496 Wilhelm und Else HeraeusSeminar 6 10 February
496. Wilhelm und Else Heraeus-Seminar 6 -10 February 2012 – Physikzentrum Bad Honnef – Germany Astrophysics with modern small-scale accelerators The 40 Ca( , )44 Ti reaction studied by activation 06/02/2012 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 Supported by DFG (BE 4100/2 -1) Institute of Radiation Physics | Division of Nuclear Physics | http: //www. hzdr. de
The 40 Ca( , )44 Ti reaction - Outline § Introduction § Setup § State of the art § Results § Summary Page 2 06/02/2012 Member of the Helmholtz Association Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | http: //www. hzdr. de
The 40 Ca( , )44 Ti reaction - Outline § Introduction § Setup § State of the art § Results § Summary Page 3 06/02/2012 Member of the Helmholtz Association Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | http: //www. hzdr. de
The 40 Ca( , )44 Ti reaction - Introduction Supernova remnant Cassiopeia A § Supernovae are source of heavy elements § Their explosions eject matter enriched with freshly formed isotopes § 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 § 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 Image was taken with the NASA/ESA Hubble Space Telescope and edited by Fesen and Long 2006 Page 4 06/02/2012 Member of the Helmholtz Association Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | http: //www. hzdr. de
The 40 Ca( , )44 Ti reaction - Introduction Production of 44 Ti in supernovae Page 5 06/02/2012 Member of the Helmholtz Association Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | http: //www. hzdr. de
The 40 Ca( , )44 Ti reaction - Introduction The mass cut § 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 Page 6 06/02/2012 Mass profiles of 44 Ti and 56 Ni for a 25 M core-collapse supernova model (adapted from Hoffman et al. 1995) Member of the Helmholtz Association Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | http: //www. hzdr. de
The 40 Ca( , )44 Ti reaction - Introduction Decay of 44 Ti and 44 Sc Page 7 06/02/2012 Member of the Helmholtz Association Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | http: //www. hzdr. de
The 40 Ca( , )44 Ti reaction - Introduction Supernova signal: 44 Ti in Cassiopeia A § image was taken with the NASA/ESA Hubble Space Telescope § 44 Ti is produced near the mass cut between infalling and ejected material in the -rich freeze out phase § Sensitive probe of supernova models Fesen and Long 2006 COMPTEL on CGRO, NASA IBIS on INTEGRAL, ESA Iyudin et al. 1997 Renaud et al. 2006 Page 8 06/02/2012 Member of the Helmholtz Association Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | http: //www. hzdr. de
The 40 Ca( , )44 Ti reaction - Outline § Introduction § Setup § State of the art § Results § Summary Page 9 06/02/2012 Member of the Helmholtz Association Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | http: //www. hzdr. de
The 40 Ca( , )44 Ti reaction - Setup at HZDR Ion Beam Center at HZDR experiment Page 10 06/02/2012 Member of the Helmholtz Association Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | http: //www. hzdr. de
The 40 Ca( , )44 Ti reaction - Setup at HZDR 3 MV Tandetron at Ion Beam Center experiment negative ions electrodes SF 6 gas (up to 12 bar) electrodes vacuum tube nitrogen stripper accelerated ions ion source resistance chain negative ions Page 11 06/02/2012 stripper electrical potential high voltage positive ions Member of the Helmholtz Association Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | http: //www. hzdr. de
The 40 Ca( , )44 Ti reaction - Setup at HZDR Resonances for beam energy calibration of 3 MV Tandetron § Nominal ion energies accelerator: Enom = e Uion Yield [µC-1] can be read from § Incident ion energy E 0 at the target differ from nominal ion § Resonances used: Yield [µC-1] energy Enom § statistical error at 4. 5 Me. V: DE 0 = 1. 3 ke. V (0. 03 %) Page 12 06/02/2012 27 Al(p, ) 40 Ca(p, ) Member of the Helmholtz Association Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | http: //www. hzdr. de
The 40 Ca( , )44 Ti reaction - Setup at HZDR Beam line and detectors 40 Ca( , )44 Ti 60 % HPGe, 90° with BGO or 100 % HPGe, 55° with BGO 40 Ca(p, )41 Sc beam or proton beam Page 13 06/02/2012 Member of the Helmholtz Association Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | http: //www. hzdr. de
