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Neutron detector for space applications

Highly miniaturized and sensitive thermal neutron detector for space applications

Thermal neutron detector

Project duration: 2010 to 2011

Project manager: Zdeněk Vykydal

Devices from the Medipix family prove to be an excellent tool for measurement and characterization of complex radiation fields including thermal and fast neutrons. The use of a neutron detector in planetary remote sensing is an important tool in the search for hydrogenous materials and specifically the presence of water which is the essential ingredient in the search for extraterrestrial life. In addition, high sensitivity neutron measurements used in combination with X-ray and gamma-ray measurements, improves the analysis of the atomic composition of regolith, which in turn, is used to interpret surface geology and ultimately planetary evolution.

High spatial resolution (matrix of 256 x 256 pixels of 55 µm x 55 m pitch) and sensitivity of the Medipix detector allows visualizing directly the energy loss and charge collection processes in the sensor material (300 µm thick silicon in this case). The different radiation types have different characteristic shapes and it is possible to use this information for very effective background suppression. Since silicon itself is insensitive to thermal neutrons a 6Li in the form of 6LiF powder was used to convert thermal neutrons into charged particles via the reaction 6Li + n -> α + 3H. Detection efficiency for thermal neutrons is above 1%.

In order to meet ESA standards for spacecraft equipment a compact, low power and lightweight FPGA based readout system communicating via SpaceWire interface was developed. Dimensions of the whole device including Medipix chipboard are 160 x 75 x 15 mm with total weight is 70 g. Power consumption of the device is 1.4 W during measurement and 0.75 W when the detector is in standby. Readout speed is 7 fps with single Medipix device which is sufficient for the target application.

Furthermore, the whole detection system is mass and power efficient in comparison with the gas proportional detectors which are standardly used in space applications for thermal neutron detection.

The project was carried out with ESA grant support No. 22907/09/NL/CBi.

The Institute of Experimental and Applied Physics

IEAP is the research center of the Czech Technical University in Prague (CTU) for applied and fundamental research in experimental physics of the microworld. R&D focuses on advanced instrumentation and new methods with novel applications in biomedical imaging and space. The IEAP CTU has presently over 80 staff members with one fifth of foreigners and many Ph.D. students and young researchers. The institute is equipped with modern facilities such as high-resolution micro-tomography units and widerange gamma-ray source facilities designed and constructed by IEAP teams. The latter facilities serve for calibration of spacecraft instruments including a transportable station for remote onsite measurements at ESA Test Centers. The institute operates also a Van de Graaff accelerator which provides light ion and mono-energetic fast neutron sources for space-related research.

What would you name as main benefits of the project to you and your company?

“The project of Highly Miniaturized and Sensitive Thermal Neutron Detector for Space Applications” falls in the long-term research strategy of the IEAP CTU in development of the complex radiation field characterization methodology (including fast and thermal neutrons) and appropriate instrumentation. IEAP CTU has already long-term experience in this field which has been demonstrated by the ATLAS-MPX detector network built and operated inside the ATLAS experiment at CERN. Collaboration with ESA opens up the possibility of practical application of this research in space.”