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1.
Recent commissioning of the Cooler Storage Ring at the Heavy Ion Research Facility in Lanzhou enabled us to conduct high-precision mass measurements at the Institute of Modern Physics in Lanzhou (IMP). In the past few years, mass measurements were performed using the CSRe-based isochronous mass spectrometry employing the fragmentation of the energetic beams of 58Ni, 78Kr, 86Kr, and 112Sn projectiles. Masses of short-lived nuclides on both sides of the stability valley were addressed. Relative mass precision of down to 10−6 ~ 10−7 is routinely achieved. The mass values were used as an input for dedicated nuclear structure and astrophysics studies, providing for instance new insights into the rp-process of nucleosynthesis in X-ray bursts. In this contribution, we briefly review the so far conducted experiments and the main achieved results, as well as outline the plans for future experiments. 相似文献
2.
本文报导了合成109号元素的实验。用能量为4.95,5.05和5.15MeV/u 的~(58)Fe 束轰击~(209)Bi 靶,研究了全熔合产物衰变模式的特性。总辐照剂量为7×10~(17)粒子。所用的实验方法是:用静电场速度过滤器在飞行过程中分离向前方向成峰的反应产物,经过飞行时间装置后注入到位置灵敏固态探测器中,测量其动能,估算出质量、入射的时间和位置。以所有的出射粒子的能量和时间来记录很有限的反应产物发生级联α粒子和(或)自发裂变的继发衰变。在5.15 MeV/u 时的一个特别的衰变过程是:在5ms 和22ms 先分别发射两个α粒子,最后,在13s 后发生自发裂变。第一个α粒子的动能为11.10±0.04MeV。对各种可能的解释进行了详细的分析,例如纯属偶然的信号相关,转移反应产物的衰变和从能量上看允许的余核蒸发等。最后表明质量数为266的109号元素的同位素、即全熔合后的单中子蒸发道、从统计的观点看是最好的指定。本文同时也讨论了合成新元素的前景。 相似文献
3.
Brane world black holes in teleparallel theory equivalent to general relativity and their Killing vectors, energy, momentum and angular momentum 下载免费PDF全文
Gamal G.L. Nashed 《中国物理 B》2010,19(2):20401-020401
The energy--momentum tensor, which is coordinate-independent, is
used to calculate energy, momentum and angular momentum of two
different tetrad fields. Although, the two tetrad fields reproduce
the same space--time their energies are different. Therefore, a
regularized expression of the gravitational energy--momentum tensor
of the teleparallel equivalent of general relativity (TEGR), is
used to make the energies of the two tetrad fields equal. The
definition of the gravitational energy--momentum is used to
investigate the energy within the external event horizon. The
components of angular momentum associated with these space--times
are calculated. In spite of using a static space--time, we get
a non-zero component of angular momentum! Therefore, we derive
the Killing vectors associated with these space--times using the
definition of the Lie derivative of a second rank tensor in the
framework of the TEGR to make the picture more clear. 相似文献
4.
Random-injection-based two-channel chaos with enhanced bandwidth and suppressed time-delay signature by mutually coupled lasers: Proposal and numerical analysis 下载免费PDF全文
Simultaneous bandwidth(BW) enhancement and time-delay signature(TDS) suppression of chaotic lasing over a wide range of parameters by mutually coupled semiconductor lasers(MCSLs) with random optical injection are proposed and numerically investigated. The influences of system parameters on TDS suppression(characterized by autocorrelation function(ACF) and permutation entropy(PE) around characteristic time) and chaos BW are investigated. The results show that, with the increasing bias current, the ranges of parameters(detuning and injection strength) for the larger BW(> 20 GHz) are broadened considerably, while the parameter range for optimized TDS(< 0.1) is not shrunk obviously.Under optimized parameters, the system can simultaneously achieve two chaos outputs with enhanced BW(> 20 GHz)and perfect TDS suppression. In addition, the system can generate two-channel high-speed truly physical random number sequences at 200 Gbits/s for each channel. 相似文献
5.
