共查询到20条相似文献,搜索用时 31 毫秒
1.
Microplasmas produced from 15 μm methanol droplets irradiated by 100 fs laser pulses in the intensity range 1014–1016 W cm?2 are investigated via measurements of the hot electron temperature and x-ray yields under different conditions of intensity, polarization state, and plasma scale-length. The scale length of the drop-let plasma is increased with an intentional prepulse that is 10 ns ahead of the main pulse. Hot electron temperatures up to 48 keV have been measured at intensities of 2.5 × 1015W cm?2 and the scaling of temperature as a function of intensity is determined for a long scale-length droplet plasma. The polarization and ellipticity dependence of the hard x-ray yield from the microdroplet plasmas are used to probe the shape of the droplet after irradiation by a prepulse. 相似文献
2.
V. S. Belyaev V. I. Vinogradov A. P. Matafonov A. M. Chekmarev A. G. Karabadzhak 《Laser Physics》2006,16(3):477-487
The interaction of high-power picosecond laser radiation with solid targets is experimentally studied for the first time at various spectral distributions of a chirped laser pulse. The interaction of the high-power laser radiation with the target is studied at four regimes of the experimental setup: (i) at a relatively high contrast (103) in the picosecond (Δt ~ 25 ps) range, (ii) at a relatively low contrast (3 × 101) in the picosecond (Δt ~ 25 ps) range, (iii) with spectral distortions of the chirped pulse, and (iv) with a strongly modulated spectrum of the chirped pulse. The results obtained reveal a strong dependence of the atomic and nuclear processes in the laser picosecond plasma on the spectral distribution of the chirped laser pulse. The prospects for the application of the spectral interferometry of chirped pulses for the online control of the parameters of the high-power laser radiation are demonstrated. 相似文献
3.
We report here an experimental study of the ionic keV X-ray line emission from magnesium plasma produced by laser pulses of
three widely different pulse durations (FWHM) of 45 fs, 25 ps and 3 ns, at a constant laser fluence of ∼1.5 × 104 J cm − 2. It is observed that the X-ray yield of the resonance lines from the higher ionization states such as H- and He-like ions
decreases on decreasing the laser pulse duration, even though the peak laser intensities of 3.5 × 1017 W cm − 2 for the 45 fs pulses and 6.2 × 1014 W cm − 2 for the 25 ps pulses are much higher than 5 × 1012 W cm − 2 for the 3 ns laser pulse. The results were explained in terms of the ionization equilibrium time for different ionization
states in the heated plasma. The study can be useful to make optimum choice of the laser pulse duration to produce short pulse
intense X-ray line emission from the plasma and to get the knowledge of the degree of ionization in the plasma. 相似文献
4.
V. N. Nevolin V. Yu. Fominskii A. G. Gnedovets V. E. Koshmanov 《Technical Physics》2005,50(6):705-710
Results are presented from experimental studies of pulsed plasma flows generated by nanosecond laser pulses with an intensity
of 7 × 108 W/cm2 from a solid-state target in a strong electric field. The current pulses through the laser target and the depth distributions
of the iron ions implanted in a silicon substrate to which a negative high-voltage pulse was applied are measured. The physical
processes occurring in laser plasma with an initial iron ion density of 6 × 1010 cm−3 are simulated numerically by the particle-in-cell method for different delay times and different shapes of the accelerating
high-voltage pulse. The model developed allows one to calculate the ion flows onto the processed substrate, the electron flows
onto the target, and the energy spectra of the implanted ions. The results from computer simulations are found to be in good
agreement the experimental data. 相似文献
5.
V. S. Belyaev V. I. Vinogradov A. P. Matafonov V. P. Krainov V. S. Lisitsa A. Ya. Faenov V. P. Andrianov G. N. Ignatiev Yu. I. Kozhunov O. B. Kozlov 《Physics of Atomic Nuclei》2006,69(6):919-923
Experimental data on neutron production in a plasma generated on a Be target by a picosecond laser of intensity 2 × 1018 W/cm2 are presented. In contrast to previous measurements, a Ta converter is not used in this study to generate γ rays. The neutron yield is equal to 2 × 103 over a solid angle of 4π steradians per laser pulse. A simultaneous measurement of the maximum energy of hard x rays gave E γmax ~ 6 MeV, the number of these photons being 5 × 108 over an angle of 4π steradians per laser pulse. The energy distributions of fast electrons and photons are estimated theoretically. 相似文献
6.
