Mechanical design and analysis of a low beta squeezed half-wave resonator

A superconducting squeezed type half-wave resonator(HWR)ofβ=0.09 has been developed at the Institute of Modern Physics,Lanzhou.In this paper,a basic design is presented for the stiffening structure for the detuning effect caused by helium pressure and Lorentz force.The mechanical modal analysis has been investigated the with finite element method(FEM).Based on these considerations,a new stiffening structure is proposed for the HWR cavity.The computation results concerning the frequency shift show that the low beta HWR cavity with new stiffening structure has low frequency sensitivity coefficient df/dp and Lorentz force detuning coefficient KL,and stable mechanical properties.     

Study on the frequency tuning of the half-wave resonator at IMP

The RF and mechanical coupled analyses are essential in superconducting cavity design in order to predict the deformation of the cavity walls and the frequency shift caused by the deformation. In this paper, the detuning caused by both bath helium pressure and Lorentz force is analysed and a tuning system has been investigated and designed to compensate the detuning by deforming the half-wave resonator along the beam axis. The simulations performed with ANSYS code show that the tuning system can adjust and compensate the frequency drift due to external vibrations and helium pressure fluctuation during operation.     

Design of a superconducting low beta niobium resonator

The proposed high current injector for the superconducting Linac at the Inter-University Accelerator Centre will have several accelerating structures, including a superconducting module which will contain low beta niobium resonators. A prototype resonator for the low beta module has been designed. The resonator has been carefully modelled to optimize the electromagnetic parameters. In order to validate them, a room-temperature copper model has been built and tested. In this paper we present details of the electromagnetic design of the low beta resonator, briefly discuss the mechanical and engineering design, and present results from the measurements on the room-temperature copper model.     

Study and design of RF coupler for Chinese ADS HWR superconducting cavity

An RF power coupler is a key component of the superconducting accelerating system in Chinese ADS proton linac injector I, which is used to transmit 15 kW RF power from the power source to the superconducting HWR cavity. According to the requirement of working frequency, power level, transmission capability and cooling condition, the physics design of coupler has been finished, which includes RF structure optimization, thermal simulation, thermal stress analysis and so on. Based on this design, the prototype of HWR coupler has been fabricated, and it has successfully passed the high power test.     

325 MHz低β半波长谐振腔设计

对质子加速器中半波长谐振腔（HWR）型的设计进行了研究,完成一种新型HWR超导腔的初步设计。通过对超导腔设计方法及设计原则的研究,结合相关半波长谐振腔的研究现状,充分利用电磁设计软件的功能,对325 MHz低大孔径的半波长谐振腔进行了设计研究。在建模中,针对腔体的不同部位进行比较分析,优化模型形状;在计算中,采用新型有限元网格,使计算快速而结果稳定;在后处理中,使用参数扫描,实现了腔形参数优化;在腔形分析中,计算了二次电子倍增效应,验证了腔体形状的可行性。通过此设计过程,使所设计的新型为0.12的HWR腔具有较好的电磁参数,满足质子加速器的要求,并可应用到实际工程中。     

低分析频率压缩光的实验制备

基于PPKTP晶体的阈值以下光学参量振荡(OPO)过程,制备了共振于铷原子D1线795 nm的压缩真空态光场,研究了分析频率处于千赫兹范围的主要噪声来源,特别是795 nm激光及其二次谐波397.5 nm激光在晶体内吸收引起的非线性损耗增加和系统热不稳定的问题(397.5 nm激光处于PPKTP晶体透光范围边缘,具有高于其他波长数倍的吸收系数).以795 nm和1064 nm为例,分析了非线性损耗及晶体内热效应对压缩度的影响.受限于以上因素,795 nm压缩光很难得到1064 nm波段同样的压缩度.探测系统中的噪声耦合则限制了压缩频带.实验上对分析频率为千赫兹的经典噪声进行了有效控制,通过使用真空注入的OPO、垂直偏振及反向传输的腔长锁定光、低噪声的平衡零拍探测器、高稳定度的实验系统及量子噪声锁定等方法,最终在2.6—100 kHz的分析频段得到了约2.8 dB的795 nm压缩真空.该压缩光可用作磁场测量系统的探测光以提高测量灵敏度.     