Pressure effect study on the Ⅰ-Ⅴ property of the GaAs-based resonant tunnelling structure by photoluminescence measurement 下载免费PDF全文
This paper discusses the Ⅰ-Ⅴ property of the GaAs-based resonant tunnelling structure(RTS) under external uniaxial pressure by photoluminescence studies.Compressive pressure parallel to the [110] direction,whose value is determined by Hooke's law,is imposed on the sample by a helix micrometer.With the increase of the applied external uniaxial compressive pressure,the blue shift and splitting of the luminescence peaks were observed,which have some influence on the I-V curve of RTS from the point of view of the energy gap,and the splitting became more apparent with applied pressure.Full width at half maximum broadening could also be observed. 相似文献
6.
We discuss quantum fluctuation in excited states(named thermo number states) of mesoscopic LC circuits at a finite temperature.By introducing the coherent thermo state into the thermo field dynamics pioneered by Umezawa and using the natural representation of thermo squeezing operator we can concisely derive the fluctuation.The result shows that the noise becomes larger when either temperature or the excitation number increases. 相似文献
7.
匀速圆周运动是曲线运动章节的教学重点.现行高中及中专教材均以两节的篇幅来讨论这种运动.一节是建立匀速圆周运动的概念,引入描述匀速圆周运动快慢的4个量,即周期(T)、频率(v)、角速度(ω)、线速度(v),并讨论这4个量的关系.另一节则从受力的角度讨论圆周运动的向心力及向心加速度.共涉及6个量.由于这6个量之间彼此存在一定的关系,这就使圆周运动具有较多的公式.如果学生能熟练掌握这些公式以及它们之间相互关系的规律,解题就能 相似文献
8.
Theoretical investigation of band-gap and mode characteristics of anti-resonance guiding photonic crystal fibres 下载免费PDF全文
With the full-vector plane-wave method (FVPWM) and the full-vector beam propagation method (FVBPM),the dependences of the band-gap and mode characteristics on material index and cladding structure parameter in antiresonance guiding photonic crystal fibres (ARGPCFs) are sufficiently analysed.An ARGPCF operating in the nearinfrared wavelength is shown.The influences of the high index cylinders,glass interstitial apexes and silica structure on the characteristics of band-gaps and modes are deeply investigated.The equivalent planar waveguide theory is used for analysing such an ARGPCF filled by the isotropic materials,and the resonance and the anti-resonance characteristics can be well predicted. 相似文献
9.
Using the technique of integration within an ordered product of operators,we find a new kind of coherent-entangled state(CES),which exhibits both coherent and entangled state properties.The set of CESs makes up a complete and partly nonorthogonal representation.Using a beam splitter,we propose a simple experimental scheme to produce the CES.Finally,we present some applications of CESs in quantum optics. 相似文献
10.
Function projective synchronization between fractional-order chaotic systems and integer-order chaotic systems 下载免费PDF全文
This paper investigates the function projective synchronization between fractional-order chaotic systems and integer-order chaotic systems using the stability theory of fractional-order systems. The function projective synchronization between three-dimensional (3D) integer-order Lorenz chaotic system and 3D fractional-order Chen chaotic system are presented to demonstrate the effectiveness of the proposed scheme. 相似文献
11.
By means of a new force sensor based on optical beam deflection (OBD), the mechanical effects of laser-matter interaction underwater at different incident laser energy are investigated in detail. The experimental results show that a target underwater is impacted in turn by laser-plasma ablation force and high-speed liquid-jet impulse induced by bubbles collapse in the vicinity of a solid boundary. Furthermore, the amplitudes of the two forces increase monotonously with laser energy. According to the ablation force detected by the experiment and the theoretical relationship between laser intensity and ablation pressure, the value of liquid-jet impact against a solid boundary can be easily obtained. In addition, based on the model of a collapsing bubble, some characteristic parameters, such as the liquid-jet impact velocity, the maximum bubble radius, the bubble energy can also be obtained at different laser energy, which are valuable in the corresponding research fields. 相似文献
12.
