Ultra-sensitive mass spectroscopy using a tandem Van de Graaff accelerator to detect /sup 10/Be and /sup 26/Al
/sup 10/Be and /sup 26/Al are cosmic ray produced radioactive isotopes with half lives of 1.6 x 10/sup 6/ and .72 x 10/sup 6/ years, respectively. /sup 10/Be is produced at a rate of 2.0 x 10/sup -2/ atoms/cm/sup 2//sec and /sup 26/Al is produced at a rate of about 2 x 10..pi../sup 4/ atoms/cm/sup 2//sec. /sup 10/Be and /sup 26/Al are incorporated into the geologic sediments where they can be detected and used as geochronometers. The very low concentrations of these isotopes can be detected with ..beta.. decay counters or accelerator mass spectroscopy techniques (AMS), but the AMS techniques are two to three orders of magnitude more sensitive than the decay counting techniques. The Yale tandem Van de Graaff accelerator was used as a mass spectrometer to detect /sup 10/Be and /sup 26/Al. The ion source was modified so that it could generate 500 nA beams of BeO/sup -/ from 1/2 mg samples of BeO. The accelerator performance and stability was improved so that 30 nA of Be/sup 4 +/ could be analyzed, and this made it possible to detect /sup 10/Be in samples containing /sup 10/Be and /sup 9/Be in a ration of 10/sup -14/ atoms/atom. Only 15 nA of Al/sup -/ could be generated in the source, and 5 nA of Al/sup 5 +/ could be transmitted through to the detector chamber. We were able to detect /sup 26/Al in samples containing /sup 26/Al and /sup 27/Al in a ratio of 10/sup -12/ atoms/atom. The background levels of /sup 10/Be and /sup 26/Al were undetectable. (/sup 12/Be//sup 9/Be << 10/sup -4/ atoms/atom, /sup 26/Al//sup 27/Al << 10/sup -12/ atoms/atom.) Background counts due to the isobar /sup 10/B were easily separated form the /sup 10/Be signal by range energy loss techniques. A Mg isobaric background beam was not present in the Al beam because we chose to accelerate the Al/sup -/ ion, and Mg does not form a negative ion. Other background counts (eg. /sup 16/O, and /sup 12/C) were removed from the Al beam by an electrostatic analyzer.
- Research Organization:
- Yale Univ., New Haven, CT (USA)
- OSTI ID:
- 5020040
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GENERAL PHYSICS
58 GEOSCIENCES
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
IRON METEORITES
CHEMICAL COMPOSITION
MASS SPECTROSCOPY
VAN DE GRAAFF ACCELERATORS
PACIFIC OCEAN
SEDIMENTS
ALUMINIUM 26
ATMOSPHERIC PRECIPITATIONS
BERYLLIUM 10
COSMIC RADIATION
DETECTION
EXPERIMENTAL DATA
HALF-LIFE
RADIOACTIVITY
SEA BED
TANDEM ELECTROSTATIC ACCELERATORS
ACCELERATORS
ALKALINE EARTH ISOTOPES
ALUMINIUM ISOTOPES
BERYLLIUM ISOTOPES
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BETA-PLUS DECAY RADIOISOTOPES
DATA
ELECTROSTATIC ACCELERATORS
EVEN-EVEN NUCLEI
INFORMATION
IONIZING RADIATIONS
ISOTOPES
LIGHT NUCLEI
METEORITES
NUCLEI
NUMERICAL DATA
ODD-ODD NUCLEI
RADIATIONS
RADIOISOTOPES
SEAS
SECONDS LIVING RADIOISOTOPES
SPECTROSCOPY
SURFACE WATERS
YEARS LIVING RADIOISOTOPES
640101* - Astrophysics & Cosmology- Cosmic Radiation
580400 - Geochemistry- (-1989)
400104 - Spectral Procedures- (-1987)