Study and design of RF coupler for Chinese ADS HWR superconducting cavity

An RF power coupler is a key component of the superconducting accelerating system in Chinese ADS proton linac injector I, which is used to transmit 15 kW RF power from the power source to the superconducting HWR cavity. According to the requirement of working frequency, power level, transmission capability and cooling condition, the physics design of coupler has been finished, which includes RF structure optimization, thermal simulation, thermal stress analysis and so on. Based on this design, the prototype of HWR coupler has been fabricated, and it has successfully passed the high power test.     

Engineering two-mode squeezed states of cold atomic clouds with a superconducting stripline resonator

A scheme is proposed for engineering two-mode squeezed states of two separated cold atomic clouds positioned near the surface of a superconducting stripline resonator. Based on the coherent magnetic coupling between the atomic spins and a stripline resonator mode, the desired two-mode squeezed state can be produced via precisely control on the dynamics of the system. This scheme may be used to realize scalable on-chip quantum networks with cold atoms coupling to stripline resonators.     

Electromagnetic design and optimization of a superconducting quarter wave resonator

Superconducting (SC) cavities currently used for the acceleration of protons at a low velocity range are based on half wave resonators. Due to the rising demand on high current, the issue of beam loading and space charge problems has arisen. Qualities of low cost and high accelerating efficiency are required for SC cavities, which are properly fitted by using an SC quarter wave resonator (QWR). We propose a concept of using QWRs with frequency 162.5 MHz to accelerate high current proton beams. The electromagnetic design and optimization of the prototype have been finished at Peking University. An analytical model derived by the transmission line theory is used to predict an optimal combination of the geometrical parameters, with which the calculation by Microwave Studio shows a good agreement. The thermal analysis to identify the temperature rise of the demountable bottom plate under various levels of thermal contact also has been done, and the maximum increment is less than 0.5 K even though the contact state is poor.     

石墨烯/羟基磷灰石复合材料力学性能的数值研究

为了研究石墨烯/羟基磷灰石复合材料力学性能（弹性模量和泊松比）,开发了石墨烯/羟基磷灰石复合材料的随机分布模型自动生成算法及相应的计算程序;建立石墨烯/羟基磷灰石复合材料的有限元模型,计算添加不同质量分数的石墨烯对复合材料力学性能的影响,通过与实验数据对比验证算法的有效性.结果表明：添加0.25%~1.25%（质量分数）的石墨烯可使复合材料的弹性模量增加12%~50%,表明添加少量石墨烯即能有效地改善羟基磷灰石的力学性能.     

Mechanical and thermodynamical stability of BiVO_4 polymorphs using first-principles study

First principles calculations of structural, electronic, mechanical, and thermodynamic properties of different polymorphs of BiVO_4 are performed using Bender-type plane/wave ultrasoft pseudopotentials within the generalized gradient approximation(GGA) in the frame of density functional theory(DFT). The calculated structural and electronic properties are consistent with the previous theoretical and experimental results. The electronic structures reveal that m-BiVO_4, opBiVO_4, and st-BiVO_4 have indirect band gaps, on the other hand, zt-BiVO_4 has a direct band gap. From the DOS and Mulliken's charge analysis, it is observed that only m-BiVO_4 has 6s~2Bi lone pair. Bond population analysis indicates that st-BiVO_4 shows a more ionic nature and a similar result is obtained from the elastic properties. From the elastic properties, it is observed that st-BiVO_4 is more mechanically stable than the others. st-BiVO_4 is more ductile and useful for high electro-optical and electro-mechanical coupling devices. Our calculated thermodynamic properties confirm the similar characteristics found from electronic and elastic properties. m-BiVO_4 is useful as photocatalysts, solid state electrolyte,and electrode and other polymorphs are applicable in electronic device fabrications.     

