High-precision high-voltage detuning system for HIAF-SRing electron target

The development of a detuning system for the precision control of electron energy is a major challenge when electron targets are used in ion-storage rings.Thus,a high-precision,high-voltage,detuning system was developed for the electron target of a high-intensity heavy-ion accelerator facility-spectrometer ring(HIAF-SRing)to produce accurate electron-ion relative energies during experiments.The system consists of auxiliary,and high-voltage detuning power supplies.The front stage of the auxiliary power supply adopts an LCC resonant converter operating in the soft-switching state and an LC filter for a sinusoidal waveform output in the post-stage.The detuning power supply is a high-voltage pulse amplifier(HVPA)connected with a high-voltage DC(HVDC)module in series.In this paper,the design and development of the detuning system are described in detail,and the test bench is presented.The test results demonstrated that the detuning system conforms to the technical specifications of the dielectronic recombination(DR)experiment.Finally,a Fe15+DR spectrum was measured using the detuning system.The experimental data demonstrated a good experimental resolution and verified the reliability and feasibility of the design.

Simulation research on surface growth process of positive and negative frequency detuning chromium atom lithographic gratings

Chromium atom photolithography gratings are a promising technology for the development of nanoscale length standard substances due to their high accuracy,uniformity,and consistency.However,the inherent difference between the interaction of positive and negative frequency detuning standing wave field and the atoms can cause a difference in the adjacent peak-to-valley heights of the grating in positive and negative frequency detuning chromium atom lithography,which greatly reduces its accuracy.In this study,we performed a controlled variable growth simulation using the semi-classical theoretical model and Monte Carlo method with trajectory tracking and ballistic deposition methods to investigate the influence of key experimental parameters on the surface growth process of positive and negative frequency detuning atomic lithography gratings.We established a theoretical model based on simulation results and summarized empirical equations to guide the selection of experimental parameters.Our simulations achieved uniform positive and negative frequency detuning atomic lithography gratings with a period of 1/4 of the wavelength corresponding to the atomic transition frequency,and adjacent peak-to-valley heights differing by no more than 2 nm,providing an important theoretical reference for the controllable fabrication of these gratings.

Two-photon live imaging of direct glia-to-neuron conversion in the mouse cortex

Over the past decade,a growing number of studies have reported transcription factor-based in situ reprogramming that can directly conve rt endogenous glial cells into functional neurons as an alternative approach for n euro regeneration in the adult mammalian central ne rvous system.Howeve r,many questions remain regarding how a terminally differentiated glial cell can transform into a delicate neuron that forms part of the intricate brain circuitry.In addition,concerns have recently been raised around the absence of astrocyte-to-neuron conversion in astrocytic lineage-tra cing mice.In this study,we employed repetitive two-photon imaging to continuously capture the in situ astrocyte-to-neuron conversion process following ecto pic expression of the neural transcription factor NeuroD1 in both prolife rating reactive astrocytes and lineage-tra ced astrocytes in the mouse cortex.Time-lapse imaging over several wee ks revealed the ste p-by-step transition from a typical astrocyte with numero us short,tapered branches to a typical neuro n with a few long neurites and dynamic growth cones that actively explored the local environment.In addition,these lineage-converting cells were able to migrate ra dially or to ngentially to relocate to suitable positions.Furthermore,two-photon Ca2+imaging and patch-clamp recordings confirmed that the newly generated neuro ns exhibited synchronous calcium signals,repetitive action potentials,and spontaneous synaptic responses,suggesting that they had made functional synaptic connections within local neural circuits.In conclusion,we directly visualized the step-by-step lineage conversion process from astrocytes to functional neurons in vivo and unambiguously demonstrated that adult mammalian brains are highly plastic with respect to their potential for neuro regeneration and neural circuit reconstruction.

Temperature-feedback two-photon-responsive metal-organic frameworks for efficient photothermal therapy

The realization of real-time thermal feedback for monitoring photothermal therapy(PTT)under near-infrared(NIR)light irradiation is of great interest and challenge for antitumor therapy.Herein,by assembling highly efficient photothermal conversion gold nanorods and a temperature-responsive probe((E)-4-(4-(diethylamino)styryl)-1-methylpyridin-1-ium,PyS)within MOF-199,an intelligent nanoplatform(AMPP)was fabricated for simultaneous chemodynamic therapy and NIR light-induced temperature-feedback PTT.The fluorescence intensity and temperature of the PyS probe are linearly related due to the restriction of the rotation of the characteristic monomethine bridge.Moreover,the copper ions resulting from the degradation of MOF-199 in an acidic microenvironment can convert H_(2)O_(2)into•OH,resulting in tumor ablation through a Fenton-like reaction,and this process can be accelerated by increasing the temperature.This study establishes a feasible platform for fabricating highly sensitive temperature sensors for efficient temperature-feedback PTT.

