scholarly journals Upper-limit power for self-guided propagation of intense lasers in underdense plasma

2013 ◽  
Vol 1 (2) ◽  
pp. 74-79 ◽  
Author(s):  
Wei-Min Wang ◽  
Zheng-Ming Sheng ◽  
Yu-Tong Li ◽  
Jie Zhang
Keyword(s):  
Lower Limit ◽  
Critical Power ◽  
Spot Size ◽  
Laser Spot Size ◽  
Particle In Cell ◽  
Upper Limit ◽  
Power Set ◽  
Guided Propagation ◽  
Underdense Plasma ◽  
Limit Power

AbstractIt is found that there is an upper-limit critical power for self-guided propagation of intense lasers in plasma in addition to the well-known lower-limit critical power set by the relativistic effect. Above this upper-limit critical power, the laser pulse experiences defocusing due to expulsion of local plasma electrons by the transverse ponderomotive force. Associated with the upper-limit power, a lower-limit critical plasma density is also found for a given laser spot size, below which self-focusing does not occur for any laser power. Both the upper-limit power and the lower-limit density are derived theoretically and verified by two-dimensional particle-in-cell simulations. The present study provides new guidance for experimental designs, where self-guided propagation of lasers is essential.

scholarly journals Upper-limit power for self-guided propagation of intense lasers in underdense plasma – CORRIGENDUM

2013 ◽  
Vol 1 (3-4) ◽  
pp. 148-148
Author(s):  
Wei-Min Wang ◽  
Zheng-Ming Sheng ◽  
Yu-Tong Li ◽  
Jie Zhang
Keyword(s):  
Upper Limit ◽  
Guided Propagation ◽  
Underdense Plasma ◽  
Limit Power

scholarly journals Escaping Electrons from Intense Laser-Solid Interactions as a Function of Laser Spot Size

2018 ◽  
Vol 167 ◽  
pp. 02001 ◽  
Author(s):  
Dean Rusby ◽  
Ross Gray ◽  
Nick Butler ◽  
Rachel Dance ◽  
Graeme Scott ◽  
...  
Keyword(s):  
Rear Surface ◽  
Spot Size ◽  
Intense Laser ◽  
Laser Spot Size ◽  
Particle In Cell ◽  
High Intensity Laser ◽  
Electric Potentials ◽  
Initial Interaction ◽  
Intensity Laser ◽  
Laser Solid Interactions

The interaction of a high-intensity laser with a solid target produces an energetic distribution of electrons that pass into the target. These electrons reach the rear surface of the target creating strong electric potentials that act to restrict the further escape of additional electrons. The measurement of the angle, flux and spectra of the electrons that do escape gives insights to the initial interaction. Here, the escaping electrons have been measured using a differentially filtered image plate stack, from interactions with intensities from mid 1020-1017 W/cm2, where the intensity has been reduced by defocussing to increase the size of the focal spot. An increase in electron flux is initially observed as the intensity is reduced from 4x1020 to 6x1018 W/cm2. The temperature of the electron distribution is also measured and found to be relatively constant. 2D particle-in-cell modelling is used to demonstrate the importance of pre-plasma conditions in understanding these observations.

Upper limit power for self-guided propagation of intense lasers in plasma

2012 ◽  
Vol 101 (18) ◽  
pp. 184104 ◽  
Author(s):  
Wei-Min Wang ◽  
Zheng-Ming Sheng ◽  
Ming Zeng ◽  
Yue Liu ◽  
Zhi-Dan Hu ◽  
...  
Keyword(s):  
Upper Limit ◽  
Guided Propagation ◽  
Limit Power

Modelling of the laser spot size dependence of retinal thermal damage

2005 ◽  
Author(s):  
Karl Schulmeister ◽  
Bernhard Seiser ◽  
Florian Edthofer ◽  
David J. Lund
Keyword(s):  
Size Dependence ◽  
Thermal Damage ◽  
Spot Size ◽  
Laser Spot ◽  
Laser Spot Size

PNN and BP Neural Network Fault Diagnosis Research on Electronic Accelerator Pedal Detection

2020 ◽  
Vol 14 (2) ◽  
pp. 205-220
Author(s):  
Yuxiu Jiang ◽  
Xiaohuan Zhao
Keyword(s):  
Neural Network ◽  
Fault Diagnosis ◽  
Fault Detection ◽  
Lower Limit ◽  
Bp Neural Network ◽  
Accelerator Pedal ◽  
Electronic Throttle ◽  
Measured Voltage ◽  
Upper Limit ◽  
Network Fault

