Experimental Modelling of Czochralski Melt Flow with a Slow Crystal Dummy Rotation
This study examines the e ect of slow crystal dummy rotation on three-dimensional oscillatory instability and time-dependent supercritical ow states in a Czochralski melt ow experimental model. To enable further comparison with numerical modelling, the experiments are carried out using a 20 cSt silicone oil as an experimental liquid and in a large diameter crucible, which allows one to work in a narrow temperature interval, so that temperature dependence of all the thermophysical properties of the experimental liquid can be neglected. The measurements con rm, partially qualitatively and partially quantitatively, earlier numerical predictions on destabilization ofthe Czochralski convective ow by a slow rotation. A simple power dependence of ow oscillations frequency on the Grashof and rotational Reynolds numbers that ts all the experimental runs was found.
Experimental investigation on the effect of crystal and crucible rotation on thermocapillary convection in a Czochralski configuration
Abstract Experimental investigation is conducted to understand the effects of crystal and crucible rotations on the thermocapillary convection in a Czochralski configuration. A transparent fluid (0.65cSt silicone oil with Pr  = 6.7) is contained in a cylindrical model crucible with the inner diameter of 92 mm and the depth of 2 mm. A copper disc with the diameter of 46 mm is used to simulate the crystal. The rotation rates of the crystal and crucible are 0 ∼ ± 60 rpm and 0 ∼ ± 1 rpm, respectively. Results indicate that there is a transition from stable axisymmetric flow to a three-dimensional oscillatory flow with the increase of the thermocapillary Reynolds number. The critical thermocapillary Reynolds number for the flow pattern transition decreases with the increase of the crystal rotation rate, and it is greater for the crystal–crucible co-rotation, compared to the counter-rotation. When the crystal rotation rate is small, the thermocapillary force is dominant, and the oscillatory flow behaves as the hydrothermal waves. The crystal rotation has only a slight effect on the wave number and propagation angle of the hydrothermal waves. At a high crystal rotation rate, the hydrothermal waves will transit to rotating waves. The temperature fluctuation of the hydrothermal waves is suppressed by the crucible rotation.
17 &mgr;m pixel 640 x 480 microbolometer FPA development at BAE Systems
BAE Systems has developed an advanced 640 x 480 focal plane array (FPA) with a 17 &mgr;m pixel pitch. Sensitivity of ≤ 50 mK was demonstrated and the FPAs were used in imaging demonstrations. Successful scaling of BAE Systems' patented single contact per pixel, single-level microbolometer process to 17 &mgr;m pitch provides a path toward next generation microbolometer imaging systems.