共查询到20条相似文献,搜索用时 265 毫秒
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HUO Binghai GAO Jie CUI Shuanjin H. H. Telle Z. T. Salim 《Chinese Journal of Lasers》2000,9(6):558-562
1 Introduction Themethodofresonanceionizatonspectroscopy (RIS)wasintroducedintheearly 1970sfortheultra sensitivedetectionofatoms .Asthenameimplies ,inthetechniqueionshavetobedetected ;sincethecollectionofionsisusuallyconsiderablymoresensitiveandefficienttha… 相似文献
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It is reported on the recent research using resonant ionization spectroscopy (RIS) and resonant ionization mass spectroscopy (RIMS) to detect the photodissociation product of Rubidium iodide molecules in a molecular beam in an intense laser field. Time of flight mass spectra is recorded. In particular, the appearances of multiphoton ionization are discussed. 相似文献
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Resonant ionization spectroscopy (RIS) and resonant ionization mass spectroscopy (RIMS) are employed to detect the photodissociation product of sodium iodide molecules in a molecular beam in an intense laser field in the absence of the buffer gases. Time of flight mass spectra is recorded. In particular, the appearances of multiphoton ionization are discussed. 相似文献
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铀原子多色三光子共振电离谱研究 总被引:2,自引:1,他引:1
利用Nd:YAG二倍频激光同步泵浦的脉冲染料激光系统、原子束装置、飞行时间质谱和Boxcar技术测量了^238U的多色三光子共振电离谱。研究了电场对铀原子第一激发态的影响。解决了如何确定三角三光子共振电离谱图中所含的单色,双色和三色共振电离峰的问题。 相似文献
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Lalita Tripathi V.K. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1988,16(5):564-569
A relativistic annular electron beam passing through a high-density plasma excites Langmuir waves via Cerenkov interaction. The Langmuir waves are backscattered off ions via nonlinear ion Landau damping. At moderately high amplitudes these waves are parametrically up-converted by the beam into high-frequency electromagnetic radiation, as observed in some recent experiments. A nonlocal theory of this process is developed in a cylindrical geometry. It is seen that the growth rate of the Langmuir wave scales as one-third the power of beam density. The growth rate of parametric instability scales as one-fourth the power of beam density and the square root of beam thickness 相似文献
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Ramachandran K. Tripathi V.K. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1998,26(2):141-144
Near the critical layer, a large-amplitude laser beam creates a transverse plasma channel due to the ponderomotive force. The axis of the channel is normal to the ambient density gradient. Inside the channel, the laser beam decays into counter-propagating ion acoustic and Langmuir waves. A nonlocal theory of the process is developed for a parabolic density profile. The growth rate of the instability is significantly reduced due to the nonlocal effects 相似文献
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A. G. Leonov D. I. Chekhov A. N. Starostin 《Journal of Experimental and Theoretical Physics》1997,84(4):703-715
An experimental investigation and numerical simulation of resonant laser breakdown are performed. As a result, quantitative
agreement between the experimental data on the parameters of a dense resonant plasma (the electron density and the electron
temperature) and the results of calculations in the range of detunings of the laser radiation from resonance Δλ>2–2.5 nm, in which the spatial instability of the intense resonant laser beam and the absorption of radiation are minimal,
is obtained for the first time. It is shown that the previously proposed mechanism of resonant breakdown associated with laser-induced
associative ionization introduces only a small correction to the final extent of ionization of the resonant plasma and scarcely
alters its temperature. The influence of quantum stimulated inverse bremsstrahlung processes, which are usually described
as collisions of the second kind in the resonance case, on the energy gain by electrons is analyzed for the first time in
reference to specific experimental findings. The numerical calculations show that at detunings of the order of the Rabi frequency,
the mechanism by which electrons gain energy through the resonant system does not reduce to collisions of the second kind
and can significantly increase the density of the resonant plasma. However, in this range of detunings the laser beam is still
strongly perturbed by instability processes, precluding a proper comparison of the theory with experiment. At large Δλ the classical and quantum cases differ from one another only slightly, and the values of N
e calculated for both mechanisms lie within the measurement error.
