Institute of Radiation Physics | Division of Nuclear Physics | Wilhelm und Else Heraeus-Seminar 6-10 February 2012 – Physikzentrum Bad Honnef – Germany Astrophysics with modern small-scale accelerators 06/02/2012 Supported by DFG (BE 4100/2-1) The 40 Ca( ,  ) 44 Ti reaction studied by activation Konrad Schmidt 1,2, Chavkat Akhmadaliev 1, Michael Anders 1, Daniel Bemmerer 1, Konstanze Boretzky 3, Antonio Caciolli 4, Zoltán Elekes 1, Zsolt Fülöp 5, György Gyürky 5, Roland Hannaske 1, Arnd Junghans 1, Michele Marta 1,3, Ronald Schwengner 1, Tamás Szücs 5, Andreas Wagner 1, Dmitry Yakorev 1, and Kai Zuber 2 — 1 Helmholtz-Zentrum Dresden- Rossendorf (HZDR) — 2 TU Dresden — 3 GSI Darmstadt — 4 INFN Padua, Italy — 5 ATOMKI Debrecen, Hungary

Member of the Helmholtz Association Page 2 06/02/2012 Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | The 40 Ca( ,  ) 44 Ti reaction  Introduction  Setup  State of the art  Results  Summary - Outline

Member of the Helmholtz Association Page 3 06/02/2012 Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | The 40 Ca( ,  ) 44 Ti reaction  Introduction  Setup  State of the art  Results  Summary - Outline

Member of the Helmholtz Association Page 4 06/02/2012 Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | The 40 Ca( ,  ) 44 Ti reaction - Introduction Supernova remnant Cassiopeia A Image was taken with the NASA/ESA Hubble Space Telescope and edited by Fesen and Long 2006  Supernovae are source of heavy elements  Their explosions eject matter enriched with freshly formed isotopes  44 Ti decay offers a unique window to the study of supernova:  -rays penetrate the entire galactic disk with little extinction 44 Ti  -rays reflect the current rate of supernovae cosmic 44 Ca mainly daughter of 44 Ti  44 Ti was confirmed in Cas A only. Why?  -rays survey quality Supernova explosion and nucleosynthesis models 44 Ti half-life Destruction of 44 Ti because of 44 Ti( ,p) reaction Nuclear reaction parameters of 44 Ti producing reactions, like 40 Ca( ,  ) 44 Ti

Member of the Helmholtz Association Page 5 06/02/2012 Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | The 40 Ca( ,  ) 44 Ti reaction - Introduction Production of 44 Ti in supernovae

Member of the Helmholtz Association Page 6 06/02/2012 Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | The 40 Ca( ,  ) 44 Ti reaction - Introduction The mass cut Mass profiles of 44 Ti and 56 Ni for a 25 M  core-collapse supernova model (adapted from Hoffman et al. 1995)  Diehl et al. 1998: The abundance of 44 Ti and 56 Ni as a function of mass inside a 25 M  star is shown The mass cut is shown as the solid vertical line Everything interior to the mass cut becomes part of the neutron star Everything exterior may be ejected, depending on how much mass falls back onto the neutron star during the explosion  The position of the mass cut determines, if 44 Ti is detectable in a Supernova  T 1/2 ( 56 Ni) = 6.08 d  T 1/2 ( 57 Ni) = 35.6 h  T 1/2 ( 44 Ti) = 58.9 y

Member of the Helmholtz Association Page 7 06/02/2012 Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | The 40 Ca( ,  ) 44 Ti reaction - Introduction Decay of 44 Ti and 44 Sc

Member of the Helmholtz Association Page 8 06/02/2012 Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | The 40 Ca( ,  ) 44 Ti reaction - Introduction Supernova signal: 44 Ti in Cassiopeia A IBIS on INTEGRAL, ESA COMPTEL on CGRO, NASA Renaud et al Iyudin et al Fesen and Long 2006  44 Ti is produced near the mass cut between infalling and ejected material in the  -rich freeze out phase  Sensitive probe of supernova models  image was taken with the NASA/ESA Hubble Space Telescope

