  Interaction cross section measurements in fixed-target scattering experiments
are typically performed by measuring the attenuation of a beam of particles
that is incident upon a target slab of material. A fully active sampling
calorimeter, such as the time projection chamber, is a more voluminous target
that can be treated as a series of smaller target slabs. We present a method of
computing hadron-nucleus interaction cross sections for data taken with fully
active sampling calorimeters that is robust even if the target is comprised of
numerous slabs of various thicknesses.
