mJ Laser Energy Research Articles

Laser lithotripsy for pancreatic duct stones

Aim. To confirm the possibility of minimally-invasive laser procedure for fragmentation of stones in the pancreatic duct following the results of laboratory experiments and medical practice. Materials and methods. A fully functional hardware complex consisting of a pulsed laser unit, video endoscopic system and cooling system was created for experimental stone fragmentation in laboratory. The experiments involved microscopic video registration of the fragmentation process, pressure and temperature measurement in the stone area. Pancreatic stones, human and artificial gallstones as well as porcine pancreas were used in the experiments; the gastrointestinal tract was made of silicone, the pancreas was made of gelatin aqueous solution jelly. In clinical practice, a patient with lithiasis of Wirsung's duct was assigned to ultrasound and CT, then endoscopic papillosphincterotomy, endoscopic pancreatoscopy, laser lithotripsy and lithoextraction, pancreatic duct stenting. The procedures involved a laser unit, videoduodenoscope, catheter and their video systems. Results. The laboratory experiments established that effective and safe laser fragmentation of stones from 4 × 7 mm into 0.1–2 mm occurs in the flowing fluid in front of the stone at 1 μs laser pulse duration, 5–15 Hz frequency and 120–150 mJ laser energy. After laser fragmentation of the stone in a patient with virsungolithiasis and removal of fragments from the duct, the patient was discharged from the hospital on the 12th day due to improvement of healthcondition. Conclusion. The possibility of minimally-invasive fragmentation of stones in the pancreatic duct by laser lithotripsy has been proved.

Gigahertz electromagnetic pulse emission from femtosecond relativistic laser-irradiated solid targets.

The interactions between high-intensity laser and matter produce particle flux and electromagnetic radiation over a wide energy range. The generation of extremely intense transient fields in the radio frequency-microwave regime has been observed in femtosecond-to-nanosecond laser pulses with 1011-1020-W/cm2 intensity on both conductive and dielectric targets. These fields typically cause saturation and damage to electronic equipment inside and near an experimental chamber; nevertheless, they can also be effectively used as diagnostic tools. Accordingly, the characterization of electromagnetic pulses (EMPs) is extremely important and currently a popular topic for present and future laser facilities intended for laser-matter interaction. The picosecond and sub-picosecond laser pulses are considerably shorter than the characteristic electron discharge time (∼0.1 ns) and can be efficient in generating GHz EMPs. The EMP characterization study of femtosecond laser-driven solid targets is currently mainly in the order of 100 mJ laser energy, in this study, the EMP generated by intense (Joule class) femtosecond laser irradiation of solid targets has been measured as a function of laser energy, laser pulse duration, focal spot size, and target materials. And a maximum electric field of the EMP reaching up to 105 V/m was measured. Analyses of experimental results confirm a direct correlation between measured EMP energy and laser parameters in the ultrashort pulse duration regime. The EMP signals generated by femtosecond laser irradiation of solid targets mainly originate from the return current inside the target after hot electron excitation. Numerical simulations of EMP are performed according to the target charging model, which agree well with the experimental results.

Effect of laser shock peening on surface integrity and tensile fatigue behavior of TB8 bolts

Laser shock peening (LSP) treatment was introduced to improve tensile fatigue behavior of TB8 titanium alloy bolt. TB8 bolts surface integrity, tensile fatigue fracture and strengthening mechanism after LSP treatment were systematically investigated. Results showed that cracks and machining defects on the thread surface were eliminated, surface layer microhardness and compressive residual stress were increased after LSP treatment. Meanwhile, the grains sizes of the LSP treated bolts samples were reduced to 38.61 μm with the formation of high density dislocations. LSP treated bolts samples with 80 mJ laser energy exhibited the maximum average tensile fatigue life, which was increased from 66,452 cycles to 81,319 cycles. In addition, under the synergistic effect of compressive residual stress and grains refinement, cracks propagation path was changed, which were the primary factors for the improvement of TB8 bolt tensile fatigue life.

