Electric and magnetic dipole strength in Zn 66

The dipole strength of the nuclide Zn66 was studied in photon-scattering experiments using bremsstrahlung produced with electron beams of energies of 7.5 and 13.4 MeV at the γELBE facility as well as using quasimonoenergetic and linearly polarized photon beams of 30 energies within the range of 4.3 to 9.9 MeV at the HIγS facility. A total of 128 J=1 states were identified, among them 9 with 1+ and 86 with 1- assignments. The quasicontinuum of unresolved transitions was included in the analysis of the spectra and the intensities of branching transitions were estimated on the basis of simulations of statistical γ-ray cascades. As a result, the photoabsorption cross section up to the neutron-separation energy was determined and compared with predictions of the statistical reaction model. The experimental M1 strengths from resolved 1+ states are compared with results of large-scale shell-model calculations

核共鳴蛍光散乱を用いた鉛206の双極子遷移強度の測定

ドレスデン・ヘルムホルツセンター（HZDR）の制動放射線を用いて、Pb-206の双極子遷移強度の測定を行った。その結果、励起エネルギー3.7から8.2MeV領域において、88本の共鳴準位を観測した。また、得られた散乱強度データを用いて、不安定核Pb-205の中性子捕獲断面積の評価を行った。日本原子力学会において、本実験の測定手法および結果について説明し、得られた散乱強度から求めたガンマ線吸収断面積やPb-205の中性子捕獲断面積の評価結果について報告する。日本原子力学会秋の大

Photoexcitation of 76^{76}Ge

The dipole strength of the nuclide Ge76 was studied in photon-scattering experiments using bremsstrahlung produced with electron beams of energies of 7.8 and 12.3 MeV delivered by the electron linear accelerator of high brilliance and high brightness (ELBE). We identified 210 levels up to an excitation energy of 9.4 MeV and assigned spin J = 1 to most of them. The quasicontinuum of unresolved transitions was included in the analysis of the spectra and the intensities of branching transitions were estimated on the basis of simulations of statistical γ-ray cascades. The photoabsorption cross section up to the neutron-separation energy was determined and is compared with predictions of the statistical reaction model. The derived photon strength function is compared with results of experiments using other reactions.The dipole strength of the nuclide $^{76}$Ge was studied in photon-scattering experiments using bremsstrahlung produced with electron beams of energies of 7.8 and 12.3 MeV at the $\gamma$ELBE facility. We identified 210 levels up to an excitation energy of 9.4 MeV and assigned spin $J$ = 1 to most of them. The quasicontinuum of unresolved transitions was included in the analysis of the spectra and the intensities of branching transitions were estimated on the basis of simulations of statistical $\gamma$-ray cascades. The photoabsorption cross section up to the neutron-separation energy was determined and is compared with predictions of the statistical reaction model. The derived photon strength function is compared with results of experiments using other reactions

Electric and magnetic dipole strength in ⁶⁶Zn

The dipole strength of the nuclide 66Zn was studied in photon-scattering experiments using bremsstrahlung produced with electron beams of energies of 7.5 and 13.4 MeV at the γELBE facility as well as using quasimonoenergetic and linearly polarized photon beams of 30 energies within the range of 4.3 to 9.9 MeV at the HIγS facility. A total of 128 J=1 states were identified, among them 9 with 1+ and 86 with 1- assignments. The quasicontinuum of unresolved transitions was included in the analysis of the spectra and the intensities of branching transitions were estimated on the basis of simulations of statistical γ-ray cascades. As a result, the photoabsorption cross section up to the neutron-separation energy was determined and compared with predictions of the statistical reaction model. The experimental M1 strengths from resolved 1+ states are compared with results of large-scale shell-model calculations

