Svenskt kärnfysikermöte och SFAIR årsmöte 2014

10 Nov 2014, 13:00 → 12 Nov 2014, 16:40 Europe/Stockholm

Ångströmlaboratoriet, Uppsala universitet

Christian Forssén (Chalmers University of Technology), Tord Johansson (Uppsala University)

SFAIR årsmöte 10-11 november (lunch till lunch) Svenskt kärnfysikermöte XXXIV 11-12 november (start vid lunch)

Monday, 10 November ¶

13:30 → 15:45 SFAIR¶

SFAIR årsmöte 2014 (rum 80101)

13:30 Welcome¶

Speaker: Prof. Tord Johansson (Uppsala University)

13:35 FAIR and RFI¶

Speaker: Catarina Sahlberg (VR)

Slides CSahlberg_SFAIRpresentation.pdf

14:10 FAIR operation costs¶

Speaker: Prof. Örjan Skeppstedt (Department of Physics, Stockholm University)

Slides FAIR_Op_cost_SFAIR_ÖS_141110.pdf

14:35 A gas target for CRYRING¶

Speaker: H. Schmidt (SU)

Slides Schmidt_SFAIR_141110.pdf

15:00 Proton magnetic moment and electron mass meaurements¶

Speaker: Wolfgang Quint (GSI)

Slides 20141110_SFAIR_Quint.pdf

15:45 → 16:15 Coffee

16:15 → 18:05 SFAIR¶

SFAIR årsmöte 2014 (rum 80101)

16:15 A Penning Trap for spectroscopy of highly charged ions¶

Speaker: Dr Andreas Solders (Uppsala University)

Slides Solders_Penning__trap_spec_HCI.pdf

16:40 NUSTAR Day-0 and Day-1 experiments¶

Speaker: Nasser Kalantar-Nayestanaki (KVI, Groningen)

Slides NUSTAR_Kalantar.pdf

17:25 NUSTAR Administration¶

Speaker: Alexander Herlert (FAIR, Darmstadt)

Tuesday, 11 November ¶

09:00 → 10:40 SFAIR¶

SFAIR årsmöte 2014 (rum 80101)

09:00 Conceptual design of the high-resolution DESPEC Ge Array Spectrometer (DEGAS)¶

The DESPEC (Decay SPECtroscopy) experiment, which is part of the NUSTAR programme (NU- clear Structure, Astrophysics and Reactions) at FAIR (Facility for Antiproton and Ion Research) in GSI, will be devoted to investigate nuclear structure by means of beta decay and isomeric decay. It consists of an implantation detector (AIDA), a high-resolution Ge array and a neutron detector (MONSTER). In the talk, the results of Monte Carlo simulations for the conceptual design of the high-resolution Ge array (DEGAS) will be presented. The simulations show how the best approach for a system with good performances is obtained coupling the AGATA type triple cluster detectors with EUROBALL cluster detectors in a compact geometry around the implantation plane.

Speaker: Dr Maria Doncel (Royal Institute of Technology (KTH))

Slides DONCEL_SFAIR_2014.pdf

09:25 Super FRS in-kind¶

Speaker: Andreas Heinz (Chalmers)

Slides Heinz_SFAIR_2014.pdf

09:50 CALIFA for R3B - a status report¶

Speaker: Pavel Golubev (Lund University)

Slides CALIFA_SFAIR_Nov2014_PG.pdf

10:15 Alignment of silicon strip detectors on a micrometer scale¶

Using detectors with high spatial resolution demands precise nowledge of the relative position of detectors with respect to each other. Mechanical measurements have a limited precision, which is not always sufficient. In the LAND-setup at GSI, 4 silicon strip detectors are used to track beam particles and reaction products upstream as well as downstream from the target. The detectors have a spatial resolution in the order of 10 microns. Aligning several such detectors mechanically along the beam axis with this precision is not possible without sophisticated methods. Here an alternative approach is presented where the detectors are moved virtually after the experiment in a way that their positions fit the measured ion tracks. The method using the software program Millepede II is presented and results are discussed.

