D. Filipescu

Gamma ray beams for Nuclear Astrophysics: first results of tests and simulations of the ELISSA array

The Extreme Light Infrastructure-Nuclear Physics (ELI-NP) facility, under construction in Magurele near Bucharest in Romania, will provide high-intensity and high-resolution gamma ray beams that can be used to address hotly debated problems in nuclear astrophysics. For this purpose, a silicon strip detector array (named ELISSA) will be realized in a common effort by ELI-NP and INFN-LNS (Catania, Italy), in order to measure excitation functions and angular distributions over a wide energy and angular range. A prototype of ELISSA was built and tested at Laboratori Nazionali del Sud (INFN-LNS) in Catania with the support of ELI-NP. On this occasion, we carried out experiments with alpha sources and with a 11 MeV 7Li beam. Thanks to our approach, the first results of those tests show up a very good energy resolution (better than 1%) and very good position resolution, of the order of 1 mm. Below 1 MeV, a resolution of the order of 6 mm is found, still good enough for the measurement of angular distribution and the kinematical identification of the reactions induced on the target by gamma beams.

Low-energy enhancement in theγ-ray strength functions ofGe73,74

Author(s): Renstrom, T; Nyhus, HT; Utsunomiya, H; Schwengner, R; Goriely, S; Larsen, AC; Filipescu, DM; Gheorghe, I; Bernstein, LA; Bleuel, DL; Glodariu, T; Gorgen, A; Guttormsen, M; Hagen, TW; Kheswa, BV; Lui, YW; Negi, D; Ruud, IE; Shima, T; Siem, S; Takahisa, K; Tesileanu, O; Tornyi, TG; Tveten, GM; Wiedeking, M | Abstract:

Low-energy enhancement in the γ-ray strength functions of 73,74Ge

Author(s): Renstrom, T; Nyhus, HT; Utsunomiya, H; Schwengner, R; Goriely, S; Larsen, AC; Filipescu, DM; Gheorghe, I; Bernstein, LA; Bleuel, DL; Glodariu, T; Gorgen, A; Guttormsen, M; Hagen, TW; Kheswa, BV; Lui, YW; Negi, D; Ruud, IE; Shima, T; Siem, S; Takahisa, K; Tesileanu, O; Tornyi, TG; Tveten, GM; Wiedeking, M | Abstract:

Geant4 simulations on Compton scattering of laser photons on relativistic electrons

Using Geant4, a complex simulation code of the interaction between laser photons and relativistic electrons was developed. We implemented physically constrained electron beam emittance and spacial distribution parameters and we also considered a Gaussian laser beam. The code was tested against experimental data produced at the γ-ray beam line GACKO (Gamma Collaboration Hutch of Konan University) of the synchrotron radiation facility NewSUBARU. Here we will discuss the implications of transverse missallignments of the collimation system relative to the electron beam axis.

Photoneutron Reactions in Nuclear Astrophysics

Highly-monochromatic γ-ray beams are produced at the NewSUBARU synchrotron radiation facility by the inverse Compton scattering of laser photons from relativistic electrons. The latest s-process study in nuclear astrophysics with the γ-ray beam is presented.

Absolute photoneutron cross sections of Sm isotopes

Photoneutron cross sections for seven samarium isotopes, 144Sm, 147Sm, 148Sm, 149Sm, 150Sm, 152Sm and 154Sm, have been investigated near neutron emission threshold using quasimonochromatic laser-Compton scattering γ-rays produced at the synchrotron radiation facility NewSUBARU. The results are important for nuclear astrophysics calculations and also for probing γ-ray strength functions in the vicinity of neutron threshold. Here we describe the neutron detection system and we discuss the related data analysis and the necessary method improvements for adapting the current experimental method to the working parameters of the future Gamma Beam System of Extreme Light Infrastructure - Nuclear Physics facility.

Half-life of the Iπ = 4− Intruder State in 34P Using LaBr3:Ce Fast Timing

The half-life of the Iπ = 4− intruder state at 2305 keV in 3415P19 has been measured using γ-ray coincident fast timing with LaBr3:Ce scintillation detectors. Excited states in 34P were populated in the 18O(18O,pn)34P reaction at a beam energy of 36 MeV at the Tandem Laboratory at the National Institute of Physics and Nuclear Engineering, Bucharest, Romania. A half-life of t1/2 ~ 2 ns was obtained for the 4− state, giving an M2 reduced transition probability consistent with similar transitions in this mass region and confirming the intruder-parity nature of the state.

Lifetime measurements by the Doppler-shift attenuation method in the {sup 115}Sn({alpha},n{gamma}){sup 118}Te reaction

{gamma} rays were measured at several angles in both singles and coincidence modes in the {sup 115}Sn({alpha},n{gamma}){sup 118}Te reaction at 15 MeV on a thick target. Multipolarities and mixing ratios were determined from the {gamma}-ray angular distribution analysis. Lifetimes of 11 low- and medium-spin excited states in {sup 118}Te were determined from a Monte Carlo Doppler-shift attenuation method analysis of the Doppler broadened line shapes of {gamma} rays deexciting the levels. The results are discussed in comparison with the predictions of the interacting boson model.

Calculation of the Reaction Cross Section for Several Actinides

New, self‐consistent, neutron‐induced reaction cross‐section calculations for 235,238U, 237Np, and 231,232,233Pa have been performed. The statistical model code STATIS was extended to take into account the multi‐modality of the fission process. The three most dominant fission modes, the two asymmetric standard I (S1) and standard II (S2) modes, and the symmetric superlong (SL) mode have been taken into account. De‐convoluted fission cross sections for these modes in 235,238U(n,f) and 237Np(n,f) based on experimental branching ratios, were calculated for the first time up to the second chance fission threshold. For 235U(n,f) and 233Pa(n,f), the calculations being made up to 50 MeV and 20 MeV incident neutron energy, respectively, higher fission chances have been considered. This implied the need for additional calculations for the neighbouring isotopes.As a side product also mass yield distributions could be calculated at energies hitherto not accessible by experiment. Experimental validation of the predic...