scholarly journals PALS laser energy transfer into solid targets and its dependence on the lens focal point position with respect to the target surface

2008 ◽  
Vol 26 (2) ◽  
pp. 189-196 ◽  
Author(s):  
A. Kasperczuk ◽  
T. Pisarczyk ◽  
M. Kalal ◽  
M. Martinkova ◽  
J. Ullschmied ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Laser Energy ◽  
Focal Point ◽  
Target Surface ◽  
Plasma Jets ◽  
Point Position ◽  
Laser Plasma Interactions ◽  
Opposite Case ◽  
Laser Facility ◽  
Focusing Lens

AbstractThis paper is devoted to investigations of laser energy transfer into solid targets with respect to the focusing lens focal point position relative to the solid target surface as obtained at the PALS laser facility. The third harmonic of the PALS laser beam with energy ~90 J and pulse duration ~250 ps (FWHM) was used for irradiation of two kinds of targets made of Cu: a slab and a 3.6 µm thick foil. The focal point of the beam was located either inside or in front of the target surface, and care was taken to ensure the same laser spot radii in both cases (250 µm). It was demonstrated that these two opposite focal point positions give rise to significantly different laser-plasma interactions: with either depression or maximum of the laser intensity distribution in the center of the beam, respectively. It was also verified that the focal point position inside of the target is favorable for plasma jets creation, whereas the opposite case is more effective for acceleration of flyers.

scholarly journals Interferometric investigations of influence of target irradiation on the parameters of laser-produced plasma jets

2007 ◽  
Vol 25 (3) ◽  
pp. 425-433 ◽  
Author(s):  
A. Kasperczuk ◽  
T. Pisarczyk ◽  
S. Borodziuk ◽  
J. Ullschmied ◽  
E. Krousky ◽  
...  
Keyword(s):  
Focal Spot ◽  
Laser Energy ◽  
Plasma Jet ◽  
Plasma Jets ◽  
Plasma Expansion ◽  
Third Harmonic ◽  
Fundamental Process ◽  
Laser Produced Plasma ◽  
Laser Facility ◽  
Planar Target

Our recent experimental results demonstrate that the formation of plasma jets is a fundamental process accompanying the laser produced plasma expansion, if a massive planar target with relatively high atomic number is irradiated by a defocused laser beam. In this paper some new results on the influence of target irradiation conditions on plasma jet parameters are presented. The experiment was carried out at the PALS iodine laser facility, with the third harmonic beam of the pulse duration of 250 ps (FWHM). The beam energies varied in the range of 13–160 J, the focal spot radii in the range of 35–600 µm. The planar massive targets used in the experiment were made of Cu, Ag and Ta. For measurements of the electron density evolution a three frame interferometric system was employed. The jets were observed in the whole range of the laser energy used. The initial velocities of the plasma jets produced in the reported experiment reached the value of up to 7·107 cm/s, the jets were up to 4 mm long including the jet pedestal and about 400 µm in diameter. Calculations of the efficiency of the plasma jet production show that it decreases with increasing the laser energy.

scholarly journals Interaction of two plasma jets produced successively from Cu target

2010 ◽  
Vol 28 (3) ◽  
pp. 497-504 ◽  
Author(s):  
A. Kasperczuk ◽  
T. Pisarczyk ◽  
J. Badziak ◽  
S. Borodziuk ◽  
T. Chodukowski ◽  
...  
Keyword(s):  
Laser Beam ◽  
Target Surface ◽  
Plasma Jet ◽  
Plasma Jets ◽  
Diagnostic Tools ◽  
Jet Formation ◽  
Simple Method ◽  
Third Harmonic ◽  
Laser Facility ◽  
Focal Spot Diameter

AbstractOur earlier papers demonstrate a very simple method of plasma jet formation, consisting in irradiating a massive planar target of a relatively high atomic number by a partly defocused laser beam. Our present interest is concentrated on interaction of the plasma jet with other media. This paper is aimed at investigations of interaction of two jets launched successively on Cu target. Our attention was paid to the role of radiative cooling in the plasma jet formation. The experiment was carried out at the PALS iodine laser facility. The laser provided a 250-ps (full width at half maximum) pulse with energy of 130 J at the third harmonic frequency (λ3 = 0.438 µm). Two successive jets were produced on a massive flat Cu target provided with a cylindrical channel 5 mm long and 400 µm in diameter. Since the focal spot diameter of the laser beam on the target surface was larger than that of the channel (800 µm), the annular irradiation of the target face resulted in creation of the first plasma jet, whereas the second jet was produced by action of the central part of laser beam on the channel wall. Three-frame interferometric system, X-ray streak camera, and a set of ion collectors were used as diagnostic tools.