Speaker: Mr Simon Lindberg (Chalmers University of Technology)

Slides lindberg.pdf

10:40 → 11:00 Coffee

11:00 → 12:35 SFAIR¶

SFAIR årsmöte 2014 (rum 80101)

11:00 Prospects for exotics with PANDA¶

Speaker: Ulrich Wiedner (Bochum University)

Slides Wiedner_XYZ.pdf

11:45 VPTT sensors for the PANDA EMC: tests at photon energies below 100 MeV¶

Speaker: Dirk Wölbing (Stockholm University)

Slides Wolbing_ResponseofVPTT_(SFAIR).pdf

12:10 PANDA EMC read-out electronics¶

Speaker: Pawel Marciniewski (Uppsala University)

Slides PMarciniewski_SFAIR_Uppsala.pdf

12:35 → 14:00 Lunch

14:00 → 15:20 SFS-KF¶

Svenskt kärnfysikermöte (rum 80101)

14:00 Lifetime measurement of the first excited 2+ state in 112Te¶

In this work we present the preliminary results obtained in the experiment: The evolution of collectiv- ity near the N=Z=50 closed shell in the neutron-deficient nuclei 111I and 113I using DPUNS, performed at the Accelerator Laboratory of the University of Jyva ̈skyla ̈ (Finland). The aim of the experiment has been to measure the lifetime of excited states in neutron-deficient nuclei by using the Recoil Distance Doppler Shift method (RDDS). In particular we are interested on the investigation of the shape evolution in Te isotopes performed through the determination of the reduced transition probability. The states have been populated through a fusion-evaporation reaction between a 58Ni beam of 250 MeV energy and a 58Ni target of 1 mg/cm2. The target was mounted together with a Mg degrader foil of 1.2 mg/cm2 thickness in a compact Plunger device, DPUNS, provided by the University of Manchester. Fusion-evaporation products were separated in-flight from fission products using the RITU gas-filled recoil separator and implanted at the focal plane of the GREAT spectrometer. Prompt gamma-rays were detected at the target position by the JUROGAM-2 array consisting of 15 tapered and 24 clover Ge detectors distributed in four rings at different angles with respect to the beam direction. This combined setup together with the Recoil-Decay Tagging (RDT) technique leads an unique opportunity for studying this neutron-deficient region of the nuclear chart. The results of the work will be discussed in detail at the talk.

Speaker: Dr Maria Doncel (Royal Institute of Technology (KTH))

Slides DONCEL_SNPM_2014.pdf

14:20 Isomeric fission yield measurements at IGISOL¶

Fission yield data is a key parameter in the design and operation of nuclear power plants. Fission yield distributions depend not only on the fissioning nuclei, but also on the energy and type of the incoming particles inducing fision. More accurate data could improve both safety and fuel economy of present generation reactors as well as that of future nuclear systems. Improved knowledge of isomeric fission yields are also important for simulations of the astrophysical r-process. The Accurate Fission data FOr Nuclear Safety (AlFONS) project aims at high precision measurements of fission yields, using the renewed Ion Guide Isotope Separator Online (IGISOL) facility in combination with a new high-current light-ion cyclotron at the University of Jyväskylä. Fission can be induced in an actinide target either directly by the 30 MeV proton beam or by a neutron field from a Beryllium converter target. Through a series of elements, culminating with the JYFLTRAP Penning trap, the fission fragments can be mass separated at a resolving power of a few hundred thousand. The mass resolution is enough to resolve single isotopes as well as some isomeric states. We will here present the experimental setup and the IGISOL technique as well as some preliminary results from measurements performed in 2013 and 2014 of isomeric yield ratios of proton induced fission of Uranium and Thorium.

Speaker: Mr Vasilis Rakopoulos (Uppsala University)

Slides rakopoulos_SNPmeeting_2014.pdf

14:40 Spectroscopy of low-lying states in neutron-deficient astatine and francium nuclei¶

