Precision Mass Measurements of Short-lived Nuclides at the Heavy-ion Storage Ring in Lanzhou

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.     

由58Fe 和209Bi 熔合后的相关衰变过程得到的109号元素的证据

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。     

Impact of counter-rotating-wave term on quantum heat transfer and phonon statistics in nonequilibrium qubit–phonon hybrid system

Counter-rotating-wave terms(CRWTs)are traditionally viewed to be crucial in open small quantum systems with strong system–bath dissipation.Here by exemplifying in a nonequilibrium qubit–phonon hybrid model,we show that CRWTs can play the significant role in quantum heat transfer even with weak system–bath dissipation.By using extended coherent phonon states,we obtain the quantum master equation with heat exchange rates contributed by rotating-waveterms(RWTs)and CRWTs,respectively.We find that including only RWTs,the steady state heat current and current fluctuations will be significantly suppressed at large temperature bias,whereas they are strongly enhanced by considering CRWTs in addition.Furthermore,for the phonon statistics,the average phonon number and two-phonon correlation are nearly insensitive to strong qubit–phonon hybridization with only RWTs,whereas they will be dramatically cooled down via the cooperative transitions based on CRWTs in addition.Therefore,CRWTs in quantum heat transfer system should be treated carefully.     

Properties of ground state and anomalous quantum fluctuations in one-dimensional polaron-soliton systems—the effects of electron-two-phonon interaction and non-adiabatic quantum correlations

Based on the Holstein model Hamiltonian of one-dimensional molecular crystals, by making use of the expansion approach of the correlated squeezed-coherent states of phonon instead of the two-phonon coherent state expansion scheme, the properties of the ground state and the anomalous quantum fluctuations are investigated in a strongly coupled electron-phonon system with special consideration of the electron-two-phonon interaction. The effective renormalization (αi) of the displacement of the squeezed phonons with the effect of the squeezed-coherent states of phonon and both the electron-displaced phonon and the polaron-squeezed phonon correlations have been combined to obtain the anomalous quantum fluctuations for the corrections of the coherent state. Due to these non-adiabatic correlations, the effective displacement parameter αi is larger than the ordinary parameter α (0) i . In comparison with the electron-one-phonon interaction (g) corrected as αig, we have found the electron-two-phonon interaction (g1) corrected as αi2 g1 is enhanced significantly. For this reason, the ground state energy (E(2) 0 ) contributed by the electron-two-phonon interaction is more negative than the single-phonon case (E(1) 0 ) and the soliton solution is more stable. At the same time, the effects of the electron-two-phonon interaction greatly increase the polaron energy and the quantum fluctuations. Furthermore, in a deeper level, we have considered the effect of the polaron-squeezed phonon correlation (f-correlation). Since this correlation parameter f > 1, this effect will strengthen the electron-one and two-phonon interactions by fαig and f2αi2 g1, respectively. The final results show that the ground state energy and the polaron energy will appear more negative further and the quantum fluctuations will gain further improvement.     

Investigation on performance of all optical buffer with large dynamical delay time based on cascaded double loop optical buffers

Optical buffers are critical for optical signal processing in future optical packet-switched networks. In this paper, a theoretical study as well as an experimental demonstration on a new optical buffer with large dynamical delay time is carried out based on cascaded double loop optical buffers (DLOBs). It is found that pulse distortion can be restrained by a negative optical control mode when the optical packet is in the loop. Noise analysis indicates that it is feasible to realise a large variable delay range by cascaded DLOBs. These conclusions are validated by the experiment system with 4-stage cascaded DLOBs. Both the theoretical simulations and the experimental results indicate that a large delay range of 1-9999 times the basic delay unit and a fine granularity of 25 ns can be achieved by the cascaded DLOBs. The performance of the cascaded DLOBs is suitable for the all optical networks.     

Generalized unscented Kalman filtering based radial basis function neural network for the prediction of ground radioactivity time series with missing data

On the assumption that random interruptions in the observation process are modeled by a sequence of independent Bernoulli random variables, we firstly generalize two kinds of nonlinear filtering methods with random interruption failures in the observation based on the extended Kalman filtering (EKF) and the unscented Kalman filtering (UKF), which were shortened as GEKF and GUKF in this paper, respectively. Then the nonlinear filtering model is established by using the radial basis function neural network (RBFNN) prototypes and the network weights as state equation and the output of RBFNN to present the observation equation. Finally, we take the filtering problem under missing observed data as a special case of nonlinear filtering with random intermittent failures by setting each missing data to be zero without needing to pre-estimate the missing data, and use the GEKF-based RBFNN and the GUKF-based RBFNN to predict the ground radioactivity time series with missing data. Experimental results demonstrate that the prediction results of GUKF-based RBFNN accord well with the real ground radioactivity time series while the prediction results of GEKF-based RBFNN are divergent.     

