Direct measurements for nuclear astrophysics at deep under Coulomb barrier D. Tudor1, A.I. Chilug1, I.C. Stefanescu1, M. Straticiuc1, I. Burducea1, L. Trache1, I.M. Focsa1, D.G. Ghita1, R. Margineanu1, A. Pantelica1, C. Gomoiu1 and N.T. Zhang2, X. Tang2, H. Chen2 1Horia Hulubei National Institute for R&D in Physics and Nuclear Engineering, Bucharest, Romania 2Institute of Modern Physics, Lanzhou, China

Outline: Motivation The 13C+12C Experiment ( Activation Measurements) Results Conclusions Young Researchers Session in IFIN-HH 20 Dec. 2016

Motivation 3 MV Tandetron accelerator! Test of possibilities for direct measurements in nuclear astrophysics at IFIN-HH, using the: 3 MV Tandetron accelerator! Ultra low background at Bq laboratory (in salt mine)! The Objectives: Certify the absolute values of the cross sections measured by further testing calibrations. Determine the relative contribution of the channels: activation vs. total at a few energies by measuring prompt gamma rays and activation gamma rays. Extend the measurements to lower energies using the microBq lab. In collaboration with IMP – Lanzhou. Young Researchers Session in IFIN-HH 20 Dec. 2016

The 13C+12C Experiment proposed tests using 13C+12C,measured in Important reaction in nuclear astrophysics: 12C+12C Very difficult to measure, cross section fluctuating due to resonances! No resonances observed in 13C+12C! Obs: for most energies, the 12C+12C cross sections are suppressed! Only at resonant energies, the 12C+12C cross sections match with those of 12C+13C and 13C+13C! proposed tests using 13C+12C,measured in the Gamow window Young Researchers Session in IFIN-HH 20 Dec. 2016

The 13C+12C Experiment 13C2+, 3+ beam 4- 15 pA 13C beam energy 11 – 4.6 MeV (Ecm=5,3 – 2.2 MeV), in steps of 0.2 MeV 24Na:T1/2 =15 hr 12C(13C,p) 24Na 13C2+, 3+ beam 4- 15 pA Eg=1369, 2754 keV Young Researchers Session in IFIN-HH 20 Dec. 2016

The 13C+12C Experiment Offline γ-ray technique Young Researchers Session in IFIN-HH 20 Dec. 2016

Background and Detection efficiencies R. Margineanu et al., Applied Radiation and Isotopes 66, 1501-1506, 2008. Young Researchers Session in IFIN-HH 20 Dec. 2016

Background and Detection efficiencies The detectors were calibrated in efficiency using sources with well-known activities, like: 153Eu, 133Ba60Co, 137Cs, 241Am. Young Researchers Session in IFIN-HH 20 Dec. 2016

Experimental cross section     Young Researchers Session in IFIN-HH 20 Dec. 2016

Experimental cross section Activities of irradiated targets measured both in the underground and surface laboratories allowed to determine the limit of detection of cross sections to be of the order of 90 pb. Essentially, we found that we could increase the sensitivity of these measurements by about a factor 100 compared with best world results. Young Researchers Session in IFIN-HH 20 Dec. 2016

Astrophysical S(E) factor S(E)=σ(E)*E*exp(2πη) Young Researchers Session in IFIN-HH 20 Dec. 2016

CONCLUSIONS We studied the 12C+13C fusion reaction in the energy range Ec.m.= 2.3 – 5.3 MeV using the activation method and prompt gamma-rays spectroscopy. Our conclusions are: Measurements at GammaSpec, NAG and at μBq are consistent in absolute values. The proton yields from activation and from in-beam measurements are consistent for the overlap energies (see Stefanescu presentation). The values for total fusion cross section presented in this paper are not the final ones. For the final values we need to do Hauser Feshbach model calculations Activities of irradiated targets measured both in the underground and surface laboratories allowed to determine the limit of detection of cross sections to be of the order of 90 pb. Essentially, we found that we could increase the sensitivity of these measurements by about a factor 100 compared with best world results

The 64Zn(α,p)67Ga reaction Natural zinc targets 64Zn(α,p)67Ga   64Zn(α,p)67Ga Young Researchers Session in IFIN-HH 20 Dec. 2016

References Young Researchers Session in IFIN-HH 20 Dec. 2016 [1] Claus E. Rolfs and William S. Rodney, Cauldrons in the Cosmos, University Of Chicago Press, Chicago, 580 p [2] X. Fang et al., Journal of Physics: Conference Series 420, 012151, 2013 [3] I. Burducea, M. Straticiuc, D.G. Ghita, D.V. Mosu, C.I. Calinescu, N.C. Podaru, D.J.W. Mous, I. Ursu, N.V. Zamfir, Nuclear Instruments and Methods in Physics Research B 359, 1219, 2015. [4] D. Chesneanu, L. Trache, R. Margineanu, A. Pantelica, D. Ghita, M. Straticiuc, I. Burducea, A. M. Blebea-Apostu, C. M. Gomoiu, and X. Tang, AIP Conference Proceedings 1645, 311 (2015). [5] R. Margineanu, C. Simion, S. Bercea, O.G. Duliu, D. Gheorghiu, A. Stochioiu, M. Matei, Applied Radiation and Isotopes 66, 1501-1506, 2008. [6] D. Tudor, A.I. Chilug, M. Straticiuc, L. Trache et al., in C. Spitaleri, L. Lamia and G.R. Pizzone (eds.), Proceedings of the 8th European Summer School of Physics on Experimental Nuclear Astrophysics (Santa Tecla School), J. of Phys: Conf Series, vol. 703 (2016) 012028. [7] R.A.Dayras, R.G. Stokstad, Z.E.Switkowski and R.M.Wieland, Nuclear Physics A 625, 152-188, 1976 Young Researchers Session in IFIN-HH 20 Dec. 2016

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