Session: Government Agency Student Posters

Paper Number: 172922

Mechanical Design of a Target Ladder for the Bl3 Neutron Lifetime Experiment 

The goal of the BL3 (Beam Lifetime 3) experiment is to resolve a longstanding discrepancy between measurements of the neutron lifetime using a beam versus trapped neutrons. Better determination of the neutron lifetime and will refine our understanding of the fundamental laws of physics, explaining Big Bang Nucleosynthesis and the early evolution of the universe. 

In a beam, the lifetime is extracted from the ratio of the decay rate to the number of neutrons present in the fiducial volume of the beam, while for trapped neutrons, the lifetime is extracted by fitting the density as a function of time to an exponential distribution.  These two measurements currently disagree by 5 sigmas.  The BL3 experiment is being constructed to run at the NIST Center for Neutron Research (NCNR) at the National Institute of Standards and Technology to investigate systematic errors in the beam lifetime, associated with uncertainties in measurements of the neutron density and of the neutron decay rate.

A central component of the BL3 apparatus is the target ladder, which enables the precise positioning of multiple lithium-6 (Li-6) targets in the neutron beam within the vacuum chamber of the neutron detector. These deposits are crucial for measuring neutron beam intensity by capturing neutrons and producing charged particles that are detected downstream. As the measurement is directly tied to the accuracy of the lifetime calculation, the ladder must meet certain requirements for mechanical stability, thermal resilience, and neutron background minimization.

To meet the necessary constraints we are constructing the target ladder from a combination of stainless steel and aluminum, materials selected for their mechanical strength, vacuum compatibility, and minimal activation under neutron exposure. As we highlight this design process which also includes detailed mechanical modeling, material selection based on thermal and structural properties, and careful consideration of vacuum constraints. The assembly incorporates features that aim to ensure accurate target placement, reduce thermal deformation, and allow consistent transitions between multiple target positions.

As we are still in the design and assembly/testing phase of the parts, the current stage of the project focuses on finalizing mechanical assembly and preparing the ladder system for integration into the full setup that will be used. The work lays a foundation for reducing systematic errors and or uncertainty in neutron flux measurements, contributing to the broader experimental goal of improving neutron lifetime precision. Ultimately, this engineering effort supports advancements in both experimental techniques and the fundamental understanding of particle physics and cosmology. As it is crucial to have this deeper understanding in the project.

Presenting Author: Daryen Rodriguez-Saucedo University of Kentucky

Presenting Author Biography: Daryen Rodriguez-Saucedo is a junior majoring in Computer Engineering in the Department of Electrical and Computer Engineering at the University of Kentucky. He is also pursuing minors in Mathematics and Psychology. During his sophomore year, he worked as an undergraduate research assistant in the Department of Physics and Astronomy on the BL3 Project, where he contributed to experimental efforts related to neutron lifetime measurements. He plans to continue his involvement with the project during the academic year.

Authors:

Daryen Rodriguez-Saucedo University of Kentucky
Christopher Crawford University of Kentucky