W. Fairbank

Search for Neutrinoless Double-Beta Decay in 136 Xe with EXO-200

We report on a search for neutrinoless double-beta decay of 136Xe with EXO-200. No signal is observed for an exposure of 32.5 kg yr, with a background of ∼1.5×10(-3)  kg(-1) yr(-1)  keV(-1) in the ±1σ region of interest. This sets a lower limit on the half-life of the neutrinoless double-beta decay T(1/2)(0νββ)(136Xe)>1.6×10(25)  yr (90% C.L.), corresponding to effective Majorana masses of less than 140-380 meV, depending on the matrix element calculation.

Search for Neutrinoless Double-Beta Decay in 136Xe with EXO-200

We report on a search for neutrinoless double-beta decay of 136Xe with EXO-200. No signal is observed for an exposure of 32.5 kg yr, with a background of ∼1.5×10(-3)  kg(-1) yr(-1)  keV(-1) in the ±1σ region of interest. This sets a lower limit on the half-life of the neutrinoless double-beta decay T(1/2)(0νββ)(136Xe)>1.6×10(25)  yr (90% C.L.), corresponding to effective Majorana masses of less than 140-380 meV, depending on the matrix element calculation.

Multiwatt operation of Cu II and Ag II hollow cathode lasers

We report multiwatt pulsed (120 μs pulsewidth, 40Hz) laser operation of silver and copper hollow cathode lasers. Peak output powers of 65 mW at 224 nm, 500 mW at 248 nm, 1.3 W at 318.1 nm, and 2.3 W at 478.8 nm have been achieved. Measurements of small-signal gains of selected laser transitions and new laser lines in Cu, Ag, Kr, and Ar are presented.

Hollow‐cathode excitation of ion laser transitions in noble‐gas mixtures

Excitation of laser transitions in He‐Kr, He‐Ar, Ne‐Xe, and He‐Ne‐Xe mixtures was investigated in hollow‐cathode discharges. The dominant excitation mechanism of the noble‐gas ions was found to be collisions of the second kind between the ground‐state noble‐gas ions and helium or neon metastables. Based on gain and absorption spectroscopy measurements, the cross section for this mechanism was estimated to be ⩾10−14 cm2. New laser transitions in noble‐gas and copper ions are also reported.

An improved measurement of the 2\nu \beta \beta\ half-life of Xe-136 with EXO-200

We report on an improved measurement of the 2\nu \beta \beta\ half-life of Xe-136 performed by EXO-200. The use of a large and homogeneous time projection chamber allows for the precise estimate of the fiducial mass used for the measurement, resulting in a small systematic uncertainty. We also discuss in detail the data analysis methods used for double-beta decay searches with EXO-200, while emphasizing those directly related to the present measurement. The Xe-136 2\nu \beta \beta\ half-life is found to be 2.165 +- 0.016 (stat) +- 0.059 (sys) x 10^21 years. This is the most precisely measured half-life of any 2\nu \beta \beta\ decay to date.

Observation of single collisionally cooled trapped ions in a buffer gas

Individual Ba ions are trapped in a gas-filled linear ion trap and observed with a high signal-to-noise ratio by resonance fluorescence. Single-ion storage times of {approx}5 min ({approx}1 min) are achieved using He (Ar) as a buffer gas at pressures in the range 8x10{sup -5}-4x10{sup -3} torr. Trap dynamics in buffer gases are experimentally studied in the simple case of single ions. In particular, the cooling effects of light gases such as He and Ar and the destabilizing properties of heavier gases such as Xe are studied. A simple model is offered to explain the observed phenomenology.

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

New infrared laser transitions in copper and silver hollow cathode discharge

We have investigated infrared laser action in the 0.8–2‐μ region originating from silver and copper atoms and ions excited in hollow cathode discharges. 34 new laser lines are reported. We also observed eight Ar I and one Xe I infrared laser lines, most of which have been observed previously. The discharge conditions for these transitions and their excitation mechanisms are discussed.

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

Prospects for Barium Tagging in Gaseous Xenon

{\mathrm{Ba}}^{+}