Zh. éksp. Teor. Fiz. 111, 1274–1296 (April 1997) 相似文献
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H.-B. Valentini 《等离子体物理论文集》1970,10(3):207-222
Magneto-acoustic waves generated by fluctuations in the Hall parameter, the electric conductivity and the stream velocity are theoretically investigated in a weakly ionized plasma streaming across a strong external magnetic field and bearing a current flowing perpendicular to both magnetic field and stream velocity. The investigations hold for seeded rare gas plasmas at any degree of seed ionization but are resticted to waves propagating in parallel or antiparallel direction to the current density vector and in parallel or antiparallel direction to the stream velocity vector and to wave lengths which are small in comparsion to the interaction length which occurs as a characteristic wave length. The influence of these waves on the mean current density and the mean Hall field intensity is calculated in case of small amplitudes and low degree of seed ionization up to second order terms. Omitting Ohmic heating the dispersion equation can be solved exactly. A phase shift exists between the fluctuations in gas density and gas velocity. The phase velocity and the amplification rate depend on the wave length. Typical results are represented in a diagram. For both types of waves the phase velocity slightly rises with increasing wave length, while the amplification rate decreases. Waves propagating in opposite direction to the current density vector are amplified, if the electron velocity exceeds a critical value. They reduce the mean current density and the mean Hall field intensity. Waves propagating in opposite direction to the stream velocity vector are also amplified except for very high degrees of seed ionization. The threshold current density is greater than that for the waves of the first type approximately by the Hall parameter as factor. At extremely high degree of seed ionization the phase velocity is directed opposite to the direction occuring at weakly ionized seed. Waves of the second type decrease the mean current density, but increase the mean Hall field intensity. 相似文献
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L. Celona S. Gammino F. Maimone D. Mascali N. Gambino R. Miracoli G. Ciavola 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2011,61(1):107-115
Ion sources have a significant number of applications in accelerator facilities and in industrial applications. In particular,
the electron cyclotron resonance ion sources (ECRIS) are nowadays the most effective devices that can feed particle accelerators
in a continuous and reliable way, providing high current beams of low and medium charge state ions and lower, but still remarkable,
beam current for highly charged ions. In recent years several experiments have shown that the current, the charge states and
even the beam shape change by slightly varying the microwave frequency (the so-called frequency tuning effect – FTE). The
theoretical explanation of these results is based on the difference in the electromagnetic field pattern over the resonance
surface, i.e. that region where the electrons resonantly interact with the incoming wave. In order to be consistent with the
experiments, this model requires that standing waves are formed also in presence of a dense plasma. The proof was sought by
means of a series of measurements performed with a network analyzer and with a plasma reactor operating at 2.45 GHz, according
to the principles of the microwave discharge ion sources (MDIS). The measurements have been carried out with the aim to achieve
the electromagnetic characterization of the plasma chamber in terms of possible excited resonant modes with and without plasma,
and they reported that resonant modes are excited inside the cavity even in presence of a dense plasma. It was observed that
the plasma dynamics strongly depends on the structure of the standing waves that are generated. The measurement of the eigen-frequencies'
shifts were carried out for several values of pressure and RF power, thus linking the shift with the plasma density measured
by a Langmuir probe. The changes in plasma shape, density and electron temperature have been also monitored for different
