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Nuclear Physics Tuesday HK 15 Poster Session: Nuclear and Particle Astrophysics Time: Tuesday 13:30–15:30 Room: Foyer HK 15.1 Tue 13:30 Foyer Tritium related components of the KATRIN Experiment — •Frank Eichelhardt for the KATRIN collaboration — Universität Karlsruhe, Institut für exp. Kernphysik The KArlsruhe TRItium Neutrino experiment investigates spectroscopically the electron spectrum from tritium β decay 3 H → 3 He+e − +¯νe near its kinematical endpoint of 18.6keV. With a strong windowless molecular gaseous Tritium source (WGTS) and a high resolution electrostatic filter of unprecedented energy resolution, KATRIN will allow a model-independent measurement of neutrino masses with an expected sensitivity of 0.2eV (90% CL). The T2 injection rate into the WGTS is up to 0.4mbarls −1 while the maximum allowed flow rate into the pre-spectrometer is 2.5·10 −11 mbarls −1 . The necessary suppression of at least 10 10 has to be provided by differential pumping sections (DPS) and cryogenic pumping systems (CPS), which are located between source and spectrometer. This report focuses on the present status of the design of tritium related parts of KATRIN including the WGTS, DPS and CPS as well as on ongoing prototype measurements. Funded in part by the German BMBF Förderschwerpunkt Astroteilchenphysik under 05CK1VK1/7 and 05CK1UM1/5. HK 15.2 Tue 13:30 Foyer Investigations of trapping conditions in-between the MAC-E- Filters of the KATRIN experiment. — •Kathrin Essig for the KATRIN collaboration — Helmholtz-Institut für Strahlen- und Kernphysik, Rheinische Friedrich-Wilhelms-Universität, D-53115 Bonn The KArlsruhe TRItium Neutrino experiment KATRIN[1] aims to determine the absolute mass of the electron antineutrino by measuring the endpoint region of the tritium-β-spectrum with sub-eV sensitivity. The KATRIN setup consists of two MAC-E-Filter (Magnetic Adiabatic Collimation followed by Electrostatic Filter) spectrometers, one low resolution pre-spectrometer followed by a high resolution main-spectrometer. The electric and magnetic field configurations of this lined up spectrometers yield to penning trap conditions for electrons. These trapped electrons are thought of as a major source of background events, hence their number has to be minimized. The aim of this talk is to discuss the trapping conditions of electrons based on computer simulations and to present methods to remove them or to minimize their storage time. Therefore cooling processes like synchrotron radiation and residual gas interactions due to elastic and inelastic scattering or ionization have been studied. Besides cooling there is still the option of an active removal of stored particles by the pre-spectrometer’s electric dipole fields. Supported by the BMBF under contract 05CK2PD1/5. [1] A. Osipowicz et al. (KATRIN coll.), hep-ex/0109033 HK 15.3 Tue 13:30 Foyer Background measurements with the Mainz Neutrinomassexperiment — •Björn Flatt for the KATRIN collaboration — Johannes Gutenberg Universität, 55099 Mainz After the completion of the tritium runs with the Mainz Neutrinomassexperiment in 2001 the spectrometer was devoted to background studies in perspective of the successor experiment KATRIN (KArlsruhe TRItium Neutrino experiment). These studies include the modifications of the electrode systems and measurements with artificial background sources, e.g. X-rays induced and decay of 83 Kr in the spectrometer and aim to understand the background of MAC-E-Filters (Magnetic Adiabatic Collimation and Electrostatic Filter) by stored particles and by electrons from the electrodes and the walls induced by cosmic rays or radioactive impurities. In the talk the results of the measurements and the implications for KATRIN will be shown. Supported by BMBF Förderschwerpunkt Astroteilchenphysik under Nr. 