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Previously, hydrodynamic simulations [Clark et al., Phys. Plasmas 23, 072707 (2016)] suggested that precisely tailoring the capsule ablator thickness (shimming) could counterbalance cylindrical Hohlraum Legendre P4 drive asymmetries at the capsule in laser indirect drive implosions. As a result, the stagnated deuterium–tritium (DT) fuel areal density P4 asymmetry is reduced, potentially resulting in a nuclear yield increase. Inflight radiographs of various level of shimmed capsules with plastic (CH) ablators showed that shims can indeed control the in-flight capsule shell P4 asymmetry, with a linear sensitivity to shim amplitude that is close to analytic estimates and simulations. Furthermore, the stagnated DT fuel areal density P4 asymmetry inferred from downscattered neutron imaging was reduced when the capsule shim was applied, in agreement with simulations matching the inflight shell asymmetry. A nuclear yield improvement via shim was not observed, as predicted, likely due to implosion instabilities and as built capsule shim deviations from an ideal P4 shape. [ABSTRACT FROM AUTHOR]

At present, the use of microstructure to change the optical properties and wetting properties of the material itself has become the main means to improve the utilization rate of materials in the manufacturing industry. Due to the hydrophilicity of the material surface can achieve underwater self-cleaning, directional transportation function, it becomes an indispensable part of surface modification. Water jet-guide laser processing can significantly reduce the formation of the heat-affected zone and crack, and can clearly ablate the material, with higher precision and resolution. In this experiment, the effects of scan spacing, laser output power and channel aspect ratio are examined and processing conditions for achieving near superhydrophilicity are provided. Owing to the anaerobic processing environment, the surface chemical composition of the material does not change, and the hydrophilicity is increased by 8% to 43% compared with that before. Increasing the aspect ratio can increase the wettability, when the aspect ratio is more than 1.63, the wettability begins to rebound, and the wettability becomes worse. Using small laser power and multiple scanning processing scheme can make the surface covered with tiny small pillars of micro-nano particles layer beneficial to increase the droplet adhesion, and the minimum contact angle can reach 37.2°. [ABSTRACT FROM AUTHOR]

Nanoparticle (NP) analysis performed by laser ablation–single particle-inductively coupled plasma mass spectrometry (LA-sp-ICPMS) has recently allowed for multimodal insights to be gained about NPs in biological tissues. In our previous work, NP localizing, sizing and counting, as well as differentiating between the metal NP signal and its ionic form were achieved. In all of these, a low laser fluence (<1 J cm−2) was used, as it was observed that higher laser fluences can induce NP degradation, thus invalidating the results. This work is an in-depth study of gold NP (AuNP) degradation upon laser ablation, and provides guidelines for selection of the optimal laser fluence associated with NP analysis in gelatine as a matrix which mimics biological tissues. AuNPs of known size and with a narrow size distribution (CV < 5%) were used to keep track of the measured NP size with changing laser fluence. In addition, optical profilometry was utilized to measure the amount of material ablated as a function of the laser fluence, and provide a more accurate estimation of the NP degradation. [ABSTRACT FROM AUTHOR]

