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 × 1 0 11 n cm −2 s −1 mA −1 A −1 sterad −1 at 1.8 A, and the total brilliance (energy-integrated) has been measured to be 9 . 1 ± 0 . 77 × 1 0 11 n cm −2 s −1 mA −1 sterad −1 for wavelengths above 0.7 A 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 × 1 0 11 n cm −2 s −1 mA −1 A −1 sterad −1 at 1.65 A, and the total brilliance (energy-integrated) has been calculated to be 9 . 2 ± 1 . 2 × 1 0 11 n cm −2 s −1 mA −1 sterad −1 for wavelengths above 0.7 A. 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.