Pressure of Light Used as Restoring Force on an Ultramicrobalance

  • Karl P. Zinnow
  • Jens P. Dybwad
Conference paper


A symmetrical beam torsion ultramicrobalance designed for adsorption, absorption, and sputtering studies is described. The balance, mounted in a bakeable Varian ultrahigh-vacuum chamber with a pressure capability of 10−11 torr, has a sensibility of 10−8 g. The range and the sensitivity of the balance can be selected by external control. Since using magnetic restoring in the vicinity of the Vaclon® pump would require extensive shielding, the pressure of light on a mirror is used to counterbalance mass changes of the sample. A vertically suspended torsion meter is used to measure the light pressure applied. The arrangement of the optical system makes it unnecessary to calibrate the balance system with weights. Mass changes of about 4 · 10−7 g can be counterbalanced with the light source before it is necessary to extend the range by resetting the balance with the external control. The balance is designed to be automated and used as a dynamic nullreading instrument.


Mass Change Radiation Pressure Glass Beam Stray Magnetic Field Suspension Wire 
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  1. 1.
    A. W. Czanderna, Ultramicrobalance review, in: S. P. Wolsky and E. J. Zdanuk (eds.), Ultra Micro Weight Determination in Controlled Environments, Interscience, New York (1969), Chapter 2, p. 7.Google Scholar
  2. 2.
    R. L. Schwoebel, Ultramicrobalance design, ibid., Chapter 3, p. 61.Google Scholar

Copyright information

© Plenum Press, New York 1971

Authors and Affiliations

  • Karl P. Zinnow
    • 1
  • Jens P. Dybwad
    • 1
  1. 1.Space Physics LaboratoryAir Force Cambridge Research LaboratoriesBedfordUSA

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