Background: One of the most critical issues concerning in situ mass spectrometry lies in accounting for elements and molecules that overlap target isotopes of analytical interest in a sample. This study traced the instrumental mass fractionation of Rb and Sr isotopes during laser ablation-multicollector-inductively coupled plasma mass spectrometry (LA-MC-ICPMS) to obtain reliable 87Sr/86Sr ratios for high-Rb/Sr samples. Findings: In the LA-MC-ICPMS analysis, Kr interferences were corrected using Ar and He gas blanks measured without ablating material. Contributions from doubly charged Er and Yb ions were corrected using the intensities of half masses and isotopic compositions reported in the literature. After Kr correction, the calculated 166Er2+ intensity of NIST SRM 610 approached the measured intensity at mass 83, and the 173Yb2+/171Yb2+ ratio agreed with the recommended value within error ranges. Kr- and REE2+-stripped peak intensities were further corrected for Rb interference. Use of the Sr mass bias factor for the calculation of measured 87Rb/85Rb yielded 87Sr/86Sr ratios consistent with the recommended and expected values for low-Rb/Sr materials, such as NIST SRM 616, modern shark teeth, and plagioclase collected from Jeju Island, but failed to account for the 87Rb interference from high-Rb/Sr materials including NIST SRM 610 and SRM 612. We calculated in situ mass bias factor of Rb from the known 87Sr/86Sr ratios of the standards and observed a correlation between Rb and Sr mass fractionation, which allowed inference of the Rb bias from the standard run. Reliable 87Sr/86Sr and 85Rb/86Sr ratios were obtained for SRM 610 and SRM 612 using the inferred mass bias factor of Rb calculated by the standard bracketing method. Conclusions: This study revealed that Rb and Sr isotopes behave differently during LA-MC-ICPMS and suggests the potential usefulness of the standard bracketing method for measuring the Rb–Sr isotopic compositions of high-Rb/Sr materials. [ABSTRACT FROM AUTHOR]

The article discusses the study on patient-centered classifications of laser skin resurfacing. Topics discussed include the use of laser resurfacing in cosmetic dermatology and treatment of photoageing, scarring, and skin diseases, the classification of lasers such as ablative, non-ablative, and fractional lasers, and its side effects such as erythema, exudate, and oedema.

Currently available ablative fractional CO2 lasers provide excellent results and diminish down time with fewer complications than previous generation CO2 lasers. Mechanisms of action, treatment parameters, as well as pre- and postoperative care will be discussed. [ABSTRACT FROM AUTHOR]

The velocity and remaining ablator mass of an imploding capsule are critical metrics for assessing the progress toward ignition of an inertially confined fusion experiment. These and other ablator rocket parameters have been measured using a single streaked x-ray radiograph. A regularization technique has been used to determine the ablator density profile ρ(r) at each time step; moments of ρ(r) then provide the areal density, average radius, and mass of the unablated, or remaining, ablator material, with the velocity determined from the time derivative of the average radius. The technique has been implemented on experiments at the OMEGA laser facility. [ABSTRACT FROM AUTHOR]

Targets intended to produce ignition on NIF are being simulated and the simulations are used to set specifications for target fabrication and other program elements. Recent design work has focused on designs that assume only 1.0 MJ of laser energy instead of the previous 1.6 MJ. To perform with less laser energy, the hohlraum has been redesigned to be more efficient than previously, and the capsules are slightly smaller. Three hohlraum designs are being examined: gas fill, SiO2 foam fill, and SiO2 lined. All have a cocktail wall, and shields mounted between the capsule and the laser entrance holes. Two capsule designs are being considered. One has a graded doped Be(Cu) ablator, and the other graded doped CH(Ge). Both can perform acceptably with recently demonstrated ice layer quality, and with recently demonstrated outer surface roughness. Complete tables of specifications are being prepared for both targets, to be completed this fiscal year. All the specifications are being rolled together into an error budget indicating adequate margin for ignition with the new designs. The dominant source of error is hohlraum asymmetry at intermediate modes 4–8, indicating the importance of experimental techniques to measure and control this asymmetry. [ABSTRACT FROM AUTHOR]

A formed laser source, using a four-element lenticular array, is used in the ablative regime to generate select, narrowband, acoustic plate waves. The arrangement of the array produces acoustical signals that have frequencies compatible with the response of the broadband capacitive air-coupled transducer used in this study. A simplified concept is presented to explain the effect of a line array source on the frequency content of acoustic waves. The analytical model for a point pulse surface displacement is derived from the point load solution to Lamb's problem. The point pulse displacement elements of a line array source are summed mathematically, taking into account all applicable propagation modes and dispersion of plate waves. The model considers only the out-of-plane displacement of the antisymmetric plate modes to represent the detection capability of the broadband receiver. The distribution function of the laser beam energy profile is modified to depict the actual energy distribution that illuminates the surface of the plate. Filtering functions are made compatible with the sensitivity of the broadband receiver so as to retain only the detected frequencies in the model. The theoretical model showed good agreement with experimental results. [ABSTRACT FROM AUTHOR]

