Nonlinear optimization of the modern synchrotron radiation storage ring based on frequency map analysis

In this paper, we present a rule to improve the nonlinear solution with frequency map analysis (FMA), and without frequently revisiting the optimization algorithm. Two aspects of FMA are emphasized. The first one is the tune shift with amplitude, which can be used to improve the solution of harmonic sextupoles, and thus obtain a large dynamic aperture. The second one is the tune diffusion rate, which can be used to select a quiet tune. Application of these ideas is carried out in the storage ring of the Shanghai Synchrotron Radiation Facility (SSRF), and the detailed processes, as well as better solutions, are presented in this paper. Discussions about the nonlinear behaviors of off-momentum particles are also presented.     

Tune optimization of the third generation light source storage ring based on Frequency Map Analysis

Tune optimization is necessary to optimize the nonlinearity of the third generation light source storage ring. In this paper we summarize the common strategies for choosing a tune and discuss tune op- timization. Frequency Map Analysis （FMA） is applied as a tune scanning tool to reveal information about nonlinear resonances and guide the tune optimization. The Shanghai Synchrotron Radiation Facility （SSRF） storage ring is taken as a test lattice, and the optimum solutions are presented in this paper. Moreover, the third order regular structural resonances excited by sextupoles are particularly investigated, and it is found that these resonances distort the tune shifts with amplitude and show a stop-band like the linear structural resonances.     

Tune optimization of the third generation light source storage ring based on Frequency Map Analysis

Tune optimization is necessary to optimize the nonlinearity of the third generation light source storage ring. In this paper we summarize the common strategies for choosing a tune and discuss tune op-timization. Frequency Map Analysis (FMA) is applied as a tune scanning tool to reveal information about nonlinear resonances and guide the tune optimization. The Shanghai Synchrotron Radiation Facility (SSRF) storage ring is taken as a test lattice, and the optimum solutions are presented in this paper. Moreover, the third order regular structural resonances excited by sextupoles are particularly investigated, and it is found that these resonances distort the tune shifts with amplitude and show a stop-band like the linear structural resonances.     

One flavor mass reweighting in lattice QCD

One flavor mass reweighting can be used in lattice QCD computations to fine tune the quark masses to their physical values. We present a new method that utilizes an unbiased stochastic estimation of the one flavor determinant. The stochastic estimation is based on the integral representation of the determinant of a complex matrix, which we prove. In contrast to other methods it can also be applied in situations where the determinant has a complex phase. The stochastic error is controlled by determinant factorizations based on mass interpolation and Schur decomposition. As an example of an application we demonstrate how the method can be used to tune the up–down quark mass difference.     

上海光源工作点在线监测系统

上海光源储存环运行在恒流注入(top-up)模式下每10min注入一次,注入引起的β振荡为测量工作点提供了有利条件。通过数字束流位置处理器采集储存环注入时的逐圈数据,对数据进行快速傅里叶变换计算获得工作点,以此搭建了刷新间隔为10min的工作点在线监测系统。2014年上半年的运行结果表明,该系统能够有效检测工作点变化并评估加速器工作点可达到的最优性能。利用该系统能够及时发现加速器运行异常,并结合各设备运行状态可有效定位异常原因。     

上海光源工作点在线监测系统

上海光源储存环运行在恒流注入(top-up)模式下每10 min注入一次,注入引起的振荡为测量工作点提供了有利条件。通过数字束流位置处理器采集储存环注入时的逐圈数据,对数据进行快速傅里叶变换计算获得工作点,以此搭建了刷新间隔为10 min的工作点在线监测系统。2014年上半年的运行结果表明,该系统能够有效检测工作点变化并评估加速器工作点可达到的最优性能。利用该系统能够及时发现加速器运行异常,并结合各设备运行状态可有效定位异常原因。     

通过响应矩阵计算横向振荡的振幅函数和相位

 响应矩阵反映了束流位置监测器（BPM）位置处观察到的束流在校正铁磁场空间中的运行规律。根据电子储存环理论模型,采用迭代方法从实测响应矩阵计算束流横向振荡的振幅函数和相位。计算结果的精度主要受响应矩阵测量误差、BPM测量误差和校正铁电源刻度误差影响。计算响应矩阵的误差代表了迭代所采用的工作点的正确度,实际的工作点对应于计算响应矩阵的最小均方差,以此可推导实际的工作点。     

