Physics-embedded machine learning search for Sm-doped PMN-PT piezoelectric ceramics with high performance

Pb(Mg_(1/3)Nb_(2/3))O_(3)–PbTiO_(3)(PMN-PT)piezoelectric ceramics have excellent piezoelectric properties and are used in a wide range of applications.Adjusting the solid solution ratios of PMN/PT and different concentrations of elemental doping are the main methods to modulate their piezoelectric coefficients.The combination of these controllable conditions leads to an exponential increase of possible compositions in ceramics,which makes it not easy to extend the sample data by additional experimental or theoretical calculations.In this paper,a physics-embedded machine learning method is proposed to overcome the difficulties in obtaining piezoelectric coefficients and Curie temperatures of Sm-doped PMN-PT ceramics with different components.In contrast to all-data-driven model,physics-embedded machine learning is able to learn nonlinear variation rules based on small datasets through potential correlation between ferroelectric properties.Based on the model outputs,the positions of morphotropic phase boundary(MPB)with different Sm doping amounts are explored.We also find the components with the best piezoelectric property and comprehensive performance.Moreover,we set up a database according to the obtained results,through which we can quickly find the optimal components of Sm-doped PMN-PT ceramics according to our specific needs.

High energy density physics with intense ion beams

We review the development of High Energy Density Physics(HEDP)with intense heavy ion beams as a tool to induce extreme states of matter.The development of this field connects intimately to the advances in accelerator physics and technology.We will cover the generation of intense heavy ion beams starting from the ion source and follow the acceleration process and transport to the target.Intensity limitations and potential solutions to overcome these limitations are discussed.This is exemplified by citing examples from existing machines at the Gesellschaft fur Schwerionenforschung(GSI-Darmstadt),the Institute of Theoretical and Experimental Physics in Moscow(ITEP-Moscow),and the Institute of Modern Physics(IMP-Lanzhou).Facilities under construction like the FAIR facility in Darmstadt and the High Intensity Accelerator Facility(HIAF),proposed for China will be included.Developments elsewhere are covered where it seems appropriate along with a report of recent results and achievements.

A 5.12-GHz LC-based phase-locked loop for silicon pixel readouts of high-energy physics

There is an urgent need for high-quality and high-frequency clock generators for high-energy physics experiments.The transmission data rate exceeds 10 Gbps for a single channel in future readout electronics of silicon pixel detectors.Others,such as time measurement detectors,require a high time resolution based on the time-to-digital readout architecture.A phase-locked loop(PLL)is an essential and broadly used circuit in these applications.This study presents an application-specific integrated circuit of a low-jitter,low-power LC-tank that is PLL fabricated using 55-nm CMOS technology.It includes a 3rd-order frequency synthesis loop with a programmable bandwidth,a divide-by-2 pre-scaler,standard low-voltage differential signaling interfaces,and a current mode logic(CML)driver for clock transmissions.All the d-flip-flop dividers and phase-frequency detectors are protected from single-event upsets using the triple modular redundancy technique.The proposed VCO uses low-pass filters to suppress the noise from bias circuits.The tested LC-PLL covers a frequency locking range between 4.74 GHz and 5.92 GHz with two sub-bands.The jitter measurements of the frequency-halved clock(2.56 GHz)are less than 460 fs and 0.8 ps for the random and deterministic jitters,respectively,and a total of 7.5 ps peak-to-peak with a bit error rate of 10^(-12).The random and total jitter values for frequencies of 426 MHz and 20 MHz are less than 1.8 ps and 65 ps,respectively.The LC-PLL consumed 27 mW for the core and 73.8 mW in total.The measured results nearly coincided with the simulations and validated the analyses and tests.

