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Electronic parametric instabilities of an ultrarelativistic laser pulse in a plasma
摘要： Electronic parametric instabilities of an ultrarelativistic circularly polarized laser pulse propagating in underdense plasmas are studied by numerically solving the dispersion relation which includes the effect of the radiation reaction force in laser-driven plasma dynamics. Emphasis is placed on studying the different modes in the laser-plasma system and identifying the absolute and convective nature of the unstable modes in a parameter map spanned by the normalized laser vector potential and the plasma density. Implications for the ultraintense laser-plasma experiments are pointed out.
关键词： radiation reaction force,electronic parametric instabilities,laser-plasma system,plasma,ultrarelativistic laser pulse
更新于2025-09-23 15:21:01
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Investigation on the effects of laser parameters on the plasma profile of copper using picosecond laser induced plasma spectroscopy
摘要： Laser induced plasma generation and characterization, affected by laser parameters and sample physical properties, represent important phenomena in many fields of applications. In this work, we present new studies on the effects of an appropriate combination of laser wavelengths and pulse energies on the generated plasma characterization using a single shot picosecond Nd:YAG laser. The plasma plume of a pure copper sample has been generated by laser induced plasma spectroscopy (LIPS) using a single shot 170 ps laser pulse with wavelengths (266, 355, 532 and 1064 nm) and varying laser fluence (10–41 J/cm2). The spectral intensities of Cu I 324.75, 327.39, 515.32 and 521.82 nm have been observed. The plasma electron temperature and density have been determined from the Boltzmann plots and Stark-broadening profiles of the plasma spectral lines, respectively, assuming the local thermodynamic equilibrium (LTE) condition. It has been found that the electron temperature and electron density values increase from around 10,000 to 20,000 K and around 2 × 1017 to 1.5 × 1018 cm?3, respectively, with the increase in the laser wavelength and pulse fluence gradually. These observations can be understood due to the variations of mass-ablation rates, inverse-Bremsstrahlung, and photo-ionization with the studied pulse wavelength and pulse energy. The obtained results explore the opportunity to control specific generated plasma parameters by applying proper picosecond pulse parameters which can be considered in many fields of material science spectroscopic analysis and control the plasma interaction dynamics.
关键词： Stark-broadening,Picosecond,Boltzmann plot,Electron temperature,LTE,Laser induced plasma spectroscopy,Copper,Electron density,Plasma plume,LIPS
更新于2025-09-23 15:21:01
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Diagnosis of copper plasma by laser induced breakdown spectroscopy
摘要： In this paper influence of laser energy on the emission spectrum of laser copper-interaction and plasma parameter for plasma Copper by used a first harmonic generated wavelength of Nd:YAG exaction source. The metal plasma that had detection by HR4000 detection system (ocean optics) was use to different excited. plasma temperature via the Boltzmann plot diagram with measuring the electron density number by McWhirter CRITERION. Values of measuring (Ne), (Te) found between (61178776 K°) and (Ne) is (1.77*1015, 2.01*1015 cm-3) at 1064nm.
关键词： LIBS,Copper plasma,electron number density,self-absorption,plasma parameter
更新于2025-09-23 15:21:01
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A new technique for the treatment of nasal telangiectasia using atmospheric plasma (voltaic arc dermabrasion): Postoperative pain assessment by thermal infrared imaging
摘要： Background: Nasal telangiectasias are superficial, small vessels in the ala nasi and nasolabial crease with a varying origin. They represent an unaesthetic condition, frustrating patients who frequently request their removal. Microsclerotherapy, electrosurgery, different types of laser therapy, needle-assisted electrocoagulation, and TRASER therapy have been described for treating this condition. Aims: The aim of this study is to describe a novel technique that removes nasal telengectiasias using voltaic arc dermabrasion (VAD). Patients/Methods: Voltaic arc dermabrasion treatment was used to remove nasal telangiectasia in 23 patients. The post-treatment condition was monitored by means of photographic records and the evaluation of erythema, pain score, patient and surgeon satisfaction, and skin temperature. The timing points were 1, 4, 6 days and 1 year after treatment. Results: Patients referred a moderate pain during the treatment that ceased at the end of the procedure. Moderate erythema and punctiform fine crusting were present in all patients that lasted until the 6th day after treatment. No other adverse effects were observed. After 1-year, the mean patient and surgeon satisfaction scores were 2.90 and 3.00 ± 0.3, respectively. A single treatment was effective in 85% of the patients and no recurrences were recorded for one year. The skin temperature increased about 18.2 ± 3.2°C during the treatment but returned to basal values in about 20 seconds in most of the patients. Conclusion: Voltaic arc dermabrasion treatment is a viable, easy to use, and inexpensive tool for successful nasal telangiectasia removal, with minimal post-treatment discomfort.
