共查询到20条相似文献,搜索用时 31 毫秒
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T. Gregorkiewicz D. T. X. Thao I. Tsimperidis H. H. P. Th. Bekman C. J. G. M. Langerak J. Michel L. C. Kimerling 《Journal of luminescence》1998,80(1-4):291-295
We investigate the influence of infrared illumination using a free-electron laser on the photoluminescence of erbium-implanted silicon material. In addition to the earlier reported quenching of the Er-related photoluminescence due to dissociation of the intermediate excitation stage, two more features of the energy transfer mechanism are revealed. In the wavelength dependence of the quenching effect a local extreme is detected for a beam energy of approximately 100 meV. A possible origin of this effect is discussed. Further, the current experiment revealed the presence of non-radiative recombination centers which could transfer their energy to Er ions under the influence of the infrared beam. The centers were found to be characterized by extremely slow generation and decay kinetics. 相似文献
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Jie Xu 《International Journal of Theoretical Physics》2018,57(11):3369-3372
A scheme for the preparation of four-ion entangled cluster states has been proposed. Two two-level ions are confined in a linear trap and are simultaneously driven with a laser beam. In the Lamb-Dicke regime, we can get the effective Hamiltonian in the interaction picture.The effective Hamiltonian may be used to describe a realistic physical system. The scheme is insensitive to both the initial vibrational state and heating. 相似文献
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激光氦离子源产生的MeV能量的氦离子因有望用于聚变反应堆材料辐照损伤的模拟研究而得到关注.目前激光驱动氦离子源的主要方案是采用相对论激光与氦气射流作用加速高能氦离子,但这种方案在实验上难以产生具有前向性和准单能性、数MeV能量、高产额的氦离子束,而这些氦离子束特性是材料辐照损伤研究中十分关注的.不同于上述激光氦离子产生方法,我们提出了一种利用超强激光与固体-气体复合靶作用产生氦离子的新方法.利用这种方法,在实验上,采用功率密度5×10~(18)W/cm~2的皮秒脉宽的激光脉冲与铜-氦气复合靶作用,产生了前向发射的2.7 MeV的准单能氦离子束,能量超过0.5 MeV的氦离子产额约为10~(13)/sr.二维粒子模拟显示,氦离子在靶背鞘场加速和类无碰撞冲击波加速两种加速机理共同作用下得到加速.同时粒子模拟还显示氦离子截止能量与超热电子温度成正比. 相似文献
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M. A. Khodorkovskii T. O. Artamonova S. V. Murashov D. Michael L. P. Rakcheeva A. A. Belyaeva N. A. Timofeev A. S. Mel’nikov A. L. Shakhmin 《Technical Physics》2007,52(10):1263-1270
It is found that the composition of a pulsed supersonic molecular beam depends on the preparation conditions of the initial mixture containing water molecules and argon atoms. The mass spectra of the molecular beam components are obtained, and the time evolution of the signal intensities for some of the ions (T form) is traced. It is shown that stable water complexes remaining intact during supersonic flow of the mixture into a vacuum may form depending on the water partial pressure. 相似文献
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Energy and charge distributions of ions are calculated for a cluster beam irradiated by a high-power ultrashort laser pulse. It is shown that the self-consistent field of a cluster ionized by the laser beam strongly affects the characteristics of the ion distributions obtained after the cluster explodes. The mean concentration of atoms bound into clusters in a beam, the cluster size distribution, and the focal-spot diameter are found to have a weak effect on both energy and charge distributions of the ions, whereas the energy spectrum of the produced ions is determined by the mean cluster size. 相似文献
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M. Roth A. Blazevic E. Brambrink M. Geissel T. E. Cowan J. Fuchs A. Kemp H. Ruhl P. Audebert J. Cobble J. Fernandez M. Hegelich S. Letzring K. Ledingham P. McKenna R. Clarke D. Neely S. Karsch D. Habs J. Schreiber 《Hyperfine Interactions》2005,162(1-4):45-53
Intense beams of protons and heavy ions have been observed in ultra-intense laser-solid interaction experiments. Thereby,
a considerable fraction of the laser energy is transferred to collimated beams of energetic ions (e.g. up to 50 MeV protons;
100 MeV fluorine), which makes these beams highly interesting for various applications. Experimental results indicate very
short pulse duration and an excellent beam quality, leading to beam intensities in the TW range. To characterize the beam
quality and its dependence on laser parameters and target conditions, we performed experiments at several high-power laser
systems. We found a strong dependence on the target rear surface conditions allowing to tailor the ion beam by an appropriate
target design. We also succeeded in the generation of heavy ion beams by suppressing the proton amount at the target surface.