Biodegradable and flexible i-carrageenan based RRAM with ultralow power consumption

Transient memories,which can physically disappear without leaving traceable remains over a period of normal operation,are attracting increasing attention for potential applications in the fields of data security and green electronics.Resistive random access memory(RRAM)is a promising candidate for next-generation memory.In this context,biocompatible l-carrageenan(l-car),extracted from natural seaweed,is introduced for the fabrication of RRAM devices(Ag/l-car/Pt).Taking advantage of the complexation processes between the functional groups(C–O–C,C–O–H,et al.)and Ag metal ions,a lower migration barrier of Ag ions and a high-speed switching(22.2 ns for SET operation/26 ns for RESET operation)were achieved,resulting in an ultralow power consumption of 56 fJ.And the prepared Ag/l-car/Pt RRAM devices also revealed the capacities of multilevel storage and flexibility.In addition,thanks to the hydrophilic groups of l-car molecule,the RRAM devices can be rapidly dissolved in deionized(DI)water within 13 minutes,showing excellent transient characteristics.This work demonstrates that l-car based RRAM devices have great potential for applications in secure storage applications,flexible electronics and transient electronics.

Effectively modulating spatial vortex four-wave mixing in a diamond atomic system

Due to the spatial characteristics of orbital angular momentum,vortex fields can be applied in the fields of quantum storage and quantum information.We study the realization of spatially modulated vortex fields based on four-wave mixing in a four-level atomic system with a diamond structure.The intensity and spiral phase of the vortex field are effectively transferred to the generated four-wave mixing field.By changing the detuning of the probe field,the phase and intensity of the generated vertex four-wave mixing field can be changed.When the probe field takes a large detuning value,the spatial distribution of the intensity and phase of the vertex four-wave mixing field can be effectively tuned by adjusting the Rabi frequency or detuning value of the coupled field.At the same time,we also provide a detailed explanation based on the dispersion relationship,and the results agree well with our simulation results.

Hole-Doped Nonvolatile and Electrically Controllable Magnetism in van der Waals Ferroelectric Heterostructures

Electrical control of magnetism in van der Waals semiconductors is a promising step towards development of two-dimensional spintronic devices with ultralow power consumption for processing and storing information.Here, we propose a design for two-dimensional van der Waals heterostructures(vdWHs) that can host ferroelectricity and ferromagnetism simultaneously under hole doping. By contacting an In Se monolayer and forming an InSe/In_(2)Se_(3) vd WH, the switchable built-in electric field from the reversible out-of-plane polarization enables robust control of the band alignment. Furthermore, switching between the two ferroelectric states(P_↑ and P_↓)of hole-doped In_(2)Se_(3) with an external electric field can interchange the ON and OFF states of the nonvolatile magnetism. More interestingly, doping concentration and strain can effectively tune the magnetic moment and polarization energy. Therefore, this provides a platform for realizing multiferroics in ferroelectric heterostructures,showing great potential for use in nonvolatile memories and ferroelectric field-effect transistors.

The energy response of LaBr_(3)(Ce),LaBr_(3)(Ce,Sr),and NaI(Tl)crystals for GECAM

The GECAM series of satellites utilizes LaBr_(3)(Ce),LaBr_(3)(Ce,Sr),and NaI(Tl)crystals as sensitive materials for gamma-ray detectors(GRDs).To investigate the nonlinearity in the detection of low-energy gamma rays and address the errors in the calibration of the E-C relationship,comprehensive tests and comparative studies of the three aforementioned crystals were conducted using Compton electrons,radioactive sources,and mono-energetic X-rays.The nonlinearity test results of the Compton electrons and X-rays demonstrated substantial differences,with all three crystals presenting a higher nonlinearity for X/-rays than for Compton electrons.Despite the LaBr_(3)(Ce)and LaBr_(3)(Ce,Sr)crystals having higher absolute light yields,they exhibited a noticeable nonlinear decrease in the light yield,especially at energies below 400 keV.The NaI(Tl)crystal demonstrated an"excess"light output in the 6-200 keV range,reaching a maximum"excess"of 9.2%at 30 keV in the X-ray testing and up to 15.5%at 14 keV during Compton electron testing,indicating a significant advantage in the detection of low-energy gamma rays.Furthermore,we explored the underlying causes of the observed nonlinearity in these crystals.This study not only elucidates the detector responses of GECAM,but also initiates a comprehensive investigation of the nonlinearity of domestically produced lanthanum bromide and sodium iodide crystals.

