Measuring radiation doses in space with a combination of passive detectors (PhD)

The effects of the complex radiation field in space, consisting of neutrons, electrons and high-energy heavy charged particles, on biological samples are of high interest in the fields of radiobiology and exobiology. Radiation doses absorbed by biological samples must be quantified to be able to determine the relationship between observed biological effects and the radiation dose. For radiation protection purposes the effective doses to astronauts needs to be assessed, while in dosimetry for biological experiments the absorbed dose and the equivalent doses to the samples need to be known. Special techniques and correction methods combining luminescence detectors and track etched detectors are required due to the presence of particles with a wide range of LET (Linear Energy Transfer) values. These doses can be different from flight to flight, due to different solar activity, different position in the spacecraft, different compositions of the samples, and different shielding due to packaging materials.

The objective of this proposal is to develop a standard dosimetric method (as a combination of different techniques) to measure accurately the absorbed doses of space radiation. A measurement and calculation procedure for such measurements will be developed and a standard measurement kit will be made for different biological and microbiological samples (in vitro cells, tissue, bone,...), different packaging materials and different positions in a spacecraft. A special case would be the dosimetry of samples that are located in external modules, like the EXPOSE hardware.

This objective can be achieved by studies of the LET dependencies of the different types of detectors. This requires irradiations in standard high energy particle fields on earth. By measuring the LET spectra during some space flights, the influence of different locations and packaging materials can be assessed. Knowing the LET spectra and the responses of the different types of detectors, the doses can be calculated for different samples materials and geometries. The results of the real dosimetric experiments during different flights will lead to an optimization of the methodology and calculations tested.

In summary, the experiments will study the responses of different detector types in real and simulated space radiation fields. This will lead to a unique recommendation and description on dosimetric systems for experiments in space. The outcome of this project can be used in future space flights by different groups. New developments in read-out techniques and detector materials, will require a re-evaluation of the dosimetry kit procedures at periodic times. Also new irradiation facilities can enhance the knowledge of the detector characteristics, which might be included in the dosimetric procedures.