V. S. Belyaev V. I. Vinogradov A. S. Kurilov A. P. Matafonov V. P. Andrianov G. N. Ignat’ev A. Ya. Faenov T. A. Pikuz I. Yu. Skobelev A. I. Magunov S. A. Pikuz Jr. B. Yu. Sharkov 《Journal of Experimental and Theoretical Physics》2004,98(6):1133-1137
Neutron production as a result of the reaction 2H(d, n)3He in a picosecond laser plasma is reported. A considerable neutron yield of 5×104 per pulse is obtained for the first time in a picosecond laser plasma on the surface of a solid deuterated target at laser radiation intensity of 3×1017 W/cm2. 相似文献
7.
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9.
The characteristics of A1 and (CH2)n plasmas produced by a high-power CO2 laser are investigated over the flux range 1010-5 × 1011W/cm2 where absorption processes other than simple inverse Bremsstrahlung are active. The threshold dependent behavior of the measured plasma parameters indicates the presence of the parmetric decay instability. 相似文献
10.
11.
K. A. Ivanov S. A. Shulyapov A. V. Rusakov A. A. Turinge A. V. Brantov A. B. Savel’ev R. M. Dzhilkibaev V. G. Nedorezov D. S. Uryupina R. V. Volkov V. Yu. Bychenkov 《Physics of Particles and Nuclei Letters》2014,11(1):54-59
The results of X-ray diagnostics of plasma created at a material surface by a laser pulse with an intensity of up to 2.5 × 1018 W/cm2 are presented. The experimental data are compared with the results of numerical modeling of the laser-plasma interaction while accounting for the detector-response function. Examples of possible nuclear problems that can be solved with the use of laser plasma as a source of charged particles and X-ray quanta are given. 相似文献
12.
Microdroplets of 15-μm diameter are subjected to ultra-short laser pulses of intensities up to 1015Wcm−2 to produce hot dense plasma. The hot electrons produced in the microdroplet plasma result in efficient generation of hard X-rays in the range 50–150keV at an irradiance as low as 8×1014Wcm−2. The X-ray source efficiency is estimated to be about 2 ×10−7%. A prepulse that is about 11ns ahead of the main pulse strongly influences the droplet plasma and the resulting X-ray emission. For a similar laser prepulse and intensity, no measurable hard X-ray emission is observed when the laser is focused on a solid target of similar composition and this indicates that liquid droplet targets are best suited for hard X-ray generation in laser–plasma interactions. 相似文献
13.
采用一维粒子模拟(PIC)方法,研究了相对论效应对P偏振激光斜入射非均匀等离子体时产生的共振吸收的影响. 计算表明,弱相对论情况下,在临界面附近产生的电子等离子体波的相对论非线性效应占主要作用;随着入射光场的逐渐增大,吸收率逐渐降低. 当入射光强超过3.7×1017W/cm2时,由于超短激光脉冲本身在等离子体中产生相对论效应、等离子体波破裂效应,以及参量不稳定过程激发等,吸收系数随着激光强度又开始增加. 固定等离子体密度标长,取不同的激光入射角、电子初始温度,相对论效应对吸收系数的影响是一致的.
关键词:
激光等离子体
相对论效应
共振吸收
粒子模拟 相似文献
14.
The critical intensity inside plasma filaments generated in air by high-power, ultra-short laser pulses is estimated analytically
and compared to recent experimental data. The result, Icrit≈4×1013 W/cm2, is highly relevant for atmospheric applications.
Received 18 August 2000 / Published online: 8 November 2000 相似文献
15.
使用800nm飞秒脉冲激光研究了Xe,Ar,He等原子团簇对激光的吸收.实验结果表明,脉冲阀门的工作压力、所使用的气体种类等因素对团簇的尺寸及团簇对激光的吸收影响很大.在阀门工作压力为20×105Pa、激光功率密度为1×1015W/cm2的条件下,Xe团簇对激光的吸收高达45%.激光预脉冲的存在会降低原子团簇对激光能量的吸收.离子能量测量结果表明,团簇对激光的高效吸收导致较高离子温度等离子体的生
关键词:
原子团簇
飞秒激光
能量吸收效率
高能离子 相似文献
16.
A. Ya. Faenov A. I. Magunov T. A. Pikuz I. Yu. Skobelev S. Stagira F. Kalegari M. Nisoli S. De Silverstri L. Poletto P. Villoresi A. A. Andreev 《JETP Letters》2006,84(6):308-313
X-ray spectra from Teflon targets irradiated by laser pulses with a duration of 60 fs to 1 ps have been investigated experimentally. It is shown that, when the contrast of the laser pulse is sufficiently low, the effect of self-focusing of the main laser pulse in the plasma produced by the prepulse can significantly enhance the generation efficiency of fast particles. In this case, ions with energies as high as ~1 MeV are observed at relatively low laser intensities, q las ≈ (4–6) × 1016 W/cm2. 相似文献
17.
