Showing papers by "Grant M. Raisbeck published in 1984"

Measurement of 10Be with a tandetron accelerator operating at 2 MV

Abstract: A General Ionex Corporation “3 MV” Tandetron accelerator mass spectrometer system, operating at a nominal terminal voltage of 2 MV, has been used to measure 10Be. Separation of 10B from 10Be has been achieved by a combination of differential energy loss in a stripping foil, range absorption, and dE/dx−E identification in the detector. The overall efficiency (10Be ions detected per BeO− ions injected into the accelerator) is at present ∼ 5%, and the background level equivalent to 10Be/9Be ∼ 3 × 10−14. These values are approximately 30 times larger and 15 times lower respectively, than values recently reported by the Arizona group [6] using a similar machine. Using a higher terminal voltage, it should be possible to improve our performance significantly. A description of the technique and the first results using natural samples are presented.

Investigation of the possible association of 10Be and 26Al with biogenic matter in the marine environment

Abstract: As part of a more general investigation of the mechanism by which 10Be and 26Al are transported in the ocean, and eventually incorporated in various marine reservoirs, and the extent to which they are homogenized with 9Be and 27Al, we are studying the possible association of these isotopes with biogenic matter in the marine environment. To this end we have made measurements of 10Be and 9Be in: (a) the carbonate fraction of several marine animals (clam, cockel, starfish, mussel) and the organic fraction of mussels; (b) 20 samples of a 460 m coral reef core extending from the present to ∼ 7 Ma ago; (c) 2 samples of marine plankton; (d) 1 sample of paniculate matter in ocean surface water. 26Al has been measured in two coral samples. 10Be measurements have been made on the Grenoble cyclotron, the University of Pennsylvania tandem and, most recently, on the French Tandetron. 26Al was measured at the Pennsylvania tandem. 9Be and 27Al were measured using flameless atomic absorption spectrometry. These investigations have taken on added significance with the discovery of 10Be in crude petroleum, and the possibility that 14Be concentration (or 10Be/9Be ratios) might be used to estimate the age of recent petroleum, or petroleum precursor, formation.