Ruprecht Karls Universität Heidelberg


The Ultra Rapid Adaptable Neutron-Only Simulation for Environmental Research

M. Köhli1,3, M. Schrön2, S. Zacharias2, P. Dietrich2 and U. Schmidt1

1 Physikalisches Institut, Heidelberg University
2 Department of Monitoring and Exploration Technologies, UFZ Leipzig
3 Physikalisches Institut, University of Bonn


M. Köhli, M. Schrön


The Monte Carlo code URANOS was specifically tailored to address the open questions of cosmic-ray neutron sensing for environmental applications (Köhli et al. 2015). As the model has been developed further, it also proofed to be useful for neutron spin echo detectors in other research fields (Köhli et al. 2016). The model is able to predict the response of cosmic-ray neutrons to user-defined and spatially variable conditions in the soil, atmosphere, and biosphere. URANOS is very efficient, as it only accounts for the most relevant neutron interaction processes, namely elastic collisions, inelastic collisions, absorption, and evaporation.
The main model features are:
  • voxel engine,
  • tracking of particle histories from creation to detection (ray-casting),
  • detector representation as layers or cylinders,
  • automatic model and material setup based on color codes in 2D bitmap images


URANOS was developed for the project "Neutron Detectors for the MIEZE method" funded by the German Federal Ministry of Education and Research (BMBF), grant identifier: 05K10VHA. Source code and support for URANOS can be provided by M. Köhli. The research was funded and supported by Terrestrial Environmental Observatories (TERENO), which is a joint collaboration program involving several Helmholtz Research Centers in Germany.


URANOS Main Program

URANOS Additional Dependencies



UFZ Leipzig Website

Additional information, publications and mailing lists:
  • Cosmic-Sense Project

  • Project Web Page
  • Uni Heidelberg Page
  • Support

    For technical support, questions or adaptation of the source code for your own project, please contact

    Reference publication lists

    • Köhli, M., et al., 2021, "Soil Moisture and Air Humidity dependence of the above-ground cosmic-ray neutron intensity", Frontiers in Water, 2, 1-15, doi:10.3389/frwa.2020.544847
    • Badiee, A., et al., 2021, "Using Additional Moderator to Control the Footprint of a COSMOS Rover for Soil Moisture Measurement", Water Resources Research, 57, e2020WR028478, doi:10.1029/2020WR028478
    • Weimar, J., et al., 2020, "Large-scale boron-lined neutron detection systems as a 3He alternative for Cosmic Ray Neutron Sensing", Frontiers in Water, 2, 1-16, doi:10.3389/frwa.2020.00016
    • Schattan, P., et al., 2019, "Sensing area-average snow water equivalent with cosmic-ray neutrons: the influence of fractional snow cover", Water Resources Research, 55, 10796-10812, doi:10.1029/2019WR025647
    • Li, D., et al., 2019, "Can Drip Irrigation be Scheduled with Cosmic-Ray Neutron Sensing?", Vadose Zone J., 18:190053, doi:10.2136/vzj2019.05.0053
    • Köhli, M., et al., 2018, "Response Functions for Detectors in Cosmic Ray Neutron Sensing", Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 902, 184-189, doi:10.1016/j.nima.2018.06.052
    • Schrön, M., et al., 2018, "The Cosmic-Ray Neutron Rover - Mobile Surveys of Field Soil Moisture and the Influence of Roads", Water Resources Research, doi: 10.1029/2017WR021719
    • Schrön, M., et al., 2018, "Intercomparison of cosmic-ray neutron sensors and water balance monitoring in an urban environment", Geoscientific Instrumentation, Methods and Data Systems, 7, 83-99, doi:10.5194/gi-7-83-2018
    • Schrön, M., et al., 2017, "Improving calibration and validation of cosmic-ray neutron sensors in the light of spatial sensitivity", Hydrology and Earth System Sciences, 21, 5009-5030, doi:10.5194/hess-21-5009-2017
    • Köhli, M., et al., 2017, "Novel Neutron Detectors based on the Time Projection Method", Physica B: Condensed Matter - ICNS Proceedings, doi:10.1016/j.physb.2018.03.026
    • Köhli, M., et al., 2016, "Efficiency and spatial resolution of the CASCADE thermal neutron detector", Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 828, 242-249, doi:10.1016/j.nima.2016.05.014
    • Schrön, M., et al., 2015, "Monitoring Environmental Water with Ground Albedo Neutrons and Correction for Incoming Cosmic Rays with Neutron Monitor Data". In: 34th International Cosmic-Ray Conference (ICRC 2015). Proceedings of Science.
    • Köhli, M., Schrön, M. et al., 2015, "Footprint characteristics revised for field-scale soil moisture monitoring with cosmic-ray neutrons", Water Resources Research, 51, 5772-5790, doi:10.1002/2015WR017169


    Special Versions

    EDV Abteilung