LBHNC: A lunar‐based heavy nucleus detector

Abstract

A passive, large‐area experiment for the detection of cosmic ray actinides on the lunar surface is discussed. Due to the absence of a geomagnetic cutoff, a 100 m2 array of nuclear‐track‐detecting glass plates in 5 years will detect ∼300–1000 U and Th cosmic ray nuclei of energies≳0.85 GeV/u (compared to the present world’s total of 4 actinides). With a charge resolution at uranium of ∼0.25 e, the U/Th ratio can be accurately determined, thereby dating the r‐process component of the cosmic rays; the presence of a fresh r‐process component would be corroborated by the likely detection of transuranics as well. In addition, abundances in the Pt/Pb and sub‐Pt/Pb regions and abundances of secondary actinides would provide detailed data on the 0‐1 g/cm2 region of the cosmic ray path length distribution, hence on the astrophysical site of origin of these cosmic rays. Finally, should a fresh r‐process component exist, the detection of postulated superheavy nuclei is conceivale. With an analysis station at the Lunar Base, glass plates could periodically be harvested, analyzed, annealed/remelted, and replaced onto the lunar surface.