Bulletin of the American Physical Society
2017 Fall Meeting of the APS Division of Nuclear Physics
Volume 62, Number 11
Wednesday–Saturday, October 25–28, 2017; Pittsburgh, Pennsylvania
Session JC: Nuclear Astrophysics IV |
Hide Abstracts |
Chair: Anna Simon, University of Notre Dame Room: Salon 3 |
Friday, October 27, 2017 10:30AM - 10:42AM |
JC.00001: R-process experiments with the Advanced Implantation Detector Array Alfredo Estrade, Chris Griffin, Tom Davinson, Carlo Bruno, Oscar Hall, Zhong Liu, Phil Woods, Patrick Coleman-Smith, Marc Labiche, Ian Lazarus, Victor Pucknell, John Simpson, Laura Harkness-Brennan, Robert Page, Gabor Kiss, Jiajiang Liu, Keishi Matsui, Shunji Nishimura, Vi Phong, Giuseppe Lorusso, Fernando Montes, Neerajan Nepal Decay properties of neutron rich isotopes, such as half-lives and $\beta$-delayed neutron emission probabilities, are an important input for astrophysical models of the r-process. A new generation of fragmentation beam facilities has made it possible to access large regions of the nuclear chart that are close to the path of the r-process for some astrophysical models. The Advanced Implantation Detector Array (AIDA) is a segmented active-stopper detector designed for decay experiments with fast ion beams, which was recently commissioned at the Radioactive Ion Beam Factory in RIKEN, Japan. In this presentation we describe the main characteristics of AIDA, and present preliminary results of the first experiments in the region of neutron-rich selenium isotopes and along the N=82 shell closure. [Preview Abstract] |
Friday, October 27, 2017 10:42AM - 10:54AM |
JC.00002: Recent results of reverse engineering nuclear masses from solar r-process abundances and the challenges faced in the presence of fissioning nuclei Nicole Vassh The astrophysical site(s) of the rapid neutron capture process (r-process) remains one of the most challenging open problems in all of physics. Conclusive statements are difficult to make due to a limited knowledge of nuclear physics far from stability. We describe recent developments in the method of "reverse engineering" nuclear properties using well established observational data for the rare earth elements. This new theoretical framework is intended to be used in combination with recent and future measurements to gain new insights into the astrophysical site of the r-process. To do so we perform this procedure for a variety of astrophysical environments in order to differentiate between the trends in the mass surface required to fit the rare earth solar data. We present results for the most recent reverse engineering mass predictions given the astrophysical trajectory of a hot, low entropy wind and compare to the mass data for neutron rich neodymium isotopes recently measured at the CPT at CARIBU. Since fission properties of nuclei far from stability are experimentally unknown, neutron rich environments present challenges to the reverse engineering approach. We describe these challenges and the impact of fission properties, such as fragment yield distributions and fission rates, on the r-process abundance pattern. [Preview Abstract] |
Friday, October 27, 2017 10:54AM - 11:06AM |
JC.00003: Precision Mass Measurements of Neutron-Rich Rare-Earth Nuclei Rodney Orford, Fritz Buchinger, Jason Clark, Jeffrey Klimes, Mary Burkey, Guy Savard, Dmitry Gorelov, Kumar Sharma One of the open problems in nuclear astrophysics is the identification of the astrophysical site of the rapid neutron capture process (\textit{r} process). Due to the lack of experimental nuclear data of neutron-rich nuclei far from stability, it remains difficult to constrain or judge the accuracy of \textit{r}-process models and calculations. The Canadian Penning Trap mass spectrometer (CPT) is located in the CARIBU facility at Argonne National Laboratory where intense beams of neutron-rich isotopes are created from the spontaneous fission of a $^{252}$Cf source. The implementation of a phase-imaging mass measurement technique (PI-ICR) at the CPT in conjunction with the MR-TOF mass separator at CARIBU has improved our experimental sensitivity by more than two orders of magnitude. Recently, PI-ICR was used to make the first direct mass measurements of a number of neutron-rich rare-earth isotopes near N = 100. The phase-imaging technique, and insights from these new masses into possible \textit{r}-process sites will be discussed. [Preview Abstract] |
