f Development of a gammadensity probe for in-situ shallow seabed investigation (MAST - GISP project)

A gammadensity probe is presently being developed at Ifremer in the framework of the Mast I Gisp (Geophysical in-situ probe) project. The probe itself is derived from standard density devices commonly used in the oil industry, and which involve Compton scattering (Ellis 1987, Desbrande 1982, Serra 1979). The two basic components of the probe are a 137Cs radioactive source and a gamma counter consisting of a sodium iodide crystal (NaI). The probe will be employed for in-situ high resolution density measurements in soft sediments at the seafloor. Such in-situ measurements are of first interest for the determination of the physical characteristics of the sediments, in particular to calibrate the geophysical data (seismic and sidescan-sonar) .