The 40 Ca( , )44 Ti reaction - Setup at HZDR Distances and targets § Ca. O targets • natural composition (96% 40 Ca) • from GSI target lab, Darmstadt ion beam § Al targets • for beam energy and efficiency calibration • from ATOMKI Debrecen, Hungary § beam spot after irradiation: Ca. O target Ta backing ion beam § thin gold layer applied after irradiation to protect the 44 Ti Page 14 06/02/2012 Member of the Helmholtz Association Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | http: //www. hzdr. de
The 40 Ca( , )44 Ti reaction - Setup at HZDR Target chamber beam or proton beam Page 15 06/02/2012 Member of the Helmholtz Association Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | http: //www. hzdr. de
The 40 Ca( , )44 Ti reaction - Outline § Introduction § Setup § State of the art § Results § Summary Page 16 06/02/2012 Member of the Helmholtz Association Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | http: //www. hzdr. de
The 40 Ca( , )44 Ti reaction - State of the art Important resonances and approach completed under analysis planned 2012 § Approach: 1. Activation at high-intensity 3 MV Tandetron 2. -counting at Felsenkeller Dresden well-characterized calibration sources 3. Determination of resonance strengths are necessary Page 17 06/02/2012 Member of the Helmholtz Association Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | http: //www. hzdr. de
The 40 Ca( , )44 Ti reaction - State of the art Calibrated 44 Ti standards § used high-precision calibration sources A [Bq] (HZDR) § underground laboratory Felsenkeller Source A [Bq] (PSI) A [Bq] (VKTA) P-60 46 ± 9 35. 5 ± 0. 4 (1. 1 %) – Sources by PSI/ERAWAST P-160 151 ± 15 67. 5 ± 0. 8 (1. 2 %) 63 ± 4 (Exotic Radionuclides from Accelerator Waste for Science and Technology) F-130 146 ± 15 137. 1 ± 1. 7 (1. 2 %) – F-320 310 ± 30 225 ± 3 (1. 3 %) – P-690 600 ± 60 498 ± 6 (1. 2 %) – § reference date: 01/01/2010 Page 18 06/02/2012 Member of the Helmholtz Association Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | http: //www. hzdr. de
The 40 Ca( , )44 Ti reaction - State of the art Literature values Reference [ke. V] Dixon et al. 1977 (Nat. Res. Council of Canada) 4523, 4510 and 4497 Vockenhuber et al. 2007 4523, 4510 (DRAGON at TRIUMF, Canada) and 4497 Hoffman et al. 2010 (Lawrence Livermore Nat. Lab. ) Page 19 06/02/2012 (8. 3 ± 1. 3) e. V (16 %) (12. 0 ± 1. 2) e. V (10 %) 4523, 4510, (16 ± 3) e. V 4497, … (19 %) Cooperman et al. 1977 3618 ± 6 (California State Univ. , Fullerton) (0. 33 ± 0. 07) e. V (21 %) Vockenhuber et al. 2007 3618 ± 6 (0. 40 ± 0. 08) e. V (20 %) Cooperman et al. 1977 Vockenhuber et al. 2007 3584 ± 6 (0. 52 ± 0. 10) e. V (0. 53 ± 0. 12) e. V (19 %) (23 %) Cooperman et al. 1977 Vockenhuber et al. 2007 3722 ± 6 (0. 22 ± 0. 04) e. V (0. 46 ± 0. 11) e. V (18 %) (24 %) Cooperman et al. 1977 Vockenhuber et al. 2007 2758 ± 22 (0. 013 ± 0. 003) e. V (23 %) (0. 013 ± 0. 007) e. V (44 %) Member of the Helmholtz Association Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | http: //www. hzdr. de
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: § Triplet at 4. 5 Me. V: • (4523 ± 2) ke. V • (4510 ± 2) ke. V • (4497 ± 2) ke. V § Differences: • 13 ke. V each § Measure the sum of all 3 resonance strengths at 4. 5 Me. V Page 20 06/02/2012 Member of the Helmholtz Association Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | http: //www. hzdr. de
The 40 Ca( , )44 Ti reaction - State of the art Reduced level scheme of 44 Ti Page 21 06/02/2012 Member of the Helmholtz Association Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | http: //www. hzdr. de
The 40 Ca( , )44 Ti reaction - Outline § Introduction § Setup § State of the art § Results § Summary Page 22 06/02/2012 Member of the Helmholtz Association Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | http: //www. hzdr. de
The 40 Ca( , )44 Ti reaction - Results In-beam -spectrum § natural composition (96% 40 Ca) in Ca. O 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. Page 23 06/02/2012 Member of the Helmholtz Association Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | http: //www. hzdr. de
