Experimental and Theoretical Studies of a Gadolinium-Water Neutron Detector for Cosmogenic Neutron Flux Measurements by

Experimental and Theoretical Studies of a Gadolinium-Water Neutron Detector for Cosmogenic Neutron Flux Measurements by Robert K. Lanza, Jr. Bachelors of Science in Physics University of California, Santa Barbara Harry N. Nelson, Advisor This work describes experimental and theoretical aspects of calibrations performed on a gadolinium/water neutron detector designed to measure the cosmogenic neutron flux in the Soudan mine for the CDMS II dark matter experiment. A calibration using Cherenkov emitting cosmic ray muons was performed, and a calculation was made of the expected number of photoelectrons produced. The calculated number of photoelectrons was roughly 3σ above the mean experimental value, and probable explanations are discussed. A single photoelectron calibration was also performed using pulsed light from an LED. In addition, a device for increased light collection known as a Winston cone was studied and implemented. The use of a Winston cone is desirable because it very closely approaches the maximum possible light concentration ratio set by theory. Our light collection was found to increase by roughly 60% through the use of a Winston cone.