New radio-frequency setup for studying large 2D complex plasma crystals

Complex plasma crystals are popular model systems where various plasma-specific or generic phenomena can be studied at the level of individual particles. Addressing the growing need for larger two-dimensional (2D) plasma crystals, a new plasma setup was built at the DLR Institute of Materials Physics in Space. The setup allows obtaining larger than before, highly ordered 2D plasma crystals and exploring new parameter ranges. It is based on a relatively large (90 cm in diameter) vacuum chamber where a capacitively coupled radio-frequency discharge is used to levitate polymer microparticles. The discharge is created between the lower rf electrode and the grounded chamber walls, the particles levitate in the plasma (pre)sheath above the electrode and are observed by video microscopy through the large top glass window and through the side windows. The first observations of plasma crystals in the new setup are reported.