The NUBASE2020 evaluation of nuclear physics properties

The NUBASE2020 evaluation contains the recommended values of the main nuclear physics properties for all nuclei in their ground and excited,isomeric(T1/2≥100 ns)states.It encompasses all experimental data published in primary(journal articles)and secondary(mainly laboratory reports and conference proceedings)references,together with the corresponding bibliographical information.In cases where no experimental data were available for a particular nuclide,trends in the behavior of specific properties in neighboring nuclei were examined and estimated values are proposed.Evaluation procedures and policies that were used during the development of this evaluated nuclear data library are presented,together with a detailed table of recommended values and their uncertainties.     

毛细现象公式的导出

液体表面分子间的吸引力、液体表面的分子有一种使其面积缩成最小的力,或称一种抵抗表面积扩张的力,此力称“表面张力”．液体表面是指液体与空气或其他液体相接触的自由面．若不指明,即可认为相对于空气而言．表面张力的大小与接触面的物质有密切关系．此外,表面张力还与温度有关,温度越高,表面张力越小．表面张力的方向总是与液面相切,与分界线相垂直．若在液面作一长为L的直线,将液面分成两部分,这两部分之间的相互牵引力为F,即表面张力F=σL．其中σ为液体表面张力系数．单位为N/m．由于表面张力的作用,液滴表面有收缩到最小的趋势,而使液滴成近似球形的状态．     

Lump,lumpoff and predictable rogue wave solutions to a dimensionally reduced Hirota bilinear equation

We study a simplified(3+1)-dimensional model equation and construct a lump solution for the special case of z=y using the Hirota bilinear method.Then,a more general form of lump solution is constructed,which contains more arbitrary autocephalous parameters.In addition,a lumpoff solution is also derived based on the general lump solutions and a stripe soliton.Furthermore,we figure out instanton/rogue wave solutions via introducing two stripe solitons.Finally,one can better illustrate these propagation phenomena of these solutions by analyzing images.     

Arbitrary full-state hybrid projective synchronization for chaotic discrete-time systems via a scalar signal

In this paper we present a new projective synchronization scheme,where two chaotic(hyperchaotic) discretetime systems synchronize for any arbitrary scaling matrix.Specifically,each drive system state synchronizes with a linear combination of response system states.The proposed observer-based approach presents some useful features:i) it enables exact synchronization to be achieved in finite time(i.e.,dead-beat synchronization);ii) it exploits a scalar synchronizing signal;iii) it can be applied to a wide class of discrete-time chaotic(hyperchaotic) systems;iv) it includes,as a particular case,most of the synchronization types defined so far.An example is reported,which shows in detail that exact synchronization is effectively achieved in finite time,using a scalar synchronizing signal only,for any arbitrary scaling matrix.     

介质窗横向电磁场分布下的次级电子倍增效应

本文利用自编P3D3V PIC程序, 数值研究了BJ32矩波导传输TE₁₀模式高功率微波在介质窗内、 外表面引发的次级电子倍增过程, 给出了次级电子3维空间位置分布特征、介质窗表面法向静电场分布规律以及电子数密度分布特性. 模拟结果表明: 对于介质窗内侧, 微波强场区域率先进入次级电子倍增过程; 而对于介质窗外侧, 则是微波弱场区域优先进入次级电子倍增过程. 形成机理可以解释为: 微波坡印廷矢量方向与介质窗外表面法向相同而与内表面法向相反, 内侧漂移运动导致强场区域电子易于被推回表面, 有利于次级电子倍增优先形成; 外侧漂移运动导致强场区域电子易于被推离表面, 不利于次级电子倍增形成. 准3维模型相对1维模型: 介质窗内侧次级电子倍增过程中, 次级电子倍增进入饱和时间长、饱和次级电子数目少、平均电子能量高、 入射微波功率低、沉积功率低; 介质窗外侧次级电子倍增过程中, 次级电子倍增进入饱和时间短、饱和次级电子数目少、平均电子能量低、 入射微波功率低、沉积功率低. 沉积功率与入射微波功率比值与微波模式、强度及介质窗内外侧表面关系不大, 准3维和1维模型计算结果均在1%–2%左右水平. 关键词： 高功率微波 介质表面次级电子倍增 粒子模拟 横向电磁场分布     

Numerical studies of atmospheric pressure glow discharge controlled by a dielectric barrier between two coaxial electrodes

