共查询到20条相似文献,搜索用时 15 毫秒
1.
O. Renner E. Förster P. Sondhauss J. S. Wark P. K. Patel 《Czechoslovak Journal of Physics》1998,48(5):557-563
The positions and profiles of x-ray spectral lines emitted from well characterized laserproduced plasmas have been investigated.
The red shifts observed for higher members of the aluminum Lyman series are consistent with theoretical predictions of the
line shifts in hot dense plasmas. The experimentally observed profiles of Al XIII Lya line are interpreted by modeling the radiative transport through plasma with large transverse gradients.
The presented results originated from collaborative effort of the research groups from the Institute of Physics, Prague, University
of Jena and University of Oxford.
This work was supported by the Grant Agency of the Czech Republic under Grant No. 202/97/1186. 相似文献
2.
J.P. Apruzese J. Davis K.G. Whitney 《Journal of Quantitative Spectroscopy & Radiative Transfer》1977,17(5):557-562
We have generalized our treatment of resonance-line radiation from a spherical, laser-heated plasma by including the effects of radiative and collisional line broadening in representing the line-emission and absorption profiles by a Voigt function. We find that the emitted profiles are broadened by factors of five or more, depending on the magnitude of the damping constant. It is also shown that the Al(XIII) to Al(XII) line ratios are seriously affected by the different escape probabilities associated with Doppler and Voigt profiles. We also find that plasma cooling via resonance-line radiation is accelerated relative to that calculated with a pure Doppler profile, and that use of the Voigt profile decreases the density of excited states relative to the Doppler values. These phenomena are analyzed in terms of the differing profile shapes and widths. 相似文献
3.
4.
A lithium spectrum is obtained form vacuum spark discharges using a grazing-incidence flat-field spectrometer. Hydrogen-like lines up to Lyman η are identified in the spectrum. The spectrum is analyzed, and it is found that the experimental line widths increase along the Lyman series. An asymmetry between the blue and red wings appears in the profile of the Lyman ζ line, and becomes significant in the profile of the Lyman ? line. A relatively new method is used to estimate an electron density of 1 ± 0.4 × 1018cm?3 from the experimental degree of asymmetry between the blue and the red wings of the Lyman ζ line. This result is compared with an analysis of the experimental widths of two optically thin lines, namely, Lyman δ and Lyman ζ. In this analysis an electron density of 1.2±0.5 × 1018cm?3 is deduced. The principal quantum number of Lyman η (n=8) is used in the Inglis-Teller formula for the last line seen before the merging of the lines with the continuum, and the estimated electron density is found to be 2.0 × 1018cm?3 for the lithium plasma. Thus, it is demonstrated that the new method employing the asymmetry of the lineshapes in dense plasmas yields results consistent with the analysis of the widths of the lines. However, it requires obtaining the profile of just one spectral line, which is a great advantage. The reference data on the Stark broadening of the Lyman ζ line is also tabulated, which was previously unavailable in the literature. 相似文献
5.
A detailed investigation of aluminum plasma induced by a 1064 nm Nd:YAG laser in air was performed. The emission of spectral lines arising from Al I transition at 396.07 nm, Al II transition at 358.46 nm, Al III transition at 360.72 nm and Al IV transition at 363.05 nm were well-resolved. The plasma parameters including electron temperature and electron density were determined through the Boltzmann plot method using the emission line intensities of the same ionized stages of aluminum atoms and the Stark-broadening profiles of Al II emission line, respectively. The temporal evolutions of the spectral lines belonging to atomic and ionic aluminum elements and the plasma parameters were investigated at three different laser pulse energies. Moreover, the validity of local thermodynamic equilibrium was elucidated in our experimental condition. 相似文献
6.
L. Escobar-Alarcón A. Arrieta E. Camps S. Romero M. Fernandez E. Haro-Poniatowski 《Applied Physics A: Materials Science & Processing》2008,93(3):605-609
The plasma produced by the ablation of a high purity Al2O3 target, using the fundamental line (1064 nm) of a Nd:YAG laser, was characterized. The laser fluence was varied in order
to study its effect on the characteristics of the produced plasma as well as on the properties of the material deposited.
