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An introduction to nuclear astrophysics

Description: The role of nuclear reactions in astrophysics is described. Stellar energy generation and heavy element nucleosynthesis is explained in terms of specific sequences of charged-particle and neutron induced reactions. The evolution and final states of stars are examined. 20 refs. 11 figs., 2 tabs.
Date: September 1, 1987
Creator: Norman, E.B.
Partner: UNT Libraries Government Documents Department

The interplay of nuclear and atomic physics in the synthesis of the elements

Description: In many astronomical environments, physical conditions are so extreme that matter is almost completely ionized. The absence of bound atomic electrons can dramatically alter the decay rates of a number of radioactive nuclei. Several examples of this interplay of nuclear and atomic physics relevant to the synthesis of the chemical elements are described. 16 refs., 4 figs.
Date: March 1, 1989
Creator: Norman, E.B.
Partner: UNT Libraries Government Documents Department

Influences of the astrophysical environment on nuclear decay rates

Description: In many astronomical environments, physical conditions are so extreme that nuclear decay rates can be significantly altered from their laboratory values. Such effects are relevant to a number of current problems in nuclear astrophysics. Experiments related to these problems are now being pursued, and will be described in this talk. 19 refs., 5 figs.
Date: September 1, 1987
Creator: Norman, E.B.
Partner: UNT Libraries Government Documents Department

Prospects for CUORE and Latest Results from CUORICINO

Description: CUORE (Cryogenic Underground Observatory for Rare Events) is a proposed next generation experiment designed to search for the neutrinoless DBD of {sup 130}Te using a bolometric technique. The present status of the CUORE is presented along with the latest results from its operating prototype, CUORICINO.
Date: January 5, 2006
Creator: Norman, E B
Partner: UNT Libraries Government Documents Department

Recent Developments in Neutrino Science: A Whole Lot About Almost Nothing

Description: Results from Super-K, SNO, and KamLAND provide strong evidence that neutrinos undergo flavor-changing oscillations and therefore have non-zero mass. The {nu}-disappearance observations by KamLAND, assuming CPT conservation, point to matter enhanced (MSW) oscillations with large mixing angles as the solution to the solar neutrino problem--a result consistent with the MSW parameters recently defined by these experiments. This requires that the observed neutrino flavors (e, {mu}, and tau) are not mass eigenstates, but are linear combinations of the mass eigenstates of the neutrino. However, such oscillation experiments can only determine the differences in the masses of the neutrinos, not the absolute scale of neutrino mass. What can be inferred from these experiments is that at least one species of neutrino has a mass greater than 55 meV. In fact, the WMAP observations of large-scale structure point to a sum-neutrino mass of {approx} 0.7 eV (roughly 0.25 eV/species assuming democracy between the flavors). Furthermore, there is still the important issue of whether the neutrino and anti-neutrino are distinct particles (i.e. Dirac type) or not (Majorana type). The only way to answer both of these questions is through neutrinoless double beta decay (DBD) experiments. CUORE (Cryogenic Underground Observatory for Rare Events) is a proposed next generation experiment designed to search for the neutrinoless DBD of {sup 130}Te using a bolometric technique. The source/detector will be composed of 988 5 x 5 x 5-cm single crystals of TeO{sub 2} all housed in a common dilution refrigerator and operated at a temperature of 8-10 mK. The total mass of {sup 130}Te contained in CUORE will be approximately 203 kg. Attached to each crystal will be one or more neutron-transmutation doped (NTD) germanium thermistors that will measure the small temperature rise produced in a crystal when radiation is absorbed. A schematic illustration of the CUORE detector ...
Date: August 22, 2005
Creator: Norman, E B
Partner: UNT Libraries Government Documents Department

On the road to the solution of the Solar Neutrino Problem

Description: The present status of solar neutrino experiments is reviewed. The discrepancy between the experimental results and the theoretical expectations has come to be known as the Solar Neutrino Problem. Possible solutions to this problem are discussed. The next generation of solar neutrino experiments are described.
Date: August 15, 1995
Creator: Norman, E.B.
Partner: UNT Libraries Government Documents Department

Stellar alchemy: The origin of the chemical elements

Description: What makes the stars shine? This question puzzled human beings for thousands of years. Early in this century, chemists and physicists discovered radioactivity; and the nuclear model of the atom was developed. Once nuclear reactions were produced in the laboratory, it did not take long before their role in stellar energy generation was realized. The theory that nuclear fusion is the source of stellar energy was initially developed in the 1930`s and was elaborated in detail in the 1950`s. Only within the last ten years, however, have astronomical observations provided direct confirmation of these theoretical ideas. In this paper, I describe the sequences of nuclear reactions that are believed to be responsible for the power generation in stars. The ashes of these reactions are the heavy elements that we find on earth and throughout the universe. The evolution and final fates of stars are examined. The key astronomical observations that provide support for these theoretical ideas are presented.
Date: March 13, 1994
Creator: Norman, E. B.
Partner: UNT Libraries Government Documents Department