A theory is developed for calculating the charge composition of a cluster plasma produced upon irradiation of large atomic clusters by the field of a superatomic femtosecond laser pulse. The theory is based on the overbarrier process of a successive multiple internal ionization of atomic ions inside a cluster accompanied by the external field ionization. Collision ionization is also taken into account in the calculations. The theory is illustrated by the example of a cluster consisting of 106 xenon atoms irradiated by a 50-fs laser pulse with a peak intensity of 2×1018 W/cm2. In this case, the Xe26+ ions dominate. The amounts of atomic xenon ions with multiplicity up to 31 are calculated. 相似文献
18.
K. Venkata Krishnaiah C. K. Jayasankar V. Venkatramu S. F. Leόn-Luis V. Lavín S. Chaurasia L. J. Dhareshwar 《Applied physics. B, Lasers and optics》2013,113(4):527-535
Yb3+-doped fluorophosphate glasses were prepared by melt-quenching technique and characterized their spectroscopic properties to assess the laser performance parameters. The magnitude of absorption (emission) cross-sections at 975 nm for all the studied Yb3+-doped glasses is found to be in the range of 0.29–1.50 × 10?20 (0.59–1.99 × 10?20 cm2) which is much higher than those of commercial Kigre QX/Yb: 1.06 × 10?20 (0.5 × 10?20 cm2) laser glass. The luminescence lifetimes of 2F5/2 level decrease (1.15–0.45 ms) with increase in Yb2O3 concentration (0.1–4.0 mol%). Effect of OH? content on luminescence properties of Yb3+ ions has also been investigated. The effect of radiative trapping has been discussed by using McCumber (McC) and Fuchtbauer–Ladenburge (F–L) methods. The product of experimental lifetimes and emission cross-sections for 0.1 mol% Yb2O3-doped glass is found to be 2.28 × 10?20 cm2 ms which indicates that the higher energy storage and extraction capability could be possible. The detailed spectroscopic results suggest that the studied glasses can be considered for high-power and ultrashort pulse laser applications. 相似文献
19.
U. Chakravarty P. A. Naik B. S. Rao V. Arora H. Singhal G. M. Bhalerao A. K. Sinha P. Tiwari P. D. Gupta 《Applied physics. B, Lasers and optics》2011,103(3):571-577
A comparative experimental study of the X-ray emission in the water-window spectral region has been performed using carbon
nanofibers (CNFs) of different sizes and graphite plate targets, irradiated with ultra-short (Ti:sapphire) laser pulses. More
than an order of magnitude enhancement in the X-ray yield is observed from CNFs of 60-nm diameter with respect to graphite
targets. The X-ray emission from CNFs of 160-nm diameter was also high. The integrated X-ray yield of these carbon-based targets
scales with the laser intensity (I
L) as IL ~ 1.3-1.4I_{\mathrm{L}}^{\sim 1.3-1.4} in the intensity range of 4×1016–4×1017 W/cm2. The effect of the laser pulse duration on the X-ray emission from the CNFs was also studied by varying the pulse duration
from 45 fs up to 3 ps at a constant fluence of 2×104 J/cm2. The optimum laser pulse duration for maximum X-ray emission increases with the diameter of the CNFs used. The results are
explained from physical considerations of heating and hydrodynamic expansion of the CNF plasma in which resonance field enhancement
takes place while passing through two times the critical density. The results add to the efforts towards achieving an efficient
low-cost water-window X-ray source for microscopy. 相似文献
20.
In this work, wave formation in laser-produced plasma is investigated by an analysis of time-of-flight signal of the electron pulse. Electrons are extracted from a non-equilibrium plasma, generated by pulsed laser ablation on a solid Ge target. The process is represented by ion-acoustic waves, which are generated from an external perturbation, given by the positive bias voltage of a Faraday cup. The characteristics of the waves depend substantially on the geometry of the plasma expansion chamber and on laser fluence, but are independent on bias potential. A KrF excimer UV laser was employed for plasma generation. Measurements were performed at two different laser fluences, 4 and 7 J/cm2. The plasma created propagates with a mean velocity of about 1.1?×?104 m/s. A movable Faraday cup was employed in order to collect electrons at different bias voltage values. 相似文献