Eur. Phys. J. A (2026) 62: 33
https://doi.org/10.1140/epja/s10050-026-01788-6

Regular Article - Experimental Physics

Radiative neutron capture cross section of $_{}^{242}$Pu measured at n_TOF-EAR1 in the unresolved resonance region up to 600 keV

¹ Dpto. Fisica Atómica, Molecular y Nuclear, Universidad de Sevilla, Seville, Spain
² Instituto de Física Corpuscular, CSIC-Universidad de Valencia, Valencia, Spain
³ Centro de Investigaciones Energéticas Medioambientales y Tecnológicas (CIEMAT), Madrid, Spain
⁴ Johannes Gutenberg-Universität Mainz, 55128, Mainz, Germany
⁵ Helmholtz-Zentrum Dresden-Rossendorf, 01328, Dresden, Germany
⁶ European Organization for Nuclear Research (CERN), Geneva, Switzerland
⁷ University of Lodz, Lodz, Poland
⁸ Institut de Physique Nucléaire, CNRS-IN2P3, Univ. Paris-Sud, Université Paris-Saclay, 91406, Orsay Cedex, France
⁹ TU Wien, Atominstitut, Stadionallee 2, 1020, Wien, Austria
¹⁰ Istituto Nazionale di Fisica Nucleare, Sezione di Bari, Bari, Italy
¹¹ Instituto Superior Técnico, Lisbon, Portugal
¹² Charles University, Prague, Czech Republic
¹³ Goethe University Frankfurt, Frankfurt am Main, Germany
¹⁴ CEA Irfu, Université Paris-Saclay, 91191, Gif-sur-Yvette, France
¹⁵ University of Manchester, Manchester, UK
¹⁶ Department of Physics, Faculty of Science, University of Zagreb, Zagreb, Croatia
¹⁷ University of Santiago de Compostela, Santiago, Spain
¹⁸ Universitat Politècnica de Catalunya, Barcelona, Spain
¹⁹ Agenzia nazionale per le nuove tecnologie, l’energia e lo sviluppo economico sostenibile (ENEA), Rome, Italy
²⁰ Istituto Nazionale di Fisica Nucleare, Sezione di Bologna, Bologna, Italy
²¹ INFN Laboratori Nazionali del Sud, Catania, Italy
²² Dipartimento Interateneo di Fisica, Università degli Studi di Bari, Bari, Italy
²³ Paul Scherrer Institut (PSI), Villigen, Switzerland
²⁴ Affiliated with an institute covered by a cooperation agreement with CERN, Geneva, Switzerland
²⁵ Horia Hulubei National Institute of Physics and Nuclear Engineering, Mǎgurele, Romania
²⁶ Institute of Physics and Power Engineering (IPPE), Obninsk, Russia
²⁷ Japan Atomic Energy Agency (JAEA), Tokai-Mura, Japan
²⁸ European Commission, Joint Research Centre (JRC), Geel, Belgium
²⁹ University of York, York, UK
³⁰ Karlsruhe Institute of Technology, Campus North, IKP, 76021, Karlsruhe, Germany
³¹ Tokyo Institute of Technology, Meguro, Japan
³² National Technical University of Athens, Athens, Greece
³³ School of Physics and Astronomy, University of Edinburgh, Edinburgh, UK
³⁴ Dipartimento di Fisica e Astronomia, Università di Bologna, Bologna, Italy
³⁵ INFN Laboratori Nazionali di Legnaro, Legnaro, Italy
³⁶ Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, Trieste, Italy
³⁷ Department of Physics, University of Trieste, Trieste, Italy
³⁸ Department of Physics and Astronomy, University of Catania, Catania, Italy
³⁹ Physikalisch-Technische Bundesanstalt (PTB), Bundesallee 100, 38116, Braunschweig, Germany
⁴⁰ University of Ioannina, Ioannina, Greece
⁴¹ Faculty of Physics, University of Vienna, Vienna, Austria
⁴² University of Granada, Granada, Spain
⁴³ Bhabha Atomic Research Centre (BARC), Mumbai, India
⁴⁴ Centre for Astrophysics Research, University of Hertfordshire, Hatfield, UK
⁴⁵ Department of Physics, University of Basel, Basel, Switzerland
⁴⁶ Australian National University, Canberra, Australia

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Received: 18 July 2025
Accepted: 20 December 2025
Published online: 20 February 2026

Abstract

Accurate neutron capture cross sections are essential for the design and operation of fast reactors using MOX fuels. For $_{}^{242}$Pu, the Nuclear Energy Agency (NEA) recommends 8–12% accuracy in the fast energy region (2–500 keV), compared to the current uncertainty of 35%. Moreover, integral experiments and previous measurements suggest the evaluated $_{}^{242}$Pu(n,$\gamma$) cross section is overestimated, particularly in the JEFF-3.3 library, which shows a 14% overestimation between 1 keV and 1 MeV. Recent measurements from LANSCE reported a 20–30% reduction in the 1–40 keV range relative to evaluations. To solve these discrepancies, the $_{}^{242}$Pu(n,$\gamma$) cross section was measured from 1 to 600 keV at CERN n_TOF-EAR1 facility using a 95(4) mg $_{}^{242}$Pu target, enriched to 99.959%. Gamma rays from neutron capture were detected with an array of ${\text{C}}_6{\text{D}}_6$ scintillators and a novel application of the Pulse Height Weighting Technique was employed. The resulting cross section presents a systematic uncertainty between 8 and 12%, reducing the current uncertainties of 35% and achieving the accuracy requested by the NEA. Analysis using FITACS produced average resonance parameters, consistent with the analysis of the resolved resonance region. Our data align well with Wisshak and Käeppeler, and are 10–14% lower than JEFF-3.3 in the 1–250 keV range, helping to achieve consistency with integral benchmarks. At higher energies, our results are in reasonable agreement with ENDF/B-VIII.1 and JEFF-3.3. In contrast, DANCE results appear to underestimate the cross section by a factor of 2–3 above a few keV.