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131.
RF deflecting cavity can be used for bunch length measurement and is designed to diagnose the beam produced by the photocathode electron gun which was built at Tsinghua University for the Thomson scattering experiment. Detailed discussion and calculation for measuring the 3.5 MeV bunch and another with further acceleration to 50 MeV, which is under development, are presented. A standing-wave deflecting cavity working at 2856 MHz is designed and the power feeding system has been planned. 相似文献
132.
2004—2007年BEPC高频系统从常温腔改建到超导腔, 逐渐解决了改频的物理问题和超导技术的工程难题, 实现了与国际先进技术接轨, 并按期保质完成了工程、调束任务. 高频系统是BEPCⅡ工程首个吸收国外超导技术、自主完成集成和调试成功的大型装置; 2006年7月国内首次超导高频大功率试验成功; 2006年11月完成系统联调, 按期投入BEPCⅡ首轮调束; 同年12月首次投入同步辐射运行; 2007年2至5月, 东、西两套超导高频系统在1MV以上的加速电压均已实现正/负电子1.89GeV注入积累和110/114mA对撞; 在同步辐射运行中, 逐渐达到2.5GeV/250mA、束流功率100kW, 接近国外同类机器水平; 束流试验证明两套高频系统的 相似文献
133.
Aluminium and copper prototype cavities were designed to study higher order modes (HOM). An automatic field mapping system was developed with LabVIEW to measure the radiofrequency (RF) characteristics, such as resonant frequency, Q-value, shunt impedance and electromagnetic field distribution of the higher-order modes in a model RF cavity. Two kinds of the bell-shaped cavities were measured using the field mapping system, their frequencies are 1.5GHz and 800~MHz respectively. The fields' distributions of the monopole modes and dipole modes, as well the R/Q values, were measured. 相似文献
134.
This study employs RF magnetron sputter technique to deposit high C-axis preferred orientation ZnO thin film on silicon substrate, which is then used as the piezoelectric thin film for a thin film bulk acoustic resonator (FBAR). Electrical properties of the FBAR component were investigated by sputtering a ZnO thin film on various bottom electrode materials, as well as varying sputter power, sputter pressure, substrate temperature, argon and oxygen flow rate ratio, so that structural parameters of each layer were changed. The experimental results show that when sputter power is 200 W, sputter pressure is 10 mTorr, substrate temperature is 300 °C, and argon to oxygen ratio is 4:6, the ZnO thin film has high C-axis preferred orientation. The FBAR component made in this experiment show that different bottom electrode materials have great impact on components. In the experiment, the Pt bottom electrode resonant frequency was clearly lower than the Mo bottom electrode resonant frequency, because Pt has higher mass density and lower acoustic wave rate. The component resonant frequency will decrease as ZnO thin film thickness increases; when top electrode thickness is higher, its resonant frequency also drops, due to top electrode mass loading effect and increased acoustic wave path. Therefore, ZnO thin film and top/bottom electrode thickness can be fine-tuned according to the required resonant frequency. 相似文献
135.
Mukesh Kumar Alaria A. K. Sinha A. Bera V. Srivastava 《International Journal of Infrared and Millimeter Waves》2008,29(12):1083-1090
The main objective of the paper is to make an efficient design of the input and output coaxial coupler for a helix TWTs. An
approach has been developed for the efficient design and analysis of the coaxial couplers in the practical situation. Normally
multi-section impedance transformer approach is used for any wide band coupler. For a space helix TWT, coupler should be wide
bandwidth and small size. In this case coupler is matched with helix slow wave structure and the standard 50-ohm connectors.
The simulated return loss (dB) profile for different type of couplers is obtained by using Ansoft HFSS, CST microwave studio
and compares those with experimental results. The tip loss design at sever ends for the input and the output section has been
also optimized. 相似文献
136.
J. Zafar H. Zafar K. Masood A. A. P. Gibson 《International Journal of Infrared and Millimeter Waves》2008,29(12):1205-1214
High power line source emitter assembly was coupled to a twin symmetric H-plane slab loaded accelerating structure for beam
acceleration. Closed form field analysis of the accelerating structure that includes guideline information regarding modal
hierarchy, mode nomenclature, propagation plane, cut-off plane and dispersion relations is presented. Furthermore it was confirmed
that by using symmetrically loaded dielectric accelerating structures with one rotated through 90° results in exerting a uniform
acceleration impact on a travelling beam passing through the structure. 相似文献
137.
