Thu·Jul 16, 2015Thursday·July 16, 2015

1. 01*

   The first direct measurement of 12C(12C,n)23Mg at stellar energies

   B. Bucher🇺🇸 · X.D. Tang🇨🇳 · X. Fang🇺🇸 · A. Heger🇦🇺 · S. Almaraz-Calderon🇺🇸 · A. Alongi🇺🇸 · A.D. Ayangeakaa🇺🇸 · M. Beard🇺🇸 · A. Best🇺🇸 · J. Browne🇺🇸 · C. Cahillane🇺🇸 · M. Couder🇺🇸 and 19 other authors

   Neutrons produced by the carbon fusion reaction 12C(12C,n)23Mg play an important role in stellar nucleosynthesis. However, past studies have shown large discrepancies between experimental data and theory, leading to an uncertain cross section extrapolation at astrophysical energies. We present the first direct measurement that extends deep into the astrophysical energy range along with a new and improved extrapolation technique based on experimental data from the mirror reaction 12C(12C,p)23Na. The new reaction rate has been determined with a well-defined uncertainty that exceeds the precision required by astrophysics models. Using our constrained rate, we find that 12C(12C,n)23Mg is crucial to the production of Na and Al in Pop-III Pair Instability Supernovae. It also plays a non-negligible role in the production of weak s-process elements as well as in the production of the important galactic gamma-ray emitter 60Fe.

   nucl-exastro-ph.SRPRL(2015)·35 citations
2. 02*

   Characterization of the scission point from fission-fragment velocities

   M. Caamaño🇪🇸 · F. Farget🇫🇷 · O. Delaune🇫🇷 · K.-H. Schmidt🇫🇷 · C. Schmitt🇫🇷 · L. Audouin🇫🇷 · C.-O. Bacri🇫🇷 · J. Benlliure🇪🇸 · E. Casarejos🇪🇸 · X. Derkx🇫🇷 · B. Fernández-Domínguez🇪🇸 · L. Gaudefroy🇫🇷 and 7 other authors

   The isotopic-yield distributions and kinematic properties of fragments produced in transfer-induced fission of 240Pu and fusion-induced fission of 250Cf, with 9 MeV and 45 MeV of excitation energy respectively, were measured in inverse kinematics with the spectrometer VAMOS. The kinematic properties of identified fission fragments allow to derive properties of the scission configuration such as the distance between fragments, the total kinetic energy, the neutron multiplicity, the total excitation energy, and, for the first time, the proton- and neutron-number sharing during the emergence of the fragments. These properties of the scission point are studied as functions of the fragment atomic number. The correlation between these observables, gathered in one single experiment and for two different fissioning systems at different excitation energies, give valuable information for the understanding and modeling of the fission process.

   nucl-exnucl-thPRC(2015)·62 citations
3. 03*

   The origin of the background radioactive isotope Xe-127 in the sample of Xe enriched in Xe-124

   Yu.M. Gavrilyuk🇷🇺 · A.M. Gangapshev🇷🇺 · V.V. Kazalov🇷🇺 · V.V. Kuzminov🇷🇺 · S.I. Panasenko🇺🇦 · S.S. Ratkevich🇺🇦 · D.A. Tekueva🇷🇺 · S.P. Yakimenko🇷🇺

   The results of investigation of Xe-127 radioactive isotope production in the xenon sample enriched in Xe-124, Xe-126, Xe-128 are presented. The isotope is supposed to be the source of the background events in the low-background experiment on search for 2K-capture of Xe-124. In this work we consider two channels of Xe-127 production: the neutron knock-out from Xe-128 nucleus by cosmogenic muons and the neutron capture by Xe-126 nucleus. For the first channel the upper limit of the cross section of Xe-127 production was found to be sigma >= 0.007 barn at 95\% C.L. For the second channel the value obtained for the cross section was found to be equal to sigma =(2.74+-0.4) barn, which coincides well, within the statistical error, with reference value.

   nucl-exphysics.ins-detPhys.Part.Nucl.(2017)·2 citations
4. 04*

   Feasibility study of heavy ion beams and compound target materials for muon production

   Jaebum Son · Ju Hahn Lee · Gi Dong Kim · Yong Kyun Kim

   We have investigated the feasibility of using compound materials as target for muon production by virtue of simulations using a GEANT4 toolkit. A graphite and two thermostable compound materials, beryllium oxide (BeO) and boron carbide (B4C) were considered as muon production targets and their muon production rates for 600-MeV proton beam were calculated and compared. For thermal analysis, total heat deposited on the targets by the proton beams and the secondary particles was calculated with a MCNPX code, and then the temperature distribution of target was derived from the calculated heat by using an ANSYS code with consideration for heat transfer mechanisms, such as thermal conduction and thermal radiation. In addition, we have investigated whether the heavy ion beams can be utilized for muon production. For various beam species such as 3He2, 4He, 7Li, 10B and 12C, their muon production rates were calculated and compared with that obtained for a proton beam.

   ↳ physics.ins-detnucl-exphysics.acc-phJ.Korean Phys.Soc.(2015)·0 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.