1064 and 266 nm wavelengths are combined in an unconventional orthogonal (crossed-beam) double-pulse configuration with 45° angle to focus on a gold target along with a spectrometer for spectral analysis of gold plasma. The properties of gold plasma produced under double-pulse lasers excitation were studied. The velocity distribution function (VDF) of the emitted plasma was studied using a dedicated Faraday-cup ion probe (FCIP) under argon gas discharge. The experimental parameters were optimized to attain the best signal to noise (S/N) ratio. The results depicted that the VDF and current signals depend on the discharge applied voltage, laser intensity, laser wavelength and ambient argon gas pressure. A seven-fold increases in the current signal by increasing the discharge applied voltage and ion velocity under applying double-pulse lasers field. The plasma parameters (electron temperature and density) were also studied and their dependence on the delay (times between the excitation laser pulse and the opening of camera shutter) was investigated as well. This study could provide significant reference data for the optimization and design of DPLA systems engaged in laser induced plasma deposition thin films and facing components diagnostics.

  4. Image guided thermal ablation of tumors increases the plasma level of IL-6 and IL-10

    PubMed Central

    Erinjeri, Joseph P; Thomas, Contessa T; Samoila, Alaiksandra; Fleisher, Martin; Gonen, Mithat; Sofocleous, Constantinos T.; Thornton, Raymond H; Siegelbaum, Robert H.; Covey, Anne M.; Brody, Lynn A.; Alago, William; Maybody, Majid; Brown, Karen T.; Getrajdman, George; Solomon, Stephen B.

    2014-01-01

    PURPOSE To identify changes in plasma cytokine levels following image-guided thermal ablation of human tumors and to identify the factors that independently predict changes in plasma cytokine levels. MATERIALS AND METHODS Whole blood samples were collected from 36 patients at 3 time points: pre-ablation, post-ablation (within 48 hours), and in follow-up (1–5 weeks after ablation). Plasma levels of IL-1a, IL-2, IL-6, IL-10 and TNFa were measured using a multiplex immunoassay. Univariate and multivariate analyses were performed using cytokine level as the dependent variable and sample collection, time, age, sex, primary diagnosis, metastatic status, ablation site, and ablation type as the independent variables. RESULTS There was a significant increase in the plasma level of IL-6 post-ablation when compared to pre-ablation (9.6+/−31 fold, p<0.002). IL-10 also showed a significant increase postablation (1.9 +/−2.8 fold, p<0.02). Plasma levels of IL-1a, IL-2, and TNFa were not significantly changed after ablation. Cryoablation resulted in the largest change in IL-6 level (>54 fold), while radiofrequency and microwave ablation showed 3.6 and 3.4-fold changes, respectively. Ablation of melanomas showed the largest change in IL-6 48 hours after ablation (92×), followed by ablation of kidney (26×), liver (8×), and lung (6×) cancers. Multivariate analysis revealed that ablation type (p<0.0003), and primary diagnosis (p<0.03) were independent predictors of changes to IL-6 following ablation. Age was the only independent predictor of IL-10 levels following ablation (p<0.019). CONCLUSION Image guided thermal ablation of tumors increases the plasma level of IL-6 and IL-10, without increasing the plasma level of IL-1a, IL-2, or TNFa. PMID:23582441

  5. Synthesis of cubic ruthenium nitride by reactive pulsed laser ablation

    NASA Astrophysics Data System (ADS)

    Moreno-Armenta, M. G.; Diaz, J.; Martinez-Ruiz, A.; Soto, G.

    2007-10-01

    The recent synthesis of platinum nitride opens the possibility of novel platinum-group metal nitrides to exist. In this work we report the synthesis of ruthenium nitride by reactive pulsed laser ablation. Several plausible structures have been evaluated by ab initio calculations using the full potential linearized augmented plane wave method, in order to investigate the ruthenium nitride structural and electronic properties. In fact, the predicted symmetry of stoichiometric RuN matches the experimental diffraction data. RuN crystallizes with NaCl-type structure at room temperature with cell-parameter somewhat larger than predicted by calculations. However we found a marginal chemical strength in these nitrides. The material is destroyed by mild acid and basic solutions. Under annealing RuN decomposes abruptly for temperatures beyond 100 °C. Since the thermal stability correlates directly with the mechanical properties our finding cast doubts than the latter transition metal nitrides can be ultra-hard materials at ambient conditions.

  6. Ultraviolet versus infrared: Effects of ablation laser wavelength on the expansion of laser-induced plasma into one-atmosphere argon gas

    NASA Astrophysics Data System (ADS)

    Ma, Qianli; Motto-Ros, Vincent; Laye, Fabrice; Yu, Jin; Lei, Wenqi; Bai, Xueshi; Zheng, Lijuan; Zeng, Heping

    2012-03-01

    Laser-induced plasma from an aluminum target in one-atmosphere argon background has been investigated with ablation using nanosecond ultraviolet (UV: 355 nm) or infrared (IR: 1064 nm) laser pulses. Time- and space-resolved emission spectroscopy was used as a diagnostics tool to have access to the plasma parameters during its propagation into the background, such as optical emission intensity, electron density, and temperature. The specific feature of nanosecond laser ablation is that the pulse duration is significantly longer than the initiation time of the plasma. Laser-supported absorption wave due to post-ablation absorption of the laser radiation by the vapor plume and the shocked background gas plays a dominant role in the propagation and subsequently the behavior of the plasma. We demonstrate that the difference in absorption rate between UV and IR radiations leads to different propagation behaviors of the plasma produced with these radiations. The consequence is that higher electron density and temperature are observed for UV ablation. While for IR ablation, the plasma is found with lower electron density and temperature in a larger and more homogenous axial profile. The difference is also that for UV ablation, the background gas is principally evacuated by the expansion of the vapor plume as predicted by the standard piston model. While for IR ablation, the background gas is effectively mixed to the ejected vapor at least hundreds of nanoseconds after the initiation of the plasma. Our observations suggest a description by laser-supported combustion wave for the propagation of the plasma produced by UV laser, while that by laser-supported detonation wave for the propagation of the plasma produced by IR laser. Finally, practical consequences of specific expansion behavior for UV or IR ablation are discussed in terms of analytical performance promised by corresponding plasmas for application with laser-induced breakdown spectroscopy.

  7. A Langmuir Probe Diagnostic for Use in Inhomogeneous, Time-Varying Plasmas Produced by High-Energy Laser Ablation

    SciTech Connect

    Patterson, J R; Emig, J A; Fournier, K B; Jenkins, P P; Trautz, K M; Seiler, S W; Davis, J F

    2012-05-01

    Langmuir probes (LP) are used extensively to characterize plasma environments produced by radio frequency, pulsed plasma thrusters, and laser ablation. We discuss here the development of a LP diagnostic to examine high-density, high-temperature inhomogeneous plasmas such as those that can be created at the University of Rochester's Laboratory for Laser Energetics OMEGA facility. We have configured our diagnostic to examine the velocity of the plasma expanding from the target. We observe velocities of approximately 16-17 cm/{micro}s, with individual LP currents displaying complex structures, perhaps due to the multiple atomic species and ionization states that exist.

  8. Laser ablation of single-crystalline silicon by radiation of pulsed frequency-selective fiber laser

    NASA Astrophysics Data System (ADS)

    Veiko, V. P.; Skvortsov, A. M.; Huynh, C. T.; Petrov, A. A.

    2015-07-01

    We have studied the process of destruction of the surface of a single-crystalline silicon wafer scanned by the beam of a pulsed ytterbium-doped fiber laser radiation with a wavelength of λ = 1062 nm. It is established that the laser ablation can proceed without melting of silicon and the formation of a plasma plume. Under certain parameters of the process (radiation power, beam scan velocity, and beam overlap density), pronounced oxidation of silicon microparticles with the formation of a characteristic loose layer of fine powdered silicon dioxide has been observed for the first time. The range of lasing and beam scanning regimes in which the growth of SiO2 layer takes place is determined.

  9. Laser ablated copper plasmas in liquid and gas ambient

    SciTech Connect

    Kumar, Bhupesh; Thareja, Raj K.

    2013-05-15

    The dynamics of copper ablated plasma plumes generated using laser ablation of copper targets in both liquid (de-ionized water) and gas (air) ambients is reported. Using time and space resolved visible emission spectroscopy (450-650 nm), the plasma plumes parameters are investigated. The electron density (n{sub e}) determined using Stark broadening of the Cu I (3d{sup 10}4d{sup 1} {sup 2}D{sub 3/2}-3d{sup 10}4p{sup 1} {sup 2}P{sub 3/2} at 521.8 nm) line is estimated and compared for both plasma plumes. The electron temperature (T{sub e}) was estimated using the relative line emission intensities of the neutral copper transitions. Field emission scanning electron microscopy and energy dispersive x-ray spectral analysis of the ablated copper surface indicated abundance of spherical nanoparticles in liquid while those in air are amalgamates of irregular shapes. The nanoparticles suspended in the confining liquid form aggregates and exhibit a surface plasmon resonance at ∼590 nm.

  10. Inductively Coupled Plasma: Fundamental Particle Investigations with Laser Ablation and Applications in Magnetic Sector Mass Spectrometry

    SciTech Connect

    Saetveit, Nathan Joe

    2008-01-01

    Particle size effects and elemental fractionation in laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) are investigated with nanosecond and femtosecond laser ablation, differential mobility analysis, and magnetic sector ICP-MS. Laser pulse width was found to have a significant influence on the LA particle size distribution and the elemental composition of the aerosol and thus fractionation. Emission from individual particles from solution nebulization, glass, and a pressed powder pellet are observed with high speed digital photography. The presence of intact particles in an ICP is shown to be a likely source of fractionation. A technique for the online detection of stimulated elemental release from neural tissue using magnetic sector ICP-MS is described. Detection limits of 1 μg L-1 or better were found for P, Mn, Fe, Cu, and Zn in a 60 μL injection in a physiological saline matrix.

  11. Laser cutting of carbon fiber reinforced plastics (CFRP) by UV pulsed laser ablation

    NASA Astrophysics Data System (ADS)

    Niino, Hiroyuki; Kurosaki, Ryozo

    2011-03-01

    In this paper, we report on a micro-cutting of carbon fiber reinforced plastics (CFRP) by nanosecond-pulsed laser ablation with a diode-pumped solid state UV laser (DPSS UV laser, λ= 355nm). A well-defined cutting of CFRP which were free of debris and thermal-damages around the grooves, were performed by the laser ablation with a multiple-scanpass irradiation method. CFRP is a high strength composite material with a lightweight, and is increasingly being used various applications. UV pulsed laser ablation is suitable for laser cutting process of CFRP materials, which drastically reduces a thermal damage at cut regions.

  12. Simulation of laser interaction with ablative plasma and hydrodynamic behavior of laser supported plasma

    NASA Astrophysics Data System (ADS)

    Tong, Huifeng; Yuan, Hong; Tang, Zhiping

    2013-01-01

    When an intense laser beam irradiates on a solid target, ambient air ionizes and becomes plasma, while part of the target rises in temperature, melts, vaporizes, ionizes, and yet becomes plasma. A general Godunov finite difference scheme WENO (Weighted Essentially Non-Oscillatory Scheme) with fifth-order accuracy is used to simulate 2-dimensional axis symmetrical laser-supported plasma flow field in the process of laser ablation. The model of the calculation of ionization degree of plasma and the interaction between laser beam and plasma are considered in the simulation. The numerical simulations obtain the profiles of temperature, density, and velocity at different times which show the evolvement of the ablative plasma. The simulated results show that the laser energy is strongly absorbed by plasma on target surface and that the velocity of laser supported detonation (LSD) wave is half of the ideal LSD value derived from Chapman-Jouguet detonation theory.

  13. Simulation of laser interaction with ablative plasma and hydrodynamic behavior of laser supported plasma

    SciTech Connect

    Tong Huifeng; Yuan Hong; Tang Zhiping

    2013-01-28

    When an intense laser beam irradiates on a solid target, ambient air ionizes and becomes plasma, while part of the target rises in temperature, melts, vaporizes, ionizes, and yet becomes plasma. A general Godunov finite difference scheme WENO (Weighted Essentially Non-Oscillatory Scheme) with fifth-order accuracy is used to simulate 2-dimensional axis symmetrical laser-supported plasma flow field in the process of laser ablation. The model of the calculation of ionization degree of plasma and the interaction between laser beam and plasma are considered in the simulation. The numerical simulations obtain the profiles of temperature, density, and velocity at different times which show the evolvement of the ablative plasma. The simulated results show that the laser energy is strongly absorbed by plasma on target surface and that the velocity of laser supported detonation (LSD) wave is half of the ideal LSD value derived from Chapman-Jouguet detonation theory.

  14. Plasma Emission Spectra of Opuntia Nopalea Obtained with Microsecond Laser Pulses

    SciTech Connect

    Ponce, L.; Flores, T.; Arronte, A.; Flores, A.

    2008-04-15

    Laser-induced Plasma Spectroscopy was performed during the spines ablation of Opuntia by using Nd:YAG microsecond laser pulses. The results show strong absorption in Glochids that causes the intense electronic noise on the spectra. This process is consider suitable for practical elimination of spines in alimentary products like opuntia.

  15. Experimental and Computational Studies of High Energy Density Plasma Streams Ablated from Fine Wires

    SciTech Connect

    Greenly, John B.; Seyler, Charles

    2014-03-30

    Experimental and computational studies of high energy density plasma streams ablated from fine wires. Laboratory of Plasma Studies, School of Electrical and Computer Engineering, Cornell University. Principal Investigators: Dr. John B. Greenly and Dr. Charles E. Seyler. This report summarizes progress during the final year of this project to study the physics of high energy density (HED) plasma streams of 10^17-10^20/cm3 density and high velocity (~100-500 km/s). Such streams are produced from 5-250 micrometer diameter wires heated and ionized by a 1 MA, 250 ns current pulse on the COBRA pulsed power facility at Cornell University. Plasma is ablated from the wires and is driven away to high velocity by unbalanced JxB force. A wire, or an array of wires, can persist as an essentially stationary, continuous source of this streaming plasma for >200 ns, even with driving magnetic fields of many Tesla and peak current densities in the plasma of many MA/cm2. At the heart of the ablation stream generation is the continuous transport of mass from the relatively cold, near-solid-density wire "core" into current-carrying plasma within 1 mm of the wire, followed by the magnetic acceleration of that plasma and its trapped flux to form a directed stream. In the first two years of this program, an advancing understanding of ablation physics led to the discovery of several novel wire ablation experimental regimes. In the final year, one of these new HED plasma regimes has been studied in quantitative detail. This regime studies highly reproducible magnetic reconnection in strongly radiating plasma with supersonic and superalfvenic flow, and shock structures in the outflow. The key discovery is that very heavy wires, e.g. 250 micrometer diameter Al or 150 micrometer Cu, behave in a qualitatively different way than the lighter wires typically used in wire-array Z-pinches. Such wires can be configured to produce a static magnetic X-point null geometry that stores magnetic and

  16. Comparing ablation induced by fs, ps, and ns XUV-laser pulses

    NASA Astrophysics Data System (ADS)

    Bittner, Michal; Juha, Libor; Chvostova, Dagmar; Letal, Vit; Krasa, Josef; Otcenasek, Zdenek; Kozlova, Michaela; Polan, Jiri; Praeg, Ansgar R.; Rus, Bedrich; Stupka, Michal; Krzywinski, Jacek; Andrejczuk, Andrzej; Pelka, Jerzy B.; Sobierajski, Ryszard; Feldhaus, Josef; Boody, Frederick P.; Grisham, Michael E.; Vaschenko, Georgiy O.; Menoni, Carmen S.; Rocca, Jorge J.

    2004-09-01

    Ablation thresholds, etch rates, and quality of ablated structures often differ dramatically if a conventional, UV-Vis-IR laser delivers radiation energy onto a material surface in a short (nanosecond) or ultra-short (picosecond/femtosecond) pulses. Various short-wavelength (λ < 100 nm) lasers emitting pulses with durations ranging from ~ 10 fs to ~ 1 ns have recently been put into a routine operation. This makes possible to investigate how the ablation characteristics depends on the pulse duration in the XUV spectral region. 1.2-ns pulses of 46.9-nm radiation delivered from a capillary-discharge Ne-like Ar laser, focused by a spherical Sc/Si multilayer-coated mirror were used for an ablation of organic polymers and silicon. Various materials were irradiated with an ellipsoidal-mirror-focused XUV radiation (λ = 86 nm, τ = 30-100 fs) generated by the free-electron laser (FEL) operated at the TESLA Test Facility (TTF1 FEL) in Hamburg. The beam of the Ne-like Zn XUV laser (λ = 21.2 nm, τ < 100 ps) driven by the Prague Asterix Laser System (PALS) was also successfully focused by a spherical Si/Mo multilayer-coated mirror to ablate various materials. Based on the results of the experiment the etch rates for three different pulse durations are compared using the XUV-ABLATOR code to compensate for the wavelength difference. Comparing the values of etch rates calculated for short pulses with the measured ones for ultrashort pulses we may study the influence of pulse duration on the XUV ablation efficiency.

  17. Electron dynamics and prompt ablation of aluminum surface excited by intense femtosecond laser pulse

    NASA Astrophysics Data System (ADS)

    Ionin, A. A.; Kudryashov, S. I.; Makarov, S. V.; Seleznev, L. V.; Sinitsyn, D. V.

    2014-12-01

    Thin aluminum film homogeneously heated by intense IR femtosecond laser pulses exhibits on the excitation timescale consequent fluence-dependent rise and drop of the IR-pump self-reflectivity, followed by its final saturation at higher fluences F > 0.3 J/cm2. This prompt optical dynamics correlates with the initial monotonic increase in the accompanying laser-induced electron emission, which is succeeded by its non-linear (three-photon) increase for F > 0.3 J/cm2. The underlying electronic dynamics is related to the initial saturation of IR resonant interband transitions in this material, followed by its strong instantaneous electronic heating via intraband transitions during the pump pulse resulting in thermionic emission. Above the threshold fluence of 0.3 J/cm2, the surface electronic heating is balanced during the pump pulse by simultaneous cooling via intense plasma removal (prompt ablation). The relationship between the deposited volume energy density in the film and its prompt electronic temperature derived from the self-reflection measurements using a Drude model, demonstrates a kind of electron "liquid-vapor" phase transition, driven by strong cubic optical non-linearity of the photo-excited aluminum.

  18. Stark broadening measurements in plasmas produced by laser ablation of hydrogen containing compounds

    NASA Astrophysics Data System (ADS)

    Burger, Miloš; Hermann, Jörg

    2016-08-01

    We present a method for the measurement of Stark broadening parameters of atomic and ionic spectral lines based on laser ablation of hydrogen containing compounds. Therefore, plume emission spectra, recorded with an echelle spectrometer coupled to a gated detector, were compared to the spectral radiance of a plasma in local thermal equilibrium. Producing material ablation with ultraviolet nanosecond laser pulses in argon at near atmospheric pressure, the recordings take advantage of the spatially uniform distributions of electron density and temperature within the ablated vapor. By changing the delay between laser pulse and detector gate, the electron density could be varied by more than two orders of magnitude while the temperature was altered in the range from 6,000 to 14,000 K. The Stark broadening parameters of transitions were derived from their simultaneous observation with the hydrogen Balmer alpha line. In addition, assuming a linear increase of Stark widths and shifts with electron density for non-hydrogenic lines, our measurements indicate a change of the Stark broadening-dependence of Hα over the considered electron density range. The presented results obtained for hydrated calcium sulfate (CaSO4ṡ2H2O) can be extended to any kind of hydrogen containing compounds.

  19. Dynamics of a pulsed laser generated tin plasma expanding in an oxygen atmosphere

    NASA Astrophysics Data System (ADS)

    Barreca, F.; Fazio, E.; Neri, F.; Barletta, E.; Trusso, S.; Fazio, B.

    2005-10-01

    Semiconducting tin oxide can be successfully deposited by means of the laser ablation technique. In particular by ablating metallic tin in a controlled oxygen atmosphere, thin films of SnOx have been deposited. The partial oxygen pressure at which the films are deposited strongly influences both the stoichiometry and the structural properties of the films. In this work, we present a study of the expansion dynamics of the plasma generated by ablating a tin target by means of a pulsed laser using time and space resolved optical emission spectroscopy and fast photography imaging of the expanding plasma. Both Sn I and Sn II optical emission lines have been observed from the time-integrated spectroscopy. Time resolved-measurements revealed the dynamics of the expanding plasma in the ambient oxygen atmosphere. Stoichiometry of the films has been determined by means of X-ray photoelectron spectroscopy and correlated to the expansion dynamics of the plasma.

  20. Ablation plasma transport using multicusp magnetic field for laser ion source

    NASA Astrophysics Data System (ADS)

    Takahashi, K.; Umezawa, M.; Uchino, T.; Ikegami, K.; Sasaki, T.; Kikuchi, T.; Harada, N.

    2016-05-01

    We propose a plasma guiding method using multicusp magnetic field to transport the ablation plasma keeping the density for developing laser ion sources. To investigate the effect of guiding using the magnetic field on the ablation plasma, we demonstrated the transport of the laser ablation plasma in the multicusp magnetic field. The magnetic field was formed with eight permanent magnets and arranged to limit the plasma expansion in the radial direction. We investigated the variation of the plasma ion current density and charge distribution during transport in the magnetic field. The results indicate that the plasma is confined in the radial direction during the transport in the multicusp magnetic field.

  1. INFN - P.L.A.I.A. PROJECT (Plasma Laser Ablation for Ion Acceleration)

    NASA Astrophysics Data System (ADS)

    Torrisi, L.; Gammino, S.; Andò, L.; Ciavola, G.; Mezzasalma, A. M.; Nassisi, V.; Wolowski, J.; Parys, P.; Laska, L.; Krasa, J.; Boody, F. P.

    2004-10-01

    The INFN-Gr.V PLAIA (Plasma Laser Ablation for Ion Acceleration) Project is presented and discussed. The project is developing at LNS of Catania, Messina and Lecce Laboratories as Italian centers of research and it see as European partners the PALS Laboratory of Prague and the group of researchers coordinated by Prof. Wolowsky from IPPLM of Warsaw. PLAIA concerns the study of pulsed plasma produced by pulsed lasers and some special applications of this physics to the new generation of ion sources. Different lasers are employed at LNS of Catania, LEA of Lecce and PALS of Prague. Their fluences range from about 10 J/cm2 for the excimer lasers of LEA up to about 100 kj/cm2 for the iodine laser of PALS. The Nd:Yag laser of LNS, operating at 1064 nm, 9 ns pulse width and 900 mJ maximum pulse energy shows peculiar properties, specially if it is employed at 30 Hz repetition rate, at which it may produce stabile current of ions ejected from a dense plasma. Such laser has the optimum compromise between power density and repetition rate to be used as injector of ions in ECR sources or as source of a new generation of ion implanters which can be employed to accelerate multi-energetic ion beams useful to treat the surface of different materials. Results and projects are discussed in detail.

  2. Dynamic absorption and scattering of water and hydrogel during high-repetition-rate (>100 MHz) burst-mode ultrafast-pulse laser ablation

    PubMed Central

    Qian, Zuoming; Covarrubias, Andrés; Grindal, Alexander W.; Akens, Margarete K.; Lilge, Lothar; Marjoribanks, Robin S.

    2016-01-01

    High-repetition-rate burst-mode ultrafast-laser ablation and disruption of biological tissues depends on interaction of each pulse with the sample, but under those particular conditions which persist from previous pulses. This work characterizes and compares the dynamics of absorption and scattering of a 133-MHz repetition-rate, burst-mode ultrafast-pulse laser, in agar hydrogel targets and distilled water. The differences in energy partition are quantified, pulse-by-pulse, using a time-resolving integrating-sphere-based device. These measurements reveal that high-repetition-rate burst-mode ultrafast-laser ablation is a highly dynamical process affected by the persistence of ionization, dissipation of plasma plume, neutral material flow, tissue tensile strength, and the hydrodynamic oscillation of cavitation bubbles. PMID:27375948

  3. Dynamic absorption and scattering of water and hydrogel during high-repetition-rate (>100 MHz) burst-mode ultrafast-pulse laser ablation.

    PubMed

    Qian, Zuoming; Covarrubias, Andrés; Grindal, Alexander W; Akens, Margarete K; Lilge, Lothar; Marjoribanks, Robin S

    2016-06-01

    High-repetition-rate burst-mode ultrafast-laser ablation and disruption of biological tissues depends on interaction of each pulse with the sample, but under those particular conditions which persist from previous pulses. This work characterizes and compares the dynamics of absorption and scattering of a 133-MHz repetition-rate, burst-mode ultrafast-pulse laser, in agar hydrogel targets and distilled water. The differences in energy partition are quantified, pulse-by-pulse, using a time-resolving integrating-sphere-based device. These measurements reveal that high-repetition-rate burst-mode ultrafast-laser ablation is a highly dynamical process affected by the persistence of ionization, dissipation of plasma plume, neutral material flow, tissue tensile strength, and the hydrodynamic oscillation of cavitation bubbles. PMID:27375948

  4. Influence of effective number of pulses on the morphological structure of teeth and bovine femur after femtosecond laser ablation

    NASA Astrophysics Data System (ADS)

    Nicolodelli, Gustavo; de Fátima Zanirato Lizarelli, Rosane; Salvador Bagnato, Vanderlei

    2012-04-01

    Femtosecond lasers have been widely used in laser surgery as an instrument for contact-free tissue removal of hard dental, restorative materials, and osseous tissues, complementing conventional drilling or cutting tools. In order to obtain a laser system that provides an ablation efficiency comparable to mechanical instruments, the laser pulse rate must be maximal without causing thermal damage. The aim of this study was to compare the different morphological characteristics of the hard tissue after exposure to lasers operating in the femtosecond pulse regime. Two different kinds of samples were irradiated: dentin from human extracted teeth and bovine femur samples. Different procedures were applied, while paying special care to preserving the structures. The incubation factor S was calculated to be 0.788+/-0.004 for the bovine femur bone. These results indicate that the incubation effect is still substantial during the femtosecond laser ablation of hard tissues. The plasma-induced ablation has reduced side effects, i.e., we observe less thermal and mechanical damage when using a superficial femtosecond laser irradiation close to the threshold conditions. In the femtosecond regime, the morphology characteristics of the cavity were strongly influenced by the change of the effective number of pulses.

  5. Influence of effective number of pulses on the morphological structure of teeth and bovine femur after femtosecond laser ablation.

    PubMed

    Nicolodelli, Gustavo; Lizarelli, Rosane de Fátima Zanirato; Bagnato, Vanderlei Salvador

    2012-04-01

    Femtosecond lasers have been widely used in laser surgery as an instrument for contact-free tissue removal of hard dental, restorative materials, and osseous tissues, complementing conventional drilling or cutting tools. In order to obtain a laser system that provides an ablation efficiency comparable to mechanical instruments, the laser pulse rate must be maximal without causing thermal damage. The aim of this study was to compare the different morphological characteristics of the hard tissue after exposure to lasers operating in the femtosecond pulse regime. Two different kinds of samples were irradiated: dentin from human extracted teeth and bovine femur samples. Different procedures were applied, while paying special care to preserving the structures. The incubation factor S was calculated to be 0.788±0.004 for the bovine femur bone. These results indicate that the incubation effect is still substantial during the femtosecond laser ablation of hard tissues. The plasma-induced ablation has reduced side effects, i.e., we observe less thermal and mechanical damage when using a superficial femtosecond laser irradiation close to the threshold conditions. In the femtosecond regime, the morphology characteristics of the cavity were strongly influenced by the change of the effective number of pulses. PMID:22559697

  6. Morphological effects of nanosecond- and femtosecond-pulsed laser ablation on human middle ear ossicles

    NASA Astrophysics Data System (ADS)

    Ilgner, Justus F.; Wehner, Martin; Lorenzen, Johann; Bovi, Manfred; Westhofen, Martin

    2004-07-01

    Introduction: Since the early 1980's, a considerable number of different laser systems have been introduced into reconstructive middle ear surgery. Depending on the ablation mode, however, pressure transients or thermal load to inner ear structures continue to be subject to discussion. Material and methods: We examined single spot ablations by a nanosecond-pulsed, frequency-tripled Nd:YAG-Laser (355 nm, beam diameter 10 μm, pulse rate 2 kHz, power 250 mW) on isolated human mallei. In a second set-up, a similar system (355 nm, beam diameter 20 μm, pulse rate 10 kHz, power 160-1500 mW) was coupled to a scanner to examine the morphology of bone surface ablation over an area of 1mm2. A third set-up employed a femtosecond-pulsed CrLiSAF-Oscillator (850 nm, pulse duration 100 fs, pulse energy 40μJ, beam diameter 36 μm, pulse rate 1 kHz) to compare these results with the former and with those obtained from a commercially available Er:YAG laser for ear surgery (Zeiss ORL E, 2940 nm, single pulse, energy 10-25 mJ). Results: In set-up 1 and 2, thermal effects in terms of marginal carbonization were visible in all single spot ablations of 1 s and longer. With ablations of 0.5 seconds, precise cutting margins with preservation of surrounding tissue could be observed. Cooling with saline solution resulted in no carbonization at 1500 mW and a scan speed of 500 mm/s. Set-up 3 equally showed no carbonization, although scanning times were longer and ablation less pronounced. Conclusion: Ultrashort pulsed laser systems could potentially aid further refinement of reconstructive microsurgery of the middle ear.

  7. Ablation par laser pulse de revetements antierosion pour le domaine aeronautique

    NASA Astrophysics Data System (ADS)

    Ragusich, Alexis

    Erosion resistant coatings (ERCs) are frequently used to protect aircraft engine components against erosion, and therefore, to extend their lifetime and reduce maintenance cost. However, after many hours in service, certain areas of the coating will begin to deteriorate. Given that such components are generally very costly, it is desirable to replace only the coating instead of the part itself. This research is part of the MANU 4 project, supported by CRIAQ and NSERC, which aims to study the feasibility of stripping an erosion-resistant coating deposited on a titanium-based alloy with three different techniques: wet chemical etching, plasma etching and pulse laser ablation. This thesis focuses more specifically on the etching with a pulsed laser of a 20-mum thick TiAlN ERC deposited on a Ti-6Al-4V substrate. This work compares the suitability of two pulsed lasers: a femtosecond Ti:Sapphire laser emitting at 800 nm and a nanosecond KrF excimer laser centred at 248 nm. These two lasers were chosen since they are frequently used for micromachining applications and allow us to study the effect of the wavelength and pulse duration. Preliminary findings have allowed us to identify four most critical variables that influence the etch rate and the surface roughness: (i) beam size, (ii) laser power, (iii) stage speed, and (iv) step distance between scanned lines. For each laser, optimal etching conditions were obtained by varying a single parameter at a time. Final results show that the higher energy per pulse offered by the excimer laser allows one to increase by one order of magnitude the etch rate, but almost doubles, from 1 mum to 1.8 mum, the surface roughness, in comparison with results obtained with the Ti:Sapphire laser. Compared with other techniques, pulse laser ablation has the potential to offer very high selectivity. In this regard, plume emission spectroscopy was studied as an in situ technique to monitor the etching progress and determine the precise moment

  8. Electrosensitization assists cell ablation by nanosecond pulsed electric field in 3D cultures

    PubMed Central

    Muratori, Claudia; Pakhomov, Andrei G.; Xiao, Shu; Pakhomova, Olga N.

    2016-01-01

    Previous studies reported a delayed increase of sensitivity to electroporation (termed “electrosensitization”) in mammalian cells that had been subjected to electroporation. Electrosensitization facilitated membrane permeabilization and reduced survival in cell suspensions when the electric pulse treatments were split in fractions. The present study was aimed to visualize the effect of sensitization and establish its utility for cell ablation. We used KLN 205 squamous carcinoma cells embedded in an agarose gel and cell spheroids in Matrigel. A local ablation was created by a train of 200 to 600 of 300-ns pulses (50 Hz, 300–600 V) delivered by a two-needle probe with 1-mm inter-electrode distance. In order to facilitate ablation by engaging electrosensitization, the train was split in two identical fractions applied with a 2- to 480-s interval. At 400–600 V (2.9–4.3 kV/cm), the split-dose treatments increased the ablation volume and cell death up to 2–3-fold compared to single-train treatments. Under the conditions tested, the maximum enhancement of ablation was achieved when two fractions were separated by 100 s. The results suggest that engaging electrosensitization may assist in vivo cancer ablation by reducing the voltage or number of pulses required, or by enabling larger inter-electrode distances without losing the ablation efficiency. PMID:26987779

  9. Femtosecond laser ablation of sapphire on different crystallographic facet planes by single and multiple laser pulses irradiation

    NASA Astrophysics Data System (ADS)

    Qi, Litao; Nishii, Kazuhiro; Yasui, Motohiro; Aoki, Hikoharu; Namba, Yoshiharu

    2010-10-01

    Ablation of sapphire on different crystallographic facet planes by single and multiple laser pulses irradiation was carried out with a femtosecond pulsed laser operating at a wavelength of 780 nm and a pulse width of 164 fs. The quality and morphology of the laser ablated sapphire surface were evaluated by scanning electron microscopy and atomic force microscopy. For single laser pulse irradiation, two ablation phases were observed, which have a strong dependency on the pulse energy. The volume of the ablated craters kept an approximately linear relationship with the pulse energy. The threshold fluences of the two ablation phases on different crystallographic facet planes were calculated from the relationship between the squared diameter of the craters and pulse energy. With multiple laser pulses irradiation, craters free of cracks were obtained in the 'gentle' ablation phase. The threshold fluence for N laser pulses was calculated and found to decrease inversely to the number of laser pulses irradiating on the substrate surface due to incubation effect. The depth of the craters increased with the number of laser pulses until reaching a saturation value. The mechanism of femtosecond laser ablation of sapphire in two ablation phases was discussed and identified as either phase explosion, Coulomb explosion or particle vaporization. The choice of crystallographic facet plane has little effect on the process of femtosecond laser ablation of sapphire when compared with the parameters of the femtosecond laser pulses, such as pulse energy and number of laser pulses. In the 'gentle' ablation phase, laser-induced periodic surface structures (LIPSS) with a spatial period of 340 nm were obtained and the mechanism of the LIPSS formation is discussed. There is a potential application of the femtosecond laser ablation to the fabrication of sapphire-based devices.

  10. Spectroscopic measurements of ablation plasma generated with laser-driven intense extreme ultraviolet (EUV) light

    NASA Astrophysics Data System (ADS)

    Tanaka, N.; Hane, K.; Shikata, H.; Masuda, M.; Nagatomi, K.; Sunahara, A.; Yoshida, M.; Fujioka, S.; Nishimura, H.

    2016-03-01

    Material ablation by a focused Extreme ultraviolet (EUV) light is studied by comparing expanding ion properties and plasma parameters with laser ablation. The kinetic energy distributions of expanding ions from EUV and laser ablation showed different spectra implying different geometries of plasma expansion. The calculation results of plasma parameters showed that EUV energy is mostly deposited in high electron density region close to the solid density, while laser energy is deposited in low energy density region. Plasma parameters experimentally obtained from visible spectra did not show noticeable difference between EUV and laser ablation due to the corresponding low cut off density.

  11. UV-laser Ablation of Fibre Reinforced Composites with Ns-Pulses

    NASA Astrophysics Data System (ADS)

    Dittmar, H.; Gäbler, F.; Stute, U.

    Within this work the ablation behaviour of both carbon and glass fibre reinforced epoxy resin was assessed when ablated by a nanosecond-pulsed laser source emitting radiation in the ultra-violet spectrum. The investigation focussed on the influences of pulse overlap, focus spot diameter and resulting fluence on process quality and machining time.Results showed that ns-pulsed UV-lasers are capable of machining both types of fibre reinforced composites, while achieving good quality surfaces without burn marks or otherwise heat-damaged areas.

  12. Modeling of plasma distortions by laser-induced ablation spectroscopy (LIAS) and implications for the interpretation of LIAS measurements

    NASA Astrophysics Data System (ADS)

    Tokar, M. Z.; Gierse, N.; Philipps, V.; Samm, U.

    2015-09-01

    For the interpretation of the line radiation observed from laser induced ablation spectroscopy (LIAS) such parameters as the density and temperature of electrons within very compact clouds of atoms and singly charged ions of ablated material have to be known. Compared to the local plasma conditions prior to the laser pulse, these can be strongly changed during LIAS since new electrons are generated by the ionisation of particles ejected from the irradiated target. Because of their transience and spatial inhomogeneity it is technically difficult to measure disturbances induced in the plasma by LIAS. To overcome this uncertainty a numerical model has been elaborated, providing a self-consistent description for the spreading of ablated particles and accompanying modifications in the plasma. The results of calculations for LIAS performed on carbon-containing targets in Ohmic and additionally heated discharges in the tokamak TEXTOR are presented. Due to the increase in the electron density the ‘ionisation per photon’ ratio, S/XB factor, is significantly enhanced compared to unperturbed plasma conditions. The impact of the amount of material ablated and of the plasma conditions before LIAS on the level of the S/XB-enhancement is investigated.

  13. The effects of pulse duration on ablation pressure driven by laser radiation

    SciTech Connect

    Zhou, Lei; Li, Xiao-Ya Zhu, Wen-Jun; Wang, Jia-Xiang; Tang, Chang-Jian

    2015-03-28

    The effects of laser pulse duration on the ablation pressure induced by laser radiation are investigated using Al target. Numerical simulation results using one dimensional radiation hydro code for laser intensities from 5×10{sup 12}W/cm{sup 2} to 5×10{sup 13}W/cm{sup 2} and pulse durations from 0.5 ns to 20 ns are presented. These results suggest that the laser intensity scaling law of ablation pressure differs for different pulse durations. And the theoretical analysis shows that the effects of laser pulse duration on ablation pressure are mainly caused by two regimes: the unsteady-state flow and the radiative energy loss to vacuum.

  14. Oscillating plasma bubbles. II. Pulsed experiments

    SciTech Connect

    Stenzel, R. L.; Urrutia, J. M.

    2012-08-15

    Time-dependent phenomena have been investigated in plasma bubbles which are created by inserting spherical grids into an ambient plasma and letting electrons and ions form a plasma of different parameters than the ambient one. There are no plasma sources inside the bubble. The grid bias controls the particle flux. There are sheaths on both sides of the grid, each of which passes particle flows in both directions. The inner sheath or plasma potential develops self consistently to establish charge neutrality and divergence free charge and mass flows. When the electron supply is restricted, the inner sheath exhibits oscillations near the ion plasma frequency. When all electrons are excluded, a virtual anode forms on the inside sheath, reflects all ions such that the bubble is empty. By pulsing the ambient plasma, the lifetime of the bubble plasma has been measured. In an afterglow, plasma electrons are trapped inside the bubble and the bubble decays as slow as the ambient plasma. Pulsing the grid voltage yields the time scale for filling and emptying the bubble. Probes have been shown to modify the plasma potential. Using pulsed probes, transient ringing on the time scale of ion transit times through the bubble has been observed. The start of sheath oscillations has been investigated. The instability mechanism has been qualitatively explained. The dependence of the oscillation frequency on electrons in the sheath has been clarified.

  15. Femtosecond laser ablation of carbon: From spallation to formation of hot critical plasma

    NASA Astrophysics Data System (ADS)

    Kudryashov, S. I.; Ionin, A. A.; Makarov, S. V.; Mel'nik, N. N.; Seleznev, L. V.; Sinitsyn, D. V.

    2012-07-01

    Strong ablative shock waves were generated on a highly oriented pyrolytic graphite surface by intense IR femtosecond laser pulses in a broad fluence range and their basic parameters (pressure, velocity) were acquired by means of a non-contact broadband ultrasonic technique. At moderate laser fluences (F ≥ 0.3 J/cm2), ultrafast formation of a dense, strongly-heated (supercritical) carbon phase is expected, which expands on a fluence-dependent picosecond timescale in the form of a point-like three-dimensional explosion, driving a multi-GPa shock wave both in ambient air and the graphite target. At higher laser fluences (F > 5 J/cm2), critical electron-ion plasma is formed instantaneously during the exciting femtosecond laser pulse, with its strong plasma absorption initiating a TPa-level shock wave (the maximum shock wave pressure ≈ 3 TPa is more than twice the previous maximum for carbon). Because of the ablative removal of the laser-heated surface carbon layer, the following time-integrated structural studies indicate the formation of a mixture of diamond and graphite nanocrystallites or, in other words, glassy carbon only in the redeposition products.

  16. Influence of pulse width on ultraviolet laser ablation of poly(methyl methacrylate)

    NASA Astrophysics Data System (ADS)

    Srinivasan, R.; Braren, Bodil

    1988-10-01

    The etching of poly(methyl methacrylate) using pulses of 248 nm laser radiation which had a full width at half maximum (FWHM) of 40-100 ns is reported. These pulses were created by combining two identical pulses, each of 40 ns FWHM, with a set time delay. The etch depth/pulse is sensitive to the pulse width and, therefore, the power density in this polymer. It can be explained by the changes in absorptivity during a pulse that have been reported by G. M. Davis and M. C. Gower [J. Appl. Phys. 61, 2090 (1987)]. The shape of the pulse was also found to influence the etch depth/pulse. The etching of polyimide by these extended pulses shows trends that are opposite to those observed in poly(methyl methacrylate). In this instance, the shielding of the latter portion of the incoming pulse by the products that are ablated by the front portion is probably a serious effect.

  17. Nanoparticle mediated thermal ablation of breast cancer cells using a nanosecond pulsed electric field.

    PubMed

    Burford, Christopher D; Bhattacharyya, Kiran D; Boriraksantikul, Nattaphong; Whiteside, Paul J D; Robertson, Benjamin P; Peth, Sarah M; Islam, Naz E; Viator, John A

    2013-06-01

    In the past, ablation of cancer cells using radiofrequency heating techniques has been demonstrated, but the current methodology has many flaws, including inconsistent tumor ablation and significant ablation of normal cells. Other researchers have begun to develop a treatment that is more selective for cancer cells using metallic nanoparticles and constant electric field exposure. In these studies, cell necrosis is induced by heating antibody functionalized metallic nanoparticles attached to cancer cells. Our approach to studying this phenomenon is to use similarly functionalized metallic nanoparticles that are specific for the T47D breast cancer cell line, exposing these nanoparticle cell conjugates to a nanosecond pulsed electric field. Using fluorescent, polystyrene-coated, iron-oxide nanoparticles, the results of our pilot study indicated that we were able to ablate up to approximately 80% of the cells using 60 ns pulses in increasing numbers of pulses and up to approximately 90% of the cells using 300 ns pulses in increasing numbers of pulses. These quantities of ablated cells were achieved using a cumulative exposure time 6 orders of magnitude less than most in vitro constant electric field studies. PMID:23694696

  18. Relativistic plasma shutter for ultraintense laser pulses

    PubMed Central

    Reed, Stephen A.; Matsuoka, Takeshi; Bulanov, Stepan; Tampo, Motonobu; Chvykov, Vladimir; Kalintchenko, Galina; Rousseau, Pascal; Yanovsky, Victor; Kodama, Ryousuke; Litzenberg, Dale W.; Krushelnick, Karl; Maksimchuk, Anatoly

    2009-01-01

    A relativistic plasma shutter technique is proposed and tested to remove the sub-100 ps pedestal of a high-intensity laser pulse. The shutter is an ultrathin foil placed before the target of interest. As the leading edge of the laser ionizes the shutter material it will expand into a relativistically underdense plasma allowing for the peak pulse to propagate through while rejecting the low intensity pedestal. An increase in the laser temporal contrast is demonstrated by measuring characteristic signatures in the accelerated proton spectra and directionality from the interaction of 30 TW pulses with ultrathin foils along with supporting hydrodynamic and particle-in-cell simulations. PMID:19654882

  19. Plasma in a Pulsed Discharge Environment

    NASA Technical Reports Server (NTRS)

    Remy, J.; Bienier, L.; Salama, F.

    2005-01-01

    The plasma generated in a pulsed slit discharge nozzle is used to form molecular ions in an astrophysically relevant environment. The plasma has been characterized as a glow discharge in the abnormal regime. Laboratory studies help understand the formation processes of polycyclic aromatic hydrocarbon (PAH) ions that are thought to be the source of the ubiquitous unidentified infrared bands.

  20. Laser ablated zirconium plasma: A source of neutral zirconium

    SciTech Connect

    Yadav, Dheerendra; Thareja, Raj K.

