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Professor Dr. Norbert Pietralla TU Darmstadt Nuclear Structure Physics at 4GLS Norbert Pietralla Institut für Kernphysik Darmstadt University of Technology.

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Presentation on theme: "Professor Dr. Norbert Pietralla TU Darmstadt Nuclear Structure Physics at 4GLS Norbert Pietralla Institut für Kernphysik Darmstadt University of Technology."— Presentation transcript:

1 Professor Dr. Norbert Pietralla TU Darmstadt Nuclear Structure Physics at 4GLS Norbert Pietralla Institut für Kernphysik Darmstadt University of Technology TUD Collaborative Research Center SFB634 Research Center of Excellence Nuclear and Radiation Physics TUD

2 Professor Dr. Norbert Pietralla TU Darmstadt Vision of Nuclear Physics Understanding the properties of heavy atomic nuclei from their basic constituents, quarks and gluons, and from the interactions between them.

3 Professor Dr. Norbert Pietralla TU Darmstadt Relevance Deductive understanding of Nature Solid understanding of the nucleus as a laboratory for other fields (standard model, neutrino physics, strongly interacting many-body Fermi-systems…) Dynamics of cosmic objects and the “Origin of the Elements“ (astrophysics, nuclear astrophysics)

4 Professor Dr. Norbert Pietralla TU Darmstadt Recent Progress Systematic derivation of structural form of nucleon-nucleon interaction from QCD in Chiral Perturbation Theory Unique low-energy NN-potential V low-k from Renormalization Group approach Non-perturbative all-order calculations from self- consistent iteration methods for nuclear many- body systems Advanced many-body techniques, e.g., No-Core Shell Model, Monte-Carlo Shell Model,…

5 Professor Dr. Norbert Pietralla TU Darmstadt shell structure: valence nucleons Cooper pairing: N s,d boson system Collective motion: nuclear shapes Once the atomic nucleus is formed effective (in-medium) forces can generate simple pattern.

6 Professor Dr. Norbert Pietralla TU Darmstadt Outline Nuclear physics with low-energy photons (nuclear dipole physics) Impact of photon beams from Laser Compton Backscattering  Recent progress at Duke‘s HI  S  Research potential of  -ray beams from Laser Compton Backscattering Summary

7 Professor Dr. Norbert Pietralla TU Darmstadt Nuclear Structure Physics with low-energy photon beams Pure EM-interaction (nuclear-) model independent “small“ cross sections, thick targets Minimum projectile mass min. angular momentum transfer, spin-selective: dipole-modes Polarisation “Parity physics“

8 Professor Dr. Norbert Pietralla TU Darmstadt Nucleon-Spin-flip Role of Isovector Spin-flip M1 excitations in Nuclear Physics E (MeV) Quark-Spin-flip

9 Professor Dr. Norbert Pietralla TU Darmstadt Electric Giant Dipol Resonance (GDR) Protons Neutrons Sensitive to average Proton-Neutron-Restoring Force but insensitive to shell structure: need low-energy E1/M1 data ! GDR in 197 Au GDR-Strength vs A Data from: A.Bohr, B.Mottelson “Nuclear Structure” E1

10 Professor Dr. Norbert Pietralla TU Darmstadt Photonuclear Reactions gs ´´  Separation threshold AXAX A´ Y  Nuclear Resonance Fluorescence (NRF) Photoactivation Photodesintegration  Absorption (-activation) ´´

11 Professor Dr. Norbert Pietralla TU Darmstadt Traditionally Bremsstrahlung: Kneissl,Pietralla,Zilges, J.Phys.G 32, R217 (2006).

12 Professor Dr. Norbert Pietralla TU Darmstadt Overview: dipole modes Exotic Modes B(M1) Orbital M1 Strength Scissors mode,… Spin M1 Strength

13 Professor Dr. Norbert Pietralla TU Darmstadt Scissors Mode in Deformed Nuclei (Darmstadt, 1983) Bohle et al., NPA 458, 205 (1986). Scissors mode classically: current loop => M1 magnetic dipole excitation electron scattering photon scattering

14 Professor Dr. Norbert Pietralla TU Darmstadt Richter, Kneissl, von Brentano et al. Collectivity of the Scissors Mode M1 phenomena in the nuclear valence shell E2M1 Measure of quadrupole collectivity 2+2+ Stuttgart-Darmstadt-Köln 1+1+ N. Pietralla et al., PRC 58, 184 (1998)

15 Professor Dr. Norbert Pietralla TU Darmstadt S-DALINAC facility at IKP TU Darmstadt 1 2 Photon Experiments 10 MeV Injector: Photon Scattering / Photofission < 30 MeV Tagger: Photodesintegration / Photon Scattering Source 130 MeV Electron LINAC Electron Source

16 Professor Dr. Norbert Pietralla TU Darmstadt Darmstadt Low-Energy Photon Scattering Site at S-DALINAC Target Ge(HP)  -detectors Radiator target e-e-  Energie Intensity Electrons Energie Intensity Bremsstrahlung < 10 MeV Cu A.Zilges E  < 10 MeV Cu

17 Professor Dr. Norbert Pietralla TU Darmstadt

18 A. Zilges et al., PLB 542 (2002) 43. S. Volz et al., NPA 779 (2006) 1. A. Zilges, contrib. to Vico Equense 07. Systematics of the Pygmy Dipole Resonance Concentration around 5-7 MeV Strong fragmentation Summed strength: Scaling with N/Z ? Is this really all E1 strength ?