Background: The working state of electronic accelerator pedal directly affects the safety of vehicles and drivers. Effective fault detection and judgment for the working state of the accelerator pedal can prevent accidents. Methods: Aiming at different working conditions of electronic accelerator pedal, this paper used PNN and BP diagnosis model to detect the state of electronic accelerator pedal according to the principle and characteristics of PNN and BP neural network. The fault diagnosis test experiment of electronic accelerator pedal was carried out to get the data acquisition. Results: After the patents for electronic accelerator pedals are queried and used, the first measured voltage, the upper limit of first voltage, the first voltage lower limit, the second measured voltage, the upper limit of second voltage and the second voltage lower limit are tested to build up the data samples. Then the PNN and BP fault diagnosis models of electronic accelerator pedal are established. Six fault samples are defined through the design of electronic accelerator pedal fault classifier and the fault diagnosis processes are executed to test. Conclusion: The fault diagnosis results were analyzed and the comparisons between the PNN and the BP research results show that BP neural network is an effective method for fault detection of electronic throttle pedal, which is obviously superior to PNN neural network based on the experiment data.

scholarly journals Geometric particle-in-cell methods for the Vlasov–Maxwell equations with spin effects

2021 ◽  
Vol 87 (3) ◽  
Author(s):  
Nicolas Crouseilles ◽  
Paul-Antoine Hervieux ◽  
Yingzhe Li ◽  
Giovanni Manfredi ◽  
Yajuan Sun
Keyword(s):  
Phase Space ◽  
Maxwell Equations ◽  
Stimulated Raman Scattering ◽  
Extended Phase ◽  
Five Dimensions ◽  
Particle In Cell ◽  
Spin Effects ◽  
Dimensional Phase Space ◽  
Spin Polarized ◽  
Underdense Plasma

We propose a numerical scheme to solve the semiclassical Vlasov–Maxwell equations for electrons with spin. The electron gas is described by a distribution function $f(t,{\boldsymbol x},{{{\boldsymbol p}}}, {\boldsymbol s})$ that evolves in an extended 9-dimensional phase space $({\boldsymbol x},{{{\boldsymbol p}}}, {\boldsymbol s})$ , where $\boldsymbol s$ represents the spin vector. Using suitable approximations and symmetries, the extended phase space can be reduced to five dimensions: $(x,{{p_x}}, {\boldsymbol s})$ . It can be shown that the spin Vlasov–Maxwell equations enjoy a Hamiltonian structure that motivates the use of the recently developed geometric particle-in-cell (PIC) methods. Here, the geometric PIC approach is generalized to the case of electrons with spin. Total energy conservation is very well satisfied, with a relative error below $0.05\,\%$ . As a relevant example, we study the stimulated Raman scattering of an electromagnetic wave interacting with an underdense plasma, where the electrons are partially or fully spin polarized. It is shown that the Raman instability is very effective in destroying the electron polarization.

scholarly journals Long lifetime of bialkali photocathodes operating in high gradient superconducting radio frequency gun

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
E. Wang ◽  
V. N. Litvinenko ◽  
I. Pinayev ◽  
M. Gaowei ◽  
J. Skaritka ◽  
...  
Keyword(s):  
Radio Frequency ◽  
Electron Beams ◽  
Spot Size ◽  
Laser Spot ◽  
Laser Spot Size ◽  
High Quantum Efficiency ◽  
High Brightness ◽  
High Charge ◽  
Superconducting Radio Frequency ◽  
Long Lifetime

AbstractHigh brightness, high charge electron beams are critical for a number of advanced accelerator applications. The initial emittance of the electron beam, which is determined by the mean transverse energy (MTE) and laser spot size, is one of the most important parameters determining the beam quality. The bialkali photocathodes illuminated by a visible laser have the advantages of high quantum efficiency (QE) and low MTE. Furthermore, Superconducting Radio Frequency (SRF) guns can operate in the continuous wave (CW) mode at high accelerating gradients, e.g. with significant reduction of the laser spot size at the photocathode. Combining the bialkali photocathode with the SRF gun enables generation of high charge, high brightness, and possibly high average current electron beams. However, integrating the high QE semiconductor photocathode into the SRF guns has been challenging. In this article, we report on the development of bialkali photocathodes for successful operation in the SRF gun with months-long lifetime while delivering CW beams with nano-coulomb charge per bunch. This achievement opens a new era for high charge, high brightness CW electron beams.

The Excavation of Eighteen Round Barrows near Shrewton, Wiltshire.