Member of the Helmholtz Association Page 9 06/02/2012 Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | The 40 Ca( ,  ) 44 Ti reaction  Introduction  Setup  State of the art  Results  Summary - Outline

Member of the Helmholtz Association Page 10 06/02/2012 Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | The 40 Ca( ,  ) 44 Ti reaction - Setup at HZDR Ion Beam Center at HZDR experiment

Member of the Helmholtz Association Page 11 06/02/2012 Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | The 40 Ca( ,  ) 44 Ti reaction - Setup at HZDR ion source vacuum tube accelerated ions high voltage resistance chain negative ions positive ions stripper electrical potential nitrogen stripper SF 6 gas (up to 12 bar) electrodes 3 MV Tandetron at Ion Beam Center experiment

Member of the Helmholtz Association Page 12 06/02/2012 Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | The 40 Ca( ,  ) 44 Ti reaction - Setup at HZDR Resonances for beam energy calibration of 3 MV Tandetron Yield [µC -1 ] 27 Al(p,  ) 40 Ca( ,  ) 40 Ca(p,  )  Nominal ion energies can be read from accelerator: E nom = e U ion  Incident ion energy E 0 at the target differ from nominal ion energy E nom  Resonances used:  statistical error at 4.5 MeV:  E 0 = 1.3 keV (0.03 %)

Member of the Helmholtz Association Page 13 06/02/2012 Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | The 40 Ca( ,  ) 44 Ti reaction - Setup at HZDR 40 Ca( ,  ) 44 Ti or 40 Ca(p,  ) 41 Sc 60 % HPGe, 90° with BGO 100 % HPGe, 55° with BGO  beam or proton beam Beam line and detectors

Member of the Helmholtz Association Page 14 06/02/2012 Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | The 40 Ca( ,  ) 44 Ti reaction - Setup at HZDR Distances and targets  CaO targets natural composition (96% 40 Ca) from GSI target lab, Darmstadt  Al targets for beam energy and efficiency calibration from ATOMKI Debrecen, Hungary  beam spot after irradiation:  thin gold layer applied after irradiation to protect the 44 Ti ion beam CaO target Ta backing

Member of the Helmholtz Association Page 15 06/02/2012 Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | The 40 Ca( ,  ) 44 Ti reaction - Setup at HZDR  beam or proton beam  beam or proton beam Target chamber

Member of the Helmholtz Association Page 16 06/02/2012 Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | The 40 Ca( ,  ) 44 Ti reaction  Introduction  Setup  State of the art  Results  Summary - Outline

Member of the Helmholtz Association Page 17 06/02/2012 Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | The 40 Ca( ,  ) 44 Ti reaction Important resonances and approach completed  Approach: 1.Activation at high-intensity 3 MV Tandetron 2.  -counting at Felsenkeller Dresden 3.Determination of resonance strengths under analysis planned 2012 under analysis well-characterized calibration sources are necessary - State of the art

Member of the Helmholtz Association Page 18 06/02/2012 Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | The 40 Ca( ,  ) 44 Ti reaction Calibrated 44 Ti standards - State of the art Source A [Bq] (PSI) A [Bq] (HZDR) A [Bq] (VKTA) P-6046 ± ±0.4(1.1 %)– P ± ±0.8(1.2 %)63 ± 4 F ± ±1.7(1.2 %)– F ± ±3(1.3 %)– P ± ±6(1.2 %)–  used high-precision calibration sources  underground laboratory Felsenkeller  reference date: 01/01/2010 Sources by PSI/ERAWAST (Exotic Radionuclides from Accelerator Waste for Science and Technology)

