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Neutron Spectrometer for Spacecraft

#3779


Development of a Portable High-Energy Neutron Spectrometer for Active Diagnostics of Radiation Environment in Spacecraft

Tech Area / Field

  • SAT-SAF/Space Safety/Space, Aircraft and Surface Transportation
  • INS-MEA/Measuring Instruments/Instrumentation

Status
8 Project completed

Registration date
18.06.2007

Completion date
28.04.2012

Senior Project Manager
Ryzhova T B

Leading Institute
Khlopin Radium Institute, Russia, St Petersburg

Collaborators

  • Canadian Space Agency / Operational Space Medicine Group, Canada, QC, Saint-Hubert\nDeutsches Zentrum für Luft- und Raumfahrt e.V. / Institut für Luft- und Raumfahrtmedizin, Germany, Köln\nUniversity of Uppsala / Svedberg Laboratory, Sweden, Uppsala\nUniversity of Uppsala / Department of Neutron Research, Sweden, Uppsala\nBubble Technology Industries Inc., Canada, ON, Chalk River\nRoyal Military College of Canada, Canada, ON, Kingston

Project summary

Dosimetry measurements made aboard low-earth orbit (LEO) spacecrafts over the past 20 years revealed that neutrons could contribute significantly to astronaut radiation exposure. The neutron component is estimated to account for approximately 30% of the total dose equivalent in LEO spacecraft (and more than 50% - in space missions beyond the Earth’s magnetosphere). The real numbers depend strongly on the solar cycle, spacecraft’s shielding, orbital inclination, altitude, and, in fact, are not well understood. A large uncertainty in the neutron dose determination is due to a poor characterization of neutron fields inside a spacecraft. These fields are largely formed by secondary neutrons produced by high-energy charged particles of galactic and solar origin in their collisions with spacecraft structures. The neutron spectrum inside LEO spacecraft extends from thermal to the GeV energies, but for the accurate risk assessment of possible radiation effects on crewmembers, the neutron measurements over the energy range 0.2 eV – 200 MeV are necessary. Currently available instrumentation can provide reasonably good measurements of the neutron flux at energies below about 14 MeV, whereas the measurements at higher neutron energies remain a difficult problem. The present Project is aimed at the development of a portable, high-energy neutron spectrometer (PHENS) for real-time measurements aboard spacecraft.

A prototype of PHENS will be developed in the course of the Project. The main technical characteristics of PHENS are listed below:


Mass ≤ 2 kg
Energy consumption ≤ 3 W
Overall dimensions 10x15x15 cm3
Sensitivity:
10-50 MeV 0.2 cm2
50-200 MeV 0.1 cm2

Detecting element of PHENS (with a volume of 2-3 cubic centimeters) is made of a lightweight material. The detector measures energy deposition spectrum of secondary charged particles due to nuclear interactions between energetic neutrons and the nuclei contended in the detecting element. Having this spectrum, one can evaluate (using unfolding procedures) the incident neutron energy spectrum, provided that the detector response functions are well known for a wide set of neutron energies. The detector assembly is shielded by anti-coincidence system (inorganic scintillators with photodiode readouts) to separate neutrons from primary and secondary charged particles. Associated electronics comprises power-supply converters, signal-processing modules, programmable controller with memory, and interface units.

PHENS should meet the special technical demands, which are normally placed upon radiation detecting instruments in space. Institute of Biomedical Problems (IBMP) Russian Academy of Sciences, that is responsible for the crew radiation safety aboard the Russian Segment of the International Space Station (ISS), will draw up the corresponding requirements specification. The demands will be imposed on the detector portability, construction, power supply, safety, resistance to external action, etc. All the stages of the PHENS testing and engineering development will be performed at IBMP attached Special Design Bureau of Experimental Equipment.

An important point in the PHENS development is reliable determination of its response matrix at incident neutron energies up to 200 MeV. It is expected to be done at quasi-monoenergetic neutron beams available at the Université Catholique de Louvain (UCL) in Louvain-la-Neuve, Belgium, the The Svedberg Laboratory (TSL) in Uppsala, Sweden, and the iThemba Laboratory for Accelerator Based Sciences in Cape Town, South Africa. The measurements will be carried out using various neutron fluence monitors developed by the KRI group for the basic nuclear data measurements at European neutron beam facilities (UCL, TSL). The choice between the neutron beam facilities to be used for the PHENS calibration will be done in such a way to optimize the quality-to-cost ratio of the data.

The major part of the proposed work will be performed in Russia, including designing, manufacturing and testing of PHENS and supporting equipment. The Project meets ISTC goals completely as it provides weapons scientists and engineers, who possess knowledge and skills related to weapons of mass destruction, opportunities to redirect their talents to peaceful activities in the sphere of space exploration.

The PHENS is targeted for operation aboard the ISS and the research satellite “BION”. At the same time, the PHENS application can be extended to airborne dosimetry, accelerator-based medicine and research, accelerator-driven systems for transmutation of nuclear waste, etc.


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