Recent years have been a particularly active period in the study of neutron-deficient astatine and francium nuclei. For instance new isotopes and new isomers have been reported [1,2,3,4,5], and laser-spectroscopic studies have been performed [6,7]. In this contribution we would like to report on results from in-beam and decay-spectroscopic studies performed in this region using fusion-evaporation reactions with stable heavy-ion beams at the accelerator laboratory of the University of Jyväskylä, Finland (JYFL). Shape coexistence, associated with the intruder picture, has been studied extensively in the region of neutron-deficient nuclei close to lead. A motivation for the study of particularly astatine and francium nuclei that lie three and respectively five protons above the shell closure, is the question of the prevalence of the intruder picture, as the shell closure moves further below the Fermi surface. In the odd-Z elements bismuth, astatine and francium, shape coexistence is observed between the 9/2− (πh9/2 ), 13/2+ (πi13/2 ) and 1/2+ (πs−1 1/2) states. Of these, the 1/2+ state is generated through the intruder mechanism. In heavier isotopes the spherical 9/2− state remains the ground state, whereas in lighter isotopes the 1/2+ state becomes the ground state, introducing ground-state deformation. The odd i13/2 proton may also couple to the intruder excitation, resulting in the deformation of the 13/2+ state. Such a coupling will bring the 13/2+ state down in energy and rotational structures observable through in-beam gamma-ray spectroscopy, will be built on this state. The difficulty in studying excited states in the neutron-deficient astatine and francium nuclei is the low production yield due to the high rate of fission competing against fusion-evaporation at each evaporation step. These challenges are met by the RITU gas-filled recoil separator used in conjunction with the JUROGAM germanium-detector array and the GREAT focal-plane spectrometer located at JYFL. We have observed the 1/2+ state at low excitation energy in the nuclei At-199, At-201, Fr-203 and Fr-205 through novel focal-plane electron spectroscopy, where the implantation detector performed as a calorimeter observing the cascade de-exciting the 1/2+ state to the 9/2− ground state. We have, in addition, for the first time observed the isomeric 13/2+ state in neutron-deficient francium nuclei, namely in Fr-203 and Fr-205. We want to present these results and give an overview on the properties of the ground state and isomeric 1/2+ and 13/2+ states in astatine and francium nuclei. [1] J. Uusitalo et al., Phys. Rev. C 87, 064304 (2013) [2] Z. Kalaninov'a et al., Phys. Rev. C 87, 044335 (2013) [3] U. Jakobsson et al., Phys. Rev. C 85, 014309 (2012) and Phys. Rev. C 87, 054320 (2013) [4] M. Nyman et al., Phys. Rev. C 88, 054320 (2013) [5] K. Auranen et al., Phys. Rev. C 90, 024310 (2014) [6] A. Voss et al., Phys. Rev. Lett. 111, 122501 (2013) [7] K. T. Flanagan et al., Phys. Rev. Lett., 111, 212501 (2013)

Speaker: Dr Ulrika Jakobsson (KTH)

Slides ulrika-presentation.pdf

15:00 Nuclear spectroscopy with Geant4¶

Comprehensive Monte-Carlo simulations using the Geant4 toolkit open the door for direct nuclear structure insights for a variety of physics cases, in particular when applied in a self-consistent way, i.e. confronting simulated data with real experimental data. Extentions to the Geant4 source code are necessary to extend the usage of the simulation toolkit to cover, for instance, the heaviest man-made atomic nuclei or proton radioactivity. Physics examples and Geant4 developments towards nuclear spectroscopy will be discussed.

Speaker: Dr Luis Sarmiento (Lund University)

Slides Pico-Sarmiento.pdf

15:20 → 15:50 Coffee

15:50 → 17:50 SFS-KF¶

Svenskt kärnfysikermöte (rum 80101)

