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Wall effects observed in tissue-equivalent proportional counters from 1.05 GeV/nucleon iron-56 particles
S E Rademacher1, T B Borak, C Zeitlin
1Department of Radiological Health Sciences, Colorado State University, Fort Collins 80523, USA.
Radiation Research
|April 3, 1998
Summary
Tissue-equivalent proportional counters (TEPCs) can measure energy deposition but wall effects are significant for heavy ions. These wall effects influence energy transfer measurements, especially near the cavity/wall interface.
Area of Science:
- Radiation dosimetry
- Biophysical modeling
Background:
- Tissue-equivalent proportional counters (TEPCs) are used to simulate energy deposition in microscopic tissue volumes.
- Concerns exist regarding the influence of TEPC wall density on energy deposition within the sensitive volume, particularly for high-velocity heavy ions.
Purpose of the Study:
- To investigate the impact of TEPC wall effects on energy deposition measurements for high-velocity heavy ions.
- To quantify energy loss and transfer within a 1-micrometer tissue-equivalent volume under specific irradiation conditions.
Main Methods:
- Measurements of energy deposition using a TEPC simulating a 1-micrometer tissue sphere.
- Irradiation with 1 GeV/nucleon iron particles within a particle spectrometer for individual particle identification and trajectory analysis.
- Study of energy deposition as a function of particle pathlength through the TEPC.
Main Results:
- Approximately 30% of energy transfer escaped the sensitive volume for trajectories through the detector's center.
- TEPC response consistently exceeded homogeneous medium calculations for energy loss.
- Enhanced response was most pronounced for trajectories near the cavity/wall interface.
Conclusions:
- TEPC wall effects significantly influence energy deposition measurements, particularly for high-velocity heavy ions.
- Charged-particle equilibrium is achieved with a 2.54 mm wall thickness.
- Accurate estimation of linear energy transfer requires accounting for these wall effects in TEPC measurements.
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