The influences of dipole-dipole interaction and detuning on the sudden death of entanglement between two atoms in the Tavis-Cummings model

The influences of dipole-dipole interaction and detuning on the entanglement between two atoms with different initial tripartite entangled W-like states in the Tavis Cummings model have been investigated by means of Wootters＇ concurrence, respectively. The results show that the entanglement between the two atoms can be enhanced via appropriately tuning the strength of dipole-dipole interaction of two atoms or the detunings between atom and cavity, and the so-called sudden death effect can he weakened simultaneously.

A non-invasive diagnostic method of cavity detuning based on a convolutional neural network

As modern accelerator technologies advance toward more compact sizes,conventional invasive diagnostic methods of cavity detuning introduce negligible interference in measurements and run the risk of harming structural surfaces.To overcome these difficulties,this study developed a non-invasive diagnostic method using knowledge of scattering parameters with a convolutional neural network and the interior point method.Meticulous construction and training of the neural network led to remarkable results on three typical acceleration structures:a 13-cell S-band standing-wave linac,a 12-cell X-band traveling-wave linac,and a 3-cell X-band RF gun.The trained networks significantly reduced the burden of the tuning process,freed researchers from tedious tuning tasks,and provided a new perspective for the tuning of side-coupling,semi-enclosed,and total-enclosed structures.

Synchronously Pumped Mode-Locked 1.89 μm Tm-Doped Fiber Laser with High Detuning Toleration

We propose and demonstrate a synchronously pumped mode-locked Tm-doped fiber（TDF） laser without any extra mode-locking elements. Pumped by a 1.56 μm pulse fiber laser, the TDF laser generates 1.17 ps pulses with a spectral width of 9.7 nm and a repetition rate of 9.33 MHz. The emission wavelength is tunable along with the cavity length detuning in a wide range of 3 mm. The high detuning toleration is beneficial to achieve high temperature and vibration stability in all-fiber configuration lasers.

The squeezing dynamics of two independent atoms by detuning in two non-Markovian environments

The squeezing dynamics of two independent two-level atoms off-resonantly coupled to two non-Markovian reservoirs is studied by the time-convolutionless master-equation approach. We find that the squeezing of two atoms is dependent on both detuning and the non-Markovian effect. Our results show that, in the non-Markovian regime, the bigger the detuning and the stronger the non-Markovian effect are, the larger the strength of the squeezing is. And the squeezing of two atoms can be effectively protected for a long time when both the non-Markovian effect and detuning are present simultaneously. The physical mechanism is that the detuning not only can promote the feedback of information from the environment into the atomic system but also can greatly suppress the atomic decay in the non-Markovian regime.

Two-photon absorption of FAPbBr_(3) perovskite nanocrystals

Perovskite nanocrystals(NCs) with high two-photon absorption(TPA) cross-section are of great interest due to their potential applications in three-dimensional optical data storage and multiphoton fluorescence microscopy. Among various perovskite materials, FAPbBr_(3) NCs show a better development prospect due to their excellent stability. However, there are few reports on their nonlinear optical properties. In this work, the nonlinear optical behavior of FAPbBr_(3) NCs is studied.The methods of multiphoton absorption photoluminescence saturation and open aperture Z-scan technique were applied to determine the TPA cross-section of FAPbBr_(3)NCs, which was around 2.76 × 10^(-45)cm^(4)·s·photon^(-1) at 800 nm. In addition,temperature-dependent photoluminescence induced by TPA was investigated, and the small longitudinal optical phonon energy and electron–phonon coupling strength was obtained, which confirm the weak Pb–Br interaction. Meanwhile, it is found that the exciton binding energy in FAPbBr_(3) NCs was 69.668 me V, which may be ascribed to the strong hydrogen bond interaction. It is expected that our findings will promote the application of FAPbBr_(3) NCs in optoelectronic devices.

A simple Bessel module with tunable focal depth and constant resolution for commercial two-photon microscope

The volumetric imaging of two-photon microscopy expands the focal depth and improves the throughput,which has unparalleled superiority for three-dimension samples,especially in neuroscience.However,emerging in volumetric imaging is still largely customized,which limits the integration with commercial two-photon systems.Here,we analyzed the key parameters that modulate the focal depth and lateral resolution of polarized annular imaging and proposed a volumetric imaging module that can be directly integrated into commercial two-photon systems using conventional optical elements.This design incorporates the beam diameter adjustment settings of commercial two-photon systems,allowing flexibility to adjust the depth of focus while maintaining the same lateral resolution.Further,the depth range and lateral resolution of the design were verified,and the imaging throughput was demonstrated by an increase in the number of imaging neurons in the awake mouse cerebral cortex.