Member of the Helmholtz Association Page 19 06/02/2012 Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | The 40 Ca( ,  ) 44 Ti reaction Literature values Dixon et al (Nat. Res. Council of Canada) Reference Vockenhuber et al (DRAGON at TRIUMF, Canada) - State of the art 4523, 4510 and 4497 (8.3 ± 1.3) eV(16 %) [keV] 4523, 4510 and 4497 (12.0 ± 1.2) eV(10 %) Hoffman et al (Lawrence Livermore Nat. Lab.) 4523, 4510, 4497, … (16 ± 3) eV(19 %) Cooperman et al (California State Univ., Fullerton) 3618 ± 6(0.33 ± 0.07) eV(21 %) Vockenhuber et al ± 6(0.40 ± 0.08) eV(20 %) Cooperman et al ± 6(0.52 ± 0.10) eV(19 %) Vockenhuber et al ± 6(0.53 ± 0.12) eV(23 %) Cooperman et al ± 6(0.22 ± 0.04) eV(18 %) Vockenhuber et al ± 6(0.46 ± 0.11) eV(24 %) Cooperman et al ± 22(0.013 ± 0.003) eV(23 %) Vockenhuber et al ± 22(0.013 ± 0.007) eV(44 %)

Member of the Helmholtz Association Page 20 06/02/2012 Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | The 40 Ca( ,  ) 44 Ti reaction - State of the art Energy straggling  Schematic representation of energy distribution functions f(E,d) for a beam of charged particles as they move through an absorber.  FWHM of the energy distribution corresponds to energy straggling  Best approximation by Bohr 1915:  Measure the sum of all 3 resonance strengths at 4.5 MeV  Triplet at 4.5 MeV: (4523 ± 2) keV (4510 ± 2) keV (4497 ± 2) keV  Differences: 13 keV each

Member of the Helmholtz Association Page 21 06/02/2012 Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | The 40 Ca( ,  ) 44 Ti reaction - State of the art Reduced level scheme of 44 Ti

Member of the Helmholtz Association Page 22 06/02/2012 Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | The 40 Ca( ,  ) 44 Ti reaction  Introduction  Setup  State of the art  Results  Summary - Outline

Member of the Helmholtz Association Page 23 06/02/2012 Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | The 40 Ca( ,  ) 44 Ti reaction - Results In-beam  -spectrum  natural composition (96% 40 Ca) in CaO targets   reactions on Ca: 40 Ca( ,  ) 41 Ca( ,p  ) 44 Sc 44 Ca( ,n  ) 47 Ti 44 Ca( ,  ) 48 Ti etc.   reactions on O: 16 O( ,  ) 20 Ne 18 O( ,n  ) 21 Ne etc.   reactions on additional contaminations: 19 F( ,n  ) 22 Na 19 F( ,p  ) 22 Ne etc.

Member of the Helmholtz Association Page 24 06/02/2012 Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | The 40 Ca( ,  ) 44 Ti reaction - Results Triplet at 4.5 MeV laboratory  energy  Sample 14, 100 % detector at 55° Difference between lower and main resonance: (12.4 ± 1.0) keV Difference between main and upper resonance: (14.0 ± 1.0) keV  Sample 29, 100 % detector at 55° Difference between lower and main resonance: (11.3 ± 1.0) keV Difference between main and upper resonance: (13.7 ± 1.0) keV

Member of the Helmholtz Association Page 25 06/02/2012 Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | The 40 Ca( ,  ) 44 Ti reaction Number of nuclei and activity as a function of time - Results  Example calculation  Initial number of 44 Ti nuclei is 9×10 6  T 1/2 ( 44 Ti) = 58,9 y  T 1/2 ( 44 Sc) = h  After 1 day the activity of 44 Sc becomes equal to the activity of 44 Ti: A ( 44 Ti) = A ( 44 Sc)  Contaminations decayed after a couple of days  Except for 22 Na T 1/2 ( 22 Na) = 2.6 y  Then counting in Felsenkeller started

Member of the Helmholtz Association Page 26 06/02/2012 Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | The 40 Ca( ,  ) 44 Ti reaction - Results Offline spectra from HZDR and Felsenkeller (below 47 m of rock)

Member of the Helmholtz Association Page 27 06/02/2012 Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | The 40 Ca( ,  ) 44 Ti reaction - Results Structure scans before and after activation by 40 Ca(p,  ) 41 Sc reaction  about 24 hours activation with a current of 1.5 µA at the water cooled target  Structure scans before and after activation have just minor differences  Conclusion: Target layer stays stable during the activation one point with high statistics in order to solve following problem