The glow discharge in pure helium at atmospheric pressure, controlled by a dielectric barrier between coaxial electrodes, is investigated based on a one-dimensional self-consistent fluid model. By solving the continuity equations for electrons, ions, and excited atoms, with the current conservation equation and the electric field profile, the time evolution of the discharge current, gas voltage and the surface density of charged particles on the dielectric barrier are calculated. The simulation results show that the peak values of the discharge current, gas voltage and electric field in the first half period are asymmetric to the second half. When the current reaches its positive or negative maximum, the electric field profile, and the electron and ion densities represent similar properties to the typical glow discharge at low pressures. Obviously there exist a cathode fall, a negative glow region, and a positive column. Effects of the barrier position in between the two coaxial electrodes and the discharge gap width on discharge current characteristics are also analysed. The result indicates that, in the case when the dielectric covering the outer electrode only, the gas is punctured earlier during the former half period and later during the latter half period than other cases, also the current peak value is higher, and the difference of pulse width between the two half periods is more obvious. On reducing the gap width, the multiple current pulse discharge happens.     

Discharges and mechanoelectrical phenomena in charged glasses

Conclusions In high-resistance solid dielectrics (with resistances of 10¹² · cm or higher, when they are irradiated with electron beams, spontaneous electric discharges are observed while the irradiation is occurring. The discharges occur at defects in the surface and develop in the layer within which the charged particles are distributed.When the charged particles are distributed in the surface or near-surface layer of the dielectric, the discharge may be initiated close to the charged surface by a grounded metal needle, even some time after the irradiation. After long storage and self-dis charge of the surface layer of the irradiated dielectric or compensation of the surface charge, discharge of the charge stored in the depth of the dielectric can occur by scratching the surface or pricking it with a needle. When the charge lies deep inside the dielectric, a brush discharge occurs when a strong shock is applied to the surface of the dielectric using a grounded needle.In all the above cases initiation of an electric discharge in the solid dielectric occurred by mechanoelectrical phenomena of direct conversion of mechanical energy into electrical energy with a high field strength. These phenomena occur in solid dielectrics with a defect structure.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 40–46, February, 1977.     

Forming concentric double-emulsion droplets using electric fields

Double-emulsion droplets may be assembled into highly concentric shells using a uniform AC electric field to induce dipole/dipole interactions. The resulting force centers the inner droplet with respect to the outer shell if the outer droplet has a higher dielectric constant than the ambient, suspending liquid. The dielectric constant of the inner droplet does not influence this condition. Applying an electric field >10⁴ V_rms/m achieves centering of approximately 3–6 mm diameter droplets suspended in ～10 centipoise liquids within ～60 s. If the outer shell is electrically conductive, the effect depends strongly on frequency. In the case of the monomer-containing liquids requisite to forming foam shells for laser target fabrication, the electrical field frequency must be ～10 MHz or higher. Because of very stringent requirements imposed on the concentricity and sphericity of laser targets, electric field induced droplet distortion must be minimized. Consequently, the liquid constituents must be matched in density to ～0.1%.     

不同电极结构下大气压Ar等离子体射流的流体模拟研究

采用二维轴对称流体模型对比研究了3种不同电极结构下大气压Ar等离子体射流的基本特性。第一种是带绝缘介质的针电极结构（电场方向和气体流方向平行）,第二种是在第一种电极结构的介质管外增加一个垂直气流方向的接地环电极,第三种是不带绝缘介质的裸针电极结构。研究结果表明,接地环电极的引入对介质管内外的射流传播影响不同。在介质管内,接地环电极使管内表面附近的径向电场增加,电子密度升高,射流传播速度加快,但对中心轴附近的电场和电子密度影响很小;然而在介质管外,接地环电极的引入导致轴向和径向电场均减小,从而引起射流的传播长度减小,射流通道径向收缩。通过带绝缘介质的针电极和裸针电极结构的对比研究发现,保持其他条件不变,去掉包裹在针电极上的介质后,由于等离子体电势升高,电场增加,射流的传播长度几乎增加一倍,峰值电子密度增加近一个数量级,而且在整个射流通道内电子密度都保持相对高的值。此外,对3种电极结构下的主要活性粒子的产生和输运进行了比较研究。     

