No abstract available

[en] The technique used at the Sudbury Neutrino Observatory (SNO) to measure the concentration of ²²²Rn in water is described. Water from the SNO detector is passed through a vacuum degasser (in the light water system) or a membrane contact degasser (in the heavy water system) where dissolved gases, including radon, are liberated. The degasser is connected to a vacuum system which collects the radon on a cold trap and removes most other gases, such as water vapor and N₂. After roughly 0.5 tonnes of H₂O or 6 tonnes of D₂O have been sampled, the accumulated radon is transferred to a Lucas cell. The cell is mounted on a photomultiplier tube which detects the α-particles from the decay of ²²²Rn and its progeny. The overall degassing and concentration efficiency is about 38% and the single-α counting efficiency is approximately 75%. The sensitivity of the radon assay system for D₂O is equivalent to ∼3x10^-15 g U/g water. The radon concentration in both the H₂O and D₂O is sufficiently low that the rate of background events from U-chain elements is a small fraction of the interaction rate of solar neutrinos by the neutral current reaction

[en] As photodisintegration of deuterons mimics the disintegration of deuterons by neutrinos, the accurate measurement of the radioactivity from thorium and uranium decay chains in the heavy water in the Sudbury Neutrino Observatory (SNO) is essential for the determination of the total solar neutrino flux. A radium assay technique of the required sensitivity is described that uses hydrous titanium oxide adsorbent on a filtration membrane together with a β-α delayed coincidence counting system. For a 200 tonne assay the detection limit for ²³²Th is a concentration of ∼3x10^-16 g Th/g water and for ²³⁸U of ∼3x10^-16 g U/g water. Results of assays of both the heavy and light water carried out during the first 2 years of data collection of SNO are presented

No abstract available

[en] The Sudbury Neutrino Observatory (SNO) has precisely determined the total active (v_x)⁸B solar neutrino flux without assumptions about the energy dependence of the v_e survival probability. The measurements were made with dissolved NaCl in the heavy water to enhance the sensitivity and signature for neutral-current interactions. The flux is found to be 5.21+-0.27 (stat)+-0.38(syst)x10^-6 cm^-2s^-1, in agreement with previous measurements and standard solar models. A global analysis of these and other solar and reactor neutrino results yields Δm² = 7.1^+1.2_-0.6 x 10^-5 eV² and θ 32.5^+2.4_-2.3 degrees. Maximal mixing is rejected at the equivalent of 5.4 standard deviations

[en] The Sudbury Neutrino Observatory (SNO) is a water imaging Cherenkov detector. Its usage of 1000 metric tons of D₂O as target allows the SNO detector to make a solar-model independent test of the neutrino oscillation hypothesis by simultaneously measuring the solar ν_e flux and the total flux of all active neutrino species. Solar neutrinos from the decay of ⁸B have been detected at SNO by the charged-current (CC) interaction on the deuteron and by the elastic scattering (ES) of electrons. While the CC reaction is sensitive exclusively to ν_e, the ES reaction also has a small sensitivity to ν_μ and ν_τ. In this paper, recent solar neutrino results from the SNO experiment are presented. It is demonstrated that the solar flux from ⁸B decay as measured from the ES reaction rate under the no-oscillation assumption is consistent with the high precision ES measurement by the Super-Kamiokande experiment. The ν_e flux deduced from the CC reaction rate in SNO differs from the Super-Kamiokande ES results by 3.3σ. This is evidence for an active neutrino component, in additional to ν_e, in the solar neutrino flux. These results also allow the first experimental determination of the total active ⁸B neutrino flux from the Sun, and is found to be in good agreement with solar model predictions

[en] The Sudbury Neutrino Observatory is a second-generation water Cherenkov detector designed to determine whether the currently observed solar neutrino deficit is a result of neutrino oscillations. The detector is unique in its use of D₂O as a detection medium, permitting it to make a solar model-independent test of the neutrino oscillation hypothesis by comparison of the charged- and neutral-current interaction rates. In this paper the physical properties, construction, and preliminary operation of the Sudbury Neutrino Observatory are described. Data and predicted operating parameters are provided whenever possible