Microcalorimetry of dust particles in a radio-frequency plasma

Abstract

The internal temperature of rhodamine B-dyed dust particles (2r p ϭ1.2 m) immersed in radio-frequency ͑rf͒ plasmas has been measured for various plasma conditions. For this purpose, the dye has been excited with an argon-ion laser and the fluorescent emission of the particles has been recorded with an optical multichannel analyzer system. The temperature has been determined after comparison with calibration curves. In argon, the particle temperature increases with rf power and is independent of pressure. In oxygen, an increase with rf power is observed, too. However, the energy flux towards the particles includes also heating by atom recombination ͑association͒ and exothermic combustion reactions. These temperature measurements have been compared with calculations based on the thermal balance, where measurements of gas temperature, electron density, and electron temperature have been used. A good agreement between theory and experiment has been found.

Basic Processes in Complex (Dusty) Plasmas: Charging, Interactions, and Ion Drag Force

“…Experiments and theoretical estimations demonstrated that in low pressure gas discharges the particle surface temperature is somewhat hotter that the neutral gas temperature [81,112,113]. Recent estimation has shown that under typical discharge conditions the magnitude of neutral shadowing is usually weaker compared to ion shadowing and electric interactions [81].…”

On the heating of nano- and microparticles in process plasmas

“…The accommodation coefficient of the microparticles is estimated to be α μ ≈ 0.86 [34,47]. The emissivity is estimated to be ε = 0,5 [58].…”

“…Rhodamine-B dyed melamine-formaldehyde particles, and compared their temperaturedependent emission spectrum in the plasma to spectra from a calibration oven [47]. Oliver and Enikov measured the incandescent radiation from particles in a plasma jet, which of course is only possible at rather high particle temperatures above 1000 K [46].…”

“…Several studies addressed the grain temperature, both theoretically [39][40][41][42] and experimentally [33,34,[43][44][45][46][47]. For example, Daugherty and Graves measured the temperature-dependent decay time of the fluorescence of manganese activated magnesium fluorogermanate particles in a pulsed argon discharge during the plasma-off phase [43].…”

“…Then, the integral energy influx density J in is balanced by integral energy loss density J out due to radiation and conduction to the environment [42,47] …”