DOBIES

The effects of the complex radiation field in space, consisting of high-energy heavy charged particles, neutrons, and electrons, on biological samples are of high interest in the fields of radiobiology and exobiology. Radiation energy absorbed by biological samples must be characterised not only quantitatively but also qualitatively, through, for example the linear energy transfer (LET) and its distribution. Only in such case one can be able to determine the relationship between observed biological effects and the radiation energy deposited. 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 values. These doses can be different due to different position in the spacecraft, different compositions of the samples, and different shielding due to packing materials.

The objective of this project is to develop a standard dosimetric method (as a combination of different techniques) to measure accurately the absorbed doses and equivalent doses in biological samples. A measurement and calculational procedure and for such measurements will be developed and a standard measurement kit will be made. This for different biological and microbiological samples (in vitro cells, tissue, bone,...), different packing 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 packing 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.

In conclusion, the DOBIES experiments will study the responses of different detector types in real and simulated space radiation fields. This will lead to an unique recommendation and description on dosimetric systems for radiobiologocal experiments in space.

Czech participants are using within the frame of the program DOBIES following detectors:

·        Thermoluminescent detectors with different dependencies of their response on the LET of radiation, and

·        LET spectrometer based on the chemically treated track-etch detectors. This method has been developed in the Institute and is regularly upgraded since more than 20 years.

Both types of detectors have been used since many years for dosimetry studies onboard spacecraft, aircraft and behind high-energy accelerator shielding. Other partners on the DOBIES project are:

·        SCK/CEN, B-2400, Mol, Belgium (coordinator)

·        Dublin Institute of Advanced Studies, Ireland, and

·        Oklahoma State University, USA.