Effect of laser cavitation peening on surface integrity and electrochemical corrosion behavior of magnesium alloy

A novel method of laser cavitation peening (LCP) was employed to process the AZ31B magnesium (Mg) alloy. The processes of bubble evolution and LCP impact were investigated. The influences of LCP on the surface integrity (surface morphology and roughness, microhardness, residual stress, phase) and electrochemical corrosion behavior of AZ31B Mg alloy under various processing parameters (laser energy and defocusing amount) were systemically investigated. The results show that the laser breakdown extent, bubble radius, pulsation period, and bubble energy increase with the increase of laser energy. The maximum radius of the cavitation bubble decreases significantly as the defocusing amount increases from 0 mm to 2 mm. LCP enhances the microhardness and introduces the compressive residual stress into the surface layer of the AZ31B, but it also increases the surface roughness. The surface morphology of LCP processed AZ31B has significant differences under various processing parameters, and the microhardness and residual stress increase as increasing the laser energy. LCP improves the anti-corrosion of AZ31B effectively except for the condition of 200 mJ laser energy. The best defocusing amount for enhancing the surface integrity and electrochemical performance of AZ31B by LCP processing is 1 mm, and the higher laser energy has the better corrosion resistance.

Semi-hydro-equivalent design and performance extrapolation between 100 kJ-scale and NIF-scale indirect drive implosion

Extrapolation of implosion performance between different laser energy scales is investigated for indirect drive through a semi-hydro-equivalent design. Since radiation transport is non-hydro-equivalent, the peak radiation temperature of the hohlraum and the ablation velocity of the capsule ablator are not scale-invariant when the sizes of the hohlraum and the capsule are scale-varied. A semi-hydro-equivalent design method that keeps the implosion velocity Vi, adiabat αF, and PL/Rhc2 (where PL is the laser power and Rhc is the hohlraum and capsule scale length) scale-invariant, is proposed to create hydrodynamically similar implosions. The semi-hydro-equivalent design and the scaled implosion performance are investigated for the 100 kJ Laser Facility (100 kJ-scale) and the National Ignition Facility (NIF-scale) with about 2 MJ laser energy. It is found that the one-dimensional implosion performance is approximately hydro-equivalent when Vi and αF are kept the same. Owing to the non-hydro-equivalent radiation transport, the yield-over-clean without α-particle heating (YOCnoα) is slightly lower at 100 kJ-scale than at NIF-scale for the same scaled radiation asymmetry or the same initial perturbation of the hydrodynamic instability. The overall scaled two-dimensional implosion performance is slightly lower at 100 kJ-scale. The general Lawson criterion factor scales as χnoα2D∼S1.06±0.04 (where S is the scale-variation factor) for the semi-hydro-equivalent implosion design with a moderate YOCnoα. Our study indicates that χnoα ≈ 0.379 is the minimum requirement for the 100 kJ-scale implosion to demonstrate the ability to achieve marginal ignition at NIF-scale.

Studies on photovoltaic properties of BFO/WO3 bilayer thin films for solar energy harvesting applications

BFO possess high remnant polarization (∼100 μC/cm2) and low direct band gap (∼2.7 eV) having potential for photovoltaic (PV) applications. In the present work, WO3 insulating layer is utilized with BFO and BFO/WO3 bilayer thin film structure is fabricated for reducing the leakage current along with possessing the low band gap and high ferroelectric polarization. In BFO/WO3 bilayer structure, the WO3 nanostructured thin film layer was fabricated utilizing rf-magnetron sputtering technique under the optimized parameters while BFO thin film layer was fabricated by altering the incident energy of excimer laser (150 mJ − 250 mJ) in Pulsed Laser deposition technique. BFO/WO3 bilayer structure prepared at 200 mJ laser energy demonstrated the superior ferroelectric properties (Ps = 63.24 µC/cm2 and Pr = 25.94 µC/cm2) with high values of short circuit photocurrent density (Jsc = ∼18 mA/cm2) and open-circuit voltage (Voc = ∼320 mV) under the UV illumination of Intensity = 160 mW/cm2 and λ = 355 nm. Obtained results suggest the utilization of prepared BFO/WO3 bilayer thin film structures on future novel energy harvesting purposes.