1984 ◽  
Vol 50 ◽  
pp. 255-318 ◽  
Author(s):  
Charles Green ◽  
Stephen Rollo-Smith ◽  
Elisabeth Crowfoot ◽  
Calvin Wells
Keyword(s):  
Water Supply ◽  
Lower Limit ◽  
Open Water ◽  
Linear Groups ◽  
Upper Limit ◽  
The Village

The excavation of eighteen round barrows was undertaken by the late Charles Green during summer seasons from 1958 to 1960, in advance of their destruction by ploughing. The excavated barrows are members of two linear groups which occupy adjacent spurs to the east of the village of Shrewton in the modern parish of that name (fig. 1). One of the barrows investigated lies in Winterbourne Stoke parish. This western part of Salisbury Plain is termed the ‘Lower Plain’ comprising those areas having their ‘upper limit… between 400 and 450 feet OD and their lower limit where they overlook the valley trenches … between 250 and 300 feet O.D.’ (Gifford 1957, 6). In such a lower valley lie the modern villages of Shrewton and Rollestone, and through it flows the river Till, the nearest modern open water supply to the barrows. This connects the area to the River Avon via the Wylye and Nadder.

scholarly journals Фотоиндуцированная обратимая локальная деформация рельефа поверхности в объемных монокристаллах TlInSe-=SUB=-2-=/SUB=-, TlGaTe-=SUB=-2-=/SUB=- и TlSe

2018 ◽  
Vol 44 (14) ◽  
pp. 86
Author(s):  
Y.G. Shim ◽  
T. Asahi ◽  
K. Wakita ◽  
Н.Т. Мамедов ◽  
Е.Н. Алиева ◽  
...  
Keyword(s):  
Laser Radiation ◽  
Room Temperature ◽  
Surface Deformation ◽  
Damage Threshold ◽  
Spot Size ◽  
Photon Absorption ◽  
Laser Radiation Intensity ◽  
Laser Spot Size ◽  
Absorption Length ◽  
Bulk Single Crystals

AbstractGiant macroscopic expansion of the surface relief, localized within a laser spot size, has been observed in bulk single crystals of TlInSe_2, TlGaTe_2, and TlSe at room temperature and laser radiation densities lower by at least two orders of magnitude than the material optical damage threshold. Quantitative estimations of the deformation magnitude in this local region were obtained using an interference dilatometer. The photon absorption length was determined with the aid of spectroscopic ellipsometry. It is established that the surface deformation amounts to 2.6 × 10^–3 at a laser radiation intensity of 19 mW/mm^2. The observed phenomenon has a thermal nature and is probably related to a low thermal conductivity of the materials studied.

scholarly journals PENGARUH PIJAT BAYI TERHADAP LAMA TIDUR BAYI DI DESA DUWET KECAMATAN WONOSARI KABUPATEN KLATEN

2016 ◽  
Vol 4 (1) ◽  
Author(s):  
Warsini Warsini ◽  
Dyah Nugraini
Keyword(s):  
Lower Limit ◽  
Sampling Technique ◽  
Infant Sleep ◽  
Not Given ◽  
Infant Massage ◽  
Natural Form ◽  
Upper Limit ◽  
Lack Of Information ◽  
Long Sleep ◽  
The Village

Background: Even the oldest massage is an activity used by humans to expelfatigue and stress. Lack of information and knowledge of parents of massage,makes many parents think a massage is not a scientific and natural form oftherapy for infants. Most mothers believe massage is necessary only when theirchild had flu and colds.Purpose of the study: To determine the effect of infant massage on infant sleepduration in the village of Duwet, Wonosari Subdistrict, Klaten Regency.The subject: The population in this study is a baby in the village of DuwetWonosari District of Klaten regency totaling 45 babies. Samples that met thestudy criteria and amounted to 20 babies. The sampling technique is simplerandom sampling.Methods: The data collection is done by the experimental method is bymeasuring how much sleep babies after intervention. Data were analyzed usingstatistical tests Independent t-test.The results: Long sleep in infants that give the infant massage is known that atleast 11 hours and a maximum of 18 hours with an average bed is 15.90 hours.Long sleep in infants who were not given the infant massage is known at least 12hours and a maximum of 17 hours with an average bed is 13.90 hours. Statisticalanalysis showed p: 3.967 with an upper limit 0.047 and lower limit 0.33.Conclusion: There is a statistically significant effect of infant massage with infantsleep duration (p: 3.967 with an upper limit 0.047 and lower limit 0.33).Keywords: infant massage, infant sleep duration

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