High-performance GaSb planar PN junction detector

This paper examines GaSb short-wavelength infrared detectors employing planar PN junctions. The fabrication was based on the Zn diffusion process and the diffusion temperature was optimized. Characterization revealed a 50% cut-off wavelength of 1.73 μm, a maximum detectivity of 8.73 × 10^(10) cm·Hz^(1/2)/W, and a minimum dark current density of 1.02 × 10^(-5) A/cm^(2).Additionally, a maximum quantum efficiency of 60.3% was achieved. Subsequent optimization of fabrication enabled the realization of a 320 × 256 focal plane array that exhibited satisfactory imaging results. Remarkably, the GaSb planar detectors demonstrated potential in low-cost short wavelength infrared imaging, without requiring material epitaxy or deposition.

Mapping the antiparallel aligned domain rotation by microwave excitation

The evolution process of magnetic domains in response to external fields is crucial for the modern understanding and application of spintronics.In this study,we investigated the domain rotation in stripe domain films of varying thicknesses by examining their response to microwave excitation in four different orientations.The resonance spectra indicate that the rotation field of stripe domain film under an applied magnetic field approaches the field where the resonance mode of sample changes.The saturation field of the stripe domain film corresponds to the field where the resonance mode disappears when measured in the stripe direction parallel to the microwave magnetic field.The results are reproducible and consistent with micromagnetic simulations,providing additional approaches and techniques for comprehending the microscopic mechanisms of magnetic domains and characterizing their rotation.

晶体硅中的铁沉淀规律

研究了在直拉单晶硅和铸造多晶硅中经 110 0℃热处理快冷或慢冷条件下所形成的铁沉淀规律及其对少数载流子扩散长度的影响 .红外扫描仪照片显示在直拉单晶硅中慢冷却形成的铁沉淀密度较低 ,而且其尺寸较大 ;在铸造多晶硅中 ,铁易在晶界上沉淀 ,沉淀规律也依赖于冷却速度 .表面光电压仪测试结果表明 :无论在直拉单晶硅材料中还是在铸造多晶硅材料中 ,快冷形成的铁沉淀对少数载流子扩散长度影响更大 .

中性原子成像探测的物理设计与仿真

研究了磁层-电离层-热层耦合星座(MIT)卫星计划中高能中性原子成像仪(NAIS-H)探测方案的原理设计和模拟仿真.以双星中性原子成像仪设计思想为基础,依据MIT卫星计划的总体科学目标和磁层卫星的轨道环境及相应自旋姿态,给出中性原子成像仪的技术架构,并针对地磁偶极场的环电流模型进行了模拟仿真.仿真结果表明,所研制的NAIS-H以其高时空分辨能力适用于监测和反演磁暴期间磁层等离子体的全球动力学过程.

不同银膜粒径对单壁碳纳米管SERS谱的影响

利用化学沉积法和溶胶法制备了粒径在20～100 nm范围内不同的表面增强纳米结构活性银膜, 系统地研究了单壁碳纳米管(SWCNT)的表面增强拉曼光谱(SERS)的G-band和D-band. 比较玻璃和石英两种不同基片上的结果发现, 单壁碳管的SERS谱随银膜粒径的变化有相同的变化趋势. G-band峰移对20～100 nm范围内活性银膜粒径的差异不敏感, 表明该波段所对应的碳管六元环本征振动比较稳定, 与界面的化学相互作用较弱. D-band的峰形随基片和活性银膜粒径不同均有改变, 且随着粒径变小, 高频振动贡献有增大的趋势, 表明无序碳与活性银膜间存在很强的相互作用.

1965～2000年北京宇宙线台垂直截止刚度的变化

根据带电粒子的力学运动方程分别计算了有外源场和无外源场情况下北京宇宙线观测台的垂直截止刚度,计算结果表明,北京宇宙线观测站的截止刚度随时间是变化的,在1965～2000年期间,1990年的垂直截止刚度最低,考虑外源场后,除1990年以外,北京宇宙线台的截止刚度都低于不考虑外源场的计算结果。

适用于放大自发辐射平滑光束的脉宽压缩方法

为了增加靶上的功率密度和耦合效率,基于饱和增益开关原理,发展了一种适用于放大自发辐射平滑光束的脉宽压缩方法。利用该方法,在赛格德大学的一台放电泵浦KrF准分子激光器上进行了实验,将该激光器输出的脉宽为14.5ns的放大自发辐射光束压缩到了7.5ns,并且保持了光束原有的均匀性。

自由钨团簇与氮分子反应性的尺寸相关性

利用激光蒸发团簇源产生Wn团簇束 ,团簇通过一个充有N2 气体分子的低压反应池 ,利用飞行时间质谱探测反应产物 ,在单次碰撞条件下研究了W+ 10 —W+ 50 和N2 分子的反应性 ,在室温条件下测量了N2 分子与W+ n 团簇反应的反应几率 .n =10— 2 6的团簇与N2 分子的反应几率与团簇尺寸有很强的相关性 ,n =16 ,2 2 ,2 3的团簇有较高的反应性 .W+ n 与N2 分子的反应性与Wn与N2 分子的反应性显示出相似的规律性 .

