The level structure of 158Er has been studied using the Gammasphere spectrometer via the 114Cd(48Ca, 4n) reaction at 215 MeV with both thin (self-supporting) and thick (backed) targets. The level scheme has been con-siderably extended with more than 200 new transitions and six new rotational structures, including two strongly coupled high -K bands. Configuration assignments for the new structures are based on their observed alignments, B(M1)/B(E2) ratios of reduced transition probabilities, excitation energies, and comparisons with neighboring nuclei and theoretical calculations. With increasing angular momentum, this nucleus exhibits Coriolis-induced alignments of both neutrons and protons before it then undergoes a rotation-induced transition from near-prolate collective rotation to a noncollective oblate configuration. This transition occurs via the mechanism of band termination around spin 45 h over bar in three rotational structures. Two distinct lifetime branches, consistent with the crossing of a collective "fast" rotational structure by an energetically favored "slow" terminating sequence, are confirmed for the positive-parity states, and similar behavior is established in the negative-parity states. Weak-intensity, high-energy transitions are observed to feed into the terminating states. At the highest spins,

Lifetimes or lifetime limits of a small number of excited states of the sulfur isotopes with mass numbers $A=35$, 36, 37, and 38 have been measured using the differential recoil-distance method. The isotopes of sulfur were populated in binary grazing reactions initiated by a beam of $^{36}\mathrm{S}$ ions of energy 225 MeV incident on a thin $^{208}\mathrm{Pb}$ target which was mounted in the Cologne plunger apparatus. The combination of the PRISMA magnetic spectrometer and an early implementation of the AGATA $\ensuremath{\gamma}$-ray tracking array was used to detect $\ensuremath{\gamma}$ rays in coincidence with projectile-like nuclear species. Lifetime measurements of populated states were measured within the range from about 1 to 100 ps. The number of states for which lifetime measurements or lifetime limits were possible was limited by statistics. For $^{35}\mathrm{S}$, the lifetime was determined for the first $1/{2}^{+}$ state at 1572 keV; the result is compared with a previous published lifetime value. The lifetime of the ${3}^{\ensuremath{-}}$ state of $^{36}\mathrm{S}$ at 4193 keV was determined and compared with earlier measurements. No previous lifetime information exists for the (${6}^{+}$) state at 6690 keV; a lifetime measurement with large associated error was made in the present work. For $^{37}\mathrm{S}$, the states for which lifetime limits were established were those at 646 keV with ${J}^{\ensuremath{\pi}}=3/{2}^{\ensuremath{-}}$ and at 2776 keV with ${J}^{\ensuremath{\pi}}=11/{2}^{\ensuremath{-}}$; there are no previously published lifetime values for excited states of $^{37}\mathrm{S}$. Finally, a lifetime limit was established for the ${J}^{\ensuremath{\pi}}=({6}^{+})$ state of $^{38}\mathrm{S}$ at 3675 keV; no lifetime information exists for this state in the literature. Measured lifetime values were compared with the results of state-of-the-art shell-model calculations based on the PSDPF, SDPF-U, and FSU effective interactions. In addition, nuclear magnetic-dipole and electric-quadrupole moments, branching ratios, mixing ratios, and electromagnetic transition rates, where available, have been compared with shell-model values. The current work suffers from poor statistics; nevertheless, lifetime values and limits have been possible, allowing a useful discussion of the ability of state-of-the-art shell-model calculations to reproduce the experimental results.

