142.8MHz次谐波聚束腔的结构优化设计

使用二维有限差分法分析软件Superfish和三维有限积分法分析软件MAFIA,对142.8MHz次谐波聚束腔的结构进行了模拟和优化研究,给出了聚束腔结构优化设计的步骤和方法,确定了优化后聚束腔的基本结构。分析比较了Superfish和MAFIA两个软件的模拟优化结果,得出了基本一致的结论。还探讨了Superfish和MAFIA在聚束腔设计中的应用方法。     

142.8MHz次谐波聚束腔的结构优化设计

 使用二维有限差分法分析软件Superfish和三维有限积分法分析软件MAFIA，对142.8MHz次谐波聚束腔的结构进行了模拟和优化研究，给出了聚束腔结构优化设计的步骤和方法，确定了优化后聚束腔的基本结构。分析比较了Superfish和MAFIA两个软件的模拟优化结果，得出了基本一致的结论。还探讨了Superfish和MAFIA在聚束腔设计中的应用方法。     

核运动对非奇次谐波产生的影响

理论研究了H2+、D2+、T2+辐射高次谐波的特点.结果表明,在核运动影响下,不仅奇次谐波呈现红移现象,而且谐波光谱呈现非奇次谐波.随着核质量增大,奇次谐波频移和非几次谐波强度都减弱.但是随着激脉宽增大,非奇次谐波的产生明显被增强.理论分析表明,谐波频移是由谐波辐射在激光上升和下降区间的非对称性导致的;非奇次谐波是由于分子对称性在较大核间距离处遭破坏产生的.     

次谐波聚束系统固态放大器相位特性

 为研究BEPCⅡ直线加速器次谐波聚束系统使用的两台固态放大器（20 kW/142.8 MHz,10 kW/571.2 MHz）的相位特性,利用基于现场可编程门阵列(FPGA)的数字测量方法对两台固态放大器的脉内相移和相位稳定度进行了测量。测量系统硬件包括频率综合器、FPGA数字信号处理板和PC;软件部分包括FPGA内部算法、通信及PC端界面程序。该测量系统能真实地反映两台固态放大器的相位特性,为次谐波聚束器的相位补偿提供了参考。     

热透镜效应对半整块腔型中二次谐波过程的影响

二次谐波过程是制备高功率、宽波长范围激光的有效途径.在二次谐波过程中,晶体的热透镜效应是限制转换效率进一步提高的重要因素,热透镜效应对二次谐波转换效率的影响随着基频光功率的增大而加剧.本文理论分析了不同半整块腔型中热透镜效应对转换效率的影响关系;实验上搭建了两种腔型进行高效外腔倍频制备532 nm激光,测量其倍频转换效率随基频光功率的变化关系.对于平凹型半整块腔,在输入光功率为800 mW时,产生747 mW的532 nm激光输出,得到最佳的转换效率为93.4%±3%;对于双凹型半整块腔,在输入光功率为600 mW时,产生529 mW的532 nm激光输出,得到的最佳转换效率为88.2%±3%.研究表明,热透镜效应对双凹型半整块腔的转换效率影响相对较大,且随着腔内损耗的增加而加剧;相比于双凹型半整块腔,平凹型结构可以实现更高效的倍频转换.本文的理论及实验结果可在量子信息科学、光学频率计量以及生物医学等领域的研究中发挥重要作用.     

BEPCII次谐波聚束系统物理公差要求的研究

 为了进一步提高束流品质并逐步采用双束加速技术, BEPCII直线加速器准备采用带有两个次谐波聚束器的双次谐波聚束系统。目前, 该次谐波聚束系统的物理设计和优化已经基本完成。由于新设计的双次谐波聚束系统很不同于BEPCII现有的聚束系统, 因此, 就要求对聚束系统中存在的各种抖动(jitter)效应重新进行研究。 使用多粒子模拟计算程序PARMELA对电子枪的高压抖动和定时抖动、次谐波聚束器的相位抖动以及功率抖动、聚束器中加速电场相位以及A0加速管(俘获加速节)中加速电场相位的抖动等效应进行了研究, 并最终确定了聚束系统中各部件的物理公差要求。     

BEPCII次谐波聚束系统物理公差要求的研究

为了进一步提高束流品质并逐步采用双束加速技术, BEPCII直线加速器准备采用带有两个次谐波聚束器的双次谐波聚束系统。目前, 该次谐波聚束系统的物理设计和优化已经基本完成。由于新设计的双次谐波聚束系统很不同于BEPCII现有的聚束系统, 因此, 就要求对聚束系统中存在的各种抖动(jitter)效应重新进行研究。 使用多粒子模拟计算程序PARMELA对电子枪的高压抖动和定时抖动、次谐波聚束器的相位抖动以及功率抖动、聚束器中加速电场相位以及A0加速管(俘获加速节)中加速电场相位的抖动等效应进行了研究, 并最终确定了聚束系统中各部件的物理公差要求。     

交直交型机车的高频谐波混沌分析

针对典型的交直交型动车组CRH2车型,推导出其在正弦脉宽调制下的参数方程,并建立一套新的非线性参数模型.通过混沌原理分析了高次谐波的分形情况,并针对典型的牵引变电站,进行了计算和仿真,依托实际录波的数据验证,证实高频谐波能够导致系统谐振,为混沌分析方法拓展了新的应用.     

