Tue·Oct 20, 2015Tuesday·October 20, 2015

1. 01*

   Low-energy enhancement in the \gamma-ray strength functions of ${}^{73,74}$Ge

   T. Renstrøm🇳🇴 · H. -T. Nyhus🇳🇴 · H. Utsumoniya · R. Schwengner🇩🇪 · S. Goriely🇧🇪 · A. C. Larsen🇳🇴 · D. M. Filipescu🇷🇴 · I. Gheorghe🇷🇴 · L. A. Bernstein🇺🇸 · D. L. Bleuel🇺🇸 · T. Glodariu🇷🇴 · A. Görgen🇳🇴 and 13 other authors

   The $\gamma$-ray strength functions and level densities of ${}^{73,74}$Ge have been extracted up to the neutron separation energy S${}_n$ from particle-$\gamma$ coincidence data using the Oslo method. Moreover, the $\gamma$-ray strength function of ${}^{74}$Ge above S${}_n$ has been determined from photo-neutron measurements, hence these two experiments cover the range of E${}_{\gamma }\approx$ 1-13 MeV for ${}^{74}$Ge. The obtained data show that both ${}^{73,74}$Ge display an increase in strength at low $\gamma$ energies. The experimental $\gamma$-ray strength functions are compared with $M1$ strength functions deduced from average $B(M1)$ values calculated within the shell model for a large number of transitions. The observed low-energy enhancements in ${}^{73,74}$Ge are adopted in the calculations of the ${}^{72,73}$Ge(n,$\gamma$) cross sections, where there are no direct experimental data. Calculated reaction rates for more neutron-rich germanium isotopes are shown to be strongly dependent on the presence of the low-energy enhancement.

   nucl-exPRC(2016)·39 citations
2. 02*

   Results of measurements of an environment neutron background at BNO INR RAS objects with the helium proportional counter

   V.V. Alekseenko · I.R. Barabanov · R.A. Etezov · Yu.M. Gavrilyuk · A.M. Gangapshev · A.M. Gezhaev · V.V. Kazalov · A.Kh. Khokonov · V.V. Kuzminov · S.I. Panasenko · S.S. Ratkevich

   A method of measurements of the environmental neutron background at the Baksan Neutrino Observatory of the INR RAS are described. Measurements were done by using of a proportional counter filled with mixture of Ar(2 at)+${}^3$He(4 at). The results obtained at the surface and the underground laboratory of the BNO INR RAS are presented. It is shown that a neutron background in the underground laboratory at the 4900 m w.e. depth is decreased by $\sim 260$ times without any special shield in a comparison with the Earth surface. A neutron flux density in the 5-1323.5~cm air height region is constant within the determination error and equal to $(7.1\pm 0.1_{\mathrm{stat}}\pm 0.3_{\mathrm{syst}})\times 10^{-3}$ s${}^{-1}\cdot$cm${}^{-2}$.

   ↳ physics.ins-detnucl-ex2 citations
3. 03*

   Anatomy of molecular structures in ${}^{20}$Ne

   E. F. Zhou🇨🇳 · J. M. Yao🇯🇵 · Z. P. Li🇨🇳 · J. Meng🇨🇳 · P. Ring🇨🇳

   We present a beyond mean-field study of clusters and molecular structures in low-spin states of ${}^{20}$Ne with a multireference relativistic energy density functional, where the dynamical correlation effects of symmetry restoration and quadrupole-octupole shapes fluctuation are taken into account with projections on parity, particle number and angular momentum in the framework of the generator coordinate method. Both the energy spectrum and the electric multipole transition strengths for low-lying parity-doublet bands are better reproduced after taking into account the dynamical octupole vibration effect. Consistent with the finding in previous studies, a rotation-induced dissolution of the $\alpha {+}^{16}$O molecular structure in ${}^{20}$Ne is predicted.

   ↳ nucl-thnucl-exPLB(2016)·59 citations
4. 04*

   Response of diamond detector sandwich to 14 MeV neutrons

   M. Osipenko🇮🇹 · M. Ripani🇮🇹 · G. Ricco🇮🇹 · B. Caiffi🇮🇹 · F. Pompili · M. Pillon · G. Verona-Rinati · R. Cardarelli🇮🇹

   In this paper we present the measurement of the response of 50 $\mu$m thin diamond detectors to 14 MeV neutrons. Such neutrons are produced in fusion reactors and are of particular interest for ITER neutron diagnostics. Among semiconductor detectors diamond has properties most appropriate for harsh radiation and temperature conditions of a fusion reactor. However, 300-500 $\mu$m thick diamond detectors suffer significant radiation damage already at neutron fluences of the order of $10^{14}$ n/cm${}^2$. It is expected that a 50 $\mu$m thick diamond will withstand a fluence of $>10^{16}$ n/cm${}^2$. We tested two 50 $\mu$m thick single crystal CVD diamonds, stacked to form a "sandwich" detector for coincidence measurements. The detector measured the conversion of 14 MeV neutrons, impinging on one diamond, into $\alpha$ particles which were detected in the second diamond in coincidence with nuclear recoil. For ${}^{12}C(n,\alpha {)}^{9}Be$ reaction the total energy deposited in the detector gives access to the initial neutron energy value. The measured 14 MeV neutron detection sensitivity through this reaction by a detector of effective area 3$\times$3 mm${}^2$ was $5\times 10^{-7}$ counts cm${}^2$/n. This value is in good agreement with Geant4 simulations. The intrinsic energy resolution of the detector was found to be 240 keV FWHM which adds only 10 % to ITER's 14 MeV neutron energy spread.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2016)·3 citations
5. 05*

   Net-proton number kurtosis and skewness in nuclear collisions: Influence of deuteron formation

   Zuzana Feckova🇸🇰 · Jan Steinheimer🇩🇪 · Boris Tomasik🇸🇰 · Marcus Bleicher🇩🇪

   We explore the influence of deuteron formation in the late stage of nucleus-nucleus reactions on the fluctuations observed in the final net-proton yields around midrapidity. At each investigated energy, the produced (anti-)proton yield at chemical freeze-out is assumed to fluctuate according to a Poisson distribution and in each event the probability for deuteron formation by coalescence is proportional to $(d{N}_{\mathrm{proton}}/dy{)}^2$. The protons that are then clustered in deuterons are usually not included in the experimental measurement of the net-proton fluctuations, therefore, we subtract these clustered protons from the final state proton number for the calculation of the net-proton fluctuations (the same is done in the anti-proton sector). Due to the non-linear deuteron formation probability the resulting distribution is not a Skellam distribution, but shows the interesting feature of a decrease in the kurtosis $\kappa {\sigma }^2$ and a local maximum in the skewness $S\sigma$ observables as the collision energy decreases.

   ↳ nucl-thnucl-exPRC(2015)·24 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.