Assembly of Alpha Gamma Chamber and Li-6 Target Ladder System for the BL3 Project

The BL3 experiment aims to measure the free neutron lifetime on a cold neutron beam to high precision by detecting the decay protons in a Penning trap and the total neutron capture flux through interaction with a thin Li-6 foil. Such measurements are critical for refining Big Bang Nucleosynthesis models and testing the unitarity of the CKM matrix. The current beam result exhibits a significant deviation from ultracold neutron decay experiments. My work focuses on mechanical and electronic preparations for BL3, including ultrasonic cleaning of ultra-high vacuum components, assembly of the Alpha-Gamma chamber, and implementation of motion control systems for the target ladder. The target ladder enables precise placement of Li-6 targets for neutron capture and decay along the beamline and for particle detection. To maximize particle detection uniformity, detectors were positioned by modeling and optimizing the total solid-angle subtended by different points on the target. Future measurements are aimed at validating these models and testing the uniformity by scanning a sealed alpha source across the target surface and measuring the total count rate in all six detectors. These efforts will help reduce systematic uncertainties and improve systematic errors in the resulting neutron lifetime measurements.