Photo-response of the

The electric E1 and magnetic M1 dipole responses of the $$N=Z$$ nucleus $$^{24}$$Mg were investigated in an inelastic photon scattering experiment. The 13.0 MeV electrons, which were used to produce the unpolarised bremsstrahlung in the entrance channel of the $$^{24}$$Mg($$\gamma ,\gamma ^{\prime }$$) reaction, were delivered by the ELBE accelerator of the Helmholtz-Zentrum Dresden-Rossendorf. The collimated bremsstrahlung photons excited one $$J^{\pi }=1^-$$, four $$J^{\pi }=1^+$$, and six $$J^{\pi }=2^+$$ states in $$^{24}$$Mg. De-excitation $$\gamma$$ rays were detected using the four high-purity germanium detectors of the $$\gamma$$ELBE setup, which is dedicated to nuclear resonance fluorescence experiments. In the energy region up to 13.0 MeV a total $$B(M1)\uparrow = 2.7(3)~\mu _N^2$$ is observed, but this $$N=Z$$ nucleus exhibits only marginal E1 strength of less than $$\sum B(E1)\uparrow \le 0.61 \times 10^{-3}$$ e$$^2 \,$$fm$$^2$$. The $$B(\varPi 1, 1^{\pi }_i \rightarrow 2^+_1)/B(\varPi 1, 1^{\pi }_i \rightarrow 0^+_{gs})$$ branching ratios in combination with the expected results from the Alaga rules demonstrate that K is a good approximative quantum number for $$^{24}$$Mg. The use of the known $$\rho ^2(E0, 0^+_2 \rightarrow 0^+_{gs})$$ strength and the measured $$B(M1, 1^+ \rightarrow 0^+_2)/B(M1, 1^+ \rightarrow 0^+_{gs})$$ branching ratio of the 10.712 MeV $$1^+$$ level allows, in a two-state mixing model, an extraction of the difference $$\varDelta \beta _2^2$$ between the prolate ground-state structure and shape-coexisting superdeformed structure built upon the 6432-keV $$0^+_2$$ level

Study of the photon strength functions and level density in the gamma decay of the n + 234U reaction

The accurate calculations of neutron-induced reaction cross sections are relevant for many nuclear applications. The photon strength functions and nuclear level densities are essential inputs for such calculations. These quantities for 235U are studied using the measurement of the gamma de-excitation cascades in radiative capture on 234U with the Total Absorption Calorimeter at n_TOF at CERN. This segmented 4π gamma calorimeter is designed to detect gamma rays emitted from the nucleus with high efficiency. This experiment provides information on gamma multiplicity and gamma spectra that can be compared with numerical simulations. The code DICEBOXC is used to simulate the gamma cascades while GEANT4 is used for the simulation of the interaction of these gammas with the TAC materials. Available models and their parameters are being tested using the present data. Some preliminary results of this ongoing study are presented and discussed

New reaction rates for the destruction of 7Be during big bang nucleosynthesis measured at CERN/n_TOF and their implications on the cosmological lithium problem

New measurements of the 7Be(n,α)4He and 7Be(n,p)7Li reaction cross sections from thermal to keV neutron energies have been recently performed at CERN/n_TOF. Based on the new experimental results, astrophysical reaction rates have been derived for both reactions, including a proper evaluation of their uncertainties in the thermal energy range of interest for big bang nucleosynthesis studies. The new estimate of the 7Be destruction rate, based on these new results, yields a decrease of the predicted cosmological 7Li abundance insufficient to provide a viable solution to the cosmological lithium problem

Status and perspectives of the neutron time-of-flight facility n_TOF at CERN

Since the start of its operation in 2001, based on an idea of Prof. Carlo Rubbia [1], the neutron time of-flight facility of CERN, n_TOF, has become one of the most forefront neutron facilities in the world for wide-energy spectrum neutron cross section measurements. Thanks to the combination of excellent neutron energy resolution and high instantaneous neutron flux available in the two experimental areas, the second of which has been constructed in 2014, n_TOF is providing a wealth of new data on neutron-induced reactions of interest for nuclear astrophysics, advanced nuclear technologies and medical applications. The unique features of the facility will continue to be exploited in the future, to perform challenging new measurements addressing the still open issues and long-standing quests in the field of neutron physics. In this document the main characteristics of the n_TOF facility and their relevance for neutron studies in the different areas of research will be outlined, addressing the possible future contribution of n_TOF in the fields of nuclear astrophysics, nuclear technologies and medical applications. In addition, the future perspectives of the facility will be described including the upgrade of the spallation target, the setup of an imaging installation and the construction of a new irradiation area