通过响应矩阵计算横向振荡的振幅函数和相位

响应矩阵反映了束流位置监测器（BPM）位置处观察到的束流在校正铁磁场空间中的运行规律。根据电子储存环理论模型,采用迭代方法从实测响应矩阵计算束流横向振荡的振幅函数和相位。计算结果的精度主要受响应矩阵测量误差、BPM测量误差和校正铁电源刻度误差影响。计算响应矩阵的误差代表了迭代所采用的工作点的正确度,实际的工作点对应于计算响应矩阵的最小均方差,以此可推导实际的工作点。     

Side-effects of the space charge field introduced by a hollow electron beam in the electron cooler of CSRm

An electron cooler is used to improve the quality of the ion beam in a synchrotron;however it also introduces a nonlinear electromagnetic field to the accelerator,which causes tune shift,tune spread and may drive resonances leading to ion beam loss.In this paper the tune shift and the tune spread caused by the nonlinear electromagnetic field of a hollow electron beam is investigated,and the resonance driving terms of the nonlinear electromagnetic field are analysed.The differences are presented compared with a solid electron beam.Calculations are performed for ~(238)U~(32+) ion of energy 1.272 MeV stored in the main Cooler Storage Ring(CSRm) at the Institute of Modern Physics,Lanzhou.It is found that in this situation the nonlinear field caused by the hollow electron beam does not lead to serious resonances.     

利用快速扫描伏安法测定醋酸根和甲酸根在铂(111)电极上吸附等温线 (cited: 3)

快速扫描伏安法是一种可以用来区分氧化/还原,吸附/脱附反应的有效工具. 这里,我们将提供一种新的方法,在一种相对浓度较低的反应物溶液中,利用不同的电位扫描速率(相对于扩散速率),可以得到电极表面的吸附/脱附过程的等温线. 本文将以醋酸根在酸性溶液中在Pt(111)上吸附作为例子,并将此方法扩展到复杂的甲酸氧化反应机理研究中.     

A molecular dynamics simulation study on resonance frequencies comparison of tunable carbon-nanotube resonators

We investigated tunable gigahertz-resonators, which is based on the application of a telescoped double-walled carbon-nanotube that can be used repeatedly and operate at a single frequency or have a relatively narrow frequency range, via classical molecular dynamics simulations of a double-walled carbon-nanotube. Two types of telescoped double-walled carbon-nanotube resonators were compared with each other; one was bridge-type and another was cantilever-type, and one side was connected to a position controller in order to achieve a telescoped carbon-nanotube. The frequency bandwidth of our cantilevered type design can exceed that of the bridged type. Our simulations showed that such a system can tune it up its resonance frequency by controlling the length of oscillating carbon-nanotube resonator.     

Modelling of tuning of an ultra low frequency Roberts Linkage vibration isolator

We present an analytical model for a Roberts Linkage used as an ultra low frequency vibration isolator. The Roberts Linkage is a structure that simulates a very long radius conical pendulum, at a relatively small height. We show through an analytical solution that it is possible to independently tune the centre of percussion and the resonant frequency for arbitrary geometrical configurations. The result is shown to provide a practical tuning solution, which achieves near ideal vibration isolation.     

Performance improvement of unidimensional continuous-variable quantum key distribution using heralded hybrid linear amplifier

We propose an improved scheme for unidimensional continuous-variable quantum key distribution (UCVQKD) using heralded hybrid linear amplifier, aiming to simplify the implementation and improve secret key rate. Different from the symmetrical continuous-variable quantum key distribution protocol (CVQKD), this scheme modulates one quadrature of the coherent state with security insurance. The heralded hybrid linear amplifier concatenates a deterministic linear amplifier (DLA) and a noiseless linear amplifier (NLA), which can tune between the high-gain or high noise-reduction for performance enhancement. Security analysis shows that the proposed scheme can be secured under the collective attacks. Compared with traditional UCVQKD involving noiseless amplifier, the security transmission distance of proposed protocol is increased by 24 kilometers. It not only simplifies the modulation process but also has approximate performance with symmetrical CVQKD in terms of maximal security transmission distance.     

Modifying protein adsorption by layers of glutathione pre-adsorbed on Au(111)

Molecular interaction with metal surfaces raises fundamental questions regarding their binding tendency, their dispersion on the surface, as well as their conformation which may change their biological properties; addressing these questions, and being able to tune protein interactions, is of primary importance for the control of biointerfaces. In this study, one tripeptide, GSH (glu-cys-gly), was used to condition gold surfaces and thus influence the adsorption of bovine serum albumin (BSA). Depending on the pH value of the GSH solution, cationic, zwitterionic or anionic forms of the tripeptide could be stabilised on the surface, before interacting with BSA solutions. The amount of proteins was observed to depend both on the chemical state of the adsorbed underlying peptide and on the solvent of the protein solution, indicating an important role of electrostatic interactions upon protein adsorption. Moreover, atomic force microscopy (AFM), and synchrotron IR microscopy revealed a heterogeneous distribution of proteins on the GSH layer.     

