Improved STEREO simulation with a new gamma ray spectrum of excited gadolinium isotopes using FIFRELIN

H. Almazán; L. Bernard; A. Blanchet; A. Bonhomme; C. Buck; A. Chebboubi; P. del Amo Sanchez; I. El Atmani; J. Haser; F. Kandzia; S. Kox; L. Labit; J. Lamblin; A. Letourneau; D. Lhuillier; M. Lindner; O. Litaize; T. Materna; A. Minotti; H. Pessard; J. -S. Réal; C. Roca; T. Salagnac; V. Savu; S. Schoppmann; V. Sergeyeva; T. Soldner; A. Stutz; L. Thulliez; M. Vialat

doi:10.1140/epja/i2019-12886-y

2021 Impact factor 3.131

Hadrons and Nuclei

Open Access

Eur. Phys. J. A (2019) 55: 183
https://doi.org/10.1140/epja/i2019-12886-y

Special Article - New Tools and Techniques

Improved STEREO simulation with a new gamma ray spectrum of excited gadolinium isotopes using FIFRELIN

H. Almazán¹, L. Bernard², A. Blanchet³, A. Bonhomme¹^,3^*, C. Buck¹, A. Chebboubi⁶, P. del Amo Sanchez⁴, I. El Atmani³, J. Haser¹, F. Kandzia⁵, S. Kox², L. Labit⁴, J. Lamblin², A. Letourneau³, D. Lhuillier³, M. Lindner¹, O. Litaize⁶, T. Materna³, A. Minotti³, H. Pessard⁴, J. -S. Réal², C. Roca¹, T. Salagnac², V. Savu³, S. Schoppmann¹, V. Sergeyeva⁴, T. Soldner⁵, A. Stutz², L. Thulliez³ and M. Vialat²

¹ Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117, Heidelberg, Germany
² Univ. Grenoble Alpes, CNRS, Grenoble INP, LPSC-IN2P3, 38000, Grenoble, France
³ IRFU, CEA, Université Paris-Saclay, 91191, Gif-sur-Yvette, France
⁴ Univ. Grenoble Alpes, Université Savoie Mont Blanc, CNRS/IN2P3, LAPP, 74000, Annecy, France
⁵ Institut Laue-Langevin, CS 20156, 38042, Grenoble Cedex 9, France
⁶ CEA, DEN, DER, SPRC, F-13108, Saint Paul Lez Durance, France

^* e-mail: aurelie.bonhomme@mpi-hd.mpg.de

Received: 31 May 2019
Accepted: 19 September 2019
Published online: 23 October 2019

Abstract

The STEREO experiment measures the electron antineutrino spectrum emitted in a research reactor using the inverse beta decay reaction on H nuclei in a gadolinium loaded liquid scintillator. The detection is based on a signal coincidence of a prompt positron and a delayed neutron capture event. The simulated response of the neutron capture on gadolinium is crucial for the comparison with data, in particular in the case of the detection efficiency. Among all stable isotopes, ¹⁵⁵Gd and ¹⁵⁷Gd have the highest cross sections for thermal neutron capture. The excited nuclei after the neutron capture emit gamma rays with a total energy of about 8MeV. The complex level schemes of ¹⁵⁶Gd and ¹⁵⁸Gd are a challenge for the modeling and prediction of the deexcitation spectrum, especially for compact detectors where gamma rays can escape the active volume. With a new description of the Gd (n,) cascades obtained using the FIFRELIN code, the agreement between simulation and measurements with a neutron calibration source was significantly improved in the STEREO experiment. A database of ten millions of deexcitation cascades for each isotope has been generated and is now available for the user.