    2010-10-15

    The authors report spectroscopic investigations of laser produced zirconium (Zr) plasma at moderate laser fluence. At low laser fluence the neutral zirconium species are observed to dominate over the higher species of zirconium. Laser induced fluorescence technique is used to study the velocity distribution of ground state neutral zirconium species. Two-dimensional time-resolved density distributions of ground state zirconium is mapped using planner laser induced fluorescence imaging and total ablated mass of neutral zirconium atoms is estimated. Temporal and spatial evolutions of electron density and temperature are discussed by measuring Stark broadened profile and ratio of intensity of emission lines, respectively.

  1. Repetitively pulsed plasma illumination sources

    NASA Astrophysics Data System (ADS)

    Root, Robert G.; Falkos, Paul

    1997-12-01

    The acoustic environment created by turbulence in aircraft flight tests demands that illumination sources for high speed photography of munitions drops be extremely rugged. A repetitive pulsed surface discharge system has been developed to provide wide angle illumination in a bomb bay for photography at 250 - 500 Hertz. The lamp has a simple construction suitable for adverse environments and produces 100 mJ of visible light per pulse. The discharge parameters were selected to minimize the size and complexity of the power supply. The system is also capable of operating at high repetition rates; preliminary tests demonstrated 1000 pulses at 1 kHz, 200 pulses at 1.5 kHz, and 13 pulses at 2 kHz. A simple power supply capable of providing several amperes at 450 V is being completed; it will be used to extend the run times and to explore extensions to higher repetition rate.

  2. Mapping neutral, ion, and electron number densities within laser-ablated plasma plumes

    NASA Astrophysics Data System (ADS)

    Weaver, I.; Doyle, Liam A.; Martin, G. W.; Riley, Dave; Lamb, M. J.; Graham, William G.; Morrow, Tom; Lewis, Ciaran L. S.

    1998-05-01

    Spatially and temporally varying neutral, ion and electron number densities have been mapped out within laser ablated plasma plumes expanding into vacuum. Ablation of a magnesium target was performed using a KrF laser, 30 ns pulse duration and 248 nm wavelength. During the initial stage of plasma expansion (t plasma expansion (t equals 1 microsecond(s) ) simultaneous absorption and laser induced fluorescence spectroscopy has been used to determine 3D neutral and ion number densities, for a power density equal to 6.7 X 107 W/cm2. Two distinct regions within the plume were identified. One is a fast component (approximately 106 cm-1) consisting of ions and neutrals with maximum number densities observed to be approximately 30 and 4 X 1012 cm-3 respectively, and the second consists of slow moving neutral material at a number density of up to 1015 cm-3. Additionally a Langmuir probe has been used to obtain ion and electron number densities at very late times in the plasma expansion (1 microsecond(s) ablated using a Nd:YAG laser, 7.5 ns duration and 532 nm (2 (omega) ) wavelength, with a power density on target equal to 6 X 108 W/cm2. Two regions within the plume with different velocities were observed. Within a fast component (approximately 3 X 106 cms-1) electron and ion number densities of the order 5 X 1012 cm-3 were observed and within the second slower component (approximately 106 cms-1) electron and ion number densities of the order 1 - 2 X 1013 cm-3 were determined.

  3. Investigations of the damage mechanisms during ultrashort pulse laser ablation of dental tissue

    NASA Astrophysics Data System (ADS)

    Domke, Matthias; Wick, Sebastian; Laible, Maike; Rapp, Stephan; Kuznetsova, Julia; Homann, Christian; Huber, Heinz P.; Sroka, Ronald

    2015-07-01

    Several investigations of dental tissue ablation with ultrashort pulsed lasers suggest that these lasers enable precise and selective material removal and reduce the formation of micro cracks and thermal effects, when compared to ns-pulses. In this study, two damage mechanisms are presented occurring during ablation of dentin using a laser emitting pulses of a duration of 380 fs at a wavelength of 1040 nm. First, it was found that nano cracks appear around the craters after single fs-pulse ablation. These cracks are directed to the crater and cross the dentinal tubules. Transient investigation of the single fs-pulse ablation process by pump-probe microscopy suggest that the driving mechanism could be a pressure wave that is released after stress confinement. Second, squared ablation holes were created by moving the laser focus at scan speeds between 0.5 mm/s and 2.0 m/s and fluences up to 14 J/cm2. It was found that deep cracks appear at the edges of the squared holes, if the scan speed is about 0.5 m/s. The fluence has only a minor impact on the crack formation. The crack propagation was investigated in the depth using x-ray micro tomography and optical coherence tomography. It was found that these cracks appear in the depth down to the dental pulp. These findings suggest that fast scanning of the laser beam is the key for damage free processing using ultrashort pulse lasers. Then, ablation rates of about 2.5 - 3.5 mm3/min/W can be achieved in dentine with pulse durations of 380 fs.

  4. Relativistic laser pulse compression in magnetized plasmas

    SciTech Connect

    Liang, Yun; Sang, Hai-Bo Wan, Feng; Lv, Chong; Xie, Bai-Song

    2015-07-15

    The self-compression of a weak relativistic Gaussian laser pulse propagating in a magnetized plasma is investigated. The nonlinear Schrödinger equation, which describes the laser pulse amplitude evolution, is deduced and solved numerically. The pulse compression is observed in the cases of both left- and right-hand circular polarized lasers. It is found that the compressed velocity is increased for the left-hand circular polarized laser fields, while decreased for the right-hand ones, which is reinforced as the enhancement of the external magnetic field. We find a 100 fs left-hand circular polarized laser pulse is compressed in a magnetized (1757 T) plasma medium by more than ten times. The results in this paper indicate the possibility of generating particularly intense and short pulses.

  5. Laser Ablation of Biological Tissue Using Pulsed CO{sub 2} Laser

    SciTech Connect

    Hashishin, Yuichi; Sano, Shu; Nakayama, Takeyoshi

    2010-10-13

    Laser scalpels are currently used as a form of laser treatment. However, their ablation mechanism has not been clarified because laser excision of biological tissue occurs over a short time scale. Biological tissue ablation generates sound (laser-induced sound). This study seeks to clarify the ablation mechanism. The state of the gelatin ablation was determined using a high-speed video camera and the power reduction of a He-Ne laser beam. The aim of this study was to clarify the laser ablation mechanism by observing laser excision using the high-speed video camera and monitoring the power reduction of the He-Ne laser beam. We simulated laser excision of a biological tissue by irradiating gelatin (10 wt%) with radiation from a pulsed CO{sub 2} laser (wavelength: 10.6 {mu}m; pulse width: 80 ns). In addition, a microphone was used to measure the laser-induced sound. The first pulse caused ablation particles to be emitted in all directions; these particles were subsequently damped so that they formed a mushroom cloud. Furthermore, water was initially evaporated by laser irradiation and then tissue was ejected.

  6. Determination of ablation threshold for composite resins and amalgam irradiated with femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Freitas, A. Z.; Freschi, L. R.; Samad, R. E.; Zezell, D. M.; Gouw-Soares, S. C.; Vieira, N. D., Jr.

    2010-03-01

    The use of laser for caries removal and cavity preparation is already a reality in the dental clinic. The objective of the present study was to consider the viability of ultrashort laser pulses for restorative material selective removal, by determining the ablation threshold fluence for composite resins and amalgam irradiated with femtosecond laser pulses. Lasers pulses centered at 830 nm with 50 fs of duration and 1 kHz of repetition rate, with energies in the range of 300 to 770 μJ were used to irradiate the samples. The samples were irradiated using two different geometrical methods for ablation threshold fluence determinations and the volume ablation was measured by optical coherence tomography. The shape of the ablated surfaces were analyzed by optical microscopy and scanning electron microscopy. The determined ablation threshold fluence is 0.35 J/cm2 for the composite resins Z-100 and Z-350, and 0.25 J/cm2 for the amalgam. These values are half of the value for enamel in this temporal regime. Thermal damages were not observed in the samples. Using the OCT technique (optical coherence tomography) was possible to determine the ablated volume and the total mass removed.

  7. Pulsed laser ablation of Germanium under vacuum and hydrogen environments at various fluences

    NASA Astrophysics Data System (ADS)

    Iqbal, Muhammad Hassan; Bashir, Shazia; Rafique, Muhammad Shahid; Dawood, Asadullah; Akram, Mahreen; Mahmood, Khaliq; Hayat, Asma; Ahmad, Riaz; Hussain, Tousif; Mahmood, Arshad

    2015-07-01

    Laser fluence and ambient environment play a significant role for the formation and development of the micro/nano-structures on the laser irradiated targets. Single crystal (1 0 0) Germanium (Ge) has been ablated under two environments of vacuum (10-3 Torr) and hydrogen (100 Torr) at various fluences ranging from 4.5 J cm-2 to 6 J cm-2. For this purpose KrF Excimer laser with wavelength of 248 nm, pulse duration of 18 ns and repetition rate of 20 Hz has been employed. Surface morphology has been observed by Scanning Electron Microscope (SEM). Whereas, structural modification of irradiated targets was explored by Fourier Transform Infrared Spectroscopy (FTIR) and Raman spectroscopy. Electrical conductivity of the irradiated Ge is measured by four probe method. SEM analysis exhibits the formation of laser-induced periodic surface structures (LIPSS), cones and micro-bumps in both ambient environments (vacuum and hydrogen). The formation as well as development of these structures is strongly dependent upon the laser fluence and environmental conditions. The periodicity of LIPSS or ripples varies from 38 μm to 60 μm in case of vacuum whereas in case of hydrogen environment, the periodicity varies from 20 μm to 45 μm. The difference in number of ripples and periodicity as well as in shape and size of cones and bumps in vacuum and hydrogen is explained on the basis of confinement and shielding effect of plasma. FTIR spectroscopy reveals that no new bands are formed for laser ablated Ge under vacuum, whereas Csbnd H stretching vibration band is formed for two moderate fluences (5 J cm-2 and 5.5 J cm-2) in case of ablation in hydrogen. Raman spectroscopy shows that no new bands are formed in case of ablation in both environments; however a slight Raman shift is observed which is attributed to laser-induced stresses. The electrical conductivity of the irradiated Ge increases with increasing fluence and is also dependent upon the environment as well as grown structures.

  8. Evaluation of the temporal profiles and the analytical features of a laser ablation - Pulsed glow discharge coupling for optical emission spectrometry

    NASA Astrophysics Data System (ADS)

    González de Vega, Claudia; Bordel, Nerea; Pereiro, Rosario; Sanz-Medel, Alfredo

    2016-07-01

    The coupling of a glow discharge (GD) in pulsed mode (PGD) as secondary source for excitation/ionization of the material provided by laser ablation (LA) has been investigated using optical emission spectrometry (OES). The variation of the laser pulse delay with respect to the GD pulse allows to producing the ablation process during prepeak, plateau or afterglow GD regions. Emission properties of the LA-PGD plasma in each temporal region of the GD pulse have been evaluated for analytical lines of different elements. Resonant atomic lines have shown higher emission intensity in the prepeak region compared to non-resonant lines. Non-resonant lines showed higher enhancement of the emission intensity in the afterglow region. Moreover, the coupled LA-PGD system offered better linear correlation coefficients using a set of glass standards for calibration as well as lower detection limits (by at least a factor of two) when compared to laser induced breakdown spectroscopy.

  9. Visualization of liquid-assisted hard tissue ablation with a pulsed CO2 laser

    NASA Astrophysics Data System (ADS)

    Li, X. W.; Chen, C. G.; Zhang, X. Z.; Zhan, Z. L.; Xie, S. S.

    2015-01-01

    To investigate the characteristics of liquid-mediated hard tissue ablation induced by a pulsed CO2 laser with a wavelength of 10.6 μm, a high speed camera was used to monitor the interaction between water, tissue and laser irradiation. The results showed that laser irradiation can directly impact on tissue through a vapor channel formed by the leading part of the laser pulse. The ablation debris plays a key role in liquid-assisted laser ablation, having the ability to keep the vapor channel open to extend actuation time. The runoff effect induced by vortex convection liquid flow can remove the tissue that obstructs the effect of the next laser pulse.

  10. Ablation of femural bone with femtosecond laser pulses--a feasibility study.

    PubMed

    Liu, Yifei; Niemz, Markolf

    2007-09-01

    Although lasers are nowadays widely accepted as a popular scalpel of minimally invasive surgery (MIS), one of the most common orthopedic surgeries-the replacement of the knee joint-is still performed using an ordinary oscillating saw. Since ultra-short laser pulses are usually considered to be inefficient regardless of their high precision, the newest development of femtosecond laser systems has not yet been clinically applied to any mass ablation situation. However, thin disk Yb:KYW lasers meanwhile provide sufficient output power to ablate bone tissue within a reasonable time frame. Our results mainly focus on ablation rates obtained at different spot distances, repetition rates and pulse energies. It is shown that femtosecond laser pulses at high repetition rates are a promising tool for orthopedic surgery. PMID:17242869

  11. Pulsed RF Plasma Source for Materials Processing

    NASA Astrophysics Data System (ADS)

    Nasiruddin, Abutaher Mohammad

    A pulsed rf plasma source was evaluated for materials processing. A pulsed rf discharge of carbon tetrafluoride (CF_4), sulfur hexafluoride (SF _6), oxygen (O_2), or acetylene (C_2H_2 ) created the plasmas. The frequency and duration of the rf discharge were about 290 kHz and 30 musec, respectively. The repetition rate was 1 discharge per minute. Plasma diagnostics included Langmuir probes, a photodiode dectector, an optical multichannel analyzer (OMA), and a microwave interferometer. Langmuir probe measurements showed that at a position 67 cm away from the rf coil, CF_4 plasma arrived in separate packets. Plasma densities and electron temperatures at this position were in the range 4 times 10^{11} cm ^{-3} to 1.8 times 10^{13} cm ^{-3} and 2 eV to 8.3 eV, respectively. The OMA measurements identified neutral atomic fluorine in the CF_4 plasma and neutral atomic oxygen in the O_2 plasma. A plasma slab model of the microwave interferometer was applied to predict the interferometer response. The measured response was found to be almost identical to the predicted response. The influence of different reactor parameters on plasma parameters was studied. Metal barriers of different geometry were used to control the ratio of charged particles to atomic neutrals in the plasma chamber. Four plasma structures were identified: precursor plasma, shock induced plasma, driver plasma, and delayed glow plasma. Pulsed CF _4 and SF_6 plasmas were used to etch silicon dioxide (SiO_2 ) grown on silicon wafers. The SF_6 plasma etched SiO_2 at a rate of about 0.71 A per discharge and the CF_4 plasma deposited a non-uniform film (possibly polymer) instead of etching. The C_2H _2 plasma deposited plasma polymerized acetylene on a KBr pellet with a deposition rate of 127 A per discharge. An FT-IR spectrum of the deposited film showed that carbon -to-carbon double bonds as well as carbon-to-hydrogen bonds were present. This device can be used in plasma assisted deposition and/or synthesis

  12. Laser ablation of GaAs in liquid: the role of laser pulse duration

    NASA Astrophysics Data System (ADS)

    De Bonis, Angela; Galasso, Agostino; Santagata, Antonio; Teghil, Roberto

    2016-01-01

    The synthesis of gallium arsenide (GaAs) nanoparticles has attracted wide scientific and technological interest due to the possibility of tuning the GaAs NP (nanoparticle) band gap across the visible spectrum and their consequent use in optoelectronic devices. In recent years, laser ablation in liquid (LAL) has been widely used for the preparation of colloidal solutions of semiconducting and metallic nanoparticles, thanks to its flexibility. With the aim of highlighting the key role played by laser pulse duration on the ablation mechanism and on the properties of the obtained materials, laser ablation of a gallium arsenide target in acetone was performed using laser sources operating in two different temporal regimes: Nd:glass laser (λ   =  527 nm, pulse duration of 250 fs and frequency repetition rate of 10 Hz) and Nd:YAG laser (λ   =  532 nm, pulse duration of 7 ns and frequency repetition rate of 10 Hz). The ablation process was studied following the dynamics of the laser induced shock waves (SWs) and cavitation bubbles (CBs) by fast shadowgraphy, showing that CB dimension and lifetime is related to the laser pulse length. A characterization of the obtained materials by TEM (transmission electron microscopy) and microRaman spectroscopy have shown that quite spherical gallium oxide/GaAs nanoparticles can be obtained by nanosecond laser ablation. On the other hand, pure polycrystalline GaAs nanoparticles can be produced by using an ultrashort laser source.

  13. Planarization of Isolated Defects on ICF Target Capsule Surfaces by Pulsed Laser Ablation

    DOE PAGESBeta

    Alfonso, Noel; Carlson, Lane C.; Bunn, Thomas L.

    2016-08-09

    Demanding surface quality requirements for inertial confinement fusion (ICF) capsules motivated the development of a pulsed laser ablation method to reduce or eliminate undesirable surface defects. The pulsed laser ablation technique takes advantage of a full surface (4π) capsule manipulation system working in combination with an optical profiling (confocal) microscope. Based on the defect topography, the material removal rate, the laser pulse energy and its beam profile, a customized laser raster pattern is derived to remove the defect. The pattern is a table of coordinates and number of pulses that dictate how the defect will be vaporized until its heightmore » is level with the capsule surface. This paper explains how the raster patterns are optimized to minimize surface roughness and how surface roughness after laser ablation is simulated. The simulated surfaces are compared with actual ablated surfaces. Large defects are reduced to a size regime where a tumble finishing process produces very high quality surfaces devoid of high mode defects. The combined polishing processes of laser ablation and tumble finishing have become routine fabrication steps for National Ignition Facility capsule production.« less

  14. Effect of the pulse repetition rate on fiber-assisted tissue ablation

    NASA Astrophysics Data System (ADS)

    Kang, Hyun Wook

    2016-07-01

    The effect of the pulse repetition rate on ablation performance was evaluated ex vivo at various fiber sweeping speeds for an effective 532-nm laser prostatectomy. Three pulse repetition rates (7.5, 15, and 30 kHz) at 100 W were delivered to bovine liver tissue at three sweeping speeds (2, 4, and 6 mm/s) to achieve bulky tissue removal. Ablation performance was quantitatively compared in terms of the ablation volume and the coagulation thickness. The lowest pulse repetition rate of 7.5 kHz attained the highest ablation volume (101.5 ± 12.0 mm3) and the thinnest coagulation (0.7 ± 0.1 mm) along with superficial carbonization. The highest pulse repetition rate of 30 kHz was associated with the least tissue removal (65.8 ± 5.0 mm3) and the deepest thermal denaturation (1.1 ± 0.2 mm). Quantitative evaluations of laser parameters can be instrumental in facilitating ablation efficiency and maintaining hemostatic coagulation during treatment of large-sized benign prostate hyperplasia.

  15. An improved three-dimensional two-temperature model for multi-pulse femtosecond laser ablation of aluminum

    SciTech Connect

    Zhang, Jinping; Chen, Yuping Hu, Mengning; Chen, Xianfeng

    2015-02-14

    In this paper, an improved three-dimensional two-temperature model for multi-pulse femtosecond laser ablation of aluminum was proposed and proved in our experiment. Aiming to achieve hole-drilling with a high ratio of depth/entrance diameter in vacuum, this model can predict the depth and radius of the drilled holes precisely when employing different laser parameters. Additionally, for multi-pulse laser ablation, we found that the laser fluence and number of pulses are the dominant parameters and the multi-pulse ablation threshold is much lower than the single-pulse one, which will help to obtain high-quality holes.

  16. Cold Atmospheric Plasma for Selectively Ablating Metastatic Breast Cancer Cells

    PubMed Central

    Wang, Mian; Holmes, Benjamin; Cheng, Xiaoqian; Zhu, Wei; Keidar, Michael; Zhang, Lijie Grace

    2013-01-01

    Traditional breast cancer treatments such as surgery and radiotherapy contain many inherent limitations with regards to incomplete and nonselective tumor ablation. Cold atomospheric plasma (CAP) is an ionized gas where the ion temperature is close to room temperature. It contains electrons, charged particles, radicals, various excited molecules, UV photons and transient electric fields. These various compositional elements have the potential to either enhance and promote cellular activity, or disrupt and destroy them. In particular, based on this unique composition, CAP could offer a minimally-invasive surgical approach allowing for specific cancer cell or tumor tissue removal without influencing healthy cells. Thus, the objective of this research is to investigate a novel CAP-based therapy for selectively bone metastatic breast cancer treatment. For this purpose, human metastatic breast cancer (BrCa) cells and bone marrow derived human mesenchymal stem cells (MSCs) were separately treated with CAP, and behavioral changes were evaluated after 1, 3, and 5 days of culture. With different treatment times, different BrCa and MSC cell responses were observed. Our results showed that BrCa cells were more sensitive to these CAP treatments than MSCs under plasma dose conditions tested. It demonstrated that CAP can selectively ablate metastatic BrCa cells in vitro without damaging healthy MSCs at the metastatic bone site. In addition, our study showed that CAP treatment can significantly inhibit the migration and invasion of BrCa cells. The results suggest the great potential of CAP for breast cancer therapy. PMID:24040051

  17. Gas Effect On Plasma Dynamics Of Laser Ablation Zinc Oxide

    NASA Astrophysics Data System (ADS)

    Abdelli-Messaci, S.; Kerdja, T.; Lafane, S.; Malek, S.

    2008-09-01

    In order to synthesis zinc oxide thin films and nanostructures, laser ablation of ZnO target into both vacuum and oxygen atmosphere was performed. The gas effect on the plume dynamics was studied for O2 pressures varied between 10-2 to 70 mbar. Plasma plume evolution was investigated by ICCD camera fast imaging. The plasma was created by a KrF excimer laser (λ = 248 nm, τ = 25 ns) at a fluence of 2 J/cm2. The light emitted by the plume was observed along the perpendicular to the ejection direction through a fast intensified charge-coupled device (ICCD). We have found that the plasma dynamics is very affected by the gas pressures. The photographs reveal the stratification of plasma into slow and fast components for 0.5 mbar O2 pressures and beyond. The photographs also show the apparition of hydrodynamic instabilities which are related to chemical reactions between the plasma and the surrounding gas for a certain range of pressures.

  18. Gas Effect On Plasma Dynamics Of Laser Ablation Zinc Oxide

    SciTech Connect

    Abdelli-Messaci, S.; Kerdja, T.; Lafane, S.; Malek, S.

    2008-09-23

    In order to synthesis zinc oxide thin films and nanostructures, laser ablation of ZnO target into both vacuum and oxygen atmosphere was performed. The gas effect on the plume dynamics was studied for O{sub 2} pressures varied between 10{sup -2} to 70 mbar. Plasma plume evolution was investigated by ICCD camera fast imaging. The plasma was created by a KrF excimer laser ({lambda} = 248 nm, {tau} = 25 ns) at a fluence of 2 J/cm{sup 2}. The light emitted by the plume was observed along the perpendicular to the ejection direction through a fast intensified charge-coupled device (ICCD). We have found that the plasma dynamics is very affected by the gas pressures. The photographs reveal the stratification of plasma into slow and fast components for 0.5 mbar O{sub 2} pressures and beyond. The photographs also show the apparition of hydrodynamic instabilities which are related to chemical reactions between the plasma and the surrounding gas for a certain range of pressures.

  19. Modeling ultrashort-pulse laser ablation of dielectric materials

    SciTech Connect

    Christensen, B. H.; Balling, P.

    2009-04-15

    An approach to modeling ablation thresholds and depths in dielectric materials is proposed. The model is based on the multiple-rate-equation description suggested by Rethfeld [Phys. Rev. Lett. 92, 187401 (2004)]. This model has been extended to include a description of the propagation of the light into the dielectric sample. The generic model is based on only a few experimental quantities that characterize the native material. A Drude model describing the evolution of the dielectric constant owing to an excitation of the electrons in the material is applied. The model is compared to experimental ablation data for different dielectric materials from the literature.

  20. Destruction of monocrystalline silicon with nanosecond pulsed fiber laser accompanied by the oxidation of ablation microparticles

    NASA Astrophysics Data System (ADS)

    Veiko, V. P.; Skvortsov, A. M.; Huynh, C. T.; Petrov, A. A.

    2013-11-01

    In this work, we report an observation of process of local destruction monocrystalline silicon with a scanning beam irradiation of pulse ytterbium fiber laser with a wavelength λ= 1062 nm, accompanied by the oxidation of ablation microparticles. It is shown that depending on the power density of irradiation was observed a large scatter size of the microparticles. From a certain average power density is observed beginning oxidation particulate emitted from the surface of the irradiated area. By varying the parameters of the laser beam such as scanning speed, pulse repetition rate, overlap of laser spot, radiation dose can be achieved almost complete oxidation of all formed during the ablation of microparticles.

  1. Pulsed Nd:YAG laser selective ablation of surface enamel caries: I. Photoacoustic response and FTIR spectroscopy

    NASA Astrophysics Data System (ADS)

    Harris, David M.; Fried, Daniel

    2000-03-01

    Enamel caries lesions on extracted teeth were ablated with a pulsed Nd:YAG or Er:YAG laser. Tissue ablation was accompanied by a 'popping' sound (the photoacoustic response). Analysis of the photoacoustic response yields insights into the laser/tissue interactions. Fourier Transform Infrared (FTIR) Spectroscopy of lesions before ablation show a strong protein component associated with organic material (i.e., bacteria). Following ablation this protein component is absent.

  2. Dynamics of plasma expansion and shockwave formation in femtosecond laser-ablated aluminum plumes in argon gas at atmospheric pressures

    SciTech Connect

    Miloshevsky, Alexander; Harilal, Sivanandan S.; Miloshevsky, Gennady Hassanein, Ahmed

    2014-04-15

    Plasma expansion with shockwave formation during laser ablation of materials in a background gasses is a complex process. The spatial and temporal evolution of pressure, temperature, density, and velocity fields is needed for its complete understanding. We have studied the expansion of femtosecond (fs) laser-ablated aluminum (Al) plumes in Argon (Ar) gas at 0.5 and 1 atmosphere (atm). The expansion of the plume is investigated experimentally using shadowgraphy and fast-gated imaging. The computational fluid dynamics (CFD) modeling is also carried out. The position of the shock front measured by shadowgraphy and fast-gated imaging is then compared to that obtained from the CFD modeling. The results from the three methods are found to be in good agreement, especially during the initial stage of plasma expansion. The computed time- and space-resolved fields of gas-dynamic parameters have provided valuable insights into the dynamics of plasma expansion and shockwave formation in fs-pulse ablated Al plumes in Ar gas at 0.5 and 1 atm. These results are compared to our previous data on nanosecond (ns) laser ablation of Al [S. S. Harilal et al., Phys. Plasmas 19, 083504 (2012)]. It is observed that both fs and ns plumes acquire a nearly spherical shape at the end of expansion in Ar gas at 1 atm. However, due to significantly lower pulse energy of the fs laser (5 mJ) compared to pulse energy of the ns laser (100 mJ) used in our studies, the values of pressure, temperature, mass density, and velocity are found to be smaller in the fs laser plume, and their time evolution occurs much faster on the same time scale. The oscillatory shock waves clearly visible in the ns plume are not observed in the internal region of the fs plume. These experimental and computational results provide a quantitative understanding of plasma expansion and shockwave formation in fs-pulse and ns-pulse laser ablated Al plumes in an ambient gas at atmospheric pressures.

  3. Dynamics of plasma expansion and shockwave formation in femtosecond laser-ablated aluminum plumes in argon gas at atmospheric pressures

    NASA Astrophysics Data System (ADS)

    Miloshevsky, Alexander; Harilal, Sivanandan S.; Miloshevsky, Gennady; Hassanein, Ahmed

    2014-04-01

    Plasma expansion with shockwave formation during laser ablation of materials in a background gasses is a complex process. The spatial and temporal evolution of pressure, temperature, density, and velocity fields is needed for its complete understanding. We have studied the expansion of femtosecond (fs) laser-ablated aluminum (Al) plumes in Argon (Ar) gas at 0.5 and 1 atmosphere (atm). The expansion of the plume is investigated experimentally using shadowgraphy and fast-gated imaging. The computational fluid dynamics (CFD) modeling is also carried out. The position of the shock front measured by shadowgraphy and fast-gated imaging is then compared to that obtained from the CFD modeling. The results from the three methods are found to be in good agreement, especially during the initial stage of plasma expansion. The computed time- and space-resolved fields of gas-dynamic parameters have provided valuable insights into the dynamics of plasma expansion and shockwave formation in fs-pulse ablated Al plumes in Ar gas at 0.5 and 1 atm. These results are compared to our previous data on nanosecond (ns) laser ablation of Al [S. S. Harilal et al., Phys. Plasmas 19, 083504 (2012)]. It is observed that both fs and ns plumes acquire a nearly spherical shape at the end of expansion in Ar gas at 1 atm. However, due to significantly lower pulse energy of the fs laser (5 mJ) compared to pulse energy of the ns laser (100 mJ) used in our studies, the values of pressure, temperature, mass density, and velocity are found to be smaller in the fs laser plume, and their time evolution occurs much faster on the same time scale. The oscillatory shock waves clearly visible in the ns plume are not observed in the internal region of the fs plume. These experimental and computational results provide a quantitative understanding of plasma expansion and shockwave formation in fs-pulse and ns-pulse laser ablated Al plumes in an ambient gas at atmospheric pressures.

  4. Ablation by ultrashort laser pulses: Atomistic and thermodynamic analysis of the processes at the ablation threshold

    SciTech Connect

    Upadhyay, Arun K.; Inogamov, Nail A.; Rethfeld, Baerbel; Urbassek, Herbert M.

    2008-07-15

    Ultrafast laser irradiation of solids may ablate material off the surface. We study this process for thin films using molecular-dynamics simulation and thermodynamic analysis. Both metals and Lennard-Jones (LJ) materials are studied. We find that despite the large difference in thermodynamical properties between these two classes of materials--e.g., for aluminum versus LJ the ratio T{sub c}/T{sub tr} of critical to triple-point temperature differs by more than a factor of 4--the values of the ablation threshold energy E{sub abl} normalized to the cohesion energy, {epsilon}{sub abl}=E{sub abl}/E{sub coh}, are surprisingly universal: all are near 0.3 with {+-}30% scattering. The difference in the ratio T{sub c}/T{sub tr} means that for metals the melting threshold {epsilon}{sub m} is low, {epsilon}{sub m}<{epsilon}{sub abl}, while for LJ it is high, {epsilon}{sub m}>{epsilon}{sub abl}. This thermodynamical consideration gives a simple explanation for the difference between metals and LJ. It explains why despite the universality in {epsilon}{sub abl}, metals thermomechanically ablate always from the liquid state. This is opposite to LJ materials, which (near threshold) ablate from the solid state. Furthermore, we find that immediately below the ablation threshold, the formation of large voids (cavitation) in the irradiated material leads to a strong temporary expansion on a very slow time scale. This feature is easily distinguished from the acoustic oscillations governing the material response at smaller intensities, on the one hand, and the ablation occurring at larger intensities, on the other hand. This finding allows us to explain the puzzle of huge surface excursions found in experiments at near-threshold laser irradiation.

  5. Effect of inter-pulse delay time on production and size properties of colloidal nanoparticles prepared by collinear double-pulse laser ablation in liquid

    NASA Astrophysics Data System (ADS)

    Fattahi, Behzad; Mahdieh, Mohammah Hossein

    2016-08-01

    The influence of inter-pulse delay times (0–20 ns) between two collinear sequential nanosecond pulses on the production and size properties (mean size and size distribution) of colloidal nanoparticles prepared by pulsed laser ablation of a silver target in a distilled water medium has been studied. Various laser fluences at different inter-pulse delay times between two collinear pulses were used. Furthermore, for a better understanding of the effect of the double-pulse and single-pulse mode, experiments were performed. The characterization of the synthesized colloidal nanoparticles was investigated using scanning electron microscopy (SEM) and UV–vis absorption spectroscopy. Our results showed that 5 ns time-delayed double-pulse laser ablation results in the production of nanoparticles with the highest concentration among the other time-delayed ablation experiments and even more than single-pulse-mode experiments. It also found that using a double-pulse approach with inter-pulse delay times in the range of 0–20 ns leads to the production of nanoparticles with smaller mean sizes and narrower size distributions in comparison to single-pulse-mode laser ablation. The effect of time overlapping between two pulses in the case of double-pulse ablation was analyzed.

  6. Long term survival of mice with hepatocellular carcinoma after pulse power ablation with nanosecond pulsed electric fields.

    PubMed

    Chen, X; Zhuang, J; Kolb, J F; Schoenbach, K H; Beebe, S J

    2012-02-01

    Novel therapies are needed for treating hepatocellular carcinoma (HCC) without recurrence in a single procedure. In this work we evaluated anti-neoplastic effects of a pulse power ablation (PPA) with nanosecond pulsed electric fields (nsPEFs), a non-thermal, non-drug, local, regional method and investigated its molecular mechanisms for hepatocellular carcinoma tumor ablation in vivo. An ectopic tumor model was established using C57BL/6 mice with Hepa1-6 hepatocellular carcinoma cells. Pulses with durations of 30 or 100 ns and fast rise times were delivered by a needle or ring electrode with different electric field strengths (33, 50 and 68 kV/cm), and 900 pulses in three treatment sessions (300 pulses each session) or a single 900 pulse treatment. Treated and control tumor volumes were monitored by ultrasound and apoptosis and angiogenesis markers were evaluated by immunohistochemistry. Seventy five percent of primary hepatocellular carcinoma tumors were eradicated with 900 hundred pulses at 100 ns pulses at 68 kV/cm in a single treatment or in three treatment sessions without recurrence within 9 months. Using quantitative analysis, tumors in treated animals showed nsPEF-mediated nuclear condensation (3 h post-pulse), cell shrinkage (1 h), increases in active executioner caspases (caspase-3 > -7 > -6) and terminal deoxynucleotidyl transferase dUTP nick-end-labeling (1 h) with decreases in vascular endothelial growth factor expression (7d) and micro-vessel density (14d). NsPEF ablation eliminated hepatocellular carcinoma tumors by targeting two therapeutic sites, apoptosis induction and inhibition of angiogenesis, both important cancer hallmarks. These data indicate that PPA with nsPEFs is not limited to treating skin cancers and provide a rationale for continuing to investigate pulse power ablation for hepatocellular carcinoma using other models in pre-clinical applications and ultimately in clinical trials. Based on present treatments for specific HCC stages, it

  7. Pulsed Energy Systems for Generating Plasmas

    NASA Technical Reports Server (NTRS)

    Rose, M. Franklin; Shotts, Z.

    2005-01-01

    This paper will describe the techniques needed to electrically generate highly ionized dense plasmas for a variety of applications. The components needed in pulsed circuits are described in terms of general performance parameters currently available from commercial vendors. Examples of pulsed systems using these components are described and technical data from laboratory experiments presented. Experimental data are given for point designs, capable of multi-megawatt power levels.

  8. FEU-140 photomultipliers in pulsed plasma spectroscopy

    SciTech Connect

    Arteev, M.S.; Sulakshin, S.S.

    1987-12-01

    Special fast photomultipliers are usually employed in photoelectric spectroscopy of nonstationary plasmas. Measurements have been made on the pulse characteristics and spectral sensitivity for the FEU-140 photomultiplier, which enables one to record a light flux of about 10/sup -10/ W as pulses of duration down to 10 nsec in the range 200-650 nm with a fairly wide linearity range (10/sup -10/-10/sup -18/ W).

  9. Laser-ablation-induced refractive index fields studied using pulsed digital holographic interferometry

    NASA Astrophysics Data System (ADS)

    Amer, Eynas; Gren, Per; Sjödahl, Mikael

    2009-07-01

    Pulsed digital holographic interferometry has been used to investigate the plume and the shock wave generated in the ablation process of a Q-switched Nd-YAG ( λ=1064 nm and pulse duration=12 ns) laser pulse on a polycrystalline boron nitride (PCBN) target under atmospheric air pressure. A special setup based on two synchronised wavelengths from the same laser for simultaneous processing and measurement has been used. Digital holograms were recorded for different time delays using collimated laser light ( λ=532 nm) passed through the volume along the target. Numerical data of the integrated refractive index field were calculated and presented as phase maps showing the propagation of the shock wave and the plume generated by the process. Radon inversion has been used to estimate the 3D refractive index fields measured from the projections assuming rotational symmetry. The shock wave density has been calculated using the point explosion model and the shock wave condition equation and its behaviour with time at different power densities ranging from 1.4 to 9.1 GW/cm 2 is presented. Shock front densities have been calculated from the reconstructed refractive index fields using the Gladstone-Dale equation. A comparison of the shock front density calculated from the reconstructed data and that calculated using the point explosion model at different time delays has been done. The comparison shows quite good agreement between the model and the experimental data. Finally the reconstructed refractive index field has been used to estimate the electron number density distribution within the laser-induced plasma. The electron number density behaviour with distance from the target at different power densities and its behaviour with time are shown. The electron number densities are found to be in the order of 10 18 cm -3 and decay at a rate of 3×10 15 electrons/cm 3 ns.

  10. Developing the model of laser ablation by considering the interplay between emission and expansion of aluminum plasma

    SciTech Connect

    Rezaei, F.; Tavassoli, S. H.

    2013-01-15

    In the present study, the ablation behavior of aluminum target and its plasma radiation in noble ambient gases by a laser pulse with wavelength of 266 nm and pulse duration of 10 ns are numerically studied. A thermal model of laser ablation considering heat conduction, Euler equations, Saha-Eggert equations, Knudsen layer, mass and energy balance relations and optical shielding effects are used for calculation of plasma parameters. Effects of excitation energy on plasma expansion and its emissivity are investigated. Time and spatial-resolved plasma emission including bremsstrahlung, recombination and spectral emission at early delay times after laser irradiation is obtained. Effects of two ambient gases (He and Ar) as well as different gas pressures of 100, 300, 500, and 760 Torr on plasma expansion and its spectrum are studied. Results illustrate that at initial delay times, especially at high noble gas pressures, ionic lines have the maximum intensities, while at later times neutral lines dominate. When the pressure of ambient gas increases, a confinement of the plasma plume is predicted and the intensity of neutral lines decreases. Continuous emission increases with wavelength in both ambient gases. Spatially resolved analysis shows that an intense continuous emission is predicted next to the sample surface decreasing with distance from the latter.

  11. Tailored ablation processing of advanced biomedical hydroxyapatite by femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Ozono, K.; Obara, M.

    The micromachining of hydroxyapatite (HAp) is highly important for orthopedics and dentistry, since human bone and teeth consist mainly of HAp. We demonstrate ultrashort Ti:sapphire laser ablation of HAp, using pulse-widths of 50 fs, 500 fs, and 2 ps at a wavelength of 820 nm and at 1 kpps. The crucial medical issue is to preserve the chemical properties of the machined (ablated) surface. If the chemical properties of HAp change, the human bone or tooth cannot re-grow after laser processing. Using X-ray photoelectron spectroscopy, we observe chemical properties of HAp ablated in air. The HAp is ablated at laser fluences of 3.2 J/cm2 (6.4×1013 W/cm2 at 50 fs), 3.3 J/cm2 (6.6×1012 W/cm2 at 500 fs), and 9.6 J/cm2 (4.8×1012 W/cm2 at 2 ps), respectively. As a result it is found that the ablated surface is unchanged after laser ablation over the pulse-width range used in this experiment.

  12. Ablation of NIF Targets and Diagnostic Components by High Power Lasers and X-Rays from High Temperature Plasmas

    SciTech Connect

    Eder, D.C; Anderson, A.T.; Braun, D.G; Tobin, M.T.

    2000-04-19

    The National Ignition Facility (NIF) will consist of 192 laser beams that have a total energy of up to 1.8 MJ in the 3rd harmonic ({lambda} = 0.35 {micro}m) with the amount of 2nd harmonic and fundamental light depending on the pulse shape. Material near best focus of the 3rd harmonic light will be vaporized/ablated very rapidly, with a significant fraction of the laser energy converted into plasma x rays. Additional plasma x rays can come from imploding/igniting capsule inside Inertial Confinement Fusion (ICF) hohlraums. Material from outer portions of the target, diagnostic components, first-wall material, and optical components, are ablated by the plasma x rays. Material out to a radius of order 3 cm from target center is also exposed to a significant flux of 2nd harmonic and fundamental laser light. Ablation can accelerate the remaining material to high velocities if it has been fragmented or melted. In addition, the high velocity debris wind of the initially vaporized material pushes on the fragments/droplets and increases their velocity. The high velocity shrapnel fragments/droplets can damage the fused silica shields protecting the final optics in NIF. We discuss modeling efforts to calculate vaporization/ablation, x-ray generation, shrapnel production, and ways to mitigate damage to the shields.

  13. Highly doped p-ZnTe films and quantum well structures grown by nonequilibrium pulsed laser ablation

    SciTech Connect

    Lowndes, D.H.; Rouleau, C.M.; Budai, J.D.; Geohegan, D.B.; McCamy, J.W.

    1995-06-01

    Highly p-doped ZnTe films have been grown on semi-insulating GaAs (001) and unintentionally doped (p-type) GaSb (001) substrates by pulsed KrF (248 nm) excimer laser ablation of a ZnTe target through an N{sub 2} ambient, without the use of any assisting (DC or AC) plasma source. Free hole concentrations in the mid-10{sup 19} cm{sup {minus}3} to > 10{sup 20} cm{sup {minus}3} range have been obtained. This appears to be the first time that any wide band gap (E{sub g} {ge} 2 eV) II-VI compound (or other) semiconductor has been impurity-doped from the gas phase by pulsed-laser ablation (PLA). The maximum carrier concentrations also may be the highest obtained for ZnTe by any method thus far. Because pulsed laser deposition is inherently digital, attractive deposition rates can be combined with precise control of layer thickness in epitaxial multilayered structures. Typical deposition conditions are < 0.5 {angstrom} per laser pulse, with crystalline quality governed by tradeoffs between substrate temperature, pulse repetition rate, and the focused pulsed laser energy density. PLA`s capability for growth of very thin epitaxial layers is being exploited and studied through growth of doped heteroepitaxial quantum well structures in the nearly lattice-matched ZnTe/CdSe//GaSb(substrate) system. Results obtained from growth and characterization of heterostructures in this system will be presented.

  14. Emission features of femtosecond laser ablated carbon plasma in ambient helium

    NASA Astrophysics Data System (ADS)

    Al-Shboul, K. F.; Harilal, S. S.; Hassanein, A.

    2013-04-01

    We investigated the optical emission features of plasmas produced by 800 nm, 40 fs ultrafast laser pulses on a carbon target in the presence of ambient helium or nitrogen gases at varied pressures. Fast photography employing intensified charge coupled device, optical emission spectroscopy, and temporally spatially resolved optical time of flight emission spectroscopy were used as diagnostic tools. Spatio-temporal contours of excited neutral, ionic, as well as molecular carbon species in the plume were obtained using time of flight emission spectroscopy. These contours provided detailed account of molecular species evolution and expansion dynamics and indicate that three-body recombination is a major mechanism for carbon dimers generation in ultrafast laser ablation plumes in the presence of ambient gas. A systematic comparison of the emission features from ns and fs laser ablation carbon plumes as well as their expansion in ambient helium is also given. C2 vibrational temperatures were estimated during carbon plasma expansion with lower values in ambient helium compared to nitrogen and showed decreasing values with respect to space and ambient gas pressure.

  15. Plasma probe characteristics in low density hydrogen pulsed plasmas

    NASA Astrophysics Data System (ADS)

    Astakhov, D. I.; Goedheer, W. J.; Lee, C. J.; Ivanov, V. V.; Krivtsun, V. M.; Zotovich, A. I.; Zyryanov, S. M.; Lopaev, D. V.; Bijkerk, F.

    2015-10-01

    Probe theories are only applicable in the regime where the probe’s perturbation of the plasma can be neglected. However, it is not always possible to know, a priori, that a particular probe theory can be successfully applied, especially in low density plasmas. This is especially difficult in the case of transient, low density plasmas. Here, we applied probe diagnostics in combination with a 2D particle-in-cell model, to an experiment with a pulsed low density hydrogen plasma. The calculations took into account the full chamber geometry, including the plasma probe as an electrode in the chamber. It was found that the simulations reproduce the time evolution of the probe IV characteristics with good accuracy. The disagreement between the simulated and probe measured plasma density is attributed to the limited applicability of probe theory to measurements of low density pulsed plasmas on a similarly short time scale as investigated here. Indeed, in the case studied here, probe measurements would lead to, either a large overestimate, or underestimate of the plasma density, depending on the chosen probe theory. In contrast, the simulations of the plasma evolution and the probe characteristics do not suffer from such strict applicability limits. These studies show that probe theory cannot be justified through probe measurements. However, limiting cases of probe theories can be used to estimate upper and lower bounds on plasma densities. These theories include and neglect orbital motion, respectively, with different collisional terms leading to intermediate estimates.

