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This paper details the solar neutrino analysis of the 385.17-day Phase-III data set acquired by the Sudbury Neutrino Observatory (SNO). An array of $^3$He proportional counters was installed in the heavy-water target to measure precisely the rate of neutrino-deuteron neutral-current interactions. This technique to determine the total active $^8$B solar neutrino flux was largely independent of the methods employed in previous phases. The total flux of active neutrinos was measured to be $5.54^{+0.33}_{-0.31}(stat.)^{+0.36}_{-0.34}(syst.)\times 10^{6}$ cm$^{-2}$ s$^{-1}$, consistent with previous measurements and standard solar models. A global analysis of solar and reactor neutrino mixing parameters yielded the best-fit values of $\Delta m^2 = 7.59^{+0.19}_{-0.21}\times 10^{-5}{eV}^2$ and $\theta = 34.4^{+1.3}_{-1.2}$ degrees.

The Sudbury Neutrino Observatory (SNO) used an array of 3He proportional counters to measure the rate of neutral-current interactions in heavy water and precisely determined the total active (nu_x) 8B solar neutrino flux. This technique is independent of previous methods employed by SNO. The total flux is found to be 5.54_-0.31;+0.33(stat)-0.34+0.36(syst)x10(6) cm(-2) s(-1), in agreement with previous measurements and standard solar models. A global analysis of solar and reactor neutrino results yields Deltam2=7.59_-0.21;+0.19x10(-5) eV2 and theta=34.4_-1.2;+1.3 degrees. The uncertainty on the mixing angle has been reduced from SNO's previous results.

The 31-yr isomer of {sup 178}Hf at excitation energy 2.446 MeV, and with J{sup {pi}}, K= 16+, 16, has been the object of several studies for possible mechanisms that might trigger isomer decay to the ground state. Potential for the control of nuclear energies (MeV) with atomic energies (keV) is the driving interest. The 178Hf isomer is a favorite nucleus in the search for triggered decay because this isomer is long-lived, available in microgram quantities, the decay scheme is well known, the excitation energy is high, and a sample enriched in the isomer can be fabricated for irradiation. In fact, accelerated decay of the {sup 178}Hf isomer when irradiated with photons from a dental x-ray machine has been reported by Collins et al. The triggering x-ray energies were reported to be in the 20-60 keV range. Using the synchrotron radiation at the Advanced Photon Source (APS) we published limits on such accelerated emission approximately 5 orders of magnitude lower than those in ref. 1. Very recently, a new measurement of triggering has been reported by Collins et al., using monochromatic x rays from the SPring-8 synchrotron but this time for (several) much lower incident x-ray energies in the 9-13 keV region. In order to verify this observation, we undertook a new measurement at the APS, with significantly increased focus on incident x-rays below 20 keV, as described below.

Enhanced decay of the 31-yr isomer of 178Hf induced by x-ray irradiation has been reported previously. Here we describe an attempt to reproduce this result with an intense "white" x-ray beam from the Advanced Photon Source. No induced decay was observed. The upper limits for the energy-integrated cross sections for such a process, over the range of energies of 20–60 keV x rays, are less than 2×10^-27cm^2 keV, below the previously reported values by more than 5 orders of magnitude; at 8 keV the limit is 5×10^-26 cm^2 keV.