We will present recent experimental results demonstrating a transverse beam emittance far superior to accelerator-based ion
beams. Finally, we will discuss the prospect of laser-accelerated ion beams as new diagnostics in laser-solid interaction
experiements. Special fields of interest are proton radiography, electric field imaging, and relativistic electron transport
inside the target. 相似文献
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The influence of collective effects associated with transverse plasma oscillations excited by a beam of negative ions on the neutralization of the space charge due to fast ions is studied. Conditions for the dynamic deneutralization of an unstable ion beam are refined. Analytic expressions for the plasma ion density distribution and for the stationary electric field in a partially neutralized beam are obtained. The equation of motion of a beam in the self-electric field and in an external magnetic field is used to determine the effect of secondary charged particles on the transport of negative ions through the injector of a cyclotron. 相似文献
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U. Eisenbarth M. Mudrich B. Eike M. Grieser R. Grimm V. Luger T. Schätz U. Schramm D. Schwalm M. Weidemüller 《Hyperfine Interactions》2000,127(1-4):223-235
We have observed a sudden disappearance of intrabeam scattering in a laser cooled stored 9Be+ beam at the Heidelberg Test Storage Ring. The transition takes place at about 106 ions corresponding to a mean ion distance of ≃50c μm. The disappearance of IBS is accompanied by a decrease of the longitudinal
temperature by more than two orders of magnitude. At the same time, the transverse width of the ion beam shows an increase
which is limited to the diameter of the laser beam. Experimental signatures of this anomalous beam behaviour are described,
and possible interpretations are discussed.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
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Based on laser radar equations, a Doppler shift model of a laser pulse beam scattered by a rotating arbitrary convex target is reported in this paper. The boundary relations between an incident pulse beam and the detected area elements are analyzed by geometric methods. The Doppler shift characteristics of the rotating cone and cylinder are discussed and the difference between the laser pulse beam and the plane wave scattered from the same rotating target is compared accordingly. Numerical simulations show that the Doppler shift is tightly relevant to their dimensions, speeds, and so on. In the same incidence conditions, the pulse beam and plane wave have difference peak values and the same Doppler shift bandwidth. If the waist radius of the pulse beam is larger, the peak value is higher, and the Doppler shifts are proportional to the speed of the rotating target. By virtue of our theoretical model, we probe into the scattered characteristics of the Doppler shifts of a laser pulse beam, which would benefit target identification in national defense. 相似文献
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特定折射率材料及光学薄膜制备 总被引:1,自引:0,他引:1
根据太阳电池阵激光防护膜性能优化的需要,应用离子辅助电子束双源共蒸工艺方法制备了优化设计所需的特定折射率的薄膜材料并用于制备激光防护膜。测试结果显示:用该工艺方法制备的掺杂材料薄膜的折射率n=1.75,与优化设计所需数值相符;激光防护膜性能优良,太阳辐射能透过率提高6%以上,实现了对该激光防护膜性能的进一步优化。为了使该双源共蒸方法适于大面积薄膜的制备,应用均匀性挡板技术来提高该方法制备大面积薄膜的膜厚均匀性,使制备的掺杂材料薄膜在口径为400 mm时的不均匀性小于2.1%。该双源共蒸方法制备工艺简单、可靠,适于实际工程应用。薄膜性能测试结果与理论优化结果相符,达到预期优化目标。 相似文献
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H.-Th. Prinz D. Dauvergne S. Andriamonje K. Beckert M. Chevallier C. Cohen J. Dural H. Eickhoff B. Franzke H. Geissel R. Kirsch A. L'Hoir P.H. Mokler R. Moshammer F. Nickel F. Nolden J.C. Poizat H. Reich J. Remillieux F. Sanuy C. Scheidenberger D. Schmaus M. Steck Th. Stöhlker M. Toulemonde 《Hyperfine Interactions》1997,108(1-3):325-332
A cooled beam of decelerated highly-charged heavy ions is slowly extracted out of the cooler and storage ring ESR, by combining
the deceleration technique and the charge exchange extraction mode. The quality of the external ion beam is tested by a channeling
experiment. Bare Au79+ ions are injected into the ESR at an energy of 360 MeV/u, decelerated to 53 MeV/u, and finally cooled strongly in the electron
cooler. By breeding of neighboring charge state ions via radiative recombination in the electron cooler H-like ions are produced.
