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2 fundamental nuclear physics Get information about the mere nuclear interaction NEUTRON INDUCED REACTIONS Nuclear tecnologies Nuclear Waste trasmutation Energy production Nuclear Astrophysics Nucleosynthesis of the elements heavier than Fe abundance of some light nuclides modified by (n,γ), (n,p) and (n,α) reactions during the s- or r-processes or explosive nucleosynthesis
3 non monocromatic beam TOF technique neutron energy spectra which simulate a stellar (kt 25 kev) Maxwell-Boltzmann distribution (e.g. 7 Li(p,n) 7 Be ) The on-line detection of the reaction products is often limited by high neutron fluxes. Background subtraction Normalization of the cross section Security problems USE OF an indirect technique Several IM have been developped for nuclear astrophysics, like CD, ANC and THM
4 USE OF THE QUASI- FREE BREAK-UP OF DEUTERON TO PRODUCE A VIRTUAL NEUTRON BEAM Advantages: 1. Get complementary information about the cross section of reactions induced by neutrons 2. Overcome the suppression due to the possible presence of centrifugal barrier 3. Allow to measure the neutron induced reaction on radioactive nuclei with low life time (minutes or less) by using the Radioactive ions beams
5 n α p USE OF THE QUASI-FREE BREAK-UP OF DEUTERON TO PRODUCE A VIRTUAL NEUTRON SOURCE To be used also with radioactive ion beams 2-bodies reaction 6 Li(n,α) 3 H d 3 σ de b dω b dω B KF Φ p s dω ( ) 2 dσ d( 6 Li,α 3 H)p 3-bodies reaction
6 6 Li(n,α) 3 H d( 6 Li,α 3 H)p First run @LNS parassitic experiment good agreement but low energy resolution Second run @LNS devoted experiment 17 O(n,α) 14 C d( 17 O,α 14 C)p First run @LNS parassitic experiment Second run @ND devoted experiment Cross section (barn) Cross section (barn) -1-2 -3 1-1 1 Incident energy (MeV) -6-4 -2
7 Experiment performed @LNS,Catania CD2 α 18-28 6Li beam@14mev DE E-PSD t 43-53 40 <θ cm <70 The directly measured cross section is integrated over the same θ cm angular region and is averaged out at the same energy resolution of 120 kev Eur. Phys. Jour. A, 25, 649 Volume: 25, 649-650 (2005)
The new set-up 6Li beam@17mev CD2 Resolution of 30 kev in 6Li-n relative energy α 22-26 E-PSD 95 <θ cm <1 Data correction for the penetrability of the centrifugal barrier t 36-40 N dσ dω = C dσ N P dω l J. of Phys. G, Nucl. Part.Phys. 37, 1255 (20)
9 NUCLEAR REACTORS the neutron induced reaction on 14 N and 17 O are the dominant sources of the radioactive isotope 14 C (T 1/2 = 5730 yr). NUCLEAR ASTROPHYSICS In the inhomogeneous big-bang model the 14 C may act as a bottleneck in the production of elements heavier than A=17 anomalies in 18 O/ 16 O and 17 O/ 16 O ratios found in asymptotic giant branch stars and in circumstellar Al 2 O 3 meteorite grains neutron poison in the nucleosynthesis of the s-process elements
14 N+α+n 17 O+p 14 N+α Two experiments were performed @LNS - Catania, Italy 17 O+d @NSL Notre Dame, IN, USA 14 C+α+p 17 O+n 14 C+α EXPERIMENTAL SET-UP 17 O @ 41 MeV PSD CD2 IC
11 Indentification of the reaction channel 17 O(n,α) 14 C O N C d( 17 O,α 14 C)p
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13 ) (arb. units) 18 O =8.038 MeV E 18 O =8.125 MeV E 18 O =8.213 MeV E 18 O =8.282 MeV E (a) xs ) yield / ( KF (p 2 E 18 O =8.038 MeV E 18 O =8.125 MeV -0-50 0 50 0 150 200 250 300 E c.m. (kev) PHYSICAL REVIEW C 87, 012801(R) (2013) E 18 O =8.213 MeV E 18 O =8.282 MeV (b) Cross section (barn) -1-2 -3-6 -4-2 Energy (MeV)
14 E = 8.038 MeV l i =1 l i =3 l i =0, l i =2 (arb. units) 0 E = 8.125 MeV l i =3 l i =1 l i =1 d / dcos c.m. 0 E = 8.213 MeV l i =0 l i =2 0 E = 8.282 MeV l i =1 0-1 -0.5 0 0.5 1 cos c.m. PHYSICAL REVIEW C 87, 012801(R) (2013)
15 5 4 =8.213 MeV 18O E =8.282 MeV 18O E Data correction for the penetrability of the centrifugal barrier dσ dω = C dσ P dω l N N < > (mb) 2 1-2 =8.125 MeV 18O E -4 0 0 200 300 E c.m. (kev) PHYSICAL REVIEW C 87, 012801(R) (2013)
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