Annual report - 2007

Scientific purpose of DOBIES

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. Together with the microgravity condition, the cosmic radiation is a very important factor contributing to the different behavior of biological samples in space compared to earth conditions.

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, 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 the Earth. Knowing the LET spectra and the responses of the different types of detectors, the doses can be calculated for different sample 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 conclusion, the DOBIES 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 radiobiological experiments in space.

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

1.            Thermoluminescent detectors with different dependencies of their response on the LET of radiation:

• AlP glass: diameter 8 mm, thickness 1 mm
• Al₂O₃:C: diameter 4.5 mm, thickness 0.85 mm
• CaSO₄:Dy: diameter 4.5 mm, thickness 0.85 mm.

2.             LET spectrometer based on the chemically treated track-etch detectors (TED). Track etch detectors (polyallyldiglycolcarbonate (PADC)) of different origin, individual thicknesses 0.5-0.9 mm, can be dimensioned according to specific needs.

3.             In some cases, also a spectrometer of energy deposited in a Si detectors has been used for some specific studies

All three types of detectors have been used since many years for dosimetry studies onboard spacecraft, aircraft and behind high-energy accelerator shielding.

Czech participants are within the frame of the program DOBIES also participating on the preparation , evaluation, and analysis of both on-Earth tests measurements in high energy accelerator beams and fields as well as onboard spacecraft exposures.

  Description of work performed up to the December 2007

 NPI AS CR team has participated at all activities organized and/or related to the goal of the DOBIES project up to the end of 2007 year:

I.       Ground reference experiments to simulate the radiation in space and characterizing response of TLD's, OSLD's and TED to high LET radiation:

1.      The CERF field (CERN, Switzerland) irradiations, end of 2006, to simulate the neutron spectrum encountered in the space at the level of the ISS.

2.      The JRC-IRMM in Geel, Belgium, November 2006 and 2007. Here mono-energetic neutron beams (E_N ~  0.1 - 20 MeV) were used to characterize our detectors

3.      NPI AS CR team prepared and organized for DOBIES teams irradiations in proton beam (E_P ~ 150 MeV) at Dubna, Russia (September 2007), the detectors have been exposed at the entrance and in Bragg peak region.

4.      Irradiations have also been done at the iThemba laboratory where high-energy neutrons (100 MeV and 200 MeV) have been used to irradiate the DOBIES detectors. 

The analysis of all these experiments has been already started, the results obtained by different DOBIES participants will be compared, and analyzed in the following months, and regularly published in scientific journals and/or presented during scientific meetings.

II.    Onboard spacecraft measurements:

1.      The first space flight in which DOBIES team participated was the BASE-A experiment in September 2006. OSL, TLD, and TED were exposed in space together with the BASE-A biological experiments. The dosemeter results were analysed and compared to previous flights. The differences between the responses of the different detectors are not yet quantitatively explained. A paper on the BASE-A results was prepared and published.

2.      The DOBIES project teams participates on the SI2 space intercomparison. Here, our dosemeters were sent to the ISS in April 2007, together with the dosemeters from other international groups for the period of half a year. The exposure has been finished October 2007, the detectors will be returned to participants January 2008 for the evaluation. NPI AS CR delivered for this exposure 12 sets of TLDs' and LET spectrometers based on TEDs'.

3.      NPI AS CR team has participated during the same space flight also in the frame of SPD experiment in the ISS Russian module. In total 15 sets of TLDs' and LET spectrometers based on TEDs were exposed. They have been already returned to Prague, their evaluation will start in next months.

4.      DOBIES teams will take part in the EXPOSE-EUTEF experiment (18 months exposure, mostly outside of spacecraft). Detectors were already sent to the organizers and approved for the space measurements. The launch (STS 122 Atlantis) planned for December 2007 has been postponed to the 2nd January 2008

5.      Other BASE type experiments are negotiated, as well as some additional exposure onboard Russian ISS module.

6.      Further space intercomparison (SI3) has been already announced, detectors would be exposed in the period April - October 2008. NPI AS CR as well as other DOBIES participants will take part in it.

