Eur. Phys. J. A (2013) 49: 156
https://doi.org/10.1140/epja/i2013-13156-x

Special Article - Tools for Experiment and Theory

High-accuracy determination of the neutron flux at n_TOF

¹ INFN, Sezione di Bari, V. Orabona 4, 70125, Bari, Italy
² European Organization for Nuclear Research (CERN), Geneva, Switzerland
³ National Technical University of Athens (NTUA), Athens, Greece
⁴ Universidade de Santiago de Compostela, Santiago, Spain
⁵ Johann-Wolfgang-Goethe Universität, Frankfurt, Germany
⁶ Uniwersytet Łódzki, Lodz, Poland
⁷ Centre National de la Recherche Scientifique/IN2P3 - IPN, Orsay, France
⁸ Centro de Investigaciones Energeticas Medioambientales y Tecnológicas (CIEMAT), Madrid, Spain
⁹ Charles University, Prague, Czech Republic
¹⁰ Commissariatà l’Energie Atomique (CEA) Saclay - Irfu, Gif-sur-Yvette, France
¹¹ University of Manchester, Oxford Road, Manchester, UK
¹² Department of Physics, Faculty of Science, University of Zagreb, Zagreb, Croatia
¹³ Universitat Politecnica de Catalunya, Barcelona, Spain
¹⁴ Instituto Tecnológico e Nuclear, Instituto Superior Técnico, Universidade Técnica de Lisboa, Lisboa, Portugal
¹⁵ Universidad de Sevilla, Sevilla, Spain
¹⁶ Instituto de Física Corpuscular, CSIC-Universidad de Valencia, Valencia, Spain
¹⁷ Paul Scherrer Institut, Villigen PSI, Switzerland
¹⁸ INFN, Laboratori Nazionali di Legnaro, Rome, Italy
¹⁹ Aristotle University of Thessaloniki, Thessaloniki, Greece
²⁰ Bhabha Atomic Research Centre (BARC), Mumbai, India
²¹ Atominstitut, Technische Universität Wien, Wien, Austria
²² University of York, Heslington, York, UK
²³ Karlsruhe Institute of Technology, Campus Nord, Institut für Kernphysik, Karlsruhe, Germany
²⁴ Oak Ridge National Laboratory (ORNL), TN 37831, Oak Ridge, USA
²⁵ Faculty of Physics, University of Vienna, Vienna, Austria
²⁶ Dipartimento di Fisica, Università di Bologna, and INFN, Sezione di Bologna, Bologna, Italy
²⁷ Agenzia nazionale per le nuove tecnologie, l’energia e lo sviluppo economico sostenibile (ENEA), Bologna, Italy
²⁸ INFN, Sezione di Trieste, Trieste, Italy
²⁹ Horia Hulubei National Institute of Physics and Nuclear Engineering - IFIN HH, Bucharest - Magurele, Romania
³⁰ European Commission JRC, Institute for Reference Materials and Measurements, Retieseweg 111, B-2440, Geel, Belgium
³¹ Department of Physics and Astronomy, University of Basel, Basel, Switzerland
³² Laboratori Nazionali del Gran Sasso dell’INFN, Assergi (AQ), Italy

^* e-mail: massimo.barbagallo@ba.infn.it

Received: 16 May 2013
Revised: 1 November 2013
Accepted: 3 December 2013
Published online: 18 December 2013

Abstract

The neutron flux of the n_TOF facility at CERN was measured, after installation of the new spallation target, with four different systems based on three neutron-converting reactions, which represent accepted cross sections standards in different energy regions. A careful comparison and combination of the different measurements allowed us to reach an unprecedented accuracy on the energy dependence of the neutron flux in the very wide range (thermal to 1 GeV) that characterizes the n_TOF neutron beam. This is a pre-requisite for the high accuracy of cross section measurements at n_TOF. An unexpected anomaly in the neutron-induced fission cross section of ²³⁵U is observed in the energy region between 10 and 30keV, hinting at a possible overestimation of this important cross section, well above currently assigned uncertainties.