两种外磁场形式对介质面次级电子倍增的抑制

利用自编1D3V PIC程序,数值研究了不同外加磁场方式对次级电子倍增抑制的物理过程,给出了次级电子数目、平均能量、密度、运动轨迹、渡越时间、介质表面静电场及沉积功率等物理量时空分布关系。模拟结果表明:不同方向外加磁场抑制次级电子倍增的机理有所不同。轴向外加磁场利用电子回旋运动干扰微波电场对电子加速过程,使其碰壁能量降低以达到抑制二次电子倍增的效果;横向外加磁场利用电子回旋漂移过程中,电子半个周期被推离介质表面（不发生次级电子倍增）,半个周期被推回介质表面（降低电子碰撞能量）的作用机理,达到抑制二次电子倍增的效果。讨论了横向磁场在回旋共振下,电子回旋同步加速导致回旋半径增大,电子能量持续增加的特殊过程。两种外加磁场方式都可以通过增加磁场达到进一步抑制次级电子倍增的目的。轴向外加磁场加载容易,但对磁场要求较高;横向外加磁场需要磁场较低,但加载较为困难。     

介质材料二次电子发射特性对微波击穿的影响

以介质填充的平行板放电结构为例,本文主要研究了介质填充后微波低气压放电和微放电的物理过程.为了探究介质材料特性对微波低气压放电和微放电阈值的影响,本文采用自主研发的二次电子发射特性测量装置,测量了7种常见介质材料的二次电子发射系数和二次电子能谱.依据二次电子发射过程中介质表面正带电的稳定条件,计算了介质材料稳态表面电位与二次电子发射系数以及能谱参数的关系.在放电结构中引入与表面电位相应的等效直流电场后,依据电子扩散模型和微放电中电子谐振条件,分别探讨了介质表面稳态表面电位的大小对微波低气压放电和微放电阈值的影响.结果表明,介质材料的二次电子发射系数以及能谱参数越大,介质材料的稳态表面电位也越大,对应的微波低气压放电和微放电阈值也越大.所得结论对于填充介质的选择有一定的理论指导价值.     

高能电子辐射下聚四氟乙烯深层充电特性

介质深层充放电现象是诱发航天器异常故障的重要因素之一.分析了高能电子辐射下介质内部电荷沉积、能量沉积特性和电导特性,考虑了真空与介质界面电荷对电场分布的影响,建立了介质二维深层充电的物理模型,并基于有限元方法实现了数值计算.计算了高能电子辐射下聚四氟乙烯的深层充电特性.结果表明:真空环境下,介质的表面存在较弱的反向电场,随着介质深度增大,电场减小至零,随后逐渐增大,最大值出现在靠近接地附近,但在接地点,电场存在小幅降低.分析了不同辐射时间下(1 h,1 d,10 d和30 d),介质内部最大电位和最大电场的时空演变特性.随着辐射时间的增加,最大电位由-128V增加至-7.9×104V,最大电场由2.83×105V·m-1增加至1.76×108V·m-1.讨论了入射电子束流密度对最大电场的影响,典型空间电子环境(1×10-10A·m-2)下,电子辐照10 d时,介质内部最大电场为2.95×106V·m-1.而恶劣空间电子环境(2×10-8A·m-2)下,电子辐射42 h,介质内部最大电场即达到108V·m-1,超过材料击穿阈值(约为108V·m-1),极易发生放电现象.该物理模型和数值方法可以作为航天器复杂部件多维电场仿真的研究基础.     

Refractive index dependent local electric field enhancement in cylindrical gold nanohole

We report on the local electric field characters in a long cylindrical gold nanohole. Theoretical calculation results based on quasi-static model show that the local environmental dielectric constant dependent electric field intensity and field distribution in the gold nanohole show quite unique properties, different from those in the thin gold nanotube. Because of the thick gold wall, no plasmon hybridization exists. So there is only one resonance frequency taking place, and the intense local field has been focused into the gold nanohole. Our main finding is that, the local field in the nanohole is largely dependent on the inner hole refractive index and outer environmental refractive index. The competition between inner hole and outer polarization leads to a non-monotonic change of the local field intensity with increasing the dielectric constant of the nanohole. This refractive index controlled local field enhancement in cylindrical gold nanohole presents a potential for tunable surface-enhanced fluorescence and novel nano-optical biosensing applications.     

介质阻挡均匀大气压辉光放电数值模拟研究

通过数值求解一维电子、离子连续性方程和动量方程，以及电流连续性方程，计算了氦气介 质阻挡大气压辉光放电电子、离子密度和电场在放电空间的时空分布，以及放电电流密度和 绝缘介质板充电电荷密度随时间的变化. 分析讨论所加电压频率、幅值及介质板性质等对均 匀大气压辉光放电性质的影响. 当外加电压频率足够高时，大量离子被俘获在放电空间，空 间电荷场又引起足够多的电子滞留在放电空间. 这些种子电子使得在大气压下发生汤森放电 ，放电空间结构类似于低气压辉光放电，即存在明显的阴极位降区、负辉区、法拉第暗区和 等离子体正柱 关键词： 大气压辉光放电 介质阻挡 数值模拟 等离子体