Beam Profile Corrections for BL3 Neutron Intensity Monitor*

The recent measurement of the lifetime of the free neutron using the beam method has an 8.7s (4σ) discrepancy with UCN measurements. The goal of the BL3 experiment is to improve the statistical error of this measurement and explore systematic uncertainties as an explanation for the discrepancy. A well-characterized neutron flux detector with flat response is important since the neutron flux enters linearly into the neutron lifetime. I will present a method of determining the average neutron beam position and RMS width using two rings of detectors and describe how to use this information to correct for the beam acceptance.