  16. Ablation and nanostructuring of metals by femtosecond laser pulses

    SciTech Connect

    Ashitkov, S I; Komarov, P S; Ovchinnikov, A V; Struleva, E V; Agranat, M B; Zhakhovskii, V V; Inogamov, N A

    2014-06-30

    Using an interferometric continuous monitoring technique, we have investigated the motion of the surface of an aluminium target in the case of femtosecond laser ablation at picosecond time delays relative to the instant of laser exposure. Measurements of the temporal target dispersion dynamics, molecular dynamics simulation results and the morphology of the ablation crater have demonstrated a thermomechanical (spall) nature of the disruption of the condensed phase due to the cavitation-driven formation and growth of vapour phase nuclei upon melt expansion, followed by the formation of surface nanostructures upon melt solidification. The tensile strength of heated aluminium in a condensed state has been determined experimentally at an expansion rate of ∼10{sup 9} s{sup -1}. (extreme light fields and their applications)

  17. Multi-diagnostic comparison of femtosecond and nanosecond pulsed laser plasmas

    NASA Astrophysics Data System (ADS)

    Zhang, Z.; VanRompay, P. A.; Nees, J. A.; Pronko, P. P.

    2002-09-01

    Understanding and fully characterizing highly dynamic and rapidly streaming laser ablation plasmas requires multiple techniques for monitoring effects at different stages. By combining multiple diagnostic methods, it is possible to analyze the broad time window over which these ablation plasmas develop and to learn more about the related physical processes that occur. Two laser sources, an 80 fs Ti:Sapphire laser (780 nm) and a 6 ns Nd:YAG laser (1.06 mum), are used in this work in order to compare pulse duration effects at similar wavelengths. Characteristics of the plasma produced by these two lasers are compared under conditions of comparable ablation flux. Results are presented involving correlation of time-resolved Langmuir probe data and electrostatic energy analysis for aluminum plasmas as a representative investigation for metallic systems. In addition, continuous-wave refractive index laser beam deflection is used to characterize the plasma and hot gas generated from boron nitride targets in terms of their ion and neutral atom densities. A self-similarity plasma expansion model is used to analyze the plumes under various conditions. Fundamental data obtained in this way can be relevant to laser micro-machining, laser induced breakdown spectroscopy, and pulsed laser deposition.

  18. Surface roughness and wettability of dentin ablated with ultrashort pulsed laser

    NASA Astrophysics Data System (ADS)

    Liu, Jing; Lü, Peijun; Sun, Yuchun; Wang, Yong

    2015-05-01

    The aim of this study was to evaluate the surface roughness and wettability of dentin following ultrashort pulsed laser ablation with different levels of fluence and pulse overlap (PO). Twenty-five extracted human teeth crowns were cut longitudinally into slices of approximately 1.5-mm thick and randomly divided into nine groups of five. Samples in groups 1 to 8 were ablated with an ultrashort pulsed laser through a galvanometric scanning system. Samples in group 9 were prepared using a mechanical rotary instrument. The surface roughness of samples from each group was then measured using a three-dimensional profile measurement laser microscope, and wettability was evaluated by measuring the contact angle of a drop of water on the prepared dentin surface using an optical contact angle measuring device. The results showed that both laser fluence and PO had an effect on dentin surface roughness. Specifically, a higher PO decreased dentin surface roughness and reduced the effect of high-laser fluence on decreasing the surface roughness in some groups. Furthermore, all ablated dentin showed a contact angle of approximately 0 deg, meaning that laser ablation significantly improved wettability. Adjustment of ultrashort pulsed laser parameters can, therefore, significantly alter dentin surface roughness and wettability.

  19. Ultra-short pulsed laser tissue ablation using focused laser beam

    NASA Astrophysics Data System (ADS)

    Jaunich, Megan K.; Raje, Shreya; Mitra, Kunal; Grace, Michael S.; Fahey, Molly; Spooner, Greg

    2008-02-01

    Short pulse lasers are used for a variety of therapeutic applications in medicine. Recently ultra-short pulse lasers have gained prominence due to the reduction in collateral thermal damage to surrounding healthy tissue during tissue ablation. In this paper, ultra-short pulsed laser ablation of mouse skin tissue is analyzed by assessing the extent of damage produced due to focused laser beam irradiation. The laser used for this study is a fiber-based desktop laser (Raydiance, Inc.) having a wavelength of 1552 nm and a pulse width of 1.3 ps. The laser beam is focused on the sample surface to a spot size on the order of 10 microns, thus producing high peak intensity necessary for precise clean ablation. A parametric study is performed on in vitro mouse tissue specimens and live anaesthetized mice with mammary tumors through variation of laser parameters such as time-averaged laser power, repetition rate, laser scanning rate and irradiation time. Radial temperature distribution is measured using thermal camera to analyze the heat affected zone. Temperature measurements are performed to assess the peak temperature rise attained during ablation. A detailed histological study is performed using frozen section technique to observe the nature and extent of laser-induced damages.

  20. Bone tissue heating and ablation by short and ultrashort laser pulses

    NASA Astrophysics Data System (ADS)

    Letfullin, Renat R.; Rice, Colin E. W.; George, Thomas F.

    2010-02-01

    Biological hard tissues, such as those found in bone and teeth, are complex tissues that build a strong mineral structure over an organic matrix framework. The laser-matter interaction for bone hard tissues holds great interest to laser surgery and laser dentistry; the use of short/ultrashort pulses, in particular, shows interesting behaviors not seen in continuous wave lasers. High laser energy densities in ultrashort pulses can be focused on a small irradiated surface (spot diameter is 10-50 μm) leading to rapid temperature rise and thermal ablation of the bone tissue. Ultrashort pulses, specifically those in the picosecond and femtosecond ranges, impose several challenges in modeling bone tissue response. In the present paper we perform time-dependent thermal simulations of short and ultrashort pulse laser-bone interactions in singlepulse and multipulse (set of ultrashort pulses) modes of laser heating. A comparative analysis for both radiation modes is discussed for laser heating of different types of the solid bone on the nanosecond, picosecond and femtosecond time scales. It is shown that ultrashort laser pulses with high energy densities can ablate bone tissue without heating tissues bordering the ablation creator. This reaction is particularly desirable as heat accumulation and thermal damage are the main factors affecting tissue regrowth rates, and thus patient recovery times.

  1. Laser-induced back-ablation of aluminum thin films using picosecond laser pulses

    SciTech Connect

    BULLOCK, A B

    1999-05-26

    Experiments were performed to understand laser-induced back-ablation of Al film targets with picosecond laser pulses. Al films deposited on the back surface of BK-7 substrates are ablated by picosecond laser pulses propagating into the Al film through the substrate. The ablated Al plume is transversely probed by a time-delayed, two-color sub-picoseond (500 fs) pulse, and this probe is then used to produce self-referencing interferograms and shadowgraphs of the Al plume in flight. Optical emission from the Al target due to LIBA is directed into a time-integrated grating spectrometer, and a time-integrating CCD camera records images of the Al plume emission. Ablated Al plumes are also redeposited on to receiving substrates. A post-experimental study of the Al target and recollected deposit characteristics was also done using optical microscopy, interferometry, and profilometry. In this high laser intensity regime, laser-induced substrate ionization and damage strongly limits transmitted laser fluence through the substrate above a threshold fluence. The threshold fluence for this ionization-based transmission limit in the substrate is dependent on the duration of the incident pulse. The substrate ionization can be used as a dynamic control of both transmitted spatial pulse profile and ablated Al plume shape. The efficiency of laser energy transfer between the laser pulse incident on the Al film and the ablated Al plume is estimated to be of order 5% and is a weak function of laser pulsewidth. The Al plume is highly directed. Low plume divergence ({theta}{sub divergence} < 5{sup o}) shows the ablated plume temperature to be very low at long time delays ( T << 0.5 eV at delays of 255 ns). Spectroscopic observations and calculations indicate that, in early time (t < 100 ps), the Al film region near the substrate/metal interface is at temperatures of order 0.5 eV. Interferograms of Al plumes produced with 0.1 {micro}m films show these plumes to be of high neutral atom

  2. Wavelength Effects In Femtosecond Pulsed Laser Ablation And Deposition

    SciTech Connect

    Castillejo, Marta; Nalda, Rebeca de; Oujja, Mohamed; Sanz, Mikel

    2010-10-08

    Ultrafast pulsed laser irradiation of solid materials is highly attractive for the micro-and nanostructuring of substrates and for the fabrication of nanostructured deposits. Femtosecond laser pulses promote efficient material removal with reduced heat transfer and high deposition rates of nanometer scale particles free of microscopic particulates. Most of the studies to date have been performed with light pulses centered around the peak wavelength of the Titanium:Sapphire laser, around 800 nm. Analysis of the process over a broader range of wavelengths can provide important information about the processes involved and serve as experimental tests for advanced theoretical models. We report on our current investigations on the effect that laser wavelength of femtosecond pulses has on the superficial nanostructuring induced on biopolymer substrates, and on the characteristics of nanostructured deposits grown by pulsed laser deposition from semiconductor targets.

  3. Effect of Twisted Fiber Anisotropy in Cardiac Tissue on Ablation with Pulsed Electric Fields

    PubMed Central

    Xie, Fei; Zemlin, Christian W.

    2016-01-01

    Background Ablation of cardiac tissue with pulsed electric fields is a promising alternative to current thermal ablation methods, and it critically depends on the electric field distribution in the heart. Methods We developed a model that incorporates the twisted anisotropy of cardiac tissue and computed the electric field distribution in the tissue. We also performed experiments in rabbit ventricles to validate our model. We find that the model agrees well with the experimentally determined ablation volume if we assume that all tissue that is exposed to a field greater than 3 kV/cm is ablated. In our numerical analysis, we considered how tissue thickness, degree of anisotropy, and electrode configuration affect the geometry of the ablated volume. We considered two electrode configurations: two parallel needles inserted into the myocardium (“penetrating needles” configuration) and one circular electrode each on epi- and endocardium, opposing each other (“epi-endo” configuration). Results For thick tissues (10 mm) and moderate anisotropy ratio (a = 2), we find that the geometry of the ablated volume is almost unaffected by twisted anisotropy, i.e. it is approximately translationally symmetric from epi- to endocardium, for both electrode configurations. Higher anisotropy ratio (a = 10) leads to substantial variation in ablation width across the wall; these variations were more pronounced for the penetrating needle configuration than for the epi-endo configuration. For thinner tissues (4 mm, typical for human atria) and higher anisotropy ratio (a = 10), the epi-endo configuration yielded approximately translationally symmetric ablation volumes, while the penetrating electrodes configuration was much more sensitive to fiber twist. Conclusions These results suggest that the epi-endo configuration will be reliable for ablation of atrial fibrillation, independently of fiber orientation, while the penetrating electrode configuration may experience problems when the

  4. Plasma mirrors for short pulse lasers

    SciTech Connect

    Yanovksy, V.P.; Perry, M.D.; Brown, C.G.; Feit, M.D.; Rubenchik, A.

    1997-06-11

    We show experimentally and theoretically that plasmas created by a sufficiently (1014 1015 2 short (<500 fs) intense W/cm ) laser pulse on the surface of dielectric material act as nearly perfect mirrors: reflecting p to 90% of the incident radiation with a wavefront quality equal to that of the initial solid surface.

  5. Deposition of Fluorinated Diamond-Like-Carbon Films by Exposure of Electrothermal Pulsed Plasmas

    NASA Astrophysics Data System (ADS)

    Kimura, Takashi; Iida, Masayasu

    2011-08-01

    Thin amorphous carbon films are deposited on silicon substrates by exposure to pulsed plasmas where the feed gas is mainly generated from the ablation of an insulator. An electrothermal pulsed plasma thruster with a discharge room in an insulator rod is used as the pulsed plasma for the ablation of the insulator, and the material of the insulator rod is poly(tetrafluoroethylene) (PTFE). The pulsed plasma, in which the estimated electron density is on the order of 1022-1023 m-3, is generated by the stored energy in the capacitor. The deposition rate, which depends on the stored energy, is lower than 1 nm per pulse in our experiment. The maximum hardness measured using a nanoindenter is about 7 GPa at a stored energy of about 2.7 J, beyond which the hardness of the films decreases with the increase in stored energy. Raman spectroscopy is also carried out to examine the formation of fluorinated diamond-like carbon films. In addition, the influence of dilution gas on the properties of the deposited films is also investigated.

  6. Time-resolved investigations of the non-thermal ablation process of graphite induced by femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Kalupka, C.; Finger, J.; Reininghaus, M.

    2016-04-01

    We report on the in-situ analysis of the ablation dynamics of the, so-called, laser induced non-thermal ablation process of graphite. A highly oriented pyrolytic graphite is excited by femtosecond laser pulses with fluences below the classic thermal ablation threshold. The ablation dynamics are investigated by axial pump-probe reflection measurements, transversal pump-probe shadowgraphy, and time-resolved transversal emission photography. The combination of the applied analysis methods allows for a continuous and detailed time-resolved observation of the non-thermal ablation dynamics from several picoseconds up to 180 ns. Formation of large, μm-sized particles takes place within the first 3.5 ns after irradiation. The following propagation of ablation products and the shock wave front are tracked by transversal shadowgraphy up to 16 ns. The comparison of ablation dynamics of different fluences by emission photography reveals thermal ablation products even for non-thermal fluences.

  7. Plasma-assisted laser ablation of tungsten: Reduction in ablation power threshold due to bursting of holes/bubbles

    SciTech Connect

    Kajita, Shin; Ohno, Noriyasu; Takamura, Shuichi; Sakaguchi, Wataru; Nishijima, Dai

    2007-12-24

    Nanosecond laser ablation of tungsten (W) exposed to helium plasma is investigated using optical emission spectroscopy. Submicrometer-sized holes/bubbles are formed on the surface of W when it was exposed to the helium plasma at a sufficiently high temperature (> or approx. 1500-1600 K). The emissions from a virgin W (before the helium plasma irradiation) cannot be detected when the fluence is <1 J/cm{sup 2}; however, the threshold fluence for the detection of neutral W emission after it was exposed to the helium plasma is {approx}0.2 J/cm{sup 2}. The physical mechanism of laser-induced bursting of holes/bubbles is proposed for achieving a significant reduction in ablation power threshold.

  8. The effect of ultrafast laser wavelength on ablation properties and implications on sample introduction in inductively coupled plasma mass spectrometry

    PubMed Central

    LaHaye, N. L.; Harilal, S. S.; Diwakar, P. K.; Hassanein, A.; Kulkarni, P.

    2015-01-01

    We investigated the role of femtosecond (fs) laser wavelength on laser ablation (LA) and its relation to laser generated aerosol counts and particle distribution, inductively coupled plasma-mass spectrometry (ICP-MS) signal intensity, detection limits, and elemental fractionation. Four different NIST standard reference materials (610, 613, 615, and 616) were ablated using 400 nm and 800 nm fs laser pulses to study the effect of wavelength on laser ablation rate, accuracy, precision, and fractionation. Our results show that the detection limits are lower for 400 nm laser excitation than 800 nm laser excitation at lower laser energies but approximately equal at higher energies. Ablation threshold was also found to be lower for 400 nm than 800 nm laser excitation. Particle size distributions are very similar for 400 nm and 800 nm wavelengths; however, they differ significantly in counts at similar laser fluence levels. This study concludes that 400 nm LA is more beneficial for sample introduction in ICP-MS, particularly when lower laser energies are to be used for ablation. PMID:26640294

  9. The effect of ultrafast laser wavelength on ablation properties and implications on sample introduction in inductively coupled plasma mass spectrometry

    SciTech Connect

    LaHaye, N. L.; Harilal, S. S.; Diwakar, P. K.; Hassanein, A.; Kulkarni, P.

    2013-07-14

    We investigated the role of femtosecond (fs) laser wavelength on laser ablation (LA) and its relation to laser generated aerosol counts and particle distribution, inductively coupled plasma-mass spectrometry (ICP-MS) signal intensity, detection limits, and elemental fractionation. Four different NIST standard reference materials (610, 613, 615, and 616) were ablated using 400 nm and 800 nm fs laser pulses to study the effect of wavelength on laser ablation rate, accuracy, precision, and fractionation. Our results show that the detection limits are lower for 400 nm laser excitation than 800 nm laser excitation at lower laser energies but approximately equal at higher energies. Ablation threshold was also found to be lower for 400 nm than 800 nm laser excitation. Particle size distributions are very similar for 400 nm and 800 nm wavelengths; however, they differ significantly in counts at similar laser fluence levels. This study concludes that 400 nm LA is more beneficial for sample introduction in ICP-MS, particularly when lower laser energies are to be used for ablation.

  10. Synthesis of silver nanoparticles by laser ablation in ethanol: A pulsed photoacoustic study

    NASA Astrophysics Data System (ADS)

    Valverde-Alva, M. A.; García-Fernández, T.; Villagrán-Muniz, M.; Sánchez-Aké, C.; Castañeda-Guzmán, R.; Esparza-Alegría, E.; Sánchez-Valdés, C. F.; Llamazares, J. L. Sánchez; Herrera, C. E. Márquez

    2015-11-01

    The pulsed photoacoustic (PA) technique was used to study the synthesis by laser ablation of silver nanoparticles (Ag-NPs) in ethanol. PA technique allowed to determine the production rate per laser pulse and concentration of synthesized Ag-NPs. The samples were produced by using a pulsed Nd:YAG laser with 1064 nm of wavelength and 7 ns of pulse duration. The laser pulse energy varied from 10 to 100 mJ. Transmission electron microscopy micrographs demonstrated that the obtained nanoparticles were spherical with an average size close to 10 nm. The absorption spectra of the colloids showed a plasmon absorption peak around 400 nm. The PA analyses showed a significant reduction of the production rate of Ag-NPs during the first hundreds of laser pulses. For a higher number of pulses this rate was kept almost constant. Finally, we found that the root mean square (RMS) value of the PA signal was proportional to the laser pulse fluence on the target surface. Thus PA technique was useful to monitor the ablation process.

  11. A unified model to determine the energy partitioning between target and plasma in nanosecond laser ablation of silicon

    SciTech Connect

    Galasso, G.; Kaltenbacher, M.; Tomaselli, A.; Scarpa, D.

    2015-03-28

    In semiconductor industry, pulsed nanosecond lasers are widely applied for the separation of silicon wafers. Here, the high intensities employed activate a cascade of complex multi-physical and multi-phase mechanisms, which finally result in the formation of a laser induced plasma, shielding the target from the incoming laser beam. Such induced plasma plume, by preventing the laser to effectively reach the target, reduces the overall efficiency and controllability of the ablation process. Modelling can be a useful tool in the optimization of industrial laser applications, allowing a deeper understanding of the way the laser energy distributes between target and induced plasma. Nevertheless, the highly multi-physical character of laser ablation poses serious challenges on the implementation of the various mechanisms underlying the process within a common modelling framework. A novel strategy is here proposed in order to simulate in a simplified, yet physically consistent way, a typical industrial application as laser ablation of silicon wafers. Reasonable agreement with experimental findings is obtained. Three fundamental mechanisms have been identified as the main factors influencing the accuracy of the numerical predictions: the transition from evaporative to volumetric mass removal occurring at critical temperature, the collisional and radiative processes underlying the initial plasma formation stage and the increased impact of the liquid ejection mechanism when a sub-millimeter laser footprint is used.

  12. A unified model to determine the energy partitioning between target and plasma in nanosecond laser ablation of silicon

    NASA Astrophysics Data System (ADS)

    Galasso, G.; Kaltenbacher, M.; Tomaselli, A.; Scarpa, D.

    2015-03-01

    In semiconductor industry, pulsed nanosecond lasers are widely applied for the separation of silicon wafers. Here, the high intensities employed activate a cascade of complex multi-physical and multi-phase mechanisms, which finally result in the formation of a laser induced plasma, shielding the target from the incoming laser beam. Such induced plasma plume, by preventing the laser to effectively reach the target, reduces the overall efficiency and controllability of the ablation process. Modelling can be a useful tool in the optimization of industrial laser applications, allowing a deeper understanding of the way the laser energy distributes between target and induced plasma. Nevertheless, the highly multi-physical character of laser ablation poses serious challenges on the implementation of the various mechanisms underlying the process within a common modelling framework. A novel strategy is here proposed in order to simulate in a simplified, yet physically consistent way, a typical industrial application as laser ablation of silicon wafers. Reasonable agreement with experimental findings is obtained. Three fundamental mechanisms have been identified as the main factors influencing the accuracy of the numerical predictions: the transition from evaporative to volumetric mass removal occurring at critical temperature, the collisional and radiative processes underlying the initial plasma formation stage and the increased impact of the liquid ejection mechanism when a sub-millimeter laser footprint is used.

  13. Powerful laser pulse absorption in partly homogenized foam plasma

    NASA Astrophysics Data System (ADS)

    Cipriani, M.; Gus'kov, S. Yu.; De Angelis, R.; Andreoli, P.; Consoli, F.; Cristofari, G.; Di Giorgio, G.; Ingenito, F.; Rupasov, A. A.

    2016-03-01

    The internal volume structure of a porous medium of light elements determines unique features of the absorption mechanism of laser radiation; the characteristics of relaxation and transport processes in the produced plasma are affected as well. Porous materials with an average density larger than the critical density have a central role in enhancing the pressure produced during the ablation by the laser pulse; this pressure can exceed the one produced by target direct irradiation. The problem of the absorption of powerful laser radiation in a porous material is examined both analytically and numerically. The behavior of the medium during the process of pore filling in the heated region is described by a model of viscous homogenization. An expression describing the time and space dependence of the absorption coefficient of laser radiation is therefore obtained from the model. A numerical investigation of the absorption of a nanosecond laser pulse is performed within the present model. In the context of numerical calculations, porous media with an average density larger than the critical density of the laser-produced plasma are considered. Preliminary results about the inclusion of the developed absorption model into an hydrodynamic code are presented.

  14. Low electron temperature in ablating materials formed by picosecond soft x-ray laser pulses

    NASA Astrophysics Data System (ADS)

    Ishino, Masahiko; Hasegawa, Noboru; Nishikino, Masaharu; Pikuz, Tatiana; Skobelev, Igor; Faenov, Anatoly; Inogamov, Nail; Kawachi, Tetsuya; Yamagiwa, Mitsuru

    2015-09-01

    To study the ablation process induced by the soft x-ray laser pulse, we investigated the electron temperature of the ablating material. Focused soft x-ray laser pulses having a wavelength of 13.9 nm and duration of 7 ps were irradiated onto the LiF, Al, and Cu surfaces, and we observed the optical emission from the surfaces by use of an optical camera. On sample surfaces, we could confirm damage structures, but no emission signal in the visible spectral range during ablation could be observed. Then, we estimated the electron temperature in the ablating matter. To consider the radiation from a heated layer, we supposed a black-body radiator as an object. The calculation result was that the electron temperature was estimated to be lower than 1 eV and the process duration was shorter than 1000 ps. The theoretical model calculation suggests the spallative ablation for the interaction between the soft x-ray laser and materials. The driving force for the spallation is an increasing pressure appearing in the heated layer, and the change of the surface is considered to be due to a splash of a molten layer. The model calculation predicts that the soft x-ray laser with the fluence around the ablation threshold can create an electron temperature around 1 eV in a material. The experimental result is in good accordance with the theoretical prediction. Our investigation implies that the spallative ablation occurs in the low electron temperature region of a non-equilibrium state of warm dense matter.

  15. Generation of Al nanoparticles via ablation of bulk Al in liquids with short laser pulses.

    PubMed

    Stratakis, Emmanuel; Barberoglou, Marios; Fotakis, Costas; Viau, Guillaume; Garcia, Cecile; Shafeev, Georgy A

    2009-07-20

    Highly stable aluminum nanoparticles (NPs) are generated via ablation of bulk Al in ethanol using either femtosecond (fs) or picosecond (ps) laser sources. The colloidal NPs solutions obtained with fs pulses exhibit a yellow coloration and show an increased optical absorption between 300 and 400 nm, tentatively assigned to the plasmon resonance of nanosized Al. The corresponding solutions after ps ablation are gray colored and opalescent. The average size of the NPs formed ranges from 20 nm for the fs case to 60 nm for the ps case, while a narrower distribution is obtained using the shorter pulses. High Resolution Transmission Electron Microscopy (HRTEM) studies indicate that the NPs are mostly amorphous with single crystalline inclusions. Al NPs generated with short laser pulses slowly react with air oxygen due to the presence of a native oxide cladding, which efficiently passivates their surface against further oxidation. PMID:19654669

  16. Pulsed laser ablation of binary semiconductors: mechanisms of vaporisation and cluster formation

    SciTech Connect

    Bulgakov, A V; Evtushenko, A B; Shukhov, Yu G; Ozerov, I; Marin, W

    2010-12-29

    Formation of small clusters during pulsed ablation of two binary semiconductors, zinc oxide and indium phosphide, in vacuum by UV, visible, and IR laser radiation is comparatively studied. The irradiation conditions favourable for generation of neutral and charged Zn{sub n}O{sub m} and In{sub n}P{sub m} clusters of different stoichiometry in the ablation products are found. The size and composition of the clusters, their expansion dynamics and reactivity are analysed by time-of-flight mass spectrometry. A particular attention is paid to the mechanisms of ZnO and InP ablation as a function of laser fluence, with the use of different ablation models. It is established that ZnO evapourates congruently in a wide range of irradiation conditions, while InP ablation leads to enrichment of the target surface with indium. It is shown that this radically different character of semiconductor ablation determines the composition of the nanostructures formed: zinc oxide clusters are mainly stoichiometric, whereas In{sub n}P{sub m} particles are significantly enriched with indium. (photonics and nanotechnology)

  17. Submicron surface patterning by laser ablation with short UV pulses using a proximity phase mask setup

    SciTech Connect

    Borchers, B.; Bekesi, J.; Simon, P.; Ihlemann, J.

    2010-03-15

    A new approach for the generation of large-area periodic surface structures on different materials, like polymers and semiconductors, by direct laser ablation is presented. The surfaces were illuminated with the interference pattern emerging in close proximity behind a laser irradiated phase mask. In the experiments, nanosecond and picosecond laser pulses at 248 nm were applied. To prevent contamination or damage of the phase mask caused by the ablated material, the mask is protected by a thin water film or a thin quartz plate. In addition we present a technique to eliminate a lateral variation of the generated structures due to insufficient alignment precision of the workpiece.

  18. Coblation technology: plasma-mediated ablation for otolaryngology applications

    NASA Astrophysics Data System (ADS)

    Woloszko, Jean; Gilbride, Charles

    2000-05-01

    Coblation is a unique method of delivering radio frequency energy to soft tissue for applications in Otolaryngology (ENT). Using radio frequency in a bipolar mode with a conductive solution, such as saline, Coblation energizes the ions in the saline to form a small plasma field. The plasma has enough energy to break the tissue's molecular bonds, creating an ablative path. The thermal effect of this process is approximately 45 - 85 degrees Celsius, significantly lower than traditional radio-frequency techniques. Coblation has been used for Otolaryngological applications such as Uvulopalatopharyngoplasty (UPPP), tonsillectomy, turbinate reduction, palate reduction, base of tongue reduction and various Head and Neck cancer procedures. The decreased thermal effect of Coblation anecdotally has led to less pain and faster recovery for cases where tissue is excised. In cases where Coblation is applied submucosally to reduce tissue volume (inferior turbinate, soft palate), the immediate volume reduction may lead to immediate clinical benefits for the patient. Coblation is currently being tested in various clinical studies to document the benefits for otolaryngological applications.

  19. Modeling CO{sub 2} laser ablation impulse of polymers in vapor and plasma regimes

    SciTech Connect

    Sinko, John E.; Phipps, Claude R.

    2009-09-28

    An improved model for CO{sub 2} laser ablation impulse in polyoxymethylene and similar polymers is presented that describes the transition effects from the onset of vaporization to the plasma regime in a continuous fashion. Several predictions are made for ablation behavior.

  20. Population inversions in ablation plasmas generated by intense electron beams

    NASA Astrophysics Data System (ADS)

    Gilgenbach, R. M.; Kammash, T.; Brake, M. L.

    1988-11-01

    Experiments during the past three years have concerned the generation and spectroscopic study of electron beam-driven carbon plasmas in order to explore the production of optical and ultraviolet radiation from nonequilibrium populations. The output of MELBA (Michigan Electron Long Beam Accelerator), has been connected to an electron beam diode consisting of an aluminum (or brass) cathode stalk and a carbon anode. Magnetic field coils have been designed, procured, and utilized to focus the electron beam. A side viewing port permitted spectroscopic diagnostics to view across the surface of the anode. Spectroscopic diagnosis has been performed using a 1 m spectrograph capable of operation from the vacuum ultraviolet through the visible. This spectrograph is coupled to a 1024 channel optical multichannel analyzer. Spectra taken during the initial 400 ns period of the e-beam pulse showed a low effective charge plasma with primarily molecular components (C2, CH) as well as atomic hydrogen and singly ionized carbon (CII). When the generator pulse was crowbarred after the first 400 ns, the spectra revealed a continuation of the low charge state plasma.

  1. Low- and high-order harmonic generation in the extended plasmas produced by laser ablation of zinc and manganese targets

    SciTech Connect

    Ganeev, R. A.; Baba, M.; Suzuki, M.; Yoneya, S.; Kuroda, H.

    2014-12-28

    The systematic studies of the harmonic generation of ultrashort laser pulses in the 5-mm-long Zn and Mn plasmas (i.e., application of nanosecond, picosecond, and femtosecond pulses for ablation, comparison of harmonic generation from atomic, ionic, and cluster-contained species of plasma, variation of plasma length, two-color pump of plasmas, etc.) are presented. The conversion efficiency of the 11th–19th harmonics generated in the Zn plasma was ∼5 × 10{sup −5}. The role of the ionic resonances of Zn near the 9th and 10th harmonics on the enhancement of harmonics is discussed. The enhancement of harmonics was also analyzed using the two-color pump of extended plasmas, which showed similar intensities of the odd and even harmonics along the whole range of generation. The harmonics up to the 107th order were demonstrated in the case of manganese plasma. The comparison of harmonic generation in the 5-mm-long and commonly used short (≤0.5 mm) plasma plumes showed the advanced properties of extended media.

  2. A new sealed RF-excited CO2 laser for enamel ablation operating at 9.4-μm with a pulse duration of 26-μs

    PubMed Central

    Chan, Kenneth H.; Jew, Jamison M.; Fried, Daniel

    2016-01-01

    Several studies over the past 20 years have shown that carbon dioxide lasers operating at wavelengths between 9.3 and 9.6-μm with pulse durations near 20-μs are ideal for hard tissue ablation. Those wavelengths are coincident with the peak absorption of the mineral phase. The pulse duration is close to the thermal relaxation time of the deposited energy of a few microseconds which is short enough to minimize peripheral thermal damage and long enough to minimize plasma shielding effects to allow efficient ablation at practical rates. The desired pulse duration near 20-μs has been difficult to achieve since it is too long for transverse excited atmospheric pressure (TEA) lasers and too short for radio-frequency (RF) excited lasers for efficient operation. Recently, Coherent Inc. (Santa Clara, CA) developed the Diamond J5-V laser for microvia drilling which can produce laser pulses greater than 100-mJ in energy at 9.4-μm with a pulse duration of 26-μs and it can achieve pulse repetition rates of 3 KHz. We report the first results using this laser to ablate dental enamel. Efficient ablation of dental enamel is possible at rates exceeding 50-μm per pulse. This laser is ideally suited for the selective ablation of carious lesions. PMID:27006521

  3. Pulsed Plasma Treatment of Magnesium Diboride System for Formation of Superconducting Regions

    SciTech Connect

    Piekoszewski, J.; Stanislawski, J.; Skladnik-Sadowska, E.; Barlak, M.

    2006-01-15

    The experiments to synthesis thin MgB2 inter-metallic compound with the use of ion implantation and plasma pulse treatment are presented. Polycrystalline magnesium was implanted with 5x1018cm-2 of 100 keV boron ions and next treated with hydrogen plasma pulses of duration of about 1{mu}s and fluence between 1 and 3 J/cm2. Optical diagnostics of Mg plasma plumes ablated during pulse duration was performed prior to synthesize process. Superconducting properties were examined by magnetically modulated microwave absorption (MMMA). The main result consists in observation of MMMA hysteresis loop demonstrating the existence of superconducting regions with transition temperatures Tc as high as 32K. However, the zero-resistance effect has not been obtained due to incomplete global connectivity between the superconducting regions.

  4. Plasma and Shock Generation by Indirect Laser Pulse Action

    SciTech Connect

    Kasperczuk, A.; Borodziuk, S.; Pisarczyk, T.; Demchenko, N. N.; Gus'kov, S. Yu.; Jungwirth, K.; Kralikova, B.; Krousky, E.; Masek, K.; Pfeifer, M.; Rohlena, K.; Rozanov, V. B.; Skala, J.; Ullschmied, J.; Kalal, M.; Limpouch, J.; Pisarczyk, P.

    2006-01-15

    In the paper the results of our experiment with flyer disks, accelerated to high velocities by the PALS iodine laser and subsequently creating craters when hitting massive targets , are presented. We have carried out experiments with the double targets consisted of a disk placed in front of a massive target part at distances of either 200 or 500 {mu}m. Both elements of the targets were made of Al. The following disk irradiation conditions were used: laser energy of 130 J, laser wavelength of 1.315 {mu}m, pulse duration of 0.4 ns, and laser spot diameter of 250 {mu}m. To measure some plasma parameters and accelerated disk velocity a three frame interferometric system was used. Efficiency of crater creation by a disk impact was determined from the crater parameters, which were obtained by means of a crater replica technique. The experimental results concern two main stages: (a) ablative plasma generation and disk acceleration and (b) disk impact and crater creation. Spatial density distributions at different moments of plasma generation and expansion are shown. Discussion of the experimental results on the basis of a 2-D theoretical model of the laser -- solid target interaction is carried out.

  5. Characterization of Carbon Plasma Evolution Using Laser Ablation TOF Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Zhang, Lei; Feng, Chunlei; Xiao, Qingmei; Hai, Ran; Ding, Hongbin

    2015-11-01

    In this work, a time-of-flight (TOF) mass spectrometer has been used to investigate the distribution of intermediate species and formation process of carbon clusters. The graphite sample was ablated by Nd:YAG laser (532 nm and 1064 nm). The results indicate that the maximum size distribution shifted towards small cluster ions as the laser fluence increased, which happened because of the fragmentation of larger clusters in the hot plume. The temporal evolution of ions was measured by varying the delay time of the ion extraction pulse with respect to the laser irradiation, which was used to provide distribution information of the species in the ablated plasma plume. When the laser fluence decreased, the yield of all of the clusters obviously dropped. supported by the National Magnetic Confinement Fusion Science Program of China (No. 2013GB109005) and National Natural Science Foundation of China (No. 11175035), Chinesisch-Deutsches Forschungs Project (GZ768), the Fundamental Research Funds for the Central Universities of China (Nos. DUT12ZD(G)01, DUT14ZD(G)04) and MMLab Research Project (DP1051208)

  6. Pulsed Radiofrequency Ablation Under Ultrasound Guidance for Huge Neuroma

    PubMed Central

    Jung, Il; Lee, Chang Hee; Kim, Se Hun; Kim, Jin Sun; Yoo, Byoung Woo

    2014-01-01

    Amputation neuroma can cause very serious, intractable pain. Many treatment modalities are suggested for painful neuroma. Pharmacologic treatment shows a limited effect on eliminating the pain, and surgical treatment has a high recurrence rate. We applied pulsed radiofrequency treatment at the neuroma stalk under ultrasonography guidance. The long-term outcome was very successful, prompting us to report this case. PMID:25031817

  7. The thermoelastic basis of short pulsed laser ablation of biological tissue.

    PubMed Central

    Itzkan, I; Albagli, D; Dark, M L; Perelman, L T; von Rosenberg, C; Feld, M S

    1995-01-01

    Strong evidence that short-pulse laser ablation of biological tissues is a photomechanical process is presented. A full three-dimensional, time-dependent solution to the thermoelastic wave equation is compared to the results of experiments using an interferometric surface monitor to measure thermoelastic expansion. Agreement is excellent for calibrations performed on glass and on acrylic at low laser fluences. For cortical bone, the measurements agree well with the theoretical predictions once optical scattering is included. The theory predicts the presence of the tensile stresses necessary to rupture the tissue during photomechanical ablation. The technique is also used to monitor the ablation event both before and after material is ejected. PMID:7892208

  8. Processing condition influence on the characteristics of gold nanoparticles produced by pulsed laser ablation in liquids

    NASA Astrophysics Data System (ADS)

    Nikov, R. G.; Nikolov, A. S.; Nedyalkov, N. N.; Atanasov, P. A.; Alexandrov, M. T.; Karashanova, D. B.

    2013-06-01

    A study is presented of Au nanoparticles (NPs) created by nanosecond pulsed laser ablation of a solid target in double distilled water. The influence was examined of the laser wavelength on the size, shape and optical properties of the resulting NPs. Three different wavelengths: the fundamental (λ = 1064 nm), second (λSHG = 532) and third (λTHG = 355) harmonic of a Nd:YAG laser at the same fluence were utilized to produce various colloids. Ablation at the wavelength of 532 nm was investigated in more detail to reveal the influence of self-absorption by the already created NPs on their characteristics. The colloid produced was irradiated by λirrad = 532 nm (laser energy 40 mJ) at different times up to 25 min after the end of ablation. The initial structure of welded NPs forming wires was modified. Transmission electron microscopy and optical transmission measurements were used to evaluate the shape and size distribution of the NPs.

  9. Influence of consecutive picosecond pulses at 532 nm wavelength on laser ablation of human teeth

    NASA Astrophysics Data System (ADS)

    Mirdan, Balsam M.; Antonelli, Luca; Batani, Dimitri; Jafer, Rashida; Jakubowska, Katarzyna; Tarazi, Saad al; Villa, Anna Maria; Vodopivec, Bruno; Volpe, Luca

    2014-07-01

    The interaction of 40 ps pulse duration laser emitting at 532 nm wavelength with human dental tissue (enamel, dentin, and dentin-enamel junction) has been investigated. The crater profile and the surface morphology have been studied by using a confocal auto-fluorescence microscope (working in reflection mode) and a scanning electron microscope. Crater profile and crater morphology were studied after applying consecutive laser pulses and it was found that the ablation depth increases with the number of consecutive pulses, leaving the crater diameter unchanged. We found that the thermal damage is reduced by using short duration laser pulses, which implies an increased retention of restorative material. We observe carbonization of the irradiated samples, which does not imply changes in the chemical composition. Finally, the use of 40 ps pulse duration laser may become a state of art in conservative dentistry.

  10. Multiple pulse resonantly enhanced laser plasma wakefield acceleration

    SciTech Connect

    Corner, L.; Walczak, R.; Nevay, L. J.; Dann, S.; Hooker, S. M.; Bourgeois, N.; Cowley, J.

    2012-12-21

    We present an outline of experiments being conducted at Oxford University on multiple-pulse, resonantly-enhanced laser plasma wakefield acceleration. This method of laser plasma acceleration uses trains of optimally spaced low energy short pulses to drive plasma oscillations and may enable laser plasma accelerators to be driven by compact and efficient fibre laser sources operating at high repetition rates.

  11. Ultrathin sectioning with DUV-pulsed laser ablation: development of a laser ablation nano tome.

    PubMed

    Kanemaru, Takaaki; Oki, Yuji

    2015-08-01

    The electrically automated ultrathin sectioning apparatus, which has been developed in recent years, can produce consecutive ultrathin sections with a diamond knife and a gallium ion beam. These newly developed apparatuses, however, have several shortcomings, such as the limited block cutting area, thermal damage to the sample by the focused ion beam and a sample electronic charge. To overcome these faults and for easier scanning electron microscopy three-dimensional fine structural reconstruction, we have developed a new cutting method using a deep ultraviolet laser, which we have named the 'LANTome (Light Ablation Nanotome)'. Using this method, we confirmed the widening of sectioning areas, shortening of the sectioning time, automatic smoothing of rough surfaces, no sample electronic charge and minimal heat effects on the sample tissue, such as thermal denaturation. PMID:25888714

  12. Pd2+ reduction and gasochromic properties of colloidal tungsten oxide nanoparticles synthesized by pulsed laser ablation

    NASA Astrophysics Data System (ADS)

    Tahmasebi Garavand, N.; Mahdavi, S. M.; Iraji zad, A.

    2012-08-01

    Tungsten oxide nanoparticles were fabricated by a pulsed laser ablation method in deionized water using the first harmonic of a Nd:YAG laser ( λ=1064 nm) at three different laser pulse energies (E1 =160, E2 =370 and E3 =500 mJ/pulse), respectively. The aim is to investigate the effect of laser pulse energy on the size distribution and gasochromic property of colloidal nanoparticles. The products were characterized by dynamic light scattering (DLS), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and UV-Vis spectroscopy. The results indicated that WO3 nanoparticles were formed. After ablation, a 0.2 g/l PdCl2 solution was added to activate the solution against hydrogen gas. In this process Pd2+ ions were reduced to deposit fine metallic Pd particles on the surface of tungsten oxide nanoparticles. The gasochromic response was measured by H2 and O2 gases bubbling into the produced colloidal Pd-WO3. The results indicate that the number of unreduced ions (Pd2+) decreases with increasing laser pulse energy; therefore, for colloidal nanoparticles synthesized at the highest laser pulse energy approximately all Pd2+ ions have been reduced. Hence, the gasochromic response for this sample is nearly reversible in all cycles, whereas those due to other samples are not reversible in the first cycle.

  13. Fabrication of gold and silver nanoparticles with pulsed laser ablation under pressurized CO2

    NASA Astrophysics Data System (ADS)

    Machmudah, Siti; Wahyudiono; Takada, Noriharu; Kanda, Hideki; Sasaki, Koichi; Goto, Motonobu

    2013-12-01

    Pulsed laser ablation (PLA) has become a promising method for the synthesis of nanoclusters for photonics, electronics and medicine. In this work PLA in pressurized CO2 has been applied for fabrication of gold and silver nanoparticles. Laser ablation was performed with an excitation wavelength of 532 nm under various pressures (0.1-20 MPa), temperatures (40-80 °C) of CO2 medium and ablation times (1500-9000 s). On the basis of the experimental result, it follows that structures of gold (Au) and silver (Ag) nanoparticles were significantly affected by the changes in CO2 density. The structures of gold and silver nanoparticles also changed with an increase of ablation time. From a field-emission scanning electron microscopy (FE-SEM) image of the fabricated gold nano-structured particles on silicon wafer, it was seen that a network structure of smaller gold particles was fabricated. A similar morphology of particles fabricated from silver plate was observed. Silver particles contain nanoparticles with large-varied diameter ranging from 5 nm to 1.2 μm. The mechanism of nanoparticles fabrication could be observed as follows. Bigger gold/silver particles melted during the ablation process and then ejected smaller spherical nanoparticles, which formed nanoclusters attached on the molten particles.

  14. Pilot-scale synthesis of metal nanoparticles by high-speed pulsed laser ablation in liquids.

    PubMed

    Streubel, René; Bendt, Georg; Gökce, Bilal

    2016-05-20

    The synthesis of catalysis-relevant nanoparticles such as platinum and gold is demonstrated with productivities of 4 g h(-1) for pulsed laser ablation in liquids (PLAL). The major drawback of low productivity of PLAL is overcome by utilizing a novel ultrafast high-repetition rate laser system combined with a polygon scanner that reaches scanning speeds up to 500 m s(-1). This high scanning speed is exploited to spatially bypass the laser-induced cavitation bubbles at MHz-repetition rates resulting in an increase of the applicable, ablation-effective, repetition rate for PLAL by two orders of magnitude. The particle size, morphology and oxidation state of fully automated synthesized colloids are analyzed while the ablation mechanisms are studied for different laser fluences, repetition rates, interpulse distances, ablation times, volumetric flow rates and focus positions. It is found that at high scanning speeds and high repetition rate PLAL the ablation process is stable in crystallite size and decoupled from shielding and liquid effects that conventionally occur during low-speed PLAL. PMID:27053598

  15. Pilot-scale synthesis of metal nanoparticles by high-speed pulsed laser ablation in liquids

    NASA Astrophysics Data System (ADS)

    Streubel, René; Bendt, Georg; Gökce, Bilal

    2016-05-01

    The synthesis of catalysis-relevant nanoparticles such as platinum and gold is demonstrated with productivities of 4 g h‑1 for pulsed laser ablation in liquids (PLAL). The major drawback of low productivity of PLAL is overcome by utilizing a novel ultrafast high-repetition rate laser system combined with a polygon scanner that reaches scanning speeds up to 500 m s‑1. This high scanning speed is exploited to spatially bypass the laser-induced cavitation bubbles at MHz-repetition rates resulting in an increase of the applicable, ablation-effective, repetition rate for PLAL by two orders of magnitude. The particle size, morphology and oxidation state of fully automated synthesized colloids are analyzed while the ablation mechanisms are studied for different laser fluences, repetition rates, interpulse distances, ablation times, volumetric flow rates and focus positions. It is found that at high scanning speeds and high repetition rate PLAL the ablation process is stable in crystallite size and decoupled from shielding and liquid effects that conventionally occur during low-speed PLAL.

