The 16N calibration source for the Sudbury Neutrino Observatory

Abstract A calibration source using γ-rays from 16 N ( t 1/2 =7.13 s) β-decay has been developed for the Sudbury Neutrino Observatory (SNO) for the purpose of energy and other calibrations. The 16 N is produced via the (n,p) reaction on 16 O in the form of CO 2 gas using 14-MeV neutrons from a commercially available Deuterium-Tritium (DT) generator. The 16 N is produced in a shielding pit in a utility room near the SNO cavity and transferred to the water volumes (D 2 O or H 2 O) in a CO 2 gas stream via small diameter capillary tubing. The bulk of the activity decays in a decay/trigger chamber designed to block the energetic β-particles yet permit the primary branch 6.13 MeV γ-rays to exit. Detection of the coincident β-particles with plastic scintillator lining the walls of the decay chamber volume provides a tag for the SNO electronics. This paper gives details of the production, transfer, and triggering systems for this source along with a discussion of the source γ-ray output and performance.