Improving the detection limit for 182 Hf
Date
2007
Authors
Winkler, Stephan
Fifield, L Keith
Tims, Stephen
Morton, Clyde
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Publisher
Elsevier
Abstract
A nearby supernova would deposit radionuclides on earth. The long-lived radionuclide 182Hf (t1/2 = 8.9 Ma) is one of a number of candidates for an isotopic signature of such an event. Together with 60Fe, observation of 182Hf would be direct evidence for a supernova site of the r-process. The most suitable site for searching for such a signature would be a deep-sea sediment of slow deposition rate. Measurement of 182Hf at the anticipated level requires very effective suppression of the interfering stable isobar 182W. Chemical separation and the injection of HfF5- allow for suppression by several orders of magnitude, but more is needed for detection of 182Hf as a supernova isotope signature. We are currently developing AMS methods for measuring 182Hf/180Hf isotope ratios at the required level using a 15 MV tandem accelerator . Both projectile X-ray emission and the use of a solid passive absorber with a subsequent measurement of the residual energy are being explored. The former suffers from low efficiency, but the latter looks promising.
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Keywords
Keywords: Energy dissipation; Galaxies; Particle accelerators; Radiation detectors; Radioisotopes; Sediments; Deposition rate; Residual energy; Supernova; Hafnium 182Hf; AMS; Energy-loss; Supernova
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Source
Nuclear Instruments and Methods in Physics Research: Section B
Type
Journal article
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2037-12-31