Fluorescence Efficiency and Visible Re-emission Spectrum of Tetraphenyl Butadiene Films at Extreme Ultraviolet Wavelengths

A large number of current and future experiments in neutrino and dark matter detection use the scintillation light from noble elements as a mechanism for measuring energy deposition. The scintillation light from these elements is produced in the extreme ultraviolet (EUV) range, from 60 - 200 nm. Currently, the most practical technique for observing light at these wavelengths is to surround the scintillation volume with a thin film of Tetraphenyl Butadiene (TPB) to act as a fluor. The TPB film absorbs EUV photons and reemits visible photons, detectable with a variety of commercial photosensors. Here we present a measurement of the re-emission spectrum of TPB films when illuminated with 128, 160, 175, and 250 nm light. We also measure the fluorescence efficiency as a function of incident wavelength from 120 to 250 nm.Comment: 15 pages, 9 figures, Submitted to Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipmen

The calibration of the Sudbury Neutrino Observatory using uniformly distributed radioactive sources

The production and analysis of distributed sources of 24Na and 222Rn in the Sudbury Neutrino Observatory (SNO) are described. These unique sources provided accurate calibrations of the response to neutrons, produced through photodisintegration of the deuterons in the heavy water target, and to low energy betas and gammas. The application of these sources in determining the neutron detection efficiency and response of the 3He proportional counter array, and the characteristics of background Cherenkov light from trace amounts of natural radioactivity is described.Comment: 24 pages, 13 figure

Measurement of the νe and total 8B solar neutrino fluxes with the Sudbury Neutrino Observatory phase-III data set

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 3He 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 8B solar neutrino flux was largely independent of the methods employed in previous phases. The total flux of active neutrinos was measured to be 5.54-0.31+0.33(stat.)-0.34+0.36(syst.)×106 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 Δm2=7.59-0.21+0.19×10 -5eV2 and θ=34.4-1.2+1.3degrees

Long-Baseline Neutrino Facility (LBNF) and Deep Underground Neutrino Experiment (DUNE) Conceptual Design Report Volume 2: The Physics Program for DUNE at LBNF

The Physics Program for the Deep Underground Neutrino Experiment (DUNE) at the Fermilab Long-Baseline Neutrino Facility (LBNF) is described

Wavelength and intensity dependent studies of isolated Photosystem II reaction centers using an optical parametric amplifier

Isolated Photosystem II reaction centers were excited at five wavelengths to study the effects of excitation wavelength and intensity on energy transfer and charge separation

Femtosecond spectroscopy on PSII reaction centers: New results

Time evolution of transient absorption changes excited by pumping Photosystem II (PSII) RCs at 683 nm (where P680 absorbs) or 665 nm (where RC antenna pigments absorb) and probing at 544 nm elicited a rapid increase in absorption within the time of the pump pulse, and, subsequently, three distinct kinetic components representing decreases in absorption: A fast component with {tau}s on the order of 1--3 ps, an intermediate one with {tau}s of 10--25 ps, and a slow one with {tau}s ranging from 50--100 ps. The amplitudes of the three bleach components versus pump energy are linear up to 250 nJ at both pump wavelengths. Between 250 nJ and 1 {mu}J the amplitudes continue to increase but at a lesser slope. Zero-crossing times increase with increasing pump energy from a minimum of about 10 ps at 683 nm excitation and 20 ps at 665 nm excitation. ZCTs provide a convenient way of comparing from laboratory to laboratory the actual pump intensity seen by a sample. Whereas the amplitudes of the three kinetic components increase with pump energy, there does not seem to be a consistent change in the relative percentage of the three components over the pump energy range investigated. However, the percentage of intermediate time component appears greater, and the lifetimes of all three components increase somewhat when pumping at 665 nm vs. 683 nm. To examine this point, we obtained transient absorption spectra of PSII RCs at 500 ps and 1 ps after low energy pump pulses at 665 nm and 683 nm. At 500 ps, transient absorption spectra in the 500-nm to 600-nm range are independent of pump wavelength. This indicates that energy transfer from antenna pigments, absorbing at 665 nm, to P680 is close to 100% efficient. On the other hand, at short time there is a substantial difference in the spectra generated by the two pump wavelengths

Population genomics and phylogeography of four Australasian waterfowl

OnlinePublBiogeographic barriers can restrict gene flow, but variation in ecological drivers of dispersal influences the effectiveness of these barriers among different species. Detailed information about the genetic connectivity and movement of waterfowl across biogeographic barriers in northern Australia and Papua New Guinea is limited. We compared genetic connectivity for four species of Australasian waterfowl that vary in their capacity and predisposition for dispersal: Radjah Shelduck (Radjah radjah), Wandering Whistling Duck (Dendrocygna arcuata), Green Pygmy Goose (Nettapus pulchellus), and Pacific Black Duck (Anas superciliosa). We obtained >3,700 loci from double-digest restriction-associated DNA sequencing for 15 to 40 individuals per species and found idiosyncratic patterns of population structure among the four species. The mostly sedentary Radjah Shelduck exhibited clear genetic differences between New Guinea and Australia as well as among locations within Australia. Although the population structure was consistent with isolation by distance, the Torres Strait and Carpentaria Barrier contributed more to genetic differences than geographic distance alone. In contrast, the presumed sedentary Green Pygmy Goose did not show obvious structure. Likewise, populations of the more dispersive Wandering Whistling Duck and Pacific Black Duck were unstructured and genetically indistinguishable between southern New Guinea and northern Australia. Our data suggest that some Australo-Papuan biogeographical barriers are insufficient to impede gene flow in waterfowl species capable of dispersing great distances. In sedentary species like the Radjah Shelduck, these barriers, perhaps coupled with its ecology and natural history, restrict gene flow. Our findings bring new insight into the population ecology of Australo-Papuan waterfowl.Sara R. Seibert, Leo Joseph, Jonathan Bowers, Philip Lavretsky, Alex Drew, Ian Mason, David A. Roshier, Bulisa Iova and Jeffrey L. Peter