15:50 From CELSIUS to COSY: On the Observation of a Dibaryon Resonance¶

Within the program to systematically study the two-pion production in nucleon-nucleon collisions by CELSIUS/WASA also the ominous ABC effect was investigated, which denotes an unusual huge low-mass enhancement in the invariant mass spectrum of an isoscalar pion pair produced in double-pionic fusion process. Due to the lack of convincing explanations the effect got named after Abashian, Booth and Crowe, who were the first to observe this phenomenon in inclusive measurements back in 1960. After having confirmed the ABC effect by exclusive and kinematically complete experiments at CELSIUS/WASA first indications of a correlation of this effect with a resonance-like structure in the total cross section were observed in the basic double-pionic fusion reaction np -> dpi0pi0 [1]. After the move of the WASA detector to COSY the two-pion production program could be continued with WASA-at-COSY with much superior intensity and precision. As a result the resonance effect could be established in all relevant two-pion channels and its quantum numbers determined to be I(JP) = 0(3+) [2-4]. If the hypothesis of a genuine dibaryon resonance is true, then it has to be observed also in neutron-proton scattering directly – though its effect is expected to be tiny. Since the analyzing power is the best observable to sense even tiny contributions to the scattering amplitude, high-statistics measurements of polarized neutron-proton scattering have been performed over the region of the anticipated resonance with WASA-at-COSY. Incorporation of these new data into the SAID partial-wave analysis produces, indeed, a resonance pole in the 3D3-3G3 coupled partial waves at (2380±10 – i 40±5) MeV – in full agreement with the findings in the two-pion production channels and establishing thus the first observation of a dibaryon resonance[5]. References [1] M. Bashkanov et al., Phys. Rev. Lett. 102, 052301 (2009). [2] P. Adlarson et al., Phys. Rev. Lett. 106, 242302 (2011). [3] P. Adlarson et al., Phys. Lett. B 721, 229 (2013) [4] P. Adlarson et al., Phys. Rev. C 88, 055208 (2013) [3] P. Adlarson et al., Phys. Rev. Lett. 112, 202301 (2014) and Phys. Rev. C 90, 035204 (2014).

Speaker: Prof. Heinz Clement (Physikalisches Institut, University of Tuebingen)

Slides hcl_Uppsala_2014.pdf

16:30 Hadronic decays of the omega meson¶

Studies of the decay reactions omega -> pi+ pi- pi0 and omega -> pi+ pi- will be presented. The data used for this study was collected by the WASA-at-COSY collaboration where the omega mesons were produced through the reaction p + d -> 3He + omega. These studies are part of an ongoing PhD project in the nuclear physics group at Uppsala university. The decay mechanism for the omega -> pi+ pi- pi0 channel can be studied in detail through the doubly differential decay width distribution, also called a Dalitz plot. Previous measurements of such a plot are of limited statistics. A high-statistics Dalitz plot would allow for convincing tests of theoretical predictions of the decay mechanism and final state interactions. The isospin breaking omega -> pi+ pi- decay can give insight into the behaviour of the rho-omega mixing. This channel has already been widely studied in e+e- collisions where the interference has been conclusively shown as destructive. Only a few measurements with limited statistics have been performed for hadronic production of the omega meson with hints of a possible constructive interference. The aim of this study is to investigate the structure of the omega -> pi+ pi- signal in proton on deuteron collisions.

Speaker: Ms Lena Heijkenskjöld (Uppsala University)

Slides SKF2014_Lena.pdf

16:50 Kärnfysiksektionens Årsmöte¶

Speaker: Christian Forssén (Chalmers University of Technology)

Slides arsmote.pdf epsnpd_2014_jn.pdf

19:00 → 22:00 Conference dinner

Kalmar Nation
Svartmangatan 3 ,
Centrala Uppsala

Wednesday, 12 November ¶

09:00 → 10:30 SFS-KF¶

Svenskt kärnfysikermöte (rum 80101)

09:00 Odd-even mass staggering, shell effects, and pairing correlation in neutron-rich nuclei¶

The empirical pairing gaps derived from four different odd-even mass staggering formulae are compared. By performing single-$j$ shell and multi-shell seniority model calculations as well as by using the standard HFB approach with Skryme force we show that the three-point formula ${\mathrm{\Delta }}_C^{(3)}(N)=\frac{1}{2}[B(N,Z)+B(N-2,Z)-2B(N-1,Z)]$ provides a good measure of the neutron pairing gap in even-$N$ nuclei. It removes to the largest extent the contribution from the nuclear mean field as well as contributions from shell structure details. It is also free from the Wigner effect for nuclei around $N=Z$. We also show that the strength of ${\mathrm{\Delta }}_C^{(3)}(N)$ can serve as a good indication of the two-particle correlation in the nucleus of concern and that the weakening of ${\mathrm{\Delta }}_C^{(3)}(N)$ in some neutron-rich nuclei indicates that the di-neutron correlation itself is weak in these nuclei.