  16. Spatiotemporal evolution of plasma molecular emission following laser ablation of explosive analogs

    NASA Astrophysics Data System (ADS)

    Merten, Jonathan; Jones, Matthew; Sheppard, Cheyenne; Parigger, Christian; Allen, Susan

    2013-05-01

    The spatial and temporal evolution of the CN molecular emission following laser ablation of a TNT analog (3- nitrobenzoic acid) has been studied along with ablation of targets that contain neither nitro groups nor C-N bonds. At a fluence of ~104 J/cm2, behavior indicative of the ablation of native CN bonds has been observed in samples containing no native CN bonds. The recorded data show significant plasma background emissions that pose difficulties for direct spectral imaging. Spatially resolved images suggest that some of the observed phenomena are simply the result of the interaction of the plasma and the observation volume of the collection optics.

  17. Patterned graphene ablation and two-photon functionalization by picosecond laser pulses in ambient conditions

    SciTech Connect

    Bobrinetskiy, I. I. Otero, N.; Romero, P. M.; Emelianov, A. V.

    2015-07-27

    Direct laser writing is a technology with excellent prospects for mask-less processing of carbon-based nanomaterials, because of the wide range of photoinduced reactions that can be performed on large surfaces with submicron resolution. In this paper, we demonstrate the use of picoseconds laser pulses for one-step ablation and functionalization of graphene. Varying the parameters of power, pulse frequency, and speed, we demonstrated the ablation down to 2 μm width and up to mm-long lines as well as functionalization with spatial resolution less than 1 μm with linear speeds in the range of 1 m/s. Raman and atomic-force microscopy studies were used to indicate the difference in modified graphene states and correlation to the changes in optical properties.

  18. Cavitation effect of holmium laser pulse applied to ablation of hard tissue underwater.

    PubMed

    Lü, Tao; Xiao, Qing; Xia, Danqing; Ruan, Kai; Li, Zhengjia

    2010-01-01

    To overcome the inconsecutive drawback of shadow and schlieren photography, the complete dynamics of cavitation bubble oscillation or ablation products induced by a single holmium laser pulse [2.12 microm, 300 micros (FWHM)] transmitted in different core diameter (200, 400, and 600 microm) fibers is recorded by means of high-speed photography. Consecutive images from high-speed cameras can stand for the true and complete process of laser-water or laser-tissue interaction. Both laser pulse energy and fiber diameter determine cavitation bubble size, which further determines acoustic transient amplitudes. Based on the pictures taken by high-speed camera and scanned by an optical coherent microscopy (OCM) system, it is easily seen that the liquid layer at the distal end of the fiber plays an important role during the process of laser-tissue interaction, which can increase ablation efficiency, decrease heat side effects, and reduce cost. PMID:20799845

  19. Gold fingerprinting by laser ablation inductively coupled plasma mass spectrometry

    NASA Astrophysics Data System (ADS)

    Watling, R. John; Herbert, Hugh K.; Delev, Dianne; Abell, Ian D.

    1994-02-01

    Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) has been applied to the characterization of the trace element composition "fingerprint" of selected gold samples from Western Australia and South Africa. By comparison of the elemental associations it is possible to relate gold to a specific mineralizing event, mine or bullion sample. This methodology facilitates identification of the provenance of stolen gold or gold used in salting activities. In this latter case, it is common for gold from a number of sources to be used in the salting process. Consequently, gold in the prospect being salted will not come from a single source and identification of multiple sources for this gold will establish that salting has occurred. Preliminary results also indicate that specific elemental associations could be used to identify the country of origin of gold. The technique has already been applied in 17 cases involving gold theft in Western Australia, where it is estimated that up to 2% of gold production is "relocated" each year as a result of criminal activities.

  20. Pulse distortion and modulation instability in laser plasma interaction

    SciTech Connect

    Jha, Pallavi; Singh, Ram Gopal; Upadhyay, Ajay K.

    2009-01-15

    The present paper deals with the propagation of a short, intense, Gaussian laser pulse in plasma. Using a one dimensional model, a wave equation including finite pulse length and group velocity dispersion is set up and solved to obtain the intensity distribution across the laser pulse. It is shown that the pulse profile becomes asymmetric as it propagates through plasma. Further, the growth rate of modulation instability and range of unstable frequencies across the laser pulse have been derived and graphically analyzed.

  1. Synthesis of Nickel Nanomaterial by Pulsed Laser Ablation in Liquid Medium and its Characterization

    SciTech Connect

    Gopal, R.; Singh, S. C.; Swarnkar, R. K.; Singh, M. K.; Agarwal, A.

    2009-06-29

    Laser ablation of nickel nanoparticles suspended in double deionized water has been studied using Nd:YAG laser (355 nm) with energy 30 mJ/pulse. Produced nanoparticles are analyzed by UV-visible absorption spectroscopy at certain interval (0, 20, 40, 60 minute). The particles are characterized by Transmission Electron Microscopy (TEM), and X-ray Diffraction (XRD). TEM image shows that particles have crystal like structure and these particles are in the range of 20 nm to 50 nm.

  2. Synthesis of Nickel Nanomaterial by Pulsed Laser Ablation in Liquid Medium and its Characterization

    NASA Astrophysics Data System (ADS)

    Gopal, R.; Singh, M. K.; Agarwal, A.; Singh, S. C.; Swarnkar, R. K.

    2009-06-01

    Laser ablation of nickel nanoparticles suspended in double deionized water has been studied using Nd:YAG laser (355 nm) with energy 30 mJ/pulse. Produced nanoparticles are analyzed by UV-visible absorption spectroscopy at certain interval (0, 20, 40, 60 minute). The particles are characterized by Transmission Electron Microscopy (TEM), and X-ray Diffraction (XRD). TEM image shows that particles have crystal like structure and these particles are in the range of 20 nm to 50 nm.

  3. Predictable surface ablation of dielectrics with few-cycle laser pulse even beyond air ionization

    NASA Astrophysics Data System (ADS)

    Pasquier, C.; Sentis, M.; Utéza, O.; Sanner, N.

    2016-08-01

    We study surface ablation of dielectrics with single-shot few-cycle optical pulse (˜10 fs) in air, at intensities below and above the onset of air ionization. We perform 3D analysis and careful calibration of the fluence distribution at the laser focus, spanning from linear- to nonlinear- focusing regimes, enabling to thoroughly characterize the severe limitation of the fluence delivered onto the sample surface upon increase of incident pulse energy. Despite significant beam reshaping taking place at high fluence, we demonstrate that it is nevertheless possible to confidently predict the resulting crater profiles on fused silica surface, even in the regime of filamentation.

  4. Structural properties of silicon nanoparticles formed by pulsed laser ablation in liquid media

    NASA Astrophysics Data System (ADS)

    Eroshova, O. I.; Perminov, P. A.; Zabotnov, S. V.; Gongal'skii, M. B.; Ezhov, A. A.; Golovan', L. A.; Kashkarov, P. K.

    2012-11-01

    Silicon nanoparticles have been formed as a result of the irradiation of single-crystal silicon targets in distilled water and liquid nitrogen, by, respectively, picosecond and femtosecond laser pulses. The main structural properties of these nanoparticles have been investigated by atomic force microscopy, transmission electron microscopy, electron diffraction, Raman scattering, and photoluminescence spectroscopy. These particles are found to be mainly spherical. The presence of crystalline and amorphous silicon phases under picosecond ablation in water is established experimentally. Irradiation by femtosecond pulses in liquid nitrogen can yield nanoparticles smaller than 5 nm in size, which are quantum dots with a characteristic photoluminescence peak near 750 nm.

  5. Flexible interference ablation using fibers to split and deliver laser pulses for direct plasmonic nanopatterning

    NASA Astrophysics Data System (ADS)

    Lin, Yuanhai; Zhang, Xinping

    2014-09-01

    Optical fibers are used to achieve a flexible interference ablation scheme, where the bundled end of fibers functions as a beam splitter and the fibers are used to deliver 5-ns ultraviolet laser pulses at 355 nm. The divergent beams from the free ends of fibers are overlapped onto the film of colloidal gold nanoparticles. A single-pulse single-shot exposure process leads to removal of the gold nanoparticles within the bright interference fringes. Gold nanogratings are produced on glass substrates coated with indium tin oxide after an annealing process at 400 °C. Fano coupling between plasmon and waveguide resonance modes was observed.

  6. Morphology selective preparation and formation mechanism of graphene nanoribbons from graphite by liquid-phase pulsed laser ablation

    NASA Astrophysics Data System (ADS)

    Ren, X. D.; Liu, R.; Zheng, L. M.; Ren, Y. P.; Hu, Z. Z.; He, H.

    2016-02-01

    The paper studied preparation and formation mechanism of free-standing 3D graphene nanoribbons (GNRs) from graphite by pulsed laser ablation in liquid. The method to fabricate freestanding graphene nanoribbons directly was simple and controllable, which does not need other precursor materials and has no byproducts. Prepared graphene nanoribbons are shown composed of up to 14 layers of graphene, spaced about 0.30-0.35 nm and have a length of hundreds of nanometers. Formation mechanism of graphene nanoribbons was proposed based on the interaction between laser and material which can be demonstrated that the exfoliation of GNRs is a carbon plasma collision connecting-graphene segments-graphene sheets-multilayer graphene-graphene nanoribbons process. The high degree of repeatability and particularity found in the obtained GNRs might suggest their unique advantages and potential applications in nano-devices and spin electronics.

  7. A survey of pulse shape options for a revised plastic ablator ignition design

    NASA Astrophysics Data System (ADS)

    Clark, Daniel; Eder, David; Haan, Steven; Hinkel, Denise; Jones, Ogden; Marinak, Michael; Milovich, Jose; Peterson, Jayson; Robey, Harold; Salmonson, Jay; Smalyuk, Vladimir; Weber, Christopher

    2014-10-01

    Recent experimental results using the ``high foot'' pulse shape on the National Ignition Facility (NIF) have shown encouraging progress compared to earlier ``low foot'' experiments. These results strongly suggest that controlling ablation front instability growth can dramatically improve implosion performance, even in the presence of persistent, large, low-mode distortions. In parallel, Hydro. Growth Radiography experiments have so far validated the techniques used for modeling ablation front growth in NIF experiments. It is timely then to combine these two results and ask how current ignition pulse shapes could be modified so as to improve implosion performance, namely fuel compressibility, while maintaining the stability properties demonstrated with the high foot. This talk presents a survey of pulse shapes intermediate between the low and high foot extremes in search of a more optimal design. From the database of pulse shapes surveyed, a higher picket version of the original low foot pulse shape shows the most promise for improved compression without loss of stability. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  8. Tumour cell membrane poration and ablation by pulsed low-intensity electric field with carbon nanotubes.

    PubMed

    Wang, Lijun; Liu, Dun; Zhou, Ru; Wang, Zhigang; Cuschieri, Alfred

    2015-01-01

    Electroporation is a physical method to increase permeabilization of cell membrane by electrical pulses. Carbon nanotubes (CNTs) can potentially act like "lighting rods" or exhibit direct physical force on cell membrane under alternating electromagnetic fields thus reducing the required field strength. A cell poration/ablation system was built for exploring these effects of CNTs in which two-electrode sets were constructed and two perpendicular electric fields could be generated sequentially. By applying this system to breast cancer cells in the presence of multi-walled CNTs (MWCNTs), the effective pulse amplitude was reduced to 50 V/cm (main field)/15 V/cm (alignment field) at the optimized pulse frequency (5 Hz) of 500 pulses. Under these conditions instant cell membrane permeabilization was increased to 38.62%, 2.77-fold higher than that without CNTs. Moreover, we also observed irreversible electroporation occurred under these conditions, such that only 39.23% of the cells were viable 24 h post treatment, in contrast to 87.01% cell viability without presence of CNTs. These results indicate that CNT-enhanced electroporation has the potential for tumour cell ablation by significantly lower electric fields than that in conventional electroporation therapy thus avoiding potential risks associated with the use of high intensity electric pulses. PMID:25822874

  9. Tumour Cell Membrane Poration and Ablation by Pulsed Low-Intensity Electric Field with Carbon Nanotubes

    PubMed Central

    Wang, Lijun; Liu, Dun; Zhou, Ru; Wang, Zhigang; Cuschieri, Alfred

    2015-01-01

    Electroporation is a physical method to increase permeabilization of cell membrane by electrical pulses. Carbon nanotubes (CNTs) can potentially act like “lighting rods” or exhibit direct physical force on cell membrane under alternating electromagnetic fields thus reducing the required field strength. A cell poration/ablation system was built for exploring these effects of CNTs in which two-electrode sets were constructed and two perpendicular electric fields could be generated sequentially. By applying this system to breast cancer cells in the presence of multi-walled CNTs (MWCNTs), the effective pulse amplitude was reduced to 50 V/cm (main field)/15 V/cm (alignment field) at the optimized pulse frequency (5 Hz) of 500 pulses. Under these conditions instant cell membrane permeabilization was increased to 38.62%, 2.77-fold higher than that without CNTs. Moreover, we also observed irreversible electroporation occurred under these conditions, such that only 39.23% of the cells were viable 24 h post treatment, in contrast to 87.01% cell viability without presence of CNTs. These results indicate that CNT-enhanced electroporation has the potential for tumour cell ablation by significantly lower electric fields than that in conventional electroporation therapy thus avoiding potential risks associated with the use of high intensity electric pulses. PMID:25822874

  10. Dynamic mechanism of the velocity splitting of ablated particles produced by pulsed-laser deposition in an inert gas

    NASA Astrophysics Data System (ADS)

    Ding, X. C.; Wang, Y. L.; Chu, L. Z.; Deng, Z. C.; Liang, W. H.; Galalaldeen, I. I. A.; Fu, G. S.

    2011-12-01

    The transport dynamics of ablated particles produced by pulsed-laser deposition in an inert gas is investigated via the Monte Carlo simulation method. The splitting mechanism of ablated particles is discussed by tracking every ablated particle with their forces, velocities and locations. The force analysis demonstrates that whether the splitting appears or not is decided by the releasing way of the driving force acting on the ablated particles. The "average" drag force, which is related to the mass and radius of the ambient gas, determines the releasing way of the driving force. Our simulated results are approximately in agreement with the previous experimental data.

  11. Analysis of process parameter for the ablation of optical glasses with femto- and picosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Schindler, Christian; Friedrich, Maria; Bliedtner, Jens

    2016-03-01

    Experiments with an ultrashort pulsed laser system emitting pulses ranging from 350 fs to 10 ps and a maximum average power of 50 W at 1030 nm are presented. The laser beam gets deflected by a galvanometric scan-system with maximum scan speed of 2500 mm/s and focused by F-theta lenses onto the substrates. By experiments the influences of pulse energy, fluence, laser wavelength, pulse length and material conditions on the target figures is analyzed. These are represented by the material characteristics mean squared roughness, ablation depths as well as the microcrack distribution in depth. The experimental procedure is applied onto a series of fused silica and SF6 samples.

  12. Multi-Pulse laser ablation modeling with applications to automated zona removal.

    PubMed

    Wong, Christopher Yee; Mills, James K

    2015-08-01

    Laser zona drilling (LZD), the ablation of a portion of the zona pellucida (ZP) in embryos with the use of a laser, is a required step in many embryonic surgical procedures such as assisted hatching and preimplantation genetic diagnosis. The objective of LZD is to remove specific locations of the ZP while minimizing potential harmful thermal effects to important structures of the embryo, namely the blastomeres. Current thermal analyzes of lasers used in LZD only encompass the use of a single pulse, whereas LZD is typically performed using multiple pulses. In this paper we analyze the effect of multipulse LZD and introduce a linear approximation method for multi-pulse LZD. Furthermore, we describe a novel method of measuring the thermal effect of a single laser pulse using the thermosensitive fluorescent dye Rhodamine B and a high speed camera. PMID:26736816

  13. Laser ablation plasmas for diagnostics of structured electronic and optical materials during or after laser processing

    NASA Astrophysics Data System (ADS)

    Russo, Richard E.; Bol'shakov, Alexander A.; Yoo, Jong H.; González, Jhanis J.

    2012-03-01

    Laser induced plasma can be used for rapid optical diagnostics of electronic, optical, electro-optical, electromechanical and other structures. Plasma monitoring and diagnostics can be realized during laser processing in real time by means of measuring optical emission that originates from the pulsed laser-material interaction. In post-process applications, e.g., quality assurance and quality control, surface raster scanning and depth profiling can be realized with high spatial resolution (~10 nm in depth and ~3 μm lateral). Commercial instruments based on laser induced breakdown spectrometry (LIBS) are available for these purposes. Since only a laser beam comes in direct contact with the sample, such diagnostics are sterile and non-disruptive, and can be performed at a distance, e.g. through a window. The technique enables rapid micro-localized chemical analysis without a need for sample preparation, dissolution or evacuation of samples, thus it is particularly beneficial in fabrication of thin films and structures, such as electronic, photovoltaic and electro-optical devices or circuits of devices. Spectrum acquisition from a single laser shot provides detection limits for metal traces of ~10 μg/g, which can be further improved by accumulating signal from multiple laser pulses. LIBS detection limit for Br in polyethylene is 90 μg/g using 50-shot spectral accumulation (halogen detection is a requirement for semiconductor package materials). Three to four orders of magnitude lower detection limits can be obtained with a femtosecond laser ablation - inductively coupled plasma mass spectrometer (LA-ICP-MS), which is also provided on commercial basis. Laser repetition rate is currently up to 20 Hz in LIBS instruments and up to 100 kHz in LA-ICP-MS.

  14. Electron acceleration by a laser pulse in a plasma

    SciTech Connect

    McKinstrie, C.J.; Startsev, E.A.

    1996-08-01

    The acceleration of an electron by a circularly polarized laser pulse in a plasma is studied. It appears possible to increase significantly the energy of a preaccelerated electron. Although the pulse tends to generate a plasma wake, to which it loses energy, one can eliminate the wake by choosing the duration of the pulse judiciously. {copyright} {ital 1996 The American Physical Society.}

  15. Heat generation caused by ablation of dental restorative materials with an ultra short pulse laser (USPL) system

    NASA Astrophysics Data System (ADS)

    Braun, Andreas; Wehry, Richard; Brede, Olivier; Frentzen, Matthias; Schelle, Florian

    2011-03-01

    The aim of this study was to assess heat generation in dental restoration materials following laser ablation using an Ultra Short Pulse Laser (USPL) system. Specimens of phosphate cement (PC), ceramic (CE) and composite (C) were used. Ablation was performed with an Nd:YVO4 laser at 1064 nm and a pulse length of 8 ps. Heat generation during laser ablation depended on the thickness of the restoration material. A time delay for temperature increase was observed in the PC and C group. Employing the USPL system for removal of restorative materials, heat generation has to be considered.

  16. Pulsed Electromagnetic Acceleration of Plasma: A Review

    NASA Technical Reports Server (NTRS)

    Thio, Y. C. Francis; Turchi, Peter J.; Markusic, Thomas E.; Cassibry, Jason T.; Sommer, James; Rodgers, Stephen L. (Technical Monitor)

    2002-01-01

    Much have been learned in the acceleration mechanisms involved in accelerating a plasma electromagnetically in the laboratory over the last 40 years since the early review by Winston Bostik of 1963, but the accumulated understanding is very much scattered throughout the literature. This literature extends back at least to the early sixties and includes Rosenbluth's snowplow model, discussions by Ralph Lovberg, Colgate's boundary-layer model of a current sheet, many papers from the activity at Columbia by Robert Gross and his colleagues, and the relevant, 1-D unsteady descriptions developed from the U. of Maryland theta-pinch studies. Recent progress on the understanding of the pulsed penetration of magnetic fields into collisionless or nearly collisionless plasmas are also be reviewed. Somewhat more recently, we have the two-dimensional, unsteady results in the collisional regime associated with so-called wall-instability in large radius pinch discharges and also in coaxial plasma guns (e.g., Plasma Flow Switch). Among other things, for example, we have the phenomenon of a high- density plasma discharge propagating in a cooaxial gun as an apparently straight sheet (vs paraboloid) because mass re-distribution (on a microsecond timescale) compensates for the 1/r- squared variation of magnetic pressure. We will attempt to collate some of this vast material and bring some coherence tc the development of the subject.

  17. Laser-ablation sampling for inductively coupled plasma distance-of-flight mass spectrometry

    SciTech Connect

    Gundlach-Graham, Alexander W.; Dennis, Elise; Ray, Steven J.; Enke, Christie G.; Barinaga, Charles J.; Koppenaal, David W.; Hieftje, Gary M.

    2015-01-01

    An inductively coupled plasma distance-of-flight mass spectrometer (ICP-DOFMS) has been coupled with laser-ablation (LA) sample introduction for the elemental analysis of solids. ICP-DOFMS is well suited for the analysis of laser-generated aerosols because it offers both high-speed mass analysis and simultaneous multi-elemental detection. Here, we evaluate the analytical performance of the LA-ICP-DOFMS instrument, equipped with a microchannel plate-based imaging detector, for the measurement of steady-state LA signals, as well as transient signals produced from single LA events. Steady-state detection limits are 1 mg g1, and absolute single-pulse LA detection limits are 200 fg for uranium; the system is shown capable of performing time-resolved single-pulse LA analysis. By leveraging the benefits of simultaneous multi-elemental detection, we also attain a good shot-to-shot reproducibility of 6% relative standard deviation (RSD) and isotope-ratio precision of 0.3% RSD with a 10 s integration time.

  18. Dynamic materials evaluation by confined plasma ablation and laser-generated shocks

    NASA Astrophysics Data System (ADS)

    Paisley, Dennis L.; Swift, D. C.; Forsman, A. C.; Kyrala, George A.; Johnson, Randall P.; Kopp, Roger A.; Hauer, Allan A.; Wark, Justin S.; Loveridge, A.; Allen, A. M.; Kalantar, Daniel H.

    2000-08-01

    Laser-generated shocks can and have been used to study their effects on single crystal materials during shock compression. While a crystal undergoes shock compression and release, the transient x- ray diffraction (TXD) of the Bragg and Laue signals is indicative of the change in the crystal lattice spacing. The lattice spacing directly relates to the strain in the crystal. From the dynamic lattice data, strain, strain rate, and/or phase change in a material may be determined. Confined ablation plasmas can efficiently launch a flyer plate for direct impact on a target material imparting a well-characterized shock input and generate kilobar to megabar pressure pulses over a wide range of pulse duration (= 20 ns). The laser-launched flyer plates are analogous to those launched by gas guns, but the smaller size provides an experimental method not easily accessible by larger gas gun experiments. With lasers, diagnostic equipment can be easily synchronized to study dynamic material parameters, i.e., single crystal shock dynamics, interfacial bond strengths of thin coatings, grain-interfaces, texture, and high strain rates (106 - 109 sec-1).

  19. Features of silicon-containing coatings deposition from ablation plasma formed by a powerful ion beam

    NASA Astrophysics Data System (ADS)

    Sazonov, R.; Kholodnaya, G.; Ponomarev, D.; Remnev, G.; Khailov, I.

    2014-11-01

    This paper presents the research of features of silicon-containing coatings deposition from ablation plasma, which is formed by a powerful ion beam at the influence on a microsized pressed powder of SiO2. Experimental research have been conducted with a laboratory setup based on a TEMP-4M pulsed ion accelerator in a double-pulse forming mode; the first is negative (300-500 ns, 100-150 kV), and the second is positive (150 ns, 250-300 kV). A beam composition: C+ ions (60-70 %) and protons, the ion current density on the target is 25±5 A/cm2. An electron self-magnetically insulated diode has been used to generate the ion beam in the TEMP-4M accelerator. The properties of obtained silicon-containing films have been analyzed with the help of IR spectroscopy. A surface structure has been studied by the method of scanning electron microscopy.

  20. Influence of pulse duration on erbium and holmium laser ablation under water

    NASA Astrophysics Data System (ADS)

    Ith, Michael; Frenz, Martin; Pratisto, Hans S.; Weber, Heinz P.; Altermatt, Hans J.; Staeubli, Hans U.; Asshauer, Thomas; Delacretaz, Guy P.; Salathe, Rene-Paul; Gerber, Bruno E.

    1995-01-01

    Erbium and Holmium lasers are ideally suited for cutting and drilling biological tissue. This is due to the fact that their wavelengths (Er:YSGG at 2.79 micrometers and Ho:YAG at 2.12 micrometers ) are strongly absorbed in water which is present in all tissues. Combined with an optical fiber these lasers seem to be optimal instruments for endoscopic and/or minimal invasive applications in surgery. In this study we focused our interest on cutting of human meniscus in the knee where, besides a very limited operation field, the standard arthroscopic treatment is performed in a liquid, highly absorbing environment. The bubble formation process, therefore, has to be well understood because it mainly determines relevant aspects of tissue ablation. The influence of the laser parameters in general and the influence of pulse duration in particular are determined in this paper for two different laser wavelengths. The goal was to determine the optimum laser parameters in view of a high ablation efficiency, a high precision and a minimal destruction of the adjacent tissue. To determine the optimum pulse duration for ablating tissue under water and to obtain a better understanding of the channel formation process, transmission and pressure measurements together with video flash photography were performed. Additionally, we determined experimentally the ratio between initial laser pulse energy and energy available for tissue treatment under water. To prove the results obtained, cuts in human meniscus were performed, sectioned and evaluated. The comparison between the results obtained with the Erbium and Holmium laser revealed a strong influence of the absorption coefficients on the tissue effects, especially on the ablation efficiency and on the zone of thermally and mechanically damaged tissue.

  1. Analysis of the short-pulsed CO2 laser ablation process for optimizing the processing performance for cutting bony tissue

    NASA Astrophysics Data System (ADS)

    Mehrwald, Markus; Burgner, Jessica; Platzek, Christoph; Feldmann, Claus; Raczkowsky, Jörg; Wörn, Heinz

    2010-02-01

    Recently we established an experimental setup for robot-assisted laser bone ablation using short-pulsed CO2 laser. Due to the comparable low processing speed of laser bone ablation the application in surgical interventions is not yet feasible. In order to optimize this ablation process, we conducted a series of experiments to derive parameters for a discrete process model. After applying single and multiple laser pulses with varying intensity onto bone, the resulting craters were measured using a confocal microscope in 3D. The resulting ablation volumes were evaluated by applying Gaussian function fitting. We then derived a logarithmic function for the depth prediction of laser ablation on bone. In order to increase the ablation performance we conducted experiments using alternate fluids replacing the water spray: pure glycerin, glycerin/water mixture, acids and bases. Because of the higher boiling point of glycerin compared to water we had expected deeper craters through the resulting higher temperatures. Experimental results showed that glycerin or a glycerin/water mix do not have any effect on the depth of the ablation craters. Additionally applying the acid or base on to the ablation site does only show minor benefits compared to water. Furthermore we preheated the chemicals with a low energy pulse prior to the ablation pulse, which also showed no effect. However, applying a longer soaking time of the chemicals induced nearly a doubling of the ablation depth in some cases. Furthermore with this longer soaking time, carbonization at the crater margins does not occur as is observed when using conventionally water spray.

  2. Structure of the dense cores and ablation plasmas in the initiation phase of tungsten wire-array Z pinches

    SciTech Connect

    Douglass, J. D.; Hammer, D. A.; McBride, R. D.; Pikuz, S. A.; Shelkovenko, T. A.; Bland, S. N.; Bott, S. C.

    2007-01-15

    The early stages of tungsten (W) wire-array Z-pinch implosions have been studied using two-frame point projection x-ray backlighting on the 1 MA COBRA pulsed power generator [J. D. Douglass, J. B. Greenly, D. A. Hammer, and B. R. Kusse, in Proceedings of the 15th IEEE International Pulsed Power Conference, Monterey, 2005 (to be published)]. X-pinch backlighter images with subnanosecond time resolution and 4-10 {mu}m spatial resolution have been obtained of individual W exploding wires in 8-wire arrays that show evolution of wire-core and coronal plasma structures. The timing of the X-pinch x-ray bursts relative to the Z-pinch initiation time was adjusted over a 50 ns time interval by varying the X-pinch mass per unit length. Wire-cores seen in two images separated in view by 120 deg. show that the expansion is remarkably azimuthally symmetric. A strong correlation is observed between the structure on the dense exploding wire-cores and the structure of the {>=}10{sup 18}/cm{sup 3} ablation plasma being drawn from radial prominences. Plasma ablation velocity was estimated to have a lower bound of 24 km/s. The wire-core expansion rate was found to be approximately constant with time over the interval 50-100 ns after the start of the current pulse. Finally, micron-scale axial gaps, seen as early as 70 ns into the current pulse and persisting from that time, were observed along the wire-core.

  3. Pulse-discharge plasmas for plasma-accelerator applications

    SciTech Connect

    Clayton, C. E.; Joshi, C.; Lopes, N. C.

    2012-12-21

    For particle-beam-driven plasma wakefield accelerators, a long and fully-ionized plasma is desirable. We describe an experiment at UCLA to develop a prototype of such plasma using a pulsed-current discharge. Scaling of the plasma density with glass-tube diameter and with discharge-circuit parameters is currently underway. We have found that 4 Torr of Argon can be fully ionized to a density of about 1.3 Multiplication-Sign 10{sup 17} cm{sup -3} when the current density in the 1 inch diameter, 1.2 meter-long tube is around 2 kA/cm{sup 2}, at least at one point along the discharge. The homogeneity of the plasma density in the longitudinal direction is crucial to prevent slippage of the driven plasma structures with the particles. Equally important are the transverse gradients since any dipole asymmetry in the transverse direction can lead to 'steering' of the particle beam. The longitudinal and transverse gradients may be a function of time into the discharge, the shape of the electrodes, the tube size, and the fractional ionization for a given fill pressure. These issues are currently under investigation.

  4. Pulse Power Supply for Plasma Dynamic Accelerator

    NASA Astrophysics Data System (ADS)

    Yang, Xuanzong; Liu, Jian; Feng, Chunhua; Wang, Long

    2008-06-01

    A new concept of a coaxial plasma dynamic accelerator with a self-energized magnetic compressor coil to simulate the effects of space debris impact is demonstrated. A brief description is presented about the pulse power supply system including the charging circuit, start switch and current transfer system along with some of the key techniques for this kind of accelerator. Using this accelerator configuration, ceramic beads of 100 fim in diameter were accelerated to a speed as high as 18 km/sec. The facility can be used in a laboratory setting to study impact phenomena on solar array materials, potential structural materials for use in space.

  5. Study of polymer ablation products obtained by ultraviolet laser ablation — inductively coupled plasma atomic emission spectrometry

    NASA Astrophysics Data System (ADS)

    Todolí, J.-L.; Mermet, J.-M.

    1998-10-01

    A study of the nature of aerosols following polymer laser ablation was performed. A glass sample was used for comparison. Aerosol fractions were analyzed by using simple methods based on transport efficiency and filters. Three different tube lengths, i.e. 4, 29 and 54 m, were inserted between the ablation cell and the inductively coupled plasma atomic emission spectrometry (ICP-AES) injector. For the glass sample, 10 elements were studied. Only Na and K exhibited different results as the particle size, i.e. tube length, was varied. The polymers used were poly(vinyl chloride), PVC, and poly(ethylene), PE. Three elements (Ca, Ti and Sn) under different chemical forms were measured. Unlike Ti and Sn the ablated aerosol particle size (mass) seemed to depend on the Ca chemical form. Another PVC sample containing 11 elements was also studied. Na, Al and C exhibited a different behavior with particle size with respect to the remaining elements. Then, the carbon signal was studied after a 0.3 μm pore size filter had been placed between the ablation cell and the ICP torch. The results indicated that carbon was mainly present under gaseous form and particles smaller than 0.3 μm size. The analysis of the aerosol gaseous phase by thermal desorption GC-MS confirmed the presence of polymer volatile thermal degradation products. These results explained why carbon could not be applied as an efficient internal standard.

  6. Silver nanoparticles generated by pulsed laser ablation in supercritical CO2 medium

    NASA Astrophysics Data System (ADS)

    Machmudah, Siti; Sato, Takayuki; Wahyudiono; Sasaki, Mitsuru; Goto, Motonobu

    2012-03-01

    Pulsed laser ablation (PLA) has been widely employed in industrial and biological applications and in other fields. The environmental conditions in which PLA is conducted are important parameters that affect both the solid particle cloud and the deposition produced by the plume. In this work, the generation of nanoparticles (NPs) has been developed by performing PLA of silver (Ag) plates in a supercritical CO2 medium. Ag NPs were successfully generated by allowing the selective generation of clusters. Laser ablation was performed with an excitation wavelength of 532 nm under various pressures and temperatures of CO2 medium. On the basis of the experimental result, both surface of the irradiated Ag plate and structure of Ag NPs were significantly affected by the changes in supercritical CO2 pressure and temperature. With increasing irradiation pressure, plume deposited in the surrounding crater created by the ablation was clearly observed. In Field Emission Scanning Electron Microscopy (FE-SEM) the image of the generated Ag NPs on the silicon wafer and the morphology of Ag particles were basically a sphere-like structure. Ag particles contain NPs with large-varied diameter ranging from 5 nm to 1.2 μm. The bigger Ag NPs melted during the ablation process and then ejected smaller spherical Ag NPs, which formed nanoclusters attached on the molten Ag NPs. The smaller Ag NPs were also formed around the bigger Ag NPs. Based on the results, this new method can also be used to obtain advanced nano-structured materials.

  7. Pulsed Inductive Plasma Acceleration: Performance Optimization Criteria

    NASA Technical Reports Server (NTRS)

    Polzin, Kurt A.

    2014-01-01

    Optimization criteria for pulsed inductive plasma acceleration are developed using an acceleration model consisting of a set of coupled circuit equations describing the time-varying current in the thruster and a one-dimensional momentum equation. The model is nondimensionalized, resulting in the identification of several scaling parameters that are varied to optimize the performance of the thruster. The analysis reveals the benefits of underdamped current waveforms and leads to a performance optimization criterion that requires the matching of the natural period of the discharge and the acceleration timescale imposed by the inertia of the working gas. In addition, the performance increases when a greater fraction of the propellant is initially located nearer to the inductive acceleration coil. While the dimensionless model uses a constant temperature formulation in calculating performance, the scaling parameters that yield the optimum performance are shown to be relatively invariant if a self-consistent description of energy in the plasma is instead used.

  8. Convoluted effect of laser fluence and pulse duration on the property of a nanosecond laser-induced plasma into an argon ambient gas at the atmospheric pressure

    SciTech Connect

    Bai Xueshi; Ma Qianli; Motto-Ros, Vincent; Yu Jin; Sabourdy, David; Nguyen, Luc; Jalocha, Alain

    2013-01-07

    We studied the behavior of the plasma induced by a nanosecond infrared (1064 nm) laser pulse on a metallic target (Al) during its propagation into argon ambient gas at the atmospheric pressure and especially over the delay interval ranging from several hundred nanoseconds to several microseconds. In such interval, the plasma is particularly interesting as a spectroscopic emission source for laser-induced plasma spectroscopy (LIBS). We show a convoluted effect between laser fluence and pulse duration on the structure and the emission property of the plasma. With a relatively high fluence of about 160 J/cm{sup 2} where a strong plasma shielding effect is observed, a short pulse of about 4 ns duration is shown to be significantly more efficient to excite the optical emission from the ablation vapor than a long pulse of about 25 ns duration. While with a lower fluence of about 65 J/cm{sup 2}, a significantly more efficient excitation is observed with the long pulse. We interpret our observations by considering the post-ablation interaction between the generated plume and the tailing part of the laser pulse. We demonstrate that the ionization of the layer of ambient gas surrounding the ablation vapor plays an important role in plasma shielding. Such ionization is the consequence of laser-supported absorption wave and directly dependent on the laser fluence and the pulse duration. Further observations of the structure of the generated plume in its early stage of expansion support our explanations.

  9. Controlling electron injection in laser plasma accelerators using multiple pulses

    SciTech Connect

    Matlis, N. H.; Geddes, C. G. R.; Plateau, G. R.; Esarey, E.; Schroeder, C.; Bruhwiler, D.; Cormier-Michel, E.; Chen, M.; Yu, L.; Leemans, W. P.

    2012-12-21

    Use of counter-propagating pulses to control electron injection in laser-plasma accelerators promises to be an important ingredient in the development of stable devices. We discuss the colliding pulse scheme and associated diagnostics.

  10. The role of laser wavelength on plasma generation and expansion of ablation plumes in air

    SciTech Connect

    Hussein, A. E.; Diwakar, P. K.; Harilal, S. S.; Hassanein, A.

    2013-04-14

    We investigated the role of excitation laser wavelength on plasma generation and the expansion and confinement of ablation plumes at early times (0-500 ns) in the presence of atmospheric pressure. Fundamental, second, and fourth harmonic radiation from Nd:YAG laser was focused on Al target to produce plasma. Shadowgraphy, fast photography, and optical emission spectroscopy were employed to analyze the plasma plumes, and white light interferometry was used to characterize the laser ablation craters. Our results indicated that excitation wavelength plays a crucial role in laser-target and laser-plasma coupling, which in turn affects plasma plume morphology and radiation emission. Fast photography and shadowgraphy images showed that plasmas generated by 1064 nm are more cylindrical compared to plasmas generated by shorter wavelengths, indicating the role of inverse bremsstrahlung absorption at longer laser wavelength excitation. Electron density estimates using Stark broadening showed higher densities for shorter wavelength laser generated plasmas, demonstrating the significance of absorption caused by photoionization. Crater depth analysis showed that ablated mass is significantly higher for UV wavelengths compared to IR laser radiation. In this experimental study, the use of multiple diagnostic tools provided a comprehensive picture of the differing roles of laser absorption mechanisms during ablation.

  11. The role of laser wavelength on plasma generation and expansion of ablation plumes in air

    NASA Astrophysics Data System (ADS)

    Hussein, A. E.; Diwakar, P. K.; Harilal, S. S.; Hassanein, A.

    2013-04-01

    We investigated the role of excitation laser wavelength on plasma generation and the expansion and confinement of ablation plumes at early times (0-500 ns) in the presence of atmospheric pressure. Fundamental, second, and fourth harmonic radiation from Nd:YAG laser was focused on Al target to produce plasma. Shadowgraphy, fast photography, and optical emission spectroscopy were employed to analyze the plasma plumes, and white light interferometry was used to characterize the laser ablation craters. Our results indicated that excitation wavelength plays a crucial role in laser-target and laser-plasma coupling, which in turn affects plasma plume morphology and radiation emission. Fast photography and shadowgraphy images showed that plasmas generated by 1064 nm are more cylindrical compared to plasmas generated by shorter wavelengths, indicating the role of inverse bremsstrahlung absorption at longer laser wavelength excitation. Electron density estimates using Stark broadening showed higher densities for shorter wavelength laser generated plasmas, demonstrating the significance of absorption caused by photoionization. Crater depth analysis showed that ablated mass is significantly higher for UV wavelengths compared to IR laser radiation. In this experimental study, the use of multiple diagnostic tools provided a comprehensive picture of the differing roles of laser absorption mechanisms during ablation.

  12. Particle Generation by Pulsed Excimer Laser Ablation in Liquid: Hollow Structures and Laser-Induced Reactions

    NASA Astrophysics Data System (ADS)

    Yan, Zijie

    2011-12-01

    Pulsed laser ablation of solid targets in liquid media is a powerful method to fabricate micro-/nanoparticles, which has attracted much interest in the past decade. It represents a combinatorial library of constituents and interactions, and one can explore disparate regions of parameter space with outcomes that are impossible to envision a priori. In this work, a pulsed excimer laser (wavelength 248 nm, pulse width 30 ns) has been used to ablate targets in liquid media with varying laser fluences, frequencies, ablation times and surfactants. It is observed that hollow particles could be fabricated by excimer laser ablation of Al, Pt, Zn, Mg, Ag, Si, TiO2, and Nb2O5 in water or aqueous solutions. The hollow particles, with sizes from tens of nanometers to micrometers, may have smooth and continuous shells or have morphologies demonstrating that they were assembled from nanoparticles. A new mechanism has been proposed to explain the formation of these novel particle geometries. They were formed on laser-produced bubbles through bubble interface pinning by laser-produced solid species. Considering the bubble dynamics, thermodynamic and kinetic requirements have been discussed in the mechanism that can explain some phenomena associated with the formation of hollow particles, especially (1) larger particles are more likely to be hollow particles; (2) Mg and Al targets have stronger tendency to generate hollow particles; and (3) the 248 nm excimer laser is more beneficial to fabricate hollow particles in water than other lasers with longer wavelengths. The work has also demonstrated the possiblities to fabricate novel nanostructures through laser-induced reactions. Zn(OH)2/dodecyl sulfate flower-like nanostructures, AgCl cubes, and Ag2O cubes, pyramids, triangular plates, pentagonal rods and bars have been obtained via reactions between laser-produced species with water, electrolyes, or surfactant molecules. The underlying mechanisms of forming these structures have been

  13. Laser pulse modulation instabilities in plasma channels

    PubMed

    Sprangle; Hafizi; Penano

    2000-04-01

    In this paper the modulational instability associated with propagation of intense laser pulses in a partially stripped, preformed plasma channel is analyzed. In general, modulation instabilities are caused by the interplay between (anomalous) group velocity dispersion and self-phase modulation. The analysis is based on a systematic approach that includes finite-perturbation-length effects, nonlinearities, group velocity dispersion, and transverse effects. To properly include the radial variation of both the laser field and plasma channel, the source-dependent expansion method for analyzing the wave equation is employed. Matched equilibria for a laser beam propagating in a plasma channel are obtained and analyzed. Modulation of a uniform (matched) laser beam equilibrium in a plasma channel leads to a coupled pair of differential equations for the perturbed spot size and laser field amplitude. A general dispersion relation is derived and solved. Surface plots of the spatial growth rate as a function of laser beam power and the modulation wave number are presented. PMID:11088236

  14. Nanosecond pulsed laser ablation of brass in a dry and liquid-confined environment

    NASA Astrophysics Data System (ADS)

    Bashir, Shazia; Vaheed, Hamza; Mahmood, Khaliq

    2013-02-01

    The effect of ambient environment (dry or wet) and overlapping laser pulses on the laser ablation performance of brass has been investigated. For this purpose, a Q-switched, frequency doubled Nd:YAG laser with a wavelength of 532 nm, pulse energy of 150 mJ, pulse width of 6 ns and repetition rate of 10 Hz is employed. In order to explore the effect of ambient environments, brass targets have been exposed in deionized water, methanol and air. The targets are exposed for 1000, 2000, 3000 and 4000 succeeding pulses in each atmosphere. The surface morphology and chemical composition of ablated targets have been characterized by using Scanning Electron Microscope (SEM), Atomic Force Microscope (AFM) and Attenuated Total Reflection (ATR) techniques. In case of liquid environment, various features like nano- and micro-scale laser-induced periodic surface structures with periodicity 500 nm-1 μm, cavities of size few micrometers with multiple ablative layers and phenomenon of thermal stress cracking are observed. These features are originated by various chemical and thermal phenomena induced by laser heating at the liquid-solid interfaces. The convective bubble motion, explosive boiling, pressure gradients, cluster and colloid formation due to confinement effects of liquids are possible cause for such kind of features. The metal oxides and alcohol formed on irradiated surface are also playing the significant role for the formation of these kinds of structure. In case of air one huge crater is formed along with the redeposition of sputtered material and is ascribed to laser-induced evaporation and oxide formation.

  15. Influence of plasma parameters and substrate temperature on the structural and optical properties of CdTe thin films deposited on glass by laser ablation

    SciTech Connect

    Quiñones-Galván, J. G.; Santana-Aranda, M. A.; Pérez-Centeno, A.; Camps, Enrique; Campos-González, E.; Guillén-Cervantes, A.; Santoyo-Salazar, J.; Zelaya-Angel, O.; Hernández-Hernández, A.

    2015-09-28

    In the pulsed laser deposition of thin films, plasma parameters such as energy and density of ions play an important role in the properties of materials. In the present work, cadmium telluride thin films were obtained by laser ablation of a stoichiometric CdTe target in vacuum, using two different values for: substrate temperature (RT and 200 °C) and plasma energy (120 and 200 eV). Structural characterization revealed that the crystalline phase can be changed by controlling both plasma energy and substrate temperature; which affects the corresponding band gap energy. All the thin films showed smooth surfaces and a Te rich composition.

