A New Instrument for Thermal Electron Attachment at High Temperature: NF3 and CH3Cl Attachment Rate Constants up to 1100 K
AIR FORCE RESEARCH LAB HANSCOM AFB MA SPACE VEHICLES DIRECTORATE
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A new high temperature flowing afterglow Langmuir probe HT-FALP apparatus is described. A movable Langmuir probe and a four-needle reactant gas inlet were fitted to an existing high temperature flowing afterglow apparatus. The instrument is suitable for study of electron attachment from 300-1200 K, the upper limit set to avoid softening of the quartz flow tube. We present results for two reactions over extended ranges NF3 300-900 K and CH3Cl 600-1100 K. Electron attachment rate constants for NF3 had been measured earlier using our conventional FALP apparatus. Those measurements were repeated with the FALP and then extended to 900 K with the HT-FALP. CH3Cl attaches electrons too weakly to study with the low temperature FALP but reaches a value of 10exp -9 cu cms at 1100 K. F- is produced in NF3 attachment at all temperatures and Cl- in CH3Cl attachment, as determined by a quadrupole mass spectrometer at the end of the flow tube. Future modifications to increase the plasma density should allow study of electron-ion recombination at high temperatures.
- Physical Chemistry
- Plasma Physics and Magnetohydrodynamics