Speaker: Ms Sara Asiyeh Changizi (Royal Institute of Technology (KTH))

Slides s_changizi.pdf

09:20 Alpha decay and nuclear structure of odd nuclei¶

Recent experiments [1] have made a first exploration of the low-energy spectroscopy of super heavy elements around Z=115. One uses alpha-gamma-coincidence measurements to probe the low lying states. This calls for a theoretical understanding of the alpha decay and structure in particular of odd nuclei. In the alpha decay of an odd nucleus the resulting daughter nucleus can often be left in an exited state, which subsequently decays electromagnetically. The most probable state to alpha decay into is the one where the odd particle occupies the same orbital as in the mother nucleus -- such decays are called favored. Hindered decays, where the orbital of the odd particle changes, are generally less probable. As a first approximation one can employ rule-of-thumb estimates to determine how hindered a certain alpha decay is [2]. The largest hindrance is associated with decays where the odd nucleon intrinsic spin changes direction, a spin flip, and where the parity of the mother and daughter are different. To correctly asses which states are connected by alpha decay one needs to consider the interplay between the energy dependence of the alpha particle tunneling and the formation probability of the alpha particle given the different daughter and mother nucleus states. This requires a microscopic theoretical description. In previous work [3, 4] we considered alpha decay of even near-spherical nuclei using a microscopic Skyrme-HFB approach. From the wave functions obtained in the self-consistent mean field calculations we calculated the alpha-particle formation amplitudes. The resulting decay rates reasonably reproduce data, especially shell and pairing effects not captured by simpler models. In the current work we extend the approach to near-spherical odd-A nuclei. By considering different quasi-particle excitations of the daughter nucleus we obtain the partial alpha-decay rates for different possible decay branches of the mother nucleus. Comparing the obtained decay rates with experimental data we see a good agreement for the relative rates of different favored and hindered decay branches. The hindrance observed in experiment varies from nucleus to nucleus. In the calculations both the overall hindrance, and the variation in the decay rates for different nuclei are reproduced. References [1] D. Rudolph et al., Phys. Rev. Lett. 111, 112502 (2013). [2] G. T. Seaborg and W. D. Loveland, The Elements Beyond Uranium, Wiley-Interscience, New York (1990). [3] D. E. Ward, B. G. Carlsson, and S. Åberg, Phys. Rev. C 88, 064316 (2013) [4] D. E. Ward, B. G. Carlsson, and S. Åberg, Phys. Scr. 89, 054027 (2014).

Speaker: Mr Daniel Ward (Department of Physics, Lund University)

Slides Ward-SFS-KF2014-v3.pdf

09:40 Proton halos in Cluster effective field theory¶

Proton halos are loosely bound nuclei consisting of a core plus valence proton(s). Compared to neutron halos, a proton halo system is more involved due to the presence of the Coulomb repulsion. We study these systems using the so called Halo, or Cluster, effective field theory (EFT). In this EFT the core of the halo nucleus is treated as a structureless, effective degree-of-freedom. The main advantages of using EFT are the systematic way of improving results, by including higher orders, and the fact that error estimates can be extracted at each order. We have considered one-proton halos bound due to an S-wave interaction to next-to-leading order and due to a P-wave interaction at leading order. Results that will be shown include the astrophysical S-factors for the reactions 16O(p,γ)17F* and 7Be(p,γ)8B and the charge radii of the one-proton halo states 17F* and 8B.

Speaker: Emil Ryberg (Chalmers University of Technology)

Slides Ryberg.pdf

10:00 News from VR¶

Speaker: Prof. Lars Bergström (SU)

10:30 → 11:00 Coffee

11:00 → 12:00 SFS-KF¶

Svenskt kärnfysikermöte (rum 80101)

11:00 The pion transition form factor - why it is interesting and how to calculate it¶

speaker: Stefan Leupold coauthors: M. Hoferichter, B. Kubis, F. Niecknig, S.P. Schneider abstract: The pion transition form factor denotes the process where a pion converts to a real or virtual photon by emitting another virtual photon. In general, form factors parametrize the deviation from point-like behavior. Therefore the pion transition form factor encodes information about the intrinsic structure of the pion. In addition, the pion transition form factor is needed for the high-precision standard-model prediction of the magnetic moment of the muon [1]. This process shows some deviation between standard-model prediction and experiment. Therefore it is one of the candidates where beyond-standard-model physics might become visible if the experimental and the standard-model uncertainties can be reduced. One necessary input is the knowledge of the pion transition form factor with a reliable, i.e. model independent, uncertainty estimate. I will show first results from our ongoing project to calculate the pion transition form factor based on dispersion theory [2]. [1] E. Czerwinski et al., MesonNet Workshop on Meson Transition Form Factors, e-Print: arXiv:1207.6556 [hep-ph]. [2] M. Hoferichter, B. Kubis, S. Leupold, F. Niecknig, S.P. Schneider, work in progress.