A technique has been developed for studying the time-dependent, local physical conditions in ablator samples in an inertial confinement fusion (ICF) hohlraum environment. This technique involves backlit point-projection absorption spectroscopy of thin tracer layers buried in the interior of solid samples mounted on laser-driven hohlraums. It is shown how detailed view-factor, atomic, hydrodynamics, and radiation-transport modeling can be used to infer time-dependent physical conditions in the interiors of these samples from the observed absorption spectra. This modeling is applied to the results of an experimental campaign on the OMEGA laser [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)] designed to compare radiation-wave velocities in doped and undoped ICF ablator materials. [ABSTRACT FROM AUTHOR]

Laser-supported propulsion of a micro-airplane with a water-covered ablator is demonstrated. The repetitive use of an overlay structure is experimentally demonstrated with a specially designed water supply. Various transparent overlays are investigated by the CIP-based hydrodynamic code and by experiments using a pendulum and using a semi-conductor load cell. A momentum-coupling efficiency of ∼ 10[SUP4]N s/MJ is achieved by water-exotic-target experiments, in agreement with the simulation code, which predicts a maximum efficiency of ∼ 10[SUP5]N s/MJ. The concept of laser-supported propulsion can also be used for driving a Mach 5 airplane in the stratosphere, a micro-ship inside the human body, and a robot in a nuclear power reactor accident, during which large numbers of neutrons make electronic devices useless. [ABSTRACT FROM AUTHOR]

• Effects of laser irradiation on composites were studied for composites laser machining. • Ablation behaviors of homogeneous materials and their composites were compared. • A thermal-mechanical coupling existed in composites' interface while laser irradiating. • Composites with smaller particles was closer to homogeneous materials in ablative behavior. • SiC particles enhanced composites' optical absorptivity and decreased its damage threshold. In this study, homogenous Al alloy and SiC materials and SiC p /AA2024 composites with mean particle diameters of 5 μm and 30 μm were irradiated by a single-pulse nanosecond fiber laser with a 200 ns pulse width and 1064 nm wavelength. Using a laser pulse, regular circular heat-affected zones (HAZ) were formed in the homogenous materials. For the composites, an Al allloy matrix was melted and sputtered, and the SiC particles bulged when irradiated by the laser pulse. According to the measured results, the HAZ increased with the pulse energy density in a logarithmic pattern. Nonlinear fitting results demonstrated that the damage thresholds of the composites and SiC homogenous materials were the lowest and highest, respectively. SiC p /AA2024 composites with different mean particle diameters exhibited similar damage thresholds. The measured etching depths of the SiC particles and Al alloy matrix were smaller than the respective values of the homogenous materials. Thermal simulation results revealed that thermal-mechanical coupling occurred between the SiC particles and Al alloy matrix. The SiC particles in the composite heated more rapidly under a nanosecond laser, and the heat was then transferred to the matrix. Large SiC particles constrained the matrix's molten pool, which accelerated its gasification but hindered further etching. [ABSTRACT FROM AUTHOR]

• Weighing experiments while ablating copper with ultra-short pulses were carried out. • The thrust was measured during processing with single-, double- and triple pulses. • The thrust is 2 times higher when using double pulses instead of single pulses. • The mass specific thrust for single and triple pulses is similar. • The mass specific thrust for double pulses is increased by up to a factor of 3. Investigations on the thrust generated during ablation of copper with single, double, or triple ultra-short laser pulses are presented in this paper with the goal to find the optimum parameters for laser propulsion thrusters. On the basis of high-precision weighing experiments, it is shown that the material initially ablated by the first pulse and redeposited by the second pulse of a double pulse leads to a significant increase of thrust. Hence, double pulses are a suitable method to propel vessels in space with enhanced thrust values while at the same time saving propellant material. [ABSTRACT FROM AUTHOR]