通过自行研制的光纤传感器对不同黏度液体中材料靶后的力学作用进行研究,获得了液体黏度变化对等离子体烧蚀力、射流冲击力及空泡生存周期的影响. 实验结果表明:液体黏度相同时,靶材所受冲击力幅值随作用激光能量的增加单调上升;液体黏度增加时,靶材所受的冲击力减小,靶材的空化空蚀程度亦减小;受液体黏度增大的影响,空泡膨胀或收缩过程减缓,相应的生存周期也增大. 此外,对空泡溃灭周期公式进行修正, 结果表明修正后的理论估算值与实验值的一致性较好. 相似文献
13.
Effect of surface tension on a liquid-jet produced by the collapse of a laser-induced bubble against a rigid boundary 总被引:1,自引:0,他引:1
The effect of surface tension on the behavior of a liquid-jet is investigated experimentally by means of a fiber-coupled optical beam deflection (OBD) technique. It is found that a target under water is impacted in turn by a laser-plasma ablation force and by a high-speed liquid-jet impulse induced by bubble collapse in the vicinity of a rigid boundary. The liquid-jet impact is found to be the main damage mechanism in cavitation erosion. Furthermore, the liquid-jet increases monotonously with surface tension, so cavitation erosion rises sharply with increasing surface tension. Surface tension also reduces bubble collapse duration. From the experimental results and the modified Rayleigh theory, the maximum bubble radius is obtained and it is found to reduce with increasing surface tension. 相似文献
14.
Experimental investigation of the impact on nearby solid boundary during laser-generated bubble collapse 下载免费PDF全文
Cavitation damage has been considered as being responsible for many effects in hydraulic machinery and biological medicine. In order to better understand the cavity interaction with nearby solid surfaces, the impact loading induced by the high-speed liquid-jet and subsequent jet flow during the final stage of the bubble collapse in a static fluid is investigated by focusing a Q-switched pulsed laser into water. By means of a new method based on a fibre-coupling optical beam deflection technique, a detailed experimental study has been made to clarify the relationship of the impact pressure against a solid boundary as a function of the dimensionless γ that is generally used to describe the bubble dynamics with its definition γ= s/R_{max}(R_{max} being the maximum bubble radius and s denoting the distance of the cavity inception from the boundary). The experimental results are shown that for γ in the range of about 0.67 to 0.95 with a pulsed laser energy 230mJ, the transient pressure applied on the solid surface is maximum; while for γ>1 or γ<0.67, it is gradually decreased. By combination of our experimental results with the other work that detected the acoustic emission during the bubble collapse at different γ, it is concluded that in this range of 0.67-0.95, the destructive effect due to a liquid-jet and the following jet flow impact actually outweighs the well-known effect of shock wave emission and plays a vital role during the cavitation bubble collapse. 相似文献
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Pulse chirping effect on controlling the transverse cavity oscillations in nonlinear bubble regime 下载免费PDF全文
The propagation of an intense laser pulse in an under-dense plasma induces a plasma wake that is suitable for the acceleration of electrons to relativistic energies. For an ultra-intense laser pulse which has a longitudinal size shorter than the plasma wavelength, λp, instead of a periodic plasma wave, a cavity free from cold plasma electrons, called a bubble, is formed behind the laser pulse. An intense charge separation electric field inside the moving bubble can capture the electrons at the base of the bubble and accelerate them with a narrow energy spread. In the nonlinear bubble regime, due to localized depletion at the front of the pulse during its propagation through the plasma, the phase shift between carrier waves and pulse envelope plays an important role in plasma response. The carrier–envelope phase(CEP) breaks down the symmetric transverse ponderomotive force of the laser pulse that makes the bubble structure unstable. Our studies using a series of two-dimensional(2D) particle-in-cell(PIC) simulations show that the frequency-chirped laser pulses are more effective in controlling the pulse depletion rate and consequently the effect of the CEP in the bubble regime. The results indicate that the utilization of a positively chirped laser pulse leads to an increase in rate of erosion of the leading edge of the pulse that rapidly results in the formation of a steep intensity gradient at the front of the pulse. A more unstable bubble structure, the self-injections in different positions, and high dark current are the results of using a positively chirped laser pulse. For a negatively chirped laser pulse, the pulse depletion process is compensated during the propagation of the pulse in plasma in such a way that results in a more stable bubble shape and therefore, a localized electron bunch is produced during the acceleration process. As a result, by the proper choice of chirping, one can tune the number of self-injected electrons, the size of accelerated bunch and its energy spectrum to the values required for practical applications. 相似文献
19.
