Eur. Phys. J. A (2013) 49: 62
https://doi.org/10.1140/epja/i2013-13062-3

Regular Article - Experimental Physics

Determination of the ²³⁷Np(n,f) reaction cross section for E_n = 4.5-5.3 MeV, using a MicroMegas detector assembly

¹⁹⁸⁹² Department of Physics, National Technical University of Athens, Athens, Greece
²⁹⁸⁹² Institute of Nuclear Physics, NCSR “Demokritos”, Athens, Greece
³⁹⁸⁹² Commissariat à l’ Énergie Atomique (CEA), Saclay, France

^* e-mail: diakakim@central.ntua.gr

Received: 1 January 2013
Accepted: 24 April 2013
Published online: 24 May 2013

Abstract

In the present work, the measurement of the ²³⁷Np(n,f) cross section with reference to the standard ²³⁸U(n,f) reaction was performed for the first time with a MicroMegas detector, especially developed at CERN, for these measurements, within the framework of the n_TOF Collaboration. The incident monoenergetic neutron beam with energies in the range 4.5-5.3MeV was produced via the ²H(d,n) reaction at the neutron facility of the 5.5MV Tandem accelerator laboratory at NCSR “Demokritos”. The mass of the actinide content of the targets used and of their impurities was quantitatively determined via alpha spectroscopy. Furthermore, their thickness and homogeneity have been examined via the RBS (Rutherford Backscattering Spectrometry) technique. Monte Carlo simulations were carried out using the code MCNP5 implementing the neutron beam setup and the MicroMegas assembly in order to determine the neutron flux for each target, as well as the existence of possible low-energy neutrons due to scattering. Additional simulations with FLUKA were performed, studying the energy deposition of the fission fragments in the active area of the detector, in order to accurately estimate the detection efficiency. Fair discrimination of the heavy and light mass peaks of the fission fragments at the energy spectra was achieved. The present work is compared to existing evaluations and previous data which present discrepancies of up to 8% within the same energy range.