Friday, October 27, 2017 11:06AM - 11:18AM |
JC.00004: Half-Lives of the Neutron-Rich $N\approx82$ Isotopes $^{128-130}$Cd and $^{131}$In Ryan Dunlop Half-lives of $N=82$ nuclei below doubly-magic $^{132}$Sn are key input parameters for calculations of any astrophysical $r$-process scenario and play an important role in the formation and shape of the second $r$-process abundance peak. Shell-model calculations of neutron-rich nuclei near the $N=82$ neutron shell closure that are not yet experimentally accessible have been performed by adjusting the quenching of the Gamow-Teller (GT) operator to reproduce the $^{130}$Cd half-life. The calculated half-lives of other nuclei in the region are known to be systematically too long. Recently, a shorter half-life for $^{130}$Cd was measured that resolves this discrepancy by scaling the GT quenching by a constant factor for all of the nuclei in the region. However, the reduced quenching of the GT operator creates a new discrepancy in the calculated half-life of $^{131}$In. The measurement of $^{131}$In is complicated due to the presence of three known $\beta$-decaying states with roughly the same half-life, making photopeak gating an ideal method to measure each of these half-lives. In this talk, the half-lives of $^{128-130}$Cd and $^{131}$In, as well as the spectroscopy of $^{131}$Sn, measured using the GRIFFIN $\gamma$-ray spectrometer at TRIUMF will be presented. [Preview Abstract] |
Friday, October 27, 2017 11:18AM - 11:30AM |
JC.00005: Pioneering mass measurements in the rare-earth region for the astrophysical r-process James M Kelly, Markus Vilen, Maxime Brodeur, Anu Kankainen The astrophysical r-process generates around half of the elements heavier than iron, yet precisely where or how this occurs remains a topic of intense inquiry. Understanding the formation of one of its hallmarks, the rare-earth abundance peak, could shed light on the astrophysical sites because this feature is very sensitive to underlying nuclear properties, particularly to nuclear binding energies which have so far been largely derived from theoretical mass models. We have performed precise atomic mass measurements of 12 neutron-rich rare-earth isotopes using the JYFLTRAP double Penning trap mass spectrometer. The atomic masses of $^{\mathrm{158}}$Nd, $^{\mathrm{160}}$Pm, $^{\mathrm{162}}$Sm, and $^{\mathrm{164-166}}$Gd have been experimentally determined for the first time, and the precisions for $^{\mathrm{156}}$Nd, $^{\mathrm{158}}$Pm, $^{\mathrm{162,163}}$Eu, $^{\mathrm{163}}$Gd, and $^{\mathrm{164}}$Tb have been significantly improved. The $^{\mathrm{163}}$Gd measurement also indicates the presence of a previously suspected isomeric state. Trends in two-neutron separation energies are compared to theoretical mass model predictions, and the effects of these new mass measurements on r-process abundance calculations will be examined. [Preview Abstract] |
Friday, October 27, 2017 11:30AM - 11:42AM |
JC.00006: The S-Process Branching-Point at $^{\mathrm{205}}$PB Anton Tonchev, N. Tsoneva, C. Bhatia, C.W. Arnold, S. Goriely, S.L. Hammond, J.H. Kelley, E. Kwan, H. Lenske, J. Piekarewicz, R. Raut, G. Rusev, T. Shizuma, W. Tornow Accurate neutron-capture cross sections for radioactive nuclei near the line of beta stability are crucial for understanding $s$-process nucleosynthesis. However, neutron-capture cross sections for short-lived radionuclides are difficult to measure due to the fact that the measurements require both highly radioactive samples and intense neutron sources. We consider photon scattering using monoenergetic and 100{\%} linearly polarized photon beams to obtain the photoabsorption cross section on $^{\mathrm{206}}$Pb below the neutron separation energy. This observable becomes an essential ingredient in the Hauser-Feshbach statistical model for calculations of capture cross sections on 205Pb. The newly obtained photoabsorption information is also used to estimate the Maxwellian-averaged radiative cross section of $^{\mathrm{205}}$Pb(n,g)$^{\mathrm{206}}$Pb at 30 keV. The astrophysical impact of this measurement on s-process nucleosynthesis will be discussed. [Preview Abstract] |