Member of the Helmholtz Association Page 28 06/02/2012 Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | The 40 Ca( ,  ) 44 Ti reaction  Yield Y p of 40 Ca(p,  ) 41 Sc reaction to determine ratio n of O to Ca in CaO  Resonance strength  = (140 ± 15) meV (11 %) by Zijderhand et al  Hence we find the sum of resonance strengths for the 40 Ca( ,  ) 44 Ti Problem 1: unknown ratio of O to Ca in CaO targets  Yield Y p of 16 O(p,  ) 17 F reaction to determine ration n of O to Ca in CaO  Cross section  = (4.84 ± 0.24) b (5 %) by Iliadis et al Results Solution 1 Solution 2 effective stopping power reaction (relative to 40 Ca(p,  ) 41 Sc):  With this we find the sum of resonance strengths for the 40 Ca( ,  ) 44 Ti reaction (relative to 16 O(p,  ) 17 F): target thickness

Member of the Helmholtz Association Page 29 06/02/2012 Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | The 40 Ca( ,  ) 44 Ti reaction Problem 2: The measurement of extremely low activity - Results Triplet at 4.5 MeV laboratory  energy  triplet resonance strength:  = 8.1 eV (present work, preliminary)  irradiation: 16 h with  beam intensity of 1 µA (6 ·  / sec)  44 Ti activity from irradiation: A = 5.09 mBq net count rate: R = 7·10 -4 counts / sec time to measure: t = 2 weeks  relative activity uncertainty: Resonance at 3.7 MeV laboratory  energy  resonance strength:  = 0.22 eV (Cooperman et al. 1977)  irradiation: 3 · 24 h with  beam intensity of 1 µA (6 ·  / sec)  44 Ti activity from irradiation: A = 1.34 mBq net count rate: R = 2·10 -4 counts / sec time to measure: t = 7 weeks  relative activity uncertainty: Conclusion:  only a few atoms in spite of the long irradiation  takes a long time to measure for acceptable statistics  we found 44 Ti contamination on sample holder, so that we had to repeat measurements

Member of the Helmholtz Association Page 30 06/02/2012 Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | The 40 Ca( ,  ) 44 Ti reaction Results and Outlook Dixon et al triplet Vockenhuber et al result of present work (preliminary) - Results  = (8.3 ± 1.3) eV  = (12.0 ± 1.2) eV  = (8.1 ± 0.5) eV (16 %) (10 %) (6.2 %) Cooperman keV Vockenhuber et al present work Cooperman et al keV Vockenhuber et al present work 19 % uncertainty 23 % uncertainty under analysis 21 % uncertainty 20 % uncertainty under analysis completed, ERDA in future under analysis,counting at Felsenkeller planned 2012,23 % uncertainty in literature under analysis,counting at Felsenkeller

Member of the Helmholtz Association Page 31 06/02/2012 Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | The 40 Ca( ,  ) 44 Ti reaction  Introduction  Setup  State of the art  Results  Summary - Outline

Member of the Helmholtz Association Page 32 06/02/2012 Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | The 40 Ca( ,  ) 44 Ti reaction - Summary  Astrophysically interesting resonance triplet of the 40 Ca( ,  ) 44 Ti reaction at 4.5 MeV has been studied with CaO targets.  Samples were irradiated using the  beam of the 3.3 MV Tandetron of Helmholtz- Zentrum Dresden-Rossendorf.  44 Ti activity has been measured in the underground laboratory Felsenkeller Dresden relative to a calibrated 44 Ti standard.  Sum of resonance strengths at laboratory energies of 4497, 4510 and 4523 keV has been determined: ReferenceActivated E lab [keV]  Dixon et al , 4510 and 4497(8,3 ± 1,3) eV(16 %) Vockenhuber et al , 4510 and 4497(12,0 ± 1,2) eV(10 %) Hoffman et al , 4510, 4497, …(16 ± 3) eV(19 %) present work (preliminary)4523, 4510 and 4497(8.1 ± 0.5) eV(6.2 %)  Outlook: Study resonances at 3.5, 3.6, and 3.7 MeV (under analysis) Experiment at laboratory  energy of 2.8 MeV (later this year) Thank you for your attention.

