S. Daigle

Radioisotope studies of the farmville meteorite using γγ-coincidence spectrometry.

Radionuclides are cosmogenically produced in meteorites before they fall to the surface of the Earth. Measurement of the radioactive decay of such nuclides provides a wealth of information on the irradiation conditions of the meteorite fragment, the intensity of cosmic rays in the inner solar system, and the magnetic activity of the Sun. We report here on the detection of (26)Al using a sophisticated spectrometer consisting of a HPGe detector and a NaI(Tl) annulus. It is shown that modern γ-ray spectrometers represent an interesting alternative to other detection techniques. Data are obtained for a fragment of the Farmville meteorite and compared to results from Geant4 simulations. In particular, we report on optimizing the detection sensitivity by using suitable coincidence gates for deposited energy and event multiplicity. We measured an (26)Al activity of 48.5±3.5dpm/kg for the Farmville meteorite, in agreement with previously reported values for other H chondrites.

Measurement of {sup 17}O(p,gamma){sup 18}F between the narrow resonances at E{sub r}{sup lab}=193 and 519 keV

The {sup 17}O(p,gamma){sup 18}F reaction sensitively influences hydrogen burning nucleosynthesis in a number of stellar sites, including classical novae. These thermonuclear explosions, taking place in close binary star systems, produce peak temperatures in the range of T=100-400 MK. Recent results indicate that the thermonuclear rates for this reaction in this particular temperature range are dominated by the direct capture process. We report on the measurement of the {sup 17}O(p,gamma){sup 18}F cross section between the narrow resonances at E{sub r}{sup lab}=193 and 519 keV, where the S factor is expected to vary smoothly with energy. We extract the direct capture contribution from the total cross section and demonstrate that earlier data are inconsistent with our results.

Resonance strength in {sup 22}Ne(p,gamma){sup 23}Na from depth profiling in aluminum

A novel method for extracting absolute resonance strengths has been investigated. By implanting

Measurement of the e r c.m. = 138 keV resonance in the 23 Na(p, γ) 24 Mg reaction and the abundance of sodium in AGB stars

^{22}\mathrm{Ne}

Measurement of O17(p,γ)F18 between the narrow resonances at Erlab=193 and 519keV

ions into a thick aluminum backing and simultaneously measuring the

Resonance strength in Ne22(p,γ)Na23 from depth profiling in aluminum

^{22}\mathrm{Ne}

Measurement of the Erc.m.=259 keV resonance in the N14(p,γ)O15 reaction

+p

Performance of A Compact Multi-crystal High-purity Germanium Detector Array for Measuring Coincident Gamma-ray Emissions

and

Thermonuclear reaction rate for 18 O(p,γ) 19 F

^{27}\mathrm{Al}