S. Riordan

Demonstration of Single-Barium-Ion Sensitivity for Neutrinoless Double-Beta Decay Using Single-Molecule Fluorescence Imaging

A new method to tag the barium daughter in the double-beta decay of ^{136}Xe is reported. Using the technique of single molecule fluorescent imaging (SMFI), individual barium dication (Ba^{++}) resolution at a transparent scanning surface is demonstrated. A single-step photobleach confirms the single ion interpretation. Individual ions are localized with superresolution (∼2u2009u2009nm), and detected with a statistical significance of 12.9σ over backgrounds. This lays the foundation for a new and potentially background-free neutrinoless double-beta decay technology, based on SMFI coupled to high pressure xenon gas time projection chambers.

Helium–Xenon mixtures to improve the topological signature in high pressure gas xenon TPCs

Abstract Within the framework of xenon-based double beta decay experiments, we propose the possibility to improve the background rejection of an electroluminescent Time Projection Chamber (EL TPC) by reducing the diffusion of the drifting electrons while keeping nearly intact the energy resolution of a pure xenon EL TPC. Based on state-of-the-art microscopic simulations, a substantial addition of helium, around 10 or 15xa0%, may reduce drastically the transverse diffusion down to 2.5xa0mm/ m from the 10.5xa0mm/ m of pure xenon. The longitudinal diffusion remains around 4xa0mm/ m . Light production studies have been performed as well. They show that the relative variation in energy resolution introduced by such a change does not exceed a few percent, which leaves the energy resolution practically unchanged. The technical caveats of using photomultipliers close to an helium atmosphere are also discussed in detail.

Study of the loss of xenon scintillation in xenon-trimethylamine mixtures

Abstract This work investigates the capability of TMA ((CH 3 ) 3 N) molecules to shift the wavelength of Xe VUV emission (160–188xa0nm) to a longer, more manageable, wavelength (260–350xa0nm). Light emitted from a Xe lamp was passed through a gas chamber filled with Xe-TMA mixtures at 800xa0Torr and detected with a photomultiplier tube. Using bandpass filters in the proper transmission ranges, no reemitted light was observed experimentally. Considering the detection limit of the experimental system, if reemission by TMA molecules occurs, it is below 0.3% of the scintillation absorbed in the 160–188xa0nm range. An absorption coefficient value for xenon VUV light by TMA of 0.43xa0±xa00.03xa0cm −1 Torr −1 was also obtained. These results can be especially important for experiments considering TMA as a molecular additive to Xe in large volume optical time projection chambers.