速调管输入腔开放腔的高频特性分析与实验研究

建立了带输入波导结构的S波段速调管放大器输入腔开放腔模型,利用3维软件对其高频特性进行了数值计算研究,并对输入腔结构进行了优化设计。利用已加工的输入腔进行了高频参数的冷测实验研究,实验中的输入腔结构尺寸与高频分析中的完全相同,实验结果与高频分析结果一致。用3维PIC程序对电子束经过该输入腔后的束流调制以及注入微波的吸收情况进行了模拟。模拟结果表明：该输入腔与微波注入波导匹配很好,注入微波能被电子束和谐振腔全部吸收,在输入腔间隙后37 cm处得到了13%的基波电流调制深度。     

相对传播的双脉冲激光与薄膜靶作用产生的强单色谐波

研究了相对传播的双脉冲激光与薄膜靶的作用,观察到很强的谐波产生.其物理图像是:圆偏振高对比度强激光脉冲作用于薄膜靶,由光压推动产生的高密度等离子体靶向前运动,同时由于电荷分离场的作用,使得离子束和电子束在纵向上都有好的聚束,从而产生以相对论速度向前运动的等离子体镜;反向入射一个探测光到已被加速的等离子体镜上,由多普勒频移产生强的单色N次谐波,探测光脉冲被"压缩"至原来的1/N.还讨论了激光和等离子体参数对等离子体镜的运动和谐波级次的影响,以及相对论运动等离子体镜的稳定性对谐波的影响.     

射频超导谐振腔中的电磁场研究

由高纯铌制成的射频超导谐振腔在高场时会出现Q值下降现象，这是高场下超导腔表面局部磁场增强所致. 为研究高场下超导腔表面的电磁场特性，用单cell超导腔设计了腔表面峰值磁场的研究实验. 通过对单cell超导腔表面峰值磁场的测量，可以确定超导腔焊缝及iris附近表面是否存在缺陷，以便进一步进行腔的处理来改进腔的性能.     

Effect of driving frequency on electron heating in capacitively coupled RF argon glow discharges at low pressure

A one-dimensional(1D) fluid model on capacitively coupled radio frequency(RF) argon glow discharge between parallel-plates electrodes at low pressure is established to test the effect of the driving frequency on electron heating. The model is solved numerically by a finite difference method. The numerical results show that the discharge process may be divided into three stages: the growing rapidly stage, the growing slowly stage, and the steady stage. In the steady stage,the maximal electron density increases as the driving frequency increases. The results show that the discharge region has three parts: the powered electrode sheath region, the bulk plasma region and the grounded electrode sheath region. In the growing rapidly stage(at 18 μs), the results of the cycle-averaged electric field, electron temperature, electron density, and electric potentials for the driving frequencies of 3.39, 6.78, 13.56, and 27.12 MHz are compared, respectively. Furthermore,the results of cycle-averaged electron pressure cooling, electron ohmic heating, electron heating, and electron energy loss for the driving frequencies of 3.39, 6.78, 13.56, and 27.12 MHz are discussed, respectively. It is also found that the effect of the cycle-averaged electron pressure cooling on the electrons is to "cool" the electrons; the effect of the electron ohmic heating on the electrons is always to "heat" the electrons; the effect of the cycle-averaged electron ohmic heating on the electrons is stronger than the effect of the cycle-averaged electron pressure cooling on the electrons in the discharge region except in the regions near the electrodes. Therefore, the effect of the cycle-averaged electron heating on the electrons is to "heat" the electrons in the discharge region except in the regions near the electrodes. However, in the regions near the electrodes, the effect of the cycle-averaged electron heating on the electron is to "cool" the electrons. Finally, the space distributions of the electron pressure cooling the electron ohmic heating and the electron heating at 1/4 T, 2/4 T, 3/4 T, and 4/4 T in one RF-cycle are presented and compared.     

高频环行器打火原因的分析

合肥光源(HLS)储存环高频系统环行器在工作中出现了两种形式的打火——谐波打火和束流丢失打火. 谐波打火的原因已经找到并予以解决, 但丢束打火的机制尚未明确. 文中描述了丢束后高频系统的响应过程, 分析了一些可能造成环行器打火的因素. 为了防止环行器打火受损, 建立了快速联锁保护电路, 该电路在历次打火中成功地保护了环行器.     

