Dusty plasmas have been the fastest growing subfield of plasma physics in the last two decades. Plasma or dust crystals are formed when the electrostatic coupling between grains is dominant. Plasma crystals resemble condensed matter at macroscopic level and exhibit unusual properties. We propose to carry out a novel experimental study on the interaction of plasma flows with dust crystals. Some of the questions that this project is aiming to elucidate are as follows. Will the plasma crystal preserve its 3-D structure and be carried by the plasma flow? How will a plasma-flow-dragged crystal or dust cloud interact with another plasma crystal? This project will address topics of utmost interest and actuality related to the plasma drag force exerted on dust grains, the potential around dust grains immersed in a plasma flow, collective effects due to dust-dust interactions, and propagation of ion-flow induced dust waves.
The main parts of the experimental set-up which will be designed and built in the first phase of the project include a coaxial plasma gun and a small size (~40 L) vacuum container provided with 2 parallel plate-electrodes. The plasma flow will be produced in a small coaxial gun by applying voltages of a few kVolts and currents no higher than a few kAmps. The plasma flow speed will be ~10 km/s. An rf plasma produced at low pressure between the parallel-plate electrodes will allow the formation of plasma crystals consisting of micron-size spherical grains, made of different materials such as plastic or carbon, in the sheath of the lower electrode. The electric force due to the sheath electric field will compensate for the microparticles’ weight and sustain them in equilibrium above the electrode. The coaxial gun will be attached sideway to the vacuum container such that the ejected plasma flow will be directed towards the plasma crystal.