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Piston Corer Dynamics

CHATS (Core Head Acceleration and Tilt System) measures the motions (acceleration, tilt and depth) of a piston corer. It has been installed on the Atlantic Geoscience Centre (AGC) piston corer, a 30 m long 11 cm i.d. piston core system which has been developed at AGC. A companion instrument, PAL (Piston Acceleration Logger), has also been installed in the lower half of the split piston. The purpose of these instruments is twofold. First, by recording and analyzing the dynamic performance of the core head and piston during free fall and bottom penetration, we hope to improve both the coring system and the operating procedures. This should result in longer and less disturbed samples of seafloor sediments. Second, measured decelerations of the corer as it penetrates the seafloor should give estimates of the physical properties of the seafloor sediments. This should make the corer double as a "free fall penetrometer". This paper will describe the instruments used and present Detailed motions of the core head, the data from actual cores. piston and the wire above the trip arm have been measured.