05CK1VK1/7 and 05CK1UM1/5. HK 15.4 Tue 13:30 Foyer Beam induced background at the LUNA 400 kV underground accelerator facility — •Daniel Bemmerer for the LUNA collaboration — Institut für Atomare Physik und Fachdidaktik, Technische Universität Berlin, Germany At the LUNA 400 kV accelerator facility [1] at Laboratori Nazionali del Gran Sasso, Italy, the background due to cosmic ray induced muons is reduced by six orders of magnitude due to the rock overburden. In order to study radiative-capture cross sections at astrophysically relevant energies, also the background induced by the ion beam itself has to be reduced. Currently, the 14 N(p,γ) 15 O reaction is being investigated by the LUNA collaboration using a windowless gas target system [2]. In preparation for these studies, background from the 2 D(p,γ) 3 He, 13 C(p,γ) 14 N and other reactions has been identified, localized and significantly reduced. [1] A. Formicola et al., Nucl. Inst. Meth. A 507 (2003) 609-616. [2] C. Casella et al., Nucl. Inst. Meth. A 489 (2002), 160-169. HK 15.5 Tue 13:30 Foyer GENIUS Test Facility Started in GRAN SASSO. — •Irina Krivosheina, Hans Volker Klapdor-Kleingrothaus, Oleg Chkvorets, Claudia Tomei, and Herbert Strecker — Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, D-69117 HEIDELBERG, GERMANY The first four naked high purity Germanium detectors were installed successfully in liquid nitrogen in the GENIUS-Test-Facility (GENIUS- TF) in the GRAN SASSO Underground Laboratory on May 5, 2003. This is the first time ever that this novel technique aiming at extreme background reduction in search for rare decays is going to be tested underground. First operational parameters are presented. HK 15.6 Tue 13:30 Foyer Metal loaded liquid scintillators — •Christian Buck, F.X. Hartmann, D. Motta, S. Schönert, and U. Schwan — Max Planck Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg The development of metal based liquid scintillator systems is important towards the next generation low energy solar neutrino, reactor antineutrino and double-beta decay experiments. One approach to develop stable scintillator systems containing In (solar neutrinos), Gd (reactor neutrinos) or Nd (neutrinoless double-beta decay) is the use of metal beta-diketonate complexes. The optical properties of these metal loaded scintillators will be reported. Furthermore the energy transfer between the various components in a liquid scintillator will be discussed. The In-system was investigated in most detail. Results of a highly loaded In-scintillator used in a prototype detector at the underground laboratory in Gran Sasso, Italy will be presented. HK 15.7 Tue 13:30 Foyer A Prediction of Cosmic Rays from Nearby Black Holes’ Activity — •Oana Tascau, Peter Biermann, and Ralf Ulrich — MPIFR The Falcke Biermann model of a jet disk which explain the radio to infrared spectrum of the black hole camdidate was apply for many relativistic jet systems and in this pariculary case for the radio emission at the base of the jet of the black holes candidates within 50 Mpcs. The data from AGASA and HiRes were fitted showing a possible difference in spectrum between north and south.
Nuclear Physics Tuesday HK 16 Nuclear Structure/Spectroscopy II Time: Tuesday 15:30–18:30 Room: A Group Report HK 16.1 Tue 15:30 A The neutron-rich Na and Mg isotopes — •Heiko Scheit for the REX-MINIBALL collaboration — Max-Planck-Institut für Kernphysik, Heidelberg More than 30 years after the first observation of the neutron-rich Na isotopes (at ISOLDE) the unusual properties of the Na and Mg isotopes in the vicinity of the N = 20 shell closure are still not fully understood. The existing experimental data are sparse and sometimes even contradictory, e.g. the measured B(E2; 0gs → 2 + 1 ) values of the even-even isotopes 30,32 Mg deviate by as much as a factor of two from each other[1-3]. The