原生直拉单晶硅中的铜沉淀规律

采用红外扫描仪、扫描电镜以及电子束诱生电流仪研究了不同温度和不同冷却速度下原生直拉单晶硅的铜沉淀规律.红外扫描仪观察发现:只有在热处理温度高于800℃的样品中才能观察到铜沉淀团,表明在原生单晶硅中铜沉淀温度为800℃.同时,红外扫描仪和电子束诱生电流谱仪照片显示,快冷(30K/s)时,形成高密度的小铜沉淀团;而慢冷(0.3K/s)导致低密度、巨大的星形铜沉淀团的形成.实验还发现慢冷所形成的星形铜沉淀团对少数载流子具有更强的复合强度.最后,讨论了原生直拉单晶硅中铜沉淀规律的机理.

钨离子团簇与N_2分子的反应性

利用激光蒸发团簇源产生Wn 团簇束 ,团簇束通过一个充有N2 气体分子的低压反应池 ,利用飞行时间质谱探测反应产物 ,在类单次碰撞条件下研究了W+10 -W+50 和N2 分子的反应性 ,在室温条件下测量了N2 分子与W+n 团簇反应的反应几率。团簇尺寸在 10～ 2 6原子的团簇与N2 分子的反应几率与团簇尺寸有很强的相关性 ,对n =16,2 2 ,2 3的团簇具有比较高的反应性。W+n 与N2 分子的反应性与Wn 与N2 分子的反应性显示出相似的规律性。

卫星姿态对磁层中性原子成像探测的影响

适于磁层中性原子威像探测的一般是运行在磁层高度的极轨自旋稳定卫星。利用设置在不同仰角方向的探测器通过卫星自旋进行方位角扫描以实现二维中性原子成像探测。这样以来,卫星自旋轴的取向就是我们选择中性原子二维图像的仰角和方位角分布的依据。为了提高角分辨,我们总是希望把垂直于自旋轴方向的探测器时准主要成像位置。考虑卫星在极区的最佳遥测位置,我们选择卫星自旋轴垂直于轨道面将最有利于中性原子的成像探测。对于三轴稳定卫星,我们可以利用多组硅条探测器设计二维中性原子成像仪。

低能质子束在氢等离子体中的能损研究

实验测量了100 keV的质子束穿过部分电离氢等离子体靶后的能量损失.等离子体靶由气体放电方式产生,其自由电子密度在1016cm-3量级,电子温度约1—2 eV,维持时间在微秒量级.研究结果表明:质子束在等离子体靶中的能量损失与自由电子密度密切相关且明显大于在同密度条件下中性气体靶中的能量损失;在自由电子密度达到峰值处,通过实验结果计算得到此时的自由电子库仑对数约为10.8,与理论计算结果符合较好,该值比Bethe公式给出的中性气体靶中束缚电子库仑对数高4.3倍,相应的能损增强因子为2.9.

Thermophysical properties of the Ni-based alloy Nimonic 80A up to 2400 K

Nimonic 80A is a nickel-chromium alloy which is strengthened by additions of titanium and aluminium. The alloy is used for high temperature, high strength applications. Wire shaped Nimonic 80A samples are resistively volume heated as part of a fast capacitor discharge circuit. Time resolved measurements with sub-μs resolution of current through the specimen are performed with a Pearson probe, voltage drop across the specimen is measured with knife-edge contacts and ohmic voltage dividers and the radiance temperature of the sample with a pyrometer. These measurements allow to determine heat of fusion as well as heat capacity and electrical resistivity at initial geometry of Nimonic 80A as a function of temperature in the solid and in the liquid phase up to 2400 K.