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1.
A method of studying a non-equilibrium x-ray laser plasma is
developed by extending the existing one-dimensional similarity
equations to the case of two-dimensional plasma study in the
directions perpendicular to the slab and along a focal line. With this
method the characteristics of pre-plasma are optimized for transient
neon-like Cr x-ray laser. It is found that when the duration and the
intensity of 1.053μm pre-pulse are 1.2ns and
6.5 TW/cm2 respectively with a delay time of 1.5ns, the
temperature and the temperature discrepancy each approach a proper
state, which will provide a uniform distribution of properly ionized
neon-like Cr ions before the arrival of pumping pulse. 相似文献
2.
Demonstration of Mo Soft X-Ray Lasers with a Grazing Incidence Pumping Scheme in the XL-II Facility
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A Ni-like Mo soft x-ray laser (SXRLs) operating at 18.9nm has been demonstrated by employing a grazing incidence pumping scheme with 120m^3 in the 200ps pre-pulse and 140mJ in the 200fs main pulse. The SXRL gain is estimated to be 1.5-3cm^-1 when a grazing incidence angle of 14° is applied. Numerical simulations are also performed to investigate the dynamics of the ion distribution. It is found that a high intensity at 2.4× 10^14 W/cm^2 of the 200fs main pulse could heat the pre-plasma rapidly to an appropriate temperature for population inversion, and could compensate for the shortage of the total pump energy to a certain extent. 相似文献
3.
在超强激光系统中,对比度和本底宽度是压缩光脉冲极为重要的指标。在啁啾脉冲放大系统的压缩阶段,在啁啾脉冲宽度为141ps,啁啾系数为1000,B积分值分别为0,1和2的情况下,模拟了自相位调制效应(SPM)对压缩脉冲的峰值光强、脉冲宽度和本底宽度的影响。结果表明:在B积分值为2的条件下,若不补偿非线性色散,压缩脉冲的峰值强度降为无自相位调制效应时的65%左右,脉冲宽度约为种子脉冲宽度的2倍,本底宽度则增加到原来的3倍左右;在B积分值大于0.5的情况下,本底宽度和B积分值近似成线性关系。 相似文献
4.
5.
E.G. Gamaly A.V. Rode B. Luther-Davies 《Applied Physics A: Materials Science & Processing》1999,69(7):S121-S127
The ionization of laser-ablated vapours with lasers producing ns duration pulses at various wavelengths has been studied in order to understand the mechanisms of the vapour-plasma transition. It has been established that there are several regimes characterizing the laser-target interaction which depend on laser intensity, wavelength, and pulse duration. The range of laser intensities for optimal laser evaporation is determined by the condition of transparent vapours. The intensity range is upper-limited by the opaque plasma formation due to vapour optical breakdown. Results are given for laser evaporation of graphite with Nd:YAG laser (1.064 7m), KrF laser (248 nm) and ArF laser (193 nm). For the UV laser wavelength the regime of skin-effect interaction was proposed as the mechanism of ion acceleration, and the range of validity of the skin-effect mode was established. With UV lasers the interaction has a bimodal nature: the interaction may proceed initially in the skin effect regime, resulting in a few high-energy ions, until hydrodynamic expansion begins at a later stage. The skin-effect interaction at the initial stage of the UV laser pulse gives the first, to our knowledge, explanation for the acceleration of ions up to ~100 eV at low laser intensities of 108-109 W/cm2 and ns-range pulse duration. 相似文献
6.
Through the use of time and space integrated kiloelectronvolt (keV) spectroscopy, we investigate the thermal emission of plasma, which produces strong line emission from the titanium K shell (He-a at 4.7 keV and H-α at 4.9 keV), created by laser. In order to optimize the conversion efficiency enhancement on titanium foils, the experiment is conducted under a variety of laser-driven intensity conditions. The X-ray emission intensity at 4.7 keV is measured and compared with prediction. The experimental result demonstrates that the solid Ti target laser-produced plasma (LPP) source has X-ray emission at 4.7 keV, which are all generated from electronic transitions in Ti ions at pulse width of 2.1 ns or 30 ps, the crudely evaluated He-α X-ray intensity appears to slightly increase with laser intensity enhancement, and the pre- pulse effect increases the conversion efficiency of the He-α X-ray. In addition, a 90-μm-thick Ti foil as a filter is used to transmit He-α X-ray at near 4.7 keV, creating a quasi-monochromatic transmission and greatly reducing the lower- and higher-energy background. 相似文献
7.
8.
