Near-intrinsic energy resolution for 30-662 keV gamma rays in a high pressure xenon electroluminescent TPC

We present the design, data and results from the NEXT prototype for Double Beta and Dark Matter (NEXT-DBDM) detector, a high-pressure gaseous natural xenon electroluminescent time projection chamber (TPC) that was built at the Lawrence Berkeley National Laboratory. It is a prototype of the planned NEXT-100 136Xe neutrino-less double beta decay (0νββ) experiment with the main objectives of demonstrating near-intrinsic energy resolution at energies up to 662 keV and of optimizing the NEXT-100 detector design and operating parameters. Energy resolutions of ∼1% FWHM for 662 keV gamma rays were obtained at 10 and 15 atm and ∼5% FWHM for 30 keV fluorescence xenon X-rays. These results demonstrate that 0.5% FWHM resolutions for the 2,459 keV hypothetical neutrino-less double beta decay peak are realizable. This energy resolution is a factor 7 to 20 better than that of the current leading 0νββ experiments using liquid xenon and thus represents a significant advancement. We present also first results from a track imaging system consisting of 64 silicon photo-multipliers recently installed in NEXT-DBDM that, along with the excellent energy resolution, demonstrates the key functionalities required for the NEXT-100 0νββ search

Ethyl cellulose, cellulose acetate and carboxymethyl cellulose microstructures prepared using electrohydrodynamics and green solvents

Cellulose derivatives are an attractive sustainable material used frequently in biomaterials, however their solubility in safe, green solvents is not widely exploited. In this work three cellulose derivatives; ethyl cellulose, cellulose acetate and carboxymethyl cellulose were subjected to electrohydrodynamic processing. All were processed with safe, environmentally friendly solvents; ethanol, acetone and water. Ethyl cellulose was electrospun and an interesting transitional region was identified. The morphological changes from particles with tails to thick fibres were charted from 17 to 25 wt% solutions. The concentration and solvent composition of cellulose acetate (CA) solutions were then changed; increasing the concentration also increased fibre size. At 10 wt% CA, with acetone only, fibres with heavy beading were produced. In an attempt to incorporate water in the binary solvent system to reduce the acetone content, 80:20 acetone/water solvent system was used. It was noted that for the same concentration of CA (10 wt%), the beading was reduced. Finally, carboxymethyl cellulose was electrospun with poly(ethylene oxide), with the molecular weight and polymer compositions changed and the morphology observed

Structure, and kinetics of the thermal decomposition of organic phosphite ozonides

Activation parameters for uncatalyzed loss of oxygen from phosphite ozonide solutions (R alkyl or aryl) (RO)3P + O3 → (RO)3PO3 → (RO)3PO + O2 were measured for a number of different phosphites in several solvents. Triphenyl phosphite ozonide in toluene, chlorobenzene and acetonitrile showed Ea (kcal mol-1) = 19.4 - 20.1 and log A = 13.5 - 13.6, where A is in reciprocal seconds, whereas in dichloromethane the rate constants were not very reproducible and depended on the precautions followed to exclude moisture from the ozonide preparations. Activation parameters for triphenyl phosphite ozonide in dichloromethane reported in the literature or derived from reported rate constants vary from log A = 8.1 to log A = 11.9 and from Ea (kcal mol-1) = 14.4 to Ea = 17.2. Other phosphite ozonides show activation parameters which range approximately between the extremes given above for triphenyl phosphite ozonide, even in solvents other than dichloromethane. Possible reasons for these differences are discussed together with earlier theories to account for them. A molecular weight determination and the 31P nuclear magnetic resonance spectrum of trimethylolpropane phosphite ozonide are consistent with a monomeric non-equilibrating structure. © 1984