nEXO is a 5-ton liquid enriched-xenon time projection chamber (TPC) to search for neutrinoless double-beta decay, designed to have the sensitivity to completely probe the inverted mass hierarchy of ...Majorana neutrinos. The detector will accommodate—as a background reduction technique—a system to recover and identify the barium decay product. This upgrade will allow a background-free measurement of neutrinoless double-beta decay and increase the half-life sensitivity of the experiment by at least one order of magnitude. Ongoing research and development includes a system to test barium extraction from liquid xenon using surface adsorption and Resonance Ionization Spectroscopy (RIS).
The EXO-200 Collaboration is searching for neutrinoless double β decay using a liquid xenon (LXe) time projection chamber. This measurement relies on modeling the transport of charge deposits ...produced by interactions in the LXe to allow discrimination between signal and background events. Here we present measurements of the transverse diffusion constant and drift velocity of electrons at drift fields between 20 V/cm and 615 V/cm using EXO-200 data. At the operating field of 380 V/cm EXO-200 measures a drift velocity of 1.705+0.014 -0.010 mm/μs and a transverse diffusion coefficient of 55 ± 4 cm2/s.
A search for Lorentz- and CPT-violating signals in the double beta decay spectrum of super(136) Xe has been performed using an exposure of 100kgmiddotyr with the EXO-200 detector. No significant ...evidence of the spectral modification due to isotropic Lorentz-violation was found, and a two-sided limit of -2.65x10 super(-5)GeV(ProQuest: Formulae and/or non-USASCII text omitted) <7.60x10 super(-6)GeV (90% C.L.) is placed on the relevant coefficient within the Standard-Model Extension (SME). This is the first experimental study of the effect of the SME-defined oscillation-free and momentum-independent neutrino coupling operator on the double beta decay process.
Atherosclerosis is a progressive disease characterised in part by an imbalance of endothelial decline and endothelial repair. Erythropoietin has been connected to vasculoprotective effects such as ...enhanced nitric oxide production in endothelial cells and mobilisation of endothelial progenitor cells (EPC).
To determine the effect of erythropoietin on endothelial function and EPC mobilisation in humans with atherosclerosis.
A prospective single-blind monocentric study of 20 patients randomly assigned to the test drug or placebo treatment over 4 weeks.
20 Patients with stable coronary artery disease receiving optimal medical treatment with either weekly subcutaneous injections of saline (placebo) or the recombinant erythropoietin darbepoetin (60 μg/injection) over 3 consecutive weeks. At the initial and final visits, flow mediated dilatation (FMD) was determined by ultrasound. The number of EPC was determined as the number of CD34/CD133 positive mononuclear cells in peripheral blood.
Treatment with darbepoetin resulted in a significantly improved FMD in each patient, whereas no difference was seen in placebo-treated patients. The FMD of darbepoetin-treated patients increased by 7.5±1.64%. Additionally, an increase in peripheral blood EPC of 50±24% was seen.
Darbepoetin given in addition to optimal medical treatment resulted in a significantly improved endothelial function in patients with coronary artery disease, indicating a promising new atheroprotective treatment option.
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•We present a new and simple design of an RF-only ion funnel.•Longitudinal ion transport is provided by the residual gas flow through the funnel thus no DC drag field is required.•The ...presented ion funnel allows for ion extraction from argon and xenon gas from up to 10bar to 10−3mbar in only one step with very high efficiency.•First experimental results of ion extraction from high-pressure noble gas have been performed and are compared with gas dynamic and ion trajectory calculations.
An RF ion-funnel technique has been developed to extract ions from a high-pressure (10bar) noble-gas environment into a vacuum (10−6mbar). Detailed simulations have been performed and a prototype has been developed for the purpose of extracting 136Ba 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>40u) carrier gas.
Cosmogenic backgrounds to 0νββ in EXO-200 Albert, J.B.; Auty, D.J.; Barbeau, P.S. ...
Journal of cosmology and astroparticle physics,
04/2016, Letnik:
2016, Številka:
4
Journal Article
Recenzirano
Odprti dostop
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 $Φ$ = 4.07±0.14 (sys)±0.03 (stat)×10-7 cm-2 s-1, with a vertical intensity of $I_v$ = 2.97+0.14-0.13 (sys) ± 0.02 (stat) × 10-7 cm-2 s-1 sr-1. Simulations of muon-induced backgrounds identified several potential cosmogenic radionuclides, though only 137Xe is a significant background for the 136Xe $0νββ$ search with EXO-200. Muon-induced neutron backgrounds were measured using $γ$-rays from neutron capture on the detector materials. This provided a measurement of 137Xe yield, and a test of the accuracy of the neutron production and transport simulations. The independently measured rates of 136Xe neutron capture and of 137Xe decay agree within uncertainties. Geant4 and FLUKA simulations were performed to estimate neutron capture rates, and these estimates agreed to within ~ 40% or better with measurements. The ability to identify 136Xe($n,γ$) events will allow for rejection of 137Xe backgrounds in future $0νββ$ analyses.
Characterization of large area APDs for the EXO-200 detector Neilson, R.; LePort, F.; Pocar, A. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
09/2009, Letnik:
608, Številka:
1
Journal Article
Recenzirano
Enriched Xenon Observatory (EXO)-200 uses 468 large area avalanche photodiodes (LAAPDs) for detection of scintillation light in an ultra-low-background liquid xenon (LXe) detector. We describe ...initial measurements of dark noise, gain and response to xenon scintillation light of LAAPDs at temperatures from room temperature to 169
K—the temperature of liquid xenon. We also describe the individual characterization of more than 800 LAAPDs for selective installation in the EXO-200 detector.
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