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The SND@LHC neutron shielding

The SND@LHC Collaboration

TL;DR

The study tackles neutron background challenges for the SND@LHC emulsion target by designing the ColdBox, a sealed shielding enclosure with a dual-layer shield (plexiglass moderator and borated polyethylene absorber) to preserve environmental stability. It employs FLUKA simulations (with Flair) to optimize geometry and material composition, corroborated by boron-content verification and finite-element structural analysis. The results show substantial attenuation of thermal neutrons, with a simulated ratio of $R_{\text{SIM}}$ around $2.3 \times 10^{-3}$, consistent with, and more stringent than, the experimental BatMon upper limit. The work delivers a robust, future-proof shielding solution that preserves emulsion integrity while fitting the constrained TI18 geometry, with plans for ongoing monitoring and refinement.

Abstract

The design and construction of a neutron shielding for the SND@LHC detector, which utilizes a combination of plexiglass and borated polyethylene, is presented. FLUKA simulations were employed to optimize the shielding configuration and assess its efficiency. Results indicate a significant reduction in neutron flux, ensuring the long-term stability of the emulsion films used in the target of the SND@LHC detector.

The SND@LHC neutron shielding

TL;DR

The study tackles neutron background challenges for the SND@LHC emulsion target by designing the ColdBox, a sealed shielding enclosure with a dual-layer shield (plexiglass moderator and borated polyethylene absorber) to preserve environmental stability. It employs FLUKA simulations (with Flair) to optimize geometry and material composition, corroborated by boron-content verification and finite-element structural analysis. The results show substantial attenuation of thermal neutrons, with a simulated ratio of around , consistent with, and more stringent than, the experimental BatMon upper limit. The work delivers a robust, future-proof shielding solution that preserves emulsion integrity while fitting the constrained TI18 geometry, with plans for ongoing monitoring and refinement.

Abstract

The design and construction of a neutron shielding for the SND@LHC detector, which utilizes a combination of plexiglass and borated polyethylene, is presented. FLUKA simulations were employed to optimize the shielding configuration and assess its efficiency. Results indicate a significant reduction in neutron flux, ensuring the long-term stability of the emulsion films used in the target of the SND@LHC detector.

Paper Structure

This paper contains 13 sections, 2 equations, 14 figures, 8 tables.

Table of Contents

  1. Introduction
  2. Mechanical Design and Construction
  3. Design Requirements and Frame
  4. Shielding Materials and Assembly
  5. Sealing and Safety Compliance
  6. Structural Analysis
  7. FLUKA Simulations and Shielding Performance
  8. Simulation Setup and Material Selection
  9. Configuration Optimization and Results
  10. Comparison with Measurements
  11. Verification of Boron Content
  12. Conclusions
  13. Appendix: ColdBox drawings

Figures (14)

  • Figure 1: The SND@LHC detector.
  • Figure 2: Installed aluminium frame
  • Figure 3: Evaporator highlighted in yellow over the target region highlighted in red.
  • Figure 4: Left side: machined borated polyethylene. Right side: plexiglass sheets before the machining process.
  • Figure 5: View of the final ColdBox.
  • ...and 9 more figures