The 3He(4He,gamma) 7Be reaction plays an important role in determining the high energy solar neutrino flux and in understanding the abundances of primordial 7Li. This Letter reports a new precision measurement of the cross sections of this direct capture reaction, determined by measuring the ensuing 7Be activity in the region of Ec.m.=420 to 950 keV. Various recent theoretical fits to our data result in a consistent extrapolated value of S34(0)=0.53(2)(1) keV b.

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High levels of naturally occurring and carcinogenic radium isotopes have been measured in low-saline and oxic groundwater from the Rum Group of the Disi sandstone aquifer in Jordan. The combined 228Ra and 226Ra activities are up to 2000% higher than international drinking water standards. Analyses of the host sandstone aquifer rocks show 228Ra and 226Ra activities and ratios that are consistent with previous reports of sandstone rocks from different parts of the world. A compilation of previous data in groundwater from worldwide sandstone aquifers shows large variations in Ra activities regardless of the groundwater salinity. On the basis of the distribution of the four Ra isotopes and the ratios of the short- to long-lived Ra isotopes, we postulate that Ra activity in groundwater is controlled by the balance of radioactive decay of parent Th isotopes on aquifer solids, decay of the dissolved radium isotopes, and adsorption of dissolved Ra on solid surfaces. The availability of surface adsorption sites, which depends on the clay content in the aquifer rocks, is therefore an important constraint for Ra activity in sandstone aquifers. These findings raise concerns about the safety of this and similar nonrenewable groundwater reservoirs, exacerbating the already severe water crisis in the Middle East.

The 7 Be(p,␥) 8 B reaction plays a central role in the evaluation of solar neutrino fluxes. We report on a new precision measurement of the cross section of this reaction, following our previous experiment with an implanted 7 Be target, a raster-scanned beam, and the elimination of backscattering losses. The new measurement incorporates a higher activity 7 Be target and a number of improvements in design and procedure. The cross section at a selected energy E c.m. ϭ850 keV ͑where c.m. stands for center of mass͒ was measured several times under varying experimental conditions, yielding a value of S 17 (E c.m. ϭ850 keV)ϭ24.0 Ϯ0.5 eV b, to serve as a benchmark. Measurements were carried out at lower energies as well. Due to the precise knowledge of the implanted 7 Be density profile, it was possible to reconstitute both the off-and on-resonance parts of the cross section and to obtain from the entire set of measurements an extrapolated value of S 17 (0)ϭ21.2Ϯ0.7 eV b, using the cluster model of Descouvemont and Baye.

The 7 Be(p,γ) 8 B reaction plays a central role in the evaluation of solar neutrino fluxes. We report on a new precision measurement of the cross section of this reaction, following our previous experiment with an implanted 7 Be target, a raster-scanned beam and the elimination of backscattering losses. The new measurement incorporates a higher activity 7 Be target and a number of improvements in design and procedure. The cross section at a selected energy of Ec.m. = 850 keV was measured several times under varying experimental conditions, yielding a value of S17(Ec.m. = 850 keV) = 24.0 ± 0.5 eV b, to serve as a benchmark. Measurements were carried out at lower energies as well. Due to the precise knowledge of the implanted 7 Be density profile it was possible to reconstitute both the off-and on-resonance parts of the cross section and to obtain from the entire set of measurements an extrapolated value of S17(0) =21.2 ± 0.7 eV b, using the cluster model of Descouvemont and Baye.

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The free-surface Liquid-Lithium Target, recently developed at Soreq Applied Research Accelerator Facility (SARAF), was successfully used with a 1.9 MeV, 1.2 mA (2.3 kW) continuous-wave proton beam. Neutrons (~2 × 10(10) n/s having a peak energy of ~27 keV) from the (7)Li(p,n)(7)Be reaction were detected with a fission-chamber detector and by gold activation targets positioned in the forward direction. The setup is being used for nuclear astrophysics experiments to study neutron-induced reactions at stellar energies and to demonstrate the feasibility of accelerator-based boron neutron capture therapy.