Radiant energy – Ionic separation or analysis – Methods
Patent
1981-09-08
1984-01-17
Smith, Alfred E.
Radiant energy
Ionic separation or analysis
Methods
250286, 250288, H01J 4942, B01D 5944
Patent
active
044265760
ABSTRACT:
Apparatus and methods of operation are described for determining, with isotopic selectivity, the number of noble gas atoms in a sample. The analysis is conducted within an evacuated chamber which can be isolated by a valve from a vacuum pumping system capable of producing a pressure of 10.sup.-8 Torr. Provision is made to pass pulses of laser beams through the chamber, these pulses having wavelengths appropriate for the resonance ionization of atoms of the noble gas under analysis. A mass filter within the chamber selects ions of a specific isotope of the noble gas, and means are provided to accelerate these selected ions sufficiently for implantation into a target. Specific types of targets are discussed. An electron measuring device produces a signal relatable to the number of ions implanted into the target and thus to the number of atoms of the selected isotope of the noble gas removed from the gas sample. The measurement can be continued until a substantial fraction, or all, of the atoms in the sample have been counted.
Furthermore, additional embodiments of the apparatus are described for bunching the atoms of a noble gas for more rapid analysis, and for changing the target for repetitive cycling of the gas in the chamber. The number of repetitions of the cyclic steps depend upon the concentration of the isotope of interest, the separative efficiency of the mass filter, etc. The cycles are continued until a desired selectivity is achieved. Also described are components and a method of operation for a pre-enrichment operation for use when an introduction of a total sample would elevate the pressure within the chamber to levels in excess of those for operation of the mass filter, specifically a quadrupole mass filter.
Specific examples of three noble gas isotope analyses are described.
REFERENCES:
patent: 3987302 (1976-10-01), Hurst et al.
patent: 4329582 (1982-05-01), French et al.
McGee et al., "Refrigerated Inlet Arrangement . . . ", Review of Scientific Instruments, vol. 37, No. 5, May 1966, pp. 561-566.
Armour et al., "Apparatus for the Study . . . ", Vacuum, vol. 22, No. 10, Oct. 1972, pp. 457-462.
Joshi et al., "New Detector . . . ", Review of Scientific Instruments, vol. 46, No. 5, May 1975, pp. 559-561.
Chen Chung-Hsuan
Hurst G. Samuel
Parks James E.
Payne Marvin G.
Atom Sciences, Inc.
Berman Jack I.
Smith Alfred E.
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