The 40 Ca( , )44 Ti reaction - Results Triplet at 4. 5 Me. V laboratory energy § Sample 14, 100 % detector at 55° • Difference between lower and main resonance: (12. 4 ± 1. 0) ke. V • Difference between main and upper resonance: (14. 0 ± 1. 0) ke. V § Sample 29, 100 % detector at 55° • Difference between lower and main resonance: (11. 3 ± 1. 0) ke. V • Difference between main and upper resonance: (13. 7 ± 1. 0) ke. V Page 24 06/02/2012 Member of the Helmholtz Association Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | http: //www. hzdr. de
The 40 Ca( , )44 Ti reaction - Results Number of nuclei and activity as a function of time § Example calculation § Initial number of 44 Ti nuclei is 9× 106 § T 1/2(44 Ti) = 58, 9 y § T 1/2(44 Sc) = 3. 891 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 Page 25 06/02/2012 Member of the Helmholtz Association Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | http: //www. hzdr. de
The 40 Ca( , )44 Ti reaction - Results Offline spectra from HZDR and Felsenkeller (below 47 m of rock) Page 26 06/02/2012 Member of the Helmholtz Association Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | http: //www. hzdr. de
The 40 Ca( , )44 Ti reaction - Results Structure scans before and after activation by 40 Ca(p, )41 Sc reaction one point with high statistics in order to solve following problem § 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 Page 27 06/02/2012 Member of the Helmholtz Association Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | http: //www. hzdr. de
The 40 Ca( , )44 Ti reaction - Results Problem 1: unknown ratio of O to Ca in Ca. O targets § Yield Yp of 40 Ca(p, )41 Sc reaction to determine ratio n of O to Ca in Ca. O § Resonance strength wg = (140 ± 15) me. V (11 %) by Zijderhand et al. 1987 Solution 1 effective stopping power § Hence we find the sum of resonance strengths for the 40 Ca( , )44 Ti reaction (relative to 40 Ca(p, )41 Sc): § Yield Yp of 16 O(p, )17 F reaction to determine ration n of O to Ca in Ca. O § Cross section s = (4. 84 ± 0. 24) b (5 %) by Iliadis et al. 2008 target thickness Solution 2 § With this we find the sum of resonance strengths for the 40 Ca( , )44 Ti reaction (relative to 16 O(p, )17 F): Page 28 06/02/2012 Member of the Helmholtz Association Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | http: //www. hzdr. de
The 40 Ca( , )44 Ti reaction - Results Problem 2: The measurement of extremely low activity Triplet at 4. 5 Me. V laboratory energy § triplet resonance strength: wg = 8. 1 e. V (present work, preliminary) § irradiation: 16 h with beam intensity of 1 µA (6 · 1018 / sec) § 44 Ti activity from irradiation: A = 5. 09 m. Bq • net count rate: R = 7· 10 -4 counts / sec • time to measure: t = 2 weeks § relative activity uncertainty: Resonance at 3. 7 Me. V laboratory energy § resonance strength: wg = 0. 22 e. V (Cooperman et al. 1977) § irradiation: 3 · 24 h with beam intensity of 1 µA (6 · 1018 / sec) § 44 Ti activity from irradiation: A = 1. 34 m. Bq • 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 Page 29 06/02/2012 Member of the Helmholtz Association Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | http: //www. hzdr. de
The 40 Ca( , )44 Ti reaction - Results and Outlook completed, ERDA in future under analysis, counting at Felsenkeller planned 2012, 23 % uncertainty in literature Dixon et al. 1977 Vockenhuber et al. 2007 result of present work (preliminary) triplet w = (8. 3 ± 1. 3) e. V w = (12. 0 ± 1. 2) e. V w = (8. 1 ± 0. 5) e. V Cooperman 1977 Vockenhuber et al. 2007 present work 3584 ke. V 21 % uncertainty 20 % uncertainty under analysis Cooperman et al. 1977 Vockenhuber et al. 2007 present work 3618 ke. V 19 % uncertainty 23 % uncertainty under analysis Page 30 06/02/2012 (16 %) (10 %) (6. 2 %) Member of the Helmholtz Association Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | http: //www. hzdr. de
The 40 Ca( , )44 Ti reaction - Outline § Introduction § Setup § State of the art § Results § Summary Page 31 06/02/2012 Member of the Helmholtz Association Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | http: //www. hzdr. de
