Production of square temperature waves in filaments of field emission microscopes operating at low temperatures

  • R. Klein


An important consideration in the measurement of activation energies of surface processes observed with the field emission microscope is the production of a square temperature wave. That is, the initial temperature rise to the final operating temperature must be sufficiently rapid so that uncertainties in time measurements can be eliminated. The temperature-current characteristics of a typical field emission microscope tungsten filament operating in a low temperature bath such as liquid nitrogen or liquid helium are derived from the well known solution of the heat conduction equation. The steady state current-temperature curves are of the form i = F + (B/ T) where B is negative for filament end temperatures above 50° K, zero at this temperature, and negative below. The steady state temperature-current curve for the filament of a tube operating at liquid helium temperature represents an unstable equilibrium. These predictions were confirmed experimentally with a 0.1 mm diameter, 2.5 cm long filament. A circuit capable of producing a filament temperature above 4.2° K to any desired temperature below 600° K in less than 0.3 sec will be described.

Copyright information

© Springer-Verlag Berlin Heidelberg 1960

Authors and Affiliations

  • R. Klein
    • 1
  1. 1.National Bureau of StandardsWashingtonUSA

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