Accession Number:

ADA010220

Title:

Microdosimetric Structure of HZE Particle Tracks in Tissue,

Descriptive Note:

Corporate Author:

NAVAL AEROSPACE MEDICAL RESEARCH LAB PENSACOLA FL

Personal Author(s):

Report Date:

1975-04-08

Pagination or Media Count:

24.0

Abstract:

Heavy nuclei of the primary galactic radiation in space HZE particles can have the same Linear Energy Transfer LET yet greatly different lateral distribution patterns of the energy in the microstructure of tissue. Track structure thus presents itself as a new dosimetric parameter for HZE particles which is at present incompletely understood in its radiobiological significance. While the microscopic image of a particle track in nuclear emulsion conveys some information on track structure, a complete analysis has to rely on theory. The theory of track structure distinguishes two regions core and penumbra. The core is a narrow region with a radius far below 1 micron in tissue where energy deposition occurs mainly through excitations and collective oscillations of electrons. Energy density in the core is enormous accounting for slightly more than half the total LET. The penumbra surrounding the core extends laterally several to many microns depending on the energy of the primary. Energy density in the penumbra decreases steeply with the square of increasing radius. The relationships are illustrated with nuclear emulsion micrographs and plots of energy density profiles. The implications of the findings for a dosimetric system for HZE particles are discussed.

Subject Categories:

  • Astrophysics
  • Radiobiology
  • Astronautics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE