交流剪力下所誘發物理系統的動力反應向來是個基礎且複雜的問題，其巨觀的反應由系統粒子間的交互作用力及型構所決定。經由巨觀的量測可得黏彈性係數，但其微觀下動力反應卻鮮為人知。在可直接觀測粒子運動的強耦合微粒電漿系統中，我們製作出一雪茄形狀的庫倫流體，利用雷射產生一外加交流之剪力推動庫倫團中長軸上的微粒，進而研究其微觀尺度下的黏彈性，討論微粒間如何反應外加的剪力及黏性與彈性的源由。此外，我們亦可調控雷射的頻率研究其頻率反應 ? 調控庫倫流體之溫度及大小，研究溫度及邊界的效應。 The AC shear-induced microscopic motions of dust particles in the strongly coupled Coulomb liquids in the rectangular plasma trap are investigated experimentally. In this work, the technique for confining a cigar-shaped elongated cluster in a rectangular cell is developed. A periodically chopped vertical laser sheet is ejected along the major axis of the cluster and introduced a strong shear. The visco-elastic response is observed on the displacements of particles under the AC external shear. For particles in the force chain regions, motions of particles demonstrate the microscopic origin of elastic response. However, position rearrangements of particles in the micro-vortex domains are responsible for the microscopic origin of viscous response. A damped transverse wave can be excited. After the laser is off, the slow relaxation comes from the complex relaxation processes among particles with different time delay motions. The frequency response, the temperature effect and the size effect are also studied in this series of experiments.