A novelα-ketoamide reactivity-based two-photon fluorogenic probe for visualizing peroxynitrite in Parkinson's disease models

Peroxynitrite(ONOO^(-))contributes to oxidative stress and neurodegeneration in Parkinson's disease(PD).Developing a peroxynitrite probe would enable in situ visualization of the overwhelming ONOO^(-)flux and understanding of the ONOO^(-)stress-induced neuropathology of PD.Herein,a novelα-ketoamide-based fluorogenic probe(DFlu)was designed for ONOO^(-)
monitoring in multiple PD models.The results demonstrated that DFlu exhibits a fluorescence turn-on response to ONOO^(-)with high specificity and sensitivity.The efficacy of DFlu for intracellular ONOO^(-)
imaging was demonstrated systematically.The results showed that DFlu can successfully visualize endogenous and exogenous ONOO^(-)in cells derived from chemical and biochemical routes.More importantly,the two-photon excitation ability of DFlu has been well demonstrated by monitoring exogenous/endogenous ONOO^(-)production and scavenging in live zebraflsh PD models.This work provides a reliable and promising
α-ketoamide-based optical tool for identifying variations of ONOO^(-)in PD models.

Modulation bandwidth enhancement in monolithic integrated two-section DFB lasers based on the detuned loading effect

Modulation bandwidth enhancement in a directly modulated two-section distributed feedback(TS-DFB)laser based on a detuned loading effect is investigated and experimentally demonstrated.The results show that the 3-dB bandwidth of the TS-DFB laser is increased to 17.6 GHz and that chirp parameter can be reduced to 2.24.Compared to the absence of a detuned loading effect,there is a 4.6 GHz increase and a 2.45 reduction,respectively.After transmitting a 10 Gb/s non-return-to-zero(NRZ)signal through a 5-km fiber,the modulation eye diagram still achieves a large opening.Eight-channel laser arrays with precise wavelength spacing are fabricated.Each TS-DFB laser in the array has side mode suppression ratios(SMSR)>49.093 dB and the maximum wavelength residual<0.316 nm.

High-speed directly modulated distributed feedback laser based on detuned loading and photon-photon resonance effect

A monolithic integrated two-section distributed feedback(TS-DFB)semiconductor laser for high-speed direct modulation is proposed and analyzed theoretically.The grating structure of the TS-DFB laser is designed by the reconstructionequivalent-chirp(REC)technique,which can reduce the manufacturing cost and difficulty,and achieve high wavelength controlling accuracy.The detuned loading effect and the photon-photon resonance(PPR)effect are utilized to enhance the modulation bandwidth of the TS-DFB laser,exceeding 37 GHz,while that of the conventional one-section DFB laser is only 16 GHz.When the bit rate of the non-return-to-zero(NRZ)signal reaches 55 Gb/s,a clear eye diagram with large opening can still be obtained.These results show that the proposed method can enhance the modulation bandwidth of DFB laser significantly.

Production of χc and ηc in Ultra-Peripheral Collisions with Two-Photon Processes

We calculate the production of χc and ηc by the two-photon process in ultra-peripheral heavy ion collisions at Relativistic Heavy Ion Collider (RHIC) and Large Hadron Collider (LHC) energies. The differential cross section of transverse momentum distribution and rapidity distribution for (H = χc and ηc), are estimated by using the equivalent photon flux in the impact parameter space. The numerical results indicate that the study of χc and ηc in ultra-peripheral heavy ion collisions are feasible at RHIC and LHC energies.

提高微腔孤子光频梳泵浦能量转换效率技术研究进展

分析了孤子微梳泵浦能量转换效率低的原因,介绍了目前已提出的几种提高孤子微梳泵浦光能量转换效率的技术方案,包括激发孤子晶体光梳利用多孤子结构、正常-反常色散双腔耦合泵浦光循环存储结构、微腔-光纤/波导环泵浦光反馈耦合干涉结构、主-副微环腔耦合超模谐振峰劈裂结构等,并分析了这些方案的优缺点。在此基础上,给出了本课题组对反馈耦合腔的优化设计,仿真模拟结果显示,单孤子微梳的泵浦光转换效率可超过25%。最后,对孤子微梳的低能耗产生方案作出总结和展望,为微腔孤子光频梳泵浦能量转换效率提高技术的发展与应用提供理论参考。

Multi-branched carbazole derivatives for two-photon absorption and two-photon excited fluorescence