19 Professor Dr. Norbert Pietralla TU Darmstadt Parity Measurements Principle of a Compton-Polarimeter

20 Professor Dr. Norbert Pietralla TU Darmstadt Modest polarisation sensitivity Better use polarized  -ray beams !

21 Professor Dr. Norbert Pietralla TU Darmstadt Azimuthal asymmetry → parity quantum no. Parity Measurements with Linearly Polarized Photon Beams

22 Professor Dr. Norbert Pietralla TU Darmstadt

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28 HIgS Beam Profile

29 Professor Dr. Norbert Pietralla TU Darmstadt Testing shell structure from M1 Spin-flip excitation

30 Professor Dr. Norbert Pietralla TU Darmstadt

31 40Ar First ever observation of a 1 + state of 40 Ar

32 Professor Dr. Norbert Pietralla TU Darmstadt Duke-Stony Brook expt. high-pressure Ar gas HIgS polarized g-beam 7.7 MeV < E < 11 MeV analyzing power 50% Duke – Stony Brook data (2 examples)

33 Professor Dr. Norbert Pietralla TU Darmstadt T.C.Li, NP et al, Phys.Rev.C (2006).

34 Professor Dr. Norbert Pietralla TU Darmstadt Astrophysical Relevance of M1 Data Darmstadt data 54 Fe Langanke et al., PRL (2004). Neutrino-cross sections

35 Professor Dr. Norbert Pietralla TU Darmstadt Direct Measurement of B(GT) from Charge-Exchange Reactions Osaka-data Fujita et al., PRL(2005). Adachi et al.,PRC (2006).

36 Professor Dr. Norbert Pietralla TU Darmstadt Polarized Beams 100 keV Polarized Electron Gun 5 m Spatial restriction – transport of accelerator equipment 10 MeV Injector 250 keV Thermionic Electron Gun To Experimental Hall

37 Professor Dr. Norbert Pietralla TU Darmstadt Preparation system Polarized electron gun Differential pumping stages Injector cryostat Prebuncher system Chopper Mott polarimeter Wien filter 1 m S-DALINAC Polarized INjector (SPIN) From Gun Laser Red Hall Entrance Thermionic electron gun Injector cryostat 2 m  Design of polarized injector beam line finished (Prof.Dr.J.Enders)  Installation begins – middle of 2007

38 Professor Dr. Norbert Pietralla TU Darmstadt Polarization in the entrance channel Linear polarization (HI  S) spin/parity program (since 2001) Circular polarization (HI  S, S-DALINAC) parity non-conservation 20 Ne, 238 U EE bremsstrahlung spectrum NN P  ≤ 75% e-e- target  circular bremstarget -θ-θ θ Forward-backward asymmetry ? Parity-violation Weak interaction

39 Professor Dr. Norbert Pietralla TU Darmstadt The 20 Ne case: parity mixing of yrast levels ΔE=7.5±5.7 keV “enhancement factor” 670 ± 7000 Γ(1 - ) ≤ 0.3 keV Γ(1 + ) ? T < = ± ±3 20 Ne F, T < =  (d 5/2 1 ) (d 5/2 3 ) gs T=1 isobaric analog states Goal: measure parity violation in simple states ! Understand effects of weak interaction microscopically ► e.g., study the parity doublet in 20 Ne !

40 Professor Dr. Norbert Pietralla TU Darmstadt Heavy Atomic nucleus many-body system consists of two equivalent entities (protons-neutrons) quantum system COLLECTIVITY SHELL STRUCTURE ISOSPIN SYMMETRY Two-fluid quantum system Generic Aspects of Nuclear Structure Coexist, interplay, and compete? Study collective proton-neutron valence shell excitations ! (combine all 3 aspects)

41 Professor Dr. Norbert Pietralla TU Darmstadt Themes and challenges of Modern Science Complexity out of simplicity How the world, with all its apparent complexity and diversity can be constructed out of a few elementary building blocks and their interactions Simplicity out of complexity How the world of complex systems can display such astonishing regularity and simplicity Understanding the nature of the physical universe Manipulating nature for the benefit of mankind Nuclei: Two-fluid, many-body, strongly-interacting, quantal systems provide wonderful laboratories for frontier research in all four areas From US-NSAC-charge: “Nuclear Physics with the Rare Isotope Accelerator”

42 Professor Dr. Norbert Pietralla TU Darmstadt Summary Nuclear structure physics with  -ray beams is a vivid field with high discovery potential 4GLS can become a major facility in this field Needs: - energy-tunable, high-flux, polarized  -ray beam from LASER- Compton backscattering All this is possible at 4GLS !

43 Professor Dr. Norbert Pietralla TU Darmstadt

44 Die Valenz-Proton-Neutron Wechselwirkung Bestimmt die Entwicklung von Kollektivitaet und Kerndeformation Bildet die mikroskopische Grundlage fuer Deformations- Phasen-Uebergangsverhalten (Federman-Pittel Mechanismus) Bewirkt Besetzungszahlabhaengigkeit von Einteilchen- Energien, Energieluecken und Schalenstruktur

45 Professor Dr. Norbert Pietralla TU Darmstadt MSSs* at the analytical Limits N  = N = SU(3) Rotor Scissors Mode N.Pietralla et al. Univ.zu Koeln, 1999 K= U(5) Vibrator F max -1 MS multi-Phonon structure A. Richter et al. TU Darmstadt, 1983 * MSSs = proton-neutron Mixed-Symmetry States

46 Professor Dr. Norbert Pietralla TU Darmstadt Proton-Neutron symmetrische und gemischt-symmetrische Valenzraumanregungen (schematisch/geometrisch) Sphaerischer Kern Vibration Deformierter Kern Rotation Protonen-Neutronen ausser Phase Gem.-sym. Vibration Protonen-Neutronen ausser Phase Scherenmode Animation: Robert Casperson (Yale)


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