scholarly journals Influence of the focal point position of a focusing lens on a character of an ablative plasma expansion

2008 ◽  
Vol 112 (2) ◽  
pp. 022047
Author(s):  
A Kasperczuk ◽  
T Pisarczyk ◽  
J Badziak ◽  
R Miklaszewski ◽  
P Parys ◽  
...  
Keyword(s):  
Focal Point ◽  
Plasma Expansion ◽  
Point Position ◽  
Focusing Lens

scholarly journals Three-Jet Powder Flow and Laser–Powder Interaction in Laser Melting Deposition: Modelling Versus Experimental Correlations

Metals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1113 ◽  
Author(s):  
Muhammad Arif Mahmood ◽  
Andrei C. Popescu ◽  
Mihai Oane ◽  
Carmen Ristoscu ◽  
Diana Chioibasu ◽  
...  
Keyword(s):  
Temperature Distribution ◽  
Laser Energy ◽  
Focal Point ◽  
Heating Temperature ◽  
Plasma Formation ◽  
Powder Flow ◽  
Laser Melting ◽  
Gaussian Shape ◽  
Point Position ◽  
Laser Melting Deposition

Powder flow and temperature distribution are recognized as essential factors in the laser melting deposition (LMD) process, which affect not only the layer formation but also its characteristics. In this study, two mathematical models were developed. Initially, the three-jet powder flow in the Gaussian shape was simulated for the LMD process. Next, the Gaussian powder flow was coaxially added along with the moving laser beam to investigate the effect of powder flow on temperature distribution at the substrate. The powder particles’ inflight and within melt-pool heating times were controlled to avoid vapors or plasma formation due to excessive heat. Computations were carried out via MATLAB software. A high-speed imaging camera was used to monitor the powder stream distribution, experimentally, while temperature distribution results were compared with finite element simulations and experimental analyses. A close correlation was observed among analytical computation, numerical simulations, and experimental results. An investigation was conducted to investigate the effect of the focal point position on powder stream distribution. It was found that the focal point position plays a key role in determining the shape of the powder stream, such that an increment in the distance from the focus point will gradually transform the powder stream from the Gaussian to Transition, and from the Transition to Annular streams. By raising the powder flow rate, the attenuation ratio prevails in the LMD process, hence, decreasing the laser energy density arriving at the substrate. The computations indicate that, if the particle’s heating temperature surpasses the boiling point, a strong possibility exists for vapors and plasma formation. Consequently, an excessive amount of laser energy is absorbed by the produced vapors and plasma, thus impeding the deposition process.

Energy Transfer and Molecule-Radiation Interaction in Optical Microcavities

2006 ◽  
Author(s):  
Haiyong Quan ◽  
Zhixiong (James) Guo
Keyword(s):  
Energy Transfer ◽  
Molecular Detection ◽  
Laser Energy ◽  
Maximum Energy ◽  
Whispering Gallery Modes ◽  
Optical Microcavities ◽  
Optical Wavelength ◽  
Whispering Gallery ◽  
Microcavity Devices ◽  
And Storage

Laser energy transfer and molecule-radiation interaction in optical microcavity devices are characterized. The device is operated at whispering-gallery modes, and consists of a microcavity and a micro-waveguide coupled by a sub-micrometer air-gap. Emphases are placed on the influences of microcavity size and waveguide compatibility on the energy transfer and storage capability, on the interactions of foreign molecules with the evanescent radiation field surrounding a resonant microcavity. An optimal gap is found for the considered device configuration where maximum energy storage is achieved. This optimal gap is dependent on the resonance mode as well as the morphology. The Q factor increases exponentially with increasing gap and saturates as the gap approaches the optical wavelength. The influence of molecules attachment is demonstrated and the potential in molecular detection is discussed.