关键词： nasal telangiectasia,plasma,voltaic arc dermabrasion,atmospheric plasma
更新于2025-09-23 15:21:01
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Silicon wafer etching by pulsed high-power inductively coupled Ar/CF <sub/>4</sub> plasma with 150 kHz band frequency
摘要： A silicon wafer etching using a burst pulse high-power inductively coupled plasma (ICP) is investigated. A 200 μs wide burst of a 157 kHz power supply is employed to generate ICP with a repetition rate of 50 Hz. A rectangular pulsed voltage synchronized with the burst power supply is applied upto 1 kV at the wafer. Mixed gas of argon (Ar) and tetrafluoromethane (CF4) is supplied into the vacuum chamber. The plasma density and electron temperature are 1019 m?3 and 2.8 eV where the wafer is, respectively. In the case of Ar plasma, the silicon etching rate is 0.01 μm min?1 with 1000 V negative bias. The etching rate increases to 0.23 μm min?1 by adding CF4 into Ar and increases linearly with increasing the bias voltage. The target current and emission intensity of Ar+ and F* are depended on bias voltage from ?300 to ?1000 V. The etching rate sharply increases by increasing CF4 content from 0% to 10%, and it becomes almost constant at 10%. The dependency of emission intensity of F* on CF4 content is similar to the dependency the etching rate.
关键词： Ar/CF4 plasma,high-power inductively coupled plasma,silicon wafer etching,150 kHz band frequency
更新于2025-09-23 15:21:01
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Laser-heated capillary discharge plasma waveguides for electron acceleration to 8 GeV
摘要： A plasma channel created by the combination of a capillary discharge and inverse Bremsstrahlung laser heating enabled the generation of electron bunches with energy up to 7.8 GeV in a laser-driven plasma accelerator. The capillary discharge created an initial plasma channel and was used to tune the plasma temperature, which optimized laser heating. Although optimized colder initial plasma temperatures reduced the ionization degree, subsequent ionization from the heater pulse created a fully ionized plasma on-axis. The heater pulse duration was chosen to be longer than the hydrodynamic timescale of ~1 ns, such that later temporal slices were more efficiently guided by the channel created by the front of the pulse. Simulations are presented which show that this thermal self-guiding of the heater pulse enabled channel formation over 20 cm. The post-heated channel had lower on-axis density and increased focusing strength compared to relying on the discharge alone, which allowed for guiding of relativistically intense laser pulses with a peak power of 0.85 PW and wakefield acceleration over 15 diffraction lengths. Electrons were injected into the wake in multiple buckets and times, leading to several electron bunches with different peak energies. To create single electron bunches with low energy spread, experiments using localized ionization injection inside a capillary discharge waveguide were performed. A single injected bunch with energy 1.6 GeV, charge 38 pC, divergence 1 mrad, and relative energy spread below 2% full-width half-maximum was produced in a 3.3 cm-long capillary discharge waveguide. This development shows promise for mitigation of energy spread and future high efficiency staged acceleration experiments.
关键词： capillary discharge,inverse Bremsstrahlung laser heating,electron acceleration,laser-driven plasma accelerator,plasma channel
更新于2025-09-23 15:21:01
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Insights into the Role of Plasma in Atmospheric Pressure Chemical Vapor Deposition of Titanium Dioxide Thin Films
摘要： In this work, the effect of plasma on the chemistry and morphology of coatings deposited by Atmospheric Pressure Plasma Enhanced Chemical Vapor Deposition (AP-PECVD) is investigated. To do so, plasma deposited amorphous titanium dioxide (TiO2) thin films are compared to thin films deposited using Atmospheric Pressure Chemical Vapor Deposition (AP-CVD) not involving the use of plasma. We focus here on the effect and the interest of plasma in the AP-PECVD process over AP-CVD for low substrate temperature deposition. The advantages of AP-PECVD over AP-CVD are often suggested in many articles however no direct evidence of the role of the plasma for TiO2 deposition at atmospheric pressure was reported. Hence, herein, the deposition via both methods is directly compared by depositing coatings with and without plasma using the same CVD reactor. Through the control of the plasma parameters, we are able to form low carbon coatings at low temperature with a deposition rate twice faster than AP-CVD, clearly showing the interest of plasma. Plasma enhanced methods are promising for the deposition of coatings at industrial scale over large surface and at high rate.