Measurement of cross sections for alpha-induced reactions on 197Au and thick-target yields for the ((alpha),(gamma)) process on 64Zn and 63Cu

Description: We have measured the cross sections for the {sup 197}Au({alpha},{gamma}){sup 201}Tl and {sup 197}Au({alpha},2n){sup 199}Tl reactions in the 17.9- to 23.9-MeV energy range, and {sup 197}Au({alpha},n){sup 200}Tl reaction in the 13.4- to 23.9-MeV energy range using an activation technique. Thick-target yields for the {sup 64}Zn({alpha},{gamma}){sup 68}Ge (7- to 14-MeV) and {sup 63}Cu({alpha},{gamma}){sup 67}Ga (7-MeV) reactions were measured. For all measurements, natural elements were bombarded with He{sup +} beams from the 88'' Cyclotron at the Lawrence Berkeley National Laboratory (LBNL). Irradiated samples were counted using a g-spectrometry system at LBNL's Low Background Facility. Measured {sup 197}Au({alpha},{gamma}){sup 201}Tl cross-sections were compared with the NON-SMOKER theoretical values. The thick-target yields for the {sup 64}Zn({alpha},{gamma}){sup 68}Ge and {sup 63}Cu({alpha},{gamma}){sup 67}Ga reactions are also compared with the theoretical yield, calculated numerically using the energy dependent NON-SMOKER cross section data. In both cases, measured values are found to follow a trend of overlapping the predicted value near the alpha nucleus barrier height and fall below with a slowly widening difference between them in the sub barrier energy points.
Date: August 14, 2006
Creator: Basunia, M S; Shugart, H A; Smith, A R & Norman, E B
Partner: UNT Libraries Government Documents Department

Final Task Report on NRF Measurements of Photon Scattering Resonances in Plutonium at the High Voltage Research Laboratory of MIT

Description: Conclusions of this report are that there are 13 new transitions associated with NRF states in {sup 239}Pu that have been discovered. These resonances are between 2- and 2.5-MeV relative to the ground state in {sup 239}Pu. The strengths of most these resonances are between 15 and 20 eV b. This approximately is the strength required for using the transmission detection method for NRF [Pruet et al J. Appl. Phys. 99 12310 (2006)] for six-sigma alarm confidence levels. Future measurements on {sup 239}Pu at higher photon energies are necessary to probe for NRF strengths at higher energies. Such resonances may be more advantageous to the NRF technique with FINDER if they are stronger or if the mean free path of these energetic photons is longer.
Date: February 23, 2007
Creator: Johnson, M S; McNabb, D P & Norman, E B
Partner: UNT Libraries Government Documents Department

Effects of s-process branchings on stellar and meteoritic abundances

Description: The level scheme and electromagnetic properties of /sup 148/Pm have been studied using /sup 149/Sm(d,/sup 3/He) and /sup 148/Nd(p,n..gamma..) reactions. Combining these measurements with estimates for E2/M1 decay branching ratios leads to the tentative conclusion that /sup 148/Pm/sup g,m/ are in thermal equilibrium during the s-process. The branch at /sup 148/Pm then leads to an inferred s-process neutron density of 3 x 10/sup 8/ cm/sup -3/.
Date: December 1, 1985
Creator: Norman, E.B.; Lesko, K.T.; Crane, S.G.; Larimer, R.M. & Champagne, A.E.
Partner: UNT Libraries Government Documents Department

Measurements of cross sections relevant to. gamma. -ray line astronomy

Description: Gamma-ray production cross sections have been measured for the ..gamma..-ray lines which are mostly strongly excited in the proton bombardment of C, O, Mg, Si, and Fe targets of natural isotopic composition. High resolution germanium detectors were used to collect ..gamma..-ray spectra at proton bombarding energies of 20, 30, 33, 40 and 50 MeV. 6 refs., 6 figs.
Date: June 1, 1986
Creator: Lesko, K.T.; Norman, E.B.; Larimer, R.M. & Crane, S.G.
Partner: UNT Libraries Government Documents Department

Rapid detailed characterization of concrete shielding blocks utilizing internal natural radionuclides for calibration

