Methane Production from Carbondioxide in Polluted Areas Using Graphene Doped Ni/ NiO Nanocomposite via Photocatalysis

Background: Photocatalysis for the production of solar fuels and particularly to perform CO2 reduction with a sufficiently high efficiency depends to the presence of H2 and absence of H2 O using graphene doped Ni/ NiO nanocomposite. Objective: To examine the methane production from carbondioxide in polluted areas using graphene doped Ni/ NiO nanocomposite via photocatalysis with the use of dimethylaniline and xylene as electron donors. Methods: With 2 mg/l graphene doped Ni/ NiO nanocomposite with a Ni content of 19% wt from 786 μmol/h CO2 gas 563 μl CH4 /g Ni.h was obtained at 160oC temperature and the quantum yield was detected as 1.99%. It was found that H2 O has a negative influence on the photocatalytic activity. Under continuous flow operation, water molecules were easier desorbed from the graphene doped Ni/NiO photocatalyst Results: The maximum CH4 production rate was 650 μl/h for 2.4 mg of graphene doped Ni/ NiO nanocomposite after a detectione time of 17 min. Dimethylaniline and xylene were used as electron donors and 1.2 ml/l dimethylaniline and 0.9 ml/l xylene enhanced the CH4 productions by 8% and 12% as quenching factor. Conclusion: Photocatalysis methods was effected for methane production from carbondioxide in polluted areas using graphene doped Ni/ NiO nanocomposite with the use of dimethylaniline and xylene as electron donors.

Characterization of SABRE crystal NaI-33 with direct underground counting

Ultra-pure NaI(Tl) crystals are the key element for a model-independent verification of the long standing DAMA result and a powerful means to search for the annual modulation signature of dark matter interactions. The SABRE collaboration has been developing cutting-edge techniques for the reduction of intrinsic backgrounds over several years. In this paper we report the first characterization of a 3.4 kg crystal, named NaI-33, performed in an underground passive shielding setup at LNGS. NaI-33 has a record low $$^{39}$$ 39 K contamination of 4.3 ± 0.2 ppb as determined by mass spectrometry. We measured a light yield of 11.1 ± 0.2 photoelectrons/keV and an energy resolution of 13.2% (FWHM/E) at 59.5 keV. We evaluated the activities of $$^{226}$$ 226 Ra and $$^{228}$$ 228 Th inside the crystal to be $$5.9\pm 0.6~\upmu $$ 5.9 ± 0.6 μ Bq/kg and $$1.6\pm 0.3~\upmu $$ 1.6 ± 0.3 μ Bq/kg, respectively, which would indicate a contamination from $$^{238}$$ 238 U and $$^{232}$$ 232 Th at part-per-trillion level. We measured an activity of 0.51 ± 0.02 mBq/kg due to $$^{210}$$ 210 Pb out of equilibrium and a $$\alpha $$ α quenching factor of 0.63 ± 0.01 at 5304 keV. We illustrate the analyses techniques developed to reject electronic noise in the lower part of the energy spectrum. A cut-based strategy and a multivariate approach indicated a rate, attributed to the intrinsic radioactivity of the crystal, of $$\sim $$ ∼ 1 count/day/kg/keV in the [5–20] keV region.

Luminescence Response and Quenching Models for Heavy Ions of 0.5 keV to 1 GeV/n in Liquid Argon and Xenon

Biexcitonic collision kinetics with prescribed diffusion in the ion track core have been applied for scintillation response due to heavy ions in liquid argon. The quenching factors q = EL/E, where E is the ion energy and EL is the energy expended for luminescence, for 33.5 MeV/n 18O and 31.9 MeV/n 36Ar ions in liquid Ar at zero field are found to be 0.73 and 0.46, compared with measured values of 0.59 and 0.46, respectively. The quenching model is also applied for 80–200 keV Pb recoils in α-decay, background candidates in direct dark matter searches, in liquid argon. Values obtained are ~0.09. A particular feature of Birks’ law has been found and exploited in evaluating the electronic quenching factor qel in liquid Xe. The total quenching factors qT for 0.5–20 keV Xe recoils needed for weakly interacting massive particle (WIMP) searches are estimated to be ~0.12–0.14, and those for Pb recoils of 103 and 169 keV are 0.08 and 0.09, respectively. In the calculation, the nuclear quenching factor qnc = Eη/E, where Eη is the energy available for the electronic excitation, is obtained by Lindhard theory and a semi-empirical theory by Ling and Knipp. The electronic linear energy transfer plays a key role.

Anisotropic response measurements of ZnWO4 scintillators to neutrons for developing a direction-sensitive dark matter detector

The scintillation yields of ZnWO$_4$ crystals change depending on the incident direction of particles. This property can be used as a direction-sensitive dark matter detector, so we investigated the ZnWO$_4$ light yields ratio of neutron-induced nuclear recoils to gamma-ray-induced electron recoils (quenching factor). Two surfaces almost perpendicular to the crystal axis of ZnWO$_4$ were irradiated with a quasi-monochromatic neutron beam of 0.885 MeV, and the quenching factors of both surfaces for the oxygen-nucleus recoil in the ZnWO$_4$ crystal were measured. The obtained quenching factors of the two surfaces were $0.235 \pm 0.026$ and $0.199 \pm 0.020$, respectively, confirming 15.3% anisotropy.

SABRE and the Stawell Underground Physics Laboratory Dark Matter Research at the Australian National University

The direct detection of dark matter is a key problem in astroparticle physics that generally requires the use of deep-underground laboratories for a low-background environment where the rare signals from dark matter interactions can be observed. This work reports on the Stawell Underground Physics Laboratory – currently under construction and the first such laboratory in the Southern Hemisphere – and the associated research program. A particular focus will be given to ANU’s contribution to SABRE, a NaI:Tl dark matter, direct detection experiment that aims to confirm or refute the long-standing DAMA result. Preliminary measurements of the NaI:Tl quenching factor and characterisation of the SABRE liquid scintillator veto are reported.