T. Didberidze

Characterization of Silicon Photomultipliers for nEXO

Silicon Photomultipliers (SiPMs) are attractive candidates for light detectors for next generation liquid xenon double-beta decay experiments, like nEXO (next Enriched Xenon Observatory). In this paper we discuss the requirements that the SiPMs must satisfy in order to be suitable for nEXO and similar experiments, describe the two test setups operated by the nEXO collaboration, and present the results of characterization of SiPMs from several vendors. In particular, we find that the photon detection efficiency at the peak of xenon scintillation light emission (175-178 nm) approaches the nEXO requirements for tested FBK and Hamamatsu devices. Additionally, the nEXO collaboration performed radio-assay of several grams of bare FBK devices using neutron activation analysis, indicating levels of 40K, 232Th, and 238U of the order of <; 0.15, (6.9 · 10- 4 - 1.3 · 10- 2), and <; 0.11 mBq/kg, respectively.

An RF-only ion-funnel for extraction from high-pressure gases

An RF ion-funnel technique has been developed to extract ions from a high-pressure (10 bar) noble-gas environment into a vacuum (10(-6) mbar). Detailed simulations have been performed and a prototype has been developed for the purpose of extracting Ba-136 ions from Xe gas with high efficiency. With this prototype, ions have been extracted for the first time from high-pressure xenon gas and argon gas. Systematic studies have been carried out and compared to simulations. This demonstration of extraction of ions, with mass comparable to that of the gas generating the high-pressure, has applications to Ba tagging from a Xe-gas time-projection chamber for double-beta decay, as well as to the general problem of recovering trace amounts of an ionized element in a heavy (m > 40 u) carrier gas

Spectroscopy of Ba and Ba + deposits in solid xenon for barium tagging in nEXO

Progress on a method of barium tagging for the nEXO double beta decay experiment is reported. Absorption and emission spectra for deposits of barium atoms and ions in solid xenon matrices are presented. Excitation spectra for prominent emission lines, temperature dependence, and bleaching of the fluorescence reveal the existence of different matrix sites. A regular series of sharp lines observed in

Cosmogenic backgrounds to 0νββ in EXO-200

{\mathrm{Ba}}^{+}

Measurements of the ion fraction and mobility of alpha and beta decay products in liquid xenon using EXO-200

deposits is identified with some type of barium hydride molecule. Lower limits for the fluorescence quantum efficiency of the principal Ba emission transition are reported. Under current conditions, an image of fewer than or equal to

An apparatus to manipulate and identify individual Ba ions from bulk liquid Xe

{10}^{4}

Measurement of the Drift Velocity and Transverse Diffusion of Electrons in Liquid Xenon with the EXO-200 Detector

Ba atoms can be obtained. Prospects for imaging single Ba atoms in solid xenon are discussed.

First Search for Lorentz and CPT Violation in Double Beta Decay with EXO-200

As neutrinoless double-beta decay experiments become more sensitive and intrinsic radioactivity in detector materials is reduced, previously minor contributions to the background must be understood and eliminated. With this in mind, cosmogenic backgrounds have been studied with the EXO-200 experiment. Using the EXO-200 TPC, the muon flux (through a flat horizontal surface) underground at the Waste Isolation Pilot Plant (WIPP) has been measured to be {\Phi} = 4.07

Measurements of the ion fraction and mobility of α− and β -decay products in liquid xenon using the EXO-200 detector

\pm

An Optimal Energy Estimator to Reduce Correlated Noise for the EXO-200 Light Readout

0.14 (sys)