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Preliminary Study for the Construction of a Direct-reading Dosimeter for Astronauts

In 2007, the European Space Agency (ESA) started developing a direct-reading dosimeter for astronauts. A consortium – consisting of the Physikalisch-Technische Bundesanstalt (PTB)/Germany, Mirion Technologies (RADOS) Oy/Finland, the Austrian Institute of Technology (AIT)/Austria, and Tyndall National Institute/Ireland - under the leadership of the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt - DLR), was commissioned with a preliminary study (contract No. 20795/07/NL/CP).

The figure shows the conceptual principle of the suggested system. It consists of a service unit - in which the personal dosimeters are charged and information is saved - and a TEPC (Tissue Equivalent Proportional Counter) - which, in the right figure, is represented as a sphere and, via the display of an LET (Linear Energy Transfer) spectrum, serves as a reference measuring instrument for radiation quality in space.

It has been recommended to set up direct-reading personal dosimeters using four components:

  • a silicon semi-conducting detector of approx. 300 µm thickness equipped with pulse-height spectroscopy enabling the display of the LET spectrum for low ionizing radiation;
  • another silicon detector with a thinner sensitive layer (approx. 5.6 µm, as in PTB’s prototype neutron dosimeter DOS-2005) which enables the indication of an LET spectrum for high ionizing radiation;
  • a small ionization chamber (Direct Ion Storage Chamber – DIS – developed by the RADOS company) which does not allow LET measurement but reliably integrates the absorbed dose – even at high dose rates;
  • a RadFET (Radiation Sensing Field Effect Transistor, developed by Tyndall National Institute) which reliably indicates the absorbed dose at even higher dose rates, e.g. in the case of a solar event.

The selection of the components is based on the results of computer simulations which predict the indication of the dosimeter probes in space where the ISS (International Space Station) is located. The results of these calculations were presented on the occasion of a congress (11th Neutron and Ion Dosimetry Symposium, Cape Town, South Africa, 12-16 October 2009) and a publication is presently being printed [1]. http://dx.doi.org/10.1016/j.radmeas.2010.08.026.


Figure:

Conceptual design of a dosimeter system for use inside the ISS

Literature

  1. Luszik-Bhadra, M., Beck, P., Berger, T., Jaksic, A., Latocha, M., Rollet, S., Vuotila, M., Zechner, A. and Reitz, G.: Response calculations for silicon-based direct reading dosimeters for use at the international space station (ISS), doi:10.1016/j.radmeas.2010.08.026

Contact person:
M. Luszik-Bhadra, Department 6.5, Working Group 6.52,
e-mail: Marlies Luszik-Bhadra


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