关键词： AP-PECVD,TiO2 thin films,Atmospheric Pressure Chemical Vapor Deposition,Atmospheric Pressure Plasma Enhanced Chemical Vapor Deposition,plasma,AP-CVD,low substrate temperature deposition
更新于2025-09-23 15:21:01
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Control of electron beam energy-spread by beam loading effects in a laser-plasma accelerator
摘要： We present experimental results from a laser wakefield electron accelerator driven by 70 TW ultrashort laser pulses in Helium and Helium–Nitrogen gaseous plasmas with two different Nitrogen concentrations, showing distinct electron-beam qualities. In order to get a clear view of the involved phenomenon, two-dimensional particle-in-cell simulations are performed which not only agreed with the experimental results but also provided an investigation on the evolution of accelerating structures. The experimental and simulation results depict that the beam loading effect can strongly modify the longitudinal accelerating electric field of the wake wave, imposing diametrically opposite effects on the final electron-beam qualities, especially the energy-spread, in the Helium–Nitrogen gas mixtures with different Nitrogen concentrations. In the Helium–Nitrogen-mixed plasma with a lower Nitrogen concentration (0.5%), if appropriately controlled, the beam loading effect can be employed to flatten the accelerating electric field for reducing the electron-beam energy spread. In contrast, in the Helium–Nitrogen-mixed plasmas with a higher Nitrogen concentration (5%), the accelerating electric field of the wake is locally reversed by the self-fields of the overloaded electron bunch, and the correspondingly generated negative-slope region of electric field increases the electron-beam energy-spread.
关键词： experimental laser plasma acceleration,ionization injection,laser wakefield acceleration
更新于2025-09-23 15:21:01
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Enhancement of THz Generation by Two-Color TW Laser Pulses in a Low-Pressure Gas
摘要： We identify experimental conditions for efficient generation of THz pulses by high power near IR laser radiation: 2 TW, 30 fs, 800-nm laser pulses with their second harmonic were slightly focused in a low-pressure gas cell in such a way to avoid multiple filamentation and excessive ionization. This two-color scheme yields a microjoule level of THz pulses which is two orders of magnitude higher than the signal generated in the atmosphere of ambient air.
关键词： THz,Two-color,Plasma absorption,Terawatt,Chirp,Filament,Low pressure,Saturation
更新于2025-09-23 15:21:01
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Analysis of alloy and solar cells with double-pulse calibration-free laser-induced breakdown spectroscopy
摘要： We applied variant of calibration free laser induced Breakdown Spectroscopy (CF-LIBS) approach for the compositional analysis of standard Gd/Ge/Si alloy and solar cells. The double pulse laser induced plasma was produced on the sample surface and the emission spectra were recorded at optimized interpulse delay and energy ratio. The Plasma temperature, determined using Boltzmann plot, was used to determine the concentration of all species present in a sample. The results are compared with reference values as well as conventional CF-LIBS results, which show that conventional and variant CF-LIBS results are similar and in close agreement to reference values. It is worth mention that the variant CF-LIBS results, but the approach is simpler and faster. Therefore, this approach was applied to three unknown polycrystalline silicon solar cells, which yield Al, C, Ca, Fe, In, Ti, Sb and Sn in the parts per million (ppm). This approach can potentially be applied for real-time trace monitoring in manufacturing processes of photovoltaic devices where conversion e?ciency depends strongly on impurities’ concentration.
关键词： Alloy and solar cells,Double pulse LIBS,Laser induced plasmas,Quantitative elemental analysis,Calibration free LIBS,Plasma parameters
更新于2025-09-23 15:21:01