Buffer gas

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

A kinetic model of the sustained discharge HgBr laser

Abstract: A kinetic model of the sustained discharge Ar/HgBr2 laser is developed from an experimental base. The choice of Ar as the buffer gas is supported by measurements of the specific fluorescence and laser efficiency in the buffer mixtures (Ar, Ar+5% Xe, Ne+10% Xe, Ne+10% N2). A computational treatment of the coupled photon and kinetic equations is described. Gain measurements determine a peak HgBr (B‐X) stimulated emission cross section of 1.6×10−16 cm2±20% at 502 nm. Absorption measurements between 515 and 530 nm show the presence of a large, broad band absorption tentatively assigned to HgBr+2 with a cross section of 2×10−18 cm2. An upper bound of 5×10−9 cm3 sec−1 is placed on the rate constant for electron collisional quenching of the HgBr(B) state. The laser extraction efficiency of 65% is modeled by a lower level collisional deactivation by Ar with a rate constant 6.0×10−12 cm3 sec−1. Discharge impedance is measured as a function of E/N and the ionizing electron beam current density. Using the new data a...

Non-negligible collisions of alkali atoms with background gas in buffer-gas-free cells coated with paraffin

Abstract: We measured the rate of velocity-changing collisions (VCCs) between alkali atoms and background gas in buffer-gas-free anti-relaxation-coated cells. The average VCC rate in paraffin-coated rubidium vapor cells prepared in this work was $$1\times 10^{6} \,\hbox {s}^{-1}$$ , which corresponds to ~1 mm in the mean free path of rubidium atoms. This short mean free path indicates that the background gas is not negligible in the sense that alkali atoms do not travel freely between the cell walls. In addition, we found that a heating process known as “ripening” increases the VCC rate, and also confirmed that ripening improves the anti-relaxation performance of the coatings.

Mass selectivity of dipolar resonant excitation in a linear quadrupole ion trap.

Abstract: RATIONALE For mass analysis, linear quadrupole ion traps operate with dipolar excitation of ions for either axial or radial ejection. There have been comparatively few computer simulations of this process. We introduce a new concept, the excitation contour, S(q), the fraction of the excited ions that reach the trap electrodes when trapped at q values near that corresponding to the excitation frequency. METHODS Ion trajectory calculations are used to calculate S(q). Ions are given Gaussian distributions of initial positions in x and y, and thermal initial velocity distributions. To model gas damping, a drag force is added to the equations of motion. The effects of the initial conditions, ejection Mathieu parameter q, scan speed, excitation voltage and collisional damping, are modeled. RESULTS We find that, with no buffer gas, the mass resolution is mostly determined by the excitation time and is given by R~dβdqqn, where β(q) determines the oscillation frequency, and n is the number of cycles of the trapping radio frequency during the excitation or ejection time. The highest resolution at a given scan speed is reached with the lowest excitation amplitude that gives ejection. The addition of a buffer gas can increase the mass resolution. The simulation results are in broad agreement with experiments. CONCLUSIONS The excitation contour, S(q), introduced here, is a useful tool for studying the ejection process. The excitation strength, excitation time and buffer gas pressure interact in a complex way but, when set properly, a mass resolution R0.5 of at least 10,000 can be obtained at a mass-to-charge ratio of 609. Copyright © 2014 John Wiley & Sons, Ltd.

Effect of hydrogen on the average output power of the UV Cu/sup +/ Ne-CuBr laser

Abstract: The effect of different additives-air, synthetic air, N/sub 2/, O/sub 2/, CO/sub 2/, He, Ar, Xe, and H/sub 2/, to the neon buffer gas on the average output power of a UV Cu/sup +/ Ne-CuBr is investigated. It is found that the addition of small amounts of hydrogen, 0.02-0.04 torr, leads to an increase by more than twice of the average output power for simultaneous laser oscillation at the five Cu/sup +/ lines-248.6, 252.9, 259.7, 260.0, and 270.3 nm.