共查询到19条相似文献,搜索用时 125 毫秒
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超导谐振腔是超导加速器的关键部件.用于重离子超导加速器的低β加速腔的最佳选择是四分之一波长谐振腔(QWR).目前,利用无氧铜为基底,溅射一层几微米厚的铌膜,可以获得极好的超导性能和加速离子性能.但是,四分之一波长谐振腔的内表面复杂,溅射均匀的铌膜比较困难.针对此难题,发展了一种多参数可调节的溅射方法,在640×φ220的大型腔体内,成功地生成了一层均匀的、超导性能优异的铌膜.超导腔的低温实验表明铌膜的性能良好. 相似文献
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大晶粒铌材是射频超导领域的研究热点之一.采用大晶粒铌材的射频超导谐振腔,其后处理工艺可以大大简化.北京大学对此进行了深入细致的研究,自主研制了采用国产大晶粒铌材的射频超导腔,对这些超导腔进行了简单的表面处理,包括标准的化学抛光(BCP)和120.C低温烘烤处理,未进行非常复杂的电抛光处理,低温性能测试结果表明其低温超导性能优越,大晶粒1.3GHz超导腔的加速梯度达到了43.5MV/m,为我国超导加速器的国产化打下了基础. 相似文献
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射频超导谐振腔以其优越性在加速器领域起到了常温加速腔无法替代的作用. 超导腔的表面 特性直接影响到加速腔的性能. 为进一步提高超导腔的加速性能,北京大学利用超高真空氩 离子清洗技术发展了一种超导腔表面的干式处理方法. 与传统的湿处理方法(化学抛光BCP和 电抛光EP)相比,干式处理方法具有其特有的优点,有可能成为一种新的超导腔表面处理方 法,对提高加速腔的性能起到推动作用. 进一步的研究正在进行之中.
关键词:
射频超导
表面处理
溅射
抛光 相似文献
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上海光源是能量为3.5 GeV的第三代先进中能同步辐射光源,其储存环上安装了三台超导高频腔补偿电子因同步辐射等原因丢失的能量。为保障上海光源的长期稳定高效运行,中国科学院上海应用物理研究所和上海市低温超导高频腔技术重点实验室共同研制了具备低高次模损失参数和可承受更高入射功率的新型500 MHz超导腔,作为上海光源在线运行超导高频腔的备用腔。超导铌腔经低温垂直测试达到所需加速性能后,需要与高功率输入耦合器、高次模吸收器、低温恒温器等集成并完成水平测试,获得超导腔模组的加速性能、低温性能和真空性能。介绍了超导腔备用腔的研制、集成和测试过程,采用文丘里(Venturi)校准法获得模组的静态功耗反应模组的低温性能,并通过高功率测试获得了超导腔备用腔模组的加速性能。测试结果表明:自主研制的500 MHz超导腔备用腔满足上海光源的工作需求,在超导腔的加速腔压为2.0 MV时,无载品质因数为1.2×109 @4.2 K,且低温模组的静态热损耗为36.1 W。 相似文献
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Nb3Sn金属合金是一种性能优良的超导材料。磁控溅射多层沉积是用两个溅射源分层沉积铌和锡,再经过高温退火后获得超导薄膜的方法。用这种方法所获得的超导薄膜的原子组分的调整比较方便,对于Nb3Sn的研究较为有利。实验测量了样品的超导参数和晶格参数,其超导临界温度(Tc)可达17 K,剩余电阻率(RRR)为5左右。需要进一步研究相关工艺,以便提高RRR,从而使这种方法在超导加速腔的制造中得到应用。 相似文献
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The properties of Be films, quench-condensed upon a3He cooled substrate, have been investigated by resistance and tunneling measurements. The superconducting transition temperature,T c , of Be films increased with thickness and a thick film limit of 9.95 K could be estimated. Alloying with Al or Pb decreasedT c. The ratios between energy gaps andT c 's indicated that Be is a weak coupling superconductor, and no phonon induced structure could be traced in tunneling curves neither in pure Be nor in the Be based alloys. Resistance change during annealing as well as superconducting data indicated that the vapour quenched Be films were amorphous as deposited. 相似文献
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The effect of short-term low-temperature annealing in air and in vacuum on the properties of HTSC films of YBCO is studied. It is shown that, under certain conditions of preparation of initial samples, a transition from the HTSC phase with the superconducting transition temperature Tc=90 K to a phase with Tc=60 K occurs without a noticeable change in the oxygen content. It is found that, as a result of short-term annealings, a transition from the HTSC phase with Tc=60 K to the phase with Tc=90 K can occur only through the vacuum annealing stage, which converts the sample into the superconducting state. Short-term annealings lead to multiple reversible “switching” of the films from one phase to another. The obtained results are of practical interest, since the proposed method can be used to quickly obtain superconducting YBCO films in various phase states. It is shown, in addition, that the annealing procedure makes it possible not only to increase the oxygen concentration but also to produce a structural rearrangement of a YBCO film. 相似文献
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We studied the conductivity and superconducting transition temperature Tc of SnAr films. The films were prepared by condensing the SnAr mixture on a sapphire substrate held at 5 K. A plot of the conductivity as a function of Sn concentration shows a metal-insulator transition which agrees with a percolation model consisting of Sn clusters embedded in solid Ar. A drop of Tc is observed below the percolation threshold. 相似文献
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April O’Brien Brendon Villegas J.Y. Gu 《Physica C: Superconductivity and its Applications》2009,469(1):39-43
