Shadowgraph of Pulse CO2 Laser Induced Breakdown in Different Pressure Air

2014 ◽  
Vol 887-888 ◽  
pp. 1001-1004 ◽  
Author(s):  
Yu Zhang ◽  
Duan Yong Li ◽  
Tao Wu
Keyword(s):  
Shock Wave ◽  
Delay Time ◽  
High Speed ◽  
Laser Energy ◽  
Early Stage ◽  
Propagation Speed ◽  
Air Pressure ◽  
Incident Laser ◽  
Incident Laser Energy ◽  
Laser Induced Breakdown

The expansion property of an infrared CO2 laser produced air plasma is characterized using a high-speed imaging shadowgraph technique. The shadowgraphs were taken by a time-gated intensified charge-coupled device at various delay times after single pulses induced gas breakdown. We examined five incident laser energy of 180, 240, 345, 420 and 600 mJ induced air breakdown at the pressure of atmospheric and 104 Pa. A shock wave produced by laser induced breakdown was also observed and its speed was measured as a function delay time between the breakdown and the shadow imaging under different air pressure. The experimental results indicated that the radial and axial shock wave front evolutions showed similar behavior, which increased fast with delay time at early stage and slowly at later stage. The propagation speed of the wavefront was about 2 cm/μs at the initial stage of breakdown, and then decreased very quickly. The propagation speed under low air pressure was higher than that of gases under high pressure and the spark sustained less time at lower pressure. The size of laser induced air spark increased with incident laser energy but not simple linear relationships.

scholarly journals Effect of Cu(NO3)2 and Cu(CH3COO)2 Activating Additives on Combustion Characteristics of Anthracite and Its Semi-Coke

Energies ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5926
Author(s):  
Kirill Larionov ◽  
Konstantin Slyusarskiy ◽  
Svyatoslav Tsibulskiy ◽  
Anton Tolokolnikov ◽  
Ilya Mishakov ◽  
...  
Keyword(s):  
Ignition Delay ◽  
Delay Time ◽  
High Speed ◽  
Ignition Delay Time ◽  
Early Stage ◽  
Copper Acetate ◽  
Gas Analysis ◽  
Copper Salts ◽  
Activating Additives ◽  
On Line

The process of anthracite and its semi-coke combustion in the presence of 5 wt.% (in terms of dry salt) additives of copper salts Cu(NO3)2 and Cu(CH3COO)2 was studied. The activating additives were introduced by an incipient wetness procedure. The ignition and combustion parameters for coal samples were examined in the combustion chamber at the heating medium temperatures (Tg) of 600–800 °C. The composition of the gaseous combustion products was controlled using an on-line gas analyzer. The fuel modification with copper salts was found to reduce the ignition delay time on average, along with a drop in the minimum ignition temperature Tmin by 138–277 °C. With an increase in Tg temperature, a significant reduction in the ignition delay time for the anthracite and semi-coke samples (by a factor of 6.7) was observed. The maximum difference in the ignition delay time between the original and modified samples of anthracite (ΔTi = 5.5 s) and semi-coke (ΔTi = 5.4 s) was recorded at a Tg temperature of 600 °C in the case of Cu(CH3COO)2. The emergence of micro-explosions was detected at an early stage of combustion via high-speed video imaging for samples modified by copper acetate. According to the on-line gas analysis data, the addition of copper salts permits one to reduce the volume of CO formed by 40% on average, providing complete oxidation of the fuel to CO2. It was shown that the introduction of additives promoted the reduction in the NOx emissions during the combustion of the anthracite and semi-coke samples.

Laser Assisted E-Beam Epitaxial Growth of Si/Ge Alloys on Si

1990 ◽  
Vol 202 ◽  
Author(s):  
Paul Martin Smith ◽  
S. Lombardo ◽  
M.J. Uttormark ◽  
Stephen J. Cook ◽  
Michael O. Thompson
Keyword(s):  
Film Thickness ◽  
Epitaxial Growth ◽  
Room Temperature ◽  
Laser Energy ◽  
Incident Laser ◽  
Fine Grained ◽  
Surface Mobility ◽  
Incident Laser Energy ◽  
Enhanced Surface ◽  
Xecl Excimer Laser

ABSTRACTA novel laser-assisted technique for e-beam epitaxial growth of GexSi1−x alloys on <100> Si has been investigated. During deposition, a XeCl excimer laser is used to either heat, or to melt and crystallize, the GexSi1−x continuously as the material is evaporated. This process of heating or melting and crystallizing can be continued until the desired film thickness is achieved. At incident laser energy densities which produce melt, the underlying crystalline seed ensures epitaxial growth during the subsequent solidification. Depositions of films up to 3 at.% Ge under this liquid regime, with substrates held nominally at room temperature, exhibited complete epitaxial growth. At energy densities below the melt threshold, enhanced surface mobility for epitaxial alignment is required. Depositions in this regime exhibit only partial epitaxial growth with conversion to fine grained polycrystalline growth after short distances.

