Buffer gas

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

Comparison of magnetron sputter deposition conditions in neon, argon, krypton, and xenon discharges

Abstract: The ion and deposition fluxes to the substrate during sputtering of a vanadium target in neon, argon, krypton, and xenon discharges were measured as a function of the discharge power and gas pressure. The measurements of the deposition fluxes were also compared with calculations obtained using an analytical model for transport of the sputtered species through the gas discharge. The calculation takes into account both the ballistic and thermal components of the deposition flux. Overall, a good agreement between the calculated and the experimentally measured values was obtained. The results show that, at a constant discharge current, the vanadium flux at the substrate position is a strong function of both pressure and the type of inert gas used. The ion flux, on the other hand, remains relatively constant as the gas and pressure are changed. This implies that the ion‐to‐neutral arrival rate ratio was dominated by changes in the neutral deposition flux and it was found to increase with pressure, remain relatively constant with power at low pressures, and decrease with power at high pressures. By increasing the field strength of the outer pole in the magnetron source (unbalanced magnetron source of type II), the ion flux impinging the substrate was strongly increased for all pressures, while the vanadium deposition flux remained the same as in the ‘‘balanced’’ magnetron configuration.

Wide aperture self‐sustained discharge KrF and XeCl lasers

Abstract: A UV‐preionized rare‐gas halide laser with a large aperture to 7×7 cm2 and active volume of 4 l has been operated at a high pressure regime of 5 atm. Beam profile measurements at the midplane between electrodes have shown the beam widths of 7 cm at a half‐energy density both in KrF and XeCl. The improvement in discharge homogeneity and extension of the optical pulse duration have been obtained by the peaking of the discharge current with a small stray capacitance between the rail gap and the laser head as well as by the use of Ne rather than He as a buffer gas, resulting in the output energy of 13.8 J in XeCl and 5.0 J in KrF.

Magnetic trapping of atomic chromium

Abstract: Recently we demonstrated the technique of buffer-gas loading of neutral species by using it to load a magnetic trap with europium atoms @1,2# The atom density achieved in that experiment ( n;10 12 cm 23 ! is comparable to the highest densities achieved in magneto-optical traps, and the number trapped ( N;10 12 ) is an order of magnitude higher than can currently be obtained with light-force traps @3# The buffer-gas method promises the extension of magnetic trapping and evaporative cooling to species other than alkali atoms, and should open the way for producing ultracold, dense samples in a variety of atomic and molecular species Herein, we report the magnetic trapping of atomic chromium via buffer-gas loading Chromium has many properties of interest It is a metal dissimilar to europium; trapping it further demonstrates the generality of buffer-gas loading Chromium’s large magnetic moment of 6 m B ~Bohr magneton! allows for trapping at elevated buffer-gas temperatures, opening up the possibility to trap it with a simple pumped liquid helium cryostat Study of chromium is also motivated by its applications in atom lithography @4,5# As it has four naturally occurring isotopes, three bosons and one fermion, trapping could open the door to the study of chromium BoseEinstein condensates or degenerate Fermi gases @6‐9# The principles of buffer-gas loading and the specifics of our apparatus are outlined in previous papers @1,2# We give a brief description below Our magnetic trap is a linear quadrupole field formed by two anti-Helmholtz coils The trapping region is filled with helium buffer gas The buffer gas is maintained at cryogenic temperatures by a dilution refrigerator The species of interest ~atomic chromium in this case! is introduced into the trap, where it diffuses through the helium gas and quickly thermalizes with it via elastic collisions The atoms in the weak-field-seeking magnetic states are contained by the magnetic fields, but as the atoms are thermally distributed, they evaporate from the trap at a rate determined by h, the ratio of the trap depth to the temperature of the atoms For a sufficiently large h, this evaporation is slow enough that a large fraction of the atoms may be held for a long enough time that the ~nonmagnetic! helium gas can be ~cryo-!pumped out of the trapping region This leaves a thermally isolated, trapped sample Because this technique relies only on elastic collisions with the buffer gas and on the magnetic state of the species, it should be applicable to any magnetic species that can be cleanly introduced into the cryogenic environment In our experiment, Cr atoms are produced, thermalized, and trapped within a copper cell There is a fused silica window on the bottom of the cell to permit optical access ~for detection and ablation! and a mirror on the top of the cell to retroreflect the probe beam for absorption spectroscopy of the trapped sample Resistance thermometry is used to determine the cell temperature Additional resistors attached to the cell are used as heaters The cell is filled with either 3 He or 4 He buffer gas A sufficient amount of 3 He ( 4 He) is present so that at temperatures above 03 K ~09 K! the density is approximately 10 17 cm 23 Below these temperatures, the density is determined by the helium vapor pressure The Cr atoms are brought into the gas phase by single pulse laser ablation of a solid sample of isotopically pure 52 Cr The solid 52 Cr is positioned at the edge of the trapping region inside the cell A doubled yttrium-aluminum-garnet laser with typical ablation pulse energy of 25 mJ at 532 nm is used for ablation The atoms are detected by laser absorption spectroscopy on the a 7 S3$z 7 P3 transition at 23 386 cm 21

Experimental study of a pre-ionized high power pulsed magnetron discharge

Abstract: This paper is focused on experimental studies of a high power pulsed magnetron discharge stabilized by low current pre-ionization. Time resolved studies were performed for a Cu target by optical emission spectroscopy and electrical measurements for different pressures of Ar buffer gas. Due to the elimination of the statistical delay time and a fast discharge current rise the quasi-stationary state was reached in 6 µs. The quasi-stationary state is characterized by an extremely high and pressure independent discharge current density of ~10 A cm−2 and stable Cu+ and Cu++ emissions. Such fast discharge dynamics permits the magnetron cathode current to be driven with a pulse of duration of the order of a few µs, significantly shorter than in other devices. During this short time, the plasma does not have time to undergo the transition from the glow to the arc discharge even at the extremely high cathode loads met in our case. Different stages of the fast discharge development are identified and the composition of the magnetized plasma as a function of the pressure is discussed in detail.