The H-like ion fraction is extracted out of the storage ring. This extracted Au78+ ion beam is probed by a channeling experiment measuring the extinction rate of the projectile Kα X-ray yield around the [110]
axis of a thin silicon crystal.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
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用飞行时间质谱仪和超声速脉冲分子束技术研究了紫外激光对1-萘酚(1HN)团簇的电离质谱.观测到(1HN)_n~+系列的团簇离子,且离子强度随团簇尺寸的增大而减小.电离激光的强度(在5μJ/pulse~100μJ/pulse范围内)对团簇离子强度的相对分布影响较小,说明软电离为产生团簇离子的主要过程,团簇离子的强度分布反映出电离前中性团簇的分布特征.增大电离区的进样气压可以产生更大尺寸的团簇离子,同时在(1HN)_n~+后面观测到新系列的团簇离子.这些新生离子与(H_2O)_m有关,考虑到1-萘酚团簇可以通过OH形成H键,推测该新生团簇离子通过团簇内的反应而产生. 相似文献
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A. Kellerbauer G. Bollen J. Dilling S. Henry F. Herfurth H.-J. Kluge E. Lamour D. Lunney R.B. Moore C. Scheidenberger S. Schwarz G. Sikler J. Szerypo 《Hyperfine Interactions》2001,132(1-4):507-511
With the Penning trap mass spectrometer ISOLTRAP, close to 200 nuclides have already been investigated and their masses determined
with a typical relative precision of δm/m=10−7. Recently, ISOLTRAP's beam preparation system was replaced by an RFQ ion beam cooler and buncher. The principle and the characteristics
of this new beam preparation system will be presented. It is planned to use ions of various carbon clusters C+
n
(n>1) as reference ions for mass measurements. Apart from negligible molecular binding energies, these clusters have masses
that are exact multiples of the unified atomic mass unit. This will allow ISOLTRAP to carry out absolute mass measurements
as well as to investigate possible mass-dependent systematic errors. The results of tests of the production, transport, and
trapping of such carbon clusters will be presented.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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H. Imajo S. Urabe K. Hayasaka M. Watanabe R. Hayashi 《Applied physics. B, Lasers and optics》1993,57(2):141-144
Be+ ions stored in a Penning trap were cooled by a laser beam perpendicular to the magnetic field. The cooled ions are strongly coupled and phase transitions of up to 100 ions were observed. In experiments with only a few ions stored in the trap, a stepwise decrease in fluorescence intensity was observed. All steps are of the same size and so every step is attributed to a single ion. The discrete changes in fluorescence occurred more frequently when the background pressure was increased, caused by collisions between stored ions and background neutral molecules. 相似文献
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Takeshi Kanesue 《辐射效应与固体损伤》2015,170(4):347-354
In Brookhaven National Laboratory (BNL), we have been developing laser ion sources for diverse accelerators. Tabletop Nd:YAG lasers with up to several Joules of energy are mainly used to create ablation plasmas for stable operations. The obtained charge states depend on laser power density and target species. Two types of ion extraction schemes, direct plasma injection scheme (DPIS) and conventional static extraction, are used depending on the application. We optimized and selected a suitable laser irradiation condition and a beam extraction scheme to meet the requirement of the following accelerator system. We have demonstrated to accelerate more than 5?×?1010 of C6+ ions using the DPIS. We successfully commissioned a low-charge ion beam provider to the user facilities in BNL. To achieve higher current, higher charge state and lower emittance, further studies will continue. 相似文献
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The beams of four pulsed high-power laser diodes are time-multiplexed resulting in a laser beam of high quality. A combination of polarization switches and filters forming a digital time-multiplexer is utilized to guide laser pulses produced by the individual laser diodes onto a common optical path. A resulting beam with an optical power of 10 W and a beam quality comparable with that of a single laser diode at a wavelength of 960 nm is obtained. 相似文献