  16. Chirped pulse compression in nonuniform plasma Bragg gratings

    SciTech Connect

    Wu Huichun; Sheng Zhengming; Zhang Jie

    2005-11-14

    A nonuniform plasma Bragg grating with a monotonically increasing density-modulation profile can be naturally produced by two Gaussian laser pulses counterpropagating through a homogeneous plasma slab. Such a plasma grating exhibits a nonuniform photonic band gap with a monotonically increasing width. It can be used to compress a positively or negatively chirped pulse. Particle-in-cell simulations show that the compressed pulse has nearly no energy loss and the compression efficiency can exceed 90%.

  17. Influence of the pulse frequency and water cooling on the femtosecond laser ablation of bovine cortical bone

    NASA Astrophysics Data System (ADS)

    Cangueiro, L. T.; Vilar, R.

    2013-10-01

    Ultrafast lasers are extremely promising tools for minimally-invasive orthopedic surgery, but the ablated volumes per pulse are low, so a high pulse frequency is necessary to reach practical ablation rates. The purpose of this work was to study in vitro the influence of the pulse repetition rate on the ablation rate, surface topography and surface composition of bone using of bovine cortical femur as a model. The tests were carried out by scanning the laser beam in relation to the sample, using pulse frequencies between 50 and 3000 Hz, scanning velocities from 0.5 to 10 mm/s and average pulse energy of 650 μJ. The experiments were performed in dry conditions and with water irrigation. The higher ablation rates were obtained at high scanning velocity without water irrigation but severe thermal effects such as resolidification, cracking and, eventually, carbonization occurred in these conditions due to heat accumulation in the tissue. Thermal damage was avoided for all the laser processing parameters ranges tested by using water cooling. The highest ablation rate achieved was 1.4 mm3/min for a scanning velocity of 10 mm/s at 2 kHz pulse repetition rate under water irrigation.

  18. Fabrication of gold nanoparticles in Therminol VP-1 by laser ablation and fragmentation with fs pulses

    NASA Astrophysics Data System (ADS)

    Torres-Mendieta, R.; Mondragón, R.; Juliá, E.; Mendoza-Yero, O.; Cordoncillo, E.; Lancis, J.; Mínguez-Vega, G.

    2014-12-01

    This letter reports on a physical method to produce highly pure, size-controlled and well-dispersed spherical gold nanoparticles (NPs) in Therminol VP-1 by pulsed laser ablation in liquids (PLAL) using a 30 fs Ti:Sapphire laser at a fluence of 1 J cm-2. A second photo-fragmentation of the ablated colloid solution by subsequent treatment with the same laser light yields a mean size and size dispersion of the NPs of 58 ± 31 nm. A study of the nanofluid properties reveals a low agglomeration over time and an enhancement of thermal conductivity of the base fluid by up to 4%. These results improve the characteristics of current nanofluids in thermal oils that may have a potential impact on the improvement of the efficiency of harvesting of solar light.

  19. Elemental fractionation in 785 nm picosecond and femtosecond laser ablation inductively coupled plasma mass spectrometry

    NASA Astrophysics Data System (ADS)

    Shaheen, M. E.; Gagnon, J. E.; Fryer, B. J.

    2015-05-01

    Elemental fractionation and ICP-MS signal response were investigated for two different pulse width laser beams originating from the same laser system. Femtosecond and picosecond laser beams at pulse widths of 130 fs and 110 ps, respectively, and wavelength of 785 nm were used to ablate NIST 610 synthetic glass and SRM 1107 Naval Brass B at the same spot for 800 to 1000 laser pulses at different repetition rates (5 to 50 Hz). Elemental fractionation was found to depend on repetition rate and showed a trend with femtosecond laser ablation that is opposite to that observed in picosecond laser ablation for most measured isotopes. ICP-MS signal intensity was higher in femtosecond than picosecond LA-ICP-MS in both NIST 610 and naval brass when ablation was conducted under the same fluence and repetition rate. The differences in signal intensity were partly related to differences in particle size distribution between particles generated by femtosecond and picosecond laser pulses and the consequent differences in transport and ionization efficiencies. The main reason for the higher signal intensity resulting from femtosecond laser pulses was related to the larger crater sizes compared to those created during picosecond laser ablation. Elemental ratios measured using 66Zn/63Cu, 208Pb/238U, 232Th/238U, 66Zn/232Th and 66Zn/208Pb were found to change with the number of laser pulses with data points being more scattered in picosecond than femtosecond laser pulses. Reproducibility of replicate measurements of signal intensities, fractionation and elemental ratios was better for fs-LA-ICP-MS (RSD ~ 3 to 6%) than ps-LA-ICP-MS (RSD ~ 7 to 11%).

  20. Precise ablation of dental hard tissues with ultra-short pulsed lasers. Preliminary exploratory investigation on adequate laser parameters.

    PubMed

    Bello-Silva, Marina Stella; Wehner, Martin; Eduardo, Carlos de Paula; Lampert, Friedrich; Poprawe, Reinhart; Hermans, Martin; Esteves-Oliveira, Marcella

    2013-01-01

    This study aimed to evaluate the possibility of introducing ultra-short pulsed lasers (USPL) in restorative dentistry by maintaining the well-known benefits of lasers for caries removal, but also overcoming disadvantages, such as thermal damage of irradiated substrate. USPL ablation of dental hard tissues was investigated in two phases. Phase 1--different wavelengths (355, 532, 1,045, and 1,064 nm), pulse durations (picoseconds and femtoseconds) and irradiation parameters (scanning speed, output power, and pulse repetition rate) were assessed for enamel and dentin. Ablation rate was determined, and the temperature increase measured in real time. Phase 2--the most favorable laser parameters were evaluated to correlate temperature increase to ablation rate and ablation efficiency. The influence of cooling methods (air, air-water spray) on ablation process was further analyzed. All parameters tested provided precise and selective tissue ablation. For all lasers, faster scanning speeds resulted in better interaction and reduced temperature increase. The most adequate results were observed for the 1064-nm ps-laser and the 1045-nm fs-laser. Forced cooling caused moderate changes in temperature increase, but reduced ablation, being considered unnecessary during irradiation with USPL. For dentin, the correlation between temperature increase and ablation efficiency was satisfactory for both pulse durations, while for enamel, the best correlation was observed for fs-laser, independently of the power used. USPL may be suitable for cavity preparation in dentin and enamel, since effective ablation and low temperature increase were observed. If adequate laser parameters are selected, this technique seems to be promising for promoting the laser-assisted, minimally invasive approach. PMID:22565342

  1. Analysis of Sterilization Effect of Atmospheric Pressure Pulsed Plasma

    SciTech Connect

    Ekem, N.; Akan, T.; Pat, S.; Akgun, Y.; Kiremitci, A.; Musa, G.

    2007-04-23

    We have developed a new technology, the High Voltage Atmospheric Pressure Pulsed Plasma (HVAPPP), for bacteria killing. The aim of this paper is to present a simple device to generate plasma able to kill efficiently bacteria.

  2. EVOLUTION OF FAST MAGNETOACOUSTIC PULSES IN RANDOMLY STRUCTURED CORONAL PLASMAS

    SciTech Connect

    Yuan, D.; Li, B.; Pascoe, D. J.; Nakariakov, V. M.; Keppens, R. E-mail: bbl@sdu.edu.cn

    2015-02-01

    We investigate the evolution of fast magnetoacoustic pulses in randomly structured plasmas, in the context of large-scale propagating waves in the solar atmosphere. We perform one-dimensional numerical simulations of fast wave pulses propagating perpendicular to a constant magnetic field in a low-β plasma with a random density profile across the field. Both linear and nonlinear regimes are considered. We study how the evolution of the pulse amplitude and width depends on their initial values and the parameters of the random structuring. Acting as a dispersive medium, a randomly structured plasma causes amplitude attenuation and width broadening of the fast wave pulses. After the passage of the main pulse, secondary propagating and standing fast waves appear. Width evolution of both linear and nonlinear pulses can be well approximated by linear functions; however, narrow pulses may have zero or negative broadening. This arises because narrow pulses are prone to splitting, while broad pulses usually deviate less from their initial Gaussian shape and form ripple structures on top of the main pulse. Linear pulses decay at an almost constant rate, while nonlinear pulses decay exponentially. A pulse interacts most efficiently with a random medium with a correlation length of about half of the initial pulse width. This detailed model of fast wave pulses propagating in highly structured media substantiates the interpretation of EIT waves as fast magnetoacoustic waves. Evolution of a fast pulse provides us with a novel method to diagnose the sub-resolution filamentation of the solar atmosphere.

  3. Heat generation caused by ablation of dental hard tissues with an ultrashort pulse laser (USPL) system.

    PubMed

    Braun, Andreas; Krillke, Raphael Franz; Frentzen, Matthias; Bourauel, Christoph; Stark, Helmut; Schelle, Florian

    2015-02-01

    Heat generation during the removal of dental hard tissues may lead to a temperature increase and cause painful sensations or damage dental tissues. The aim of this study was to assess heat generation in dental hard tissues following laser ablation using an ultrashort pulse laser (USPL) system. A total of 85 specimens of dental hard tissues were used, comprising 45 specimens of human dentine evaluating a thickness of 1, 2, and 3 mm (15 samples each) and 40 specimens of human enamel with a thickness of 1 and 2 mm (20 samples each). Ablation was performed with an Nd:YVO4 laser at 1,064 nm, a pulse duration of 9 ps, and a repetition rate of 500 kHz with an average output power of 6 W. Specimens were irradiated for 0.8 s. Employing a scanner system, rectangular cavities of 1-mm edge length were generated. A temperature sensor was placed at the back of the specimens, recording the temperature during the ablation process. All measurements were made employing a heat-conductive paste without any additional cooling or spray. Heat generation during laser ablation depended on the dental hard tissue (enamel or dentine) and the thickness of the respective tissue (p < 0.05). Highest temperature increase could be observed in the 1-mm thickness group for enamel. Evaluating the 1-mm group for dentine, a significantly lower temperature increase could be measured (p < 0.05) with lowest values in the 3-mm group (p < 0.05). A time delay for temperature increase during the ablation process depending on the material thickness was observed for both hard tissues (p < 0.05). Employing the USPL system to remove dental hard tissues, heat generation has to be considered. Especially during laser ablation next to pulpal tissues, painful sensations and potential thermal injury of pulp tissue might occur. PMID:23666547

  4. Some Considerations on the Pulsed Electromagnetic Acceleration of Plasma

    NASA Technical Reports Server (NTRS)

    Thio, Y. C. F.; Markusic, T. E.; Cassibry, J. T.; Sommers, J. C.; Turchi, P. J.; Rodgers, Stephen L. (Technical Monitor)

    2002-01-01

    In applying pulsed electromagnetic acceleration of plasma to space propulsion (known as pulsed plasma thrusters in the community), the mode of acceleration used has been mostly in the collisionless or near-collisionless regime. The preparation of the initial plasma is given scant attention. Collisional regime of accelerating the plasma, however, have been encountered in a variety of plasma accelerating devices. Both of these modes of acceleration are reviewed in a companion paper. In this paper, we discuss the considerations governing the controlled introduction and preparation of the initial plasma, so that the collisional mode of accelerating the plasma may be suitably enhanced.

  5. Evaluation of the analytical capability of NIR femtosecond laser ablation-inductively coupled plasma mass spectrometry.

    PubMed

    Hirata, Takafumi; Kon, Yoshiaki

    2008-03-01

    A laser ablation-inductively coupled plasma-mass spectrometric (LA-ICPMS) technique utilizing a titanium-sapphire (TiS) femtosecond laser (fs-laser) has been developed for elemental and isotopic analysis. The signal intensity profile, depth of the ablation pit and level of elemental fractionation were investigated in order to evaluate the analytical capability of the present fs-laser ablation-ICPMS technique. The signal intensity profile of (57)Fe, obtained from iron sulfide (FeS(2)), demonstrated that the resulting signal intensity of (57)Fe achieved by the fs-laser ablation was almost 4-times higher than that obtained by ArF excimer laser ablation under a similar energy fluence (5 J/cm(2)). In fs-laser ablation, there is no significant difference in a depth of the ablation pit between glass and zircon material, while in ArF laser ablation, the resulting crater depth on the zircon crystal was almost half the level than that obtained for glass material. Both the thermal-induced and particle size-related elemental fractionations, which have been thought to be main sources of analytical error in the LA-ICPMS analysis, were measured on a Harvard 91500 zircon crystal. The resulting fractionation indexes on the (206)Pb/(238)U (f(Pb/U)) and (238)U/(232)Th (f(U/Th)) ratios obtained by the present fs-laser ablation system were significantly smaller than those obtained by a conventional ArF excimer laser ablation system, demonstrative of smaller elemental fractionation. Using the present fs-laser ablation technique, the time profile of the signal intensity of (56)Fe and the isotopic ratios ((57)Fe/(54)Fe and (56)Fe/(54)Fe) have been measured on a natural pyrite (FeS(2)) sample. Repeatability in signal intensity of (56)Fe achieved by the fs-laser ablation system was significantly better than that obtained by ArF excimer laser ablation. Moreover, the resulting precision in (57)Fe/(54)Fe and (56)Fe/(54)Fe ratio measurements could be improved by the fs-laser ablation system

  6. Group velocity and pulse lengthening of mismatched laser pulses in plasma channels

    SciTech Connect

    Schroeder, C. B.; Benedetti, C.; Esarey, E.; Tilborg, J. van; Leemans, W. P.

    2011-08-15

    Analytic solutions are presented to the non-paraxial wave equation describing an ultra-short, low-power, laser pulse propagating in a plasma channel. Expressions for the laser pulse centroid motion and laser group velocity are derived, valid for matched and mismatched propagation in a parabolic plasma channel, as well as in vacuum, for an arbitrary Laguerre-Gaussian laser mode. The group velocity of a mismatched laser pulse, for which the laser spot size is strongly oscillating, is found to be independent of propagation distance and significantly less than that of a matched pulse. Laser pulse lengthening of a mismatched pulse owing to laser mode slippage is examined and found to dominate over that due to dispersive pulse spreading for sufficiently long pulses. Analytic results are shown to be in excellent agreement with numerical solutions of the full Maxwell equations coupled to the plasma response. Implications for plasma channel diagnostics are discussed.

  7. Ablation of human carious dentin with a nanosecond pulsed laser at a wavelength of 5.85 μm: relationship between hardness and ablation depth

    NASA Astrophysics Data System (ADS)

    Ishii, Katsunori; Kita, Tetsuya; Yoshikawa, Kazushi; Yasuo, Kenzo; Yamamoto, Kazuyo; Awazu, Kunio

    2014-02-01

    Less invasive treatment and preservation of teeth, referred to as minimal intervention, are strong requirements in dentistry. In our previous study, the fundamental ablation properties of human dentin at wavelengths around 5.8 μm were investigated, and the results indicated that the wavelength of 5.85 μm was optimal for selective removal of carious dentin with less damage to normal dentin. The purpose of this study was to investigate the relationship between the ablation depth and hardness of human dentin including carious lesion. A nanosecond pulsed laser produced by difference-frequency generation was used for irradiations to human carious dentin. It was observed that correlation between ablation depth and Vickers hardness after 2 s laser irradiation at the wavelength of 5.85 μm and the average power density of 30 W/cm2. On the other hand, ablations did not depend on Vickers hardness at the wavelength of 6.00 μm. A nanosecond pulsed laser with the wavelength at 5.85 μm is useful for selective ablation of human carious dentin in accordance with the hardness.

  8. Spectroscopic studies on diamond like carbon films synthesized by pulsed laser ablation

    NASA Astrophysics Data System (ADS)

    Panda, Madhusmita; Krishnan, R.; Ravindran, T. R.; Das, Arindam; Mangamma, G.; Dash, S.; Tyagi, A. K.

    2016-05-01

    Hydrogen free Diamond like Carbon (DLC) thin films enriched with C-C sp3 bonding were grown on Si (111) substrates at laser pulse energies varying from 100 to 400 mJ (DLC-100, DLC-200, DLC-300, DLC-400), by Pulsed Laser Ablation (PLA) utilizing an Nd:YAG laser operating at fundamental wavelength. Structural, optical and morphological evolutions as a function of laser pulse energy were studied by micro Raman, UV-Vis spectroscopic studies and Atomic Force Microscopy (AFM), respectively. Raman spectra analysis provided critical clues for the variation in sp3 content and optical energy gap. The sp3 content was estimated using the FWHM of the G peak and found to be in the range of 62-69%. The trend of evolution of sp3 content matches well with the evolution of ID/IG ratio with pulse energy. UV-Vis absorption study of DLC films revealed the variation of optical energy gap with laser pulse energy (1.88 - 2.23 eV), which matches well with the evolution of G-Peak position of the Raman spectra. AFM study revealed that roughness, size and density of particulate in DLC films increase with laser pulse energy.

  9. Synthesis of GaN nanocrystallites by pulsed laser ablation in pure nitrogen background gases

    NASA Astrophysics Data System (ADS)

    Yoshida, Takehito; Kakumoto, Soichiro; Sugimura, Akira; Umezu, Ikurou

    2011-09-01

    GaN is a promising material not only for electronic devices but also for photocatalysts. Synthesis of GaN nanocrystal is a key issue to improve performance for these applications. In the present study, GaN nanocrystallites have been synthesized by pulsed laser ablation (PLA), where safe and inactive pure N2 gases were used as reactive background gases. The third harmonics beam of a Q-switched Nd:YAG laser (355 nm, 10 mJ/pulse, 4 J/(cm2 pulse)) was used to ablate a sintered high purity GaN target. The deposition substrates were not heated. It was clarified that the formed GaN nanoparticles contained a hexagonal system with the wurtzite structure. The diameter of the nanocrystallites was about 10 nm, and showed only little dependence on the background gas pressure, while the porosity of the assembly of nanocrystallites and content of GaN nanocrystallites in the assembly increased with background gas pressure. Highly porous nanometer-sized GaN film obtained at higher gas pressure is considered to be candidate structures for the photocatalysts.

  10. Nucleation and growth of nanoparticles in a plasma by laser ablation in liquid

    NASA Astrophysics Data System (ADS)

    Taccogna, Francesco

    2015-10-01

    > Modelling the nucleation and growth of nanoparticles in liquid-phase laser ablation is very important to optimize and control the size and the structure of nanoparticles. However, the detailed formation process of nanoparticles after laser ablation is still unclear. In the present study we investigated for the first time the kinetic growth of nanoparticles synthesized by laser ablation in water, emphasizing the leading role of the plasma medium and in particular the electrostatic agglomeration due to the charging of the nanoparticle in the plasma plume. The importance of the confining role of the liquid medium on the plasma plume is revealed, showing how an isothermal expansion is able to produce smaller nanoparticles compared to an adiabatic cooling.

  11. Compact And Robust Laser Impulse Measurement Device, With Ultrashort Pulse Laser Ablation Results

    NASA Astrophysics Data System (ADS)

    Kremeyer, Kevin; Lapeyre, John; Hamann, Steven

    2008-04-01

    An impulse measurement device and analysis package was conceived, designed, constructed, tested, and demonstrated to be capable of: measuring nanoNewton-seconds to milliNewton-seconds of impulse due to laser-ablation; being transported as carry-on baggage; set-up and tear-down times of less than an hour; target exchange times of less than two minutes (targets can be ablated at multiple positions for thousands of shots); measurements in air and in vacuum; error of just a few percent; repeatability over a wide range of potential systematic error sources; and time between measurements, including ring-down and analysis, of less than 30 seconds. The instrument consists of a cantilever (i.e. leaf spring), whose time-dependent displacement/oscillation is measured and analyzed to determine the impulse imparted by a laser pulse to a target. These shapes are readily/commercially available, and any target material can be used, provided it can be fashioned in the form of a cantilever, or as a coating/film/tape, suitable for mounting on a cantilever of known geometry. The instrument was calibrated both statically and dynamically, and measurements were performed on brass, steel, and Aluminum, using laser pulses of ˜7 ns, ˜500 ps, and ˜500 fs. The results agree well with those published in the literature, with surface effects, atmosphere, and pre-/post-pulses demonstrating interesting effects and indicating areas for further study. These parameters should be carefully controlled and held constant during a series of measurements. The impulse imparted by ablation due to laser filaments in air was also explored.

  12. Combination of fiber-guided pulsed erbium and holmium laser radiation for tissue ablation under water

    NASA Astrophysics Data System (ADS)

    Pratisto, Hans; Frenz, Martin; Ith, Michael; Altermatt, Hans J.; Jansen, E. Duco; Weber, Heinz P.

    1996-07-01

    Because of the high absorption of near-infrared laser radiation in biological tissue, erbium lasers and holmium lasers emitting at 3 and 2 mu m, respectively, have been proven to have optimal qualities for cutting or welding and coagulating tissue. To combine the advantages of both wavelengths, we realized a multiwavelength laser system by simultaneously guiding erbium and holmium laser radiation by means of a single zirconium fluoride (ZrF4) fiber. Laser-induced channel formation in water and poly(acrylamide) gel was investigated by the use of a time-resolved flash-photography setup, while pressure transients were recorded simultaneously with a needle hydrophone. The shapes and depths of vapor channels produced in water and in a submerged gel after single erbium and after combination erbium-holmium radiation delivered by means of a 400- mu m ZrF4 fiber were measured. Transmission measurements were performed to determine the amount of pulse energy available for tissue ablation. The effects of laser wavelength and the delay time between pulses of different wavelengths on the photomechanical and photothermal responses of meniscal tissue were evaluated in vitro by the use of histology. It was observed that the use of a short (200- mu s, 100-mJ) holmium laser pulse as a prepulse to generate a vapor bubble through which the ablating erbium laser pulse can be transmitted (delay time, 100 mu s) increases the cutting depth in meniscus from 450 to 1120 mu m as compared with the depth following a single erbium pulse. The results indicate that a combination of erbium and holmium laser radiation precisely and efficiently cuts tissue under water with 20-50- mu m collateral tissue damage. wave, cavitation, channel formation, infrared-fiber-delivery system, tissue damage, cartilage.

  13. CO sub 2 -laser ablation of Bi-Sr-Ca-Cu oxide by millisecond pulse lengths

    SciTech Connect

    Meskoob, M.; Honda, T.; Safari, A.; Wachtman, J.B.; Danforth, S. ); Wilkens, B.J. )

    1990-03-15

    We have achieved ablation of Bi-Sr-Ca-Cu oxide from single targets of superconducting pellets by CO{sub 2}-laser pulses of l ms length to grow superconducting thin films. Upon annealing, the 6000-A thin films have a {ital T}{sub {ital c}} (onset) of 90 K and zero resistance at 78 K. X-ray diffraction patterns indicate the growth of single-phase thin films. This technique allows growth of uniform single-phase superconducting thin films of lateral area greater than 1 cm{sup 2}.

  14. Measurement of ablation threshold of oxide-film-coated aluminium nanoparticles irradiated by femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Chefonov, O. V.; Ovchinnikov, A. V.; Il'ina, I. V.; Agranat, M. B.

    2016-03-01

    We report the results of experiments on estimation of femtosecond laser threshold intensity at which nanoparticles are removed from the substrate surface. The studies are performed with nanoparticles obtained by femtosecond laser ablation of pure aluminium in distilled water. The attenuation (or extinction, i.e. absorption and scattering) spectra of nanoparticles are measured at room temperature in the UV and optical wavelength ranges. The size of nanoparticles is determined using atomic force microscopy. A new method of scanning photoluminescence is proposed to evaluate the threshold of nanoparticle removal from the surface of a glass substrate exposed to IR femtosecond laser pulses with intensities 1011 – 1013 W cm-2.

  15. Laser ablation of CFRP using picosecond laser pulses at different wavelengths from UV to IR

    NASA Astrophysics Data System (ADS)

    Wolynski, Alexander; Herrmann, Thomas; Mucha, Patrick; Haloui, Hatim; L'huillier, Johannes

    Laser processing of carbon fibre reinforced plastics (CFRP) has a great industrial relevance for high performance structural parts in airplanes, machine tools and cars. Through-holes drilled by nanosecond laser pulses show thermal induced molten layers and voids. Recently, picosecond lasers have demonstrated the ability to drill high-efficient and high-quality rivet through-holes. In this paper a high-power picosecond laser system operating at different wavelengths (355 nm, 532 nm and 1064 nm) has been used for CFRP ablation experiments to study the influence of different laser parameters in terms of machining quality and processing time.

  16. Synthesis of single domain strontium ferrite powder by pulsed laser ablation

    NASA Astrophysics Data System (ADS)

    Nawathey-Dikshit, Rashmi; Shinde, S. R.; Ogale, S. B.; Kulkarni, S. D.; Sainkar, S. R.; Date, S. K.

    1996-06-01

    Strontium hexaferrite nanoparticles have been successfully prepared from a sintered SrFe12O19 target, using pulsed excimer laser ablation and cold condensation technique. The as-condensed powders do not exhibit the same magnetic properties as the target material. However, annealing at a high temperature of 850 °C for 3 h in air followed by fast cooling yields very high coercivity of 6665 Oe, exhibiting presence of single domain particles. Vibrating sample magnetometry (VSM), scanning electron microscopy (SEM), and x-ray diffraction (XRD) techniques are used to study the magnetism, microstructure, and phase formation in the powders, respectively.

  17. Biocompatible inorganic fullerene-like molybdenum disulfide nanoparticles produced by pulsed laser ablation in water.

    PubMed

    Wu, Haihua; Yang, Rong; Song, Baomin; Han, Qiusen; Li, Jingying; Zhang, Ying; Fang, Yan; Tenne, Reshef; Wang, Chen

    2011-02-22

    We report on the synthesis of inorganic fullerene-like molybdenum disulfide (MoS(2)) nanoparticles by pulsed laser ablation (PLA) in water. The final products were characterized by scanning electron microscopy, X-ray diffraction, transmission electron microscopy, and resonance Raman spectroscopy, etc. Cell viability studies show that the as-prepared MoS(2) nanoparticles have good solubility and biocompatibility, which may show a great potential in various biomedical applications. It is shown that the technique of PLA in water also provides a green and convenient method to synthesize novel nanomaterials, especially for biocompatible nanomaterials. PMID:21230008

  18. Laser-induced metal plasmas for pulsed laser deposition of metal-oxide thin films

    NASA Astrophysics Data System (ADS)

    Wagenaars, Erik; Colgan, James; Rajendiran, Sudha; Rossall, Andrew

    2015-09-01

    Metal and metal-oxide thin films, e.g. ZnO, MgO, Al2O3 and TiO2, are widely used in e.g. microelectronics, catalysts, photonics and displays. Pulsed Laser Deposition (PLD) is a plasma-based thin-film deposition technique that is highly versatile and fast, however it suffers from limitations in control of film quality due to a lack of fundamental understanding of the underlying physical processes. We present experimental and modelling studies of the initial phases of PLD: laser ablation and plume expansion. A 2D hydrodynamic code, POLLUX, is used to model the laser-solid interaction of a Zn ablation with a Nd:YAG laser. In this early phase of PLD, the plasma plume has temperatures of about 10 eV, is highly ionized, and travels with a velocity of about 10-100 km/sec away from the target. Subsequently, the plasma enters the plume expansion phase in which the plasma cools down and collision chemistry changes the composition of the plume. Time-integrated optical emission spectroscopy shows that Zn I and Zn II emission lines dominate the visible range of the light emission. Comparison with the Los Alamos plasma kinetics code ATOMIC shows an average temperature around 1 eV, indicating a significant drop in plasma temperature during the expansion phase. We acknowledge support from the UK Engineering and Physical Sciences Research Council (EPSRC), Grant EP/K018388/1.

  19. Synthesis of oxidation resistant lead nanoparticle films by modified pulsed laser ablation

    SciTech Connect

    Shin, Eunsung; Murray, P. Terrence; Subramanyam, Guru; Malik, Hans K.; Schwartz, Kenneth L.

    2012-07-30

    Thin layers of lead nanoparticles have been produced by a modified pulsed laser ablation (PLA) process in which smaller nanoparticles were swept out of the ablation chamber by a stream of flowing Ar. Large ({mu}m-sized) particles, which are usually deposited during the standard PLA process, were successfully eliminated from the deposit. The nanoparticles deposited on room temperature substrates were well distributed, and the most probable particle diameter was in the order of 30 nm. Since lead is highly reactive, the nanoparticles formed in Ar were quickly oxidized upon exposure to air. A small partial pressure of H{sub 2}S gas was subsequently added to the effluent, downstream from the ablation chamber, and this resulted in the formation of nanoparticle deposits that were surprisingly oxidation resistant. The properties of the nanoparticle films (as determined by transmission electron microscopy, scanning electron microscopy, x-ray diffraction, x-ray photoelectron spectroscopy, and conductivity measurements) are reported, and the mechanism of the oxidation retardation process is discussed.

  20. Synthesis of oxidation resistant lead nanoparticle films by modified pulsed laser ablation

    NASA Astrophysics Data System (ADS)

    Shin, Eunsung; Murray, P. Terrence; Subramanyam, Guru; Malik, Hans K.; Schwartz, Kenneth L.

    2012-07-01

    Thin layers of lead nanoparticles have been produced by a modified pulsed laser ablation (PLA) process in which smaller nanoparticles were swept out of the ablation chamber by a stream of flowing Ar. Large (μm-sized) particles, which are usually deposited during the standard PLA process, were successfully eliminated from the deposit. The nanoparticles deposited on room temperature substrates were well distributed, and the most probable particle diameter was in the order of 30 nm. Since lead is highly reactive, the nanoparticles formed in Ar were quickly oxidized upon exposure to air. A small partial pressure of H2S gas was subsequently added to the effluent, downstream from the ablation chamber, and this resulted in the formation of nanoparticle deposits that were surprisingly oxidation resistant. The properties of the nanoparticle films (as determined by transmission electron microscopy, scanning electron microscopy, x-ray diffraction, x-ray photoelectron spectroscopy, and conductivity measurements) are reported, and the mechanism of the oxidation retardation process is discussed.

  1. Silicon and zinc telluride nanoparticles synthesized by pulsed laser ablation: Size distributions and nanoscale structure

    SciTech Connect

    Lowndes, D.H.; Rouleau, C.M.; Duscher, G.

    1997-08-01

    Size distributions of Si and ZnTe nanoparticles produced by low energy density ArF (193 nm) pulsed laser ablation into ambient gases were measured as a function of the gas pressure and target-substrate separation, D{sub ts}, using atomic force microscopy (AFM) and high resolution scanning electron microscopy (HRSEM). For low energy density (Ed = 1.04 J/cm{sup 2}) ablation of Si into He at pressures of 0.5, 1.5, 4 and 10 torr, large nanoparticles were most numerous at D{sub ts} = 10 mm, with smaller nanoparticles found at 20 mm and 40 mm. For each D{sub ts} value a maximum of the mean nanoparticle diameter occurred for a He pressure near 6 torr, in contrast to other recent measurements in which the size of Si nanoparticles increased monotonically with the He pressure. High resolution Z-contrast transmission electron microscopy (HRZTEM) and electron energy loss spectroscopy (EELS) revealed that ZnTe nanoparticles formed by ablation into nitrogen at E{sub d} = 0.74 J/cm{sup 2} consisted of a crystalline ZnTe core surrounded by an amorphous ZnO shell. Growth defects and surface steps were clearly visible in the ZnTe crystalline core. The dependences of the mean diameter of ZnTe nanocrystals on nitrogen pressure and D{sub ts}, were qualitatively similar to those found for Si in He.

  2. Ultra-fast Movies Resolve Ultra-short Pulse Laser Ablation and Bump Formation on Thin Molybdenum Films

    NASA Astrophysics Data System (ADS)

    Domke, Matthias; Rapp, Stephan; Huber, Heinz

    For the monolithic serial interconnection of CIS thin film solar cells, 470 nm molybdenum films on glass substrates must be separated galvanically. The single pulse ablation with a 660 fs laser at a wavelength of 1053 nm is investigated in a fluence regime from 0.5 to 5.0 J/cm2. At fluences above 2.0 J/cm2 bump and jet formation can be observed that could be used for creating microstructures. For the investigation of the underlying mechanisms of the laser ablation process itself as well as of the bump or jet formation, pump probe microscopy is utilized to resolve the transient ablation behavior.

  3. Plasma Sensor Measurements in Pulse Detonation Engines

    NASA Astrophysics Data System (ADS)

    Matlis, Eric; Marshall, Curtis; Corke, Thomas; Gogineni, Sivaram

    2014-11-01

    Measurements have been conducted in a pulse detonation and rotating detonation engine using a newly developed plasma sensor. This sensor relies on the novel approach of using an ac-driven, weakly-ionized electrical discharge as the main sensing element. The advantages of this approach include a native high bandwidth of 1 MHz without the need for electronic frequency compensation, a dual-mode capability that provides sensitivity to multiple flow parameters, including velocity, pressure, temperature, and gas-species, and a simple and robust design making it very cost effective. The sensor design is installation-compatible with conventional sensors commonly used in gas-turbine research such as the Kulite dynamic pressure sensor while providing much better longevity. Developmental work was performed in high temperature facilities that are relevant to the propulsion and high-speed research community. This includes tests performed in a J85 augmentor at full afterburner and pulse-detonation engines at the University of Cincinnati (UC) at temperatures approaching 2760°C (5000°F).

  4. Integration and Test Flight Validation Plans for the Pulsed Plasma Thruster Experiment on EO- 1

    NASA Technical Reports Server (NTRS)

    Zakrzwski, Charles; Benson, Scott; Sanneman, Paul; Hoskins, Andy; Bauer, Frank H. (Technical Monitor)

    2002-01-01

    The Pulsed Plasma Thruster (PPT) Experiment on the Earth Observing One (EO-1) spacecraft has been designed to demonstrate the capability of a new generation PPT to perform spacecraft attitude control. The PPT is a small, self-contained pulsed electromagnetic propulsion system capable of delivering high specific impulse (900-1200 s), very small impulse bits (10-1000 uN-s) at low average power (less than 1 to 100 W). Teflon fuel is ablated and slightly ionized by means of a capacitative discharge. The discharge also generates electromagnetic fields that accelerate the plasma by means of the Lorentz Force. EO-1 has a single PPT that can produce thrust in either the positive or negative pitch direction. The flight validation has been designed to demonstrate of the ability of the PPT to provide precision pointing accuracy, response and stability, and confirmation of benign plume and EMI effects. This paper will document the success of the flight validation.

  5. Bismuth Oxide Thin Films Deposited on Silicon Through Pulsed Laser Ablation, for Infrared Detectors

    NASA Astrophysics Data System (ADS)

    Condurache-Bota, Simona; Constantinescu, Catalin; Tigau, Nicolae; Praisler, Mirela

    2016-12-01

    Infrared detectors are used in many human activities, from industry to military, telecommunications, environmental studies and even medicine. Bismuth oxide thin films have proved their potential for optoelectronic applications, but their uses as infrared sensors have not been thoroughly studied so far. In this paper, pulsed laser ablation of pure bismuth targets within a controlled oxygen atmosphere is proposed for the deposition of bismuth oxide films on Si (100) substrates. Crystalline films were obtained, whose uniformity depends on the deposition conditions (number of laser pulses and the use of a radio-frequency (RF) discharge of the oxygen inside the deposition chamber). The optical analysis proved that the refractive index of the films is higher than 3 and that their optical bandgap is around 1eV, recommending them for infrared applications.

  6. Synthesis by pulsed laser ablation of 2D nanostructures for advanced biomedical sensing

    NASA Astrophysics Data System (ADS)

    Trusso, S.; Zanchi, C.; Bombelli, A.; Lucotti, A.; Tommasini, M.; de Grazia, U.; Ciusani, E.; Romito, L. M.; Ossi, P. M.

    2016-05-01

    Au nanoparticle arrays with controlled nanostructure were produced by pulsed laser ablation on glass. Such substrates were optimized for biomedical sensing by means of SERS keeping fixed all process parameters but the laser pulse (LP) number that is a key deposition parameter. It allows to fine-tune the Au surface nanostructure with a considerable improvement in the SERS response towards the detection of apomorphine in blood serum (3.3 × 10‑6 M), when LP number is increased from 1 × 104 to 2 × 104. This result is the starting point to correlate the intensity of selected SERS signals of apomorphine to its concentration in the blood of patients with Parkinson's disease.

  7. Blue luminescent silicon nanocrystals prepared by short pulsed laser ablation in liquid media

    NASA Astrophysics Data System (ADS)

    Švrček, Vladimir; Kondo, Michio

    2009-09-01

    The pulsed laser processing in liquid media is an attractive alternative to produce room temperature luminescent silicon nanocrystals (Si-ncs). We report on a blue luminescent Si-ncs preparation by using nanosecond pulsed laser (Nd:YAG, KrF excimer) processing in transparent polymer and water. The Si-ncs fabrication is assured by ablation of crystalline silicon target immersed in liquids. During the processing and following aging in liquids, oxide based liquid media, induce shell formation around fresh nanocrystals that provides a natural and stable form of surface passivation. The stable room temperature blue-photoluminescent Si-ncs are prepared with maxima located around ˜440 nm with corresponding optical band gap around ˜2.8 eV (˜430 nm). Due to the reduction of surface defects, the Si-ncs preparation in water, leads to a narrowing of full-width-half-maxima of the photoluminescence spectra.

  8. Thermal ablation of thin gold films irradiated by ultrashort laser pulses

    NASA Astrophysics Data System (ADS)

    Li, Ling; Zhao, Shiqiang

    2016-04-01

    The vaporization process of gold film irradiated by ultrashort-pulsed laser is investigated using the parabolic two-step model and the dual-hyperbolic two-step model. The liquid-vapor interfacial velocity in the vaporization process is obtained by considering the interface energy balance equation and gas kinetics law. Comparisons between the temperature, velocity and location of the interface based on two different models are presented, the results show a great difference between them. In addition, the variation of ablation depth with pulse widths and fluence are also compared. The effects of laser parameters and film thickness on vaporization process are investigated. The relationship between the maximum temperature, velocity of liquid-vapor interface and laser fluence are also studied.

  9. Surface Engineering of Silicon and Carbon by Pulsed-Laser Ablation

    SciTech Connect

    Fowlkes, J.D.; Geohegan, D.B.; Jellison, G.E., Jr.; Lowndes, D.H.; Merkulov, V.I.; Pedraza, A.J.; Puretzky, A.A.

    1999-02-28

    Experiments are described in which a focused pulsed-excimer laser beam is used either to ablate a graphite target and deposit hydrogen-free amorphous carbon films, or to directly texture a silicon surface and produce arrays of high-aspect-ratio silicon microcolumns. In the first case, diamond-like carbon (or tetrahedral amorphous carbon, ta-C) films were deposited with the experimental conditions selected so that the masses and kinetic energies of incident carbon species were reasonably well controlled. Striking systematic changes in ta-C film properties were found. The sp{sup 3}-bonded carbon fraction, the valence electron density, and the optical (Tauc) energy gap ail reach their maximum values in films deposited at a carbon ion kinetic energy of {approximately}90 eV. Tapping-mode atomic force microscope measurements also reveal that films deposited at 90 eV are extremely smooth (rms roughness {approximately}1 {angstrom} over several hundred nm) and relatively free of particulate, while the surface roughness increases in films deposited at significantly lower energies. In the second set of experiments, dense arrays of high-aspect-ratio silicon microcolumns {approximately}20-40 {micro}m tall and {approximately}2 {micro}m in diameter were formed by cumulative nanosecond pulsed excimer laser irradiation of silicon wafers in air and other oxygen-containing atmospheres. It is proposed that microcolumn growth occurs through a combination of pulsed-laser melting of the tips of the columns and preferential redeposition of silicon on the molten tips from the ablated flux of silicon-rich vapor. The common theme in this research is that a focused pulsed-laser beam can be used quite generally to create an energetic flux, either the energetic carbon ions needed to form sp{sup 3} (diamond-like) bonds or the overpressure of silicon-rich species needed for microcolumn growth. Thus, new materials synthesis opportunities result from the access to nonequilibrium growth conditions

  10. Pulse propagation and electron acceleration in a corrugated plasma channel.

    PubMed

    Palastro, J P; Antonsen, T M; Morshed, S; York, A G; Milchberg, H M

    2008-03-01

    A preformed plasma channel provides a guiding structure for laser pulses unbound by the intensity thresholds of standard waveguides. The recently realized corrugated plasma channel [Layer, Phys. Rev. Lett. 99, 035001 (2007)] allows for the guiding of laser pulses with subluminal spatial harmonics. These spatial harmonics can be phase matched to high energy electrons, making the corrugated plasma channel ideal for the acceleration of electrons. We present a simple analytic model of pulse propagation in a corrugated plasma channel and examine the laser-electron beam interaction. Simulations show accelerating gradients of several hundred MeV/cm for laser powers much lower than required by standard laser wakefield schemes. PMID:18517531

  11. Photon kinetic modeling of laser pulse propagation in underdense plasma

    SciTech Connect

    Reitsma, A. J. W.; Trines, R. M. G. M.; Bingham, R.; Cairns, R. A.; Mendonca, J. T.; Jaroszynski, D. A.

    2006-11-15

    This paper discusses photon kinetic theory, which is a description of the electromagnetic field in terms of classical particles in coordinate and wave number phase space. Photon kinetic theory is applied to the interaction of laser pulses with underdense plasma and the transfer of energy and momentum between the laser pulse and the plasma is described in photon kinetic terms. A comparison is made between a one-dimensional full wave and a photon kinetic code for the same laser and plasma parameters. This shows that the photon kinetic simulations accurately reproduce the pulse envelope evolution for photon frequencies down to the plasma frequency.

  12. Observation of Laser-Pulse Shortening in Nonlinear Plasma Waves

    SciTech Connect

    Faure, J.; Glinec, Y.; Santos, J.J.; Ewald, F.; Rousseau, J.-P.; Malka, V.; Kiselev, S.; Pukhov, A.; Hosokai, T.

    2005-11-11

    We have measured the temporal shortening of an ultraintense laser pulse interacting with an underdense plasma. When interacting with strongly nonlinear plasma waves, the laser pulse is shortened from 38{+-}2 fs to the 10-14 fs level, with a 20% energy efficiency. The laser ponderomotive force excites a wakefield, which, along with relativistic self-phase modulation, broadens the laser spectrum and subsequently compresses the pulse. This mechanism is confirmed by 3D particle in cell simulations.

  13. Observation of laser-pulse shortening in nonlinear plasma waves.

    PubMed

    Faure, J; Glinec, Y; Santos, J J; Ewald, F; Rousseau, J-P; Kiselev, S; Pukhov, A; Hosokai, T; Malka, V

    2005-11-11

    We have measured the temporal shortening of an ultraintense laser pulse interacting with an underdense plasma. When interacting with strongly nonlinear plasma waves, the laser pulse is shortened from 38 +/- 2 fs to the 10-14 fs level, with a 20% energy efficiency. The laser ponderomotive force excites a wakefield, which, along with relativistic self-phase modulation, broadens the laser spectrum and subsequently compresses the pulse. This mechanism is confirmed by 3D particle in cell simulations. PMID:16384066

  14. Energy coupling to the plasma in repetitive nanosecond pulse discharges

    SciTech Connect

    Adamovich, Igor V.; Nishihara, Munetake; Choi, Inchul; Uddi, Mruthunjaya; Lempert, Walter R.

    2009-11-15

    A new analytic quasi-one-dimensional model of energy coupling to nanosecond pulse discharge plasmas in plane-to-plane geometry has been developed. The use of a one-dimensional approach is based on images of repetitively pulsed nanosecond discharge plasmas in dry air demonstrating that the plasma remains diffuse and uniform on a nanosecond time scale over a wide range of pressures. The model provides analytic expressions for the time-dependent electric field and electron density in the plasma, electric field in the sheath, sheath boundary location, and coupled pulse energy. The analytic model predictions are in very good agreement with numerical calculations. The model demonstrates that (i) the energy coupled to the plasma during an individual nanosecond discharge pulse is controlled primarily by the capacitance of the dielectric layers and by the breakdown voltage and (ii) the pulse energy coupled to the plasma during a burst of nanosecond pulses decreases as a function of the pulse number in the burst. This occurs primarily because of plasma temperature rise and resultant reduction in breakdown voltage, such that the coupled pulse energy varies approximately proportionally to the number density. Analytic expression for coupled pulse energy scaling has been incorporated into the air plasma chemistry model, validated previously by comparing with atomic oxygen number density measurements in nanosecond pulse discharges. The results of kinetic modeling using the modified air plasma chemistry model are compared with time-resolved temperature measurements in a repetitively pulsed nanosecond discharge in air, by emission spectroscopy, and purely rotational coherent anti-Stokes Raman spectroscopy showing good agreement.

