Alpha capture for astrophysics: Experiments in Dresden, Munich and Gran Sasso

• Applicant: Professor Dr. Daniel Bemmerer
• Subject Area: Nuclear and Elementary Particle Physics, Quantum Mechanics, Relativity, Fields
• Term: from 2009 to 2015
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 130478278

• Final Report Year: 2014

Final Report Abstract

In the framework of the present project, two α capture reactions of astrophysical relevance were studied in low-energy stable-beam experiments: • The 2 H(α,γ)6Li reaction controls the production of 6Li in standard Big Bang nucleosynthesis. This isotope attracted significant interest due to some initial reports about possible detections of 6Li in metal-poor stars. If confirmed, these reports would have led to a second lithium problem in addition to the wellknown existing cosmological 7Li problem. The reaction was studied using in-beam γ-spectroscopy at the LUNA 0.4 MV underground accelerator in Italy. Significant beam-induced background problems were overcome, and the data from this study are the first positive cross sections directly at Big Bang energies, and were published. • The 40 Ca(α,γ)44Ti reaction is believed to be responsible for the production of radioactive 44Ti in both corecollapse and thermonuclear supernovae. It was studied by in-beam γ spectroscopy and by activation. The data on the resonance triplet at Eα = 4.5 MeV and an unexpected but important ancillary result on the 40 Ca(p,γ)41Sc reaction were published. Additional publications were produced in the framework of the present project: One on a LUNA experiment on the 14 N(p,γ)15O reaction, and the second one on a feasibility study for the 40 Ca(α,p)43 Sc and 44Ti(α,p)47 V reactions. The highly successful 2H(α,γ)6Li experiment at LUNA can in principle be extended to higher beam energies, where the signal to background ratio is expected to be better. However, this requires an underground accelerator with higher end point energy than the LUNA 0.4 MV machine. The present 40Ca(α,γ)44Ti data address selected resonances and resolve a previously unknown normalization issue. In order to extend them, a higher α-beam intensity than the 1.5 µA available at the HZDR 3 MV Tandetron is needed. Both these issues can be addressed at the upcoming Felsenkeller underground accelerator in Dresden, with its 5 MV accelerating potential, low background, and high α-beam intensity.

Publications

• Revision of the 15 N(p,γ)16 O reaction rate and oxygen abundance in H-burning zones. Astronomy & Astrophysics 533, A66 (2011)
  A. Caciolli, C. Mazzocchi, V. Capogrosso, D. Bemmerer, C. Broggini, P. Corvisiero, H. Costantini, Z. Elekes, A. Formicola, Zs. Fulop, G. Gervino, A. Guglielmetti, C. Gustavino, Gy. Gyurky, G. Imbriani, M. Junker, A. Lemut, M. Marta, R. Menegazzo, S. Palmerini, P. Prati, V. Roca, C. Rolfs, C. Rossi Alvarez, E. Somorjai, O. Straniero, F. Strieder, F. Terrasi, H. P. Trautvetter, and A. Vomiero
  
• The 14 N(p,γ)15 O reaction studied with a composite germanium detector. Phys. Rev. C 83, 045804 (2011)
  M. Marta, A. Formicola, D. Bemmerer, C. Broggini, A. Caciolli, P. Corvisiero, H. Costantini, Z. Elekes, Zs. Fülöp, G. Gervino, A. Guglielmetti, C. Gustavino, Gy. Gyürky, G. Imbriani, M. Junker, A. Lemut, B. Limata, C. Mazzocchi, R. Menegazzo, P. Prati, V. Roca, C. Rolfs, C. Rossi Alvarez, E. Somorjai, O. Straniero, F. Strieder, F. Terrasi, H.P. Trautvetter, and A. Vomiero
  
• First Direct Measurement of the 17 O(p,γ)18 F Reaction Cross Section at Gamow Energies for Classical Novae. Phys. Rev. Lett. 109, 202501 (2012)
  D. A. Scott, A. Caciolli, A. DiLeva, A. Formicola, M. Aliotta, M. Anders, D. Bemmerer, C. Broggini, M. Campeggio, P. Corvisiero, Z. Elekes, Zs. Fülöp, G. Gervino, A. Guglielmetti, C. Gustavino, Gy. Gyürky, G. Imbriani, M. Junker, M. Laubenstein, R. Menegazzo, M. Marta, E. Napolitani, P. Prati, V. Rigato, V. Roca, E. Somorjai, C. Salvo, O. Straniero, F. Strieder, T. Szücs, F. Terrasi, and D. Trezzi
  
