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The AC susceptibility (χ + iχ ) of YBCO with and without intergrain coupling was measured in AC fields within 0.13 and 3.72 mT and frequencies from 20 Hz to 12.8 kHz. Intergrain coupling was eliminated by dispersing the powder in insulating varnish. For the coupled and uncoupled grains, the χ (T ) transition near T C is field independent, indicating that the fields used do not drive the sample into the mixed state. Thus, the χ and χ curves cannot be associated with vortex motion. In χ (T ), a peak near T C due to the intragrain response increases with applied AC field for both coupled and uncoupled grains. For the sample with sufficient grain coupling, a peak below T C shifts to low temperatures with increase in field. We attribute χ (T ) to eddy currents and explain its behaviour by taking into account the effect of the temperature dependence of the penetration depth and the electrical resistance on the eddy currents.

Photoluminescence properties of ZnO microstructures are investigated for potential scintillator applications. Samples are successfully prepared by the carbothermal reduction method. A single free-standing ZnO microribbon exhibits UV and visible emissions which behave differently along the microstructure.Fast UV emission lifetimes of 40 and 150 ps have been observed for the microstructures compared to 440 ps and 2 ns for a bulk crystal. With waveguided emissions and fast lifetimes, the ZnO microstructures have promising applications as future XFEL scintillators.

0.30, and 0.49 on an MgO (100) substrate was conducted using a Q-switched 1064 nm Nd:YAG laser The laser-produced plasma (LPP) emission was collected during the deposition. Time-resolved optical emission spectroscopy reveals that the plasma plume consists of neutral atoms and ions. SEM images indicate that clusters of correct stoichiometry arrive on the substrate surface. Our result confirms that IR PLD transfers material stoichiometrically. Keywords: pulsed laser deposition, plasma diagnostic techniques and instrumentation.Introduction. Pulsed laser deposition (PLD) has been extensively used in the fabrication of high-temperature superconductors such as Bi 2 Sr 2 CaCu2O 8+δ (Bi-2212) [1][2][3][4][5]. It is a flexible and straightforward technique effective in growing highly crystalline films with smooth surface morphology suitable for device applications [3,4]. Various parameters of the laser, target, and deposition conditions influence the quality of PLD films. The laser wavelength and energy density, nature of the target, and deposition time can be explored to achieve high-quality superconducting Bi-2212 films [1][2][3][4][5]. One of the challenges in PLD is the preservation of the stoichiometry between the target and the film. This was resolved recently by using an IR pulsed laser as an excitation source in fabricating Bi-2212 films [6].Most publications in PLD focus on the characterization of the films [3-8]. Only few reports are given regarding the correlation between the plasma plume and the properties of the grown film. The laser-produced plasma (LPP) formed during the ablation process provides information on the characteristics of the particles being transferred to the film [9]. Previous studies showed the effect of energy fluence from the UV laser source on the dynamics of the plasma expansion and the stoichiometry of BSCCO films [10]. One of the methods used to determine the plasma parameters is time-resolved optical emission spectroscopy. The radiation emitted by the plasma is collected, monitored, and analyzed spectroscopically during the various stages of the plasma evolution [11]. This technique is an effective way to determine the composition and other properties of the LPP [9,12,13].In this paper, we investigate the different plasma parameters of laser-produced Y-doped BSCCO plasma using time-resolved optical emission spectroscopy. The optical emission spectra were simultaneously collected with the laser deposition of Bi 2 Sr 2 Ca 1-x YxCu2O 8+δ films using a 1064 nm Q-switched Nd:YAG laser. The surface morphology, atomic composition, and transition temperature of the films with different Y concentrations were evaluated in consideration of the LPP spectra.Experimental. PLD was conducted in a vacuum chamber at a pressure of 10 -2 mbar for 180 min. The