  15. Energy coupling to the plasma in repetitive nanosecond pulse discharges

    NASA Astrophysics Data System (ADS)

    Adamovich, Igor V.; Nishihara, Munetake; Choi, Inchul; Uddi, Mruthunjaya; Lempert, Walter R.

    2009-11-01

    A new analytic quasi-one-dimensional model of energy coupling to nanosecond pulse discharge plasmas in plane-to-plane geometry has been developed. The use of a one-dimensional approach is based on images of repetitively pulsed nanosecond discharge plasmas in dry air demonstrating that the plasma remains diffuse and uniform on a nanosecond time scale over a wide range of pressures. The model provides analytic expressions for the time-dependent electric field and electron density in the plasma, electric field in the sheath, sheath boundary location, and coupled pulse energy. The analytic model predictions are in very good agreement with numerical calculations. The model demonstrates that (i) the energy coupled to the plasma during an individual nanosecond discharge pulse is controlled primarily by the capacitance of the dielectric layers and by the breakdown voltage and (ii) the pulse energy coupled to the plasma during a burst of nanosecond pulses decreases as a function of the pulse number in the burst. This occurs primarily because of plasma temperature rise and resultant reduction in breakdown voltage, such that the coupled pulse energy varies approximately proportionally to the number density. Analytic expression for coupled pulse energy scaling has been incorporated into the air plasma chemistry model, validated previously by comparing with atomic oxygen number density measurements in nanosecond pulse discharges. The results of kinetic modeling using the modified air plasma chemistry model are compared with time-resolved temperature measurements in a repetitively pulsed nanosecond discharge in air, by emission spectroscopy, and purely rotational coherent anti-Stokes Raman spectroscopy showing good agreement.

  16. AFM and pulsed laser ablation methods for Cultural Heritage: application to archeometric analysis of stone artifacts

    NASA Astrophysics Data System (ADS)

    Barberio, M.; Veltri, S.; Stranges, F.; Bonanno, A.; Xu, F.; Antici, P.

    2015-09-01

    In this paper, we introduce the use of the atomic force microscope (AFM) and of the pulsed laser ablation as methods for morphological diagnostic with nanoscale precision of archeological artifacts and corrosive patina removal from stone artifacts. We test our methodology on stone artifacts extracted from the Church of Sotterra (located in Calabria, South Italy). The AFM microscopy was compared with different petrographic, chemical, optical and morphological analysis methods for identifying the textural characteristics, evaluating the state of preservation and formulating some hypotheses about the provenance and composition of the impurity patina located on the artifact surfaces. We demonstrate that with the nanometric precision obtained with AFM microscopy, it is possible to distinguish the different states of preservation, much better than using conventional petrographic methods. The surface's roughness is evaluated from very small artifact's fragments, reducing the coring at micrometric scale with a minimal damage to the artworks. After the diagnosis, we performed restoration tests using the pulsed laser ablation (PLA) method and compared it with the more common micro-sandblasting under dry conditions. We find that the PLA is highly effective for the removal of the surficial patina, with a control of a few hundreds of nanometers in the cleaning of surface, without introducing chemical or morphological damages to the artifacts. Moreover, PLA can be easily implemented in underwater conditions; this has the great advantage that stone and pottery artifacts for marine archeological sites do not need to be removed from the site.

  17. Damage morphology and mechanism in ablation cutting of thin glass sheets with picosecond pulsed lasers

    NASA Astrophysics Data System (ADS)

    Sun, Mingying; Eppelt, Urs; Hartmann, Claudia; Schulz, Wolfgang; Zhu, Jianqiang; Lin, Zunqi

    2016-06-01

    We experimentally investigated the morphology and mechanism of laser-induced damage in the ablation cutting of thin glass sheets with picosecond pulsed lasers and we compared the experimental results to our models. After several passes of laser ablation, we observed two different kinds of damage morphologies on the cross-section of the cut channel. They are distinguished to be the damage region caused by high-density free-electrons and the heat-affected zone due to the heat accumulation, respectively. Furthermore, micro-cracks can be observed on the top surface of the workpiece near the cut edge. The nano-cracks could be generated by high energy free-electrons but opened and developed to be visible micro-cracks by thermal stress generated in the heat-affected zone. The crack length was proportional to the volume of heat-affected zone. Heat-affected-zone and visible-cracks free conditions of glass cutting were achieved by controlling the repetition rate and spatial overlap of laser pulses.

  18. Quantitative Analysis of Plasma Ablation Using Inverse Wire Array Z-pinches

    SciTech Connect

    Harvey-Thompson, A. J.; Lebedev, S. V.; Bland, S. N.; Chittenden, J. P.; Hall, G. N.; Ning, C.; Suzuki-Vidal, F.; Bott, S. C.

    2009-01-21

    An inverse (exploding) wire array configuration, in which the wires form a cylinder around a current carrying electrode on axis, was used to study the ablation phase of the pinch. This configuration allows the parameters of the plasma from individual wires of the array to be measured as the ablated plasma streams propagate in the outward radial direction. The density distribution and the evolution of the natural mode of modulation of the ablation was measured with interferometry and soft x-ray imaging. Measurements of the voltage across the array, which in this configuration is determined by the private magnetic flux around the individual wires, allows information on the localisation of the current to be obtained.

  19. Filamentation of ultrashort laser pulses propagating in tenuous plasmas

    SciTech Connect

    Andreev, N. E.; Gorbunov, L. M.; Mora, P.; Ramazashvili, R. R.

    2007-08-15

    The filamentation of ultrashort laser pulses (shorter than a plasma period) propagating in tenuous plasmas is studied. In this regime relativistic and ponderomotive nonlinearities tend to cancel each other. Time-dependent residual nonlinear plasma response brings about the dynamical filamentation with the maximum unstable transverse wave number decreasing in the course of laser pulse propagation. Dynamics of a hot spot that seeds the filamentation instability is studied numerically and reveals a good agreement with the analytical results.

  20. Investigation of factors affecting the synthesis of nano-cadmium sulfide by pulsed laser ablation in liquid environment

    NASA Astrophysics Data System (ADS)

    Darwish, Ayman M.; Eisa, Wael H.; Shabaka, Ali A.; Talaat, Mohamed H.

    2016-01-01

    Pulsed laser ablation in a liquid medium is a promising technique as compared to the other synthetic methods to synthesize different materials in nanoscale form. The laser parameters (e.g., wavelength, pulse width, fluence, and repetition frequency) and liquid medium (e.g., aqueous/nonaqueous liquid or solution with surfactant) were tightly controlled during and after the ablation process. By optimizing these parameters, the particle size and distribution of materials can be adjusted. The UV-vis absorption spectra and weight changes of targets were used for the characterization and comparison of products.

  1. Transmission of 1064 nm laser radiation during ablation with an ultra-short pulse laser (USPL) system

    NASA Astrophysics Data System (ADS)

    Schelle, Florian; Meister, Jörg; Oehme, Bernd; Frentzen, Matthias

    2012-01-01

    During ablation of oral hard tissue with an USPL system a small amount of the incident laser power does not contribute to the ablation process and is being transmitted. Partial transmission of ultra-short laser pulses could potentially affect the dental pulp. The aim of this study was to assess the transmission during ablation and to deduce possible risks for the patient. The study was performed with an Nd:YVO4 laser, emitting pulses with a duration of 8 ps at a wavelength of 1064 nm. A repetition rate of 500 kHz and an average power of 9 W were chosen to achieve high ablation efficiency. A scanner system created square cavities with an edge length of 1 mm. Transmission during ablation of mammoth ivory and dentin slices with a thickness of 2 mm and 5 mm was measured with a power meter, placed directly beyond the samples. Effects on subjacent blood were observed by ablating specimens placed in contact to pork blood. In a separate measurement the temperature increase during ablation was monitored using an infrared camera. The influence of transmission was assessed by tuning down the laser to the corresponding power and then directly irradiating the blood. Transmission during ablation of 2 mm specimens was about 7.7% (ivory) and 9.6% (dentin) of the incident laser power. Ablation of specimens directly in contact to blood caused coagulation at longer irradiation times (t~18s). Direct irradiation of blood with the transmitted power provoked bubbling and smoke formation. Temperature measurements identified heat generation as the main reason for the observed coagulation.

  2. Intense isolated attosecond pulse generation from relativistic laser plasmas using few-cycle laser pulses

    NASA Astrophysics Data System (ADS)

    Ma, Guangjin; Dallari, William; Borot, Antonin; Krausz, Ferenc; Yu, Wei; Tsakiris, George D.; Veisz, Laszlo

    2015-03-01

    We have performed a systematic study through particle-in-cell simulations to investigate the generation of attosecond pulse from relativistic laser plasmas when laser pulse duration approaches the few-cycle regime. A significant enhancement of attosecond pulse energy has been found to depend on laser pulse duration, carrier envelope phase, and plasma scale length. Based on the results obtained in this work, the potential of attaining isolated attosecond pulses with ˜100 μJ energy for photons >16 eV using state-of-the-art laser technology appears to be within reach.

  3. Intense isolated attosecond pulse generation from relativistic laser plasmas using few-cycle laser pulses

    SciTech Connect

    Ma, Guangjin; Dallari, William; Borot, Antonin; Tsakiris, George D.; Veisz, Laszlo; Krausz, Ferenc; Yu, Wei

    2015-03-15

    We have performed a systematic study through particle-in-cell simulations to investigate the generation of attosecond pulse from relativistic laser plasmas when laser pulse duration approaches the few-cycle regime. A significant enhancement of attosecond pulse energy has been found to depend on laser pulse duration, carrier envelope phase, and plasma scale length. Based on the results obtained in this work, the potential of attaining isolated attosecond pulses with ∼100 μJ energy for photons >16 eV using state-of-the-art laser technology appears to be within reach.

  4. Plasma Discharge Process in a Pulsed Diaphragm Discharge System

    NASA Astrophysics Data System (ADS)

    Duan, Jianjin; Hu, Jue; Zhang, Chao; Wen, Yuanbin; Meng, Yuedong; Zhang, Chengxu

    2014-12-01

    As one of the most important steps in wastewater treatment, limited study on plasma discharge process is a key challenge in the development of plasma applications. In this study, we focus on the plasma discharge process of a pulsed diaphragm discharge system. According to the analysis, the pulsed diaphragm discharge proceeds in seven stages: (1) Joule heating and heat exchange stage; (2) nucleated site formation; (3) plasma generation (initiation of the breakdown stage); (4) avalanche growth and plasma expansion; (5) plasma contraction; (6) termination of the plasma discharge; and (7) heat exchange stage. From this analysis, a critical voltage criterion for breakdown is obtained. We anticipate this finding will provide guidance for a better application of plasma discharges, especially diaphragm plasma discharges.

  5. Time-resolved study of the plasma-plume emission during the nanosecond ablation of lithium fluoride

    NASA Astrophysics Data System (ADS)

    Camacho, J. J.; Diaz, L.; Cid, J. P.; Poyato, J. M. L.

    2013-10-01

    The properties of the plasma-plume accompanying the pulsed laser ablation of lithium fluoride (LiF) at medium-vacuum conditions (4 Pa) were studied by a combination of spatially and temporally resolved optical emission spectroscopy. The laser-induced plasma at CO2 laser intensities ranging from 0.18 to 4.7 GW × cm- 2 was found strongly ionized in F+, Li+, F2 +, and F3 + species and rich in neutral lithium and fluorine atoms. The temporal behavior of excited Li atoms and ionized excited species F+, Li+, F2 +, and F3 + is reported. The results show a faster decay of the continuum emission and Li+, F3 +, and F2 + ionic species than in the case of F+ and neutral Li atoms. The velocity distributions of atomic and ionic species are obtained from time-of-flight measurements. Electron density and excitation temperature in the laser-induced plasma were estimated from the analysis of spectral data at various delay times from the CO2 laser pulse incidence. From the intensity decay of Li+, F+, F2 + and F3 + with the delay time, we have estimated the three-body electron-ion recombination rate constants for these species.

  6. Plasma regimes in high power pulsed magnetron sputtering

    NASA Astrophysics Data System (ADS)

    de Los Arcos, Teresa

    2013-09-01

    High Power Pulsed Magnetron Sputtering (HPPMS) is a relatively recent variation of magnetron sputtering where high power is applied to the magnetron in short pulses. The result is the formation of dense transient plasmas with a high fraction of ionized species, ideally leading to better control of film growth through substrate bias. However, the broad range of experimental conditions accessible in pulsed discharges results in bewildering variations in current and voltage pulse shapes, pulse power densities, etc, which represent different discharge behaviors, making it difficult to identify relevant deposition conditions. The complexity of the plasma dynamics is evident. Within each pulse, plasma characteristics such as plasma composition, density, gas rarefaction, spatial distribution, degree of self-sputtering, etc. vary with time. A recent development has been the discovery that the plasma emission can self-organize into well-defined regions of high and low plasma emissivity above the racetrack (spokes), which rotate in the direction given by the E ×B drift and that significantly influence the transport mechanisms in HPPMS. One seemingly universal characteristic of HPPMS plasmas is the existence of well defined plasma regimes for different power ranges. These regimes are clearly differentiated in terms of plasma conductivity, plasma composition and spatial plasma self-organization. We will discuss the global characteristics of these regimes in terms of current-voltage characteristics, energy-resolved QMS and OES analysis, and fast imaging. In particular we will discuss how the reorganization of the plasma emission into spokes is associated only to specific regimes of high plasma conductivity. We will also briefly discuss the role of the target in shaping the characteristics of the HPPMS plasma, since sputtering is a surface-driven process. This work was supported by the Deutsche Forschungsgemeinschaft (DFG) within the framework of the SFB-TR87.

  7. Thrust Stand Measurements of a Conical Pulsed Inductive Plasma Thruster

    NASA Technical Reports Server (NTRS)

    Hallock, Ashley K.; Polzin, Kurt A.; Emsellem, Gregory D.

    2012-01-01

    Pulsed inductive plasma thrusters [1-3] are spacecraft propulsion devices in which electrical energy is capacitively stored and then discharged through an inductive coil. The thruster is electrodeless, with a time-varying current in the coil interacting with a plasma covering the face of the coil to induce a plasma current. Propellant is accelerated and expelled at a high exhaust velocity (O(10-100 km/s)) by the Lorentz body force arising from the interaction of the magnetic field and the induced plasma current. While this class of thruster mitigates the life-limiting issues associated with electrode erosion, pulsed inductive plasma thrusters can su er from both high pulse energy requirements imposed by the voltage demands of inductive propellant ionization, and low propellant utilization efficiencies. The Microwave Assisted Discharge Inductive Plasma Accelerator (MAD-IPA)[4], shown in Fig. 1 is a pulsed inductive plasma thruster that is able to operate at lower pulse energies by partially ionizing propellant with an electron cyclotron resonance (ECR) discharge inside a conical inductive coil whose geometry serves to potentially increase propellant and plasma plume containment relative to at coil geometries. The ECR plasma is created with the use of permanent mag- nets arranged to produce a thin resonance region along the inner surface of the coil, restricting plasma formation and, in turn, current sheet formation to areas of high magnetic coupling to the driving coil.

  8. Group velocity and pulse lengthening of mismatched laser pulses in plasma channels

    SciTech Connect

    Schroeder, Carl; Benedetti, Carlo; Esarey, Eric; van Tilborg, Jeroen; Leemans, Wim

    2011-07-07

    Analytic solutions are presented to the non-paraxial wave equation describing an ultra-short, low-power, laser pulse propagating in aplasma channel. Expressions for the laser pulse centroid motion and laser group velocity are derived, valid for matched and mismatchedpropagation in a parabolic plasma channel, as well as in vacuum, for an arbitrary Laguerre-Gaussian laser mode. The group velocity of amismatched laser pulse, for which the laser spot size is strongly oscillating, is found to be independent of propagation distance andsignificantly less than that of a matched pulse. Laser pulse lengthening of a mismatched pulse owing to laser mode slippage isexamined and found to dominate over that due to dispersive pulse spreading for sufficiently long pulses. Analytic results are shown tobe in excellent agreement with numerical solutions of the full Maxwell equations coupled to the plasma response. Implications for plasmachannel diagnostics are discussed.

  9. Controlling plasma channels through ultrashort laser pulse filamentation

    NASA Astrophysics Data System (ADS)

    Ionin, Andrey A.; Seleznev, Leonid V.; Sunchugasheva, Elena S.

    2013-10-01

    A review of studies fulfilled at the Lebedev Institute in collaboration with the Moscow State University and Institute of Atmospheric Optics in Tomsk (Siberia) on influence of various characteristics of ultrashort laser pulse on plasma channels formed under its filamentation is presented. Filamentation of high-power laser pulses with wavefront controlled by a deformable mirror, with cross-sections spatially formed by various diaphragms and with different wavelengths was experimentally and numerically studied. An application of plasma channels formed due to filamentation of ultrashort laser pulse including a train of such pulses for triggering and guiding electric discharge is discussed.

  10. Pulse evolution and plasma-wave phase velocity in channel-guided laser-plasma accelerators.

    PubMed

    Benedetti, C; Rossi, F; Schroeder, C B; Esarey, E; Leemans, W P

    2015-08-01

    The self-consistent laser evolution of an intense, short-pulse laser exciting a plasma wave and propagating in a preformed plasma channel is investigated, including the effects of pulse steepening and energy depletion. In the weakly relativistic laser intensity regime, analytical expressions for the laser energy depletion, pulse self-steepening rate, laser intensity centroid velocity, and phase velocity of the plasma wave are derived and validated numerically. PMID:26382537

  11. High velocity pulsed plasma thermal spray

    NASA Astrophysics Data System (ADS)

    Witherspoon, F. D.; Massey, D. W.; Kincaid, R. W.; Whichard, G. C.; Mozhi, T. A.

    2002-03-01

    The quality and durability of coatings produced by many thermal spray techniques could be improved by increasing the velocity with which coating particles impact the substrate. Additionally, better control of the chemical and thermal environment seen by the particles during flight is crucial to the quality of the coating. A high velocity thermal spray device is under development through a Ballistic Missile Defense Organization Small Business Innovation Research (SBIR) project, which provides significantly higher impact velocity for accelerated particles than is currently available with existing thermal spray devices. This device utilizes a pulsed plasma as the accelerative medium for powders introduced into the barrel. Recent experiments using a particle imaging diagnostic system showed that the device can accelerate stainless steel and WC-Co powders to velocities ranging from 1500 to 2200 m/s. These high velocities are accomplished without the use of combustible gases and without the need of a vacuum chamber, while maintaining an inert atmosphere for the particles during acceleration. The high velocities corresponded well to modeling predictions, and these same models suggest that velocities as high as 3000 m/s or higher are possible.

  12. External Pulsed Plasma Propulsion (EPPP) Analysis Maturation

    NASA Technical Reports Server (NTRS)

    Bonometti, Joesph A.; Morton, P. Jeff; Schmidt, George R. (Technical Monitor)

    2000-01-01

    External Pulsed Plasma Propulsion (EPPP) systems are at the stage of engineering infancy with evolving paradigms for application. performance and general characteristics. Recent efforts have focused on an approach that employs existing technologies with near term EPPP development for usage in interplanetary exploration and asteroid/comet deflection. if mandated. The inherent advantages of EPPP are discussed and its application to a variety of propulsion concepts is explored. These include, but are not limited to, utilizing energy sources such as fission. fusion and antimatter, as well as, improved chemical explosives. A mars mission scenario is presented as a demonstration of its capability using existing technologies. A suggested alternate means to improve EPPP efficiencies could also lead to a heavy lift (non-nuclear) launch vehicle capability. Conceivably, true low-cost, access to space is possible using advanced explosive propellants and/or coupling the EPPP vehicle to a "beam propellant" concept. EPPP systems appear to offer an approach that can potentially cover ETO through interstellar transportation capability. A technology roadmap is presented that shows mutual benefits pertaining to a substantial number of existing space propulsion and research areas.

  13. Evaluation of Pulsed Plasma Thruster Micropulsing

    NASA Technical Reports Server (NTRS)

    Arrington, Lynn

    2004-01-01

    This paper evaluates the concept of pulsed plasma thruster (PPT) micropulsing. Micropulsing was a premise behind a power processing unit (PPU) and an energy storage unit (ESU) design that for certain mission profiles, it was advantageous to operate a PPT at lower energy but higher frequency rather than at a higher energy but lower frequency. This premise allows for reductions in the ESU volume and mass without paying a penalty in thrust. To complete the evaluation, an independent spark plug initiation unit, a high voltage power supply and a variety of mica foil capacitors at 2.6, 5, 10, and 20 capacitance were used to conduct a series of tests on a single PPT to map performance levels of thrust, impulse bit, efficiency and specific impulse over a comparable power range. Testing at NASA Glenn Research Center was conducted with breadboard PPT hardware. The test results showed that operating in the lower energy ESU micropulsing mode produced similar thrust levels to a higher energy ESU operating at high power level. Further testing however showed a reduction in specific impulse and efficiency when the smaller capacitances were used at the highest power levels. This would require more fuel mass for a mission that was predominately high power, potentially negating the ESU mass savings. Therefore, micropulsing is advantageous where most of a mission profile occurs at low power, but retains the ability to conduct high thrust maneuvers when necessary.

  14. High-Speed, Integrated Ablation Cell and Dual Concentric Injector Plasma Torch for Laser Ablation-Inductively Coupled Plasma Mass Spectrometry.

    PubMed

    Douglas, David N; Managh, Amy J; Reid, Helen J; Sharp, Barry L

    2015-11-17

    In recent years, laser ablation-inductively coupled plasma mass spectrometry (LA-ICPMS) has gained increasing importance for biological analysis, where ultratrace imaging at micrometer resolution is required. However, while undoubtedly a valuable research tool, the washout times and sensitivity of current technology have restricted its routine and clinical application. Long periods between sampling points are required to maintain adequate spatial resolution. Additionally, temporal signal dispersion reduces the signal-to-noise ratio, which is a particular concern when analyzing discrete samples, such as individual particles or cells. This paper describes a novel, two-volume laser ablation cell and integrated ICP torch designed to minimize aerosol dispersion for fast, efficient sample transport. The holistic design utilizes a short, continuous diameter fused silica conduit, which extends from the point of ablation, through the ICP torch, and into the base of the plasma. This arrangement removes the requirement for a dispersive component for argon addition, and helps to keep the sample on axis with the ICP cone orifice. Hence, deposition of sample on the cones is theoretically reduced with a resulting improvement in the absolute sensitivity (counts per unit mole). The system described here achieved washouts of 1.5, 3.2, and 4.9 ms for NIST 612 glass, at full width half, 10%, and 1% maximum, respectively, with an 8-14-fold improvement in absolute sensitivity, compared to a single volume ablation cell. To illustrate the benefits of this performance, the system was applied to a contemporary bioanalytical challenge, specifically the analysis of individual biological cells, demonstrating similar improvements in performance. PMID:26460246

  15. Plasma lenses for ultrashort multi-petawatt laser pulses

    SciTech Connect

    Palastro, J. P.; Gordon, D.; Hafizi, B.; Johnson, L. A.; Peñano, J.; Hubbard, R. F.; Helle, M.; Kaganovich, D.

    2015-12-15

    An ideal plasma lens can provide the focusing power of a small f-number, solid-state focusing optic at a fraction of the diameter. An ideal plasma lens, however, relies on a steady-state, linear laser pulse-plasma interaction. Ultrashort multi-petawatt (MPW) pulses possess broad bandwidths and extreme intensities, and, as a result, their interaction with the plasma lens is neither steady state nor linear. Here, we examine nonlinear and time-dependent modifications to plasma lens focusing, and show that these result in chromatic and phase aberrations and amplitude distortion. We find that a plasma lens can provide enhanced focusing for 30 fs pulses with peak power up to ∼1 PW. The performance degrades through the MPW regime, until finally a focusing penalty is incurred at ∼10 PW.

  16. Plasma lenses for ultrashort multi-petawatt laser pulses

    NASA Astrophysics Data System (ADS)

    Palastro, J. P.; Gordon, D.; Hafizi, B.; Johnson, L. A.; Peñano, J.; Hubbard, R. F.; Helle, M.; Kaganovich, D.

    2015-12-01

    An ideal plasma lens can provide the focusing power of a small f-number, solid-state focusing optic at a fraction of the diameter. An ideal plasma lens, however, relies on a steady-state, linear laser pulse-plasma interaction. Ultrashort multi-petawatt (MPW) pulses possess broad bandwidths and extreme intensities, and, as a result, their interaction with the plasma lens is neither steady state nor linear. Here, we examine nonlinear and time-dependent modifications to plasma lens focusing, and show that these result in chromatic and phase aberrations and amplitude distortion. We find that a plasma lens can provide enhanced focusing for 30 fs pulses with peak power up to ˜1 PW. The performance degrades through the MPW regime, until finally a focusing penalty is incurred at ˜10 PW.

  17. Time-resolved studies of particle effects in laser ablation inductively coupled plasma-mass spectrometry

    SciTech Connect

    Perdian, D.; Bajic, S.; Baldwin, D.; Houk, R.

    2007-11-13

    Time resolved signals in laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) are studied to determine the influence of experimental parameters on ICP-induced fractionation effects. Differences in sample composition and morphology, i.e., ablating brass, glass, or dust pellets, have a profound effect on the time resolved signal. Helium transport gas significantly decreases large positive signal spikes arising from large particles in the ICP. A binder for pellets also reduces the abundance and amplitude of spikes in the signal. MO{sup +} ions also yield signal spikes, but these MO{sup +} spikes generally occur at different times from their atomic ion counterparts.

  18. Selective Ablation of Thin Films with Picosecond-Pulsed Lasers for Solar Cells

    NASA Astrophysics Data System (ADS)

    Račiukaitis, G.; Gečys, P.; Gedvilas, M.; Regelskis, K.; Voisiat, B.

    2010-10-01

    Functional thin-films are of high importance in modern electronics for flat panel displays, photovoltaics, flexible and organic electronics. Versatile technologies are required for patterning thin-film materials on rigid and flexible substrates. The large-area applications of thin films such as photovoltaics need high speed and simple to use techniques. Ultra-short laser processing with its flexibility is one of the ways to achieve high quality material etching but optimization of the processes is required to meet specific needs of the applications. Lasers with picosecond pulse duration were applied in selective ablation of conducting, semi-conducting and isolating films in the complex multilayered thin-film solar cells based on amorphous Si and CuInxGa(1-x)Se2 (CIGS) deposited on glass and polymer substrates. Modeling of energy transition between the layers and temperature evolution was performed to understand the processes. Selection of the right laser wavelength was important to keep the energy coupling in a well defined volume at the interlayer interface. Ultra-short pulses ensured high energy input rate into absorbing material permitting peeling of the layers with no influence on the remaining material. Use of high repetition rate lasers with picosecond pulse duration offers new possibilities for high quality and efficiency patterning of advanced materials for thin-film electronics.

  19. Pulsed laser generation of ultrasound in a metal plate between the melting and ablation thresholds

    SciTech Connect

    Every, A. G.; Utegulov, Z. N.; Veres, I. A.

    2015-03-31

    The generation of ultrasound in a metal plate exposed to nanosecond pulsed laser heating, sufficient to cause melting but not ablation, is treated. Consideration is given to the spatial and temporal profiles of the laser pulse, penetration of the laser beam into the sample, the evolution of the melt pool, and thermal conduction in the melt and surrounding solid. The excitation of the ultrasound takes place over a few nanoseconds, and occurs predominantly within the thermal diffusion length of a micron or so beneath the surface. Because of this, the output of the thermal simulations can be represented as axially symmetric transient radial and normal surface force distributions. The epicentral displacement response at the opposite surface to these forces is obtained by two methods, the one based on the elastodynamic Green’s functions for plate geometry determined by the Cagniard generalized ray method, and the other using a finite element numerical method. The two approaches are in very close agreement. Numerical simulations are reported of the epicentral displacement response of a 3.12mm thick tungsten plate irradiated with a 4 ns pulsed laser beam with Gaussian spatial profile, at intensities below and above the melt threshold. Comparison is made between results obtained using available temperature dependent thermophysical data, and room temperature materials constants except near the melting point.

  20. Pulsed laser generation of ultrasound in a metal plate between the melting and ablation thresholds

    NASA Astrophysics Data System (ADS)

    Every, A. G.; Utegulov, Z. N.; Veres, I. A.

    2015-03-01

    The generation of ultrasound in a metal plate exposed to nanosecond pulsed laser heating, sufficient to cause melting but not ablation, is treated. Consideration is given to the spatial and temporal profiles of the laser pulse, penetration of the laser beam into the sample, the evolution of the melt pool, and thermal conduction in the melt and surrounding solid. The excitation of the ultrasound takes place over a few nanoseconds, and occurs predominantly within the thermal diffusion length of a micron or so beneath the surface. Because of this, the output of the thermal simulations can be represented as axially symmetric transient radial and normal surface force distributions. The epicentral displacement response at the opposite surface to these forces is obtained by two methods, the one based on the elastodynamic Green's functions for plate geometry determined by the Cagniard generalized ray method, and the other using a finite element numerical method. The two approaches are in very close agreement. Numerical simulations are reported of the epicentral displacement response of a 3.12mm thick tungsten plate irradiated with a 4 ns pulsed laser beam with Gaussian spatial profile, at intensities below and above the melt threshold. Comparison is made between results obtained using available temperature dependent thermophysical data, and room temperature materials constants except near the melting point.

  1. Multilayered metal oxide thin film gas sensors obtained by conventional and RF plasma-assisted laser ablation

    NASA Astrophysics Data System (ADS)

    Mitu, B.; Marotta, V.; Orlando, S.

    2006-04-01

    Multilayered thin films of In 2O 3 and SnO 2 have been deposited by conventional and RF plasma-assisted reactive pulsed laser ablation, with the aim to evaluate their behaviour as toxic gas sensors. The depositions have been carried out by a frequency doubled Nd-YAG laser ( λ = 532 nm, τ = 7 ns) on Si(1 0 0) substrates, in O 2 atmosphere. The thin films have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrical resistance measurements. A comparison of the electrical response of the simple (indium oxide, tin oxide) and multilayered oxides to toxic gas (nitric oxide, NO) has been performed. The influence on the structural and electrical properties of the deposition parameters, such as substrate temperature and RF power is reported.

  2. Determination of bromine and tin compounds in plastics using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS).

    PubMed

    İzgi, Belgin; Kayar, Murat

    2015-07-01

    The polybrominated flame retardants and organotin compounds were screened in terms of bromine and tin content using laser ablation inductively coupled plasma mass spectrometry in plastics. The calibration standards were prepared using the fused-disk technique, and all samples were investigated under optimal conditions. Using a central composite experimental design, laser parameters, laser energy, pulse rate, scan rate and spot size were identified. The detection limits of the method were 1000 mgkg(-1) and 1600 mgkg(-1) for bromide and tin, whereas the relative standard deviation (%) values of the analysis were 9% and 6% (n=3) for ERM EC681k with 770 ± 70 mgkg(-1) Br and 86 ± 6 mgkg(-1) Sn respectively, and 106-115% of Br and 102-104% of Sn were observed for the tetrabromobisphenol A and butyltin trichloride spike plastics, respectively. PMID:25882416

  3. Ultrasound-guided greater occipital nerve blocks and pulsed radiofrequency ablation for diagnosis and treatment of occipital neuralgia.

    PubMed

    Vanderhoek, Matthew David; Hoang, Hieu T; Goff, Brandon

    2013-09-01

    Occipital neuralgia is a condition manifested by chronic occipital headaches and is thought to be caused by irritation or trauma to the greater occipital nerve (GON). Treatment for occipital neuralgia includes medications, nerve blocks, and pulsed radiofrequency ablation (PRFA). Landmark-guided GON blocks are the mainstay in both the diagnosis and treatment of occipital neuralgia. Ultrasound is being utilized more and more in the chronic pain clinic to guide needle advancement when performing procedures; however, there are no reports of ultrasound used to guide a diagnostic block or PRFA of the GON. We report two cases in which ultrasound was used to guide diagnostic greater occipital nerve blocks and greater occipital nerve pulsed radiofrequency ablation for treatment of occipital neuralgia. Two patients with occipital headaches are presented. In Case 1, ultrasound was used to guide diagnostic blocks of the greater occipital nerves. In Case 2, ultrasound was utilized to guide placement of radiofrequency probes for pulsed radiofrequency ablation of the greater occipital nerves. Both patients reported immediate, significant pain relief, with continued pain relief for several months. Further study is needed to examine any difference in outcomes or morbidity between the traditional landmark method versus ultrasound-guided blocks and pulsed radiofrequency ablation of the greater occipital nerves. PMID:24282778

  4. Spatial investigations of ion and electron time of flight in laser ablated ZnO plasma

    NASA Astrophysics Data System (ADS)

    Joshy, N. V.; Jayaraj, M. K.

    2010-02-01

    The time of flight (TOF) spectra of ions and electrons of laser ablated ZnO:Ga plasma plume were recorded. The laser fluence was varied from 2.55 Jcm-2 to 17.85 Jcm-2 and the ablation was carried out in vacuum and N2O ambient pressure ranging from 0.0001 mbar to 0.1 mbar. The TOF spectra were recorded at positions 10 mm to 50 mm from the target surface along the direction normal to the surface. Ion acceleration and corresponding electron deceleration were detected in the plasma due to the formation of electric double layer during plasma expansion. Twin peaks were recorded in the ion TOF spectra-corresponding to accelerated and thermal ions, while two categories of thermal electrons were detected in electron TOF spectra. The behaviour of these ions and electrons is studied as a function of laser fluence, ambient gas pressure and distance from the target surface.

  5. Microwave Frequency Transitions Requiring Laser Ablated Uranium Metal Discovered Using Chirp-Pulse Fourier Transform Spectroscopy

    NASA Astrophysics Data System (ADS)

    Long, B. E.; Cooke, S. A.

    2014-06-01

    A rod of depleted uranium metal (mp = 1,132° C) has been ablated with the fundamental operating frequency of a Nd:YAG laser. The resulting ablation plume of uranium was then mixed with argon gas and expanded between the transmit/receive horn antennae of a chirp-pulse Fourier transform microwave spectrometer. The recorded spectra show nine strong transitions which are not present when the laser is not used in the experimental procedure. A series of experiments in which the backing gas conditions were altered provides evidence that the nine observed transitions are carried by the same species. Should the transitions be from one species it is most likely an asymmetric top. The transitions persist even when ultra-pure argon is used as the sole backing gas. The oxide coating of the uranium metal likely provides a source of oxygen and, presently, the ``top" candidate for the unknown molecule is UO_3, which is known to have C_2v symmetry. Double resonance experiments are planned to aid transition assignments. A plausible explanation for an elusive assignment to date is the presence of pseudo-rotation.

  6. Absorption of a laser light pulse in a dense plasma.

    NASA Technical Reports Server (NTRS)

    Mehlman-Balloffet, G.

    1973-01-01

    An experimental study of the absorption of a laser light pulse in a transient, high-density, high-temperature plasma is presented. The plasma is generated around a metallic anode tip by a fast capacitive discharge occurring in vacuum. The amount of transmitted light is measured for plasmas made of different metallic ions in the regions of the discharge of high electronic density. Variation of the transmission during the laser pulse is also recorded. Plasma electrons are considered responsible for the very high absorption observed.

  7. Depth profiling and imaging capabilities of an ultrashort pulse laser ablation time of flight mass spectrometer

    PubMed Central

    Cui, Yang; Moore, Jerry F.; Milasinovic, Slobodan; Liu, Yaoming; Gordon, Robert J.; Hanley, Luke

    2012-01-01

    An ultrafast laser ablation time-of-flight mass spectrometer (AToF-MS) and associated data acquisition software that permits imaging at micron-scale resolution and sub-micron-scale depth profiling are described. The ion funnel-based source of this instrument can be operated at pressures ranging from 10−8 to ∼0.3 mbar. Mass spectra may be collected and stored at a rate of 1 kHz by the data acquisition system, allowing the instrument to be coupled with standard commercial Ti:sapphire lasers. The capabilities of the AToF-MS instrument are demonstrated on metal foils and semiconductor wafers using a Ti:sapphire laser emitting 800 nm, ∼75 fs pulses at 1 kHz. Results show that elemental quantification and depth profiling are feasible with this instrument. PMID:23020378

  8. Dynamics of pulsed laser ablation in high-density carbon dioxide including supercritical fluid state

    NASA Astrophysics Data System (ADS)

    Urabe, Keiichiro; Kato, Toru; Stauss, Sven; Himeno, Shohei; Kato, Satoshi; Muneoka, Hitoshi; Baba, Motoyoshi; Suemoto, Tohru; Terashima, Kazuo

    2013-10-01

    To gain a better understanding of pulsed laser ablation (PLA) processes in high-density fluids, including gases, liquids, and supercritical fluids (SCFs), we have investigated the PLA dynamics in high-density carbon dioxide (CO2) using a time-resolved shadowgraph (SG) observation method. The SG images revealed that the PLA dynamics can be categorized into two domains that are separated by the gas-liquid coexistence curve and the Widom line, which forms a border between the gaslike and liquidlike domains of an SCF. Furthermore, a cavitation bubble observed in liquid CO2 near the critical point exhibited a particular characteristic: the formation of an inner bubble and an outer shell structure. The results indicate that the thermophysical properties of the reaction field generated by PLA can be dynamically tuned by controlling the solvent temperature and pressure, particularly near the critical point.

  9. Synthesis and characterization of Sb-doped ZnO microspheres by pulsed laser ablation

    NASA Astrophysics Data System (ADS)

    Nagasaki, Fumiaki; Shimogaki, Tetsuya; Tanaka, Toshinobu; Ikebuchi, Tatsuya; Ueyama, Takeshi; Fujiwara, Yuki; Higashihata, Mitsuhiro; Nakamura, Daisuke; Okada, Tatsuo

    2016-08-01

    We succeeded in synthesizing antimony (Sb)-doped zinc oxide (ZnO) microspheres by ablating a sintered ZnO target containing Sb in air. The structural properties of the microspheres were investigated by Raman scattering studies. The Zn–Sb related local vibrational mode (LVM) was detected around 238 cm‑1. Room-temperature photoluminescence (PL) properties of the microspheres were investigated under cw and pulsed laser excitations, and ultraviolet (UV) emission and whispering-gallery-mode (WGM) lasing were observed from the microspheres. Furthermore, a p–n heterojunction was formed between a single Sb-doped ZnO microsphere and an n-Al-doped ZnO thin film, and a good rectifying property with a turn-on voltage of approximately 1.8 V was observed in the current–voltage (I–V) characteristics across the junction.

  10. Stellate ganglion pulsed radiofrequency ablation for stretch induced complex regional pain syndrome type II

    PubMed Central

    Singh Rana, Shiv Pratap; Abraham, Mary; Gupta, Varun; Biswas, Shubhashish; Marda, Manish

    2015-01-01

    Complex regional pain syndrome (CRPS) following injury or nerve damage, as its name signifies, is a challenging entity, and its successful management requires a multidisciplinary approach. It not only manifests as severe pain, but also gives rise to functional disability, lack of sleep, lack of enjoyment of life and poor quality of life. Various pain interventional techniques have been described in the literature for the management of CRPS ranging from sympathetic blocks to spinal cord stimulator. A 34-year-old liver transplant donor, who developed position-induced right upper limb neuropathic pain suggestive of CRPS type II was managed initially with medications and later with stellate ganglion block under fluoroscopic guidance at cervical C7 position. Following an initial significant improvement in pain and allodynia, which was transient, a pulsed radiofrequency ablation of stellate ganglion was performed successfully to provide prolonged and sustained pain relief, which persisted up to 14 months of follow-up. PMID:26543471

  11. Origin of tunable photoluminescence from graphene quantum dots synthesized via pulsed laser ablation.

    PubMed

    Santiago, S R M; Lin, T N; Yuan, C T; Shen, J L; Huang, H Y; Lin, C A J

    2016-08-10

    A one-step synthesis of graphene quantum dots (GQDs) has been implemented using pulsed laser ablation (PLA) with carboxyl-functionalized multiwalled carbon nanotubes (MWCNTs). The synthesized GQDs with an average size smaller than 3 nm were obtained by the fragmentation of MWCNTs via oxidative cutting. The GQDs can generate tunable photoluminescence (PL) ranging from green to blue by controlling the PLA time. The PL spectrum (decay time) of the green GQDs remains unchanged under different excitation energies (emission energies), while that of the blue GQDs correlates with the excitation energy (emission energy). On the basis of the pH and temperature dependence of PL, we suggest that the localized intrinsic states associated with the sp(2) nanodomains and delocalized extrinsic states embedded on the GQD surface are responsible for blue and green emission in GQDs, respectively. PMID:27476476

  12. Silver nanoparticles grown in organic solvent PGMEA by pulsed laser ablation and their nonlinear optical properties.

    PubMed

    Shi, Hongfei; Wang, Can; Zhou, Yueliang; Jin, Kuijuan; Yang, Guozhen

    2012-10-01

    Well dispersed silver nanoparticles (AgNPs) with narrow size distribution have been grown in organic solvent propylene glycol monomethyl ether acetate (PGMEA) by pulsed laser ablation techniques. The presence of AgNPs in PGMEA solvent gives rise to an enhancement of the absorption and nonlinear optical properties due to the surface plasmon resonance induced by AgNPs. The shape and density of the AgNPs have been estimated by fitting the absorption spectra with a given model, and the results also show that an additional laser irradiation treatment can improve the monodispersity of the AgNPs and their nonlinear optical properties. The synthesis of AgNPs in PGMEA will facilitate adding AgNPs into organic functional materials especially for photoresist to modify their optical properties. PMID:23421153

  13. Photoemission Studies of Metallic Photocathodes Prepared by Pulsed Laser Ablation Deposition Technique

    SciTech Connect

    Fasano, V.; Lorusso, A.; Perrone, A.; De Rosa, H.; Cultrera, L.

    2010-11-10

    We present the results of our investigation on metallic films as suitable photocathodes for the production of intense electron beams in RF photoinjector guns. Pulsed laser ablation deposition technique was used for growing Mg and Y thin films onto Si and Cu substrates in high vacuum and at room temperature.Different diagnostic methods were used to characterize the thin films deposited on Si with the aim to optimize the deposition process. Photoelectron performances were investigated on samples deposited on Cu substrate in an ultra high vacuum photodiode chamber at 10{sup -7} Pa. Relatively high quantum efficiencies have been obtained for the deposited films, comparable to those of corresponding bulks. Samples could stay for several months in humid open air before being tested in a photodiode cell. The deposition process and the role of the photocathode surface contamination and its influence on the photoelectron performances are presented and discussed.

  14. Time-resolved studies of particle effects in laser ablation inductively coupled plasma-mass spectrometry

    SciTech Connect

    Perdian, D.; Bajic, S.; Baldwin, D.; Houk, R.

    2007-11-13

    Transient signal responses for ablated samples as a function of particle size and laser parameters are characterized. Data are acquired with time resolution of 5 or 6 ms per data point. Large positive spikes in signal are observed and increase in both amplitude and frequency with increasing particle size. Particle sizes are selected using a differential mobility analyzer. Spikes in the signal also increase with decreasing laser rastering rates. A comparison of lasers with pulse widths of 370 fs and 5 ns shows that shortening the pulse width significantly reduces the frequency and amplitude of positive spikes in signal. These large positive spikes are attributed to the vaporization, atomization, and ionization of individual large intact particles, which are considered to be a major cause of fractionation in laser ablation ICP-MS.

  15. A nonlinear plasma retroreflector for single pulse Compton backscattering

    NASA Astrophysics Data System (ADS)

    Palastro, J. P.; Kaganovich, D.; Gordon, D.; Hafizi, B.; Helle, M.; Penano, J.; Ting, A.

    2015-02-01

    Compton scattered x-rays can be generated using a configuration consisting of a single ultrashort laser pulse and a shaped gas target. Upon ionization the gas target serves as a plasma mirror that reflects the incident pulse providing a counter-propagating electromagnetic wiggler. While plasma mirrors are often conceived as linear Fresnel reflectors, we demonstrate that for high-intensity, ultrashort laser pulses the reflection results from two distinct nonlinear mechanisms. At lower densities, the reflection arises from the emission of an electromagnetic pulse during the saturation of the absolute Raman instability at the quarter critical surface. At higher densities the reflection of the pulse from the critical surface sets up a density fluctuation that acts as a Bragg-like reflector. These mechanisms, occurring in a non-perturbative regime of laser-plasma interactions, are examined numerically in order to characterize the Compton scattered radiation.

  16. Formation of AlN in laser ablated plasma of Al in nitrogen ambient

    NASA Astrophysics Data System (ADS)

    Thareja, Raj K.; Sharma, A. K.

