Neutron cross-sections measurement at the facility at CERN Students’coffee – 26th meeting, Tuesday 28 October 2014, D02-BE Auditorium Prevessin Massimo Barbagallo, CERN/EN-STI and INFN

Outline M. Barbagallo, Students’Coffee, 28 October 2014, Neutron cross-sections measurement at the n_TOF facility at CERN Motivations (Nuclear Astrophysics, Nuclear Technology, Nuclear Medicine, Nuclear Structure ) The facility(ies) and the experimental program so far (extremely short review) Experimental Area 2 Perspectives Conclusions

36 Institutions 120 Researchers High accuracy and precision measurements of neutron induced reaction cross-sections (n,f), (n,cp), (n,  ) n_TOF Collaboration M. Barbagallo, Students’Coffee, 28 October 2014, Neutron cross-sections measurement at the n_TOF facility at CERN

n_TOF measurements at a glance M. Barbagallo, Students’Coffee, 28 October 2014, Neutron cross-sections measurement at the n_TOF facility at CERN Astrophysics Nuclear Astrophysics (stellar nucleosynthesis) Nuclear Astrophysics (stellar nucleosynthesis) Nuclear energy (fission products & Structural material) Nuclear energy (fission products & Structural material) Advanced nuclear reactors (actinides) Advanced nuclear reactors (actinides) Nuclear Medicine (capture therapy) Nuclear Medicine (capture therapy)

n_TOF facility (beam line 1+ EAR1) M. Barbagallo, Students’Coffee, 28 October 2014, Neutron cross-sections measurement at the n_TOF facility at CERN PS 20 GeV Linac 50 MeV Booster 1.4 GeV 185 m flight path n_TOF is a spallation neutron source based on 20 GeV/c protons from the CERN PS hitting a Pb block (~360 neutrons per proton). Experimental area at 185 m.

n_TOF EAR1 features M. Barbagallo, Students’Coffee, 28 October 2014, Neutron cross-sections measurement at the n_TOF facility at CERN Other features of the neutron beam: high resolution in energy (  E/E = )study resonances Wide energy range (25 meV<E n <1 GeV)measure fission up to 1 GeV low repetition rate (< 0.8 Hz) no wrap-around Main feature: high instantaneous neutron flux (10 5 n/cm 2 /pulse). very convenient for measurements of radioactive isotopes, low cross sections, Isotope available in small quantity Advantages of the PS proton beam: high energy, high peak current, low duty cycle. C. Guerrero et al., Eur. Phys. J. A (2012) 48:29

n_TOF facility (beam line 1+ EAR1) M. Barbagallo, Students’Coffee, 28 October 2014, Neutron cross-sections measurement at the n_TOF facility at CERN

Detection systems at n_TOF C 12 H 20 O 4 ( 6 Li) 2 Neutron beam (n,  ) C6D6C6D6 TAC (n,f), (n,cp) M. Barbagallo, Students’Coffee, 28 October 2014, Neutron cross-sections measurement at the n_TOF facility at CERN FIC PPAC MGAS..and many others

n+ 197 Au M. Barbagallo et al., Eur. Phys. J. A (2013) 49:156 Road to a cross section.. M. Barbagallo, Students’Coffee, 28 October 2014, Neutron cross-sections measurement at the n_TOF facility at CERN

The experimental program so far M. Barbagallo, Students’Coffee, 28 October 2014, Neutron cross-sections measurement at the n_TOF facility at CERN Capture 151 Sm 232 Th 204,206,207,208 Pb, 209 Bi 24,25,26 Mg 90,91,92,94,96 Zr, 93 Zr 186,187,188 Os 233,234 U 237 Np, 240 Pu, 243 Am Fission 233,234,235,236,238 U 232 Th 209 Bi 237 Np 241,243 Am, 245 Cm Capture 25 Mg 88 Sr 58,60,62 Ni, 63 Ni 54,56,57 Fe, 238 U 241 Am Fission 240,242 Pu 235 U(n,  /f) 232 Th, 234 U 237 Np (FF ang.distr.) (n,  ) 33 S, 59 Ni Phase 1 ( ) Phase 2 ( ) 236 U

63 Ni(n,  ) M. Barbagallo, Students’Coffee, 28 October 2014, Neutron cross-sections measurement at the n_TOF facility at CERN 63 Ni (t 1/2 =100 y) represents the first branching point in the s- process, and determines the abundance of 63,65 Cu First high-resolution measurement of 63 Ni(n,  ) in the astrophysical energy range. 62 Ni sample (1g) irradiated in thermal reactor (1984 and 1992), leading to enrichment in 63 Ni of ~13 % (131 mg) In 2011 ~15.4 mg 63 Cu in the sample (from 63 Ni decay). After chemical separation at PSI, 63 Cu contamination <0.01 mg

M. Barbagallo, Students’Coffee, 28 October 2014, Neutron cross-sections measurement at the n_TOF facility at CERN 197 Au(n,  ) cross section is a standard at thermal energy and in the energy range MeV In order to possibly extend the standard also to the Resolved Resonance Region (few eV – few keV) it has been measured at n_TOF both with C 6 D 6 and TAC. C. Massimi et al., Phys. Rev. C 81, (2010) 197 Au(n,  )