• Neutron-induced background by an α-beam incident on a deuterium gas target and its implications for the study of the 2 H(α,γ)6 Li reaction at LUNA. Eur. Phys. J. A 49, 28 (2013)
  M. Anders, D. Trezzi, A. Bellini, M. Aliotta, D. Bemmerer, C. Broggini, A. Caciolli, H. Costantini, P. Corvisiero, T. Davinson, Z. Elekes, M. Erhard, A. Formicola, Zs. Fülöp, G. Gervino, A. Guglielmetti, C. Gustavino, Gy. Gyürky, M. Junker, A. Lemut, M. Marta, C. Mazzocchi, R. Menegazzo, P. Prati, C. Rossi Alvarez, D. Scott, E. Somorjai, O. Straniero, and T. Szücs
  
• The resonance triplet at Eα = 4.5 MeV in the 40 Ca(α,γ)44 Ti reaction. Phys. Rev. C. 88, 025803 (2013)
  K. Schmidt, S. Akhmadaliev, M. Anders, D. Bemmerer, K. Boretzky, A. Caciolli, D. Degering, M. Dietz, R. Dressler, Z. Elekes, Z. Fülöp, G. Gyürky, R. Hannaske, A. Junghans, M. Marta, M. Menzel, F. Munnik, D. Schumann, R. Schwengner, T. Szücs, A. Wagner, D. Yakorev, and K. Zube
  
• A new study of the 22 Ne(p,γ)23 Na reaction deep underground: Feasibility, setup, and first observation of the 186 keV resonance. Eur. Phys. J. A 50, 179 (2014)
  F. Cavanna, R. Depalo, M. -L. Menzel, M. Aliotta, M. Anders, D. Bemmerer, C. Broggini, C. G. Bruno, A. Caciolli, P. Corvisiero, T. Davinson, A. di Leva, Z. Elekes, F. Ferraro, A. Formicola, Zs. Fülöp, G. Gervino, A. Guglielmetti, C. Gustavino, Gy. Gyürky, G. Imbriani, M. Junker, R. Menegazzo, P. Prati, C. Rossi Alvarez, D. A. Scott, E. Somorjai, O. Straniero, F. Strieder, T. Szücs, D. Trezzi
  (See online at https://doi.org/10.1140/epja/i2014-14179-5)
• First direct measurement of the 2 H(α,γ)6 Li cross section at Big Bang energies and the impact on the primordial lithium problem. Phys. Rev. Lett. 113, 042501 (2014)
  M. Anders, D. Trezzi, R. Menegazzo, M. Aliotta, A. Bellini, D. Bemmerer, C. Broggini, A. Caciolli, H. Costantini, P. Corvisiero, T. Davinson, Z. Elekes, M. Erhard, A. Formicola, Zs. Fülöp, G. Gervino, A. Guglielmetti, C. Gustavino, Gy. Gyürky, M. Junker, A. Lemut, M. Marta, C. Mazzocchi, P. Prati, C. Rossi Alvarez, D. Scott, E. Somorjai, O. Straniero, and T. Szücs
  (See online at https://doi.org/10.1103/PhysRevLett.113.042501)
• Strength of the Ep = 1.842 MeV resonance in the 40 Ca(p,γ)41 Sc reaction revisited. Phys. Rev. C 89, 045802 (2014)
  K. Schmidt, S. Akhmadaliev, M. Anders, D. Bemmerer, A. Caciolli, M. Dietz, Z. Elekes, A. Junghans, M. Menzel, R. Schwengner, A. Wagner, and K. Zuber
  (See online at https://doi.org/10.1103/PhysRevC.89.045802)
• The feasibility of direct measurements of the 44 Ti(α,p)47 V and 40 Ca(α,p)44 Ti reaction in forward kinematics at astrophysically relevant temperatures. Eur. Phys. J. A 50, 140 (2014)
  T. Al-Abdullah, S. Akhmadaliev, M. Ayranov, D. Bemmerer, R. Dressler, Z. Elekes, N. Kivel, K. Schmidt, D. Schumann, M. Sobiella, T. Stowasser, M.P. Takács and K. Zuber
  (See online at https://doi.org/10.1140/epja/i2014-14140-8)
• Underground study of the 17 O(p,γ)18 F reaction relevant for explosive hydrogen burning. Phys. Rev. C 89, 015803 (2014)
  A. Di Leva, D. A. Scott, A. Caciolli, A. Formicola, F. Strieder, M. Aliotta, M. Anders, D. Bemmerer, C. Broggini, P. Corvisiero, Z. Elekes, Zs. Fülöp, G. Gervino, A. Guglielmetti, C. Gustavino, Gy. Gyürky, G. Imbriani, J. José, M. Junker, M. Laubenstein, R. Menegazzo, E. Napolitani, P. Prati, V. Rigato, V. Roca, E. Somorjai, C. Salvo, O. Straniero, T. Szücs, F. Terrasi, and D. Trezzi
  (See online at https://doi.org/10.1103/PhysRevC.89.015803)