Member of the Helmholtz Association Page 33 06/02/2012 Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | The 40 Ca( ,  ) 44 Ti reaction - Appendix

Member of the Helmholtz Association Page 34 06/02/2012 Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | The 40 Ca( ,  ) 44 Ti reaction - Appendix 19 F( ,n  ) 22 Na reduced level scheme & measured in beam pulse height spectrum Data by Evaluated Nuclear Structure Data File

Member of the Helmholtz Association Page 35 06/02/2012 Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | The 40 Ca( ,  ) 44 Ti reaction  Yield  Resonance strenght  Narrow resonance reaction rate - Appendix Impact Analysis I LIADIS, C.: Nuclear Physics of Stars. Wiley-VCH (2007)

Member of the Helmholtz Association Page 36 06/02/2012 Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | The 40 Ca( ,  ) 44 Ti reaction Preparation and structure of weak 44 Ti sources - Well calibrated 44 Ti standards  preparation: by vaporating radionuclide-containing diluted nitric acid on tantalum plates 5 nm chromium serve as adherent layer for the protective layer covered with 200 nm thick gold layer afterwards in order to protect the surface  structure: Au Cr Ti Ta  more details: SCHUMANN, D.; NEUHAUSEN, J.: Accelerator waste as a source for exotic radionuclides. In: J. Phys. G: Nucl. Part. Phys. 35 (2008) SCHUMANN, D.; SCHMIDT, K.; BEMMERER, D.: Characterization and Calibration of weak 44 Ti sources for astrophysical applications. In: PSI Annual Report nm 5 nm 220 µm

Member of the Helmholtz Association Page 37 06/02/2012 Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | The 40 Ca( ,  ) 44 Ti reaction Characterization of weak 44 Ti sources with imaging plates - Well calibrated 44 Ti standards  Irradiation of the imaging plate  Scanning the imaging plate Resolution: 5 µm Gradation: 65,536 (16 bit)  Plot the data

Member of the Helmholtz Association Page 38 06/02/2012 Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | The 40 Ca( ,  ) 44 Ti reaction - Well calibrated 44 Ti standards Characterization of weak 44 Ti point sources P-60P-160P-690  PSL corresponds to the  -ray intensity

Member of the Helmholtz Association Page 39 06/02/2012 Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | The 40 Ca( ,  ) 44 Ti reaction - Well calibrated 44 Ti standards F-130 Characterization of weak 44 Ti plane sources  PSL corresponds to the  -ray intensity F-320

Member of the Helmholtz Association Page 40 06/02/2012 Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | The 40 Ca( ,  ) 44 Ti reaction - Setup at HZDR Beam energy calibration of 3 MV Tandetron  Nominal ion energies can be read from accelerator E nom = e U ion  Incident ion energy E 0 at the target differ from nominal ion energy E nom  Calibration by Trompler et al (diploma thesis): resonances used: 27 Al(p,  ); 14 N(p,  ); 15 N(p,  ) energy range: 0.5 to 2.0 MeV fit function: E 0 = (1.017 ± 0.002) · E nom – (5.2 ± 1.0) keV statistical error at 4.5 MeV:  E 0 = 10 keV (0.2 %)  New calibration of present work (2010): resonances used: 27 Al(p,  ); 40 Ca(p,  ); 40 Ca( ,  ) energy range: up to 4.5 MeV fit function: E 0 = ( ± ) · E nom statistical error at 4.5 MeV:  E 0 = 1.3 keV (0.03 %)  New calibration (without offset) includes  particles

Member of the Helmholtz Association Page 41 06/02/2012 Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | The 40 Ca( ,  ) 44 Ti reaction - Setup at HZDR Comparison of old and new calibration of 3 MV Tandetron