At Los Alamos, we have been working on two-dimensional capsule-Hohlraum implosion calculations for the NIF that utilize a laser drive pulse that peaks at ∼300 eV and uses about 1 MJ of laser energy. We use a 0.3 at. % uniformly Cu doped beryllium ablator capsule that has an inner ice radius of 753 μm, inner ablator radius of 825 μm, and an outer ablator radius of 1000 μm. Our Hohlraum has a diameter of 5.02 mm and a length of 8.56 mm. We use a Hohlraum gas fill density of 1.3 mg/cm3 and obtain ignition with yields up to 9.8 MJ, but we also have some failures due to bad shock timing or different pointing positions of the inner and outer laser cones. We describe the salient features of our implosions and show postprocessed diagnostic signatures from x-ray and neutron images, along with reaction history plots to show how we can diagnose “failures” and how to correct for them based on these diagnostics. [ABSTRACT FROM AUTHOR]

• Thermal damage reduction at the laser input energy densities E L−Input < 40 J/mm2. • Thermal ablation with nanosecond laser in contrast with the picosecond laser. • No effect of heat affected zone at E L−Input < 6.25 J/mm2. • Efficiency of laser ablation for both applied lasers was almost in a same range. Silicon nitride (Si 3 N 4) has exceptional mechanical, thermal and chemical properties and is therefore, advantageous for many applications. However, the employment of Si 3 N 4 is impeded by the high finishing cost. Short and ultrashort pulse laser ablation are considered as a non-contact machining processes and are utilised in recent years to overcome constrains of conventional machining of Si 3 N 4. However, there is still a lack of research on the effects of different laser parameters such as pulse duration on the mechanism of laser ablation. In this study, laser-material interaction of two different types of solid-state lasers with 10 ps and 100 ns pulse durations was investigated at the constant power of 50 W on a Si 3 N 4 workpiece. The width of thermal damages and heat-affected zone (HAZ) is extremely reduced within laser input energy density (E L−Input) less than 40 J/mm2 for both types of laser. It is found that in case of the nanosecond laser ablation, molten droplets inside the laser cut prevent diffusion of the laser beam at E L−Input higher than 62.5 J/mm2. This effect could not be observed in ablation with the picosecond laser. Compared to the nanosecond laser, the picosecond laser is more efficient for ablating the workpiece material at laser input energy densities higher than 120 J/mm2. [ABSTRACT FROM AUTHOR]

This letter reports observation of ablated holes as small as 0.7 μm fabricated by single 25 ns pulses of KrF (λ=248 nm) laser focused onto a 5.6 μm spot. Samples with high thermal conductivity films with respect to that of the substrate (Si/silica, Al/glass) repeatedly showed considerable reduction in the size of the ablated spot (0.7- and 1.2-μm-diam holes, respectively). This letter also presents a likely mechanism of the observed super-resolution and the criteria necessary to achieve super-resolution. Due to the nonoptical origin of this effect it is expected that a tightly focused (<0.5 μm) laser beam can be used to ablate with nanoscale (<100 nm) resolution. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

In this article the author presents the studies concerning biological consequences of light-tissue interactions in laser surgery. The author features the study of Orringer and colleagues on the techniques to investigate the nonablative laser treatment's molecular consequences. The author also discusses the findings of Orringer and colleagues that superficial and deeper treatments show minimal differences and the similarity of the volume of its wounded tissue.

Since the approval of the first phase of the Fast-Ignition Realization Experiment (FIREX-I), we have devoted our efforts to designing advanced targets and constructing a petawatt laser, which will be the most energetic petawatt laser in the world. Scientific and technological improvements are required to efficiently heat the core plasma. There are two methods that can be used to enhance the coupling efficiency of the heating laser to the thermal energy of the compressed core plasma: adding a low-Z foam layer to the inner surface of the cone and employing a double cone. The implosion performance can be improved in three ways: adding a low-Z plastic layer to the outer surface of the cone, using a Br-doped plastic ablator and evacuating the target centre. An advanced target for FIREX-I was introduced to suit these requirements. A new heating laser (LFEX) has been constructed that is capable of delivering an energy of 10 kJ in 10 ps with a 1 ps rise time. A fully integrated fast-ignition experiment is scheduled for 2009. [ABSTRACT FROM AUTHOR]