    2005-05-01

    We report on spectroscopic investigations of interaction of an expanding laser ablated plume of aluminum and graphite with nitrogen gas and the formation of AlN and CN. AlN and CN bands are formed by reactive process of ablated aluminum and graphite in ambient nitrogen pressures of 70 and 0.1 Torr and laser fluence of 500 and 12 Jcm-2 respectively. Images of the expanding plasma plume were captured using ICCD to understand the role of vapor and shock temperature in the formation of AlN. Instability observed in laser ablated plume at later times attributed to Rayleigh-Taylor instability could be the cause for weak AlN band observed in the emission spectrum.

  17. 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.

  18. Pulse thermal processing of functional materials using directed plasma arc

    DOEpatents

    Ott, Ronald D.; Blue, Craig A.; Dudney, Nancy J.; Harper, David C.

    2007-05-22

    A method of thermally processing a material includes exposing the material to at least one pulse of infrared light emitted from a directed plasma arc to thermally process the material, the pulse having a duration of no more than 10 s.

  19. On the structure of quasi-stationary laser ablation fronts in strongly radiating plasmas

    SciTech Connect

    Basko, M. M. Novikov, V. G.; Grushin, A. S.

    2015-05-15

    The effect of strong thermal radiation on the structure of quasi-stationary laser ablation fronts is investigated under the assumption that all the laser flux is absorbed at the critical surface. Special attention is paid to adequate formulation of the boundary-value problem for a steady-state planar ablation flow. The dependence of the laser-to-x-ray conversion efficiency ϕ{sub r} on the laser intensity I{sub L} and wavelength λ{sub L} is analyzed within the non-equilibrium diffusion approximation for radiation transfer. The scaling of the main ablation parameters with I{sub L} and λ{sub L} in the strongly radiative regime 1−ϕ{sub r}≪1 is derived. It is demonstrated that strongly radiating ablation fronts develop a characteristic extended cushion of “radiation-soaked” plasma between the condensed ablated material and the critical surface, which can efficiently suppress perturbations from the instabilities at the critical surface.

  20. Multi-Pulse DARHT Machine-Plasma Plume Problem

    SciTech Connect

    Lauer, E J

    2004-07-01

    The plasma current decay time constant is predicted to be short compared to the pulse length and so self-focusing is predicted for most of the beam pulse. Four- pulse beam envelopes for a high dose case require mitigation, those for a low dose case do not. Methods of mitigation are summarized. Hose instability growth in the plume length is predicted to be minimal.

  1. Tailoring the plasma channel generated by femtosecond laser pulse

    NASA Astrophysics Data System (ADS)

    Wang, Haitao; Fan, Chengyu; Zhang, Pengfei; Jia, Wei

    2015-02-01

    By investigating the spatial and temporal variations of the propagating pulses, we have shown for the first time that the lattice waveguides can induce nonlinear effects to tailor the plasma channel generated by a femtosecond laser pulse. Different types of the spatiotemporal localized nonlinear light bullet’s propagating configurations have been predicted. By adjusting the parameters of the modulation potential, longer continuum filaments and reshaped laser pulses can be obtained, due to the focusing nonlinearity of the lattice modulation index.

  2. A Study of Burst-Mode Ultrafast-Pulse Laser Ablation on Soft Tissues and Tissue-Proxies

    NASA Astrophysics Data System (ADS)

    Qian, Zuoming

    This thesis research presents an experimental study of both the physics mechanisms and biological effects of burst-mode ultrafast-pulse laser ablation. A 3D living-cell-culture tissue-proxy based on agar hydrogel was developed, and this tissue-proxy was used to quantify the cellular necrosis range, to identify the types of cellular death, and to measure the volume of material removal post burst-mode laser ablation. The potential hazards of cellular DNA damage were also evaluated. A time-resolving energy-partition diagnostics system was designed and built for characterizing the dynamic scattering and absorption of pulses during burst-mode ablation. Such characterizations were carried out on soda-lime glass, aluminum, porcine tissues, distilled water, and agar gels using this diagnostic system. Each type of target materials displayed distinct features in their absorption patterns. An array of characteristics of the absorption and their relation to the ablation dynamics were analyzed, and valuable insight about the burst-mode ablation process was gained. The characterization of the dynamic absorptions allowed the evaluation of the roles of different physics mechanisms in the resulting cellular damage and material removal.

  3. Portable nanosecond pulsed air plasma jet

    SciTech Connect

    Walsh, J. L.; Kong, M. G.

    2011-08-22

    Low-temperature atmospheric pressure plasmas are of great importance in many emerging biomedical and materials processing applications. The redundancy of a vacuum system opens the gateway for highly portable plasma systems, for which air ideally becomes the plasma-forming gas and remote plasma processing is preferred to ensure electrical safety. Typically, the gas temperature observed in air plasma greatly exceeds that suitable for the processing of thermally liable materials; a large plasma-sample distance offers a potential solution but suffers from a diluted downstream plasma chemistry. This Letter reports a highly portable air plasma jet system which delivers enhanced downstream chemistry without compromising the low temperature nature of the discharge, thus forming the basis of a powerful tool for emerging mobile plasma applications.

  4. Field electron emission enhancement of graphenated MWCNTs emitters following their decoration with Au nanoparticles by a pulsed laser ablation process.

    PubMed

    Gautier, L-A; Le Borgne, V; Delegan, N; Pandiyan, R; El Khakani, M A

    2015-01-30

    A plasma-enhanced chemical vapor deposition (PECVD) process was adapted to alter the growth of multiwall carbon nanotubes (MWCNTs) so that graphene sheets grow out of their tips. Gold nanoparticle (Au-NP) decoration of graphenated MWCNTs (g-MWCNTs) was obtained by subsequent decoration by a pulsed laser deposition (PLD) process. By varying the number of laser ablation pulses (N(Lp)) in the PLD process, we were able to control the size of the gold nanoparticles and the surface coverage of the decorated g-MWCNTs. The presence of Au-NPs, preferentially located at the tip of the g-MWCNTs emitters, is shown to significantly improve the field electron emission (FEE) properties of the global g-MWCNT/Au-NP nanohybrid films. Indeed, the electric field needed to extract a current density of 0.1 μA cm(-)(2) from the g-MWCNT/Au-NP films was decreased from 2.68 V μm(-1) to a value as low as 0.96 V μm(-1). On the other hand, UV photoelectron spectroscopy (UPS) characterization revealed a decrease in the global work function of the Au-decorated g-MWCNT nanohybrids compared to that of bare g-MWCNT emitters. Surprisingly, the work function of g-MWCNT was found to decrease from 4.9 to 4.7 eV with the addition of Au-NPs-a value lower than the work function of both materials worth 5.2 and 4.9 eV for gold and g-MWCNT, respectively. Our results show that the N(Lp) dependence of the FEE characteristics of the g-MWCNT/Au-NP emitters correlates well with their work function changes. Fowler-Nordheim-theory-based calculations suggest that the significant FEE enhancement of the emitters is also caused by the Au-NPs acting as nanoscale electric field enhancers. PMID:25567743

  5. Field electron emission enhancement of graphenated MWCNTs emitters following their decoration with Au nanoparticles by a pulsed laser ablation process

    NASA Astrophysics Data System (ADS)

    Gautier, L.-A.; Le Borgne, V.; Delegan, N.; Pandiyan, R.; El Khakani, M. A.

    2015-01-01

    A plasma-enhanced chemical vapor deposition (PECVD) process was adapted to alter the growth of multiwall carbon nanotubes (MWCNTs) so that graphene sheets grow out of their tips. Gold nanoparticle (Au-NP) decoration of graphenated MWCNTs (g-MWCNTs) was obtained by subsequent decoration by a pulsed laser deposition (PLD) process. By varying the number of laser ablation pulses (NLp) in the PLD process, we were able to control the size of the gold nanoparticles and the surface coverage of the decorated g-MWCNTs. The presence of Au-NPs, preferentially located at the tip of the g-MWCNTs emitters, is shown to significantly improve the field electron emission (FEE) properties of the global g-MWCNT/Au-NP nanohybrid films. Indeed, the electric field needed to extract a current density of 0.1 μA cm-2 from the g-MWCNT/Au-NP films was decreased from 2.68 V μm-1 to a value as low as 0.96 V μm-1. On the other hand, UV photoelectron spectroscopy (UPS) characterization revealed a decrease in the global work function of the Au-decorated g-MWCNT nanohybrids compared to that of bare g-MWCNT emitters. Surprisingly, the work function of g-MWCNT was found to decrease from 4.9 to 4.7 eV with the addition of Au-NPs—a value lower than the work function of both materials worth 5.2 and 4.9 eV for gold and g-MWCNT, respectively. Our results show that the NLp dependence of the FEE characteristics of the g-MWCNT/Au-NP emitters correlates well with their work function changes. Fowler-Nordheim-theory-based calculations suggest that the significant FEE enhancement of the emitters is also caused by the Au-NPs acting as nanoscale electric field enhancers.

  6. Surfactant-free small Ni nanoparticles trapped on silica nanoparticles prepared by pulsed laser ablation in liquid

    NASA Astrophysics Data System (ADS)

    Mafuné, Fumitaka; Okamoto, Takumi; Ito, Miho

    2014-01-01

    Small Ni nanoparticles supported on silica nanoparticles were formed by pulsed laser ablation in liquid. Water dispersing surfactant-free silica particles was used here as a solvent, and a bulk Ni metal plate as a target. The nanoparticles formed by laser ablation in water were readily stabilized by the silica particles, whereas Ni nanoparticles prepared in water without silica were found to be precipitated a few hours after aggregation into 5-30 nm particles. The nanoparticles were characterized by TEM, dark-field STEM and optical absorption spectroscopy, which indicated that small 1-3 nm Ni nanoparticles were adsorbed on the surface of silica.

  7. Plasma formation and dynamics in conical wire arrays in the Llampudken pulsed power generator

    SciTech Connect

    Muñoz, C. Gonzalo E-mail: fveloso@fis.puc.cl; Valenzuela, Vicente E-mail: fveloso@fis.puc.cl; Veloso, Felipe E-mail: fveloso@fis.puc.cl; Favre, Mario E-mail: fveloso@fis.puc.cl; Wyndham, Edmund E-mail: fveloso@fis.puc.cl

    2014-12-15

    Plasma formation and dynamics from conical wire array is experimentally studied. Ablation from the wires is observed, forming plasma accumulation at the array axis and subsequently a jet outflow been expelled toward the top of the array. The arrays are composed by 16 equally spaced 25μ diameter tungsten wires. Their dimensions are 20mm height, with base diameters of 8mm and 16mm top diameter. The array loads are design to be overmassed, hence no complete ablation of the wires is observed during the current rise. The experiments have been carried out in the Llampudken. pulsed power generator (∼350kA in ∼350ns). Plasma dynamics is studied in both side-on and end-on directions. Laser probing (shadowgraphy) is achieved using a frequency doubled Nd:YAG laser (532nm, 12ps FWHM) captured by CCD cameras. Pinhole XUV imaging is captured using gated microchannel plate cameras with time resolution ∼5ns. Results on the jet velocity and the degree of collimation indicating the plausibility on the use of these jets as comparable to the study astrophysically produced jets are presented and discussed.

  8. Thrust efficiency optimization of the pulsed plasma thruster SIMP-LEX

    NASA Astrophysics Data System (ADS)

    Nawaz, Anuscheh; Albertoni, Riccardo; Auweter-Kurtz, Monika

    2010-08-01

    The effect of electric parameters on the thrust efficiency of an ablative pulsed plasma thruster was studied. Analytically, it was shown that a higher efficiency can be obtained by increasing energy of a bank of capacitors. This can be achieved by changing the inductance per distance of the plasma sheet, or reducing the resistance of the circuit and the mass bit. Further, an optimum discharge time was found when the capacitance and the inductance were varied. A low initial inductance increases the thrust efficiency. Experimentally, these trends can be verified by comparing two thrusters: SIMP-LEX and ADD SIMP-LEX, with their different initial inductances. For ADD SIMP-LEX, the optimal thrust efficiency for different capacities was determined to be 31% at 60μF for a 17 J configuration.

  9. SERS activity of silver and gold nanostructured thin films deposited by pulsed laser ablation

    NASA Astrophysics Data System (ADS)

    Agarwal, N. R.; Tommasini, M.; Fazio, E.; Neri, F.; Ponterio, R. C.; Trusso, S.; Ossi, P. M.

    2014-10-01

    Nanostructured Au and Ag thin films were obtained by nanosecond pulsed laser ablation in presence of a controlled Ar atmosphere. Keeping constant other deposition parameters such as target-to-substrate distance, incidence angle, laser wavelength and laser fluence, the film morphology, revealed by SEM, ranges from isolated NPs to island structures and sensibly depends on gas pressure (10-100 Pa) and on the laser pulse number (500-3 × 10). The control of these two parameters allows tailoring the morphology and correspondingly the optical properties of the films. The position and width of the surface plasmon resonance peak, in fact, can be varied with continuity. The films showed remarkable surface-enhanced Raman activity (SERS) that depends on the adopted deposition conditions. Raman maps were acquired on micrometer-sized areas of both silver and gold substrates selected among those with the strongest SERS activity. Organic dyes of interest in cultural heritage studies (alizarin, purpurin) have been also considered for bench marking the substrates produced in this work. Also the ability to detect the presence of biomolecules was tested using lysozyme in a label free configuration.

  10. Monodispersed Nanoparticle Synthesis Using Pulsed Laser Ablation and Application to Opto-electronic Devices

    NASA Astrophysics Data System (ADS)

    Yoshida, Takehito; Suzuki, Nobuyasu; Makino, Toshiharu; Yamada, Yuka

    We report silicon (Si) nanoparticles prepared by pulsed laser ablation in constant pressure inert background gas (PLA-IBG). We demonstrate the synthesis of monodispersed, nonagglomerated Si nanocrystallites, using a novel integrated process system where a classification unit of a low-pressure-operating differential mobility analyzer (LP-DMA) was combined to the PLA-IBG unit. The LP-DMA has been designed to operate under pressures less than 5.0 Torr. We have successfully synthesized and deposited the nonagglomerated Si nanocrystallites of 3.8 nm mean diameter and 1.2 geometrical standard deviation. On the other hand, properties of indium oxide (In2O3) thin films prepared by pulsed laser deposition (PLD) in background gases were characterized in relation to the background gas pressures. Transparent crystalline In2O3 thin films could be obtained at background gas pressures above 1.0 Torr on unheated glass substrates. To develop a near-infrared-light-emitting diode with active materials of monodispersed Si nanocrystallites and with passivation layer of the In2O3 thin films that are highly compatible with ULSI technology. The near-infrared emission was sharp and showed a peak above the band-gap region (position: 1.17 eV, width: 0.15 eV); therefore, it presumably originates from spatial quantum confinement effects of the carriers.

  11. Preparation of gold and silver nanoparticles by pulsed laser ablation of solid target in water

    NASA Astrophysics Data System (ADS)

    Nikov, R. G.; Nikolov, A. S.; Atanasov, P. A.

    2010-10-01

    Colloidal solutions of gold and silver nanoparticles (NPs) were prepared using a method pulsed laser ablation of target in liquid media. A gold and silver targets immersed in double distilled water are irradiated for 20 min by laser pulses with duration of 15 ns and repetition rate of 10 Hz. In order to investigate influences of laser wavelength and fluence on the particle size, shape and optical properties the experiments were preformed by using two different wavelength - the fundamental and the second harmonic (SH) (λ = 1064 and 532 nm, respectively) of a Nd:YAG laser system. Two different values of the laser fluence for each wavelength at the experimental conditions chosen were used and thus it was changed from several J/cm2 to tens of J/cm2. For characterization of the NPs shape and size distribution were used transmission electron microscope (TEM) and optical transmission spectroscopy in the near UV and in the visible region. Spherical shape of the nanoparticles at the low laser fluence and appearance of aggregation and building of nanowires at the SH and high laser fluence is seen. Dependence of the mean particle size at the SH on the laser fluence was established. The mean diameter of gold NPs became smaller with decrease in laser wavelength.

  12. Xenon plasma sustained by pulse-periodic laser radiation

    SciTech Connect

    Rudoy, I. G.; Solovyov, N. G.; Soroka, A. M.; Shilov, A. O.; Yakimov, M. Yu.

    2015-10-15

    The possibility of sustaining a quasi-stationary pulse-periodic optical discharge (POD) in xenon at a pressure of p = 10–20 bar in a focused 1.07-μm Yb{sup 3+} laser beam with a pulse repetition rate of f{sub rep} ⩾ 2 kHz, pulse duration of τ ⩾ 200 μs, and power of P = 200–300 W has been demonstrated. In the plasma development phase, the POD pulse brightness is generally several times higher than the stationary brightness of a continuous optical discharge at the same laser power, which indicates a higher plasma temperature in the POD regime. Upon termination of the laser pulse, plasma recombines and is then reinitiated in the next pulse. The initial absorption of laser radiation in successive POD pulses is provided by 5p{sup 5}6s excited states of xenon atoms. This kind of discharge can be applied in plasma-based high-brightness broadband light sources.

  13. Modulation instability of laser pulse in magnetized plasma

    SciTech Connect

    Jha, Pallavi; Kumar, Punit; Raj, Gaurav; Upadhyaya, Ajay K.

    2005-12-15

    Modulation instability of a laser pulse propagating through transversely magnetized underdense plasma is studied. It is observed that interaction of laser radiation with plasma in the presence of uniform magnetic field results in an additional perturbed transverse plasma current density along with the relativistic and ponderomotive nonlinear current densities, thus affecting the modulational interaction. In the plane wave limit it is observed that modulational interaction is more stable for magnetized plasma as compared to the unmagnetized case. The analysis shows that there is a significant reduction in the growth rate of modulation instability over a given range of unstable wave numbers due to magnetization of plasma.

  14. Interaction of nanosecond ultraviolet laser pulses with reactive dusty plasma

    NASA Astrophysics Data System (ADS)

    van de Wetering, F. M. J. H.; Oosterbeek, W.; Beckers, J.; Nijdam, S.; Gibert, T.; Mikikian, M.; Rabat, H.; Kovačević, E.; Berndt, J.

    2016-05-01

    Even though UV laser pulses that irradiate a gas discharge are small compared to the plasma volume (≲3%) and plasma-on time (≲6 × 10-6%), they are found to dramatically change the discharge characteristics on a global scale. The reactive argon-acetylene plasma allows the growth of nanoparticles with diameters up to 1 μm, which are formed inside the discharge volume due to spontaneous polymerization reactions. It is found that the laser pulses predominantly accelerate and enhance the coagulation phase and are able to suppress the formation of a dust void.

  15. Plasma and Cavitation Dynamics during Pulsed Laser Microsurgery in vivo

    SciTech Connect

    Hutson, M. Shane; Ma Xiaoyan

    2007-10-12

    We compare the plasma and cavitation dynamics underlying pulsed laser microsurgery in water and in fruit fly embryos (in vivo)--specifically for nanosecond pulses at 355 and 532 nm. We find two key differences. First, the plasma-formation thresholds are lower in vivo --especially at 355 nm--due to the presence of endogenous chromophores that serve as additional sources for plasma seed electrons. Second, the biological matrix constrains the growth of laser-induced cavitation bubbles. Both effects reduce the disrupted region in vivo when compared to extrapolations from measurements in water.

  16. 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.

  17. Plasma absorption evidence via chirped pulse spectral transmission measurements

    SciTech Connect

    Jedrkiewicz, Ottavia; Minardi, Stefano; Couairon, Arnaud; Jukna, Vytautas; Selva, Marco; Di Trapani, Paolo

    2015-06-08

    This work aims at highlighting the plasma generation dynamics and absorption when a Bessel beam propagates in glass. We developed a simple diagnostics allowing us to retrieve clear indications of the formation of the plasma in the material, thanks to transmission measurements in the angular and wavelength domains. This technique featured by the use of a single chirped pulse having the role of pump and probe simultaneously leads to results showing the plasma nonlinear absorption effect on the trailing part of the pulse, thanks to the spectral-temporal correspondence in the measured signal, which is also confirmed by numerical simulations.

  18. Fractal hydrodynamic model of high-fluence laser ablation plasma expansion

    SciTech Connect

    Agop, M.; Nica, P.; Gurlui, S.; Focsa, C.

    2010-10-08

    Optical/electrical characterization of transient plasmas generated by high-fluence (up to 1 kJ/cm{sup 2}) laser ablation of various targets revealed as a general feature the splitting of the plume in two structures. In order to account for this behavior, a new fractal hydrodynamic model has been developed in a non-differentiable space-time. The model successfully retrieves the kinetics of the two structures.

  19. Charge Exchange and Ablation Rates of a Titanium Wire Plasma Corona

    SciTech Connect

    Terry, Robert E.

    2009-01-21

    Wire ablation rates are important features in any examination of precursors or transparent mode implosions of wire arrays. When ion temperatures in a Ti wire plasma corona exceed a few eV, the process of resonant charge exchange competes with elastic scattering. Ions pushed into the corona from an anode bias wire array can be expected to drive a fast neutral wind into the surrounding volume, while a cathode bias wire array would not show the strong neutral wind.

  20. Thrust Stand Measurements of a Conical Inductive Pulsed Plasma Thruster

    NASA Technical Reports Server (NTRS)

    Hallock, Ashley K.; Polzin, Kurt A.

    2013-01-01

    Inductive Pulsed Plasma Thrusters (iPPT) spacecraft propulsion devices in which electrical energy is capacitively stored and then discharged through an inductive coil. The thruster is electrodeless, with a time-varying current in the coil interacting with a plasma covering the face of the coil to induce a plasma current Propellant is accelerated and expelled at a high exhaust velocity (O(10 -- 100 km/s)) by the Lorentz body force arising from the interaction of the magnetic field and the induced plasma current. While this class of thruster mitigates the life-limiting issues associated with electrode erosion, inductive pulsed plasma thrusters can suffer from both high pulse energy requirements imposed by the voltage demands of inductive propellant ionization, and low propellant utilization efficiencies. While this class of thruster mitigates the life-limiting issues associated with electrode erosion, inductive pulsed plasma thrusters can suffer from both high pulse energy requirements imposed by the voltage demands of inductive propellant ionization, and low propellant utilization efficiencies. A conical coil geometry may offer higher propellant utilization efficiency over that of a at inductive coil, however an increase in propellant utilization may be met with a decrease in axial electromagnetic acceleration, and in turn, a decrease in the total axially-directed kinetic energy imparted to the propellant.

  1. Plasma Switch for High-Power Active Pulse Compressor

    SciTech Connect

    Hirshfield, Jay L.

    2013-11-04

    Results are presented from experiments carried out at the Naval Research Laboratory X-band magnicon facility on a two-channel X-band active RF pulse compressor that employed plasma switches. Experimental evidence is shown to validate the basic goals of the project, which include: simultaneous firing of plasma switches in both channels of the RF circuit, operation of quasi-optical 3-dB hybrid directional coupler coherent superposition of RF compressed pulses from both channels, and operation of the X-band magnicon directly in the RF pulse compressor. For incident 1.2 ?s pulses in the range 0.63 ? 1.35 MW, compressed pulses of peak powers 5.7 ? 11.3 MW were obtained, corresponding to peak power gain ratios of 8.3 ? 9.3. Insufficient bakeout and conditioning of the high-power RF circuit prevented experiments from being conducted at higher RF input power levels.

  2. Endometrial ablation

    MedlinePlus

    Hysteroscopy-endometrial ablation; Laser thermal ablation; Endometrial ablation-radiofrequency; Endometrial ablation-thermal balloon ablation; Rollerball ablation; Hydrothermal ablation; Novasure ablation

  3. Long-pulse plasma discharge on the Large Helical Device

    NASA Astrophysics Data System (ADS)

    Kumazawa, R.; Mutoh, T.; Saito, K.; Seki, T.; Nakamura, Y.; Kubo, S.; Shimozuma, T.; Yoshimura, Y.; Igami, H.; Ohkubo, K.; Takeiri, Y.; Oka, Y.; Tsumori, K.; Osakabe, M.; Ikeda, K.; Nagaoka, K.; Kaneko, O.; Miyazawa, J.; Morita, S.; Narihara, K.; Shoji, M.; Masuzaki, S.; Kobayashi, M.; Ogawa, H.; Goto, M.; Morisaki, T.; Peterson, B. J.; Sato, K.; Tokuzawa, T.; Ashikawa, N.; Nishimura, K.; Funaba, H.; Chikaraishi, H.; Watari, T.; Watanabe, T.; Sakamoto, M.; Ichimura, M.; Takase, Y.; Notake, T.; Takeuchi, N.; Torii, Y.; Shimpo, F.; Nomura, G.; Takahashi, C.; Yokota, M.; Kato, A.; Zhao, Y.; Kwak, J. G.; Yoon, J. S.; Yamada, H.; Kawahata, K.; Ohyabu, N.; Ida, K.; Nagayama, Y.; Noda, N.; Komori, A.; Sudo, S.; Motojima, O.; LHD experiment Group

    2006-03-01

    A long-pulse plasma discharge of more than 30 min duration was achieved on the Large Helical Device (LHD). A plasma of ne = 0.8 × 1019 m-3 and Ti0 = 2.0 keV was sustained with PICH = 0.52 MW, PECH = 0.1 MW and averaged PNBI = 0.067 MW. The total injected heating energy was 1.3 GJ. One of the keys to the success of the experiment was a dispersion of the local plasma heat load to divertors, accomplished by sweeping the magnetic axis inward and outward. Causes limiting the long pulse plasma discharge are discussed. An ion impurity penetration limited further long-pulse discharge in the 8th experimental campaign (2004).

  4. Optical emission spectroscopy observations of fast pulsed capillary discharge plasmas

    NASA Astrophysics Data System (ADS)

    Avaria, G.; Ruiz, M.; Guzmán, F.; Favre, M.; Wyndham, E. S.; Chuaqui, H.; Bhuyan, H.

    2014-05-01

    We present time resolved optical emission spectroscopic (OES) observations of a low energy, pulsed capillary discharage (PCD). The optical emission from the capillary plasma and plasma jets emitted from the capillary volume was recorded with with a SpectraPro 275 spectrograph, fitted with a MCP gated OMA system, with 15 ns time resolution. The discharge was operated with different gases, including argon, nitrogen, hydrogen and methane, in a repetitive pulsed discharge mode at 10-50 Hz, with, 10-12 kV pulses applied at the cathode side. The time evolution of the electron density was measured using Stark broadening of the Hβ line. Several features of the capillary plasma dynamics, such as ionization growth, wall effects and plasma jet evolution, are inferred from the time evolution of the optical emission.

  5. Evolution of chirped laser pulses in a magnetized plasma channel

    SciTech Connect

    Jha, Pallavi; Hemlata,; Mishra, Rohit Kumar

    2014-12-15

    The propagation of intense, short, sinusoidal laser pulses in a magnetized plasma channel has been studied. The wave equation governing the evolution of the radiation field is set up and a variational technique is used to obtain the equations describing the evolution of the laser spot size, pulse length and chirp parameter. Numerical methods are used to analyze the simultaneous evolution of these parameters. The effect of the external magnetic field on initially chirped as well as unchirped laser pulses on the spot size, pulse length and chirping has been analyzed.

  6. Towards efficient generation of attosecond pulses from overdense plasma targets

    NASA Astrophysics Data System (ADS)

    Naumova, N. M.; Hauri, C. P.; Nees, J. A.; Sokolov, I. V.; Lopez-Martens, R.; Mourou, G. A.

    2008-02-01

    Theoretical studies and computer simulations predict efficient generation of attosecond electromagnetic pulses from overdense plasma targets, driven by relativistically strong laser pulses. These predictions need to be validated in time resolved experiments in order to provide a route for applications. The first available femtosecond sources for these experiments are likely to be 10 fs pulses of a few millijoules, which could provide focal intensities at about the relativistic threshold. With particle-in-cell simulations, we demonstrate that the radiation resulting from interaction of such pulses with solid targets is expected to be attosecond trains with very high conversion efficiency as relativistic effects start to act.

  7. Scattering of an ultrashort electromagnetic pulse in a plasma

    SciTech Connect

    Astapenko, V. A.

    2011-11-15

    An analytic approach is developed to describing how ultrashort electromagnetic pulses with a duration of one period or less at the carrier frequency are scattered in a plasma. Formulas are derived to calculate and analyze the angular and spectral probabilities of radiation scattering via two possible mechanisms-Compton and transition radiation channels-throughout the entire pulse. Numerical simulations were carried out for a Gaussian pulse. The effect of the phase of the carrier frequency relative to the pulse envelope on the scattering parameters is investigated.

  8. Topics in high voltage pulsed power plasma devices and applications

    NASA Astrophysics Data System (ADS)

    Chen, Hao

    Pulsed power technology is one of the tools that is used by scientists and engineers nowadays to produce gas plasmas. The transient ultra high power is able to provide a huge pulse of energy which is sometimes greater than the ionization energy of the gas, and therefore separates the ions and electrons to form the plasma. Sometimes, the pulsed power components themselves are plasma devices. For example, the gas type switches can "turn on" the circuit by creating the plasma channel between the switch electrodes. Mini Back Lighted Thyratron, or as we call it, mini-BLT, is one of these gas type plasma switches. The development of the reduced size and weight "mini-BLT" is presented in this dissertation. Based on the operation characteristics testing of the mini-BLT, suggestions of optimizing the design of the switch are proposed. All the factors such as the geometry of the hollow electrodes and switch housing, the gas condition, the optical triggering source, etc. are necessary to consider when we design and operate the mini-BLT. By reducing the diameter of the cylindrical gas path between the electrodes in the BLT, a novel high density plasma source is developed, producing the plasma in the "squeezed" capillary. The pulsed power generator, of course, is inevitably used to provide the ionization energy for hydrogen gas sealed in the capillary. Plasma diagnostics are necessarily analyzed and presented in detail to properly complete and understand the capillary plasma. This high density plasma source (1019 cm-3) has the potential applications in the plasma wakefield accelerator. The resonant oscillation behavior of the particles in plasmas allows for dynamically generated accelerating electric fields that have orders of magnitude larger than those available in the conventional RF accelerators. Finally, the solid state switches are introduced as a comparison to the gas type switch. Pulsed power circuit topologies such as the Marx Bank, magnetic pulse compression and diode

  9. 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.

  10. Comparison of High Rate Laser Ablation and Resulting Structures Using Continuous and Pulsed Single Mode Fiber Lasers

    NASA Astrophysics Data System (ADS)

    Knebel, T.; Streek, A.; Exner, H.

    This paper compares high rate laser ablation and resulting structures of aluminum by using both a continuous wave and a ns-pulsed single mode fiber laser of high average laser power. Two different scan technologies were applied for fast deflection of the laser beams. In this work, 2.5D laser processing was studied by using a high aperture galvanometer scanner with a maximum scan speed of 18 m/s. By contrast, considerably higher scan speeds up to 1,000 m/s were achieved by using the in-house developed polygon scanner system. The ablation rates and the processing rates per unit area were analyzed by means of the depths of line-scan ablation tracks and laser processed cavities. In addition, SEM photograph of the machining samples will be presented in order to evaluate the machining quality. Finally the feasibility of this high rate technology for industrial application is demonstrated by machining examples.

  11. ns or fs pulsed laser ablation of a bulk InSb target in liquids for nanoparticles synthesis.

    PubMed

    Semaltianos, N G; Hendry, E; Chang, H; Wears, M L; Monteil, G; Assoul, M; Malkhasyan, V; Blondeau-Patissier, V; Gauthier-Manuel, B; Moutarlier, V

    2016-05-01

    Laser ablation of bulk target materials in liquids has been established as an alternative method for the synthesis of nanoparticles colloidal solutions mainly due to the fact that the synthesized nanoparticles have bare, ligand-free surfaces since no chemical precursors are used for their synthesis. InSb is a narrow band gap semiconductor which has the highest carrier mobility of any known semiconductor and nanoparticles of this material are useful in optoelectronic device fabrication. In this paper a bulk InSb target was ablated in deionized (DI) water or ethanol using a nanosecond (20 ns) or a femtosecond (90 fs) pulsed laser source, for nanoparticles synthesis. In all four cases the largest percentage of the nanoparticles are of InSb in the zincblende crystal structure with fcc lattice. Oxides of either In or Sb are also formed in the nanoparticles ensembles in the case of ns or fs ablation, respectively. Formation of an oxide of either element from the two elements of the binary bulk alloy is explained based on the difference in the ablation mechanism of the material in the case of ns or fs pulsed laser irradiation in which the slow or fast deposition of energy into the material results to mainly melting or vaporization, respectively under the present conditions of ablation, in combination with the lower melting point but higher vaporization enthalpy of In as compared to Sb. InSb in the metastable phase with orthorhombic lattice is also formed in the nanoparticles ensembles in the case of fs ablation in DI water (as well as oxide of InSb) which indicates that the synthesized nanoparticles exhibit polymorphism controlled by the type of the laser source used for their synthesis. The nanoparticles exhibit absorption which is observed to be extended in the infrared region of the spectrum. PMID:26866890

  12. Direct coupling of pulsed radio frequency and pulsed high power in novel pulsed power system for plasma immersion ion implantation.

    PubMed

    Gong, Chunzhi; Tian, Xiubo; Yang, Shiqin; Fu, Ricky K Y; Chu, Paul K

    2008-04-01

    A novel power supply system that directly couples pulsed high voltage (HV) pulses and pulsed 13.56 MHz radio frequency (rf) has been developed for plasma processes. In this system, the sample holder is connected to both the rf generator and HV modulator. The coupling circuit in the hybrid system is composed of individual matching units, low pass filters, and voltage clamping units. This ensures the safe operation of the rf system even when the HV is on. The PSPICE software is utilized to optimize the design of circuits. The system can be operated in two modes. The pulsed rf discharge may serve as either the seed plasma source for glow discharge or high-density plasma source for plasma immersion ion implantation (PIII). The pulsed high-voltage glow discharge is induced when a rf pulse with a short duration or a larger time interval between the rf and HV pulses is used. Conventional PIII can also be achieved. Experiments conducted on the new system confirm steady and safe operation. PMID:18447526

  13. Shock Wave Mediated Plume Chemistry for Molecular Formation in Laser Ablation Plasmas.

    PubMed

    Harilal, Sivanandan S; Brumfield, Brian E; Cannon, Bret D; Phillips, Mark C

    2016-02-16

    Although it is relatively straightforward to measure the ionic, atomic, molecular, and particle emission features from laser ablation plumes, the associated kinetic and thermodynamic development leading to molecular and nanocluster formation remain one of the most important topics of analytical chemistry and material science. Very little is known, for instance, about the evolutionary paths of molecular and nanocluster formation and its relation to laser plume hydrodynamics. This is, to a large extent; due to the complexity of numerous physical processes that coexist in a transient laser-plasma system. Here, we report the formation mechanisms of molecules during complex interactions of a laser-produced plasma plume expanding from a high purity aluminum metal target into ambient air. It is found that the plume hydrodynamics plays a great role in redefining the plasma thermodynamics and molecular formation. Early in the plasma expansion, the generated shock wave at the plume edge acts as a barrier for the combustion process and molecular formation is prevalent after the shock wave collapse. The temporally and spatially resolved contour mapping of atoms and molecules in laser ablation plumes highlight the formation routes and persistence of species in the plasma and their relation to plume hydrodynamics. PMID:26732866

  14. Pulsed and CW adjustable 1942 nm single-mode all-fiber Tm-doped fiber laser system for surgical laser soft tissue ablation applications.

    PubMed

    Huang, Yize; Jivraj, Jamil; Zhou, Jiaqi; Ramjist, Joel; Wong, Ronnie; Gu, Xijia; Yang, Victor X D

    2016-07-25

    A surgical laser soft tissue ablation system based on an adjustable 1942 nm single-mode all-fiber Tm-doped fiber laser operating in pulsed or CW mode with nitrogen assistance is demonstrated. Ex vivo ablation on soft tissue targets such as muscle (chicken breast) and spinal cord (porcine) with intact dura are performed at different ablation conditions to examine the relationship between the system parameters and ablation outcomes. The maximum laser average power is 14.4 W, and its maximum peak power is 133.1 W with 21.3 μJ pulse energy. The maximum CW power density is 2.33 × 106 W/cm2 and the maximum pulsed peak power density is 2.16 × 107 W/cm2. The system parameters examined include the average laser power in CW or pulsed operation mode, gain-switching frequency, total ablation exposure time, and the input gas flow rate. The ablation effects were measured by microscopy and optical coherence tomography (OCT) to evaluate the ablation depth, superficial heat-affected zone diameter (HAZD) and charring diameter (CD). Our results conclude that the system parameters can be tailored to meet different clinical requirements such as ablation for soft tissue cutting or thermal coagulation for future applications of hemostasis. PMID:27464121

  15. A Performance Comparison of Pulsed Plasma Thruster Electrode Configurations

    NASA Technical Reports Server (NTRS)

    Arrington, Lynn A.; Haag, Tom W.; Pencil, Eric J.; Meckel, Nicole J.

    1997-01-01

    Pulsed plasma thrusters are currently planned on two small satellite missions and proposed for a third. In these missions, the pulsed plasma thruster's unique characteristics will be used variously to provide propulsive attitude control, orbit raising, translation, and precision positioning. Pulsed plasma thrusters are attractive for small satellite applications because they are essentially stand alone devices which eliminate the need for toxic and/or distributed propellant systems. Pulsed plasma thrusters also operate at low power and over a wide power range without loss of performance. As part of the technical development required for the noted missions, an experimental program to optimize performance with respect to electrode configuration was undertaken. One of the planned missions will use pulsed plasma thrusters for orbit raising requiring relatively high thrust and previously tested configurations did not provide this. Also, higher capacitor energies were tested than previously tried for this mission. Multiple configurations were tested and a final configuration was selected for flight hardware development. This paper describes the results of the electrode optimization in detail.

  16. Plasma detector for TEA CO2 laser pulse measurement

    NASA Astrophysics Data System (ADS)

    Ichikawa, Y.; Yamanaka, M.; Mitsuishi, A.; Fujita, S.; Yamanaka, T.; Yamanaka, C.; Tsunawaki, Y.; Iwasaki, T.; Takai, M.

    1983-10-01

    Laser-pulse evolution can be detected by measuring the emf generated by fast electrons in a laser-produced plasma when the laser radiation is focused onto a solid metal target in a vacuum. Using this phenomenon a 'plasma detector' is constructed, and its characteristics for the TEA CO2 laser radiation of intensity 10 to the 9th to 10 to the 10th W/sq cm are investigated experimentally. The plasma detector operates at room temperature and is strong against laser damages. For the evacuated plasma detector down to 0.1 torr, a maximum output voltage of 90 V and a rise time shorter than 1 ns are observed. The plasma detector, therefore, can be used as a power monitor for laser pulses and as a trigger voltage source.

  17. Comparison of the ablation behavior of polymer films in the IR and UV with nanosecond and picosecond pulses

    SciTech Connect

    Hahn, C.; Lippert, T.; Wokaun, A.

    1999-02-25

    Experiments are performed to compare the ablation behavior in the IR and UV spectral regions of a doped standard polymer, PMMA, and a specially tailored photopolymer, i.e., a triazene copolyester, to elucidate the underlying mechanisms. The results are discussed in light of current theories about photochemical and photothermal pathways of ablation. Further experiments are performed with nanosecond and picosecond pulses to study the impact of pulse length on the material. From the failure to induce ablation in the IR by doping the specialty polymer with an optical molecular heater the authors conclude that etching in the UV of this compound is mainly governed by a photochemical process. This result is contrasted by successful ablation of doped PMMA in the IR via a thermal unzipping mechanism. With respect to practical applications, the results show convincingly that the presence of an absorbing chromophore in the polymer is a prerequisite for achieving high-resolution structuring, since molecular absorption is required for an efficient distribution of incorporated photonic energy.

  18. A study of angular dependence in the ablation rate of polymers by nanosecond pulses

    NASA Astrophysics Data System (ADS)

    Pedder, James E. A.; Holmes, Andrew S.

    2006-02-01

    Measurements of ablation rate have traditionally been carried out only at normal incidence. However, in real-world applications ablation is often carried out at oblique angles, and it is useful to have prior knowledge of the ablation rate in this case. Detailed information about the angular dependence is also important for the development of ablation simulation tools, and can provide additional insight into the ablation mechanism. Previously we have reported on the angular dependence of direct-write ablation at 266 nm wavelength in solgel and polymer materials. In this paper we present a systematic study of angular dependence for excimer laser ablation of two polymer materials of interest for microfabrication: polycarbonate and SU8 photoresist. The results are used to improve simulation models to aid in mask design.

  19. Investigation of effect of solenoid magnet on emittances of ion beam from laser ablation plasma.

    PubMed

    Ikeda, Shunsuke; Romanelli, Mark; Cinquegrani, David; Sekine, Megumi; Kumaki, Masafumi; Fuwa, Yasuhiro; Kanesue, Takeshi; Okamura, Masahiro; Horioka, Kazuhiko

    2014-02-01

    A magnetic field can increase an ion current of a laser ablation plasma and is expected to control the change of the plasma ion current. However, the magnetic field can also make some fluctuations of the plasma and the effect on the beam emittance and the emission surface is not clear. To investigate the effect of a magnetic field, we extracted the ion beams under three conditions where without magnetic field, with magnetic field, and without magnetic field with higher laser energy to measure the beam distribution in phase space. Then we compared the relations between the plasma ion current density into the extraction gap and the Twiss parameters with each condition. We observed the effect of the magnetic field on the emission surface. PMID:24593624

  20. Investigation of effect of solenoid magnet on emittances of ion beam from laser ablation plasma

    NASA Astrophysics Data System (ADS)

    Ikeda, Shunsuke; Romanelli, Mark; Cinquegrani, David; Sekine, Megumi; Kumaki, Masafumi; Fuwa, Yasuhiro; Kanesue, Takeshi; Okamura, Masahiro; Horioka, Kazuhiko

    2014-02-01

    A magnetic field can increase an ion current of a laser ablation plasma and is expected to control the change of the plasma ion current. However, the magnetic field can also make some fluctuations of the plasma and the effect on the beam emittance and the emission surface is not clear. To investigate the effect of a magnetic field, we extracted the ion beams under three conditions where without magnetic field, with magnetic field, and without magnetic field with higher laser energy to measure the beam distribution in phase space. Then we compared the relations between the plasma ion current density into the extraction gap and the Twiss parameters with each condition. We observed the effect of the magnetic field on the emission surface.

  1. Development of A Pulse Radio-Frequency Plasma Jet

    NASA Astrophysics Data System (ADS)

    Wang, Shou-Guo; Zhao, Ling-Li; Yang, Jing-Hua

    2013-09-01

    A small pulse plasma jet was driven by new developed radio-frequency (RF) power supply of 6.78 MHz. In contrast to the conventional RF 13.56 MHz atmospheric pressure plasma jet (APPJ), the power supply was highly simplified by eliminating the matching unit of the RF power supply and using a new circuit, moreover, a pulse controller was added to the circuit to produce the pulse discharge. The plasma jet was operated in a capacitively coupled manner and exhibited low power requirement of 5 W at atmospheric pressure using argon as a carrier gas. The pulse plasma plume temperature remained at less than 45 °C for an extended period of operation without using water to cool the electrodes. Optical emission spectrum measured at a wide range of 200-1000 nm indicated various excited species which were helpful in applying the plasma jet for surface sterilization to human skin or other sensitive materials. Institude of Plasma Physics, Chinese Academy of Science, Hefei, China.

  2. INPIStron switched pulsed power for dense plasma pinches

    NASA Technical Reports Server (NTRS)

    Han, Kwang S.; Lee, Ja H.

    1993-01-01

    The inverse plasma switch INPIStron was employed for 10kJ/40kV capacitor bank discharge system to produce focused dense plasmas in hypocycloidal-pinch (HCP) devices. A single unit and an array of multiple HCP's were coupled as the load of the pulsed power circuit. The geometry and switching plasma dynamics were found advantageous and convenient for commutating the large current pulse from the low impedance transmission line to the low impedance plasma load. The pulse power system with a single unit HCP, the system A, was used for production of high temperature plasma focus and its diagnostics. The radially running down plasma dynamics, revealed in image converter photographs, could be simulated by a simple snow-plow model with a correction for plasma resistivity. The system B with an array of 8-HCP units which forms a long coaxial discharge chamber was used for pumping a Ti-sapphire laser. The intense UV emission from the plasma was frequency shifted with dye-solution jacket to match the absorption band of the Ti crystal laser near 500 nm. An untuned laser pulse energy of 0.6 J/pulse was obtained for 6.4 kJ/40 kV discharge, or near 103 times of the explosion limit of conventional flash lamps. For both systems the advantages of the INPIStron were well demonstrated: a single unit is sufficient for a large current (greater than 50 kA) without increasing the system impedance, highly reliable and long life operation and implied scalability for the high power ranges above I(sub peak) = 1 MA and V(sub hold) = 100 kV.

