Nuclear Instruments and Methods in Physics Research A 478 (2002) 559–576 The response of a liquid scintillator detector to 21–100 MeV neutrons J. Thun a,b , J. Blomgren a, *, K. Elmgren a , J. K . allne a , N. Olsson a , J.F. Lecolley c , F. Lefebvres c , C. Varignon c , F. Borne d , X. Ledoux d , Y. Patin d , O. Jonsson e , P.-U. Renberg e a Department of Neutron Research, Uppsala University, P.O. Box 525, 5751-20, Uppsala, Sweden b Laboratoire National Saturne, Gif-sur-Yvette, France c LPC, ISMRA et Universit ! e de Caen, CNRS=IN2P3, France d DPTA=SPN, Commissariat " a l’Energie Atomique, Bruy " eres-le-Ch # atel, France e The Svedberg Laboratory, Uppsala University, Sweden Received 28 February 2001 Abstract A large volume ð4lÞ liquid NE213 scintillator detector for neutrons in the energy range up to 800 MeV has been calibrated using a high accuracy tagging technique at E n ¼ 21; 34; 50; 60 and 100 MeV. The experiment is described together with a discussion of the accuracy in the absolute efficiency calibration. Results are presented on total and differential detection efficiencies along with information on the underlying nuclear reactions causing the detector response, including both charged particles and g-rays. The present results complement previous measurements for the same detector, so that an efficiency calibration now exists over an energy range of E n ¼ 2–800 MeV. The empirical results are compared with a calculated energy dependence of the detector response to neutrons. r 2002 Elsevier Science B.V. All rights reserved. PACS: 29.30.Hs; 29.40.Mc Keywords: Neutron beam; Neutron detection; Liquid scintillator; Tagging; Neutron detector efficiency; Spatial efficiency 1. Introduction Efficiency calibration of neutron detectors, such as liquid scintillators, is a general and persistent problem, making it a limiting factor in many nuclear physics studies involving neutrons. Experi- mental calibration studies (see Ref. [1] and references therein) have been performed for lower energies, but are scarce and of modest accuracy for energies above 20 MeV. Where data are missing, one has been referred to using calculated efficiency values and their dependence on neutron energy, besides the detector geometry dependent variation [1,2]. Efficiency calibration studies in the region E n > 20 MeV are therefore highly desirable. The present new calibration measurements were prompted by the interest in studies of *Corresponding author. Tel.: +46-18-471-3788. E-mail address: jan.blomgren@tsl.uu.se (J. Blomgren). 0168-9002/02/$-see front matter r 2002 Elsevier Science B.V. All rights reserved. PII:S0168-9002(01)00888-9