operating conditions. A strong variation of plasma properties has been observed as a consequence of the introduction of the
Langmuir probe inside the resonant cavity, thus demonstrating that the standing wave can be strongly perturbed even by means
of relatively small metallic electrodes. The measurements reported hereinafter are relevant also for ECRIS, because they confirm
the validity of the theoretical model that describes the frequency tuning. 相似文献
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T. Sonoda M. Wada H. Tomita C. Sakamoto T. Takatsuka T. Noto H. Iimura Y. Matsuo T. Kubo T. Shinozuka T. Wakui H. Mita S. Naimi T. Furukawa Y. Itou P. Schury H. Miyatake S. Jeong H. Ishiyama Y. Watanabe Y. Hirayama 《Hyperfine Interactions》2013,216(1-3):103-107
We developed a prototype laser ionization gas cell with a beam extraction system. This device is for use of PArasitic Laser Ion-Source (PALIS), which will be implemented into RIKEN’s fragment separator, BigRIPS as a part of SLOWRI. Off-line resonant laser ionization for stable Co, Cu, Fe, Ni, Ti, Nb, Sn, In and Pd inside the gas cell, ion extraction and transport to the high-vacuum region via SPIG and QMS have been confirmed (Sonoda et al, Nucl Instrum Meth B 295:1, 2013). 相似文献
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A. Teigelhöfer J. Lassen Z. Abboud P. Bricault H. Heggen P. Kunz R. Li T. Quenzel S. Raeder 《Hyperfine Interactions》2013,216(1-3):65-70
Resonant ionization laser ion sources (RILIS) are popular ion sources if intense, radioactive ion beams (RIBs) with minimal isobaric contamination are required. The intensity of the ion beam depends strongly on the applied resonant laser ionization scheme. Based on the all solid state laser system TRIUMF’s RILIS (TRILIS) is using, the off-line development towards an efficient ionization scheme for yttrium is presented. Several continuous wavelength scans have been performed to compare different nonresonant ionization schemes and to identify suitable Rydberg or autoionizing states for resonant ionization schemes. 相似文献
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原子法激光同位素分离的核心之一是如何高效地将原子激发电离.本文从原子法激光同位素分离的实际情况出发,研究了原子吸收谱线的Doppler展宽对原子电离率的影响.研究中使用的理论工具是原子激发电离的密度矩阵方程,并利用数值计算方法对方程进行求解.研究结果表明:当吸收谱线有Doppler展宽时,在激光参数不变的条件下原子电离率会降低;且当激光功率固定时,存在使原子电离率为最大的线宽值.这与已发表文献中无Doppler展宽时的计算结果有很大不同.为了追求最佳的原子电离效果,在原子法激光同位素分离系统中激光应该尽可能地工作在最佳线宽条件下.如果激光线宽有不可控的随机波动,在技术上让激光线宽略大于最佳线宽更为有利.无论如何控制激光线宽,尽可能地降低原子吸收谱线的Doppler展宽都有利于原子电离率的提高. 相似文献
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Ionization of atoms by the spatial gradient of the pondermotive potential in a focused laser beam is investigated. Rydberg ions, formed during the interaction of noble gas atoms with an intense laser pulse, are used to probe the gradient field. Rydberg ion species with higher ionization potentials are produced at locations where the gradient field is largest. The measured Rydberg ion yields differ dramatically from estimates that ignore gradient-field ionization, but are in good agreement with predictions that include the effect. 相似文献
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Bhimsen K. Shivamoggi 《等离子体物理论文集》1990,30(3):421-430
In a plasma acted on by an intense laser field, one encounters the problem of nonlinearly-coupled Langmuir and ion-acoustic waves. We use a generalized perturbation theory to discuss the nature of coupled oscillatory waves in this system, and the possibility of formation of an ionsheath. 相似文献
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Initiation and evolution of breakdown of gas gaps by surge voltage pulses with a rise time of ≤1 ns are investigated experimentally
and theoretically. The propagation of ionization waves for a uniform initial electron distribution in the gap is analyzed.
The results of calculation are in qualitative agreement with the experiment. It is shown that the evolution of ionization
waves leads to electric field redistribution in the discharge gap, and a region of an enhanced field with the strength sufficient
for initiating emission processes and generation of a short fast electron beam in the cathode region is formed at the cathode
for a very short time (up to 100 ps). 相似文献