Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published March 25, 2019 | Submitted
Report Open

Directed Electron Velocity Distributions in Rare Gas Discharges Using Guard Ring Probes


An experimental technique for determining detailed properties of anisotropic electron velocity distributions is described. For a planar Langmuir probe it is shown that g(v_z) = -[(m^(∂)J_(p))/(e^(2∂)V_(p))] where v_z = √[2(e/m)V_p] and g(v_z) gives the density of electrons with velocities normal to the probe in the range v_z to v_z + dv_z. This expression is valid for any distribution function making it possible to study anisotropies merely by changing the orientation of the probe. If the distribution function is isotropic the above expression is valid for cylindrical and small spherical probes as well. This technique is applied to the measurement of the directional properties of electron velocity distributions in the positive column of neon and helium hot cathode discharges. The necessary planar probe consists of a 0.01 inch diameter circular probe surrounded by a 0.090 inch square guard-ring. The measured distributions were Druyvesteyn in form except that all electrons were shifted in energy (in the direction of the external field) by an amount proportional to Eλ(v_z). Here E is the magnitude of the external electric field and λ(v_z) the electron mean free path as a function of v_z. The experimental conditions are shown to be identical with those necessary in the derivation of the Druyvesteyn distribution.

Additional Information

The author is deeply indebted to many people for their direct contributions to this project. In its initial stages the work was supported by the National Bureau of Standards, Boulder, Colorado. Particular thanks go to Frank Haller and John Trickey of that laboratory for their work in constructing the necessary equipment. During the major portion of this work the interest and suggestions of Professors R. V. Langmuir and R. W. Gould proved invaluable. My hat is off to Howard Friedrich whose skill made it possible to construct the probe described here. Also, many thanks are due Fred Wild for his expert glass work. The major portion of this work was supported by the Office of Naval Research Contract Nonr 220(50). I.B.M. and the Hughes Aircraft Company have been most generous in their fellowship support of the author. A special word of appreciation is due Mrs. Ruth Stratton for her skillful work in preparing the manuscript.

Attached Files

Submitted - TR000365.pdf


Files (4.6 MB)
Name Size Download all
4.6 MB Preview Download

Additional details

August 19, 2023
January 14, 2024