The 40 Ca( , )44 Ti reaction - Summary § Astrophysically interesting resonance triplet of the 40 Ca( , )44 Ti reaction at 4. 5 Me. V has been studied with Ca. O 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 ke. V has been determined: Reference Activated Elab [ke. V] wg Dixon et al. 1977 4523, 4510 and 4497 (8, 3 ± 1, 3) e. V (16 %) Vockenhuber et al. 2007 4523, 4510 and 4497 (12, 0 ± 1, 2) e. V (10 %) Hoffman et al. 2010 4523, 4510, 4497, … (16 ± 3) e. V (19 %) present work (preliminary) 4523, 4510 and 4497 (8. 1 ± 0. 5) e. V (6. 2 %) § Outlook: • Study resonances at 3. 5, 3. 6, and 3. 7 Me. V (under analysis) • Experiment at laboratory energy of 2. 8 Me. V (later this year) Thank you for your attention. Page 32 06/02/2012 Member of the Helmholtz Association Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | http: //www. hzdr. de
The 40 Ca( , )44 Ti reaction - Appendix Page 33 06/02/2012 Member of the Helmholtz Association Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | http: //www. hzdr. de
The 40 Ca( , )44 Ti reaction - Appendix reduced level scheme & measured in beam pulse height spectrum 19 F( , n )22 Na Data by Evaluated Nuclear Structure Data File Page 34 06/02/2012 Member of the Helmholtz Association Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | http: //www. hzdr. de
The 40 Ca( , )44 Ti reaction - Appendix Impact Analysis § Yield § Resonance strenght § Narrow resonance reaction rate ILIADIS, C. : Nuclear Physics of Stars. Wiley-VCH (2007) Page 35 06/02/2012 Member of the Helmholtz Association Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | http: //www. hzdr. de
The 40 Ca( , )44 Ti reaction - Well calibrated 44 Ti standards Preparation and structure of weak 44 Ti sources § 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: 200 nm 5 nm 220 µm 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) 014046 • SCHUMANN, D. ; SCHMIDT, K. ; BEMMERER, D. : Characterization and Calibration of weak 44 Ti sources for astrophysical applications. In: PSI Annual Report 2010 Page 36 06/02/2012 Member of the Helmholtz Association Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | http: //www. hzdr. de
The 40 Ca( , )44 Ti reaction - Well calibrated 44 Ti standards Characterization of weak 44 Ti sources with imaging plates § Irradiation of the imaging plate § Scanning the imaging plate • Resolution: 5 µm • Gradation: 65, 536 (16 bit) § Plot the data http: //home. fujifilm. com/info/products/science/toc. html Page 37 06/02/2012 Member of the Helmholtz Association Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | http: //www. hzdr. de
The 40 Ca( , )44 Ti reaction - Well calibrated 44 Ti standards Characterization of weak 44 Ti point sources P-60 P-160 P-690 § PSL corresponds to the -ray intensity Page 38 06/02/2012 Member of the Helmholtz Association Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | http: //www. hzdr. de
The 40 Ca( , )44 Ti reaction - Well calibrated 44 Ti standards Characterization of weak 44 Ti plane sources F-130 F-320 § PSL corresponds to the -ray intensity Page 39 06/02/2012 Member of the Helmholtz Association Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | http: //www. hzdr. de
The 40 Ca( , )44 Ti reaction - Setup at HZDR Beam energy calibration of 3 MV Tandetron § Nominal ion energies can be read from accelerator Enom = e Uion § Incident ion energy E 0 at the target differ from nominal ion energy Enom § Calibration by Trompler et al. 2009 (diploma thesis): • resonances used: 27 Al(p, ); 14 N(p, ); 15 N(p, ) • energy range: 0. 5 to 2. 0 Me. V • fit function: E 0 = (1. 017 ± 0. 002) · Enom – (5. 2 ± 1. 0) ke. V • statistical error at 4. 5 Me. V: DE 0 = 10 ke. V (0. 2 %) § New calibration of present work (2010): • resonances used: 27 Al(p, ); 40 Ca( , ) • energy range: up to 4. 5 Me. V • fit function: E 0 = (1. 0142 ± 0. 0003) · Enom • statistical error at 4. 5 Me. V: DE 0 = 1. 3 ke. V (0. 03 %) § New calibration (without offset) includes particles Page 40 06/02/2012 Member of the Helmholtz Association Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | http: //www. hzdr. de
The 40 Ca( , )44 Ti reaction - Setup at HZDR Comparison of old and new calibration of 3 MV Tandetron Page 41 06/02/2012 Member of the Helmholtz Association Konrad Schmidt | Institute of Radiation Physics | Division of Nuclear Physics | http: //www. hzdr. de
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