Lifetimes or lifetime limits of a small number of excited states of the sulfur isotopes with mass numbers A = 35, 36, 37, and 38 have been measured using the differential recoil-distance method. The isotopes of sulfur were populated in binary grazing reactions initiated by a beam of S-36 ions of energy 225 MeV incident on a thin Pb-208 target which was mounted in the Cologne plunger apparatus. The combination of the PRISMA magnetic spectrometer and an early implementation of the AGATA gamma-ray tracking array was used to detect gamma rays in coincidence with projectile-like nuclear species. Lifetime measurements of populated states were measured within the range from about 1 to 100 ps. The number of states for which lifetime measurements or lifetime limits were possible was limited by statistics. For S-35, the lifetime was determined for the first 1/2(+) state at 1572 keV; the result is compared with a previous published lifetime value. The lifetime of the 3(-) state of S-36 at 4193 keV was determined and compared with earlier measurements. No previous lifetime information exists for the (6(+)) state at 6690 keV; a lifetime measurement with large associated error was made in the present work. For S-37, the states for which lifetime limits were established were those at 646 keV with J(pi)=3/2(-) and at 2776 keV with J(pi)=11/2(-); there are no previously published lifetime values for excited states of 37S. Finally, a lifetime limit was established for the J(pi )= (6(+)) state of S-38 at 3675 keV; no lifetime information exists for this state in the literature. Measured lifetime values were compared with the results of state-of-the-art shell-model calculations based on the PSDPF, SDPF-U, and FSU effective interactions. In addition, nuclear magnetic-dipole and electric-quadrupole moments, branching ratios, mixing ratios, and electromagnetic transition rates, where available, have been compared with shell-model values. The current work suffers from poor statistics; nevertheless, lifetime values and limits have been possible, allowing a useful discussion of the ability of state-of-the-art shell-model calculations to reproduce the experimental results.

Lifetimes of excited states of the phosphorus isotopes P-33, 34, 35, 36(15) have been measured by using the differential recoil-distance method. The isotopes of phosphorus were populated in binary grazing reactions initiated by a beam of S-36 ions of energy 225 MeV incident on a thin Pb-208 target mounted in the Cologne plunger apparatus. The combination of the PRISMA magnetic spectrometer and an early implementation of the AGATA gamma-ray tracking array was used to detect gamma-rays in coincidence with projectile-like nuclear species. Lifetime measurements of populated states were made within the range from about 1 to 100 ps. The number of states for which lifetime measurements were possible was limited by statistics. For P-33, lifetime limits were determined for the first 3/2(+) and 5/2(+) states at 1431 and 1848 keV, respectively; the results are compared with previous published lifetime values. The lifetime of the first 2(+) state of P-34 at 429 keV was determined and compared with earlier measurements. For P-35, the states for which lifetimes, or lifetime limits, were determined were those at 2386, 3860, 4101, and 4493 keV, with J(pi) values of 3/2(+), 5/2(+), 7/2(1)(-) and 7/2(2)(-), respectively. There have been no previous published lifetimes for states in this nucleus. A lifetime was measured for the stretched pi(1f(7/2)) circle times nu(1f(7/2)) J(pi )= (7(+)) state of P-36 at 5212 keV and a lifetime limit was established for the stretched pi(1d(3/2)) circle times nu(1f(7/2)) J(pi )= (5(-)) state at 2030 keV. There are no previously published lifetimes for states of P-36. Measured lifetime values were compared with the results of state-of-the-art shell-model calculations based on the PSDPF effective interaction. In addition, measured branching ratios, published mixing ratios, and electromagnetic transition rates, where available, have been compared with shell-model values. In general, there is good agreement between experiment and the shell model; however there is evidence that the shell-model values of the M1 transition rates for the 3/2(1)(+)-> 1/2(+) (ground state) and 5/2(1)(+) -> 3/2(1)(+) transitions in P-33 underestimate the experimental values by a factor between 5 and 10. In P-35 there are some disagreements between experimental and shell-model values of branching ratios for the first and second excited 7/2(-) states. In particular, there is a serious disagreement for the decay characteristics of the second 7/2(-) state at 4493 keV, for which the shell-model counterpart lies at 4754 keV. In this case, the shell-model competing electromagnetic decay branches are dominated by E1 and M1 transitions.

Grocutt, L.; Chapman, R.; Bouhelal, M.; Haas, F.; Goasduff, A.; Smith, J.F. ; Courtin, S.; Bazzacco, D.; Braunroth, T.; Capponi, L.; Corradi, L.; Derkx, X.; Desesquelles, P.; Doncel, M.; Fioretto, E.; Gottardo, A.; Liberati, V.; Melon, B.; Mengoni, D.; Michelagnoli, C.; Mijatovi, T. ; Modamio, V.; Montagnoli, G.; Montanari, D.; Mulholland, K.F. ; Napoli, D.R.; Petrache, C.; Pipidis, A.; Recchia, F.; Sahin, E.; Singh, P.P.; Stefanini, A.M.; Szilner, S.; Valiente-Dobón, J.J.