Mechanical and thermodynamic properties of infrared transparent low melting chalcogenide glass

The properties of infrared (IR) transparent chalcogenide glass Se₅₇I₂₀As₁₈Te₃Sb₂ have been studied for the first time by dynamic mechanical analysis (DMA). This glass demonstrates both high transparency in a broad IR band (1–12 μm) and a particularly low softening point (near 50 °C). It is known as one of the best adhesives intended for the binding of IR optics elements. The DMA method gives valuable information about the complex Young’s modulus of the glass in its softening region. In parallel with the study of mechanical properties of the glass the character of its glass transition process has been investigated. Our results of DMA were then compared with our thermodynamic data obtained by scanning calorimetry. The peak of mechanical losses in DMA appears to be situated considerably higher than the calorimetrically determined glass transition temperature.     

Mechanical and Thermal Properties of Polyurethane Elastomers Synthesized with Toluene Diisocyanate Trimer

A series of polyurethane elastomers (PUE) incorporating TDI (toluene diisocyanate) trimer were synthesized via an in-situ polymerization and prepolymer process. It was found that for the sample with 10 wt% or less TDI trimer, the stress–strain curves of PUE exhibited the characteristics of a ductile failure with relatively high tensile strength and elongation at break. However, with incorporation 20～30 wt% of TDI trimer, the samples changed to brittle fracture. All PUE samples exhibited a loss peak corresponding to the glass transition temperature (T_g ) of the soft-segments, which shifted to higher temperature and decreased in peak height by incorporation of the three-functional isocyanurate rings. Although the TDI trimer modified PUE showed only slightly higher onset and peak degradation values than that of PUE in the absence of TDI trimer, there were still big differences in the end temperatures of the second stage. The value of activation energy and frequency factor fluctuated for varying samples, indicating that the thermal stability of PUE can be improved to a certain degree by incorporation of TDI trimer, but not so remarkably.     

Mechanical and Thermal Performance of High-Density Polyethylene/Alumina Nanocomposites

High-density polyethylene (HDPE) nanocomposites reinforced with pristine and vinyltrimethoxysilane (VTMS)-treated alumina nanoparticles of 2, 4, and 6 wt% were melt-compounded in a twin-screw extruder followed by injection molding. Their structure, thermal and mechanical behaviors were studied. Fourier transform infrared (FTIR) spectra showed that VTMS was successfully covalently grafted to the alumina nanoparticles. The X-ray diffraction (XRD) patterns indicated that the alumina nanoparticle additions broadened the characteristic peak width of HDPE, indicating that they reduced the crystallite size of HDPE. The heat deflection temperature and thermogravimetric analyses demonstrated that the dimensional and thermal stability of HDPE were enhanced markedly by adding pristine and silane-treated alumina nanoparticles. The alumina nanoparticle additions were also beneficial in enhancing Young's modulus and yield strength of HDPE. The reinforcing effect was particularly apparent in the silane-treated nanocomposites due to improved filler–matrix interactions.     

连续变焦距镜头结构设计及焦距实时输出分析

机械补偿式变焦距镜头以其自身的优点受到了广泛的关注和应用。介绍机械补偿式三组元连续变焦系统的基本工作原理及组成,根据实际使用要求,设计出保证变倍过程中变倍组和补偿组按一定函数规律运动的圆柱凸轮结构、导向机构及相应的加工工艺,从变倍运动方程和设计的变焦结构形式出发,分析变焦过程中焦距实时输出的实现方法和存在的问题,并提出相应的解决措施,对焦距值实时输出精度的提高以及变焦距镜头的设计和装调具有借鉴作用。     

Parametric resonance and Hopf bifurcation analysis for a MEMS resonator

We study the response of a MEMS resonator, driven in an in-plane length-extensional mode of excitation. It is observed that the amplitude of the resulting vibration has an upper bound, i.e., the response shows saturation. We present a model for this phenomenon, incorporating interaction with a bending mode. We show that this model accurately describes the observed phenomena. The in-plane (“trivial”) mode is shown to be stable up to a critical value of the amplitude of the excitation. At this value, a new “bending” branch of solutions bifurcates. For appropriate values of the parameters, a subsequent Hopf bifurcation causes a beating phenomenon, in accordance with experimental observations.     