Speaker: Stefan Leupold (Uppsala University)

Slides leupold-pionTFF.pdf

11:20 Studies of electromagnetic η and η’ decays with the Crystal Ball-TAPS detector.¶

Precision studies of light mesons decays are used to study a wide range of topics related to fundamental aspects of hadron physics. Besides tests of fundamental symmetries of the Standard Model, precision data of η and η’ decays provide a testing ground for effective field theory. In addition, measurements of the η and η’ transition form factors give valuable information on the hadronic light-by-light contribution to the anomalous magnetic moment of the muon. With the Crystal Ball-TAPS detector setup at the Mainz Microtron, large statistics samples of η and η’ have been collected. An overview of the experimental setup and recent results on electromagnetic η and η’ decays are presented.

Speaker: Dr Patrik Adlarson (Johannes Gutenberg Universität)

Slides Adlarson_eta.pdf

11:40 Study of the near-threshold ωϕ mass enhancement in doubly OZI suppressed J/ψ→γωϕ decays¶

The Beijing Electron-Positron Collider (BEPCII) is a double ring $e^{+}{e}^{-}$ collider operating within a Centre-of-Energy interval of $2.0-4.6$ GeV with a design luminosity of $1\times {10}^{33}$ cm${}^{-2}{\text{s}}^{-1}$. The Beijing Spectrometer (BESIII) is a large detector located at the BEPCII and has accumulated the largest sample of $J/\psi$, $\psi (2S)$, and $\psi (3770)$ events for studies of light hadron and charmonium spectroscopy, the hadron-to-lepton ratio $R$ as a function of energy, and high mass charmonium states including the $X$, $Y$ and $Z$ particles. Until now, a lot of physics results have been published. In this talk, I focus on the study of the near-threshold $\omega \varphi$ mass enhancement in doubly OZI suppressed $J/\psi \to \gamma \omega \varphi$ decays. A sample of 2.25$\times$10${}^8$ $J/\psi$ events was accumulated with the BESIII detector. A strong deviation ($>$ 30$\sigma$) from three-body $J/\psi \to \gamma \omega \varphi$ phase space is observed near the $\omega \varphi$ mass threshold that is consistent with a previous observation reported by the BESII experiment. A partial wave analysis (PWA) with a tensor covariant amplitude formalism has been performed, assuming that the enhancement is due to the presence of a resonance, here referred to as the $X(1810)$. PWA is an important tool in light hadron spectroscopy, used to determine resonance properties (like mass, width, branching fraction, spin and parity). Also PWA can deal with the interference of resonances. The PWA confirms that the spin-parity of the $X(1810)$ is $0^{++}$. The mass and width of the $X(1810)$ are determined to be $M=1795\pm 7$(stat)${}_{-5}^{+13}$(syst)$\pm$19(mod) MeV/$c^2$ and $\mathrm{\Gamma }=95\pm 10$(stat)${}_{-34}^{+21}$(syst)$\pm$75(mod) MeV/$c^2$, respectively. The product branching fraction is measured to be $\mathcal{B}(J/\psi \to \gamma X(1810))\times \mathcal{B}(X(1810)\to \omega \varphi )=(2.00\pm 0.08$(stat)${}_{-1.00}^{+0.45}$(syst)$\pm$1.30(mod))$\times {10}^{-4}$. These results are consistent within errors with those of the BESII experiment. The decay $J/\psi \to \gamma \omega \varphi$ is a doubly OZI suppressed process that is expected to be suppressed relative to $J/\psi \to \gamma \omega \omega$ or $J/\psi \to \gamma \varphi \varphi$ by at least one order of magnitude. The anomalous enhancement observed at the $\omega \varphi$invariant-mass threshold and the large measured branching fractions ($\sim$1/2 of $\mathcal{B}(J/\psi \to \gamma \varphi \varphi )$) are surprising and interesting. The enhancement is not compatible with being due either to the $X(1835)$ or the $X(p\overline{p})$, due to the different mass and spin-parity.