Lifetimes of first 4+ and 6+ states have been measured in neutron-rich isotopes of Zr, Mo, Ru and Pd using the recoil distance Doppler shift method at GANIL. The nuclei were produced through a fusion-fission reaction in inverse kinematics. The fission fragments were fully identified in the large-acceptance VAMOS spectrometer and γ-rays were detected in coincidence with the EXOGAM germanium array. Lifetimes of excited states in the range of 1–100 ps were measured with the Cologne plunger. Preliminary lifetime results are presented as well as a discussion on the evolution of the collectivity in this region.

This board will be part of the upgrade for the new electronics for the EXOGAM2 (HP-Ge detector array) and NEDA (BC501A-based neutron detector array), therefore it was necessary to deal with the problem of providing a sampling card with high resolution for new gamma spectroscopy experiments while sampling at very high rates, with a broad bandwidth in order to preserve the shape for further analysis. Pulse shape analysis is of paramount importance in neutron detectors, such as NEDA, based on scintillators that are sensitive to γ-rays as well. High resolution and high speed are often two parameters which conform a trade-off and it is hard to achieve both simultaneously. The aforementioned constraints and the urge of building new sampling electronics to improve the signal analysis in nuclear physics experiments, led to the development of this FADC mezzanine This involves sampling rates up to 250 Msps preserving a high resolution of 11.3 effective bits in order to satisfy the experiment demands. In this work is described the design and the test bench proposed for a proper high speed ADC characterization system and the results obtained up to now.

LNL Annual Report Nuclear Physics 1 1IFIC, Valencia, Spain. 2INFN, Sezione di Napoli, Napoli, Italy. 3Faculty of Physics, Warsaw University of Technology, Warsaw, Poland. 4Heavy Ion Laboratory, University of Warsaw, Warsaw, Poland. 5INFN, Laboratori Nazionali di Legnaro, Legnaro (Padova), Italy. 6Uppsala University, Uppsala, Sweden. 7RIKEN Nishina Center, Wako-shi, Japan. 8INFN, Sezione di Padova, Padova, Italy. 9GANIL, Caen, France. 10University of Valencia, Valencia, Spain. 11Istanbul Sabahattin Zaim Üniversitesi, Istanbul, Turkey. 12Nigde Üniversitesi, Nigde, Turkey.

A study of the dimensions and performance of a single detector of the future neutron detector array NEDA was performed by means of Monte Carlo simulations, using GEANT4. Two different liquid scintillators were evaluated: the hydrogen based BC501A and the deuterated BC537. The efficiency and the probability that one neutron will trigger a signal in more than one detector were investigated as a function of the detector size. The simulations were validated comparing the results to experimental measurements performed with two existing neutron detectors, with different geometries, based on the liquid scintillator BC501.

High-spin states in 187 Pt have been studied by means of γ-ray spectroscopy techniques. Known bands have been significantly extended and new bands have been found. The band structures are discussed in the framework of the cranking model and negative-parity states are compared with calculations performed with a semi-microscopic axial-rotor plus one-quasiparticle coupling model. Shape coexistence is observed from low excitation energy.

1 INFN, Lab. Nazionali di Legnaro, Legnaro (Padova), Italy. 2 INFN and Dip. di Scienze Fisiche, Università di Napoli, Napoli, Italy. 3 Faculty of Physics, Warsaw University of Technology, Warszawa, Poland. 4 Heavy Ion Lab., University of Warsaw, Warszawa, Poland. 5 IFIC-CSIC, Universitat de Valencia, Valencia, Spain. 6Department of Physics, Istanbul University, Istanbul, Turkey. 7 Nigde Universitesi, Fen-Edebiyat Falkültesi, Fizik Bölümü, Nigde, Turkey. 8 Dept. of Physics and Astronomy, Uppsala University, Uppsala, Sweden. 9 Dept. of Physics, University of York, Heslington (York), UK.