Friday, October 27, 2017 11:42AM - 11:54AM |
JC.00007: Thermal Effects in Dense matter beyond mean field theory Sudhanva Lalit, Constantinos Constantinou, Madappa Prakash The formalism of next-to-leading order Fermi Liquid Theory is employed to calculate the thermal properties of symmetric nuclear and pure neutron matter in a relativistic many-body theory beyond the mean field level which includes two-loop effects. For all thermal variables, the semi-analytical next-to-leading order corrections reproduce results of the exact numerical calculations for entropies per baryon up to 2. This corresponds to excellent agreement down to subnuclear densities for temperatures up to $20$ MeV. In addition to providing physical insights, a rapid evaluation of the equation of state in the homogeneous phase of hot and dense matter is achieved through the use of the zero-temperature Landau effective mass function and its derivatives. [Preview Abstract] |
Friday, October 27, 2017 11:54AM - 12:06PM |
JC.00008: Direct studies of neutron-induced reactions in inverse kinematics Shea Mosby, Aaron Couture, Michelle Mosby, Rene Reifarth Some of the major questions in both nuclear astrophysics and nuclear technology depend on neutron-induced reaction rates which are largely unknown, on nuclei which are too short-lived to directly measure with existing experimental methods. Indirect methods have progressed, by either attempting to determine the reaction rate explicitly or by constraining nuclear structure for reaction models. Despite this progress, systematic uncertainties associated with the techniques remain a persistent issue. It has been shown that the combination of a radioactive beam facility, ion storage ring, and spallation neutron source could enable direct measurements of neutron-induced reaction rates for nuclei with half-lives as short as minutes or less. We have analyzed the feasibility of this technique using the LANSCE accelerator complex as a baseline. The technique and initial results from the feasibility analysis will be presented. [Preview Abstract] |
Friday, October 27, 2017 12:06PM - 12:18PM |
JC.00009: Gravity Acceleration and Gravity Paradox Han Yongquan, Tang Yuteng The magnitude of the gravitational acceleration of the earth is derived from law of universal gravitation. If the size and mass of the gravitational force are proportional in any situation, then the celestial surface gravity is greater than the celestial center gravity, and objective facts do not match. Specific derivation method, F $=$ GMm / R$^{\mathrm{2\thinspace }}=$ mg, g $=$ GM / R$^{\mathrm{2}}$ ... ¢Ù, G is the gravitational constant, M is the mass of the earth, and finally the g $=$ 9.8 m / s$^{\mathrm{\thinspace 2\thinspace }}$is obtained. We assume that the earth is a standard sphere, the earth's volume V $=$ 4$\Pi $R$^{\mathrm{3}}$ / 3, assuming that the earth's density is $\rho $, then M $= \quad \rho $4$\Pi $R$^{\mathrm{3}}$ / 3 ... ¢Ú, ¢Ú into the¢Ù get: g $=$ G$\rho $4$\Pi $R / 3 ... ¢Û, the density of the earth is constant. Careful analysis of the formula ¢Û The result of this calculation, we can reach conclusion the gravity acceleration g and the radius of the earth is proportional. In addition to the radius of the Earth,on the right of the¢Û is constant, That is, the Earth's Gravity acceleration of the outer layer of the earth is greater than the Earth's Gravity acceleration of Inner layer We are in No1 High School, Huairou ,Beijing, China [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700