The 16N calibration source for the Sudbury Neutrino Observatory

Abstract

A calibration source using γ-rays from 16N ( 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 16N is produced via the (n,p) reaction on 16O in the form of CO 2 gas using 14-MeV neutrons from a commercially available Deuterium-Tritium (DT) generator. The 16N is produced in a shielding pit in a utility room near the SNO cavity and transferred to the water volumes (D 2O or H 2O) 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.