Magnesium diboride (MgB2) thin films were deposited on C-plane sapphire substrates by sputtering pure B and Mg targets at different substrate temperatures, and were followed by in situ annealing. A systematic study about the effects of the various growth and annealing parameters on the physical properties of MgB2 thin films showed that the substrate temperature is the most critical factor that determines the superconducting transition temperature (Tc), while annealing plays a minor role. There was no superconducting transition in the thin films grown at room temperature without post-annealing. The highest Tc of the samples grown at room temperature after the optimized annealing was 22 K. As the temperature of the substrate (Ts) increased, Tc rose. However, the maximum Ts was limited due to the low magnesium sticking coefficient and thus the Tc value was limited as well. The highest Tc, 29 K, was obtained for the sample deposited at 180 °C, annealed at 620 °C, and was subsequently annealed a second time at 800 °C. Three-dimensional (3D) AFM images clearly demonstrated that the thin films with no transition, or very low Tc, did not have the well-developed MgB2 grains while the films with higher Tc displayed the well-developed grains and smooth surface. Although the Tc of sputtered MgB2 films in the current work is lower than that for the bulk and ex situ annealed thin films, this work presents an important step towards the fabrication of MgB2 heterostructures using rather simple physical vapor deposition method such as sputtering. 相似文献
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We report superconducting measurements on NbN film () obtained by sputtering characterized by a columnar structure (grain size ? 120 Å). At the largest temperatures, the paraconductivity is tri-dimensional and of the Azlamasov-Larkin form. Near Tc it becomes bi-dimensional when 2ξ(T) is larger than the width of the sample. Below Tc, the behavior of the resistance is described in terms of phase-locking transition. The values of the corresponding critical exponents are discussed. 相似文献
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Ab initio calculations of the superconducting properties have been performed for niobium carbide (NbC) at normal pressure and upon a 15 and 30% compression. Factors accounting for the relatively low values of the transition temperature T c in transition metal carbides are considered and the possible ways of increasing this parameter are discussed. 相似文献
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Zhuang Cheng-gang An Ling Chen Li-ping Ding Li-li Zhang Kai-cheng Chen Chin-ping Xu Jun Feng Qing-rong Gan Zi-zhao 《Frontiers of Physics in China》2006,1(2):246-250
We fabricated several superconducting MgB2 thick films on stainless steel (SS) substrates by using hybrid physical-chemical vapor deposition (HPCVD) technique. The
thickness was in the 10μm to 20μm range, and the onset critical transition temperature T
c (onset) and the width of the superconducting transition (ΔT) were about 37.8 and 1.2 K. They were dense and textured along (101) direction with high tenacity, despite the existence
of a little amount of MgO and Mg. We bent the films at different degrees and studied the ductility and transport properties
of these MgB2 thick films under applied force. The results demonstrated that the superconducting properties of these thick films, prepared
by HPCVD, stay almost unaffected even with the films bent to a large degree with a curvature of 0.5 mm. This indicated that
the superconducting wires or tapes of MgB2 with a core of SS had the advantages of avoiding rigidity and brittleness in industrial handling. The technique of HPCVD
has, therefore, a high application potential.
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Translated from Chinese Journal of Low Temperature Physics, 2005, 27(2) (in Chinese) 相似文献
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B. Schröder W. Grobman W.L. Johnson C.C. Tsuei P. Chaudhari 《Solid State Communications》1978,28(8):631-633
Ultraviolet photoemission measurements at two photon energies are carried out, to understand the strong enhancement of the superconducting transition temperature Tc in the nitrogen stabilized amorphous molybdenum films. The rise of Tc can be attributed to a 40% increase of the electronic density of states at the Fermi level N(EF) and a 15% softening of the phonon spectrum. 相似文献