High flux beam source of thermal rare-gas metastable atoms

Corona discharge supersonic free-jet for III–V nitride growth via A 3Σu+ metastable nitrogen molecules

“…18 The technique was subsequently developed by Leasure et al 19 and by Fahey and coworkers. 20,21 The latter reported beam intensities of 3.5 ϫ10 14 , 1.5ϫ10 14 , and 7.2ϫ10 13 metastables sr Ϫ1 s Ϫ1 with helium, neon, and argon, respectively. CDSFJ expansions have been used extensively to produce cold radicals for spectroscopic analysis 22,16,23,24 and such work has included nitrogen.…”

“…1, was similar to those described in the literature. [18][19][20][21][22][23] It consisted of a quartz tube ͑6 mm o.d., 4 mm i.d.͒, heated and drawn to closure then ground back to form a nozzle orifice diameter of 200 m as measured by an optical comparator. The nozzle tube was mounted in a 1/4 in.…”

Generation of energetic He atom beams by a pulsed positive corona discharge

“…Within this time the voltage dropped at least 40% of the maximum value. The discharge voltage then remained at this low level for [10][11][12][13][14][15][16][17][18][19][20] s, before slowly rising back to the initial voltage. Measurements of the voltage divider signal indicated that despite the high source voltage ͑defined as the voltage at the power supply͒ in the range from 1 to 4.8 kV, the actual potential across the needle ranged approximately from 300 to 450 V. The average current through the source increased with the source voltage, and was in the range from 15 to 85 A.…”

“…Thus, we attribute the slow peak to metastable atoms that are emitted from a plasma with thermalized neutral gas background, in agreement with the metastables observed by others. 7,8,[10][11][12] If we assume an isentropic expansion, then we find that the metastable atoms are produced from expansion of a gas with a stagnation temperature of 131 K. Thus, the plasma 30-50 s after initial breakdown has a neutral background temperature approximately double that of the cell walls. Plasma effects could also explain the high velocity tail of the distribution, which exceeds that expected for a supersonic distribution, since collisions with more energetic charged particles would lead to excess population in high translational energies.…”

“…Curiously, no paper reported photons, fast atoms, and thermal metastables simultaneously. Several papers 7,8,[10][11][12] have described thermal metastable beams from corona discharge sources, both pulsed and continuous. These authors arrived at a similar conclusion for the mechanism of metastable atom beam generation, i.e., supersonic expansion from a high pressure plasma.…”