Nuclear Astrophysics at the Darmstadt superconducting electron linear accelerator S-DALINAC

1. Nuclear Astrophysics at the Darmstadt superconducting electron linear acceleratorS-DALINAC Kerstin Sonnabend ESF Workshop onThe future of stable beams in Nuclear Astrophysics Athens, Greece December 14th to 15th, 2007 supported by the DFG under grant No. SFB 634

2. Contents • S-DALINAC at TU Darmstadt • Photoactivation experiments • HIPS – High-intensity photon setup • LCS – Laboratory for counting & spectroscopy • NEPTUN – High-resolution photon tagger • Electron-scattering experiments • QCLAM – Large-acceptance spectrometer

3. S-DALINAC at TU Darmstadt HIPS – electron energies from 2 to 130 MeV available – cw and pulsed beam operation possible – source for polarized electron beams under construction injector: two 20-cell Nb cavities, up to 11 MeV main linac: eight 20-cell Nb cavities, up to 40 MeV per circle first recirculation second recirculation beam extraction

4. HIPS – High-intensity photon setup Au/Re - target 11B - target n n g g 0 ≤ Eg ≤ Emax 0 ≤ Eg ≤ Emax electrons Emax collimator radiator Activation with continuous-energy bremsstrahlung ≈ 300 · Ng Ng ≈ 105g / (keV s cm2) K. Sonnabend et al., Astroph. J. 583 (2003) 506 K. Vogt et al., Nucl. Phys. A707 (2002) 241

5. LCS – Laboratory for counting and spectroscopy Pb HPGe Cu Pb Pb g LEPS LEPS g g g Cu Pb Pb Determination of activation yield with g-spectroscopy – three low-energy photon spectrometers (LEPS) – four 30% and 40% HPGe detectors – setups with passive Cu and/or Pb shielding – complementation with x-ray detectors and electron counters

6. LCS – Laboratory for counting and spectroscopy Sample decay spectra: LEPS versus HPGe

7. Photoactivation experiments • Activation yield Y measured offline • Use of naturally composed targets (e.g.196Hg, 198Hg, 199mHg, 200Hg) • Activate targets simultaneously (e.g. Zr, Re, Ir, and Au) • Measure weak g branchings (e.g.185W: T1/2 = 75 d, Eg=125 keV, Ig≈10-4) •  method perfectly suited for systematic studies • Restrictions of activation method • Appropriate lifetime of product nucleus • Appropriate  transitions during decay of product nucleus •  Accelerator Mass Spectrometry (AMS) • No direct cross section measurements •  Use quasi-monoenergetic photon beams, e.g. AIST, Japan •  Use tagged photons, e.g. NEPTUN @ S-DALINAC

8. Photoactivation experiments NEPTUN taggersystem NEPTUN – High-resolution photon tagger 5 m

9. NEPTUN – High-resolution photon tagger magnet 1 m coincidence focal plane radiator experiment photons electrons Energy range: 6 MeV ≤ Eg ≤ 20 MeV Energy resolution: DE = 25 keV @ 10 MeV Energy window: ≈ 3 MeV Photon intensity: ≈ 104 keV-1s-1 Photon energy: Eg = Ei - Ee

10. NEPTUN – High-resolution photon tagger Recent data from test experiment SE PP DE

11. NEPTUN – High-resolution photon tagger DE SE PP ≈ 250 keV FWHM ≈ 50 keV Recent data from test experiment

12. Photoactivation experiments NEPTUN detectorarray High-resolution cross section measurements 5 m

13. NEPTUN – High-resolution photon tagger – 14 liquid scintillator neutron detectors – 8 additional 10B enriched liquid scintillator detectors Determine (g,n) cross sections with 100 keV ≤ En ≤ 10 MeV – high-resolution cross section measurements – determination of angular momentum of neutrons – (g,p) and (g,a) in preparation

14. Electron-scattering experiments QCLAM (e,e‘x) experiments of astrophysical interest 5 m

15. QCLAM – Large-acceptance spectrometer – scattering chamber – quadrupole magnet – clamshell dipole magnet (deflection angle: 120°) – three multiwire drift chambers – plastic scintillation and plexiglas Cherenkov counters

16. QCLAM – Large-acceptance spectrometer – momentum resolution:Dp/p = 2  10-4 – solid angle acceptance: 35 msr – max. central momentum: 200 MeV/c – momentum acceptance: ±10%

17. QCLAM – Large-acceptance spectrometer Electron scattering at 180° deflection angle – momentum resolution:Dp/p = 2  10-4 – solid angle acceptance: 6.4 msr – max. central momentum: 95 MeV/c – momentum acceptance: -5% to +8%

18. Electron-scattering experiments Recent results on M1 deuteron break-up – high energy resolution and high selectivity of M1 states – precision test of modern theoretical models – prediction of p(n,g)d cross section at Big Bang energies

19. Electron-scattering experiments Shell-Modeltotal Orbital Spin B(M1) / m2N 54Fe 52Cr  / 10-42 cm2 50Ti S-DALINAC 52Cr B(M1) / m2N Neutrino Energy / MeV excitation energy / MeV K. Langanke et al., PRL 93 (2004) 202501 Role of neutrino-induced reactions – high resolution (e,e‘) data  M1 strength distribution  GT0 from shell-model calc.  n-nucleus cross section • properties of pre-collapse core • supernova shock revival • explosive nucleosynthesis

20. Electron-scattering experiments Nucleosynthesis of 9Be and 10B • production mechanism of 9Be and 10,11B not clear •  spallation of 12C by neutrinos • branching ratios of 12C(e,e‘x) •  detection and discrimination of p, d, t, 3He and 4He •  E-E-telescopes, TOF and/or PSD • electro-weak theory •  extract (,‘) cross sections

21. Experimental hall of the S-DALINAC NEPTUN HIPS QCLAM Setups for experiments on Nuclear Astrophysics

22. Many thanks to… Technische Universität Darmstadt:M. Fritzsche, E. Gehrmann, J. Glorius, J. Hasper, K. Lindenberg, S. Müller, N. Pietralla,A. Sauerwein, D. Savran, L. Schnorrenberger,and the QCLAM group Universität zu Köln:M. Büssing, J. Endres, M. Elvers, and A. Zilges Roberto Gallino, Torino, Italy Franz Käppeler, Karlsruhe, Germany Karlheinz Langanke, Darmstadt, Germany Alberto Mengoni, Vienna, Austria Thomas Rauscher, Basel, Switzerland