TERMIUM Plus^®

Record 1,  Textual support,  English

Record number: 1, Textual support number: 1 CONT

Thermionic or Electron Impact Detector. In 1957, Ryce and Bryce described a sensitive ionization gauge based on the ionization potentials of vapors. It comprised a filament, a grid, and a plate. The potential difference between the filament and grid accelerated electrons which may ionize any gas in their path. If the grid potential is maintained at a level insufficient to ionize the helium carrier gas ... no current flows in the plate circuit. If a potential difference of 18 V is maintained between the filament and the grid, compounds of lower ionization potential in the helium will be ionized and the positive ions produced will yield a cathode current, the current noted being a measure of the ion concentration. Into the modified ionizing chamber, operated at reduced pressure, a small fraction of the column effluent gas stream (less than 0.5%) was allowed to flow into the gauge through a controlled leak. Over a 0.02-l.5 mm Hg pressure range, the sensitivity was approximately proportional to the pressure, and sensitivities in the range of 10[minus superscript 12] mole were claimed.  1, record 1, English, - electron%20impact%20detector

Record 1,  Textual support,  French

Record 1,  Textual support,  Spanish