Noury F Mispelter J Szeremeta F Même S Doan BT Beloeil JC 《Magnetic resonance imaging》2008,26(10):1421-1432
Intervertebral disc (IVD) degeneration is a complex process characterized by biochemical and structural changes in both the nucleus pulposus and the anulus fibrosus. In this study, we were able to obtain in vivo magnetic resonance (MR) images of the rabbit spine, with several MR imaging (MRI) contrasts (ρ, T1 and T2). We quantified several parameters (T2, apparent diffusion coefficient, disc height and area) to differentiate between healthy and degenerative IVDs and to characterize the degeneration process. To our knowledge, there has not been any previous in vivo study of rabbit IVDs at high-field MRI (9.4 T).A custom radio frequency (RF) coil for 9.4 T was designed to match rabbit IVD morphology, to study the degeneration in vivo on a model of human lumbar disease. Our new probe, a custom half-birdcage-type coil, obtains the necessary exploration depth while meeting the requirements for signal homogeneity and sensitivity of the study. This design addresses some of the difficulties with constructing RF coils at high field strengths. 相似文献
138.
Exploring the feasibility of simultaneous electroencephalography/functional magnetic resonance imaging at 7 T 总被引:1,自引:0,他引:1
The increased blood oxygenation level-dependent contrast available at high field makes the implementation of combined EEG/fMRI experiments at 7 T highly worthwhile from the point of view of fMRI data quality, but the higher field poses greater technical challenges for achieving good quality EEG data. A study of the feasibility of recording EEG signals from human subjects at 7 T using a commercially available, MR-compatible EEG system has therefore been carried out. This involved systematic measurement of the sources of noise in EEG recordings made in the 7 T scanner and measurement of RF heating effects on a gel phantom in the presence of a 32-electrode EEG cap. Having found no significant safety concerns and identified a set-up (involving switching off the magnet's cryo-cooler pumps and mounting the EEG amplifier on a cantilever) that limited scanner-induced noise, combined EEG/fMRI experiments employing visual stimulation were then successfully carried out on two human subjects. With the use of beamformer-based analysis of the EEG data, driven responses and alpha-band, event-related desynchronisation were identified in both subjects. 相似文献
139.
Wang ZJ 《Magnetic resonance imaging》2008,26(9):1310-1315
A complete RF coil system, as has been previously defined, is capable of generating any steady-state RF field, at the MR frequency, that is compatible with Maxwell's equations. A coil system is complete if it is capable of generating all basis vector fields in the multipole expansion of the electromagnetic fields. A complete coil system has the potential to reach the ultimate intrinsic signal-to-noise as an MRI receiver coil. It also offers maximum flexibility in tailoring the spatial RF field distribution as an excitation coil. Here, computer simulations have been performed on array coils employing composite coil elements, assuming the current loops are small and can be approximated by magnetic dipoles. We demonstrate that a coil array can be configured to approximate a truncated complete array coil and to generate the basis magnetic vector fields up to certain orders in the multipole expansion of the electromagnetic fields. 相似文献
140.
《Surface and interface analysis : SIA》2018,50(2):138-145
Copper‐tin thin films (CT TFs) were deposited on p‐type Si(100) by radio frequency (RF) magnetron co‐sputtering method. The atomic ratio of Cu and Sn showed complementary tendency with various RF powers on metal targets. Antibacterial test was conducted with Gram‐negative Escherichia coli. The ratio of Cu and Sn ions and the contact time with E. coli affected the antibacterial efficiency. Increasing the ratio of Cu ions and contact time showed higher antibacterial activity. Cu20Sn6 called as bronze structure, metallic Cu, and copper oxide phases were identified from X‐ray diffraction data after sterilization. The lattice strain that was changed due to the substitution of Cu and Sn was also calculated. The surface morphology of CT TFs was entirely grown to round shape when the dominant element was Sn. But, as the content of Cu increased, the surface morphology was changed from ball shape to sharp column shape. When fixed contact time, the intensities of Cu 2p increased but the intensities of Sn 3d decreased as increasing the atomic ratio of Cu. The oxidation of Cu was more sharply progressed as the RF power on Cu target increased. When fixed CT TFs, the intensities of Cu 2p were consistent but the intensities of Sn 3d3/2 decreased as increasing contact time between CT TF and E. coli. 相似文献