Optimal fusion of multi-focus image: Integrating WNMF and focal point analysis

2021 ◽  
pp. 2150156
Author(s):  
Shi-Hong Zhang ◽  
Qi-Yuan Zhan ◽  
Wen-Yu Li ◽  
Qiong-Ze Wang
Keyword(s):  
Image Fusion ◽  
Point Spread Function ◽  
Focal Point ◽  
Nonnegative Matrix ◽  
Fusion Algorithm ◽  
Point Position ◽  
Position Analysis ◽  
Point Spread ◽  
Spread Function ◽  
Focus Image

Image fusion can be used to improve the image utilization, spatial resolution and spectral resolution, which has been widely applied on medicine, remote sensing, computer vision, weather forecast and military target recognition. The goal of image fusion is to reduce the uncertainty and redundancy of the output and increase the reliability of the image on the basis of the maximum combination of relevant information. In this paper, a multi-focus image fusion algorithm based on WNMF and Focal point position analysis is proposed to improve the image fusion method based on nonnegative matrix factorization. In the imaging process, the Gaussian function is used to approximate the point spread function in the optical system. Then calculate the difference between the original image and the approximate point spread function and get the weighted matrix [Formula: see text]. Finally, we apply the weighted nonnegative matrix algorithm to image fusion, and the new fusion image with clear parts is obtained. Experimental results show that the multi-focus image fusion algorithm based on WNMF and Focal point position analysis (MFWF) is better.

INTERACTION EFFECT BETWEEN BEAM DIAMETER AND ENERGY DENSITY IN LASER-INDUCED TACTILE PERCEPTION

2018 ◽  
Vol 18 (07) ◽  
pp. 1840011
Author(s):  
MI-HYUN CHOI ◽  
HYUNG-SIK KIM ◽  
JI-HUN JO ◽  
JI-SUN KIM ◽  
JAE-HOON JUN ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Energy Density ◽  
Penetration Depth ◽  
Interaction Effect ◽  
Laser Energy ◽  
Tactile Sensation ◽  
Beam Diameter ◽  
Effective Energy ◽  
Effective Energy Transfer ◽  
Response Phase

This study aims to investigate the interaction effect between the beam diameter and energy density, which are perceived as laser-induced tactile perception by humans, by diversely varying the laser parameters, beam diameter, and energy. Eight healthy male college students of 23.5[Formula: see text][Formula: see text][Formula: see text]1.7 years participated in the study. The range of the beam diameter of the displayed laser stimulation was between 0.03[Formula: see text]mm and 8[Formula: see text]mm, and a total of 21 sizes were displayed. The laser energy was sequentially displayed from the minimum energy that can be displayed by one beam diameter to the maximum energy range that does not exceed the maximum permissible exposure (MPE) level since the energy varies according to the beam diameter. The laser energy was controlled by an optical density ([Formula: see text]) filter and was measured by an optical power meter (energy meter). Furthermore, the beam diameter was adjusted by moving the lens, which was confirmed with the beam profiler. The experimental test consists of the control phase (19[Formula: see text]s), stimulus phase (7[Formula: see text]s), and response phase (4[Formula: see text]s); the total duration of the test was 30[Formula: see text]s. The stimulus phase is the period in which stimulation was displayed on the skin through laser irradiation, and the stimulation was displayed by changing the beam diameter and the energy from the laser. The total number of beam diameter and energy pairs displayed to the subjects was 113 and 5 trials of irradiation were conducted for each pair. Stimulation perception response was recorded by pressing the response buttons during the response phase, and the responses were predefined as “no feeling,” “tactile sensation”, and “pain.” Through the extracted response data from the response phase, the beam diameter and energy density pair in which more than 50% of the subjects responded as having perceived tactile sensation were selected from the possible laser energy that could be displayed from one beam diameter. The simulation results showed that increasing the beam diameter increased the penetration depth, indicating an effective energy transfer to the skin. Therefore, increasing the beam diameter results in increased scattering, and hence increased penetration depth, and ultimately a more effective energy transfer. Therefore, increased beam diameter results in higher energy transfer efficiency, indicating that the required energy density by more than 50% of the subjects to perceive tactile sensation decreased.

Optimization of distances between the target surface and focal point on spatially confined laser-induced breakdown spectroscopy with a cylindrical cavity

2017 ◽  
Vol 32 (2) ◽  
pp. 367-372 ◽  
Author(s):  
Jin Guo ◽  
Junfeng Shao ◽  
Tingfeng Wang ◽  
Changbin Zheng ◽  
Anmin Chen ◽  
...  
Keyword(s):  
Emission Spectroscopy ◽  
Optical Emission Spectroscopy ◽  
Focal Point ◽  
Optical Emission ◽  
Target Surface ◽  
Laser Induced Breakdown Spectroscopy ◽  
Spatial Confinement ◽  
Laser Induced Plasma ◽  
Breakdown Spectroscopy ◽  
Laser Induced Breakdown

The spatial confinement effect in laser-induced plasma with different distances between the target surface and focal point is investigated by optical emission spectroscopy.

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