We fabricated Y 0.77 Gd 0.23 Ba 2 Cu 3 O y (Y,Gd)BCO and BaZrO 3 (BZO) nanoparticle doped (Y,Gd)BCO ((Y,Gd)BCO+BZO) films on CeO 2 buffered metallic substrates = coated conductor (CC) by using ...trifluoroacetate metal organic deposition (TFA-MOD). In this paper, in order to investigate the influence of grain-boundary angles of CeO 2 buffer layer (Δφ CeO2 ) on crystallinity and superconducting properties of (Y,Gd)BCO, the TFA-MOD films are fabricated on metallic substrates with various Δφ CeO2 . The Δφ of the superconducting layer decreases with decreasing Δφ CeO2 in both CCs. The self-field critical current density (J c s.f. ) of (Y,Gd)BCO+BZO CC with Δφ CeO2 = 2.0° is 5.8 MA/cm<;sup>2<;/sup> at 77 K, which is 1.5 times higher than that of CCs with Δφ CeO2 = 4.0°. Moreover, the (Y,Gd)BCO+BZO CC with Δφ CeO2 = 2.0° showed the minimum critical current density (J c,min ) of 0.81 MA/cm 2 at 77 K and 3 T. Thus, the improvement of the grain boundaries by using the improved buffer layer has an important role in the improvement of J c in TFA-MOD REBa 2 Cu 3 O y CCs.
Advanced Virgo phase cameras van der Schaaf, L; Agatsuma, K; van Beuzekom, M ...
Journal of physics. Conference series,
05/2016, Volume:
718, Issue:
7
Journal Article
Peer reviewed
Open access
A century after the prediction of gravitational waves, detectors have reached the sensitivity needed to proof their existence. One of them, the Virgo interferometer in Pisa, is presently being ...upgraded to Advanced Virgo (AdV) and will come into operation in 2016. The power stored in the interferometer arms raises from 20 to 700 kW. This increase is expected to introduce higher order modes in the beam, which could reduce the circulating power in the interferometer, limiting the sensitivity of the instrument. To suppress these higher-order modes, the core optics of Advanced Virgo is equipped with a thermal compensation system. Phase cameras, monitoring the real-time status of the beam constitute a critical component of this compensation system. These cameras measure the phases and amplitudes of the laser-light fields at the frequencies selected to control the interferometer. The measurement combines heterodyne detection with a scan of the wave front over a photodetector with pin-hole aperture. Three cameras observe the phase front of these laser sidebands. Two of them monitor the in-and output of the interferometer arms and the third one is used in the control of the aberrations introduced by the power recycling cavity. In this paper the working principle of the phase cameras is explained and some characteristic parameters are described.
Recently, affinity magnetic beads have been widely used in immunomagnetic cell sorting (IMCS) technology. Today, we can easily sort and analyze DNA and antibodies (immunoglobulin) using various types ...of affinity magnetic beads available in the market. The diameters of these affinity magnetic beads used in immunomagnetic cell sorting are limited to above approximately 1 mum because of the low magnetic fields induced by permanent magnets. Now, nano-sized affinity magnetic beads are strongly desired to achieve high resolutions. We have been studying and attempting to develop a high-gradient magnetic separation (HGMS) system that employs a superconducting magnet to induce a considerably higher magnetic field than that induced by a permanent magnet in order to trap smaller nano-sized affinity magnetic beads by a filter made of fine stainless steel wool. In this study, we constructed a prototype of a desktop-type HGMS system using a cryocooler-cooled LTS magnet and conducted preliminary experiments on trapping the nano-sized magnetic particles. Furthermore, we investigated the magnetic field distribution and magnetic force around a magnetic wire in the filter by means of a numerical simulation.
We have been developing an active magnetic levitation system, which is composed of a field-cooled disk-shaped or sphere-shaped high-temperature superconducting bulks (HTS bulks) and vertically piled ...ring-shaped electromagnets without an iron core. We suppose that this active magnetic levitation system can be applied to inertial nuclear fusion. In inertial nuclear fusion, one of the most important issues is to achieve high-accuracy position control of the fusion fuel, which consists of deuterium and tritium in order to evenly illuminate the entire surface of the target. Therefore, active magnetic levitation is applied to the levitation and position control of a sphere-shaped superconducting capsule containing nuclear fusion fuel. In this study, we designed and constructed a three-coil position control system in order to achieve the stable levitation of the sphere-shaped HTS bulk with a diameter of 5 mm by using the numerical simulation based on the hybrid finite element and boundary element analysis. Then, we carried out the experiments on the position control and restoring force characteristics of the sphere-shaped HTS bulk in the constructed levitation system.
In order to observe quantum radiation pressure noise and reduce it by measuring the ponderomotively squeezed light on a table-top experiment, we are developing a laser interferometer with Fabry-Perot ...cavities with very small suspended mirrors. As a preliminary setup, we have constructed a Fabry-Perot cavity of finesse 1300 with a suspended mirror of 20 mg. The cavity was locked stably at low laser power for which the classical radiation pressure caused little effect on the dynamics of the small mirror. For the stable operation of this cavity with higher laser power, a technique to control the motion of the small mirror, especially its yaw motion, is necessary. We describe that the motion can be stabilized through the radiation pressure of light inside the cavity, by controlling the motion of the front mirror of a Fabry-Perot cavity properly.
We measured the heat flow of current leads used for high-Tc superconducting apparatuses operating at liquid nitrogen temperature by the nitrogen boil-off method. To reduce the heat flow at the cold ...end of the current leads, the use of commercial Bi2223 silver-sheathed (Bi2223/Ag) tape conductors for current leads above liquid nitrogen temperature was also studied. We derived average Lorenz numbers between room temperature and liquid nitrogen temperature from the measurement results to assess the performance of the current leads. We tested Bi2223/Ag-soldered oxygen-free copper leads and obtained slightly lower heat flows and average Lorenz numbers than those of solid copper leads. The average Lorenz numbers of copper alloys were measured as well.
We have developed an active magnetic levitation system that comprises a field-cooled disk-shaped or sphere-shaped HTS bulk and multiple ring-shaped electromagnets. In this system, the levitation ...height of HTS bulk can be controlled by adjusting the operating current of each electromagnet individually. Further, the application of the vertical noncontact levitation system is expected due to its levitation stability without mechanical supports. We assume that this system is applied to inertial nuclear fusion. However, one of the important issues is to achieve position control with high accuracy of the fusion fuel in order to illuminate the target evenly over the entire surface. Therefore, this system is applied to the levitation and position control of a sphere-shaped superconducting capsule containing nuclear fusion fuel. In this study, we designed and constructed a position control system for the sphere-shaped HTS bulk with a diameter of 5 mm by using numerical simulation based on hybrid finite element and boundary element analysis. We then carried out the experiment of levitation height and position control characteristics of the HTS bulk in this system. With regard to position control, accuracies within 59 ?m are obtained.
A new seismic isolation system, TAMA Seismic Attenuation System (TAMA-SAS), was installed to TAMA300 in order to improve the sensitivity at low frequencies. Inertial damping is one of the ...hierarchical control systems of the TAMA-SAS which are employed to give full play to its ability. We have established two servo loops to control the Inverted Pendulum (IP) which composes the SAS. One is the servo loop using LVDT position sensors to keep the position of the IP. The other is the inertial damping which uses accelerometers to control the inertial motion of the IP for the horizontal direction. The fluctuation of the IP was reduced using our servo system. In addition, reduction of angular and longitudinal fluctuation of the mirror was also confirmed. These results indicate that the control for the IP properly works and the isolation performance of the TAMA-SAS was improved.
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