Neutron brilliance of the liquid deuterium cold source as measured from the ICON beamline at the swiss spallation neutron source (SINQ)

Abstract

A brilliance measurement was conducted on July 21, 2014 at the ICON beamline at SINQ as a benchmark before any potential changes are made to the liquid deuterium cold neutron source in a future extended shutdown period. The peak brilliance of the deuterium cold source at SINQ has been measured to be 3.3±0.15×1011 n cm−2 s−1 mA−1 Å −1 sterad−1 at 1.8 Å, and the total brilliance (energy-integrated) has been measured to be 9.1±0.77×1011 n cm−2 s−1 mA−1 sterad−1 for wavelengths above 0.7 Å via a time-of-flight measurement at the ICON beamline. Using a detailed MCNP model, the peak brilliance has been calculated to be 3.1±0.14×1011 n cm−2 s−1 mA−1 Å −1 sterad−1 at 1.65 Å, and the total brilliance (energy-integrated) has been calculated to be 9.2±1.2×1011 n cm−2 s−1 mA−1 sterad−1 for wavelengths above 0.7 Å. The peak brilliance value and wavelength position disagree only slightly between the measurement and model (7% difference in value, 8% difference in wavelength position), and the total brilliance agrees within the uncertainty bounds. The close agreement validates the models and benchmarks the state of the cold source.