Bulletin of the American Physical Society
2008 Annual Meeting of the Division of Nuclear Physics
Volume 53, Number 12
Thursday–Sunday, October 23–26, 2008; Oakland, California
Session BD: Mini-Symposium: Rare Isotope Science I |
Hide Abstracts |
Chair: W. David Kulp, Georgia Institute of Technology Room: Jewett Ballroom G-H |
Friday, October 24, 2008 8:30AM - 9:06AM |
BD.00001: Rare Isotope Science Invited Speaker: The development of radioactive-beam facilities worldwide, such as those at ISOLDE, TRIUMF-ISAC, the NSCL, HBIBF, RIKEN, GANIL, GSI, etc., has provided a tremendous potential for nuclear science in general and specifically nuclear physics. The ability to produce record-intensity radioactive-ion beams both near and far from stability has enabled new avenues of research in nuclear structure, nuclear astrophysics, weak-interaction studies, material science, and applied physics. Combined with the development of production facilities, significant advancements in instrumentation have occurred that maximize sensitivity to the physics events of interest in the presence of, at times, very large radioactive backgrounds. An overview of the two main production techniques, ISOL and fast-fragmentation, will be given, together with some selected developments in spectrometers and detection systems. Some physics highlights that have resulted from these advancements will be outlined. Finally, recent results and future prospectives for nuclear physics studies at the TRIUMF-ISAC facility, currently the world's most powerful ISOL facility, will be presented, including plans for a 500 kW electron linac driver for photofission. [Preview Abstract] |
Friday, October 24, 2008 9:06AM - 9:18AM |
BD.00002: Further results in the search for the direct two-proton decay of $^{94}$Ag$^{m }$(J$^{\pi }$= 21$^{+}$, 6.7 MeV) J. Cerny, D.W. Lee, K. Perajarvi, D.M. Moltz, B.R. Barquest, L.E. Grossman, W. Jeong, C.C. Jewett Both direct one-proton decay and direct two-proton decay of $^{94}$Ag$^{m}$ from this 0.4 s isomeric state have been reported in experiments utilizing the GSI on-line mass separator [1]. In the latter decay, coincident events between silicon E detectors with a threshold energy of 0.4 MeV and a summed decay energy of 1.9$\pm $0.1 MeV were observed with a yield of 350$\pm $210 pb in coincidence with $\gamma $-decays in the $^{92}$Rh daughter. We utilized our helium-jet system at the LBNL 88-inch cyclotron to repeat this experiment, again employing the $^{58}$Ni($^{40}$Ca,p3n) reaction at 197 MeV. Reaction products were transported via a capillary to a detection area and collected on a slowly rotating wheel in front of an assembly of 24 $\Delta $E$_{gas}-\Delta $E$_{gas}$-E$_{Si}$ detector telescopes with a threshold of 0.4 MeV for identifying protons. Five of these telescopes observe the 0.79 MeV single proton decay from $^{94}$Ag$^{m}$ at the reported yield of 1.3 nb. In the 240/276 identified proton detector combinations with low background, no proton-proton coincidences have been observed. Data from the remaining 36 detector combinations require a separate analysis, which is in progress. Monte Carlo analyses of our anticipated proton-proton coincidences for both sets of detector combinations will be presented. $^{ 1}$Mukha et al., Nature \underline {439}, 298 (2006). [Preview Abstract] |
Friday, October 24, 2008 9:18AM - 9:30AM |
BD.00003: Probing Exotic, Particle-Decay Isotopes: A New Application of the Recoil Distance Method P. Voss, P. Adrich, T. Baumann, D. Bazin, D. Enderich, D. Miller, R. Norris, S. Progovac, A. Ratkiewicz, A. Spyrou, K. Starosta, M. Thoennessen, C. Vaman, A. Dewald, H. Iwasaki The application of the Recoil Distance Method (RDM) with the NSCL/K\"{o}ln plunger [1] has proven useful in the study of picosecond-lifetime excited states of rare isotopes at the NSCL [2]. With precise control over target/degrader separation distances on the micrometer scale, replacing the passive degrader with an active silicon detector provides a new probe at fast beam fragmentation facilities for studies of exotic particle-decay isotopes with picosecond lifetimes along the proton drip line. A recent experiment at the NSCL utilized this resulting NSCL/K\"{o}ln ``particle plunger'' in a lifetime study of the two-proton emitter $^{19}$Mg, produced by the one-neutron knockout of a $^{20}$Mg secondary beam. The method and preliminary results for this commissioning particle plunger RDM investigation will be presented. [1] A. Dewald \textit{et al.}, GSI Scientific Report 2005, p. 38 (2006). [2] K. Starosta \textit{et al.}, Phys. Rev. Lett. {\bf 99}, 042503 (2007). [Preview Abstract] |
Friday, October 24, 2008 9:30AM - 9:42AM |