Influence of sample temperature and ambient argon pressure on LIBS spectra of extracted animal fat

This work explores the influence of sample temperature, ambient gas pressure, laser energy, and detector gate delay (DGD) on the LIBS emissions of extracted animal fat. The emissions from laser-induced plasma of extracted animal fat were acquired with varying sample temperatures, ambient argon pressure, laser energy, and detector gate delay. A thermoelectric system fitted with a temperature-controlling sensor was used to control the sample temperature. For maximum optical emission intensity, the detector gate delay (DGD) shifted toward a lower value with the increase in sample temperature for all ambient argon pressures. The nine-fold signal enhancement, ten times improvement in signal-to-noise ratio (SNR), and significantly reduced self-absorption were observed in all detected emission lines recorded at 200 mJ laser energy –2 ºC sample temperature, 375 Torr ambient argon pressure, and 2 µs DGD. The repeatability of emission signals was evaluated by calculating the relative standard deviation (RSD) of the emission line (Zn I (636.23 nm)) at different sample temperatures, which improved from 35 % to 6 % when the sample changed from liquid to solid (frozen). During the semi-liquid form of fat, the decreasing ambient gas pressure did not significantly affect signal repeatability. In addition to diagnosing the fat plasma, the plasma temperature and electron number density have been evaluated as a function of sample temperature and ambient argon pressure.

Metal micro/nanostructure enhanced laser-induced breakdown spectroscopy

This study used a femtosecond laser to ablate a Cu sample, forming a micro/nanostructural layer on the surface. And the effect of this structural layer on nanosecond laser-induced breakdown spectroscopy (LIBS) was discussed. Firstly, the effect of the micro/nanostructural layer on the intensity of laser-induced Cu plasma spectra was investigated. The micro/nanostructure could significantly enhance the spectral intensity of the Cu plasma by 82.5 times at 13.3 mJ laser energy. Secondly, the Cu plasma temperature and electron density were calculated. The micro/nanostructures could significantly increase Cu plasma temperature and electron density. Finally, the effect of micro/nanostructure surface on the spectral intensities of Pb and Cr elements in water was investigated for LIBS analysis. It was found that the detection limit of Pb and Cr trace metal elements in water was 1.85 ng/mL and 0.51 ng/mL at a lower laser energy (13.3 mJ), which was significantly better than other LIBS methods reported so far. The results show that the micro/nanostructure enhanced LIBS is a more sensitive method for detecting trace metal elements in the water.

Magnetic field confined laser-induced plasma: Improvement in sensitivity and repeatability

In this work, the transverse magnetic field confined laser-induced breakdown spectroscopy (MC-LIBS) technique was applied to investigate the signal sensitivity and repeatability of Al alloy plasma in the specially designed assembly. The emission signals from laser-induced plasma were recorded with varying laser energy (80 to 160 mJ) and magnetic field strength (1 to 3.5 kG). An emission signal enhancement up to 7 times was observed at 140 mJ laser energy and at 3 kG magnetic field strength. Compared to conventional LIBS, the magnetic field confined-LIBS improved the signal-to-noise ratio (SNR) by up to 5 times and the detection limit (LOD) from 86 to 26 ppm for zinc emission lines. Repeatability was evaluated using the relative standard deviation (RSD) of the Mg and Si emission lines, which was improved from 23 to 12% and 25 to 14%, respectively. Similarly, the measurement-to-measurement RSDs in electron temperature (Te) and electron number density (Ne) were improved from 12 to 7% and 1 3 to 5% when compared with conventional LIBS.

Aqueous ruthenium detection by microwave-assisted laser-induced breakdown spectroscopy

Aqueous ruthenium was detected in real-time under ambient conditions using microwave-assisted laser-induced breakdown spectroscopy (MW-LIBS). A 10 mJ laser energy and 750 W microwave power were directed at an open liquid jet sample of ruthenium. It was observed that, for liquid flow, the coupling efficiency between the microwave and the laser-induced plasma was limited to 43%. The improvement in the ruthenium’s signal-to-noise ratio with MW-LIBS, with respect to LIBS, was 76-fold. Based on MW-LIBS, the limit of detection for aqueous ruthenium was determined to be 957 ± 84 ppb.

