380 research outputs found
Untersuchung des Zerfalls der Dipol-Riesenresonanz in heissen, schnell rotierenden Dysprosium-Compoundkernen
No full textSIGLEAvailable from TIB Hannover: MA 7882 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman
From laser particle acceleration to the synthesis of extremely neutron rich isotopes via the novel fission-fusion mechanism
No full textSpectroscopy of 232U in the (p, t) reaction: Experimental data
No full textThe excitation spectra in the deformed nucleus 232U have been studied by means of the (p, t) reaction, using the Q3D spectrograph facility at the Munich Tandem accelerator. The angular distributions of tritons were measured for 162 excitations seen in the triton spectra up to 3.25 MeV. 0+ assignments are made for 13 excited states by comparison of experimental angular distributions with the calculated ones using the CHUCK3 code. Assignments up to spin 6+are made for other states
A Ge detector array for radioactive ion beam
No full textDedicated Ge-detector arrays are being developed for the investigation of rare gamma decays with low gamma -ray multiplicity at the upcoming radioactive ion beam facilities. These arrays are optimized for the high full-energy peak efficiency and angular resolution of the gamma -ray detection needed for a proper Doppler correction of the gamma -rays emitted by fast recoiling nuclei. MINIBALL will consist of 40 six-fold segmented, encapsulated Ge detectors which are clustered in eight cryostats with three detectors each and four cryostats with Four detectors, respectively. The individual components the six-fold segmented Ge detector, the cryostats, the fast preamplifier, the digital pulse-processing electronics and the mechanical frame - and their properties are described. The results of test measurements with the first MINIBALL cluster detector using a Cs-137 source and the in-beam reaction D(Cl-37, n) Ar-38 are presented. It is shown that from pulse-shape analysis of the events within a detector segment the effective granularity of the MINIBALL array can be enhanced from 240 to similar to 4000. The specifications of MINIBALL are compiled on the basis of experimental data. First results with a 12-fold segmented, encapsulated detector are discussed with respect to the feasibility of future gamma -ray tracking arrays
To the nature of 0+ excitations in deformed nuclei of actinides
No full textThe excitation spectra in the deformed nucleus 232U have been studied by means of the (p, t) reaction. 0+ assignments for 13 excited states and up to spin 6+ for other states are made from the angular distributions of tritons and the coupled-channel approximation analysis. Sequences of states are selected which can be treated as rotational bands. Moments of inertia have been derived from these sequences, whose values may be considered as evidence of the two- or one-phonon nature of these 0+ excitations. Experimental data are compared with interacting boson model (IBM) and quasiparticle-phonon model (QPM) calculations
Perspectives for Highly-Sensitive PET-Based Medical Imaging Using β+γ Coincidences
No full textBy employing the triple coincidence between the γ trajectory intersections from β+ decaying isotopes emitting a third, prompt, photon (γ-PET technique), sub-millimeter spatial resolution can be reached in 3 dimensions for the localization of a point source with a reduced requirement of reconstructed intersections per voxel compared to a conventional PET reconstruction analysis. Results of a Monte-Carlo simulation and image reconstruction study are presented in order to characterize the potential of this technique
Towards a direct transition energy measurement of the lowest nuclear excitation in
No full textThe isomeric first excited state of the isotope 229Th exhibits the lowest nuclear excitation energy in the whole landscape of known atomic nuclei. For a long time this energy was reported in the literature as 3.5(5) eV, however, a new experiment corrected this energy to 7.6(5) eV, corresponding to a UV transition wavelength of 163(11) nm. The expected isomeric lifetime is τ = 3-5 hours, leading to an extremely sharp relative linewidth of ΔE/E ≈ 10−20, 5-6 orders of magnitude smaller than typical atomic relative linewidths. For an adequately chosen electronic state, the frequency of the nuclear ground-state transition will be independent from influences of external fields in the framework of the linear Zeeman and quadratic Stark effect, rendering 229mTh a candidate for a reference of an optical clock with very high accuracy [1]. Moreover, in the literature speculations about a potentially enhanced sensitivity of the ground-state transition of 229mTh for eventual time-dependent variations of fundamental constants (e.g. fine structure constant α) can be found [3,4]. We report on our experimental activities that aim at a direct identification of the UV fluorescence of the ground-state transition energy of 229mTh. A further goal is to improve the accuracy of the ground-state transition energy as a prerequisite for a laser-based optical control of this nuclear excited state, allowing to build a bridge between atomic and nuclear physics and open new perspectives for metrological as well as fundamental studies.sponsorship: We acknowledge fruitful discussions with T.W. H ̈ansch, T. U
dem, D. Habs, E. Haettner, P. Hilz and J. Schreiber. This work was supported by the DFG Cluster of Excellence Munich-Centre for Advanced Photonics (MAP) and by DFG (TH956/3-1).status: Publishe
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