Showing papers by "Keiji Enpuku published in 1995"
TL;DR: In this article, the authors proposed a method to evaluate the magnetic penetration depth and the surface resistance of superconducting thin films from the kinetic inductance measurement using coplanar waveguides.
Abstract: We have proposed a method to evaluate the magnetic penetration depth and the surface resistance of superconducting thin films from the kinetic inductance measurement using coplanar waveguides. The method utilizes the coplanar waveguide resonator where the temperature dependence of the resonant frequency due to the kinetic inductance is measured. Comparison between the observed data and an analytical expression using a conformal mapping technique gives the value of the magnetic penetration depth. The magnetic penetration depth of NbN thin films obtained in this way is shown to be in excellent agreement with that estimated from the dirty limit theory using resistivity and critical temperature. By applying this method to a YBaCuO resonator, we obtained the magnetic penetration depth /spl lambda/(0)=266 nm for a c-axis oriented film. Using the two-fluid model it is also shown that the surface resistance of the film can be evaluated from the quality factor and the kinetic inductance. We obtained the residual surface resistance Rs(0)=20 /spl mu//spl Omega/ at a frequency of 3.8 GHz. >
22 citations
TL;DR: Effects of cumulative ablation on the ejection of particulates and molecular species in pulsed‐laser deposition are studied by Mie scattering and laser‐induced fluorescence spectroscopy, respectively.
Abstract: Effects of cumulative ablation on the ejection of particulates and molecular species in pulsed‐laser deposition are studied by Mie scattering and laser‐induced fluorescence spectroscopy, respectively. When a fresh target is ablated, a large amount of particulates are ejected during several initial shots and rapidly decreased within the first ten shots of ablation. This is due to the ejection of powder residues which are struck on the target surface during the polishing process. After this period, ejection of particulates increased gradually and almost saturated after 200 shots. The saturation characteristic is empirically formulated as a function of the number of cumulative ablations. On the other hand, ejection of molecular species rapidly decreases during the initial 500 ablations and afterwards decreases more slowly with further ablation. The effects of cumulative ablation on the particle ejection are discussed in conjunction with the structural modification of the ablated surface observed by the scann...
13 citations
TL;DR: In this paper, a measurement circuit for the precise measurement of the kinetic inductance of superconducting thin films is developed for this purpose and the voltage across an inductance made of YBaCuO meander line is measured as a function of applied current from the nonlinear relationship between the voltage and the current measured in the experiment.
Abstract: Current-dependent kinetic inductance of superconducting thin films is studied experimentally A measurement circuit for the precise measurement of the kinetic inductance is developed for this purpose The voltage across an inductance made of YBaCuO meander line is measured as a function of applied current From the nonlinear relationship between the voltage and the current measured in the experiment, dependence of the kinetic inductance on the current is obtained The experimental results are consistent with the theoretical results predicted from the Ginzburg-Landau (GL) theory
8 citations
TL;DR: In this paper, two methods are proposed in order to improve the voltage modulation depth of high-T/sub c/DC SQUIDs in the case of large inductances, one is a damping resistance parallel to the inductance, and the other is a new SQUID using three junctions, which is called 3J-SQUID.
Abstract: Two methods are proposed in order to improve the voltage modulation depth of high-T/sub c/ DC SQUIDs in the case of large inductances. One is a damping resistance parallel to the inductance, and the other is a new SQUID using three junctions, which we call 3J-SQUID. Numerical simulation shows the usefulness of the present method. Moreover. It is shown that the improvement of the voltage modulation depth results in the improvement of magnetic flux noise in the white noise region. Therefore, the present method will enable the use of large inductances. The usefulness of the present method is also confirmed partly by experimental results. >
4 citations