Carbazole-core multi-branched chromophores 9-ethyl- 3, 6-bis （ 2- { 4- [ 5- （4-tert-butyl-phenyl） - [ 1, 3, 4 ] oxadiazol-2-yl ] - phenyl }-vinyl） -carbazole（3） and 9-ethyl-3-（ 2- {4-[ 5-（4-tert-butyl- phenyl） -[ 1, 3, 4 ] oxadiazol-2-yl ] -phenyl }-vinyl ） -carbazole （ 2 ） are synthesized through Wittig reaction and characterized by nuclear magnetic resonance（NMR）and infrared（IR）. The two- photon absorption properties of chromophores are investigated. These chromophores exhibit large two-photon absorption crosssections and strong blue two-photon excited fluorescence. The cooperative enhancement of two-photon absorption（TPA） in the multi-branched structures is observed. This enhancement is partly attributed to the electronic coupling between the branches. The electronic push-pull structures in the arm and their cooperative effects help the extended charge transfer for TPA.

相干布居囚禁振荡与拉曼失谐的关系

相干布居囚禁(CPT)振荡是一种基于CPT态而产生的瞬态振荡现象,与相干双色光频差和Λ型三能级结构原子基态能级间隔之间的拉曼失谐有关.本文采用锯齿波对微波信号进行频率调制,实现拉曼失谐均匀变化和阶跃变化.并通过建立频率调制速率和拉曼失谐变化速率之间的关系,分析拉曼失谐变化速率和变化方式对CPT振荡的影响.结果表明,当拉曼失谐均匀变化时,激发CPT态原子产生振荡现象需要满足变化速率较快的条件,且激发产生的振荡呈现非谐波振荡行为.当拉曼失谐发生阶跃变化时,激发产生的CPT振荡为阻尼振荡且振荡频率与失谐量相等.利用锯齿波进行微波频率调制,进而实现对拉曼失谐的调制,实现CPT态的完全建立和CPT振荡的完全衰减过程,在弱磁场测量和原子钟领域具有较大的应用潜力.

基于副边解耦极板的电容式无线电能传输系统拾取端失谐评估

对于电容式无线电能传输(CWPT)系统,准确评估拾取端回路的失谐程度是维持系统谐振稳定的前提。然而,由于系统拾取端的感应电压无法被直接观测,难以通过测量感应电压和回路电流间的相位差来评估拾取端回路的失谐程度。文中提出一种能够间接测量拾取端感应电压相位信息,评估拾取端回路失谐程度的CWPT系统。基于Z参数建立三端口CWPT系统的数学模型和等效电路,并依托该模型提出一种基于副边解耦极板的耦合机构。分析在感应电压测量和失谐程度评估过程中存在的误差,提出拾取端回路失谐程度的评估校正方法。搭建了带有副边解耦极板的CWPT系统原理样机,实验结果表明,拾取端谐振时的失谐程度评估误差不超过1Ω,拾取端感性/容性失谐时的失谐程度评估误差分别小于2%和5%。

脉动顶张力作用下输流立管涡激振动主共振研究

为定量描述海洋工程中输流立管受脉动顶张力作用时的涡激振动响应,本文研究了海洋输流立管受到内部流体、脉动顶张力和涡流激励作用时的参数主共振问题。首先建立了该问题的数学模型,运用Galerkin法和多重尺度法对其进行求解,引入调谐参数描述输流立管第一阶固有频率同顶张力脉动频率和涡流频率的接近程度,通过改变调谐参数,研究输流立管的动力学响应。结果表明:定常顶张力作用下,立管的振幅为单值,随着调谐参数增大,立管振幅先增大后减小,且出现明显的跳跃现象,内部流体速度和张力幅值的竞争机制也会影响立管振幅;脉动顶张力作用时,在一阶锁频的条件下,随着调谐参数变化,立管的振幅呈现“多值—单值—多值”的变化规律,顶张力均值或脉动幅值越大,立管振幅的变化范围越宽。

Preparation of entangledW states based on the cavity QED system

We present a qubit-loss-free(QLF)fusion scheme for generating large-scale atom W states in cavity quantum electrodynamics(QED)system.Compared to the most current fusion schemes which are conditioned on the case where one particle can be extracted from each initial W state to the fusion process,our scheme will access one or two particles from each W state.Based on the atom–cavity-field detuned interaction,three jWin+m+t states can be generated from the jWin,jWim,and jWit states with the help of two auxiliary atoms,and three jWin+m+t+q states can be generated from jWin,jWim,jWit,and a jWiq state with the help of three auxiliary atoms.Comparing the numerical simulations of the resource cost of fusing three small-size W states based on the previous schemes,our fusion scheme seems to be more efficient.This QLF fusion scheme can be generalized to the case of fusing k different or identical particle W states.Furthermore,with no qubit loss,it greatly reduces the number of fusion steps and prepares W states with larger particle numbers.