recently commissioned REX accelerator for exotic nuclei at ISOLDE together with the modern HPGe array MINIBALL offers the opportunity to study the collective and single particle properties of these nuclei with standard nuclear physics tools such as (sub Coulomb barrier) Coulomb excitation and single-nucleon transfer reactions in inverse kinematics. After giving a short introduction of REX and MINIBALL I will summarize the current status of research on the neutron-rich Na and Mg isotopes with special emphasis on our new results from REX-ISOLDE with the MINIBALL array. [1] T. Motobayashi et al., Phys. Lett. B346 , 9 (1995). [2] B.V. Pritychenko et al., Phys. Lett. B461 , 322 (1999). [3] V. Chiste et al., Phys. Lett. B514, 233 (2001). Group Report HK 16.2 Tue 16:00 A New Insights into the Fission Barrier Landscape of Light Actinides ∗ — •P.G. Thirolf 1 , M. Csatlós 2 , T. Faestermann 3 , G. Graw 1 , D. Habs 1 , J. Gulyás 2 , M.N. Harakeh 4 , R. Hertenberger 1 , M. Hegelich 1 , M. Hunyadi 2 , A. Krasznahorkay 2 , H.J. Maier 1 , Z. Máté 2 , J. Szerypo 1 , and H.-F. Wirth 1 — 1 Ludwig-Maximilians-Universität München — 2 Inst. of Nucl. Res. of the Hung. Acad. of Sci., Debrecen — 3 Technische Universität München — 4 Kernfysisch Versneller Instituut, Groningen Transmission resonance spectroscopy in 236 U has been performed with high resolution, resulting in the identification of rotational band structures corresponding to hyperdeformed configurations. From the level density an excitation energy of the ground state in the third minimum of 3.30±0.4 MeV could be determined [1], thus confirming the existence of a rather deep third minimum, similar to our previous findings in 234 U [2]. The excitation energy of the lowest hyperdeformed transmission resonance and the energy dependence of the fission isomer population probability enabled the determination of the height of the inner fission barrier EA =5.15 ±0.20 MeV. This significant lowering of the inner barrier height compared to previously believed values in the presence of a deep third well may be a general feature in the light actinides, giving rise to the existence of short-lived fission isomers. First experiments searching for ps shape isomers in light uranium isotopes will be presented. [1] M. Csatlós et al., submitted to Phys. Lett. [2] A. Krasznahorkay et al., Phys. Lett. B461 (1999) 15. ∗ Supported by the DFG and Maier-Leibnitz-Laboratorium, Garching HK 16.3 Tue 16:30 A From spherical 34Si to deformed 32Mg: static moments of neutron rich Al-isotopes — •Pieter Himpe 1 , Gerda Neyens 1 , Dana Borremans 1 , Nele Vermeulen 1 , Deyan Yordanov 1 , Ketel Turzo 1 , Stephen Mallion 1 , Nadya Smirnova 2 , Georgi Georgiev 3 , Jean-Michel Daugas 4 , Victor Meot 4 , Iolanda Matea 3 , Dimiter Balabanski 5 , Yu.E. Penionzhkevich 6 , M Staniou 3 , Francois De Oliveira Santos 3 , Gilles de France 3 , and Magda Kowalska 7 — 1 Dept. Natuurkunde, KULeuven — 2 Ghent University — 3 GANIL — 4 Bruyeres le Chatel — 5 St. Kliments Ohridsky University of Sofia — 6 JINR-Dubna — 7 Inst. fur Physik, Univ. Mainz In 1975 Thibault et al. discovered that 31-32Na are much stronger bound than expected. Today we know that this is due to low lying intruder states in this region, called ’the island of inversion’. The ground state of 34Si (Z=14) is not influenced by the intruder states, while 32Mg (Z=12), on the contrary, is a well deformed nucleus. Using the NMR technique on polarised Al nuclei we measured the gfactor of 32-33Al, nuclei in between 34Si and 32Mg, using a polarized fragment beam from the LISE separator at GANIL. These results give an indication that the ground state of 32Al is normal and that the 2p-2h intruder state influences the ground state of 33Al. In the future we will measure the quadrupole moment of these nuclei to get more insight on their deformation. HK 16.4 Tue 16:45 A