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[en] OAK-B135 Tandem Terminal Ion Source. The terminal ion source (TIS) was used in several experiments during this reporting period, all for the(sup 7)Be((gamma))(sup 8)B experiment. Most of the runs used(sup 1)H(sup+) at terminal voltages from 0.3 MV to 1.5 MV. One of the runs used(sup 2)H(sup+) at terminal voltage of 1.4 MV. The other run used(sup 4)He(sup+) at a terminal voltage of 1.37 MV. The list of experiments run with the TIS to date is given in table 1 below. The tank was opened four times for unscheduled source repairs. On one occasion the tank was opened to replace the einzel lens power supply which had failed. The 10 kV unit was replaced with a 15 kV unit. The second time the tank was opened to repair the extractor supply which was damaged by a tank spark. On the next occasion the tank was opened to replace a source canal which had sputtered away. Finally, the tank was opened to replace the discharge bottle which had been coated with aluminum sputtered from the exit canal
[en] OAK-B135 Tandem Terminal Ion Source. The terminal ion source (TIS) was used in several experiments during this reporting period, all for the 7Be(γ)8B experiment. Most of the runs used 1H+ at terminal voltages from 0.3 MV to 1.5 MV. One of the runs used 2H+ at terminal voltage of 1.4 MV. The other run used 4He+ at a terminal voltage of 1.37 MV. The list of experiments run with the TIS to date is given in table 1 below. The tank was opened four times for unscheduled source repairs. On one occasion the tank was opened to replace the einzel lens power supply which had failed. The 10 kV unit was replaced with a 15 kV unit. The second time the tank was opened to repair the extractor supply which was damaged by a tank spark. On the next occasion the tank was opened to replace a source canal which had sputtered away. Finally, the tank was opened to replace the discharge bottle which had been coated with aluminum sputtered from the exit canal
[en] The nuclear photo-emulsion method makes it possible to study in detail the fragmentation of a projectile thanks to a high resolution capability of emulsion and the detection of secondaries in a 4π geometry. The registration of all charged particles and their identification enable one to explore the isotopic composition of fragments and the projectile fragmentation channels. In the paper are presented results on an investigation of 8B interactions with photo-emulsion nuclei. A detailed analysis made it possible to justify selections of events of nuclear fragmentation 8B→2He + p.
[en] Fusion cross sections were measured for the exotic proton-halo nucleus 8B incident on a 58Ni target at several energies near the Coulomb barrier. This is the first experiment to report on the fusion of a proton-halo nucleus. The resulting excitation function shows a striking enhancement with respect to expectations for normal projectiles. Evidence is presented that the sum of the fusion and breakup yields saturates the total reaction cross section.
[en] Fusion involving weakly bound stable and radioactive nuclei is a topic of current interest and is not well understood. While systems involving stable projectiles show below barrier fusion enhancement as compared to one dimensional barrier penetration model prediction due to coupling to their internal degrees of freedoms, systems involving weakly bound stable nuclei show overall fusion suppression in addition to the below barrier enhancement. Recently measured fusion cross sections for weakly bound radioactive 8B ion on a 58Ni target shows enhancement at all energies rather than showing enhancement at bellow barrier energies only. This has been attributed to proton halo nature of 8B
[en] Total reaction cross sections, σR, for 8B, 12C, and 14N on natSi were measured from about 20 to 60 MeV/A. The σR for 12C and 14N compared reasonably well with conventional strong absorption and microscopic calculations. Measured σR for 8B were slightly larger than those for the two heavier nuclei, and notably larger than the conventional calculations. The 8B data were well reproduced by microscopic calculations using the same matter distribution used to explain the 8B guadrupole moment data, and therefore provide new evidence for the existence of a proton halo in 8B
[en] We discuss the use of one-nucleon breakup reactions of loosely bound nuclei at intermediate energies as an indirect method in nuclear astrophysics. These are peripheral processes, therefore from breakup reaction data we can extract asymptotic normalization coefficients (ANC) from which reaction rates of astrophysical interest can be precisely evaluated. In particular, the breakup of 8B and 9C is described in detail in terms of an extended Glauber model. The results of this new analysis lead to the astrophysical factor S17(0) = 18.7 ± 1.9 eVb for the key reaction for solar neutrino production 7Be(p,γ)8B. We discuss a proposed use of the breakup of proton drip line nucleus 23Al to obtain the stellar reaction rate for 22Mg(p,γ)23Al. (author)
[en] The Coulomb dissociation of 8B, measured with high precision by the GSI group, is in excellent agreement with the astrophysical cross section factor (S17) measured by the Weizmann group with a 7Be target. The GSI and Weizmann data are in good agreement with the Seattle data at high energies, but at low energies we observe a slight systematic (up to 2σ) deviation, yet the Seattle group repeatedly rejects the CD method. We show that when plotting the slopes, they mis plotted one CD data point and exclude measured slopes that contradict their claim. Indeed, the measured slope is essential to elucidate the d-wave correction to S17(0) that could be as large as 15%, and is the last open question that needs to be resolved before S17(0) can be quoted with an accuracy of 5% or better. We show that this goal has not been achieved (in spite of the strong claim of the Seattle group), since currently there is no agreement among experiments as well as among theoretical models on the value of the slope. In addition, currently there is no theoretical framework within which (for example the Seattle) data can be analyzed and S17(0) extrapolated with the claimed high precision of 2.5%. This (last) issue of the slope and the d-wave correction must be resolved (by future measurements) so as to allow quoting S17(0) with an accuracy of 5% or better. (author)
[en] The astrophysical interest of the Tours Symposium 1994 is summarized, including studies of various nuclear reaction chains, relevant for the energy and element production in stellar environments and of the particle streams ejected in the cosmos, in particular the solar neutrino flux and high-energy cosmic rays, with the highest individual particle energies in our Universe. The Coulomb dissociation process in the field of large Z nuclei has attracted a great deal of attention. The B8→Be7 + p and the O16→C12 + α reactions are discussed in detail. (K.A.). 20 refs