Matrix method for the solution of RF field perturbations due to local frequency shifts

To tune the accelerating field to the design value in a periodical radio frequency accelerating structure, Slater's perturbation theorem is commonly used. This theorem solves a second-order differential equation to obtain the electrical field variation due to a local frequency shift. The solution becomes very difficult for a complex distribution of the local frequency shifts. Noticing the similarity between the field perturbation equation and the equation describing the transverse motion of a particle in a quadrupole channel, we propose in this paper a new method in which the transfer matrix method is applied to the field calculation instead of directly solving the differential equation. The advantage of the matrix method is illustrated in examples.     

相对论电子束对波的相速的影响

在小信号情况下研究了相对论电子束对加速器微波相速的影响.首次提出了电子束流的介质等效的思想,并建立了等效的相对介电常数的计算公式.同时,建立了考虑小信号下相对论电子束的盘荷波导的简化色散方程.     

Thermal analysis and water-cooling design of the CSNS MEBT 324 MHz buncher cavity

At least two bunchers are needed in the 3 MeV H- Medium Energy Beam Transport(MEBT)line located between RFQ and DTL for the CSNS(China Spallation Neutron Source).A nose-cone geometry has been adopted as the type of buncher cavity for its simplicity,higher impedance and lower risk of multipacting.By making use of the results got from the simulations on the buncher with two-dimension code SUPERFISH,the thermal and structural analyses have been carried out,the process and results to determine the resulting frequency shift due to thermal and structural distortion of the cavity are presented,the water-cooling channel position and the optimum cooling water temperature as well as the tuning method by adjusting the cooling water temperature when the cavity is out of resonance are also determined through the analyses.     

斯塔克效应对两模双光子J-C模型腔场谱的影响

研究了斯塔克(Stark)效应对两模双光子Jaynes-Cummings(J-C)模型腔场谱的影响,推导计算出了腔场处于光子数态时腔场谱的计算公式和数值结果,讨论了斯塔克效应和初始场强对腔场谱的影响。发现斯塔克效应在弱场条件下对腔场谱线的频率和强度都有明显的影响,破坏了谱结构的对称性,使两模的谱线更加丰富。初始场较强时斯塔克效应对谱线的影响较弱。模Ⅰ为真空场、模Ⅱ初始场强递增时,斯塔克效应使模Ⅱ的高频峰受到较强的抑制作用,其低频峰在初始场较弱时受到抑制,初始场较强时又有强化作用,初始场更强时,模Ⅱ的谱线退化为经典的共振荧光谱,与无斯塔克效应的情况基本相同。     

Electron Spin–Nuclear Spin Cross-Correlation Effects on Multiplet Splittings in Paramagnetic Proteins

The effects of cross-correlation between Curie spin–nuclear dipole and nuclear dipole–nuclear dipole interactions on the linewidths and resonance frequencies of the individual lines of anAXmultiplet in paramagnetic systems have been calculated. The implication of the relaxation-induced frequency shift of the lines (dynamic frequency shift) for the accurate measurement of residual dipolar couplings in field-oriented systems has been discussed. Our simulations indicate that these effects may play a role in the precise measurement of residual dipolar couplings in systems which belong to the small and intermediate tumbling regime, i.e., correlation times less than 5 ns.     

The influence of annealing on the properties of ZnO:Al layers obtained by RF magnetron sputtering

Al doped ZnO has been explored as a viable alternative to indium thin oxide, which is usually used as transparent electrodes' coverage but is expensive. Homogenous and durable ZnO:Al layers on glass have been obtained in radio frequency magnetron sputtering system by adjusting optimized deposition parameters, using ZnO ceramic target with 2?wt% Al₂O₃. Then, after growth process, annealing treatment has been introduced in order to improve the quality of the layers. Structural, electrical and optical properties of the obtained ZnO:Al layers are presented and discussed. From the application point of view, the best results (sheet resistance of 24 Ω/sq and transparency well above 85%) were achieved after annealing in 300?°C.     

外电场作用下三元环状水分子团簇的特性研究

采用了HartreeFork自洽场方法在321G水平上研究了0～0.01a.u.的外电场对三元环状水分子团(H2O)3基态能量和电偶极距的影响规律,分析了由外电场产生的HellmanFeynman(HF)力(内力和外力)和在这个力的平衡作用下的团簇的稳定结构,结果表明,外电场的大小对三元环状水分子团簇(H2O)3这些性质有明显的影响.通过高斯计算可以得出,在所加的电场范围内,随着外电场的增大总能量下降,电偶极距增大,结构相对更稳定;外电场引起团簇中各个原子的电荷密度改变,导致了各个原子所受的静电力随之变化.