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Mass separated particle flux from a laser-ablation metal cluster source
摘要： Flux waveforms of aluminum cluster beams supplied from a laser-ablation cluster source were precisely investigated under various source conditions such as background pressure, ablation laser intensity, and nozzle structure. A time-of-flight mass spectroscopy revealed that aluminum clusters with sizes up to 200 were generated and the amount of the clusters could be maximized by choosing a proper background pressure (～2 MPa) and an ablation laser fluence (～40 mJ/cm2). Flux waveforms of clusters having specific sizes were carefully reconstructed from the observed mass spectra. It is found that the pulse widths of the aluminum cluster beams were typically about 100 μs and much smaller than that of the monoatomic aluminum beam, indicating that the cluster formation was limited in a relatively small volume in the laser-ablated vapor. Introducing a conical nozzle having a large open angle was also found to enhance the cluster beam velocity and reduce its pulse width. A velocity measurement of particles in the cluster beam was conducted to examine the velocity spread of the supplied clusters. We found that the aluminum clusters were continuously released from the source for about 100 μs and this release time mainly determined the pulse width of the cluster beam, suggesting that controlling the behavior of an ablated vapor plume in the waiting room of the cluster source holds the key to drastically improving the cluster beam flux.
关键词： mass spectrometry,laser ablation,molecular beam,Cluster
更新于2025-09-12 10:27:22
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Pediatric Neurosurgery: Tricks of the Trade || 104 Laser Ablation of Deep Lesions
摘要： A major goal of neurosurgical management of many deep lesions is to safely destroy, or neutralize the consequences of, a lesion without damage to nearby structures. “Neutralization” here means to render harmless, as in cases where deep lesions cause seizures, such as hypothalamic hamartomas or lesions of the hippocampus. A stereotactic procedure that minimally disrupts other tissue and avoids the long-term effects of ionizing radiation (as with stereotactic radiosurgery [SRS]) may prove to be the strategy of choice. For the technique described in this chapter, laser interstitial thermoablative therapy (LITT), the key additional safety element is the ability to observe the anatomical boundaries and progress of the laser lesion as it is being made. Since the procedure is performed “closed” through a twist-drill hole, the visualization of the lesion is effected using real-time magnetic resonance imaging (MRI) observation of the target—and automated control of the laser to turn the power off when specific criteria are met. Many of the nuances of the procedure therefore depend on an understanding of the underlying phenomena and on the ability to interact with the stereotactic and laser control software.
关键词： Deep Lesions,Laser Ablation,Neurosurgical Management,LITT,MRI
更新于2025-09-12 10:27:22
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Carbon multicharged ions emission from femtosecond laser plume
摘要： Carbon ion emission from femtosecond laser ablation of a glassy carbon target is studied. A Ti:sapphire laser (pulse duration τ ~ 150 fs, wavelength λ = 800 nm, laser fluence F ≤ 6.4 J cm?2) is used to ablate the carbon target while ion emission is detected by a time-of-flight detector equipped with a three-grid retarding field analyzer. A strong effect of the laser pulse fluence on the yield of carbon ions is observed. Up to C6+ ions are detected. The carbon ion time-of-flight signal is fit to a shifted Maxwell-Boltzmann distribution and used to extrapolate the effective plasma ion temperature Tieff = 6.9 eV. Applying an external electric field along the plasma expansion direction increases ion extraction, possibly due to the retrograde motion of the plasma-vacuum edge.
关键词： Femtosecond laser ablation,Time-of-flight,Plasma ion temperature,Carbon multicharged ions,Shifted Maxwell-Boltzmann distribution
更新于2025-09-12 10:27:22
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Laser-assisted preparation of Pd nanoparticles on carbon cloth for the degradation of environmental pollutants in aqueous medium
摘要： Laser ablation in liquid (LAL), one of the attractive methods for fabrication of nanoparticles, was used for the modification carbon cloth (CC) by deposition of palladium nanoparticles (Pd NPs); a simple stirring method was deployed to deposit Pd NPs on the CC surface. Characterization techniques viz X-ray diffraction (XRD), Fourier transform infrared (FT-IR), scanning electron microscope (SEM), energy-dispersive X-ray spectrometry (EDS) and inductively coupled plasma atomic emission spectroscopy (ICP-AES) were applied to study the surface of the ensuing samples which confirmed that LAL technique managed to fabricate and deposit the Pd NPs on the surface of CC. In addition, the catalytic prowess of the carbon cloth-Pd NPs (CC/Pd NPs) was investigated in the NaBH4- or HCOOH-assisted reduction of assorted environmental pollutants in aqueous medium namely hexavalent chromium [Cr(VI)], 4-nitrophenol (4-NP), congo red (CR) and methylene blue (MB). The CC/Pd NPs system has advantages such as high stability/sustainability, high catalytic performance and easy reusability.