基于Talbot效应的可调位相差二维六角位相阵列器的理论研究和数值模拟

系统研究了基于Talbot效应的光栅阵列器,利用数值模拟方法开展了阵列器的理论研究,对二维振幅型与固定位相差型阵列器进行了分析,通过外加电场调制位相差可以很好的解决二维振幅型与固定位相差型阵列器后z处光强分布不可调节和工作易受温度影响的问题.推导了外加电场调制位相差位相型阵列器实现均匀光强分布的理论模型,并验证了Paturz等人的实验结果,为此种新型阵列器的研究提供了基础.     

A novel design of semi-active hydraulic mount with wide-band tunable notch frequency

Hydraulic engine mount is advanced vibration isolator with superior performance to reduce vibration transferred from engine to chassis. As the stiffness at notch frequency is small, some semi-active or active hydraulic mounts tune some parameters to let notch frequency coincide with exciting frequency for better vibration isolation performance. It is discovered the current semi-active mounts can tune the notch frequency in narrow frequency band when only one parameter is tuned. A novel semi-active hydraulic engine mount design which introduces screw thread is proposed and researched in the paper. This hydraulic mount can control both cross section area and the length of inertia track and the theoretical tunable notch frequency band is [0, ∞). Theoretical work is carried out to uncover the capability for the proposed design to tune notch frequency. Simulation work is performed to understand its high vibration isolation performance. For the purpose of energy conservation, the friction self-locking is introduced. This denotes once the mount is tuned at optimal condition, the energy can be cut off and the optimal condition will never change. We also determine the best time to tune the parameters of the proposed mount in order to decrease the acting force. The proposed semi-active mount has capability to obtain wide band tunable notch frequency and has merit of energy conservation.     

Ultrasound-boosted selectivity of CO in CO2 electrochemical reduction

Among the possible products of CO₂ electrochemical reduction, CO plays a unique and vital role, which can be an ideal feedstock for further reduction to C₂₊ products, and also the important component of syngas that can be used as feedstock for value-added chemicals and fuels. However, it is still a challenge to tune the CO selectivity on Cu electrode. Here we newly construct an ultrasound-assisted electrochemical method for CO₂ reduction, which can tune the selectivity of CO₂ to CO from less than 10% to >80% at −1.18 V versus (vs.) reversible hydrogen electrode (RHE). The partial current density of CO production is significantly improved by 15 times. By in-situ Raman study, the dominating factor for the improved CO production is attributed to the accelerated desorption of *CO intermediate. This work provides a facile method to tune the product selectivity in CO₂ electrochemical reduction.     

Reversible Circular Dichroism Induced by Energy Losses without Changing Chirality of Structure

Tunable circular dichroism (CD) is widely used in biology signal detection and chemical analysis. Researchers usually tune CD by changing the chirality and symmetry of nanostructures either directly or indirectly. Changes to a planar nanostructure's chirality are resisted by its structural reciprocity, which also constrains its CD tuning. However, the distribution of finite non-radiative (ohmic) losses on a planar nanostructure will not be constrained by the reciprocity of structure. Here, a nanostructure is designed to tune the intensity of energy losses rather than change the chirality and symmetry of the whole structure. The results show that not only are the position and intensity of CD affected, but also the sign of the CD signal changes. These methods and results can help in utilizing the new approach to tune the modes and sign of a CD signal.     

Multiphoton-excited microfabrication in live cells via Rose Bengal cross-linking of cytoplasmic proteins

We demonstrate the use of multiphoton-excited photochemistry to cross-link three-dimensional matrices directly from cytoplasmic proteins in a live cell (starfish oocyte). Fluorescence recovery after photobleaching measurements were used to determine diffusion coefficients inside intracellular cross-linked structures, and it was found that the diffusion was approximately 3 to 4 orders of magnitude slower than in free solution and 2-3 orders of magnitude slower than in cytoplasm and that the value can be tuned by controlling the laser exposure. Complex structures can be fabricated to construct channels and compartments that could be used to isolate cellular processes, and the method should thus be applicable to a broad range of problems in cell biology.     

Actively coupled index-guided lasers

An opto-electronic device is described in which two index-guided semiconductor lasers are actively coupled by means of a control injection current. The behaviour of the device under differing conditions of optical injection is examined. It is shown to be possible to find light-sensitive and light-insensitive configurations for device operation. The control current can be used to tune the sensitivity of the device.