Buffer gas

About: Buffer gas is a research topic. Over the lifetime, 3565 publications have been published within this topic receiving 47283 citations.

Rb-Xe spin relaxation in dilute Xe mixtures.

Abstract: We present measurements of spin-relaxation of Rb atoms in He(98%)-N2(1%)-Xe(1%) mixtures similar to those used in magnetic resonance imaging polarizers. The pressure dependence allows us to separate out contributions from Rb-Xe van der Waals molecules and binary collisions. For the first time, we observe the predicted increase in the molecular contribution at high pressure. Our data suggest that the deduced molecular breakup rate has a strong temperature dependence. The realization of magnetic resonance imaging of human subjects using hyperpolarized noble gases @1# has stimulated the intense development of Xe-Rb spin-exchange optical pumping @2# in high pressure buffer gases @3‐5#. The need to minimize the mismatch between the Rb absorption linewidth and the linewidth of inexpensive, high power but broadband diode laser sources requires pressure broadening the Rb resonance lines with many atmospheres of He gas, chosen for its weak spin-relaxation properties @6#. Despite the widespread use of high pressure He for Xe-Rb spin exchange, there exist no systematic studies of spin relaxation and spin exchange rates under such conditions, as most of the pioneering work in Xe spin-relaxation and spin-exchange either had no buffer gas @7# or used N2 buffer gas @8#. Two recent experiments report relaxation rates measured at a single pressure and temperature @4,5#. In this paper we report measurements of spin-relaxation rates at 80 and 150 °C, in

Sensor for determining gas components and/or gas concentrations of gas mixtures

Abstract: A method of determining at least one of gas constituents and gas concentrations of a gas mixture such as exhaust gas from an internal combustion engine includes producing a change in gas concentration of the gas mixture at a semiconductor gas sensor by pumping a variable supply of oxygen to the semiconductor gas sensor by means of a solid electrolyte pumping cell; detecting at least one reaction speed selected from the group consisting of adsorption speed and desorption speed caused by the change in gas concentration as a signal from the semiconductor gas sensor which is a reply function; evaluating the signal from the semiconductor gas sensor over time to provide a time response of the reply function; and comparing the time response of the reply function with a stored, standardized time response of different gas constituents whereby at least one of the gas constituents and the gas concentrations of the gas mixture are determined.

Cryogenic Ion Trapping Systems with Surface-Electrode Traps

Abstract: We present two simple cryogenic RF ion trap systems in which cryogenic temperatures and ultra high vacuum pressures can be reached in as little as 12 hours. The ion traps are operated either in a liquid helium bath cryostat or in a low vibration closed cycle cryostat. The fast turn around time and availability of buffer gas cooling made the systems ideal for testing surface-electrode ion traps. The vibration amplitude of the closed cycled cryostat was found to be below 106 nm. We evaluated the systems by loading surface-electrode ion traps with $^{88}$Sr$^+$ ions using laser ablation, which is compatible with the cryogenic environment. Using Doppler cooling we observed small ion crystals in which optically resolved ions have a trapped lifetime over 2500 minutes.

Infrared Lasers Resulting from Giant Pulse Laser Excitation of Alkali Metal Molecules

Abstract: Infrared laser action is observed to occur in vapors of K, Rb, and Cs photoexcited by various giant pulse laser beams. The mechanism of excitation involves two‐photon absorption by the molecular species followed by dissociation into various excited atomic states. In the case of cesium, anomalously long infrared laser pulses are obtained when helium buffer gas is present. A collisional mechanism is invoked to explain this phenomenon. Self‐focusing of a ruby laser beam is also observed to occur in cesium–helium vapor under certain conditions.

A highly miniaturized vacuum package for a trapped ion atomic clock

Abstract: We report on the development of a highly miniaturized vacuum package for use in an atomic clock utilizing trapped ytterbium-171 ions. The vacuum package is approximately 1 cm3 in size and contains a linear quadrupole RF Paul ion trap, miniature neutral Yb sources, and a non-evaporable getter pump. We describe the fabrication process for making the Yb sources and assembling the vacuum package. To prepare the vacuum package for ion trapping, it was evacuated, baked at a high temperature, and then back filled with a helium buffer gas. Once appropriate vacuum conditions were achieved in the package, it was sealed with a copper pinch-off and was subsequently pumped only by the non-evaporable getter. We demonstrated ion trapping in this vacuum package and the operation of an atomic clock, stabilizing a local oscillator to the 12.6 GHz hyperfine transition of 171Y b+. The fractional frequency stability of the clock was measured to be 2 × 10−11/τ1/2.