Dusty plasma correlation function experiment

Abstract

Dust particles immersed within a plasma environment, such as those in protostellar clouds, planetary rings or cometary environments, will acquire an electric charge. If the ratio of the inter-particle potential energy to the average kinetic energy is high enough the particles will form either a ''liquid'' structure with short-range ordering or a crystalline structure with long range ordering. Many experiments have been conducted over the past several years on such colloidal plasmas to discover the nature of the crystals formed, but more work is needed to fully understand these complex colloidal systems. Most previous experiments have employed monodisperse spheres to form Coulomb crystals. However, in nature (as well as in most plasma processing environments) the distribution of particle sizes is more randomized and disperse. This paper reports experiments which were carried out in a GEC radio frequency reference cell modified for use as a dusty plasma system, using varying sizes of particles to determine the manner in which the correlation function depends upon the overall dust grain size distribution. (The correlation function determines the overall crystalline structure of the lattice.) Two-dimensional plasma crystals were formed of assorted glass spheres with specific size distributions in an argon plasma. Using various optical techniques, the pair correlation function was determined and compared to those calculated numerically.

Relationship Between the DC Bias and the Debye Length in a Complex Plasma

“…The signal generator is coupled to the electrode through an impedance matching network and a variable capacitor attenuator network. The plasma discharge apparatus is described in greater detail in [15], [16]. To measure the sheath thickness accurately is difficult, particularly when dust particles are present.…”

On the Optical Characterisation of Nanoparticle and their Aggregates in Plasma Systems

“…[50]). Therefore, PTV appears to be more appropriate for analysing the spatial distribution of particles within colloidal plasma crystals [51] or particle properties linked to their charge and dynamics in plasmas [52,53]. Particle imaging techniques are basically limited by the diffraction limit [49], making it impossible to image the surface and structure of sub-micron aggregates.…”

Measurement of the Vertical Nonuniformity of the Plasma Sheath in a Complex Plasma

“…Measured positions for melamine formaldehyde particles of diameter 8.89 ± 0.09 µm were recorded using a CCD camera at 120 frames per second for an argon gas plasma held at 100 mTorr under a rf power of 5W and frequency 13.56 MHz. The CASPER plasma discharge apparatus is described in greater detail in [13]. Representative dusty plasma parameters as measured experimentally during this experiment are given in Table 1.…”