E.Chiaveri on behalf of the n_TOF Collaboration n_TOF Collaboration/Collaboration Board Lisbon, 13/15 December 2011 Proposal for Experimental Area 2(EAR-2) Scientific Motivation

Scientific Case for EAR-2 Astrophysical Research Nuclear Technology Application Basic Nuclear Research List of Examples of EAR-2 Proposals n_TOF Collaboration/Collaboration Board Lisbon, 13/15 December

EAR-2 Experiments Experiments in EAR-2 can be performed : on very small samples (important to reduce mass of unstable samples and in cases where sample material is limited) on isotopes with very small cross sections (where signal/background ratio is crucial) in much shorter time (measurements can be eventualy repeated to reduce systematic uncertainties) Measurements of neutron-induced cross sections at high energies (E n > MeV), which are not possible in the existing EAR-1, will benefit from largely reduced the  -flash. n_TOF Collaboration/Collaboration Board Lisbon, 13/15 December 2011

EAR-2 Nuclear Transmutation From the transmutation projects (or future generation nuclear energy systems), the EAR2 would allow to measure the fission cross-section of Pu isotopes and minor actinides with half lives of a few tens of years. Although short lived, it may be convenient to burn those actinides in future systems (either ADS or Gen IV fast reactors), together with their neighboring long-lived isotopes. Important Candidates: Fission Cross Section :238Pu (87.7 y)/241Pu (14.1 y) 244Cm(18.1 y) 242mAm(141y) 243Cm (29.1y) Capture Cross Section : 242Am (141 y)/ 243Cm (29.1 y) 231Pa(32400 y) N.Colonna n_TOF Collaboration/Collaboration Board Lisbon, 13/15 December 2011

EAR-2: Nuclear Astrophysics Nucleosynthesis by the slow neutron capture process represents a unique tool for studying the related abundances through the tight correlation with the experimental (n,  ) cross sections. The EAR-2 options for measurements of so far inaccessible reaction rates will provide a boost for our understanding of neutron capture nucleosynthesis during the He burning phases of stellar evolution, which played a crucial role in the history of the Universe, because they contributed half of the abundances between Fe and Bi. important candidates for EAR-2: 79 Se, 90 Sr, 93 Zr, 107 Pd, 135 Cs, 147 Pm, 163 Ho, 171 Tm, 182 Hf, 204 Tl n_TOF Collaboration/Collaboration Board Lisbon, 13/15 December 2011 F. Kaeppeler

 very small samples unstable isotopes along the reaction path of the slow neutron capture process (s process*), which give rise to local branchings in the reaction path; (n,  ) cross sections of branch point isotopes are needed for analysis of abundance pattern to deduce information on neutron flux, pressure, and temperature of stellar plasma * responsible for half of the abundances between Fe and Bi. important candidates for EAR-2: 79 Se, 90 Sr, 93 Zr, 107 Pd, 135 Cs, 147 Pm, 163 Ho, 171 Tm, 182 Hf, 204 Tl The EAR-2 window to stellar nucleosynthesis: s-process branchings F. Kaeppeler n_TOF Collaboration/Collaboration Board Lisbon, 13/15 December 2011

 very small cross sections neutron magic isotopes exhibit particularly small (n,  ) cross sections and act therefore as bottle necks for the reaction flow; present data are too uncertain and need significant improvement isotopes between C and Si represent crucial neutron poisons because their small cross sections are balanced by their high abundances; present data by far not sufficient important candidates for EAR-2: 86 Kr, 88 Sr, 138 Ba, 140 Ce, 208 Pb; isotopes of C, O, Ne, Mg The EAR-2 window to stellar nucleosynthesis: neutron magic isotopes F. Kaeppeler n_TOF Collaboration/Collaboration Board Lisbon, 13/15 December 2011

 short measuring times isotopes of pure s-process origin (which are shielded by stable isobars against contributions from the r process) are important constraints for model predictions of the s-abundance distribution and have, therefore, to be known with an accuracy of less than 2% (so far achieved only for about half of the s-only isotopes); to reach this accuracy, systematic effects have to be studied in repeated measurements with different experimental conditions important candidates for EAR-2: 64 Zn, 70 Ge, 76 Ge, 80,82 Kr, 86,87 Sr, 95,96 Mo, 104 Pd, 164,166 Er, 198 Hg The EAR-2 window to stellar nucleosynthesis: s-only isotopes F. Kaeppeler n_TOF Collaboration/Collaboration Board Lisbon, 13/15 December 2011

Basic Nuclear Research n_TOF Collaboration/Collaboration Board Lisbon, 13/15 December 2011 Neutron-induced reactions measured with the time- of-flight technique form a unique tool to investigate nuclear structure at high excitation energies by observing resolved nuclear levels that are revealed by resonances in the reaction yields Neutron resonance spectroscopy is used to obtain crucial information on level densities in the vicinity of the neutron binding energy, i.e. at several MeV above the ground state A large number of level density models exist which are all calibrated by the level density observed with neutron resonances

Basic Nuclear Research n_TOF Collaboration/Collaboration Board Lisbon, 13/15 December 2011  Example of the observation of nuclear levels in neutron-induced experiments.  Tthe total cross section is shown as a function of neutron energy for several nuclei with increasing mass ranging from 6 Li to 241 Am

LIST OF EXAMPLES OF EAR-2 PROPOSALS n_TOF Collaboration/Collaboration Board Lisbon, 13/15 December 2011 Simultaneous measurements of capture and fission cross sections of fissile Pu isotopes 239,240Pu (n,g), (n,f) isotopes Measurement of the 25 Mg(n,α) 22 Ne cross section Simultaneous measurements of capture and fission cross sections of 238 Pu and 244 Cm Simultaneous measurements of capture and fission cross sections of 245 Cm Measurements of (n,xn) reaction cross sections for heavy target nuclei Fission cross section of the 230 Th(n,f) reaction Neutron capture measurement of the s-process branching point 79 Se Cross section and angular distribution of fragments from neutron-induced fission of 232 U

EAR-2 proposal 1 n_TOF Collaboration/Collaboration Board Lisbon, 13/15 December 2011

EAR-2 proposal 2 n_TOF Collaboration/Collaboration Board Lisbon, 13/15 December 2011

EAR-2 proposal 3 n_TOF Collaboration/Collaboration Board Lisbon, 13/15 December 2011

EAR-2 proposal 4 n_TOF Collaboration/Collaboration Board Lisbon, 13/15 December 2011

EAR-2 proposal 5 n_TOF Collaboration/Collaboration Board Lisbon, 13/15 December 2011

EAR-2 proposal 6 n_TOF Collaboration/Collaboration Board Lisbon, 13/15 December 2011

EAR-2 proposal 7 n_TOF Collaboration/Collaboration Board Lisbon, 13/15 December 2011

EAR-2 proposal 8 n_TOF Collaboration/Collaboration Board Lisbon, 13/15 December 2011