The effect of incident laser energy on pulsed laser deposition of HgCdTe films

2009 ◽  
Vol 311 (4) ◽  
pp. 1087-1090 ◽  
Author(s):  
Mei Liu ◽  
Baoyuan Man ◽  
Xingchao Lin ◽  
Xiangyang Li
Keyword(s):  
Pulsed Laser Deposition ◽  
Laser Energy ◽  
Pulsed Laser ◽  
Laser Deposition ◽  
Incident Laser ◽  
Incident Laser Energy

Raman Spectroscopy on Individual Identified Carbon Nanotubes

2012 ◽  
Vol 1407 ◽  
Author(s):  
R. Parret ◽  
D. Levshov ◽  
T. X. Than ◽  
D. Nakabayashi ◽  
T. Michel ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Laser Energy ◽  
Low Frequency ◽  
Radial Breathing Mode ◽  
Incident Laser ◽  
Mechanical Coupling ◽  
Incident Laser Energy ◽  
Double Walled Carbon Nanotubes ◽  
Walled Carbon Nanotubes

ABSTRACTIn this paper, we discuss the low-frequency range of the Raman spectrum of individual suspended index-identified single-walled (SWCNTs) and double-walled carbon nanotubes (DWCNTs). In SWCNTs, the role of environment on the radial breathing mode (RBM) frequency is discussed. We show that the interaction between the surrounding air and the nanotube does not induce a RBM upshift. In several DWCNTs, we evidence that the low-frequency modes cannot be connected to the RBM of each related layer. We discuss this result in terms of mechanical coupling between the layers which results in collective radial breathing-like modes. The mechanical coupling qualitatively explains the observation of Raman lines of radial breathing-like modes, whenever only one of the layers is in resonance with the incident laser energy.

Experimental investigation on spark ignition of linear combustor at low pressure conditions

2021 ◽  
pp. 095765092110131
Author(s):  
Kaixing Wang ◽  
Fuqiang Liu ◽  
Haitao Lu ◽  
Jinhu Yang ◽  
Qianpeng Zhao ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Flame Propagation ◽  
Ignition Delay ◽  
High Speed ◽  
Equivalence Ratio ◽  
Early Stage ◽  
Lower Boundary ◽  
Low Pressure ◽  
Air Pressure ◽  
Ignition Process

In order to explore the influence of low pressure on ignition process, the ignition performance of a linear combustor with five burners was experimentally investigated at ambient temperature and low pressure. At air pressure drops of 1%, 2% and 3%, the influence of low pressure on the lower boundary of the ignition equivalence ratio and ignition delay have been carried, and the high-speed camera was used to record the flame propagation at various time. The results indicate that the minimum ignition equivalence ratio increases with the decrease of pressure. And, the lower the pressure, the more obvious the influence of pressure on the ignition boundary. At the same air pressure, the minimum ignition equivalent ratio decreases with the increase of the air pressure drop. For the process of ignition delay, the air pressure mainly affects the evaporation of droplets and the chemical delay process, and the air pressure drop mainly affects the physical delay stage. For the process of flame propagation, the flame moves between adjacent burners in a symmetrical pattern under various pressures. The air pressure mainly affects the ignition delay process, and the air pressure drop influences the ignition delay and the flame propagation in the early stage (the light-around from single burner to three-burners). The time needed to achieve stable combustion is the shortest at the air pressure drop of 2%.

scholarly journals Analysis of Pollution in High Voltage Insulators via Laser-Induced Breakdown Spectroscopy

Molecules ◽  
2020 ◽  
Vol 25 (4) ◽  
pp. 822 ◽  
Author(s):  
Xinwei Wang ◽  
Shan Lu ◽  
Tianzheng Wang ◽  
Xinran Qin ◽  
Xilin Wang ◽  
...  
Keyword(s):  
High Voltage ◽  
Delay Time ◽  
Energy Intensity ◽  
Laser Energy ◽  
Spectral Characteristics ◽  
Laser Induced Breakdown Spectroscopy ◽  
Breakdown Spectroscopy ◽  
Laser Induced Breakdown ◽  
Pollution Detection ◽  
Deposit Density