The N similar to 90 region of the nuclear chart has featured prominently as the spectroscopy of nuclei at extreme spin has progressed. This talk will present recent discoveries from investigations of high spin behavior in the N similar to 90 Er, Tm and Yb nuclei utilizing the Gammasphere gamma-ray spectrometer. In particular it will include discussion of the beautiful shape evolution and coexistence observed in these nuclei along with the identification of a remarkable new family of band structures. The latter are very weakly populated rotational sequences with high moment of inertia that bypass the classic terminating configurations near spin 40-50 (h) over bar, marking a return to collectivity that extends discrete gamma-ray spectroscopy to well over 60 (h) over bar. Establishing the nature of the yrast states in these nuclei beyond the oblate band-termination states has been a major goal for the past two decades. Cranking calculations suggest that these new structures most likely represent stable triaxial strongly deformed bands that lie in a valley of favored shell energy in deformation and particle-number space. (Less)

M.A. Riley, A. Aguilar, A.O. Evans, D.J. Hartley, K. Lagergren J. Ollier, E.S. Paul, A. Pipidis, J. Simpson, C. Teal, P.J. Twin X. Wang, D.E. Appelbe, D.B. Campbell, M.P. Carpenter, R.M. Clark M. Cromaz , I.G. Darby, P. Fallon , U. Garg, R.V.F. Janssens, D.T. Joss F.G. Kondev, T. Lauritsen, I.Y. Lee , C.J. Lister, A.O. Macchiavelli P.J. Nolan, M. Petri, S.V. Rigby, J. Thompson, C. Unsworth D. Ward , S. Zhu, I. Ragnarsson

The Cd-114(Ca-48, 6n gamma) reaction at 215 MeV has been investigated using the Gammasphere spectrometer to study the high-spin structure of the nucleus Er-156(68)88. Many new transitions have been established along with 68 definitive spin-parity level assignments from a high-fold angular-distribution analysis. In addition, absolute B(M 1) and B(E 1) strengths have been inferred from measured gamma-ray branching ratios. Strong B(E 1) strength (10(-3) W.u.) is discussed in terms of possible octupole collectivity at low spin. At high spin, this nucleus undergoes a Coriolis-induced shape transition from a prolate state of collective rotation to a noncollective, triaxial-oblate configuration. The yrast positive-parity structure ultimately terminates in an energetically favored oblate state at I-pi = 42(+). Several weak high-energy gamma-ray transitions have been discovered that feed this favored state. State-of-the-art cranked Nilsson-Strutinsky calculations are used to interpret the high-spin behavior of Er-156 and comparisons are made with other N = 88 isotones.

A high-spin rotational band was observed in the N=90 nucleus Yb-160 with moment of inertia and decay characteristics very similar to recently discovered sequences in Er-157,Er-158. These latter structures were discussed in terms of strongly deformed triaxial bands. Detailed cranked Nilsson-Strutinsky calculations were performed that predict that well-deformed triaxial structures are also expected at high spin in Yb-160. Within this interpretation the observed discontinuity in the dynamic moment of inertia around h omega=0.40-0.45 MeV can be explained as a crossing between i(13/2) neutron levels.

A high-spin rotational band has been observed in the N=90 nucleus 160Yb with very similar moment of inertia and decay characteristics to recently discovered sequences in 157,158Er which have been discussed in terms of strongly deformed triaxial structures. Well-deformed triaxial shapes are indeed expected in 160Yb at high spin and detailed cranked Nilsson-Strutinsky calculations have been performed from which possible configurations are discussed.

High‐spin states in 187Pt have been studied by means of γ‐ray spectroscopy techniques. Known bands have been significantly extended and new bands have been found. The band structures are briefly discussed.

A new frontier of discrete-line gamma-ray spectroscopy at ultrahigh spin has been opened in the rare-earth nuclei (157,158) Er. Four rotational structures, displaying high moments of inertia, have been identified, which extend up to spin approximately 65 variant Planck's over 2pi and bypass the band-terminating states in these nuclei which occur at approximately 45 variant Planck's over 2pi. Cranked Nilsson-Strutinsky calculations suggest that these structures arise from well-deformed triaxial configurations that lie in a valley of favored shell energy which also includes the triaxial strongly deformed bands in (161-167) Lu.