The LHFZ processing set-up consists of a 100 Watt CO2 laser with dual beam heating optics and a controlled atmosphere growth chamber. A schematic diagram of the LHFZ set-up is shown below. Polycrystalline YBa2Cu3O7-x precursor fibers are mounted in chucks with two axes of rotation and two axes of triangulation. After alignment, the fibers are attached to the upper and lower pulling heads of the crystal grower. The two precursor fibers are then connected by heating the ends of the filaments with the laser beams and joining them. The dual laser beams are focused on opposite sides of the precursor fiber, producing a semisolid hot zone with temperatures between 1120 °C and 1160 °C. A semisolid zone of 1 to 2 fillament diameters,, composed of the Y2BaCuO5 phase and barium cuprate liquid, is established by using incident beams with diameters of 900 mm. The temperature of the hot zone is measured with a pyrometer and controlled using the laser current source.
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©CPRL, 1995