Speaker
Description
Although water presence in lunar polar regions has been confirmed by orbiters, it remains unclear how accessible these resources are for extraction and use. Sustainability of a potential astronaut base on the Moon would be enhanced if water from local environment could be used. An in-situ exploration by a rover capable of drilling is essential for a better understanding of water abundance in the top few meters of lunar soil and rocks. However, since drilling is time- and power-intensive, it would be advantageous to develop a method to identify the promising sites for drilling with presumed high concentration of water.
Interactions of cosmic rays in the top few meters of lunar soil generate secondary particles, including neutrons. Hydrogen in water molecules has a significant cross section for collisions with neutrons, thereby altering the spectrum of neutrons observed above lunar soil. A neutron detector based on Timepix3 with silicon sensor is proposed to detect these changes in neutron field and identify potential drilling sites. Timepix3 would employ HardPix readout which was developed for space applications and has already been used in space.
The detector incorporates LiF converters enriched in Li-6 isotope, known for its high cross-section with slow neutrons through the Li-6(n, H-3)He-4 reaction. The converter is positioned directly above the silicon sensor, allowing Timepix3 to detect the resulting tritium and helium nuclei. The particle identification capabilities of Timepix3 enable it to filter out background events effectively and to identify tritium and helium nuclei with high sensitivity. Part of the LiF region is covered by additional Cd metal sheet to block neutrons with energies smaller than ~0.5 eV. Another part of the sensor will be covered by polyethylene converter sensitive to fast neutron and part of the sensor area is without any converters and Cd shielding for background subtraction. By comparing particle counts in the LiF, LiF+Cd and polyethylene regions of the sensors, it will be possible to find lunar sites with altered neutron spectrum that might contain higher densities of water.
Multiple Timepix3 detectors will be used to increase the sensitive area and shorten the acquisition time. The design of the detector and the analysis method will be presented, as well as results from laboratory measurements in known neutron fields and simulation validations. We will show results of simulations predicting the time on lunar surface needed to distinguish varying levels of water in the soil and the power consumption as a function of number of detectors.
