1. Commissioning of the n_TOF second experimental area at CERN 101 o Congresso Nazionale della Societa’ Italiana di Fisica, Roma, 21-25 Settembre 2015 Lucia Anna Damone, INFN Bari, on behalf of the n_TOF Collaboration

2. Outline The n_TOF project The facility Flux measurement Beam profile measurement Conclusions L. Damone, Commissioning of the n_TOF second experimental area at CERN, SIF 2015, Roma 21-25 Settembre 2015

3. The n_TOF Collaboration ~ 30 Institutions >100 Researchers + Newcomers High accuracy measurements of neutron induced reaction cross-sections (n,f), (n,cp), (n,  ) L. Damone, Commissioning of the n_TOF second experimental area at CERN, SIF 2015, Roma 21-25 Settembre 2015 CERN Technische Universitat Wien Austria IRMM EC-Joint Research Center, GeelBelgium IN2P3-Orsay, CEA-SaclayFrance KIT – Karlsruhe, Goethe University, FrankfurtGermany Univ. of Athens, Ioannina, DemokritosGreece INFN Bari, Bologna, LNL, LNS, Trieste, ENEA – BolognaItaly Tokyo Institute of Technology, JAEAJapan ITN LisbonPortugal Charles Univ. (Prague)Czech Republic Univ. of LodzPoland IFIN – BucarestRumania INR – Dubna *, IPPE – Obninsk * Russian Fed. CIEMAT, Univ. of Valencia, Santiago de Compostela, University of Cataluna, SevillaSpain University of Basel, PSISwitzerland Univ. of Manchester, Univ. of YorkUK

4. n_TOF measurements at glance Astrophysics Nuclear Astrophysics (stellar nucleosynthesis and BBN) Nuclear Astrophysics (stellar nucleosynthesis and BBN) Nuclear energy (fission products & Structural material) Nuclear energy (fission products & Structural material) Advanced nuclear reactors (actinides) Advanced nuclear reactors (actinides) L. Damone, Commissioning of the n_TOF second experimental area at CERN, SIF 2015, Roma 21-25 Settembre 2015

5. The n_TOF facility (1/2) L. Damone, Commissioning of the n_TOF second experimental area at CERN, SIF 2015, Roma 21-25 Settembre 2015 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 Main feature: extremely 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 EAR1

6. The n_TOF facility (2/2) 185 m 20 GeV/c protons 20 m Spallation Target EAR1 EAR2 L. Damone, Commissioning of the n_TOF second experimental area at CERN, SIF 2015, Roma 21-25 Settembre 2015 Experimental Area 2 (EAR2) is a new measuring station placed (vertically) at 20 m from 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! The huge gain in signal-to-background ratio in EAR2 allows to measure radioactive isotopes with half lives as low as a few days.

7. Commissioning of EAR2 L. Damone, Commissioning of the n_TOF second experimental area at CERN, SIF 2015, Roma 21-25 Settembre 2015 The new beam line has been characterized in terms of flux and beam profile by means of several detection systems, namely silicon based devices and gaseous detectors. The detectors are equipped with different neutron converters placed in front of the sensible layer or volume By combining the results of different detection system is possible to reach accuracy as low as few percent (or less). FUNDAMENTAL TO NORMALIZE DATA Reaction Energy range of standard

8. Setup for flux measurement @n_TOF-EAR2 L. Damone, Commissioning of the n_TOF second experimental area at CERN, SIF 2015, Roma 21-25 Settembre 2015 Si 6 LiF neutrons Si  t Silicon Monitor (SiMon2) LiF converter 105  g/cm 2 4 single pad silicon detectors 3x3 cm 2 MGAS detectors (LiF, 235 U, 10 B) few mm gas gap

9. Analisys details L. Damone, Commissioning of the n_TOF second experimental area at CERN, SIF 2015, Roma 21-25 Settembre 2015 GEANT4 simulation to determine efficiencySelection cuts to reject background events t 

10. Results for flux measurements L. Damone, Commissioning of the n_TOF second experimental area at CERN, SIF 2015, Roma 21-25 Settembre 2015 Agreement between detectors is being investigated and an official evaluation of the n_TOF flux in experimental area 2 is going to be released. At this stage of the analysis the agreement between detectors varies from 1% to 8%

11. Comparison neutron flux EAR2/EAR1 L. Damone, Commissioning of the n_TOF second experimental area at CERN, SIF 2015, Roma 21-25 Settembre 2015 x30 Possibility to study isotopes with very short half life (days)

12. Beam profile detector L. Damone, Commissioning of the n_TOF second experimental area at CERN, SIF 2015, Roma 21-25 Settembre 2015 The spatial distribution on neutrons as a function of energy has been measured by means of a double side silicon strip detector (DSSSD). 16 x 16 Si sensor strips 3 mm wide strips, 500  m thick 50 x 50 mm² X-Y grid LiF converter Selection of tritons

13. Beam profile measured L. Damone, Commissioning of the n_TOF second experimental area at CERN, SIF 2015, Roma 21-25 Settembre 2015 The neutron beam has a Gaussian profile in transversal plane.

14. Beam profile measured L. Damone, Commissioning of the n_TOF second experimental area at CERN, SIF 2015, Roma 21-25 Settembre 2015

15. Conclusions L. Damone, Commissioning of the n_TOF second experimental area at CERN, SIF 2015, Roma 21-25 Settembre 2015 There is need of accurate new data on neutron cross-section both for nuclear astrophysics and advanced nuclear technology (and nuclear medicine, fundamental physics..) Since 2001, n_TOF@CERN has provided an important contribution to the field, with an intense activity on capture, fission and n-charged particle measurements. A second new (and more intense flux) experimental area is now available. The commissioning of EAR2 has been performed in 2014, particularly in terms of energy and spatial distribution of neutrons. The measurements confirm the enhancement of flux in EAR2 with respect EAR1. EAR2 opens new perspectives for frontier measurements on short-lived radionuclides.