Drift tube borehole muon detector system, apparatus, and method for muon radiography and tomography

A system for estimating subsurface densities, the system comprising:

• one or more muon detectors located in one or more boreholes, each muon detector comprising:
• a tubular housing which defines a bore that is elongated along a longitudinal axis;
• a plurality of elongated drift tubes disposed in the bore of the housing to form a bundle of drift tubes, each drift tube elongated in a direction parallel to the longitudinal axis and the bundle of drift tubes being arranged to be discretely circularly symmetric about the longitudinal axis, each drift tube comprises a centrally located anode wire disposed on a longitudinal axis of the drift tube and a bore-defining cathode surface;
• and
• data-acquisition electronics connected to receive electronic signals from each of the plurality of drift tubes and configured to determine trajectories of muons traversing the muon detector based on the signals received from the drift tubes;
• and,
• a processing unit in communication with each of the one or more muon detectors and configured to generate a three-dimensional density profile of a region of interest based on a plurality of trajectories of muons traversing the one or more muon detectors.