Description: Following many years of productive work, the SuperHILAC and Bevalac accelerators at Lawrence Berkeley National Laboratory were closed, leaving thousands of concrete shielding blocks available for reuse or disposal. The process history of these blocks as shielding precludes free release pending radiological characterization. This paper presents a method for the rapid characterization of gamma-ray-emitting radioisotopes in large samples of earth-like materials: concrete shielding blocks in this case. Active regions are identified with a sensitive radiation-survey instrument and then examined in detail with a high-efficiency lead-shielded Ge spectrometer. Naturally-occurring gamma-ray emissions from the decays of uranium, thorium, and potassium are used to calibrate the spectrometer. A simple relationship exists between the observed counting rate in a characteristic gamma ray and the activity in the block. This method, taking only tens of minutes per sample at the nano-Curie/gram sensitivity level, replaces much of the expensive coring and laboratory analysis methods needed otherwise.
Date: October 1, 1995
Creator: McDonald, R.J.; Smith, A.R.; Norman, E.B. & Cowles, D.
Partner: UNT Libraries Government Documents Department

{Beta}{sup {minus}}-decay and cosmic-ray half-life of {sup 54}Mn

Description: A superconducting solenoid electron spectrometer operated in the lens mode was adapted to search for the {beta}{sup {minus}}-decay of {sup 54}Mn. The Compton-electron and other instrumental backgrounds have been significantly reduced by special shielding of the absorber system. An improved procedure has been developed to select the events by momenta. A limit of 2.7 {times} 10{sup {minus}5} has been established for the {beta}{sup {minus}} branch.
Date: May 1, 1995
Creator: Kibedi, T.; Kerr, M.; Dracoulis, G.D.; Byrne, A.P. & Norman, E.B.
Partner: UNT Libraries Government Documents Department

Cosmic ray half life of sup 56 Ni

Description: A search for the {beta}{plus} decay of {sup 56}Ni has established an upper limit on the branching ratio of 7.2 {times} 10{sup {minus} 7} for the most likely such transition. This provides a lower limit of 2.3 {times} 10{sup 4} years for the cosmic ray half life of {sup 56}Ni. 2 refs., 2 figs.
Date: August 1, 1989
Creator: Norman, E.B.; Sur, B.; Lesko, K.T.; Larimer, R.M. & Browne, E.
Partner: UNT Libraries Government Documents Department

Coexistence of a weakly-deformed band in a strongly-deformednucleus

Description: A weakly-deformed band J{sup {pi}} (E{sub x} keV) 0+ (1182), 2+ (1418), 4+ (1701) is identified in the strongly-deformed nucleus, {sup 154}Gd. Detailed {gamma}-ray spectroscopy following the beta decays of {sup 154}Eu (J = 3), {sup 154g,m1,m2}Tb (J = 0, 3, 7) are used to establish this structure. The structure is explained in terms of a pairing isomer which results from the {nu}[505] {up_arrow} Nilsson intruder orbital.
Date: October 27, 2002
Creator: Kulp, W.D.; Wood, J.L.; Krane, K.S.; Loats, J.; Schmelzenbach,P.; Stapels, C.J. et al.
Partner: UNT Libraries Government Documents Department

Fission Product Gamma-Ray Line Pairs Sensitive to Fissile Material and Neutron Energy

Description: The beta-delayed gamma-ray spectra from the fission of {sup 235}U, {sup 238}U, and {sup 239}Pu by thermal and near-14-MeV neutrons have been measured for delay times ranging from 1 minute to 14 hours. Spectra at all delay times contain sets of prominent gamma-ray lines with intensity ratios that identify the fissile material and distinguish between fission induced by low-energy or high-energy neutrons.
Date: November 15, 2007
Creator: Marrs, R. E.; Norman, E. B.; Burke, J. T.; Macri, R. A.; Shugart, H. A.; Browne, E. et al.
Partner: UNT Libraries Government Documents Department

A,B,C`s of nuclear science

Description: This introductory level presentation contains information on nuclear structure, radioactivity, alpha decay, beta decay, gamma decay, half-life, nuclear reactions, fusion, fission, cosmic rays, and radiation protection. Nine experiments with procedures and test questions are included.
Date: August 7, 1995
Creator: Noto, V.A.; Norman, E.B.; Chan, Yuen-Dat; Dairiki, J.; Matis, H.S.; McMahan, M.A. et al.
Partner: UNT Libraries Government Documents Department

