HIGH-SENSITIVITY MASS SPECTROMETRIC MEASUREMENT OF STABLE HELIUM AND ARGON ISOTOPES PRODUCED BY HIGH-ENERGY PROTONS IN IRON

Journal Article · Thu Jan 15 00:00:00 EST 1959 · Physical Review (U.S.) Superseded in part by Phys. Rev. A, Phys. Rev. B: Solid State, Phys. Rev. C, and Phys. Rev. D

DOI:https://doi.org/10.1103/PhysRev.113.674· OSTI ID:4257496

Schaeffer, O A; Zahringer, J

A high-sensitivity mass spectrometer was used to measure the helium, argon, and neon produced in iron by 0. 16-, 0.43-, and 3.0-Bev protons. The spectrometer has a sensitivity so that 10 /sup -11/ it standard cc of helium could be detected above the contamination level. The He/sup 4/ cross sections are 120 mb, 450 mb, and 1300 mb at 0. 16, 0.43, and 3.0 Bev, respectively, while the He/sup 3/He/sup 4/ cross section ratios are, respectively, 0.09, 0.10, and 0.18. At 0.43 Bev, cross sections of 1.0 mb, 3.3 mb, 8 mb, and 4.1 mb were found for the argon isotopes 36, 37, 38, and 39, respectively. The cross section for neon-21 is 0.1 mb at 0.43 Bev. The results are discussed in relation to evaporation theory and the rare gas coatent of iron meteorites. The He/sup 3/ yields are all higher than previously measured tritium values. At 3 Bev the He/ sup 3/T ratio is 2.4. It is suggested that in the case of iron in evaporation theory the Coulomb barrier is not as important relatively as previously thought. Alternatively, a large fraction of the He/sup 3/ and tritium may be prcduced during the nuclear cascade which precedes the evaporation from the excited nuclei. The cross sections measured bear directly on the cosmicray-produced rare gases in meteorites. From the cross section of directly produced He/sup 3/ relative to T, previous measurements of He/sup 3/-T exposure ages of iron meteorites must be reduced by a factor of about 3. From the argon isotope cross sections it is seen that 50% of the Ar/sup 36/ in meterites is the result of BETA decay of cosmic- ray-produced Cl/sup 36/ and thus Ar/sup 36/-Cl/sup 36/ should be a reliable method for measuring exposure ages of meteorites. (auth)

• Research Organization: Brookhaven National Lab., Upton, N.Y.
• NSA Number: NSA-13-010499
• OSTI ID: 4257496
• Journal Information: Physical Review (U.S.) Superseded in part by Phys. Rev. A, Phys. Rev. B: Solid State, Phys. Rev. C, and Phys. Rev. D, Vol. Vol: 113; Other Information: Orig. Receipt Date: 31-DEC-59
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

PHYSICS AND MATHEMATICS
AGE
ARGON 36
ARGON ISOTOPES
BACKGROUND
BETA DECAY
CHLORINE 36
COSMIC RADIATION
CROSS SECTIONS
ELECTRIC FIELDS
ENERGY
ENERGY LEVELS
ENERGY RANGE
EVAPORATION
HELIUM 3
HELIUM ISOTOPES
IRON
MASS SPECTROMETERS
MEASURED VALUES
METEORITES
NEON ISOTOPES
NUCLEAR THEORY
PRODUCTION
PROTON BEAMS
RARE GASES
STANDARDS
TRITIUM
VOLUME