A 400 kHz, fast-sweep Langmuir probe for measuring plasma fluctuations

A novel, fast-sweep Langmuir probe has been constructed and successfully op erated on "Thorello." It is based on a novel, dual channel circuit that com pensates for stray capacitance and permits sweep speeds up to 400 kHz. The circuit response has been tested by measuring the known current-voltage cha racteristics of resistors and diodes. In addition, the probe has been used to measure the electron temperature and density as well as the plasma poten tial of plasmas generated in Thorello. A method of three-parameter curve fi tting is used to analyze the time-dependent data. The measurements compare favorably with those derived from other standard probe techniques. (C) 1999 American Institute of Physics. [S0034-6748(99)03006-3].