Experimental study of CF4 conical theta pinch plasmaexpanding into vacuum

Langmuir probe, photodiode, and optical multichannel analyzer (OMA) measurements have been made on a pulsed CF₄ conical theta-pinch plasma. A cloud of CF₄ was puffed into a conical theta-pinch coil, converted to plasma, and propelled into the vacuum region ahead of the expanding gas cloud. At a position 67 cm away from the conical theta-pinch coil, the plasma arrived in separate packets that were about 20 μs in duration. The average drift velocity of these packets corresponded to an energy of about 3 eV. The OMA measurements showed that the second packet contained neutral atomic fluorine as well as charged particles. The electron temperature and ion density in the second packet were 2.0 eV and 1.5×10¹³ cm^-3, respectively. The electron temperature and ion density in the wake plasma were 8.3 eV and 4×10¹¹ cm^-3 , respectively. This device can be used for plasma processing or as a laboratory test of numerical and analytical models of the expansion of plasma into vacuum