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Design and commissioning of the miniBELEN neutron counter for the study of $(α,n)$ reactions

Nil Mont-Geli, Ariel Tarifeño-Saldivia, Max Pallàs, Ángel Perea, Luis Mario Fraile, Guillem Cortés, Sílvia Viñals, José Luis Tain, Gastón Garcia, Daniel Soler, Odette Alonso-Sañudo, María José G. Borge, José Antonio Briz, Francisco Calviño, Daniel Cano-Ott, Alfredo De Blas, Begoña Fernández, Roger Garcia, Vicente Garcia Tavora, Enrique M. González-Romero, Carlos Guerrero, Andrés Illana, Trino Martínez, Víctor Martínez-Nouvilas, Emilio Mendoza, Enrique Nácher, Amanda Nerio Aguirre, Julio Plaza, Olof Tengblad, José Manuel Udías

Abstract

The miniBELEN detector is a moderated neutron counter based on the use of $^3$He tubes and high-density polyethylene as moderator. The detector has been designed to have a neutron detection efficiency that is nearly independent from the initial neutron energy for ($α$,n) reactions with alpha-particle energies up to 15 MeV. In order to achieve that, an innovative design methodology based on the use of cadmium neutron filters has been used. Monte Carlo calculations of the detector response have been validated using a $^{252}$Cf fission source. Measurements of the relatively well-known ($α$,n) thick-target yields on aluminum have been found to be consistent with data from previous works. A method has been developed to correlate the counting rate ring ratios with the mean neutron energy and validated using previous time-of-flight measurements of the aluminum ($α$,n) spectra and with a $^{252}$Cf fission source. Submitted to The European Physical Journal - Plus

Design and commissioning of the miniBELEN neutron counter for the study of $(α,n)$ reactions

Abstract

The miniBELEN detector is a moderated neutron counter based on the use of He tubes and high-density polyethylene as moderator. The detector has been designed to have a neutron detection efficiency that is nearly independent from the initial neutron energy for (,n) reactions with alpha-particle energies up to 15 MeV. In order to achieve that, an innovative design methodology based on the use of cadmium neutron filters has been used. Monte Carlo calculations of the detector response have been validated using a Cf fission source. Measurements of the relatively well-known (,n) thick-target yields on aluminum have been found to be consistent with data from previous works. A method has been developed to correlate the counting rate ring ratios with the mean neutron energy and validated using previous time-of-flight measurements of the aluminum (,n) spectra and with a Cf fission source. Submitted to The European Physical Journal - Plus

Paper Structure

This paper contains 25 sections, 13 equations, 17 figures, 7 tables.

Table of Contents

  1. Introduction
  2. Design requirements
  3. Detector design
  4. Description of the simulation setup
  5. Figures of merit: average efficiency and flatness
  6. Design methodology: the composition method
  7. Optimization of miniBELEN
  8. Final configurations
  9. Discussion
  10. Implementation of miniBELEN-10A
  11. Physical implementation of the detector
  12. Neutron detection efficiency by Monte Carlo simulations
  13. Experimental characterization with a fission source
  14. Neutron Multiplicity Counting (NMC)
  15. Experimental setup
  16. ...and 10 more sections

Figures (17)

  • Figure 1: Upper panel: HDPE block (7x10x70 cm$^3$) used in miniBELEN. Each of these blocks is made of seven smaller pieces (7x10x10 cm$^3$) which are assembled using two stainless-steel rods. The black arrow shows one of these small blocks. Lower panel: front view of one of the HDPE blocks. The $^3$He-filled neutron counters are embedded within the central hole. The stainless-steel rods can also been seen (top left and bottom right corners).
  • Figure 2: Selected configuration for the optimization of the composition functions (miniBELEN-X). Light-blue: HDPE. Black: stainless-steel rods. Grey: proportional counters. White: 7x7 cm$^2$ central hole required to hold the beam-pipe and gamma detectors (see text for more details). Each ring is shown dashed circles. This is the view of the detector looking from the end of the beam-line.
  • Figure 3: Neutron detection efficiency of miniBELEN-X calculated using Particle Counter. The efficiency have been calculated using the set of neutron energies $E_i$ from section \ref{['sec:secParMer']}. Linear interpolations are used between the data points. The y-axis error-bars are smaller than width of the data lines. Black solid: total efficiency. Red dashed: ring 1 (inner) efficiency. Blue dash-dotted (1 dot): ring 2 efficiency. Green dash-dotted (2 dots): ring 3 efficiency. Orange dash-dotted (3 dots): ring 4 efficiency. Magenta dotted: ring 5 (outer) efficiency.
  • Figure 4: Average efficiencies up to 10 MeV and flatness values $F(5)$ and $F(10)$ obtained from different combinations of the composition functions. Solutions with average efficiencies below 2% are not shown. The color scale saturates at efficiency values above 9%. Upper panel: configuration miniBELEN-X. Lower panel: configuration miniBELEN-X + 4 cm thickness reflectors.
  • Figure 5: Reflectors (red) are HDPE which are added beyond the outer ring in order to increase the efficiency of miniBELEN without sacrificing flatness and adding new counters (see text for more details). In this example the thickness of the reflectors has been set to 4 cm. This is the rear view of the detector, looking from the end of the beam-line.
  • ...and 12 more figures