Design,fabrication and characterization of the X-ray supermirrors

With the development of the multiplayer technology, the multilayer mirrors have been widely used in many fields, such as the soft X-ray astronomical telescope, soft X-ray microscopy, extreme ultraviolet lithography, applications of synchrotron radiation, plasma diagnosis, and so on. However, in the hard X-ray region, especially for the wavelength shorter than 0.1 nm, the optical elements based on the traditional multilayers or the single high-Z metal coatings cannot accommodate the advancemen…     

An open volume, high isolation, radio frequency surface coil system for pulsed magnetic resonance

We present an open volume, high isolation, RF system suitable for pulsed NMR and EPR spectrometers with reduced dead time. It comprises a set of three RF surface coils disposed with mutually parallel RF fields and a double-channel receiver (RX). Theoretical and experimental results obtained with a prototype operating at about 100 MHz are reported. Each surface RF coil (diameter 5.5 cm) was tuned to f₀ = 100.00 ± 0.01 MHz when isolated. Because of the mutual coupling and the geometry of the RF coils, only two resonances at f₁ = 97.94 MHz and f₂ = 101.85 MHz were observed. We show they are associated with two different RF field spatial distributions. In continuous mode (CW) operation the isolation between the TX coil and one of the RX coils (single-channel) was about −10 dB. By setting the double-channel RF assembly in subtraction mode the isolation values at f₁ or f₂ could be optimised to about −75 dB. Following a TX RF pulse (5 μs duration) an exponential decay with time constant of about 600 ns was observed. The isolation with single-channel RX coil was about −11 dB and it increased to about −47 dB with the double-channel RX in subtraction mode. Similar results were obtained with the RF pulse frequency selected to f₂ and also with shorter (500 ns) RF pulses. The above geometrical parameters and operating frequency of the RF assembly were selected as a model for potential applications in solid state NMR and in free radical EPR spectroscopy and imaging.     

储存环高频剔除系统

 介绍了用于电子储存环部分填充和非均匀填充的一种实验装置,它利用储存环中电子运动所具有的横向自由振荡和束团脉冲的时间结构这一特性,采用外加激励的方法使其产生共振,从而使得储存环中部分束团中的电子丢失,形成储存环的部分填充和非均匀填充。还扼要介绍了用高频剔除系统在储存环上实现不同填充方式时的束流积累结果。     

Nonlinear phase adjustment of selective excitation pulses

A continuous transformation of an RF waveform with a modified Korteweg-de Vries equation or generalization can be used to adjust the phase behavior of a selective excitation pulse while preserving the magnitude behavior of the spin response. This transformation has applications in removing or adding to the nonlinear phase properties of a selected region.     

间苯二酚-甲醛凝胶自发成膜技术研究

 以间苯二酚和甲醛为原料，对水相溶胶-凝胶聚合自发成膜技术获得间苯二酚-甲醛(RF)凝胶薄膜进行了研究。主要研究了溶胶-凝胶过程中冰醋酸（HAC）含量和反应温度对凝胶过程的影响，分析了RF有机凝胶自发成膜的形成机理。IR和SEM分析表明，所得到的凝胶膜具有典型的RF有机气凝胶结构，薄膜厚度大约为50 μm，膜由直径10 μm左右的粒子组成，没有观察到明显的孔洞结构。分析认为，在间苯二酚和甲醛占总溶液的质量分数为67％左右及控制pH值在一定的酸性范围，RF凝胶自发成膜过程和机理可以用RF凝胶的收缩机理加以解释，RF自发膜的表面形貌及形成机理与均匀泡沫的连续相分离机理类似。     

��Ƶ��Ӧ���������Langmiur̽��͹������

用Langmuir探针对射频(13.56 MHz)感应等离子体进行了诊断,给出了Ar等离子体轴向和径向参数随气压的变化。采用发射光谱测量了等离子体中氩原子的750.3nm谱线强度随气压在轴向的变化,其变化趋势与Langmuir探针测量结果的变化趋势相一致。测量了氩离子的434.8nm谱线强度随气压在轴向的变化并获得了氩离子的434.8nm谱线强度与氩原子的430.0nm谱线强度的比值在轴向三个不同位置的变化。从测得的结果可知:在放电室中上部形成了均匀稳定的高密度等离子体,在靶附近有所降低,在中部以下等离子体密度逐渐变低;在径向6~7 cm以内的区域等离子体参数变化不大,形成了均匀稳定的等离子体,等离子体参数在器壁处变化明显。     

基于傅立叶变换的射频场分布测量方法

提出了一种基于傅立叶变换的射频场分布测量方法，该方法可以方便地测量出射频场的分布，其测量结果与样品的均匀度无关并且可以分别观测某个像素点处的层内射频场非均匀性或某个小区域内的射频场非均匀性.     

Crystallization and electrical properties of V2O5 thin films prepared by RF sputtering

V₂O₅ thin films were prepared under various conditions by using reactive RF sputtering technique. The microstructure and electrical properties of the films are have been investigated. X-ray diffraction data revealed the films deposited at low O₂/Ar ratio are amorphous. The orthorhombic structure of film improved after post annealing at 873 K. The microstructure parameters (crystallite/domain size and macrostrain) have been evaluated by using a single order Voigt profile method. Using the two-point probe technique, the dark conductivity as a function of the condition parameters such as film thickness, oxygen content and temperature are discussed. It was also found that, the behaviour of ρd versus d was found to fit properly with the Fuchs-Sondheimer relation with the parameters: ρ_o = 2.14 × 10⁷ Ω cm and ?_o = 112 ± 2 nm. At high temperature, the electrical conductivity is dominated by grain boundaries, the values of activation energy and potential barrier height were 0.90 ± 0.02 eV and 0.92 ± 0.02 V, respectively.     

β=0.45, f=350 MHz Spoke腔的设计

近几年来,低b超导腔(例如spoke型，re-entrant 型,CH型)作为质子或者离子在中低能段的加速结构成为研究的热点.许多实验结果表明spoke腔在低能段是很好的选择,在中能段跟椭球腔相比也很具有竞争实力,为此,北京大学开展了β=0.45,频率为350MHz的spoke型质子超导加速腔研究. 本文详细阐述了这种腔的结构及电磁场的设计,从射频参数Q,r/Q,最大表面电磁场和加速效率的计算结果来看,它具有很好的加速性能.