Nuclear photonics at ultra-high counting rates and higher multipole excitations

Next-generation gamma beams beams from laser Compton-backscattering facilities like ELI-NP (Bucharest)] or MEGa-Ray (Livermore) will drastically exceed the photon flux presently available at existing facilities, reaching or even exceeding 10^13 gamma/sec. The beam structure as presently foreseen for MEGa-Ray and ELI-NP builds upon a structure of macro-pulses (~120 Hz) for the electron beam, accelerated with X-band technology at 11.5 GHz, resulting in a micro structure of 87 ps distance between the electron pulses acting as mirrors for a counterpropagating intense laser. In total each 8.3 ms a gamma pulse series with a duration of about 100 ns will impinge on the target, resulting in an instantaneous photon flux of about 10^18 gamma/s, thus introducing major challenges in view of pile-up. Novel gamma optics will be applied to monochromatize the gamma beam to ultimately Delta E/E~10^-6. Thus level-selective spectroscopy of higher multipole excitations will become accessible with good contrast for the first time. Fast responding gamma detectors, e.g. based on advanced scintillator technology (e.g. LaBr3(Ce)) allow for measurements with count rates as high as 10^6-10^7 gamma/s without significant drop of performance. Data handling adapted to the beam conditions could be performed by fast digitizing electronics, able to sample data traces during the micro-pulse duration, while the subsequent macro-pulse gap of ca. 8 ms leaves ample time for data readout. A ball of LaBr3 detectors with digital readout appears to best suited for this novel type of nuclear photonics at ultra-high counting rates.Comment: 4 pages, 1 figure, 1 tabl

In-beam fast-timing measurements in 103,105,107Cd

Fast-timing measurements were performed recently in the region of the medium-mass 103,105,107Cd isotopes, produced in fusion evaporation reactions. Emitted gamma-rays were detected by eight HPGe and five LaBr3:Ce detectors working in coincidence. Results on new and re-evaluated half-lives are discussed within a systematic of transition rates. The $7/2_1^+$ states in 103,105,107Cd are interpreted as arising from a single-particle excitation. The half-life analysis of the $11/2_1^-$ states in 103,105,107Cd shows no change in the single-particle transition strength as a function of the neutron number

Half-life of the I Π = 4 - intruder state in 34 P: M 2 transition strengths approaching the island of inversion

The half-life of the 2305-keV, I?=4 (-) intruder state in 34P has been measured as t 1/2=2.0(1) ns using ?-ray coincidence, fast-timing techniques with the Bucharest HPGe and LaBr 3:Ce detector array. Excited states in 34P were populated using the 18O (18O,pn )34P fusion-evaporation reaction at a beam energy of 36 MeV. Reduced transition probabilities have been calculated for different values of the M2/E3 mixing ratio, ? E3/M2, and compared with shell-model estimates. For small values of the mixing ratio, the B(M2) value was found to be consistent with similar transitions associated with the occupation of neutron f 7/2 configurations in this mass region. � 2012 American Physical Society

g factors of coexisting isomeric states in Pb-188

The $g$ factors of the ${12}^{+}$, {11}^{\ensuremath{-}}, and {8}^{\ensuremath{-}} isomeric states in $^{188}\mathrm{Pb}$ were measured using the time-differential perturbed angular distribution method as g({12}^{+})=\ensuremath{-}0.179(6), g({11}^{\ensuremath{-}})=+1.03(3), and g({8}^{\ensuremath{-}})=\ensuremath{-}0.037(7). The $g$ factor of the ${12}^{+}$ state follows the observed slight down-sloping evolution of the $g$ factors of the ${i}_{13/2}^{2}$ neutron spherical states with decreasing $N$. The $g$ factors of the {11}^{\ensuremath{-}} and {8}^{\ensuremath{-}} isomers proposed as oblate and prolate deformed states, respectively, were interpreted within the rotational model, using calculated and empirical $g$ factor values for the involved single-particle orbitals

Transition probabilities in the X(5) candidate 122^{122}Ba

To investigate the possible X(5) character of 122Ba, suggested by the ground state band energy pattern, the lifetimes of the lowest yrast states of 122Ba have been measured, via the Recoil Distance Doppler-Shift method. The relevant levels have been populated by using the 108Cd(16O,2n)122Ba and the 112Sn(13C,3n)122Ba reactions. The B(E2) values deduced in the present work are compared to the predictions of the X(5) model and to calculations performed in the framework of the IBA-1 and IBA-2 models

Synthesis of Multiwall Carbon Nanotubes by Inductive Heating CCVD

The CCVD syntheses of MWCNTs from acetylene on Fe:Co:CaCO 3 and Fe:Co:CaO were performed using two different methods of heating: outer furnace and inductive heating. The comparative analysis of the MWCNTs obtained by the two methods show that the tubes grown in inductive heating have smaller diameters (5-25 nm), with fewer walls and aspect ratio of the order of hundreds. The ratio of outer to inner diameter (od/id) is ranging between 2 and 2.5. Inductively assisted CCVD is a very attractive method because of the major advantages that it presents, like low energetic consumption, thinner, well crystallized and more uniform tubes

Electromagnetic transition rates in the Ν = 80 nucleus 138/58Ce

The half-life of the I?=6+ yrast state at Ex=2294 keV in 138Ce has been measured as T1/2=880(19) ps using the fast-timing ?-ray coincidence method with a mixed LaBr3(Ce)- HPGe array. The excited states in 138Ce have been populated by the 130Te(12C,4n) fusion-evaporation reaction at an incident beam energy of 56 MeV. The extracted B(E2;61+?41+)=0.101(24) W.u. value is compared with the predictions of truncated basis shell model calculations and with the systematics of the region. This shows an anomalous behavior compared to the neighboring isotonic and isotopic chains. Half-lives for the yrast 5-, 11+ and 14+ states in 138Ce have also been determined in this work. � 2013 American Physical Society

Fast-timing measurements in 95,96Mo

Half-lives of the 19/2+ and 21/2+ states in 95Mo and of the 8+ and 10+ states in 96Mo were measured. Matrix elements for yrast transitions in 95Mo and 96Mo are discussed.Comment: Proceedings of XIX International School on Nuclear Physics, Neutron Physics and Applications, Varna, Bulgaria, 2011, 5 pages, 6 figure