Surface pollution deposition in a high voltage surface can reduce the surface flashover voltage, which is considered to be a serious accident in the transmission of electric power for the high conductivity of pollution in wet weather, such as rain or fog. Accordingly, a rapid and accurate online pollution detection method is of great importance for monitoring the safe status of transmission lines. Usually, to detect the equivalent salt deposit density (ESDD) and non-soluble deposit density (NSDD), the pollution should be collected when power cut off and bring back to lab, time-consuming, low accuracy and unable to meet the online detection. Laser-induced breakdown spectroscopy (LIBS) shows the highest potential for achieving online pollution detection, but its application in high voltage electrical engineering has only just begun to be examined. In this study, a LIBS method for quantitatively detecting the compositions of pollutions on the insulators was investigated, and the spectral characteristics of a natural pollution sample were examined. The energy spectra and LIBS analysis results were compared. LIBS was shown to detect pollution elements that were not detected by conventional energy spectroscopy and had an improved capacity to determine pollution composition. Furthermore, the effects of parameters, such as laser energy intensity and delay time, were investigated for artificial pollutions. Increasing the laser energy intensity and selecting a suitable delay time could enhance the precision and relative spectral intensities of the elements. Additionally, reducing the particle size and increasing the density achieved the same results.

scholarly journals Numerical modeling of quantum beam generation from ultra-intense laser-matter interactions

2015 ◽  
Vol 33 (2) ◽  
pp. 151-155 ◽  
Author(s):  
Tatsufumi Nakamura ◽  
Takehito Hayakawa
Keyword(s):  
Energy Transport ◽  
Laser Energy ◽  
Radiation Reaction ◽  
High Energy ◽  
Intense Laser ◽  
Incident Laser ◽  
Particle In Cell ◽  
Transport Code ◽  
Incident Laser Energy ◽  
Good Agreement

AbstractWhen intense laser beams interact with solid targets, high-energy photons are effectively generated via radiation reaction effect. These photons receive a large portion of the incident laser energy, and the energy transport by photons through the target is crucial for the understanding of the laser–matter interactions. In order to understand the energy transport, we newly developed a Particle-in-Cell code which includes the photon–matter interactions by introducing photon macro-particles. Test simulations are performed and compared with simulations using a particle transport code, which shows a good agreement.

Angular Distribution and Ion Time of Flight Produced on Silicon Target by Laser Irradiation

2011 ◽  
Vol 227 ◽  
pp. 31-34
Author(s):  
Yasmina Belaroussi ◽  
Tahar Kerdja ◽  
Smail Malek
Keyword(s):  
Angular Distribution ◽  
Laser Energy ◽  
Angular Distributions ◽  
Physical Processes ◽  
Incident Laser ◽  
Ion Energy ◽  
Incident Laser Energy ◽  
Silicon Target ◽  
The Mean

The growth of thin films by laser ablation involves very complex physical processes. The quality of the layer and stoechiometry of the deposits depend on key parameters like the ion energy and their angular distribution. The evolution of ions number and energy, and the angular distributions in regards to the incident laser energy, have been studied by the mean of a charges collector. We present the polar diagrams of energy and number of ions collected by irradiating a silicon target using an excimer laser at different energies.

scholarly journals X-ray emission from laser-irradiated gold targets with surface modulation

2001 ◽  
Vol 19 (2) ◽  
pp. 241-247 ◽  
Author(s):  
T. DESAI ◽  
H. DAIDO ◽  
M. SUZUKI ◽  
N. SAKAYA ◽  
A.R. GUERREIRO ◽  
...  
Keyword(s):  
Laser Energy ◽  
Emission Spectra ◽  
Plasma Confinement ◽  
Incident Laser ◽  
Experimental Conditions ◽  
Groove Surface ◽  
X Ray ◽  
Incident Laser Energy ◽  
Surface Modulation ◽  
Planar Target

X-ray emission spectra in the 5–22 nm range were recorded from planar and structured (meshlike groove surface) gold targets at 45° and 90° to the laser axis. A laser beam of 10-ns duration with EL ≤ 700 mJ and 1.06-μm wavelength was used for the experiment. Experimental results indicate an enhanced X-ray yield from a structured target as compared to a planar target under identical experimental conditions. Increased X-ray emission is attributed to plasma confinement and the possibility of conversion of kinetic energy into localized thermal energy of the plasma. Results are analyzed explicitly on the incident laser energy.

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