Diffusion Of Electrons In Gases Research Articles

Development of a Device to Measure the Electron Transverse Diffusion in Gas Media

In this work, a new device developed to measure the transverse diffusion of electrons in gases is described. In this device, electrons are generated in a semitransparent cesium iodide (CsI) photocathode, exposed to xenon VUV light from a pulsed Xe lamp. Electrons are allowed to drift a fixed distance, which can be varied between 3.5 and 60 mm, and the charge is collected in a multistrip anode electrode. In the present work, we report the results obtained in xenon and in methane under reduced electric fields of 0.92 and 1.53 Td, for drift distances between 3.5 and 11.5 mm. The electron characteristic energy associated with the transverse diffusion, as measured with this new device, is 5.75 ± 0.45 eV and 7.15 ± 0.63 eV at 0.92 and 1.53 Td, respectively, for xenon and 0.065 ± 0.005 eV and 0.097 ± 0.008 eV at 0.92 and 1.53 Td, respectively, for methane, which are in good agreement with results from the literature.

A new experimental system for electron transverse diffusion measurements

The knowledge of the electron transverse diffusion in detection media is mandatory to assess the accuracy in systems that require precise event tracking. A new experimental system was developed to measure the transverse diffusion of electrons in gases. Electrons are generated in a transmissive CsI photocathode by Xe VUV light from a pulsed Xe lamp, and drift a fixed distance that can be varied from 4 to 60 mm. The charge is then multiplied in a GEM and collected in a multistrip target. The results were obtained for Xe and CH4 at two different E/N values, at 800 Torr, for drift distances between 4 and 12 mm. The characteristic energy associated with the transverse diffusion obtained were (5.75±0.45) eV and (7.15±0.63) eV for Xe, and (0.065±0.005) eV and (0.097±0.008) eV for CH4, respectively for 0.92 and 1.53 Td. All values are in good agreement with results from the literature.

Longitudinal diffusion of electrons in weakly ionized gas with Coulomb collisions

Equations describing the longitudinal electron diffusion in gases with Coulomb collisions in an electric field are derived. It is shown that the presence of electron-electron interactions leads to the renormalization of the longitudinal diffusion coefficient which is calculated in Ar, He, and N2. The numerical results are used in the investigation of the thermocurrent instability threshold in the glow discharge in He. The thermocurrent instability is retarded at high ionization levels.

Experiments on the photoelectric effect and on the diffusion of electrons in gases

A versatile appartus for observing the behavior of photoelectrons in a uniform magnetic field in either a vacuum or a low-pressure gas is described. The apparatus was designed and constructed as a senior research project and is now used in a graduate laboratory course. Data on work functions and the photoelectron energy and angular distributions are presented and a common misinterpretation of photoelectric work functions is discussed. Data on the diffusion of free electrons in low-pressure air are compared to a series solution of the steady-state diffusion equation to determine the electron-molecular total cross section. The interpretation of cross sections from diffusion experiments is discussed.