Nanosecond pulsed laser ablation of silicon in liquids 总被引:2,自引:0,他引:2
R. Karimzadeh J. Zamir Anvari N. Mansour 《Applied Physics A: Materials Science & Processing》2009,94(4):949-955
Laser fluence and laser shot number are important parameters for pulse laser based micromachining of silicon in liquids. This
paper presents laser-induced ablation of silicon in liquids of the dimethyl sulfoxide (DMSO) and the water at different applied
laser fluence levels and laser shot numbers. The experimental results are conducted using 15 ns pulsed laser irradiation at
532 nm. The silicon surface morphology of the irradiated spots has an appearance as one can see in porous formation. The surface
morphology exhibits a large number of cavities which indicates as bubble nucleation sites. The observed surface morphology
shows that the explosive melt expulsion could be a dominant process for the laser ablation of silicon in liquids using nanosecond
pulsed laser irradiation at 532 nm. Silicon surface’s ablated diameter growth was measured at different applied laser fluences
and shot numbers in both liquid interfaces. A theoretical analysis suggested investigating silicon surface etching in liquid
by intense multiple nanosecond laser pulses. It has been assumed that the nanosecond pulsed laser-induced silicon surface
modification is due to the process of explosive melt expulsion under the action of the confined plasma-induced pressure or
shock wave trapped between the silicon target and the overlying liquid. This analysis allows us to determine the effective
lateral interaction zone of ablated solid target related to nanosecond pulsed laser illumination. The theoretical analysis
is found in excellent agreement with the experimental measurements of silicon ablated diameter growth in the DMSO and the
water interfaces. Multiple-shot laser ablation threshold of silicon is determined. Pulsed energy accumulation model is used
to obtain the single-shot ablation threshold of silicon. The smaller ablation threshold value is found in the DMSO, and the
incubation effect is also found to be absent. 相似文献
20.
S. V. Starikov A. Ya. Faenov T. A. Pikuz I. Yu. Skobelev V. E. Fortov S. Tamotsu M. Ishino M. Tanaka N. Hasegawa M. Nishikino T. Kaihori T. Imazono M. Kando T. Kawachi 《Applied physics. B, Lasers and optics》2014,116(4):1005-1016
Experimental and theoretical investigations of aluminum (Al) and gold (Au) surface modification by soft X-ray laser pulse are presented. Well-polished samples of Al and Au are irradiated by ps-duration pulse with wavelength of 13.9 nm at the energy range of 24–72 nJ. Differences in the melting and the ablation processes for those materials are observed. It is shown that at low laser pulse energy, the nanoscale ripples on the surface may be induced by melting without following ablation. In that case, the nanoscale changes in the surface are caused by splash of molten metal under gradient of fluence. At higher laser pulse energy, the ablation process occurs and craters are formed on the surface. However, the melting determines the size of the modified surface at all ranges of the laser energies. For interpretation of experimental results, the atomistic simulations of melting and ablation processes in Al and Au are provided. The calculated threshold fluencies for melting and ablation are well consistent with measured ones. 相似文献