Speaker: Dr Cui Li (Uppsala University)

Slides SFS-KF_Cui_LI.pdf

12:00 → 13:00 Lunch

13:00 → 14:20 SFS-KF¶

Svenskt kärnfysikermöte (rum 80101)

13:00 TALYS: A unified approach towards nuclear reaction calculations¶

An overview of the TALYS system for the simulation of nuclear reactions will be given.

Speaker: Prof. Arjan Koning (NRG)

Slides Koning_UU_SPS.pdf

13:40 Anisotropy and detection efficiency effects in the measurement of fission cross section with PPAC detectors¶

Accurate values of the fission cross section of different isotopes are crucial for the development of new nuclear reactors. For that reason, the n_TOF facility at CERN is carrying out an extensive program on neutron-induced reactions. The high-intensity neutron beam covers an unprecedented neutron energy range, from less than 1 eV up to 1 GeV. In order to study fission reactions, a chamber with up to ten Parallel Plate Avalanche Counters (PPAC) is used to identify, in time coincidence, both fission fragments emitted in the targets placed in between. The stripped cathodes used in the PPAC allow us to know the fragment position in each detector and, therefore, to determine their trajectory. Because of the limited geometrical acceptance of the PPACs, the measured fission cross sections have to be corrected by means of the limited geometrical acceptance affecting the detector efficiency. This correction is particularly important for incident neutron energies close to the multiple-chance thresholds. However, in the setup used at CERN - n_TOF Phase1 (2002-2003), the detectors and the targets were perpendicular to the beam and, as a result, the angular distribution could not be measured, forcing us to rely on previously available data on the anisotropy to correct for the detection efficiency [1].çTo solve that constraint, an improved geometrical configuration, where both detectors and targets were tilted 45o with respect to the neutron beam direction, was used during Phase2 (2010-2012) [2,3]. This new configuration makes possible to detect fission fragments at any angle between 0o and 90o so that the full angular distribution can be measured allowing, therefore, a properly self-correction of the detection efficiency. This talk will focus on the advantages of the new geometrical configuration, and on how the efficiency correction is applied to data in both setups to measure the fission cross section in the wide neutron energy range of n_TOF. A comparison of the results obtained with both setups for the Th-232(n,f) reaction will be shown. [1] C. Paradela et al., Phys. Rev. C82, 034601 (2010) [2] D. Tarrío, Nucl. Instr. And Meth. A743, 79-85 (2014) [3] L.-S. Leong, PhD thesis, Université Paris-Sud (2013)

Speaker: Dr DIEGO TARRIO (UPPSALA UNIVERSITY)

14:00 Smooth Startup Problem for Innovative Fast Reactor Working in Nuclear Burning Wave Regime¶

The results of optimization of the smooth start-up method for the innovative fast reactor (FR) working in the nuclear burning wave (NBW) regime (known also as a Traveling Wave Reactor) are presented. This method has to prevent the excessive increase of neutron flux and energy production in FR at the stage of establishing self-sustained NBW regime mainly due to the lack of neutron-absorbing fission products at this stage compared with the steady-state NBW regime. The problem is studied by means of numerical simulation of the initiation and evolution of NBW in such a reactor with metallic U-Th fuel. For this simulation we use the deterministic approach, developed in [1], and based on solving the non-stationary neutron diffusion equation using the effective multi-group approximation together with a set of burn-up equations for fuel components and equations of nuclear kinetics for precursor nuclei of delayed neutrons. The selection of the ignition zone compositions that provides a smooth start-up of the NBW reactor is carried out. The features of the initial stage of the NBW reactor are studied in detail. 1. S.P. Fomin et al., Ann. Nucl. Energy, 32 (2005) 1435; Prog. Nucl. Energy, 50 (2008) 163; 53 (2011) 800.

