Buffer gas

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

Control of Ion Drag in a Dusty Plasma

Abstract: A method of the control of the ion drag force acting on a dust particle in a complex plasma by choosing the composition of the gas mixture of a discharge has been proposed and experimentally implemented. The addition of a heavier additive with a lower ionization potential to the light buffer gas changes the ion composition and velocity of the ion flow. As a result, the ion drag force changes significantly. The experiments have been performed with the discharge in a helium-xenon mixture in a magnetic field. The measured angular rotation velocity of the dusty structure is in agreement with the numerical estimate of the ion drag force varying (increasing) in the presence of small (<5%) xenon additive. The proposed method can be used to create plasma crystals with new properties.

Passive atomic frequency standard based on coherent population trapping in 87 Rb using injection-locked lasers

Abstract: We present a microwave frequency standard based on coherent population trapping (CPT) in the 87Rb D1 line. The CPT spectrum is obtained using two Raman lasers with a 6.8 GHz frequency offset by injection locking of a master laser to a slave laser. We have constructed an atomic clock employing a 5 cm long Rb vapor cell confined with 6.67 kPa neon buffer gas at 70 °C. Using this system, we improve the CPT contrast through the elimination of undesired off-resonant fields created by the direct modulation method. We measured the frequency shift of the CPT signal as a function of the temperature of the Rb cell and estimated it to be approximately 1.3 ×10−9/K. The frequency of a 10 MHz crystal oscillator has been stabilized to the CPT spectrum between the two ground states in 87Rb. The relative frequency stability is approximately 2.3×10−12 for an average time of 68 s.

Enhanced Buffer Gas Loading: Cooling and Trapping of Atoms with Low Effective Magnetic Moments

Abstract: A new technique for buffer gas loading is described. This technique greatly extends the range of atoms and molecules that may be magnetically trapped at low temperature. The advance is made possible by the rapid removal of the buffer gas on a time scale one hundred times greater than in previous buffer gas loading experiments. A new cryogenic valve is developed and employed. The following benchmarks were attained in our first experimental run; approximately 10 atoms with effective magnetic moments μeff & 3μB were trapped and thermally isolated with near unit efficiency, ~ 10 μeff = 2μB atoms were trapped and thermally isolated, and ~ 10 μeff = 1μB atoms were trapped, but without thermal isolation. For comparison, all previous buffer gas loading experiments that achieved thermal isolation after trapping were done with atoms having a magnetic moment of at least 6μB. In our second run of the experiment, better temperature management allowed us to increase the number of trapped and thermally isolated μeff = 2μB atoms to ~10 and trapped μeff = 1μB atoms to ~ 10. The performance of the present apparatus is limited by the presence of a desorbing helium film that compromises the vacuum in the cell after the bulk of the buffer gas is removed. Future improvements to address this problem are suggested that will likely allow for efficient trapping and thermal isolation of atoms and molecules with magnetic moments as low as 1μB. Analysis of the trapping and pumping dynamics is presented.

Diode laser spectroscopy of He, N2 and air broadened water vapour transitions belonging to the (2ν1 + ν2 + ν3) overtone band

Abstract: The line shape parameters of rovibrational transitions of water vapour belonging to the (2ν1 + ν2 + ν3) overtone band due to collisions between absorber molecules and noble gas helium have been measured in the spectral range between 11988.494 cm−1 and 12218.829 cm−1 using NIR diode laser spectrometer. In addition nitrogen and air broadening effects on some water vapour transitions belonging to the same band have also been studied. Wavelength modulation spectroscopy along with phase sensitive detection technique are used to record first derivative (1f) signal of buffer gas broadened water vapour transitions. Observed line shapes are fitted to standard Voigt profiles by non-linear least squares fitting program to extract the line shape parameters, like line strength and pressure broadening coefficients. The broadening effects induced by different types of buffer gases on water vapour line shapes are compared. Rotational quantum number (J) dependence of broadening coefficients of water vapour transitions is ...