Laser-produced plasma helium-like titanium Kα x-ray source and its application to Rayleighben-Taylor instability study
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Several experiments are performed on the ShenGuang-II laser facility to investigate an x-ray source and test radiography concepts. X-ray lines emitted from laser-produced plasmas are the most practical means of generating these high intensity sources. By using a time-integrated space-resolved keV spectroscope and pinhole camera, potential helium-like titanium Kα x-ray backlighting (radiography) line source is studied as a function of laser wavelength, ratio of pre-pulse intensity to main pulse intensity, and laser intensity (from 7.25 to ~11.3× 1015 W/cm2). One-dimensional radiography using a grid consisting of 5 μm Au wires on 16 μm period and the pinhole-assisted point projection is tested. The measurements show that the size of the helium-like titanium Kα source from a simple foil target is larger than 100 μm, and relative x-ray line emission conversion efficiency ξx from the incident laser light energy to helium-like titanium K-shell spectrum increases significantly with pre-pulse intensity increasing, increases rapidly with laser wavelength decreasing, and increases moderately with main laser intensity increasing. It is also found that a gold gird foils can reach an imaging resolution better than 5-μm featured with high contrast. It is further demonstrated that the pinhole-assisted point projection at such a level will be a novel two-dimensional imaging diagnostic technique for inertial confinement fusion experiments. 相似文献
9.
Self-Starting Passively Mode-Locked Er^3+/Yb^3+ Codoped Phosphate Glass All-Fibre Ring Laser
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A self-starting, passively mode-locked all-fibre ring laser based on the homemade Er^3+/Yb^3+ codoped phosphate glass fibre is reported. Dual-pump sources were used to achieve the mode-locked operation in the experiment. The fundamental mode-locked pulse repetition rate is 10.67MHz. The pulse duration, assumed as the fit of hyperbolic secant pulse shape, is 5.82ps. We also observe the multi-pulse output of the fibre laser. 相似文献
10.
在SILEX-1激光器上测量了超强飞秒激光与Ta靶相互作用产生的出射超热电子能谱及角分布,研究了出射超热电子加热机制。激光脉宽为 30 fs,激光功率密度为8.5×1018 W/cm2。靶前法线方向超热电子温度为550 keV。从实验结果可知:共振吸收是靶前法线方向超热电子主要加热机制,这与靶前存在大密度标长预等离子体的实验条件吻合。靶厚为6~50 μm时,靶后超热电子沿法线方向出射;靶厚为2 mm时,该发射峰消失。 相似文献
11.
Plasma line emission is observed in simulations of dense plasma irradiated by moderately intense light pulses of duration some tens of femtoseconds, and its scaling with density and with laser intensity is studied. Plasma emission is recorded both during the pulse where it is observed against the background spectrum of harmonics of the laser frequency as well as postpulse. Harmonics of the plasma line up to the fifth have been observed. An unexpected feature present in most of the reflected light spectra appears on the blue side of the plasma line with a central frequency omega approximately 1.5omega(p). 相似文献
12.
Investigation on the hydrodynamics of slab x-ray laser plasma by nonuiform line focused laser irradiation
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Based on the two-dimensional model,this paper compares the hydrodynamics of slab x-ray laser plasma produced by different nonuniform line focused irradiations.It finds that the average intensity and the duration of laser pulse and the overall shape of the intensity distribution in the focal line have different influences on the plasma.Calculations show that the evolution of temperature variation is more sensitive to the pulse duration and the electron density variation is more sensitive to the pulse intensity.Pulses with duration of 200 ps to 500 ps and with intensity of 0.2 TW/cm 2 to 1.0 TW/cm 2 are proved acceptable in slab x-ray lasers. 相似文献
13.
A New Discharge Scheme of a Prepulse Plus Two Main Pulses for Capillary-Discharge Soft-X-Ray Laser
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Reducing the capillary-discharge current is one way of possibly decreasing the pumping power requirement. We examine the influence of various discharge currents on laser intensity and determine the suitable pre-discharge condition for a 46.9-nm discharge-pumped Ne-like Ar soft-x-ray amplifier. The experimental results show that a high additional pre-pulse current at amplitude of several kA and with a very short duration of several tens of nanosecond can effectively decrease the amplitude of the main discharge current at the lasing time. We propose a new discharge scheme of a pre~pulse plus two main pulses which appears to significantly decrease the requirement for discharge current. This in turn may decrease the pumping power requirement for the capillary discharge laser and can greatly increase laser efficiency. 相似文献
14.