Optical emission spectroscopy (OES) was used to determine the type of excited species present in the plasma. The mean kinetic
energy of the ions and the maximum plasma density were determined from the time of flight (TOF) curves, obtained with a planar
Langmuir probe. The obtained results reveal that the fast peak in the probe curve could be attributed to Al III, while the
slow peak corresponds to the Al II. Aluminum oxide thin films were then deposited under the same conditions of the diagnosed
plasma, in an attempt to correlate the plasma parameters with the properties of the deposited material. It was found that
when Al II ion energies are lower than 461.0 eV the films deposited have structural characteristics similar to that of α-Al2O3, whereas at ion energies greater than 461.0 eV amorphous material was obtained. 相似文献
7.
Apruzese J.P. Thornhill J.W. Whitney K.G. Davis J. Deeney C. Nash T.J. Spielman R.B. L'Eplattenier P. LePell P.D. Failor B.H. Riordan J.C. Whitton B.A. Yadlowsky E.J. Hazelton R.C. Moschella J.J. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1998,26(4):1185-1191
We consider the question of how the temperature profile of a Z-pinch plasma can be determined and/or constrained by the requirement that its observed K-shell spectrum be replicated. As a case study we employ spatially integrated, time-resolved K-shell data obtained from the implosion of 30-wire Al:Mg alloy arrays on the Saturn driver at Sandia National Laboratories. Given the measured pinch size, its K-shell power and line intensities are compared with the predictions of a collisional-radiative-equilibrium plasma model whose temperature profile is varied in seeking agreement with the data. The Al data rules out a large range of possible temperature profiles, but two quite different temperature distributions can both match the measurements. These are: a uniform temperature, or, one with a sharply dropping temperature near the pinch outer edge. However, the measured ratio of the Mg α resonance lines to those of Al, even though time-integrated, excludes the possibility of a uniform temperature distribution 相似文献
8.
Photoelectric absorption measurements have been performed on molecular hydrogen under conditions where the line profile is dominated by Doppler broadening. A curve of growth analysis was used to relate the measured equivalent width to the line oscillator strength, and the appropriate band oscillator strength was calculated from this using Hönl-London factors. Oscillator strengths for eleven Lyman and six Werner bands obtained in this way show close agreement with those deduced from inelastic electron scattering data. Recent theoretical calculations are in good agreement for the Lyman bands and show only a small systematic discrepancy for the Werner bands. 相似文献
9.
对椭圆型聚焦晶体谱仪配X射线CCD相机的X射线谱测量系统进行了优化设计.优化设计后的椭圆型聚焦晶体谱仪系统的工作距离981.56 mm和摄谱范围0.133~0.756nm,并具有很好的谱分辨本领(λ/Δλ≥1000)和信噪比.新设计的椭圆型聚焦晶体谱仪首次在"神光Ⅱ"X光激光靶室上成功地获得了激光等离子体谱线信息并辨认和归类了一些离子的谱线,同时还给出了实验测定的谱仪能量分辨率.其中一些离子谱线诸如类离子共振线、伴线、互组合线和Ly-α线谱可为下一步诊断激光等离子体的电子温度和离子密度的空间分布轮廓打下了坚实基础. 相似文献
10.