Optical polarization and β-asymmetry measurement on neutron-rich magnesium isotopes — •M. KOWALSKA 1 , K. BLAUM 2 , D. BORREMANS 3 , S. GHEYSEN 3 , P. HIMPE 3 , S. MALLION 3 , P. LIEVENS 3 , R. NEUGART 1 , G. NEYENS 3 , N. VERMEULEN 3 , and D. YORDANOV 3 — 1 University of Mainz, Germany — 2 ISOLDE-CERN, Switzerland — 3 K.U. Leuven, Belgium The properties of neutron-rich Mg isotopes around N = 20 are very much influenced by intruder states from the f7/2 shell entering into the sp shell. This “island of inversion” is a challenge for nuclear shell-model calculations, and measurements of magnetic dipole and electric quadrupole moments are important as an experimental basis. For this purpose we have recently tested the conditions of β-NMR spectroscopy on short-lived Mg isotopes. 60 keV ion beams of 29 Mg, 31 Mg and 33 Mg, produced by the RILIS ion source at ISOLDE-CERN, were polarized by collinear optical pumping with frequency-doubled laser light at 280 nm and were implanted into a cubic MgO crystal. Observation of the β-decay asymmetry as a function of the Doppler-tuned optical excitation frequency reveals the hyperfine structure of 29 Mg and 31 Mg in the 3s 2 S1/2 → 3p 2 P3/2 resonance transition. Preliminary information from these measurements about the involved spins and magnetic moments will be discussed. The observed asymmetries of up to 6% will allow us to perform accurate β-NMR measurements, from which g-factors and quadrupole moments can be deduced. HK 16.5 Tue 17:00 A Shell-Model Description of Monopole Shifts in Neutron-Rich Cu Nuclei — •Anneleen De Maesschalck, Nadya A. Smirnova, Annelies Van Dyck, and Kris Heyde — Institute for Subatomic and Radiation Physics, Ghent University, Proeftuinstraat 86, 9000 Gent, Belgium The nuclear mean field and its corresponding magic numbers have been determined predominantly by the study of nuclei in or near the valley of β-stability. When moving out of this valley towards proton- or neutronrich nuclei, changes in the nuclear mean field are expected to appear. We have studied changes in the nuclear mean field for neutron-rich nuclei with shell model techniques. The main contribution to the change comes from the monopole part of the effective two-body proton-neutron interaction. We have investigated low-lying states in odd-A Cu nuclei, for which recent experimental data have been obtained [1], [2], [3]. Both schematic and realistic (obtained with a G-matrix [4]) forces have been used, and the monopole shifts obtained with these forces are compared with the results from large-scale shell model calculations, where the same realistic force has been used; in this way, two-body correlations beyond the mean field are brought into account. [1] S. Franchoo et al., Phys. Rev. C 64 (2001), 054308. [2] J. Van Roosbroeck et al., submitted. [3] N.A. Smirnova, A. De Maesschalck, A. Van Dyck, K. Heyde, submitted. [4] M. Hjorth-Jensen, T.T.S. Kuo, E. Osnes, Phys. Rep. 261 (1995) 125. HK 16.6 Tue 17:15 A A measure for γ-deformation in heavy nuclei — •C. Scholl, V. Werner, and P. von Brentano — Institut für Kernphysik, Universität zu Köln A way to measure the γ-deformation of a nucleus is found by analysis of shape invariants. While β and γ are deformation parameters in the geometrical model, they are not always easy to define in all cases, e.g., in vibrational nuclei. The shape invariants K3 and K4 are connected to effective β- and γ- deformation parameters by simple formulas. In general, they are given by huge sums over matrix elements. Nevertheless, introducing the Q-phonon scheme and its selection rules, it was shown [1] that a good approximation to K4 can be given involving only two B(E2) values in the ground state band. Using the same approximation for K3 one can identify this quantity with the quadrupole moment of the first
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