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Wall effects observed in tissue-equivalent proportional counters from 1.05 GeV/nucleon iron-56 particlesTissue-equivalent proportional counters (TEPCs) have been used to measure energy deposition in simulated volumes of tissue ranging in diameter from 0.1 to 10 microm. There has been some concern that the wall used to define the volume of interest could influence energy deposition within the sensitive volume because it has a density significantly greater than that of the cavity gas. These effects become important for high-velocity heavy ions. Measurements of energy deposition were made for 1 GeV/nucleon iron particles in a TEPC simulating a 1-microm-diameter sphere of tissue. The TEPC was nested within a particle spectrometer that provided identification and flight path of individual particles. Energy deposition was studied as a function of pathlength through the TEPC. Approximately 30% of the energy transfer along trajectories through the center of the detector escapes the sensitive volume. The response of the TEPC, for trajectories through the detector, is always larger than calculations for energy loss in a homogeneous medium. This enhancement is greatest for trajectories near the cavity/wall interface. An integration of the response indicates that charged-particle equilibrium is essentially achieved for a wall thickness of 2.54 mm. However, estimates of the linear energy transfer for the incident particles are influenced by these wall effects.
Document ID
20040172740
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Rademacher, S. E.
(Colorado State University Fort Collins 80523, United States)
Borak, T. B.
Zeitlin, C.
Heilbronn, L.
Miller, J.
Chatterjee, A.
Date Acquired
August 22, 2013
Publication Date
April 1, 1998
Publication Information
Publication: Radiation research
Volume: 149
Issue: 4
ISSN: 0033-7587
Subject Category
Life Sciences (General)
Distribution Limits
Public
Copyright
Other
Keywords
Non-NASA Center
NASA Discipline Radiation Health

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