A cataphoretic input of calcium vapour into the active volume of pulsed He-Ca^+ laser is designed and made. The recombination laser at 373.3 nm and the R-M transition laser at 854.6 nm are achieved experimentally with modified Blumlein circuit by high-frequency longitudinal pulsed discharge. The dependences of work parameters such as the pulse frequency, the power supply voltage and the helium pressure on laser output characteristics at 373.3nm line are measured and discussed. The maximum laser output power of 136mW and the specific power of 5.9 m W/cm^3 are obtained, respectively. 相似文献
15.
A.J. Verhoef J. Seres K. Schmid Y. Nomura G. Tempea L. Veisz F. Krausz 《Applied physics. B, Lasers and optics》2006,82(4):513-517
High intensity contrast ratio, pre-pulse free pulses with pulse duration of 5 fs and pulse energy of 1 mJ were generated at a repetition rate of 1 kHz by compressing the output pulses of a multi-stage Ti:sapphire laser amplifier system in a Ne-gas-filled hollow fibre. The spatial and temporal properties of the output laser beam were fully characterised. PACS 42.60.Jf; 42.65.Re; 42.81.Qb 相似文献
16.
Numerical Modelling of QCW-Pumped Passively Q-Switched Nd:YAG Lasers with Cr^4+:yAG as Saturable Absorber
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Passively Q-switched quasi-continuous-wave (QCW) diode-pumped Nd:YAG laser with Cr^4+ :YAG as saturable absorber is numerically investigated by solving the coupled rate equations. The threshold pump rate for passively Q-switched QCW-pumped laser is derived. The effects of the pump rate and pump-pulse duration on the laser operation characteristics are studied theoretically. The pump power range can be estimated according to the number of output pulses. The numerical simulation results are in good agreement with the experimental results. 相似文献
17.
Scattering-enhanced femtosecond optical parametric generation (OPG) has been observed and studied in detail, which may decrease the pump threshold of OPGs dramatically and may make OPGs reliable. The experimental demonstration in a LiNbO3 crystal shows that strong enough OPG can be obtained at pump intensity of only about 30GW/cm2 which is well below the crystal damage threshold Either a synchronized pulsed laser or a cw laser has been used as the scattering source, of which the wavelength, spectral shape and irradiating angle are not strictly required. 相似文献
18.
Optical emission of plasma is used to investigate the characteristics of dynamics distribution in the plume gen- erated by ablation of a SiC sample using Nd:YAG laser. The plume expansion dynamics is characterized by time-of-flight measurement. We find that the profiles of Si (I) (390.55 nm) split into two components and the Si (1I) (634. 71 nm) spectra show two distinct expansion dynamics regions. The time-of-flight measurement of Si(ll) (634. 71 nm) under different laser irradianee conditions, from 0.236 G W/cm^2 to 1.667 G W/cm^2, are presented and discussed. 相似文献
19.
用高温应变计和热偶计等诊断技术,研究连续波氧碘化学激光(CW/COIL)与铝合金板作用产生的激光热应力。当照射靶面激光强度约1 000 W/cm2时,激光热应力随靶厚的增加而快速减小。当激光辐照靶材厚度h=1.00 mm、激光强度I=640~980 W/cm2时,激光热应力随辐照靶面激光强度的增加而增大。两者的激光热应力-时间曲线随靶厚的减薄或随辐照靶面激光强度的增加而变得越来越复杂。当靶厚h≤2.50 mm,辐照靶面激光强度I≥800 W/cm2时,激光热应力强度超过激光辐照区材料断裂强度,萌生许多孔洞裂纹,引起材料断裂破坏。 相似文献
20.
A theoretical model based on the rate equation for free electron density is proposed to investigate transient progression
of plasma formation in soft biological tissues during laser shock processing. The laser focusing region around the focus point
is considered to be one-dimensional along the direction of the incident beam, and is discretized into numerous thin control
volumes. In simulation of the transient plasma progression, the laser intensity distribution and the temporal evolution of
the free electron density are calculated sequentially for each control volume using a fourth-order Runge–Kutta method with
adaptive time step control. The rate-equation formalism is first validated with previously published theoretical and experimental
results. Simulation of the dynamics of plasma formation is then performed. The results include temporal evolution and spatial
distribution of the free electron density as well as the growth of the plasma. It is shown that the threshold laser intensity
for optical breakdown in water and the maximum length of the resulting plasma obtained from the present model are in good
agreement with existing experimental data.
PACS 42.65.-k; 52.38.-r; 87.80.-y 相似文献