We report on the transmission and reflection terahertz (THz) spectra of the high explosives RDX and PETN. These
common military explosives are compared to simulants L-tartaric acid and sucrose, respectively. The use of these
simulants enables researchers to develop many aspects of THz spectroscopy for explosives detection without the need
for live explosives. Further, we discuss the effect of sample preparation on the THz spectrum of RDX and demonstrate
that experiments performed on different terahertz instruments at multiple laboratories show quantitative agreement
between spectra recorded with four different instruments.