Moshe Gai

Solar fusion cross-sections

We review and analyze the available information on the nuclear-fusion cross sections that are most important for solar energy generation and solar neutrino production. We provide best values for the low-energy cross-section factors and, wherever possible, estimates of the uncertainties. We also describe the most important experiments and calculations that are required in order to improve our knowledge of solar fusion rates.

Total interaction and proton-removal cross-section measurements for the proton-rich isotopes 7Be, 8B, and 9C

Abstract In an experiment performed at the FRS of GSI, we measured total interaction cross sections for 7 Be, 8 B, and 9 C, one-proton-removal cross sections for 8 B and 9 C as well as two-proton-removal cross sections for 9 C on targets ranging from carbon to lead at an energy of 285 MeV/nucleon. In addition, we performed measurements at 142 MeV/nucleon for 8 B. The experimental results are compared to different calculations. Glauber-type calculations with different model·density distributions show that, down to incident energies of about 50 MeV/nucleon, total interaction cross-section measurements with light targets are not sensitive to an extended proton distribution in 8 B. However, at lower incident energies, a tail in the proton density distribution is needed to explain the total interaction cross sections. Total interaction cross-section measurements with high-Z targets in the present experiment show a significant increase of the cross sections due to low-lying electromagnetic strength.

Destruction of 7Li and 7Be in astrophysical environments

Abstract The destruction of 7 Li and 7 Be in astrophysical environments is essential for understanding several stellar and cosmological processes and is not well understood, though earlier 7 Li + 3 He experiments have been performed [1]. The primordial abundance of 7 Li after Big Bang Nucleosynthesis (BBN) plays a major role in our understanding of the early universe [2]. The value of the baryon to photon ratio (η) deduced from BBN combined with measurements of the cosmic microwave background provide some of the strongest and earliest evidence for the existance of non-baryonic dark matter [2]. The destruction of 7 Be during the hot-pp cycle may alter our conclusions on the production of carbon in this process, which is thought to compete with the triple-α process for the production of 12 C, as the reaction 7 Be( 3 He, 2α)2p competes with 7 Be( 4 He, γ) 11 C and may reduce carbon production [3]. These stellar and cosmological environments involve high temperatures, and thus, effective burning energies (Gamow windows) that are quite high. Experiments using 7 Be targets inevitably involve interactions with 7 Li as background due to the 7 Li daughters from the beta decay of 7 Be. The experiments were performed at the Weizmann Institute VDG Laboratory using 3 He beams from 390 keV to 1130 keV on 7 LiF foil targets and 7 Be implanted targets. Results from measurements using 10 μg 7 LiF foil targets will be discussed.

Coulomb dissociation of 8B at 254 MeV/u

We have measured the Coulomb-dissociation cross section for 8 B→ 7 Be+p in the field of 208 Pb for a wide range of 0.15–2.95 MeV at E in =254 MeV/u . The preliminary results agree with Monte Carlo simulations that used the 7 Be(p,γ) 8 B cross sections measured by Filippone et al., and Vaughn et al. and assuming E1 (+M1) Coulomb dissociation process. Further analysis is in progress.

Novel targets for the production of the secondary radioactive beams: 7Be and 15O

In this paper we describe recent advances in the production of RNBs of 7Be and 15O with possible application for the production of 17F. The production of 7Be relies on chemical separation method of 7Be from a massive LiF production target, and for the 15O we used targets fabricated at the Jet Process Corporation (JPC), New Haven, CT, using the proprietary Jet Vapor Deposition (JVD)™ method.