The LDM-1 incorporates an ORTEC GEM Series P-type HPGe crystal that is 65 mm in diameter x 50 mm in length and 40% relative efficiency. The large HPGe crystal increases sensitivity and reduces time to MDA. The “over-square” geometry means best absolute efficiency up to energies in excess of 2 MeV. All LDM-1 instruments use nominally identical germanium crystals. A cutaway drawing showing the construction materials is available on request from ORTEC and is suitable for most Monte-Carlo modeling programs