Precision Measurement of Cold Neutron Flux

The use of cold neutron beams in experiments such as the neutron beam lifetime experiment BL-2 necessitates a means of accurately measuring their flux to high precision.  The Alpha-Gamma device at the National Institute of Standards and Technology (NIST) provides a sub-0.1% measurement of the flux of a monochromatic cold neutron beam. This is accomplished through measurement of the alpha and gamma production rate following neutron absorption on a totally absorbing ¹⁰B target. The Alpha-Gamma device has most notably been used to recalibrate the flux monitor used in the neutron beam lifetime experiment leading to a re-evaluation of its result in 2012; we will discuss recent efforts in the current beam lifetime experiment at NIST. We will also cover other current projects including high precision measurements of the ²³⁵U(n,f) and ⁶Li(n,t)⁴He cross sections and a novel calibration technique for the NIST manganese bath neutron source calibration facility.