Structure and Mechanical Stability of Epoxy Modified Polyurethane Foam Under Heat and Stress

A series of phenolic epoxy resin (PEP) modified polyurethane foams (PUF) were prepared via an in-situ polymerization, one step process. It was found that the epoxy modified PUF foam exhibited a perforated network structure with larger cell size, higher open cell porosity and enhanced ovality compared with pure PUF. With increasing content of PEP, the tensile strength, elongation at break and low temperature modulus of PUF decreased. A single T_g was observed for PEP modified PUF, indicating that the two component phases of the polyurethane-epoxy were miscible. With increasing PEP content, the T_g of PUF shifted slightly to higher temperature, tan δ_max dropped to lower values, and the retention value of the storage modulus at ?20 and ?10?°C increased. For pure PUF, the cell walls degraded and the structure became disordered after aging under heat and stress, while for PUF/20wt%PEP, the degradation degree was obviously reduced, and an orientation of the cells along the stress direction and a density increase was observed. During aging at 200?°C, the retention of the mechanical properties of PUF/20wt% PEP was much higher than that of pure PUF, and it showed superior stability under heat and stress, attributed to incorporation of the thermally resistant oxazolidone rings and benzene rings in the PU backbones, the highly cross-linked networks of the polyurethane-epoxy systems and the obvious orientation of the cells under stress.     

Mechanical properties of silicon nanobeams with undercut evaluated by combining dynamic resonance test and finite element analysis

Mechanical properties of silicon nanobeams are of prime importance in nanoelectromechanical system applications. A numerical experimental method of determining resonant frequencies and Young's modulus of nanobeams by combining finite element analysis and frequency response tests based on an electrostatic excitation and visual detection by laser Doppler vibrometer is presented in this paper. Silicon nanobeams test structures are fabricated from silicon-on-insulator wafers by using a standard lithography and anisotropic wet etching release process, which inevitably generates the undercut of the nanobeam clamping. In conjunction with three-dimensional finite element numerical simulations incorporating the geometric undercut, dynamic resonance tests reveal that the undercut significantly reduces resonant frequencies of nanobeams due to the fact that it effectively increases the nanobeam length by a correct value Δ L, which is a key parameter that is correlated with deviations in the resonant frequencies predicted from the ideal Euler-Bernoulli beam theory and experimentally measured data. By using a least-square fit expression including Δ L, we finally extract Young's modulus from the measured resonance frequency versus effective length dependency and find that Young's modulus of silicon nanobeam with 200-nm thickness is close to that of bulk silicon. This result supports that the finite size effect due to surface effect does not play a role in mechanical elastic behaviour of silicon nanobeams with the thickness larger than 200 nm.     

Numerical analysis of non-confocal configurations of a hybrid stable-unstable resonator

The results of numerical simulations are reported modeling the behavior of a unidimensional Hybrid Stable-Unstable Resonator (HSUR) in strongly non-confocal configurations. Our analysis shows that such a resonator setup can produce cavity losses consistent with our design requirements and extract a Beam with Propagation Parameter better than 3 mm mrad.     

Mechanical properties an undercut evaluated resonance test and of silicon nanobeams with by combining the dynamic finite element analysis

Mechanical properties of silicon nanobeams are of prime importance in nanoelectromechanical system applications. A numerical experimental method of determining resonant frequencies and Young＇s modulus of nanobeams by combining finite element analysis and frequency response tests based on an electrostatic excitation and visual detection by using a laser Doppler vibrometer is presented in this paper. Silicon nanobeam test structures are fabricated from silicon-oninsulator wafers by using a standard lithography and anisotropic wet etching release process, which inevitably generates the undercut of the nanobeam clamping. In conjunction with three-dimensional finite element numerical simulations incorporating the geometric undercut, dynamic resonance tests reveal that the undercut significantly reduces resonant frequencies of nanobeams due to the fact that it effectively increases the nanobeam length by a correct value △L, which is a key parameter that is correlated with deviations in the resonant frequencies predicted from the ideal Euler-Bernoulli beam theory and experimentally measured data. By using a least-square fit expression including △L, we finally extract Young＇s modulus from the measured resonance frequency versus effective length dependency and find that Young＇s modulus of a silicon nanobeam with 200-nm thickness is close to that of bulk silicon. This result supports that the finite size effect due to the surface effect does not play a role in the mechanical elastic behaviour of silicon nanobeams with thickness larger than 200 nm.