Effect of Au and Ag nanoparticles addition on the morphological, structural and optical properties of ZnO thin films deposited by sol-gel method

In the present study, ZnO thin films were deposited on quartz substrates by sol-gel spincoating method. Zinc-diacetate ((Zn(CH3COO)2.2H2O), diolamine (DEA) (HN(CH2CH2OH)2) and ethylene glycol monomethyl ether (CH3OCH2CH2OH) were used as a precursor, stabilizer agent, and solvent, respectively. Au and Ag NPs were synthesized by (PLAL) technique using “Q-Switched ND-YAG laser” system with laser parameters (520 mJ laser energy, 1064 nm wavelength, 450 laser pulses, and 1Hz frequency). The volumetric ratios of ZnO source solution to Au and Ag colloidal solutions were 3:2 and 4:1, respectively. The morphological, structural and optical properties of ZnO thin films embedded with Au and Ag NPs were investigated. The patterns of x-ray diffraction (XRD) showed peaks indexed to (100), (002) and (101) planes for ZnO and (111), (200) and (220) for Au and Ag NPs. The surface morphology of the films was examined by FESEM and the Raman spectra of ZnO thin films embedded with Ag and Au NPs were investigated. Furthermore, the optical properties of the films were analyzed by UV-Vis spectroscopy measurements. The optical band gap of the films increased with increasing the volumetric ratios of ZnO embedded with Au and Ag NPs.

The influence of aluminum nanoparticles on the laser ablation characteristics of hydroxylamine nitrate-based liquid propellants

Hydroxylamine nitrate is a nontoxic green energetic propellant that has a high energy density and wide application prospects in the field of aerospace propulsion. Here, the laser ablation and propulsion properties of hydroxylamine nitrate-based propellants doped with aluminum nanoparticles were studied. The results showed a significant improvement in the laser absorption properties of hydroxylamine nitrate doped with aluminum nanoparticles. The maximum absorption rate increased by more than 80%, while the absorption depth decreased considerably with a minimum of 277 μm. The sputtering behavior also weakened during laser ablation, and the impulse of hydroxylamine nitrate could be enhanced by doping aluminum nanoparticles. With the 0.7wt% mass fraction of aluminum nanoparticles, a maximum impulse bit of 57.55 μN·s at 90 mJ laser energy. This is led to a maximum energy conversion efficiency of 218.1% and an enhancement of the kinetic energy of the hydroxylamine nitrate-based propellant of 56% with laser energy of 25 mJ. Compared with ordinary liquid propellants, doped samples have better propulsion performance.

Laser shock dynamic compaction of aluminum powder

Dynamic compaction establishes shock waves that produces a violent dynamic mechanical response in powder. This process can realize the high-density compaction of powder to fabricate the compact of powder metallurgy parts with excellent performance. A new method for dynamic compaction of powder using laser shock on a small scale is proposed. It exhibits the unique advantages of a pulsed laser, such as high strain rate and dynamic shock force, and suitable for micro-part manufacturing. The experiment on the dynamic compaction of spherical aluminum powder was completed under five different laser energies. The effects of laser energy and powder packing state on the mechanical properties of the final compact and Microstructure of the compact, including the upper, failure, and cross section surfaces, were analyzed. Results showed that the mechanical properties of the aluminum compacts gradually improved with the increase of laser energy. The nearly fully dense aluminum compacts were successfully compressed at 1800 mJ laser energy with a final relative density of 99.72%. Moreover, the Microhardness of the compacts improved by approximately 60%. The simulation results using multi-particle finite element method (MPFEM) show that with the propagation of the generated shock wave in the compact, particles had large plastic deformation that filled the pores during the laser shock dynamic compaction of aluminum powder. The simulation and experimental results show that the main connection mechanism of particles is cold welding. The dense packing of powder before compaction could considerably improve the propagation of shock waves, and the initiation and growth of inter-particle cracks were reduced.

Tuning the Energetic Performance of CL-20 by Surface Modification Using Tannic Acid and Energetic Coordination Polymers

The energetic performance of hexanitrohexaazaisowurtzitane (CL-20) was modulated with two energetic coordination polymers (ECPs), [Cu(ANQ)2(NO3)2] and [Ni(CHZ)3](ClO4)2, in this study by a two-step method. First, tannic acid polymerized in situ on the surface of CL-20 crystals. Then, [Cu(ANQ)2(NO3)2] and [Ni(CHZ)3](ClO4)2 were hydrothermally formed on the surface of CL-20/TA, respectively. Explosion performance tests show that the impact sensitivity of the coated structure CL-20/TA/[Cu(ANQ)2(NO3)2] is 58% less than that of CL-20 with no energy decrease. On the other hand, CL-20/TA/[Ni(CHZ)3](ClO4)2 can be initiated by a low laser energy of 107.3 mJ (Nd:YAG, 1064 nm, 6.5 ns pulse width), whereas CL-20 cannot be initiated by even 4000 mJ laser energy. This study shows that it is feasible to modify the performance of CL-20 by introducing energetic CPs with certain properties, like high energy insensitive, laser-sensitive, etc., which could be a prospective method for designing high energy insensitive energetic materials in the future.

