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Secondary particle contribution to LET spectra on LDEF
E R Benton1, E V Benton, A L Frank
1Eril Research Inc., San Rafael, CA 94915-0788, USA.
Radiation Measurements
|November 1, 1996
Summary
High-energy radiation in space, particularly from trapped protons in the South Atlantic Anomaly, creates secondary particles. These particles significantly contribute to the radiation dose equivalent, necessitating improved space radiation transport models.
Area of Science:
- Space radiation physics
- Radiation detection and dosimetry
- High-energy particle physics
Background:
- Passive detectors were used on the Long Duration Exposure Facility (LDEF) to study the space radiation environment.
- Understanding the radiation environment is crucial for astronaut safety and spacecraft design.
- Previous studies focused on general radiation measurements, but detailed analysis of secondary particle contributions was needed.
Purpose of the Study:
- To measure Linear Energy Transfer (LET) spectra at various locations and shielding depths using plastic nuclear track detectors (PNTDs).
- To identify the sources of high-LET particles and their contribution to dose equivalent.
- To compare experimental measurements with accelerated proton beam exposures and radiation transport models.
Main Methods:
- Utilized passive detectors (P0006, P0004, A0015, M0004) on LDEF to record charged particle tracks.
- Analyzed LET spectra, extending detection capabilities to include short-range secondary particles.
- Conducted intercomparisons between LDEF measurements and controlled exposures to 154 MeV proton beams.
Main Results:
- LET spectra extended significantly beyond the geomagnetic cutoff for Galactic Cosmic Rays (GCRs), indicating the presence of locally produced secondaries.
- Short-range secondary particles from trapped protons in the South Atlantic Anomaly (SAA) were identified as a major contributor to high-LET spectra.
- GCRs contributed modestly compared to secondary particles and stopping protons; experimental data showed similarities with proton beam interactions, supporting the secondary particle hypothesis.
Conclusions:
- Secondary particles, particularly those generated by trapped protons in the SAA, are a significant factor in the space radiation dose equivalent.
- The high-LET tail of the spectra, extending beyond 1000 keV/micrometer, is primarily due to these locally produced secondaries.
- Accurate modeling of secondary particle production is essential for improving radiation transport codes and realistic dose equivalent assessments in space.