关键词： Carbon cloth-Pd NPs,Pollutant degradation,Laser ablation,Catalytic activity,Environmental treatment
更新于2025-09-12 10:27:22
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Three-Dimensional Composition Analysis of SnAg Solder Bumps Using Ultraviolet Femtosecond Laser Ablation Ionization Mass Spectrometry
摘要： The application of a novel UV fs Laser Ablation Ionization Mass Spectrometry approach for chemical depth profiling of low-melting point, high surface roughness SnAg solder bump features is presented. The obtained resolved three-dimensional compositional submicrometer data reveal unprecedented information on the distribution of individual elements inside the solder bump matrix. Moreover, the determination of matrix-matched relative sensitivity coefficients allows the first report on quantitative assessment of the SnAg alloy composition. These results significantly contribute to an in-depth understanding of the SnAg plating process. This experimental procedure may find application in future additive performance screening.
关键词： three-dimensional compositional analysis,chemical depth profiling,SnAg solder bumps,UV fs Laser Ablation Ionization Mass Spectrometry,matrix-matched relative sensitivity coefficients
更新于2025-09-12 10:27:22
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Single-Shot Multi-Stage Damage and Ablation of Silicon by Femtosecond Mid-infrared Laser Pulses
摘要： Although ultrafast laser materials processing has advanced at a breakneck pace over the last two decades, most applications have been developed with laser pulses at near-IR or visible wavelengths. Recent progress in mid-infrared (MiR) femtosecond laser source development may create novel capabilities for material processing. This is because, at high intensities required for such processing, wavelength tuning to longer wavelengths opens the pathway to a special regime of laser-solid interactions. Under these conditions, due to the λ2 scaling, the ponderomotive energy of laser-driven electrons may significantly exceed photon energy, band gap and electron affinity and can dominantly drive absorption, resulting in a paradigm shift in the traditional concepts of ultrafast laser-solid interactions. Irreversible high-intensity ultrafast MIR laser-solid interactions are of primary interest in this connection, but they have not been systematically studied so far. To address this fundamental gap, we performed a detailed experimental investigation of high-intensity ultrafast modifications of silicon by single femtosecond MiR pulses (λ = 2.7–4.2 μm). Ultrafast melting, interaction with silicon-oxide surface layer, and ablation of the oxide and crystal surfaces were ex-situ characterized by scanning electron, atomic-force, and transmission electron microscopy combined with focused ion-beam milling, electron diffractometry, and μ-Raman spectroscopy. Laser induced damage and ablation thresholds were measured as functions of laser wavelength. The traditional theoretical models did not reproduce the wavelength scaling of the damage thresholds. To address the disagreement, we discuss possible novel pathways of energy deposition driven by the ponderomotive energy and field effects characteristic of the MIR wavelength regime.
关键词： ultrafast laser,ablation,silicon,damage threshold,mid-infrared
更新于2025-09-12 10:27:22
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Laser Ablation Electrospray Ionization Time-of-Flight Mass Spectrometry for Direct Analysis of Biological Tissue
摘要： Direct analysis and identi?cation of biological tissue is signi?cant for clinical applications. In this study, porcine liver and kidney have been analyzed using laser ablation electrospray ionization time-of-?ight mass spectrometry (LAESI-TOFMS). This method showed good reproducibility for the same types of tissue and is capable of distinguishing di?erent tissue species. The margin assessment was also performed using porcine renal tissue, and the response time was less than 6 s. Furthermore, human hepatocarcinoma tissue and normal tissue were identi?ed using this method. Our results indicate that LAESI-TOFMS is a feasible approach for direct identi?cation of tumor tissue and potential for assessment of the resection margin.