Rapid fabrication of NiO/porous Si film for ultra-violate photodetector: The effect of laser energy

In this manuscript, nickel oxide (NiO)/porous silicon (Si) film was prepared using co-precipitation and pulsed laser deposition techniques for ultra-violate (UV) photodetector application. A series of UV photodetectors were fabricated using the corresponding NiO/Si film as a function of the utilized laser energy. Simultaneously, an interdependence correlation between the physical characteristics of the attained film along with the fabricated photodetectors was established. Specifically, higher crystallinity and lower optical bandgap delivered a sound photo-responsive behavior in the proposed device geometry. In details, the attained photo-responsivity was observed to be 2.7 and 3.7 μA/mWusing laser energy of 300 and 500 mJ, respectively. Concurrently, the optimum device, fabricated at 500 mJ laser energy, exhibited approximate rise and fall periods of 750 and 800 ms, respectively. In addition to the robustness and uniformity of the fabricated UV photodetector, the proposed work presents a substitutional framework for cost-effective and eco-friendly optoelectronic scheme.

Produce of Selenium Nanoparticles by Pulsed Laser Ablation for Anticancer Treatments

The most serious public health problems now involve antibiotic resistance and cancer that kills more than 15 million people per year which indicates that the existing antibiotics and chemotherapy are not as active as before. This paper provides nanotechnology as a possible answer. However, typical physicochemical nanomaterials production processes, frequently requiring the use of harmful catalysts, have environmental or social implications. This paper covers how to use the innovative liquid-pulsed laser ablation (LP-PLA) process to manufacture selenium nanoparticles (SeNPs). After the first set of radiation at 500[Formula: see text]mJ laser energy and 100 pulses, a second set was employed to decrease the size to less than 100[Formula: see text]nm with the same condition. Therefore, two main groups of 80 and 10[Formula: see text]nm had colloidal solutions for spherical SeNPs. The particles were also more stable following the second round of irradiation. Furthermore, when SeNPs were grown with human dermal fibroblast cells at doses up to 1[Formula: see text]ppm, they had a mild cytotoxic impact. The potential of utilizing totally naked SeNPs produced using the novel LP-PLA procedure as a novel and efficient way of producing nanoparticles for biomedical applications is presented in this paper.

Reducing surface roughening in microscale laser dynamic flexible bulging by using laser pre-shocking

Roughening of the free surface in micro-forming results in the local necking and subsequent fracture, which seriously affects the formability of sheet metals. In this work, laser pre-shocking (LPS) was introduced into microscale laser dynamic flexible bulging (μLDFB) to reduce surface roughening in terms of reducing the surface roughness and refining the internal grains. In LPS experiments, when the laser energy is 447 mJ, the rebound of the copper foils can be negligible. LPS can be expected to suppress the surface roughening by reducing the initial roughness R0, increasing the N value and decreasing the rate of surface roughening. The copper foils subjected by 447 mJ LPS were used for the μLDFB experiments. The 50 μm T2 copper foils with four different grain sizes were used in μLDFB under different laser pulse energies. When laser pulse energy ranges from 325 mJ to 575 mJ, compared with μLDFB without LPS, the surface roughness on the bottom surface of the bulging sample is decreased. And the nano-hardness, elastic modulus and forming uniformity are significantly improved. In μLDFB experiments without LPS, for fine-grained samples, the cracks initiate in the bulging transition zone under 725 mJ laser energy due to surface roughening. As laser energy increases to 1050 mJ, the cracks initiate in the mold entrance zone due to the strong stress concentration. For coarse-grained samples, cracks initiate under 575 mJ laser energy, and the propagations of the cracks are difficult to predict due to non-uniform distribution of grain size and the difference of grain orientation. The experimental results suggest that LPS can reduce the possibility of the premature fracture caused by the local necking, and alleviate the uncertainty in the fracture mode.