M. Barbagallo, Students’Coffee, 28 October 2014, Neutron cross-sections measurement at the n_TOF facility at CERN T. Wright, Univ. of Manchester, PhD thesis Overall (expected): 2-3% systematic uncertainty (depending on E n ) 238 U sample (provided by JRC-IRMM) (2) g High purity (99.99%) Rectangular: x mm Used C 6 D 6 and TAC to minimize systematic uncertainty related to detection effects NEA request to measure 238 U(n,  ) cross section with 2% accuracy from 100 eV to 25 keV F. Mingrone, Univ. of Bologna, PhD thesis Response from the community: measurements at n_TOF (x2), GELINA and LANSCE 238 U(n,  )

n_TOF history M. Barbagallo, Students’Coffee, 28 October 2014, Neutron cross-sections measurement at the n_TOF facility at CERN Concept by C.Rubbia CERN/ET/Int. Note Commissioning Construction started 1999 New Target installed Phase I Measurement campaign 63 Ni 62 Ni Phase II Measurement campaign Commissioning nd Exp. area 2014 Upgrades 10 B-water Class-A area 2010 Phase III

n_TOF history M. Barbagallo, Students’Coffee, 28 October 2014, Neutron cross-sections measurement at the n_TOF facility at CERN n_TOF Experimental Area 2 20 m Beam line Spallation target Higher fluence, by a factor of 30, relative to EAR1. The shorter flight path implies a factor of 10 smaller time-of-flight. Global gain by a factor of 300 in the signal/background ratio for radioactive isotopes! 200 m Beam line x30 Experimental Area 2 (EAR2) is placed (vertically) at 20m from spallation target.

M. Barbagallo, Students’Coffee, 28 October 2014, Neutron cross-sections measurement at the n_TOF facility at CERN n_TOF Experimental Area 2 EAR2 neutrons EAR1 neutrons The new facility is presently undergoing the commissioning phase, particularly in terms of neutron flux and background. First Physics experiment 240 Pu(n,f) will start in few weeks.

M. Barbagallo, Students’Coffee, 28 October 2014, Neutron cross-sections measurement at the n_TOF facility at CERN Neutron measurement Si neutrons Transparent neutron monitor Array of four 3x3 cm 2 silicon detectors (300  m thickness) 6 LiF converter (420  g/cm 2 ) 6 LiF t  neutron energy (eV) Energy deposited (MeV) detectors converter tt

M. Barbagallo, Students’Coffee, 28 October 2014, Neutron cross-sections measurement at the n_TOF facility at CERN Neutron PRELIMINARY x35 x20

M. Barbagallo, Students’Coffee, 28 October 2014, Neutron cross-sections measurement at the n_TOF facility at CERN EAR1 EAR2 Perspectives

M. Barbagallo, Students’Coffee, 28 October 2014, Neutron cross-sections measurement at the n_TOF facility at CERN 7 Be: the Phisycs case Bing Bang Nucleosynthesis (BBN), together with Hubble expansion and Cosmic Microwave Background Radiation is one of the cornerstones for Bing Bang Theory. BBN gives the sequence of nuclear reactions leading to the synthesis of light elements up to Na* in the early stage of Universe ( sec)

BBN successfully predicts the abundances of primordial elements such as 4 He, D and 3 He. * R.H.Cyburt et al., Journal of Cosmology and Astroparticle Physics 11 (2008) 012 * ** A.Coc et al., The Astrophysical Journal, 744:158 (2012) A serious discrepancy (factor 2-4) between the predicted abundance of 7 Li and the value inferred by measurements (Spite et al, many others.) Cosmological Lithium Problem (CLiP) M. Barbagallo, Students’Coffee, 28 October 2014, Neutron cross-sections measurement at the n_TOF facility at CERN 7 Be: the Phisycs case

Approximately 95% of primordial 7 Li is produced from the electron capture decay of 7 Be (T 1/2 =53.2 d). A higher destruction rate of 7 Be can solve or at least partially explain the CLiP. 7 Be is destroyed via (n,p) (~97%) and (n,  ) (~2.5%) reactions M. Barbagallo, Students’Coffee, 28 October 2014, Neutron cross-sections measurement at the n_TOF facility at CERN 7 Be(n,p) 7 Be(n,  ) 7 Be: the Phisycs case

7 Be(n,  ) and 7 M. Barbagallo, Students’Coffee, 28 October 2014, Neutron cross-sections measurement at the n_TOF facility at CERN We plan to measure both 7 Be(n,  ) and 7 Be(n,p) reactions at n_TOF-EAR2.* Taking advantage of the: extremely high instantaneous neutron flux state of art detectors and acquisition systems high purity samples (PSI+ISOLDE) First high accuracy measurement!** (**in all the neutron energy range) 7 Be(n,  ), 1 months measurement 7 Be(n,p), <2 weeks measurement *M. Barbagallo et al., CERN-INTC / INTC-P-417

M. Barbagallo, Students’Coffee, 28 October 2014, Neutron cross-sections measurement at the n_TOF facility at CERN Conclusions There is need of accurate new data on neutron cross-section both for astrophysics and advanced nuclear technology, as well as for nuclear medicine. Since 2001, has provided an important contribution to the field, with an intense activity on capture and fission measurements. Several results of interest for stellar nucleosynthesis (Sm, Os, Zr, Ni, Fe, etc…). Important data on actinides, of interest for nuclear waste transmutation. To date, high resolution measurements performed in EAR1 in optimal conditions (borated water moderator, Class-A experimental area, etc…). A second new (and more intense flux) experimental area is now available. EAR2 will open new perspectives for frontier measurements on short-lived radionuclides. A rich experimental program is foreseen both in EAR1 and EAR2 for nuclear technologies, nuclear astrophysics and nuclear medicine.

M. Barbagallo, Students’Coffee, 28 October 2014, Neutron cross-sections measurement at the n_TOF facility at CERN Thanks for your kind attention! …and come to visit n_TOF at any time!