Radiant energy – Ionic separation or analysis
Reexamination Certificate
1999-09-15
2002-09-24
Anderson, Bruce (Department: 2881)
Radiant energy
Ionic separation or analysis
C250S282000
Reexamination Certificate
active
06455844
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates generally to the field of accelerator mass spectrometry. More particularly, the invention relates to accelerator mass spectrometers employing a multicharged ion source.
2. Discussion of the Related Art
The main difficulty in single atom detection of C-14 arises from the isobaric interferences due to N-14 atomic ions and
12
CH
2
and
13
CH molecular ions. In conventional accelerator mass spectrometry (AMS) the approach consists of using a negative ion source to eliminate the
14
N contamination, since it does not support a stable negative ion, accelerating the negative ion beam in a tandem accelerator to high energy (few MeV), and then dissociating molecular ions isobaric with
14
C
−
also present in the ion beam either in a foil or gas target. Subsequent stages of electrostatic and magnetic analysis are then used to isolate the
14
C ions prior to their detection. Conventional AMS requires large, nuclear physics scale facilities, with correspondingly high cost, which are usually not dedicated to a single task, and entails time consuming sample preparation prior to the actual measurements, and so is not suited to quasi-real time monitoring Of C-14 levels.
SUMMARY OF THE INVENTION
The invention includes an apparatus and method for the detection of carbon-14 and other rare isotopes where molecular ion isobaric interferences are a problem, and where interfering atomic isobars do not form stable negative ions. In this invention, large nuclear physics scale facilities such as used in conventional accelerator mass spectrometry (AMS), for example, are not needed.
These, and other, goals and embodiments of the invention will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following description, while indicating preferred embodiments of the invention and numerous specific details thereof, is given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the invention without departing from the spirit thereof, and the invention includes all such modifications.
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“Electron Cyclotron Resonance Multiply Charged Ion Sources”, R. Geller, Apr. 1979, vol NS-26, No 2, Part 1, IEEE Nuclear and Plasma Sciences Society, pp. 2120-2127.
“Accelerator Mass Spectrometry for Measurement of Long-Lived Radioisotopes”, David Elmore & Fred M. Phillips, Science, May 1, 1987, vol. 236, No. 4801, p. 500, 543-550.
“Nanogan II 14.5 GHz: a compact ECRIS for on line production of multicharged radioactive ion beams for Spiral”, L. Maunoury, et al., Proceedings of 13th Int'l. Workshop on ECR Ion Sources, Feb. 26-28, 1997, College Station, Texas (Hosted by Cyclotron Institute, Texas A&M University).
“Time Scales for Charge Equilibration of Oq+(3≦q≦8) Ions during Surface-Channeling Interactions with Au (110)”, L. Folkerts et al, Physical Review Letters (The American Physical Society), Mar. 20, 1995, vol. 74, No. 12, p. 2204-2207.
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Anderson Bruce
Gray Cary Ware & Freidenrich
Hashmi Zia R.
Lockheed Martin Energy Research
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