Siders C.W. Le Blanc S.P. Babine A. Stepanov A. Sergeev A. Tajima T. Downer M.C. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1996,24(2):301-315
All-optical ultrafast time-resolved plasma diagnostics of plasma-based accelerators (PBA's) are described, with emphasis on the laser wakefield accelerator (LWFA). Specifically, the diagnostic techniques involve replacing the trailing particle bunch in the LWFA with a trailing photon bunch: a weak ultrashort laser pulse. Since this photon pulse is derived directly from the intense pump pulse, practical difficulties such as synchronization and dephasing are eliminated. The interaction of the photon bunch with the plasma wake is essentially a simple time-domain shift in optical phase, which can produce both “DC” phase shifts and frequency blue/red-shifting of the probe pulse spectrum. These phase/frequency shifts are recorded in frequency domain interferograms, which are formally equivalent to time-domain holograms. Experimental results of longitudinal plasma density profiling are presented in which plasma density oscillations (Langmuir waves) in the wake of an intense (Ipeak~3×10 17 W/cm2) laser pulse (~100 fs) were measured with ultrafast time resolution. Phase shifts consistent with large amplitude (~80%) density oscillations at the electron plasma frequency were observed in a fully tunnel-ionized He plasma, corresponding to longitudinal electric fields of ~10 GV/m. Strong radial ponderomotive forces enhance the density oscillations. Finally, proposed single-shot schemes for simultaneous transverse and longitudinal profiling are discussed 相似文献
11.
S. U. Haq R. Ali M. A. Kalyar M. Rafiq A. Nadeem M. A. Baig 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,46(1):1-8
A detailed study has been performed for estimating the orbital
energies, positions and shifts of the Lyman lines of C5+,
Al12+ and Ar17+ under strongly coupled plasma with a
view to understand such line positions and shifts obtained in
laser produced plasma experiments. The effect of strongly coupled
plasma has been treated within the Ion Sphere (IS) model. Both
non-relativistic and relativistic methods have been used for
estimating the spectral properties. Theoretical estimates with IS
model of the plasma are in conformity with the results of laser
plasma experiments on these highly stripped ions. The experimental
data for the systems have also been compared with the theoretical
estimates using Debye screening model of the plasma with spatial
confinements which gives additional restrictions to the wave
functions at finite boundaries. 相似文献
12.
13.
The radial profiles of electrostatic Reynolds stress,plasma poloidal rotations,radial and poloidal electric fields have been measured in the plasma boundary region on the HL-1M tokamak using a multi-array of Mach/Langmuir probes.During experiments of lower hybrid wave current drive,the variations in LHW drive power xill cause changes in the edge electric field,poloidal rotation veloity and Reynolds stress.The results indicate that sheared poloidal flow can be generated in the edge plasma due to radially varied Reynolds stress. 相似文献
14.
The properties of an extensive reflex discharge of large power with one heated and one cold cathode in a magnetic field of 10 to 1500 Gauss were measured. At a neutral hydrogen pressure of 10–4 to 10–3 torr a plasma column was obtained which was 100 cm long, 10 cm in diameter and had a density greater than 10–11 cm–3. The dependence of the radial profile of the potential in the plasma was measured by a heated probe, and the temperature and electron density by Langmuir probes calibrated by a microwave interferometer.The dependence of the origin of low-frequency rotational instability on the parameters of the discharge was studied and the measured critical magnetic field was compared with theory. Apart from this low-frequency instability, intensive oscillations were also found in the discharge current in a frequency band up to 30 MHz, and the dependence of their spectrum on the magnetic field was measured. 相似文献
15.
Apruzese J.P. Kepple P.C. Davis J. Pender J. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1988,16(5):529-533
A major goal of current X-ray laser research is the achievement of gain in the 23.3-43.7 Å wavelength region, known as the `water window'. Silicon is the lowest atomic number element for which all the heliumlike 3-2 transitions lie in this region. The authors examine the fundamental kinetics of recombination lasing in this species, and conclude that the Si XIII 1s 3d 1D 2-1s 2p 1P 1 line at 39.1 Å is an attractive candidate for recombination-pumped lasing. Attainment of gain in this line is somewhat more energetically favorable than for the hydrogenic Al XIII 3-2 transitions, but radiative trapping may be somewhat more troublesome than for H-like Al 相似文献
16.