  3. Tailoring the air plasma with a double laser pulse

    SciTech Connect

    Shneider, M. N.; Miles, R. B.; Zheltikov, A. M.

    2011-06-15

    We present a comprehensive model of plasma dynamics that enables a detailed understanding of the ways the air plasma induced in the atmosphere in the wake of a laser-induced filament can be controlled by an additional laser pulse. Our model self-consistently integrates plasma-kinetic, Navier-Stokes, electron heat conduction, and electron-vibration energy transfer equations, serving to reveal laser-plasma interaction regimes where the plasma lifetime can be substantially increased through an efficient control over plasma temperature, as well as suppression of attachment and recombination processes. The model is used to quantify the limitations on the length of uniform laser-filament heating due to the self-defocusing of laser radiation by the radial profile of electron density. The envisaged applications include sustaining plasma guides for long-distance transmission of microwaves, standoff detection of impurities and potentially hazardous agents, as well as lightning control and protection.

  4. Tailoring the air plasma with a double laser pulse

    NASA Astrophysics Data System (ADS)

    Shneider, M. N.; Zheltikov, A. M.; Miles, R. B.

    2011-06-01

    We present a comprehensive model of plasma dynamics that enables a detailed understanding of the ways the air plasma induced in the atmosphere in the wake of a laser-induced filament can be controlled by an additional laser pulse. Our model self-consistently integrates plasma-kinetic, Navier-Stokes, electron heat conduction, and electron-vibration energy transfer equations, serving to reveal laser-plasma interaction regimes where the plasma lifetime can be substantially increased through an efficient control over plasma temperature, as well as suppression of attachment and recombination processes. The model is used to quantify the limitations on the length of uniform laser-filament heating due to the self-defocusing of laser radiation by the radial profile of electron density. The envisaged applications include sustaining plasma guides for long-distance transmission of microwaves, standoff detection of impurities and potentially hazardous agents, as well as lightning control and protection.

  5. Effect of background gas pressure and laser pulse intensity on laser induced plasma radiation of copper samples

    NASA Astrophysics Data System (ADS)

    Mehrabian, S.; Aghaei, M.; Tavassoli, S. H.

    2010-04-01

    Study of laser induced plasma emission of Cu in one dimension is numerically carried out. Effects of different background gas pressure (He), 100, 500, and 760 torr, and laser pulse intensities, 0.5, 0.7, and 1 GW/cm2, on the plasma emission as well as ablation processes are investigated. Under a specified condition, heat conduction equation in the target accompanied with gas dynamic equations in the plume is solved simultaneously. The mentioned equations are coupled to each other through the Knudsen layer conditions and the energy and mass balances at the interface between the target and the vapor. The Bremsstrahlung radiation of plasma and the spectral emission of copper atoms are studied under various background gas pressure and laser pulse intensities. Furthermore, number density of He, Cu, and the electron, pressure, and temperature of the plume under various conditions are obtained. In the early time after laser pulse, plasma radiation is mainly due to the Bremsstrahlung radiation while after some 10 ns, the plasma radiation is dominated by spectral emission of Cu atoms. A similar uncoupling is observed spatially. The Bremsstrahlung emission is dominant near the sample surface while at farther points the spectral emission is the dominant one. By increase in the background pressure and also the pulse intensity, the dominancy of the spectral emission would occur later in time and farther in position.

  6. Controlling Plasma Channels through Ultrashort Laser Pulse Filamentation

    NASA Astrophysics Data System (ADS)

    Ionin, Andrey; Seleznev, Leonid; Sunchugasheva, Elena

    2013-09-01

    A review of studies fulfilled at the Lebedev Institute in collaboration with the Moscow State University and Institute of Atmospheric Optics in Tomsk on influence of various characteristics of ultrashort laser pulse on plasma channels formed under its filamentation is presented. Filamentation of high-power laser pulses with wavefront controlled by a deformable mirror, with cross-sections spatially formed by various diaphragms and with different wavelengths was experimentally and numerically studied. An application of plasma channels formed due to filamentation of ultrashort laser pulse including a train of such pulses for triggering and guiding long electric discharges is discussed. The research was supported by RFBR Grants 11-02-12061-ofi-m and 11-02-01100, and EOARD Grant 097007 through ISTC Project 4073 P

  7. Dynamics of dark hollow Gaussian laser pulses in relativistic plasma.

    PubMed

    Sharma, A; Misra, S; Mishra, S K; Kourakis, I

    2013-06-01

    Optical beams with null central intensity have potential applications in the field of atom optics. The spatial and temporal evolution of a central shadow dark hollow Gaussian (DHG) relativistic laser pulse propagating in a plasma is studied in this article for first principles. A nonlinear Schrodinger-type equation is obtained for the beam spot profile and then solved numerically to investigate the pulse propagation characteristics. As series of numerical simulations are employed to trace the profile of the focused and compressed DHG laser pulse as it propagates through the plasma. The theoretical and simulation results predict that higher-order DHG pulses show smaller divergence as they propagate and, thus, lead to enhanced energy transport. PMID:23848793

  8. Submicrometer Imaging by Laser Ablation-Inductively Coupled Plasma Mass Spectrometry via Signal and Image Deconvolution Approaches.

    PubMed

    Van Malderen, Stijn J M; van Elteren, Johannes T; Vanhaecke, Frank

    2015-06-16

    In this work, pre- and postacquisition procedures for enhancing the lateral resolution of laser ablation-inductively coupled plasma mass spectrometry (LA-ICPMS) in two- and three-dimensional (2D, 3D) nuclide distribution mapping beyond the laser beam waist are described. 2D images were constructed by projecting a rectangular grid of discrete LA positions, arranged at interspacings smaller than the dimensions of the laser beam waist, onto the sample surface, thus oversampling the region of interest and producing a 2D image convolved in the spatial domain. The pulse response peaks of a low-dispersion LA cell were isolated via signal deconvolution of the transient mass analyzer response. A 3D stack of 2D images was deconvolved by an iterative Richardson-Lucy algorithm with Total Variance regularization, enabling submicrometer image fidelity, demonstrated in the analysis of trace level features in corroded glass. A point spread function (PSF) could be derived from topography maps of single pulse craters from atomic force microscopy. This experimental PSF allows the approach to take into account the laser beam shape, beam aberrations, and the laser-solid interaction, which in turn enhances the spatial resolution of the reconstructed volume. PMID:25975805

  9. Resonant ablation of single-wall carbon nanotubes by femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Arutyunyan, N. R.; Komlenok, M. S.; Kononenko, V. V.; Pashinin, V. P.; Pozharov, A. S.; Konov, V. I.; Obraztsova, E. D.

    2015-01-01

    The thin 50 nm film of bundled arc-discharge single-wall carbon nanotubes was irradiated by femtosecond laser pulses with wavelengths 675, 1350 and 1745 nm corresponding to the absorption band of metallic nanotubes E11M, to the background absorption and to the absorption band of semiconducting nanotubes E11S, respectively. The aim was to induce a selective removal of nanotubes of specific type from the bundled material. Similar to conducted thermal heating experiments, the effect of laser irradiation results in suppression of all radial breathing modes in the Raman spectra, with preferential destruction of the metallic nanotubes with diameters less than 1.26 nm and of the semiconducting nanotubes with diameters 1.36 nm. However, the etching rate of different nanotubes depends on the wavelength of the laser irradiation. It is demonstrated that the relative content of nanotubes of different chiralities can be tuned by a resonant laser ablation of undesired nanotube fraction. The preferential etching of the resonant nanotubes has been shown for laser wavelengths 675 nm (E11M) and 1745 nm (E11S).

  10. Characterization of titania thin films prepared by reactive pulsed-laser ablation

    NASA Astrophysics Data System (ADS)

    Luca, D.; Macovei, D.; Teodorescu, C.-M.

    2006-09-01

    Results are reported on the characterization of 200-250 nm thick TiO x transparent films grown at temperatures of 150 °C and 500 °C by reactive pulsed-laser ablation of a metallic Ti target under 0.13-13.3 Pa oxygen atmosphere. Film structure and composition were investigated by X-ray diffraction and X-ray photoelectron spectroscopy. The samples deposited at 150 °C reveal a mixture of amorphous TiO 2 and Ti 2O 3, irrespective of oxygen pressure. The O:Ti atomic ratio fluctuates in their surface around 1.83 for oxygen pressure ranging between 0.13 Pa and 2.66 Pa. The samples deposited at 500 °C feature different characteristics, as a function of oxygen pressure: (a) below 2.66 Pa of O 2 the films contain a mixture of significant amount of anatase and rutile TiO 2 phases, along with titanium suboxides; (b) above this threshold, the rutile phase vanishes, the anatase TiO 2 phase remaining dominant along with small amounts of nanocrystalline suboxides. The size of the anatase nanocrystallites decreases with the increase of oxygen pressures. The samples deposited at 500 °C feature a slight improvement of surface stoichiometry, from roughly TiO 1.8 to TiO 1.9. The films deposited at high substrate temperature and oxygen pressure are highly hydrophilic.

  11. Effects of natural oxidation on the photoluminescence properties of Si nanocrystals prepared by pulsed laser ablation

    NASA Astrophysics Data System (ADS)

    Xu, Yanmei; Han, Yinghui

    2014-07-01

    In this work, Si nanocrystals (Si-NCs) have been prepared by pulsed laser ablation technique in dichloromethane, and the microstructure and photoluminescence (PL) properties of the Si-NCs before and after natural oxidation were investigated. Transmission electron microscopy and Raman results show that the average diameter of the Si-NCs is 2.42 nm in the dichloromethane solution. Blue-violet PL with a lifetime of 4.6 ns is observed at room temperature, and the PL peak shifts toward longer wavelength with the red shift of excitation wavelength. The PL excitation spectrum indicates that the bandgap of the Si-NCs in solution is 2.64 eV, which confirms that the blue-violet PL originates from interband transition of Si-NCs caused by quantum confinement effect. The PL peak red shifts to 607 nm after natural oxidation, and the peak lifetime of which is slow down to 13.1 μs. The fixed PL peak excited by different wavelengths and the slow PL decay time indicate that interface defects become the main PL mechanism after natural oxidation. The results will add new information for understanding the PL mechanism of Si-NCs in different environments.

  12. Room temperature ferromagnetism in liquid-phase pulsed laser ablation synthesized nanoparticles of nonmagnetic oxides

    NASA Astrophysics Data System (ADS)

    Singh, S. C.; Kotnala, R. K.; Gopal, R.

    2015-08-01

    Intrinsic Room Temperature Ferromagnetism (RTF) has been observed in undoped/uncapped zinc oxide and titanium dioxide spherical nanoparticles (NPs) obtained by a purely green approach of liquid phase pulsed laser ablation of corresponding metal targets in pure water. Saturation magnetization values observed for zinc oxide (average size, 9 ± 1.2 nm) and titanium dioxide (average size, 4.4 ± 0.3 nm) NPs are 62.37 and 42.17 memu/g, respectively, which are several orders of magnitude larger than those of previous reports. In contrast to the previous works, no postprocessing treatments or surface modification is required to induce ferromagnetism in the case of present communication. The most important result, related to the field of intrinsic ferromagnetism in nonmagnetic materials, is the observation of size dependent ferromagnetism. Degree of ferromagnetism in titanium dioxide increases with the increase in particle size, while it is reverse for zinc oxide. Surface and volume defects play significant roles for the origin of RTF in zinc oxide and titanium dioxide NPs, respectively. Single ionized oxygen and neutral zinc vacancies in zinc oxide and oxygen and neutral/ionized titanium vacancies in titanium dioxide are considered as predominant defect centres responsible for observed ferromagnetism. It is expected that origin of ferromagnetism is a consequence of exchange interactions between localized electron spin moments resulting from point defects.

  13. Pulsed radiofrequency ablation for residual and phantom limb pain: a case series.

    PubMed

    West, Matt; Wu, Hong

    2010-01-01

    Residual limb pain (RLP) and phantom limb pain (PLP) can be debilitating and can prevent functional gains following amputation. High correlations have been reported between RLP and the stump neuromas following amputation. Many treatment methods including physical therapy, medications, and interventions, have been used with limited success. Pulsed radiofrequency ablation (PRFA) has shown promise in treating neuropathic pain because of the inhibition of evoked synaptic activity. We present 4 amputees who were treated with PRFA after failing conservative management for their RLP and PLP. All 4 patients underwent PRFA and demonstrated at least 80% relief of RLP for over 6 months. One patient reported a complete resolution of phantom sensation while another patient had significantly decreased frequency of spontaneous PLP and resolution of evoked PLP. In addition, all patients reported improved overall function including increased prosthetic tolerance and decreased oral pain medications. This case series suggests that PRFA is a viable treatment option which might be used for long-term relief of intractable RLP and/or PLP. PMID:20230449

  14. Generation of diluted magnetic semiconductor nanostructures by pulsed laser ablation in liquid

    NASA Astrophysics Data System (ADS)

    Savchuk, Ol. A.; Savchuk, A. I.; Stolyarchuk, I. D.; Tkachuk, P. M.; Garasym, V. I.

    2015-11-01

    Results of study of two members of diluted magnetic semiconductor (DMS) family, namely Cd1-xMnxTe and Zn1-xMnxO, which are in form of micro- and nanoparticles generated by pulsed laser ablation in liquid medium (PLAL), have been presented. The structural analysis using X-ray diffraction (XRD) of nanocrystals indicated that Mn has entered the AIIBVI lattice without changing the crystal structure and systematically substituted the A2+ ions in the lattice. Atomic force microscopy (AFM) gives information about surface morphology of the formed nanostructures. The scanning electron microscopy (SEM) clearly illustrates flower-like particles of Zn1-xMnxO, which consist of nanosheets and nanoleaves with average thickness about (5-8) nm. Obviously, these nanoobjects are responsible for the observed blue shift of the absorption edge in DMS nanostructures. In magneto-optical Faraday rotation spectra of both Cd1-xMnxTe and Zn1-xMnxO nanostructures there were exhibited peculiarities associated with s,p-d spin exchange interactions and confinement effect. It was observed almost linear dependence of the Faraday rotation as function of magnetic field strength for nanoparticles in contrast to the dependence with saturation in bulk case.

  15. Room temperature ferromagnetism in liquid-phase pulsed laser ablation synthesized nanoparticles of nonmagnetic oxides

    SciTech Connect

    Singh, S. C. Gopal, R.; Kotnala, R. K.

    2015-08-14

    Intrinsic Room Temperature Ferromagnetism (RTF) has been observed in undoped/uncapped zinc oxide and titanium dioxide spherical nanoparticles (NPs) obtained by a purely green approach of liquid phase pulsed laser ablation of corresponding metal targets in pure water. Saturation magnetization values observed for zinc oxide (average size, 9 ± 1.2 nm) and titanium dioxide (average size, 4.4 ± 0.3 nm) NPs are 62.37 and 42.17 memu/g, respectively, which are several orders of magnitude larger than those of previous reports. In contrast to the previous works, no postprocessing treatments or surface modification is required to induce ferromagnetism in the case of present communication. The most important result, related to the field of intrinsic ferromagnetism in nonmagnetic materials, is the observation of size dependent ferromagnetism. Degree of ferromagnetism in titanium dioxide increases with the increase in particle size, while it is reverse for zinc oxide. Surface and volume defects play significant roles for the origin of RTF in zinc oxide and titanium dioxide NPs, respectively. Single ionized oxygen and neutral zinc vacancies in zinc oxide and oxygen and neutral/ionized titanium vacancies in titanium dioxide are considered as predominant defect centres responsible for observed ferromagnetism. It is expected that origin of ferromagnetism is a consequence of exchange interactions between localized electron spin moments resulting from point defects.

  16. Production of microstructures in wide-band-gap and organic materials using pulsed laser ablation at 157 nm wavelength

    NASA Astrophysics Data System (ADS)

    Haehnel, Falk; Bertram, Rene; Reisse, Guenter; Boettcher, Rene; Weissmantel, Steffen

    2010-11-01

    New results on three-dimensional microstructuring of fused silica, sapphire, calcium fluoride, magnesium fluoride, and PTFE using pulsed laser ablation at 157 nm wavelength are presented. A largely automated high-precision fluorine laser micromachining station was used for the investigations. In some fundamental investigations, threshold fluences of 0.9 J/cm2 for fused silica, 0.6 J/cm2 for sapphire, 1.7 J/cm2 for calcium fluoride, and of 0.05 J/cm2 for PTFE have been determined. The ablation rates at 3 J/cm2 fluence were 60 to 100 nm/pulse for the inorganic insulators and 450 nm/pulse for PTFE. In the second part of the paper, it is shown that on the basis of the knowledge of the ablation rates and the laser beam parameters, bores of a few µm size and complex 3D microstructures with a variety of geometries can be produced in the surface of these materials. Thereby, no cracking occurs if proper parameters are used.

  17. Guiding of intense laser pulse in uniform plasmas and preformed plasma channels

    SciTech Connect

    Wang Jingwei; Lei, A. L.; Wang Xin; Yu Wei; Yu, M. Y.; Senecha, V. K.; Wang, X. G.; Murakami, M.; Mima, K.

    2010-10-15

    Guiding of laser pulse in uniform plasmas and preformed plasma channels is investigated. The self-guiding mechanisms for these two cases are quite different. It is found that an intense laser pulse can be steadily self-guided in underdense plasmas with nearly a constant spot size if the self-consistently generated electron cavity has a sufficiently steep density gradient at the edge. In a preformed plasma channel, however, laser guiding is maintained mainly by the balance between the light diffraction and focusing. The latter is induced by the wall plasmas which greatly reduce the local dielectric constant. It is shown that the self-guiding of a laser pulse in uniform plasmas requires tens of terawatts power, but those that are in preformed channels can be realized with only a terawatt power.

  18. Chirped pulse Raman amplification in warm plasma: towards controlling saturation

    NASA Astrophysics Data System (ADS)

    Yang, X.; Vieux, G.; Brunetti, E.; Ersfeld, B.; Farmer, J. P.; Hur, M. S.; Issac, R. C.; Raj, G.; Wiggins, S. M.; Welsh, G. H.; Yoffe, S. R.; Jaroszynski, D. A.

    2015-08-01

    Stimulated Raman backscattering in plasma is potentially an efficient method of amplifying laser pulses to reach exawatt powers because plasma is fully broken down and withstands extremely high electric fields. Plasma also has unique nonlinear optical properties that allow simultaneous compression of optical pulses to ultra-short durations. However, current measured efficiencies are limited to several percent. Here we investigate Raman amplification of short duration seed pulses with different chirp rates using a chirped pump pulse in a preformed plasma waveguide. We identify electron trapping and wavebreaking as the main saturation mechanisms, which lead to spectral broadening and gain saturation when the seed reaches several millijoules for durations of 10’s - 100’s fs for 250 ps, 800 nm chirped pump pulses. We show that this prevents access to the nonlinear regime and limits the efficiency, and interpret the experimental results using slowly-varying-amplitude, current-averaged particle-in-cell simulations. We also propose methods for achieving higher efficiencies.

  19. Chirped pulse Raman amplification in warm plasma: towards controlling saturation

    PubMed Central

    Yang, X.; Vieux, G.; Brunetti, E.; Ersfeld, B.; Farmer, J. P.; Hur, M. S.; Issac, R. C.; Raj, G.; Wiggins, S. M.; Welsh, G. H.; Yoffe, S. R.; Jaroszynski, D. A.

    2015-01-01

    Stimulated Raman backscattering in plasma is potentially an efficient method of amplifying laser pulses to reach exawatt powers because plasma is fully broken down and withstands extremely high electric fields. Plasma also has unique nonlinear optical properties that allow simultaneous compression of optical pulses to ultra-short durations. However, current measured efficiencies are limited to several percent. Here we investigate Raman amplification of short duration seed pulses with different chirp rates using a chirped pump pulse in a preformed plasma waveguide. We identify electron trapping and wavebreaking as the main saturation mechanisms, which lead to spectral broadening and gain saturation when the seed reaches several millijoules for durations of 10’s – 100’s fs for 250 ps, 800 nm chirped pump pulses. We show that this prevents access to the nonlinear regime and limits the efficiency, and interpret the experimental results using slowly-varying-amplitude, current-averaged particle-in-cell simulations. We also propose methods for achieving higher efficiencies. PMID:26290153

  20. Chirped pulse Raman amplification in warm plasma: towards controlling saturation.

    PubMed

    Yang, X; Vieux, G; Brunetti, E; Ersfeld, B; Farmer, J P; Hur, M S; Issac, R C; Raj, G; Wiggins, S M; Welsh, G H; Yoffe, S R; Jaroszynski, D A

    2015-01-01

    Stimulated Raman backscattering in plasma is potentially an efficient method of amplifying laser pulses to reach exawatt powers because plasma is fully broken down and withstands extremely high electric fields. Plasma also has unique nonlinear optical properties that allow simultaneous compression of optical pulses to ultra-short durations. However, current measured efficiencies are limited to several percent. Here we investigate Raman amplification of short duration seed pulses with different chirp rates using a chirped pump pulse in a preformed plasma waveguide. We identify electron trapping and wavebreaking as the main saturation mechanisms, which lead to spectral broadening and gain saturation when the seed reaches several millijoules for durations of 10's - 100's fs for 250 ps, 800 nm chirped pump pulses. We show that this prevents access to the nonlinear regime and limits the efficiency, and interpret the experimental results using slowly-varying-amplitude, current-averaged particle-in-cell simulations. We also propose methods for achieving higher efficiencies. PMID:26290153

  1. Emission spectroscopy of laser ablation plasma with time gating by acousto-optic modulator

    SciTech Connect

    Sakka, Tetsuo; Irie, Kyohei; Fukami, Kazuhiro; Ogata, Yukio H.

    2011-02-15

    The capability of acousto-optic modulator (AOM) to perform time-gated measurements for laser ablation plasma spectroscopy has been examined. Especially, we focused on the capability of the ''AOM gating'' to exclude the continuum and extremely broadened spectra usually observed immediately after the laser ablation. Final goal of the use of the AOM is to achieve considerable downsizing of the system for in situ and on-site analyses. In the present paper, it is shown that narrow and clear spectral lines can be obtained with the AOM gating even if the target is submerged in water. Also, application of this technique to the targets in air is demonstrated. It has been revealed that the AOM gating is fast enough to exclude the continuum and broadened lines, while effectively acquiring sufficiently narrow atomic lines lasting slightly longer than the continuum.

  2. Single and Multi-Pulse Low-Energy Conical Theta Pinch Inductive Pulsed Plasma Thruster Performance

    NASA Technical Reports Server (NTRS)

    Hallock, A. K.; Martin, A. K.; Polzin, K. A.; Kimberlin, A. C.; Eskridge, R. H.

    2013-01-01

    Impulse bits produced by conical theta-pinch inductive pulsed plasma thrusters possessing cone angles of 20deg, 38deg, and 60deg, were quantified for 500J/pulse operation by direct measurement using a hanging-pendulum thrust stand. All three cone angles were tested in single-pulse mode, with the 38deg model producing the highest impulse bits at roughly 1 mN-s operating on both argon and xenon propellants. A capacitor charging system, assembled to support repetitively-pulsed thruster operation, permitted testing of the 38deg thruster at a repetition-rate of 5 Hz at power levels of 0.9, 1.6, and 2.5 kW. The average thrust measured during multiple-pulse operation exceeded the value obtained when the single-pulse impulse bit is multiplied by the repetition rate.

  3. Interaction physics of multipicosecond Petawatt laser pulses with overdense plasma.

    PubMed

    Kemp, A J; Divol, L

    2012-11-01

    We study the interaction of intense petawatt laser pulses with overdense plasma over several picoseconds, using two- and three-dimensional kinetic particle simulations. Sustained irradiation with non-diffraction-limited pulses at relativistic intensities yields conditions that differ qualitatively from what is experimentally available today. Nonlinear saturation of laser-driven density perturbations at the target surface causes recurrent emissions of plasma, which stabilize the surface and keep absorption continuously high. This dynamics leads to the acceleration of three distinct groups of electrons up to energies many times the laser ponderomotive potential. We discuss their energy distribution for applications like the fast-ignition approach to inertial confinement fusion. PMID:23215393

  4. Optical spectroscopy study of pulsed excimer laser generated plasma from CuO

    SciTech Connect

    Adhi, K.P.; Kale, S.; Padhye, Y.; Limaye, A.V.; Ogale, S.B.

    1995-12-15

    Optical emissions from pulsed excimer laser induced plasma emanating from CuO target are studied by an Optical Multichannel Analyzer system in the context of its implications for thin film growth by Pulsed Laser Deposition. The plasma is generated in four different ambients viz. hydrogen, helium, oxygen (pressure of 100 mTorr in each case) and vacuum (2 {times} 10{sup {minus}5} Torr) at different energy densities from 1 to 3.5 J/cm{sup 2}. The plasma constituents and their evolution in the growth space (i.e. at a distance of 1.5 cm from the target) has been studied. Various transitions corresponding to Cu(I), H(I), Cu(II) and O(II) are observed. The observation of strong transitions due to O(II) in the plasma formed in vacuum, hydrogen and helium suggests significant degree of ionization of atoms via molecular splitting and inverse Bremsstrahlung process during early plasma formation. The persistence of ionicity in the plasma can be attributed to long recombination lifetimes for the specific conditions used. In the case of ablation in oxygen ambient a very significant and remarkably selective enhancement of the copper vapor lasing transition at 510.5 nm is observed which brings out the role of oxygen molecules in sustaining the radiation trapping condition. The changes in the concentrations of neutrals and ions are a function of the laser energy density are also examined. It is argued that impingement of ions/atoms in an excited state on the growing surface can potentially lead to localized energy deposition via non-radiative deexcitation resulting into enhancement of film quality and density.

  5. Pathogen reduction in human plasma using an ultrashort pulsed laser.

    PubMed

    Tsen, Shaw-Wei D; Kingsley, David H; Kibler, Karen; Jacobs, Bert; Sizemore, Sara; Vaiana, Sara M; Anderson, Jeanne; Tsen, Kong-Thon; Achilefu, Samuel

    2014-01-01

    Pathogen reduction is a viable approach to ensure the continued safety of the blood supply against emerging pathogens. However, the currently licensed pathogen reduction techniques are ineffective against non-enveloped viruses such as hepatitis A virus, and they introduce chemicals with concerns of side effects which prevent their widespread use. In this report, we demonstrate the inactivation of both enveloped and non-enveloped viruses in human plasma using a novel chemical-free method, a visible ultrashort pulsed laser. We found that laser treatment resulted in 2-log, 1-log, and 3-log reductions in human immunodeficiency virus, hepatitis A virus, and murine cytomegalovirus in human plasma, respectively. Laser-treated plasma showed ≥70% retention for most coagulation factors tested. Furthermore, laser treatment did not alter the structure of a model coagulation factor, fibrinogen. Ultrashort pulsed lasers are a promising new method for chemical-free, broad-spectrum pathogen reduction in human plasma. PMID:25372037

  6. Pathogen Reduction in Human Plasma Using an Ultrashort Pulsed Laser

    PubMed Central

    Tsen, Shaw-Wei D.; Kingsley, David H.; Kibler, Karen; Jacobs, Bert; Sizemore, Sara; Vaiana, Sara M.; Anderson, Jeanne; Tsen, Kong-Thon; Achilefu, Samuel

    2014-01-01

    Pathogen reduction is a viable approach to ensure the continued safety of the blood supply against emerging pathogens. However, the currently licensed pathogen reduction techniques are ineffective against non-enveloped viruses such as hepatitis A virus, and they introduce chemicals with concerns of side effects which prevent their widespread use. In this report, we demonstrate the inactivation of both enveloped and non-enveloped viruses in human plasma using a novel chemical-free method, a visible ultrashort pulsed laser. We found that laser treatment resulted in 2-log, 1-log, and 3-log reductions in human immunodeficiency virus, hepatitis A virus, and murine cytomegalovirus in human plasma, respectively. Laser-treated plasma showed ≥70% retention for most coagulation factors tested. Furthermore, laser treatment did not alter the structure of a model coagulation factor, fibrinogen. Ultrashort pulsed lasers are a promising new method for chemical-free, broad-spectrum pathogen reduction in human plasma. PMID:25372037

  7. Colliding Laser Pulses for Laser-Plasma Accelerator Injection Control

    SciTech Connect

    Plateau, G. R.; Geddes, C. G. R.; Matlis, N. H.; Mittelberger, D. E.; Nakamura, K.; Schroeder, C. B.; Esarey, E.; Leemans, W. P.; Cormier-Michel, E.

    2010-11-04

    Decoupling injection from acceleration is a key challenge to achieve compact, reliable, tunable laser-plasma accelerators (LPA). In colliding pulse injection the beat between multiple laser pulses can be used to control energy, energy spread, and emittance of the electron beam by injecting electrons in momentum and phase into the accelerating phase of the wake trailing the driver laser pulse. At LBNL, using automated control of spatiotemporal overlap of laser pulses, two-pulse experiments showed stable operation and reproducibility over hours of operation. Arrival time of the colliding beam was scanned, and the measured timing window and density of optimal operation agree with simulations. The accelerator length was mapped by scanning the collision point.

  8. Colliding Laser Pulses for Laser-Plasma Accelerator Injection Control

    NASA Astrophysics Data System (ADS)

    Plateau, G. R.; Geddes, C. G. R.; Matlis, N. H.; Cormier-Michel, E.; Mittelberger, D. E.; Nakamura, K.; Schroeder, C. B.; Esarey, E.; Leemans, W. P.

    2010-11-01

    Decoupling injection from acceleration is a key challenge to achieve compact, reliable, tunable laser-plasma accelerators (LPA) [1, 2]. In colliding pulse injection the beat between multiple laser pulses can be used to control energy, energy spread, and emittance of the electron beam by injecting electrons in momentum and phase into the accelerating phase of the wake trailing the driver laser pulse [3, 4, 5, 6, 7]. At LBNL, using automated control of spatiotemporal overlap of laser pulses, two-pulse experiments showed stable operation and reproducibility over hours of operation. Arrival time of the colliding beam was scanned, and the measured timing window and density of optimal operation agree with simulations [8]. The accelerator length was mapped by scanning the collision point.

  9. Exploration of pulse timing for multiple laser hits within a combined heat transfer, phase change, and gas dynamics model for laser ablation

    NASA Astrophysics Data System (ADS)

    Mullenix, Nathan; Povitsky, Alex

    2007-05-01

    Laser ablation involves heat transfer, phase changes and/or chemical reactions, and gas dynamics. All three of these processes are tightly coupled with each other. A model has previously been developed to simulate the nanosecond scale laser ablation of carbon. This model has been extended to accommodate longer term simulations and multiple laser pulses. The effects of varying the timing of a second laser pulse by tens of nanoseconds are explored. It is shown that by changing this interval one can control the total mass ablated and the mass transfer rate.

  10. Force-free electromagnetic pulses in a laboratory plasma

    NASA Technical Reports Server (NTRS)

    Stenzel, R. L.; Urrutia, J. M.

    1990-01-01

    A short, intense current pulse is drawn from an electrode immersed in a magnetized afterglow plasma. The induced magnetic field B(r,t) assumes the shape of a helical double vortex which propagates along B(0) through the uniform plasma as a whistler mode. The observations support a prediction of force-free (J x B + neE = 0) electromagnetic fields and solitary waves. Energy and helicity are approximately conserved.

  11. Ablation processing of biomedical materials by ultrashort laser pulse ranging from 50 fs through 2 ps

    NASA Astrophysics Data System (ADS)

    Ozono, Kazue; Obara, Minoru; Sakuma, Jun

    2003-06-01

    In recent years, femtosecond laser processing of human hard/soft tissues has been studied. Here, we have demonstrated ablation etching of hydroxyapatite. Hydroxyapatite (Ca10(PO4)6(OH)2) is a key component of human tooth and human bone. The human bone is mainly made of hydroxyapatite oriented along the collagen. The micromachining of hydroxyapatite is highly required for orthopedics and dentistry. The important issue is to preserve the chemical property of the ablated surface. If chemical properties of hydroxyapatite change once, the human bone or tooth cannot grow again after laser processing. As for nanosecond laser ablation (for example excimer laser ablation), the relative content of calcium and phosphorus in (Ca10(PO4)6(OH)2) is found to change after laser ablation. We used here pulsewidth tunable output from 50 fs through 2 ps at 820 nm and 1 kpps. We measured calcium spectrum and phosphorus spectrum of the ablated surface of hydroxyapatite by XPS. As a result, the chemical content of calcium and phosphorus is kept unchanged before and after 50-fs - 2-ps laser ablation. We also demonstrated ablation processing of human tooth with Ti:sapphire laser, and precise ablation processing and microstructure fabrication are realized.

  12. 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.

  13. A Nanosecond Pulsed Plasma Brush for Surface Decontamination

    NASA Astrophysics Data System (ADS)

    Neuber, Johanna; Malik, Muhammad; Song, Shutong; Jiang, Chunqi

    2015-11-01

    This work optimizes a non-thermal, atmospheric pressure plasma brush for surface decontamination. The generated plasma plumes with a maximum length of 2 cm are arranged in a 5 cm long, brush-like array. The plasma was generated in ambient air with <= 10 kV, 200 ns pulses at a repetition rate of 1.5 kHz. The energy per pulse and average power are in the range of 1-3 mJ and 0.5-1.5 W, respectively. Helium containing varying concentrations of water vapor was evaluated as the carrier gas and was fed into the plasma chamber at a rate varying between 1 to 7 SLPM. Optimization of the cold plasma brush for surface decontamination was tested in a study of the plasma inactivation of two common pathogens, Staphylococcus aureus and Acinetobacter baumannii. Laminate surfaces inoculated with over-night cultured bacteria were subject to the plasma treatment for varying water concentrations in He, flow rates and discharge voltages. It was found that increasing the water content of the feed gas greatly enhanced the bactericidal effect. Emission spectroscopy was performed to identify the reactive plasma species that contribute to this variation. Additional affiliation: Frank Reidy Research Center for Bioelectrics

  14. On-line isotope dilution in laser ablation inductively coupled plasma mass spectrometry using a microflow nebulizer inserted in the laser ablation chamber

    NASA Astrophysics Data System (ADS)

    Pickhardt, Carola; Izmer, Andrej V.; Zoriy, Miroslav V.; Schaumlöffel, D.; Sabine Becker, J.

    2006-02-01

    Laser ablation ICP-MS (inductively coupled plasma mass spectrometry) is becoming one of the most important analytical techniques for fast determination of trace impurities in solid samples. Quantification of analytical results requires matrix-matched standards, which are in some cases (e.g., high-purity metals, proteins separated by 2D gel electrophoresis) difficult to obtain or prepare. In order to overcome the quantification problem a special arrangement for on-line solution-based calibration has been proposed in laser ablation ICP-MS by the insertion of a microflow nebulizer in the laser ablation chamber. This arrangement allows an easy, accurate and precise quantification by on-line isotope dilution using a defined standard solution with an isotope enriched tracer nebulized to the laser-ablated sample material. An ideal matrix matching in LA-ICP-MS is therefore obtained during the measurement. The figures of merit of this arrangement with a microflow nebulizer inserted in the laser ablation chamber and applications of on-line isotope dilution in LA-ICP-MS on two different types of sample material (NIST glass SRM 612 and NIST apple leaves SRM 1515) will be described.

  15. Spectroscopic modeling and characterization of a laser-ablated lithium-silver plasma plume

    NASA Astrophysics Data System (ADS)

    Sherrill, Manolo Edgar

    In this dissertation, the modeling and spectroscopic analysis of optical line emission recorded during the laser ablation of plasma plumes from a solid Li-Ag alloy target is discussed. The spectral model considers the effects of multi-element collisional-radiative atomic kinetics, detailed Stark-broadened line profiles, and radiation transport. To compute the atomic data of neutrals and low-charge ions a semi-empirical procedure was implemented in a Hartree-Fock atomic structure code, that produces a set of wavefunctions consistent with measured energy levels. This procedure is critical to obtain spectroscopic quality atomic data for a transition element like silver. A large database of atomic cross sections and rates was computed to input the atomic kinetics calculations. Detailed line shapes were calculated for the Li and Ag line transitions observed in the experimental spectra taking into account the effects of natural, Doppler, Stark and resonance broadening. The radiation transport equation was solved to calculate the transport of the lines through the plasma and the emitted line intensity distribution. The final synthetic spectra self-consistently includes the Li and Ag line emissions. The temperature and density sensitivity of these spectra is discussed for the case of uniform and non-uniform plasmas. The spectral model was implemented in a versatile and efficient parallel processing code, and applied to the analysis of data recorded in laser ablation experiments performed at Sandia National Laboratories. First, raw data images recorded with a gated, space-resolving spectrograph were corrected for instrument efficiency, and the wavelength and space axes calibrated. Then, a collection of time- and space-resolved spectra lineouts was extracted for analysis. The results of the analysis indicate that early in time and close to the target's surface a dense plasma is formed with electron temperatures in the 1 eV to 2 eV range, and electron densities in the 1 x

  16. Plasma-mediated ablation for the management of obstructive sleep apnea

    NASA Astrophysics Data System (ADS)

    Puchalski, Robert; Shah, Udayan K.

    2000-05-01

    Plasma-mediated ablation (PMA) removes tissue by developing an electrically induced plasma layer between the instrument and target tissue. Charged particles within the plasma field then accelerate toward the tissue, breaking the molecular bonds within the top layer of tissue. Thermal damage to collateral tissue is minimal, resulting in the moniker, 'cold' ablation, for this method. Recently, instrumentation has been developed to permit application for soft tissue resection in Otolaryngology. Presentation of the theory, as well as the benefits and disadvantages associated with CoblationTM technology will be followed by examples of its use. A brief videotape will demonstrate the application of PMA for UPPP, tonsillectomy and nasal turbinate reduction. Preliminary experience from our institution, including eighteen children treated with tonsillectomy and followed for at least one month post-operatively, has provided an initial cohort for comparing the risks and benefits of the approach. The advantage of CoblationTM technology identified thus far, that of less thermal damage, is balanced against a decreased level of hemostasis (compared to MES) and an increased cost.

  17. Exponential frequency spectrum and Lorentzian pulses in magnetized plasmas

    SciTech Connect

    Pace, D. C.; Shi, M.; Maggs, J. E.; Morales, G. J.; Carter, T. A.

    2008-12-15

    Two different experiments involving pressure gradients across the confinement magnetic field in a large plasma column are found to exhibit a broadband turbulence that displays an exponential frequency spectrum for frequencies below the ion cyclotron frequency. The exponential feature has been traced to the presence of solitary pulses having a Lorentzian temporal signature. These pulses arise from nonlinear interactions of drift-Alfven waves driven by the pressure gradients. In both experiments the width of the pulses is narrowly distributed resulting in exponential spectra with a single characteristic time scale. The temporal width of the pulses is measured to be a fraction of a period of the drift-Alfven waves. The experiments are performed in the Large Plasma Device (LAPD-U) [W. Gekelman et al., Rev. Sci. Instrum. 62, 2875 (1991)] operated by the Basic Plasma Science Facility at the University of California, Los Angeles. One experiment involves a controlled, pure electron temperature gradient associated with a microscopic (6 mm gradient length) hot electron temperature filament created by the injection a small electron beam embedded in the center of a large, cold magnetized plasma. The other experiment is a macroscopic (3.5 cm gradient length) limiter-edge experiment in which a density gradient is established by inserting a metallic plate at the edge of the nominal plasma column of the LAPD-U. The temperature filament experiment permits a detailed study of the transition from coherent to turbulent behavior and the concomitant change from classical to anomalous transport. In the limiter experiment the turbulence sampled is always fully developed. The similarity of the results in the two experiments strongly suggests a universal feature of pressure-gradient driven turbulence in magnetized plasmas that results in nondiffusive cross-field transport. This may explain previous observations in helical confinement devices, research tokamaks, and arc plasmas.

  18. Preclinical investigations of articular cartilage ablation with femtosecond and pulsed infrared lasers as an alternative to microfracture surgery

    PubMed Central

    Su, Erica; Sun, Hui; Juhasz, Tibor; Wong, Brian J. F.

    2014-01-01

    Abstract. Microfracture surgery is a bone marrow stimulation technique for treating cartilage defects and injuries in the knee. Current methods rely on surgical skill and instrumentation. This study investigates the potential use of laser technology as an alternate means to create the microfracture holes. Lasers investigated in this study include an erbium:YAG laser (λ=2.94  μm), titanium:sapphire femtosecond laser system (λ=1700  nm), and Nd:glass femtosecond laser (λ=1053  nm). Bovine samples were ablated at fluences of 8 to 18  J/cm2 with the erbium:YAG laser, at a power of 300±15  mW with the titanium:sapphire femtosecond system, and at an energy of 3  μJ/pulse with the Nd:glass laser. Samples were digitally photographed and histological sections were taken for analysis. The erbium:YAG laser is capable of fast and efficient ablation; specimen treated with fluences of 12 and 18  J/cm2 experienced significant amounts of bone removal and minimal carbonization with saline hydration. The femtosecond laser systems successfully removed cartilage but not clinically significant amounts of bone. Precise tissue removal was possible but not to substantial depths due to limitations of the systems. With additional studies and development, the use of femtosecond laser systems to ablate bone may be achieved at clinically valuable ablation rates. PMID:25200394

  19. Preclinical investigations of articular cartilage ablation with femtosecond and pulsed infrared lasers as an alternative to microfracture surgery

    NASA Astrophysics Data System (ADS)

    Su, Erica; Sun, Hui; Juhasz, Tibor; Wong, Brian J. F.

    2014-09-01

    Microfracture surgery is a bone marrow stimulation technique for treating cartilage defects and injuries in the knee. Current methods rely on surgical skill and instrumentation. This study investigates the potential use of laser technology as an alternate means to create the microfracture holes. Lasers investigated in this study include an erbium:YAG laser (λ=2.94 μm), titanium:sapphire femtosecond laser system (λ=1700 nm), and Nd:glass femtosecond laser (λ=1053 nm). Bovine samples were ablated at fluences of 8 to 18 J/cm2 with the erbium:YAG laser, at a power of 300±15 mW with the titanium:sapphire femtosecond system, and at an energy of 3 μJ/pulse with the Nd:glass laser. Samples were digitally photographed and histological sections were taken for analysis. The erbium:YAG laser is capable of fast and efficient ablation; specimen treated with fluences of 12 and 18 J/cm2 experienced significant amounts of bone removal and minimal carbonization with saline hydration. The femtosecond laser systems successfully removed cartilage but not clinically significant amounts of bone. Precise tissue removal was possible but not to substantial depths due to limitations of the systems. With additional studies and development, the use of femtosecond laser systems to ablate bone may be achieved at clinically valuable ablation rates.

  20. ICRF Heated Long-Pulse Plasma Discharges in LHD

    NASA Astrophysics Data System (ADS)

    Kumazawa, R.; Seki, T.; Mutoh, T.; Saito, K.; Watari, T.; Nakamura, Y.; Sakamoto, M.; Watanabe, T.; Kubo, S.; Shimozuma, T.; Yoshimura, Y.; Igami, H.; Takeiri, Y.; Oka, Y.; Tsumori, K.; Osakabe, M.; Ikeda, K.; Nagaoka, K.; Kaneko, O.; Miyazawa, J.; Morita, S.; Narihara, K.; Shoji, M.; Masuzaki, S.; Goto, M.; Morisaki, T.; Peterson, B. J.; Sato, K.; Tokuzawa, T.; Ashikawa, N.; Nishimura, K.; Funaba, H.; Chikaraishi, H.; Notake, T.; Torii, Y.; Okada, H.; Ichimura, M.; Higaki, H.; Takase, Y.; Kasahara, H.; Shimpo, F.; Nomura, G.; Takahashi, C.; Yokota, M.; Kato, A.; Zhao, Yanping; Yoon, J. S.; Kwak, J. G.; Yamada, H.; Kawahata, K.; Ohyabu, N.; Ida, K.; Nagayama, Y.; Noda, N.; Komori, A.; Sudo, S.; Motojima, O.; LHD Experimental Group

    2006-01-01

    A long-pulse plasma discharge for more than 30 min. was achieved on the Large Helical Device (LHD). A plasma of ne = 0.8× 1019 m-3 and Ti0 = 2.0 keV was sustained with PICH = 0.52 MW, PECH = 0.1 MW and averaged PNBI = 0.067 MW. Total injected heating energy was 1.3 GJ, which was a quarter of the prepared RF heating energy. One of the keys to the success of the experiment was a dispersion of the local plasma heat load to divertors, accomplished by shifting the magnetic axis inward and outward.