Speaker: Mr Oleksiy Fomin (Uppsala University)

Slides 2014-11-12_O_Fomin.pdf

14:20 → 14:50 Coffee

14:50 → 16:10 SFS-KF¶

Svenskt kärnfysikermöte (rum 80101)

14:50 Reducing nuclear data uncertainties using differential and integral experimental data¶

The current nuclear data uncertainties observed in some reactor parameters for some nuclides, calls for safety concern especially with respect to the design of GEN-IV reactors and should therefore be reduced further. In this paper, we present two approaches for incorporating differential experimental data and criticality benchmark information into the Total Monte Carlo methodology for reducing these uncertainties. These methods have been applied to the European Lead Cooled Training Reactor (ELECTRA).

Speaker: Mr Erwin Alhassan (Uppsala University)

Slides Alhassan_SNPM_2014.pdf

15:10 Performance Measurements for the Ge Tracking Array AGATA¶

From 2012 to 2014 the pan-European Advanced GAmma-ray Tracking Array (AGATA) is placed at the German accelerator research centre GSI Darmstadt. Within the PreSPEC collaboration, AGATA is used to perform high-resolution γ-ray spectroscopy of relativistic radioactive ions to obtain unique nuclear structure information of exotic nuclei far away from the line of stability. In order to evaluate the performance of AGATA array and compare with Monte-Carlo simulations, a series of gamma-ray source measurements were conducted at GSI. Different sources have been used, such as 60-Co, 56-Co, 152-Eu and 166m-Ho. The results of this calibration measurement with 21 AGATA crystals coupled with a single EUROBALL encapsulated detector used as a coincidence trigger are presented. In these performance figures the absolute and relative efficiency, P/T ratio, quality of the Pulse-shape Analysis and the effect of tracking will be evaluated. In addition to the aforementioned aspects, the analysis of AGATA performance at high multiplicities is ongoing.

Speaker: Ms Natasa Lalovic (Lund University Sweden)

Slides Lalovic_talk_noApp.pdf

15:30 Dynamics of the eta-prime meson at finite temperature¶

speaker: Elisabetta Perotti coauthor: Stefan Leupold, Carl Niblaeus We investigate how the lifetime of the eta-prime changes in a thermal system. At high temperatures we expect an increase of the width due to interactions with particles from the heat bath (pions in our approximation). Already at T=120 MeV, the lifetime of the eta-prime seems to become comparable to that of a fireball created in heavy-ion collisions. This suggests that it could be possible to study how the eta-prime properties change close to the transition, where the spontaneously broken chiral symmetry of QCD is restored. The interest in the eta-prime is motivated by its deep connection to the U(1)_A anomaly of QCD, whose behaviour at high temperatures is still unknown. I will show results from my Master thesis project, obtained in the framework of Resonance Chiral theory [1] and I will compare them with last year results from C. Niblaeus’ Master thesis [2] based on large-Nc Chiral Perturbation theory [3]. References [1] G. Ecker, J. Gasser, A. Pich, and E. de Rafael, The Role of Resonances in Chiral Perturbation Theory, Nucl.Phys. B321, 311 (1989). [2] C. Niblaeus, In-medium width of the eta-prime meson, Master Thesis. Uppsala (2013). [3] S. Scherer, Introduction to chiral perturbation theory, Adv.Nucl.Phys. 27, 277 (2003).

Speaker: Elisabetta Perotti (Uppsala University)

Slides Perotti_SNPtalk.pdf

15:50 The search for a quasi-bound eta 3He state in dp collisions with COSY-ANKE¶

The dp --> 3He eta reaction is known for the unexpected energy dependence of its total cross section, which rises rapidly to its plateau value within the first 1 MeV of excess energy Q. This behaviour has been ascribed to a strong final state interaction and may indicate a quasi-bound eta 3He state. In order to investigate the possibility of spin-dependent contributions to the total cross section, the deuteron tensor analysing power has been measured in an excess energy range from Q = 0 MeV up to above Q = 10 MeV at the COSY-ANKE spectrometer. This allows one to compare the magnitudes of the contributions from the two spin configurations in the entrance channel with the strong variation seen in the average production amplitude. Furthermore, a weak angular dependence of T20 was also extracted and provides insight into the structure of the production amplitude close to threshold. Supported by the COSY FFE programme.

Speaker: Mr Michael Papenbrock (Uppsala University)

Slides Papenbrock_Uppsala.pdf