Joel L. Plawsky Sashidhar S. Panchamgam Shripad J. Gokhale Peter C. Wayner Jr. Sunando DasGupta 《Superlattices and Microstructures》2004,35(3-6):559
A vertical constrained vapor bubble, VCVB, made of fused silica was used to study the stability and oscillations of an evaporating wetting film of HFE- 7000® in a corner. The film thickness profile was measured as a function of time and axial position using an advanced form of image analyzing interferometry. The curvature, apparent contact angle, and pressure profiles for the evaporating film were calculated from the measured film thickness profiles. Oscillation of the liquid film was observed and profiles for both the advancing and receding films were obtained. These are the first such detailed profiles obtained for an oscillating meniscus below a thickness of 0.1 μm.The film thickness profiles demonstrated the spreading of the meniscus during advance as well as the presence of a curvature gradient near the contact line region. The maximum curvature decreased for the advancing menisci and increased with time for the receding menisci. An increase in the adsorbed film thickness was associated with the advancing stage and a decrease with the receding stage. Pressure profiles were measured as a function of position indicating the potential for driving the flow of the fluid toward or away from the contact line. As the film advances or recedes, the pressure gradients change as a function of position fueling the next oscillation cycle. 相似文献
17.
Jong-Chui Park Jae Koo Lee Bongkoo Kang 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》2000,28(2):403-413
This paper presents modeling and experimental results of the voltage, current, and density profiles of a helical resonator plasma source. The source has a 5/4-wavelength (λ) helical resonator structure with the helical coil short-circuited at one end and open circuited at the other end. When the radio frequency (RF) tap for power feeding was located at an odd multiple of λ/4 from the short-circuited end, the observed voltage, current, and plasma density were higher in the short-circuited section than those in the open-circuited section. The opposite property was observed with the RF tap at an even multiple of λ/4. A microstrip transmission line model was used to explain the experimental results. The model accurately predicted the RF voltage and current profiles. After calculation of RF voltage and current, the plasma density was solved numerically. The difference between the calculated and measured plasma density was within a factor of two. The changes on the density profile indicate that the transport properties of plasma can be adjusted with the RF tap position 相似文献
18.
《Journal of Quantitative Spectroscopy & Radiative Transfer》1987,37(4):373-375
We have used a simple glass-to-plasma boundary layer (bl) model to evaluate the influence of bls on measured Hβ line profiles emitted from a T-tube hydrogen plasma. Calculations were performed for a wide range of electron densities and temperatures. The results show that the calculated line profiles for temperatures of 3 × 104 K and higher are significantly wider than they would be if the bls were absent. At the most frequently encountered temperatures of the T-tube plasmas (∽2 × 104 K), the calculated profiles influenced by bls resemble theoretical profiles. No significant influence of the bls on the Hβ central part was found, except when the optical thickness of the whole plasma becomes significant. 相似文献
19.
Direct modeling of the dynamics of a system of many Coulomb particles is applied to analyze the formation stage of a metastable
plasma state from an initial, highly nonideal state, and also to consider some properties of this metastable supercooled state.
It is shown that relaxation of the average particle kinetic energy may be characterized by a universal dimensionless function
and in particular, there is a limiting degree of plasma nonideality which may be achieved in the metastable state, in the
absence of any external influence. The calculated pair correlation functions agree with the results of the Debye model, even
outside its limits of validity. The time dependence of the total dipole moment of the particle system is investigated. It
is shown that oscillations of the total dipole moment are observed. These collective oscillations take place at a frequency
slightly below the Langmuir frequency and the oscillations of free and bound electrons are in antiphase. The hypothesis is
put forward that recombination relaxation is frozen as a result of interaction between quasibound electrons and Langmuir oscillations
of free electrons.
Zh. Tekh. Fiz. 67, 42–52 (August 1997) 相似文献
20.
HL-1M托卡马克边缘参数和雷诺胁强的径向分布 总被引:2,自引:2,他引:0
利用多组马赫/郎缪尔探针测量了HL-1M装置刮离层和边缘静电雷诺胁强,等离子体极向旋转,径向和极向电场的径向分布,在低杂波电流驱动,超声分子束注入,多发弹丸注入和中性束注入实验中,给出了雷诺胁强和极向流的关系。结果表明,由于雷诺胁强的径向变化,托卡马克等离子体可以自发地产生剪切极向流。 相似文献