On the half-life of {sup 44}Ti

Description: One of the few long-lived gamma-ray emitting radioisotopes expected to be produced in substantial quantities during a supernova explosion is {sup 44}Ti. The relevant portions of the decay schemes of {sup 44}Ti and its daughter {sup 44}Sc are shown. {sup 44}Ti decays to {sup 44}Sc emitting {gamma} rays of 68 and 78 keV. {sup 44}Sc subsequently decays with a 3.93-hour half life to {sup 44}Ca emitting an 1,157-keV {gamma}ray. This characteristic 1,157-keV {gamma} ray from the decay of {sup 44}Ti has recently been observed from the supernova remnant Cas A. In order to compare the predicted {gamma}-ray flux to that actually observed from this remnant, one must know the half-life of {sup 44}Ti. However, published values for this quantity range from 46.4 to 66.6 years. Given that the Cas A supernova is believed to have occurred approximately 300 years ago, this translates to an uncertainty by a factor of 4 in the amount of {sup 44}Ti ejected by this supernova. Thus, in order to provide an accurate and reliable value for this important quantity, the authors have performed a new experiment to determine the half-life of {sup 44}Ti. The authors produced {sup 44}Ti via the {sup 45}Sc(p,2n) reaction using 40 MeV protons from the Lawrence Berkeley National Laboratory`s 88-Inch Cyclotron. In the present experiment, the authors attempted to use all three {sup 44}Ti {gamma}-ray lines to determine its half life. However, analysis of the {sup 241}Am and {sup 137}Cs lines produced an incorrect value for the half life of each of these isotopes. On the other hand, the analysis of the {sup 22}Na line produced a result that agreed to within 0.5% of the known value of 2.603 years. Thus, they decided to concentrate their effort on the analysis of the 1,157-keV line. The half life of {sup 44}Ti that ...
Date: June 19, 1996
Creator: Norman, E.B.; Browne, E.; Chan, Y.D.; Goldman, I.D.; Larimer, R.M.; Lesko, K.T. et al.
Partner: UNT Libraries Government Documents Department

Cosmic ray half life of sup 54 Mn

Description: A search for the {beta}{sup +} decay of {sup 54}Mn has established an upper limit of 4.4 {times} 10{sup {minus}8} for this branching ratio, and a lower limit of 13.3 for the log ft value for this second forbidden unique transition. Assuming that the {beta}{sup {minus}} decay branch has the same log ft value, then its partial half life must be greater than 4 {times} 10{sup 4} years. Experiments to directly measure the {beta}{sup {minus}} decay rate of {sup 54}Mn are now in progress. 6 refs., 2 figs.
Date: August 1, 1989
Creator: Norman, E.B.; Sur, B.; Vogel, K.R.; Lesko, K.T.; Larimer, R.M. & Browne, E.
Partner: UNT Libraries Government Documents Department

sup 176 Lu: An unreliable s-process chronometer

Description: A level scheme of {sup 176}Lu up to {approximately}1400 keV excitation energy is deduced from a gamma-gamma coincidence experiment and previously published particle transfer data. 170 gamma-ray transitions are placed between 85 levels, confirming many of the previously established levels and some of the decay scheme. A level at 835.5 keV (J{sup {pi}} = 5{sup {minus}}, t{sub 1/2} < 10 ns) decays with substantial strength to both the ground state (7{sup {minus}}, 4.08 {times} 10{sup 10} yr) and the 122.9 keV isomer (1{sup {minus}}, 3.7 hr). The presence of this level guarantees the thermal equilibration of {sup 176}Lu{sup g,m} for temperatures greater than 3 {times} 10{sup 8} K and therefore during s-process nucleosynthesis. The resulting extreme temperature sensitivity of its effective half-life rules out the use of {sup 176}Lu as an s-process chronometer. The use of {sup 176}Lu to determine s-process temperatures is discussed. 30 refs., 11 figs., 3 tabs.
Date: November 1, 1990
Creator: Lesko, K.T.; Norman, E.B.; Larimer, R.M. & Sur, B.
Partner: UNT Libraries Government Documents Department

Angular momentum in subbarrier fusion

Description: We have measured the ratio of the isomer to ground-state yields of {sup 137}Ce produced in the fusion reactions {sup 128}Te({sup 12}C,3n), {sup 133}Cs({sup 7}Li,3n), {sup 136}Ba({sup 3}He,2n), {sup 136}Ba({sup 4}He,3n), and {sup 137}Ba({sup 3}He,3n), from energies above the Coulomb barrier to energies typically 20--30% below the barrier by observing the delayed x- and {gamma}-ray emission. We deduce the average angular momentum, {lt}J{gt}, from the measured isomer ratios with a statistical model. In the first three reactions we observe that the values of {lt}J{gt} exhibit the behavior predicted for low energies and the expected variation with the reduced mass of the entrance channel. We analyze these data and the associated cross sections with a barrier penetration model that includes the coupling of inelastic channels. Measurements of average angular momenta and cross sections made on other systems using the {gamma}-multiplicity and fission-fragment angular correlation techniques are then analyzed in a similar way with this model. The discrepancies with theory for the {gamma}-multiplicity data show correlations in cross section and angular momentum that suggest a valid model can be found. The measurements of angular momentum using the fission fragment angular correlation technique, however, do not appear reconcilable with the energy dependence of the cross sections. This systematic overview suggests, in particular, that our current understanding of the relationship of angular momentum and anisotropy in fission fragment angular correlations is incomplete. 26 refs.
Date: May 1, 1990
Creator: DiGregorio, D.E.; Lesko, K.T.; Harmon, B.A.; Norman, E.B.; Pouliot, J.; Sur, B. et al.
Partner: UNT Libraries Government Documents Department