The Design and Analysis of CRU Lifting and Placement Systems for Project Dune

Abstract

The Deep Underground Neutrino Experiment (DUNE) is an international collaboration investigating neutrino physics. One of the key objectives is to understand the start of the universe. What causes asymmetry to occur between matter and antimatter, resulting in a universe dominated by matter and giving rise to the structure of the universe as we know it. Spanning 800 miles from Fermilab in Illinois to the Sanford Underground Research Facility in South Dakota. Neutrinos generated at Fermilab pass through a near detector before traveling through the Earth to the far detector where 4 liquid argon time project chambers (LArTPCs) with specialized sensors or Charge Readout Units (CRUs) capture the ionization electron produced in liquid argon. Comparing data from both detectors enables researchers to analyze neutrino oscillations. The precision required for such measurements demands exact CRU alignment, with tight tolerances. Which presents significant mechanical, thermal, electrical, and safety challenges. This paper focuses on the design and implementation of CRU lifting and placement systems for safe and reliable positioning. The CRU lifting system combines a winch and stepper motor mechanism with a programmable logic controller (PLC) for precise, stable movement. Adjustable tine supports counteract deflection under load, and a crane tine control system enables fine angular adjustments. Safety features, including emergency stops, limit switches, and electrical fusing, protect operators and equipment while meeting regulatory requirements. This integrated design allows CRUs to be maneuvered safely and positioned within tight tolerances inside the cryostat. Once lifted into position, CRUs are aligned using a compact, manually actuated X-Y translation platform constructed from 80/20 aluminum framing. Two precision ball screws provide orthogonal movement, while a turnbuckle enables controlled rotation about the vertical

axis. The system clamps directly to the cryostat’s false floor, ensuring stability, millimeter-level accuracy, and repeatable positioning across multiple installations without adding unnecessary mechanical complexity. Operation at 87 K introduces differential thermal contraction between materials, which can cause misalignment and reduced clamping force. G-10 adapter plates contract anisotropically, pulling bolt holes inward, while stainless steel fasteners contract more uniformly. Hole oversizing was calculated based on radial position to maintain clearance after cooldown, and Belleville washers were incorporated to preserve preload despite dimensional changes. These measures ensure secure connections and consistent alignment throughout thermal cycling.

Finite element analysis (FEA) in ANSYS validated the intermediate frame’s ability to meet stiffness and planarity requirements under gravitational and cryogenic loading. Both frame- only and frame-with-CRU models were evaluated, including realistic contact interactions between CRU feet and cross beams. Results showed deflection remained within the 4 mm tolerance, and beam dimensions were optimized to balance cost and performance. The resulting installation framework meets DUNE’s demanding mechanical, thermal, and safety requirements while providing a transferable design methodology for future large-scale cryogenic physics experiments.