关键词： Laser ablation electrospray ionization mass spectrometry,biological tissue,margin assessment,tumor identification
更新于2025-09-12 10:27:22
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Effect of Laser Ablation on Microwave Attenuation Properties of Diamond Films
摘要： Thermal conductivity is required for developing high-power microwave technology. Diamond has the highest thermal conductivity in nature. In this study, a diamond ?lm was synthesized by microwave plasma chemical deposition, and then long and short conductive graphite ?bers were introduced to the diamond ?lms by laser ablation. The permittivity of the samples in the K-band was measured using the transmission/re?ection method. The permittivity of diamond ?lms with short graphite ?bers increased. The increase in real part of permittivity can be attributed to electron polarization, and the increase in the imaginary part can be ascribed to both polarization and electrical conductivity. The diamond ?lms with long graphite ?bers exhibited a highly pronounced anisotropy for microwave. The calculation of microwave absorption shows that re?ection loss values exceeding ?10 dB can be obtained in the frequency range of 21.3–23.5 GHz when the graphite ?ber length is 0.7 mm and the sample thickness is 2.5 mm. Therefore, diamond ?lms can be developed into a microwave attenuation material with extremely high thermal conductivity.
关键词： high thermal conductivity,laser ablation,diamond ?lms,microwave attenuation,permittivity
更新于2025-09-12 10:27:22
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Endovenous Laser Ablation Combined with Stripping Technique for Large Saphenous Varicose Veins: The Selection of Operation Technique
摘要： Objective: Saphenous varicose veins can be accomplished by various operative techniques that result in stripping, ablation, or ligation of the venous reflux section. Great saphenous vein (GSV) stripping is one of the standard operations for varicose veins to eliminate reflux of the sapheno-femoral junction. The goal of any treatment regimen is to eliminate the junctional varicose reflux to control congestive dysfunction. Endovenous laser ablation (EVLA) is safe and effective with less postoperative pain, bleeding, and peripheral nerve damage than open surgery. In this study, a patient with severe progression of primary saphenous varicose veins is presented. We report the outcome of combined surgical strategy and perioperative treatment for extremely swollen varicose veins of the lower limbs to improve leg symptoms and congestion and/or promote skin ulcer healing. Materials and Methods: The subjects included 42 patients (51 limbs) who underwent EVLA with stripping. The patients comprised 24 males and 18 females, who presented a maximum GSV diameter >15 mm. The Clinical-Etiological-Anatomic-Pathophysiologic classification identified 9, 20, 9, 2, 6, and 5 limbs with C2, C3, C4a, C4b, C5, and C6, respectively, among the 42 patients. Results: EVLA was used to treat GSV with a mean length of 16.1±2.8 cm. The mean of the maximum GSV diameter was 16.8±3.2 mm (14.6–21.8 mm). The preoperative visual analog scale (VAS) score was 82.1±12.1. After operation, the VAS gradually deteriorated to 31.3±17.9 (p<0.0001), 2.8±3.6 (p<0.0001), and 1.2±1.8 (p<0.0001) in 7 days, 1 month, and 3 months, respectively. Conclusion: We obtained a satisfactory outcome from our combined strategy and perioperative treatment for extremely swollen saphenous varicose veins. This approach may show the possibility that lower saphenous varicose veins can induce cosmetic and minimally invasive ameliorated intervention to avoid late-phase incompetent perforating veins.
关键词： endovenous laser ablation,stripping,varicose vein
更新于2025-09-12 10:27:22
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Photoluminescence mechanism of phosphorene quantum dots (PQDs) produced by pulsed laser ablation in liquids
摘要： Phosphorene quantum dots (PQDs) with high photoluminescence (PL) quantum yield were fabricated through pulsed laser ablation of black phosphorus in liquids. The PL emission showed excitation wavelength-independent features due to the suf?cient passivation by oxygen-containing substituents derived from the ablation-decomposed solvent molecules. There were four peaks in the PL pro?le showing a multi-frequency PL effect, which provided a viable route to investigate the PL mechanism via the detailed structures of the PL pro?le. The two peaks at shorter wavelengths were attributed to the intrinsic PL transitions. The two peaks at longer wavelengths were assigned to the transitions from the lowest unoccupied molecular orbital to the two-surface states. The positions of the four peaks are redshifted with increasing solvent molecular chain length due to the passivation effect. The intense, excitation wavelength-independent, multifrequency and blue-violet PL emissions indicate the potential application in semiconductor light sources.
关键词： semiconductor light sources,pulsed laser ablation,photoluminescence,phosphorene quantum dots
更新于2025-09-12 10:27:22