Study the effect of gamma ray on silver nanoparticles prepared by pulse laser ablation in liquid technique (PLAL)

Silver nanoparticles in this study were prepared using the method of laser ablation in liquids (PLAL) at two energies (540 and 700) mJ and the count of pulses were (100,200,300 and 400) pulse . The prepared samples were divided into three groups: the first group of the samples were kept as they are without any irradiation but the second and third group were irradiated by Co-60 source with two amount of doses (7.5 and 11) KGy respectively . A series of measurements and studies were done, and from the pictures of Transmitted Electron Microscope (TEM) , it was observed that the prepared nanoparticles at laser energy (540) mJ with pulses count (400) pulse were spherical but the prepared nanoparticles at laser (700) mJ with pulses cont (400) pulse were nano rods shape. The gamma irradiation effect was studied through its effect on the optical properties of the nanoparticles at different preparation conditions , represented by a change in the pulses and the energy of the laser used. The results showed that there was an increase the absorbance peaks when increasing the irradiated dose. The (TEM) image showed we get spherical nanoparticles in shape and nano composition. The average diameter of the prepared silver nanoparticles at (540) mJ laser energy in the range of (30-40) nm.

Empirical assessment of laser safety for photoacoustic-guided liver surgeries.

Photoacoustic imaging is a promising technique to provide guidance during multiple surgeries and procedures. One challenge with this technique is that major blood vessels in the liver are difficult to differentiate from surrounding tissue within current safety limits, which only exist for human skin and eyes. In this paper, we investigate the safety of raising this limit for liver tissue excited with a 750 nm laser wavelength and approximately 30 mJ laser energy (corresponding to approximately 150 mJ/cm2 fluence). Laparotomies were performed on six swine to empirically investigate potential laser-related liver damage. Laser energy was applied for temporal durations of 1 minute, 10 minutes, and 20 minutes. Lasered liver lobes were excised either immediately after laser application (3 swine) or six weeks after surgery (3 swine). Cell damage was assessed using liver damage blood biomarkers and histopathology analyses of 41 tissue samples total. The biomarkers were generally normal over a 6 week post-surgical in vivo study period. Histopathology revealed no cell death, although additional pathology was present (i.e., hemorrhage, inflammation, fibrosis) due to handling, sample resection, and fibrous adhesions as a result of the laparotomy. These results support a new protocol for studying laser-related liver damage, indicating the potential to raise the safety limit for liver photoacoustic imaging to approximately 150 mJ/cm2 with a laser wavelength of 750 nm and for imaging durations up to 10 minutes without causing cell death. This investigation and protocol may be applied to other tissues and extended to additional wavelengths and energies, which is overall promising for introducing new tissue-specific laser safety limits for photoacoustic-guided surgery.

Raman spectroscopic studies of ortho-xylene under laser driven shock and static compression

Ortho-xylene (o-xylene), a derivative of benzene and an important aromatic compound is applied as an anti-knocking agent in automobiles and jet engines. Knocking being a dynamical phenomenon that occurs at very high temperatures and high pressures, here we have reported the pump–probe technique based time-resolved Raman spectroscopy studies under laser-driven shock compression (high temperature and high pressure) along with the numerical simulation to understand the molecular level response of o-xylene under shock compression. The laser shock experiments carried out up to 4.1 GPa using confinement geometry target holder assembly show indication of three phase transitions, i.e., liquid–solid phase-I, solid phase-I–solid phase-II, and solid phase-II–solid phase-III at 1.2, 2.1, and 3.6 GPa, respectively. The shock velocities calculated for 700 mJ laser energy (corresponding pressure 2.5 GPa) using intensity ratios of Raman modes scattered from the shocked and whole region of the sample for 735 and 582 cm−1 Raman modes are 3.4 ± 0.3 and 3.5 ± 0.3 km/s, respectively, which is in close agreement with the shock velocity of 3.51 km/s determined using 1D radiation hydrodynamic numerical simulation. In addition, our high-pressure static compression studies on this compound employing diamond anvil cell up to 13 GPa show that this compound shows four possible phase transitions at 0.4, 0.9, 3.8, and 12 GPa pressures to solid phase I, II, III, and IV, respectively. On release, these phase transitions are reversible.