BD.00004: Ultra-High Precision Half-Life Measurement for the Superallowed $\beta^+$ Emitter $^{26}$Al$^m$ P. Finlay, G. Demand, P.E. Garrett, K.G. Leach, A.A. Phillips, C.S. Sumithrarachchi, C.E. Svensson, S. Triambak, G.C. Ball, D. Bandyopadhyay, M. Djongolov, S. Ettenauer, G. Hackman, C.J. Pearson, S.J. Williams, C. Andreoiu, D. Cross, R.A.E. Austin, G.F. Grinyer, J.R. Leslie The calculated nuclear structure dependent correction for $^{26}$Al$^m$ ($\delta_{C}-\delta_{NS} = 0.305(27)\%$ [1]) is smaller by nearly a factor of two than the other twelve precision superallowed cases, making it an ideal case to pursue a reduction in the experimental errors contributing to the $\mathcal{F}${\em t} value. An ultra-high precision half-life measurement for the superallowed $\beta^+$ emitter $^{26}$Al$^m$ has been made using a 4$\pi$ continuous gas flow proportional counter as part of an ongoing experimental program in superallowed Fermi $\beta$ decay studies at the Isotope Separator and Accelerator (ISAC) facility at TRIUMF in Vancouver, Canada, which delivered a beam of $\sim 10^5$ $^{26}$Al$^m$/s in October 2007. With a statistical precision of $\sim0.008\%$, the present work represents the single most precise measurement of any superallowed half-life to date. \\ \newline [1] I.S.~Towner and J.C.~Hardy, Phys. Rev. C {\bf 77}, 025501 (2008). [Preview Abstract] |
Friday, October 24, 2008 9:42AM - 9:54AM |
BD.00005: Quadrupole Moment of $^{37}$K K. Minamisono, P.F. Mantica, H.L. Crawford, J.S. Pinter, J.B. Stoker, R.R. Weerasiri, Y. Utsuno The electric quadrupole coupling constant of the ground state of $^{37}$K($I^{\pi}$ = 3/2$^+$, $T_{1/2}$ = 1.22 s) in a tetragonal KH$_2$PO$_4$ single crystal was measured to be $|eqQ/h| = 2.99 \pm 0.07$ MHz. The experiment was performed at NSCL using a newly-developed $\beta$-ray detecting nuclear quadrupole resonance system. The electric quadrupole moment of $^{37}$K was determined to be $|Q(^{37}{\rm K})| = 10.6 \pm 0.4$ $e$ fm$^2$, where the known electric quadrupole coupling constant of stable $^{39}$K in the KH$_2$PO$_4$ crystal [1] was used as a reference. The present experimental result is consistent with but more precise than the previous value (11 $\pm$ 4 $e$ fm$^2$) measured by laser spectroscopy [2]. The present result is larger than that predicted by shell-model calculations in the $sd$ or the $sd$ and $fp$ model spaces. Evaluation of effective charges in this region of the chart of nuclides will be presented as one means to reconcile the discrepancy between experiment and theory. [1] J. Seliger, V. Zagar, Phys. Rev. B 49, 14918 (1994). [2] J. A. Behr et al., Phys. Rev. Lett. 79, 375 (1997). [Preview Abstract] |
Friday, October 24, 2008 9:54AM - 10:06AM |
BD.00006: $\beta -$decay studies of nuclides in the $^{100}$Sn region at NSCL Giuseppe Lorusso, Alan Amthor, Thomas Baumann, Daniel Bazin, Ana Becerril, Heather Crawford, Alfredo Estrade, Alexandra Gade, Thomas Ginter, Carol Guess, Mark Hausmann, Wes Hitt, Paul Mantica, Milan Matos, Rianon Meharchand, Kei Minamisono, Fernando Montes, Giorgios Perdikakis, Jorque Pereira, Jill Pinter, Mauritio Portillo, Hendrik Schatz $\beta -$decay nuclides in the immediate neighborhood of $^{100}$Sn, were studied at NSCL using the $\beta $-Counting system (BCS) and the Segmented Germanium Array (SeGA). The nuclei of interest were implanted into the BCS double-sided silicon strip detector and properties from both implantations and the subsequent $\beta $-decays were recorded on an event-by-event basis, allowing for the direct observation of the half-lives and the $\beta $-delayed proton emission branching ratios. The BCS also contains a stack of Si detectors and a Ge planar detector downstream of the implantation detector to measure the total energy of the emitted beta particles, and hence the $\beta $-decay end-point energy. The properties of those nuclei are not only relevant for rp-process calculations but also are essential to understand the structure of the single particle states far from the line of stability, providing stringent tests of nuclear models in this region. [Preview Abstract] |
Friday, October 24, 2008 10:06AM - 10:18AM |
BD.00007: Low-energy transitions in $^{112}$Cd identified in the beta-decays of $^{112}$Ag and $^{112}$In K.L. Green, P.E. Garrett, G.A. Demand, G.F. Grinyer, K.G. Leach, A.A. Phillips, M.A. Schumaker, C.E. Svensson, J. Wong, G.C. Ball, D.S. Bandyopadhyay, G. Hackman, A.C. Morton, C.J. Pearson, R.A.E. Austin, S. Colosimo, D. Cross, J.L. Wood, W.D. Kulp, S.W. Yates The Cd isotopes, especially $^{112}$Cd, have been considered exceptional examples of vibrational nuclei. While many level lifetimes are known in $^{112}$Cd, previous measurements lacked sensitivity to weak, low-energy branches that are often the most important transitions to establish collectivity. We have sought these branches through a high-statistics measurement of the $\beta$ decay of $^{112}$Ag and $^{112}$In to $^{112}$Cd using the 8$\pi$ spectrometer at the TRIUMF-ISAC facility. The data were collected in scaled-down $\gamma$ singles and $\gamma\gamma$ coincidence mode, and $\sim$100$\times$10$^6$ events were sorted into a random-background-subtracted $\gamma\gamma$ matrix. New branches from levels below 2.5 MeV were observed, and a higher precision on several branching ratios, especially the 4$^{+}$ and 0$^{+}$ doublet of states at 1871 keV, has been achieved. Details of the analysis to date will be reported. Work supported in part by NSERC and the US DOE under grant DE-FG02-96ER40958. [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