The evaluation of detectors exposed during some of these flights has been already started, the results obtained by different DOBIES participants will be compared, and analyzed in the following months, and regularly published in scientific journals and/or presented during scientific meetings.

III. General remarks:

The studies proposed to be realised in the frame of DOBIES project are going on within the expected schedule. One of expected flight (Mobilisatsija) could not be realised due to some problems with launch possibilities, other experimental studies both on Earth as in space have been however performed (SI 2, EXPOSE/EUTEF, neutron and proton calibrations, etc), another are in preparation.

IV.  Financial aspects:

The support allocated to NPI AS CR for the participation at DOBIES project is used following the planning, no problems are to be expected from that point of view up to the end of project.

News about Program DOBIES

Experiments realized with the participation of NPI AS CR (thermoluminescent detectors and LET spectrometer based on track etch detectors) and their publication

* BASE A: September 2006, Progress mission to ISS (2+9 days);

* Calibration with monoenergetic neutrons: November 2006, Louvain la Neuve (Belgium), neutron energies from 0.15 to 19 MeV; in evaluation

* Calibration with high-energy neutrons: June 2007, iThemba (Cape Town), neutron energies ~ 100, and 200 MeV;

* EXPOSE/EUTEF experiment: since summer 2007, ~ 1.5 years, outside ISS;

* Simultaneously: since May 2007, Russian module of ISS, 25 sets of NPI dosimeters, also experiment SI-2

Publications in international journals

1. Goosens, O., Vanhavere, F., Leys, N., O’Sullivan, D., Spurny, F., Yukihara, E. and McKeever, S. (2006) Dosimetry for microbial experiment in the Space station using different track-etch and luminescent detectors. Radiat. Prot. Dosim. 120, 433-437

2. Spurný, F., Ploc, O. and Datchev, Ts. To the neutron contribution to the exposure level onboard International Space Station. Radiat. Prot. Dosim., DOI:10.1093/rpd/ncm104

Contributions at International Conferences

1. Jadrníčková, I., Spurný, F. Spectrometry of linear energy transfer onboard of space vehicles with track etch detectors: Results of 2005-2007 studies. COST 724 MCM Meeting, Sofia, May, 21 – 25

2. Spurný F. Jadrníčková, I. Dependence of relative thermoluminescent detectors response on the linear energy transfer. SSD 15, Delft, July 8 -13

3. Jadrníčková, I., Spurný, F. LET spectrometry with track etch detectors – principles and use. SSD 15, Delft, July 8 -13

4. Vanhavere, F., Spurny, F., Jadrníčková, I., etal. Dosimetry of Biological Experiments in Space (DOBIES) with Luminescence (OSL and TL) and Track Etch Detectors SSD 15, Delft, July 8 -13

5. Jadrníčková, I., Spurný, F., Dachev, C., and Ploc O. Upgrading of some instrumentation devoted to increase space radiation environment understanding AOGS 2007, Bangkok 29.7.-3.8.

DOBIES meeting presentations; Reports

1. Jadrníčková, I., Spurný, F.: Dosimetry and microdosimetry onboard International Space Station for Radiobiology; experiment BASE A, program DOBIES. Report DRD NPI AS CR 578/07, Prague January 2007

2. Spurný F. Space radiation dosimetry at DRD NPI AS CR 1980-2006. DOBIES meeting, Mol, March 26-27.03., Belgium

3. Jadrníčková, I., Spurný, F. Dosimetry and microdosimetry onboard International Space Station for Radiobiology; experiment BASE A, program DOBIES. DOBIES meeting, Mol, March 26-27.03., Belgium

4. Spurný, F. Space radiation environment; space radiation dosimetry. Invited talk for CEN Mol management and researchers, DOBIES meeting, Mol, March 26-27.03., Belgium

5. Spurný, F., Jadrníčková, I., Vlcek, B. Turek, K.: Dozimetricheskije kharakteristiky polej izluchenij na borte MKS vo vremja dekabr’ 2005-sentrjabr’ 2006: Eksperiment Matrjoshka; Rezul’taty poluchennyje do konca marta 2007 g. Report DRD NPI AS CR 587/07, Prague, April 2007