Advertisement

An Attempt to Modify the MOCA Water-Vapor-Ion Code to Simulate Liquid Phase

  • S. B. Curtis
  • J. B. Schmidt
  • W. E. Wilson
Part of the Basic Life Sciences book series (BLSC, volume 63)

Abstract

An attempt was made to apply to liquid water the Monte Carlo code, MOCA14, which calculates track-structure (i.e., three-dimensional distribution of ionizations) for heavy charged-particle tracks in water-vapor. The criterion used was that the stopping powers for four energies of protons (1, 2, 5 and 10 MeV) should correspond to the stopping powers in liquid water found in ICRU Report #49. To adjust phenomenologically the vapor source data, two modifications were made: (1) several vapor-phase excitation interactions were assumed to result instead in ionizations in liquid; and (2) the optical oscillator strength along the energy-loss scale was shifted by adding (or subtracting) a constant while simultaneously and independently subtracting a constant energy from the inelastic ionization energy thresholds. The total energy-loss was used to overcome the binding energy (which was decreased by an arbitrary amount) and to provide energy to the ejected secondary electron. To be consistent, a similar adjustment was made to the secondary electron energy-loss processes. It was found that no adjustment of the two constants brought the values of the average stopping powers into agreement with the ICRU stopping power values. It is concluded that no simple and physically meaningful manipulation of the water vapor code for protons in the energy range between 1 and 10 MeV could bring the stopping powers into agreement with currently accepted values.

Keywords

Liquid Water Oscillator Strength Monte Carlo Code Track Structure Total Energy Loss 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. Berkowitz, J. (1979), Photoabsorption, Photoionization, and Photoelectron Spectroscopy, Academic Press, New York, ISBN 0-12-091650-9.Google Scholar
  2. Heller Jr., J.M., Hamm, R.D., Birkhoff, R.D., Painter, L.R., (1974), J. Chem. Phys. 60, 3483–3486.Google Scholar
  3. ICRU (1984), Stopping Powers for Electrons and Positrons, ICRU Report 37 ( International Commission on Radiation Units and Measurements, Bethesda, Maryland ).Google Scholar
  4. ICRU (1993), Stopping Powers for Protons and Alpha Particles, ICRU Report 49 ( International Commission on Radiation Units and Measurements, Bethesda, Maryland ).Google Scholar
  5. LaVerne, J.A., Mozumder, A. (1986), Effect of phase on the stopping and range distribution of low-energy electrons in water, J. Phys. Chem. 90, 3242–3247.Google Scholar
  6. Paretzke, H.G. (1987), Radiation track structure theory, in: “Kinetics of Nonhomogeneous Processes,” G.R. Freeman, ed., John Wiley & Sons, New York, ISBN 0-471-81324-9.Google Scholar
  7. Paretzke, H.G., Turner, J.E., Hamm, R.N., Ritchie, R.H., and Wright, H.A. (1991), Comparative study of electron energy deposition and yields in water in the liquid and vapor phases, Radiat. Res. 127, 121–129.Google Scholar
  8. Turner, J.E., Paretzke, H.G., Hamm, R.N., Wright, H.A., and Ritchie, R.H. (1982), Radiat. Res. 92, 47–60.CrossRefGoogle Scholar
  9. Zeiss, G.D., Meath, W.J., MacDonald, J.C.F., and Dawson, D.J. (1975), Radiat. Res. 63, 64–82.PubMedCrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media New York 1994

Authors and Affiliations

  • S. B. Curtis
    • 1
  • J. B. Schmidt
    • 2
  • W. E. Wilson
    • 3
  1. 1.Fred Hutchinson Cancer Research CenterSeattleUSA
  2. 2.Lawrence Berkeley LaboratoryUniversity of CaliforniaBerkeleyUSA
  3. 3.Pacific Northwest LaboratoriesRichlandUSA

Personalised recommendations