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1.
J. Mentel 《Applied Physics A: Materials Science & Processing》1977,14(3):269-276
Arc roots at which marked vaporization occur are unstable and therefore in general non-stationary. High speed photography
of arc roots using various electrode materials in Ar, SF6, and N2 shows that the appearance of the arc roots results from the superposition of several phenomena. On graphite cathodes in Ar
it was possible to observe these phenomena separately by varying the cooling of the electrodes. It is shown that distinctions
must be drawn between the real current transfer region with relatively weak vaporization, vaporization from the electrode
surface outside this region and vaporization from within the body of the electrode. The energy-balance determined experimentally
confirms the theoretical prediction that the energy for strong vaporization of the cathode is supplied by an ioncurrent. 相似文献
2.
M. Grozeva M. Kocik J. Mentel J. Mizeraczyk T. Petrov P. Telbizov D. Teuner N. Sabotinov J. Schulze 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,8(2):277-286
Our investigations demonstrated that utilizing copper bromide (CuBr) mixture as a source of Cu atoms in a RF-excited discharge
can be a promising alternative to the Cu sputtered system, when the development of Cu ion gas laser is considered. Both spectroscopic
and laser investigations showed that the threshold input power for lasing was reduced about 5 times using the CuBr-based system
instead of the Cu-sputtered system. Pulsed and CW laser oscillation on Cu+ transitions in the near IR spectral region was obtained in RF-excited He-CuBr discharge operated at 13.56 MHz and 27.12 MHz.
At input RF power of 800 W, a laser output power of 10 mW at the 780.8 nm Cu ion laser line was achieved. An increase of laser
output power by a factor of two, as well as better Cu vapour axial distribution and better discharge stability, was attained
when DC discharge was superimposed on the RF discharge. Laser gain on 11 UV Cu ion lines was observed in RF-excited Ne-CuBr
discharge. basing on the obtained results, we consider the CuBr laser system excited by RF discharge capable of generating
UV laser radiation at relatively low input power.
Received 4 January 1999 相似文献
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4.
The onset current of the helical instability of wall stabilized arcs can be determined by a theoretical model from a dimensionless function which is only dependent on the power input and a factor containing the gas properties and the arc conductance. The model describes the onset current of the instability in hydrogen and nitrogen as function of the tube diameter and of the pressure. Questions of restabilization are discussed. 相似文献
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6.
The diffraction theory of image construction has been used, in the case of a differential interferometer employing a Wollaston
prism, to derive the position of the interference fringes in dependence upon the phase object and the prism position. This
procedure is not only more correct, but proves also to be simpler than the corresponding geometric-optical treatment. An example
is presented in which the fringe shift resulting from a symmetrical gas flow has been used to evaluate the gradient of the
optical path perpendicular to the rotational axis of symmetry.
相似文献
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8.
Schein J. Schumann M. Nandelstadt D. Mentel J. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1997,25(5):897-904
To investigate the ignition of arc spots on cold cathodes under defined conditions, a special experimental setup was developed. An arc ignited between horn electrodes in a pure argon gas atmosphere is blown magnetically against a third so called commutation electrode, which is negatively biased against the arc plasma. The ignition of arc spots on this cathode was investigated by electrical measurements and high-speed photography. The arc traces of short current pulses were examined by in situ optical microscopy of the cathode surface. Two different modes of arc-spot ignition were observed: an initiation by a diffuse glow discharge, which may pass into a constricted arc spot, and an immediate formation of a constricted arc spot. The two modes of arc-spot ignition at atmospheric pressure were attributed to different surface structures, which are characterized by broad or narrow distributions of local ion current density enhancement factors. Ion current density enhancement may raise the field strength and temperature on the tips of microprotrusions so far that they emit electrons. A sufficiently high density of small emission sites produces locally such a high average current density that a plasma channel and an arc spot on the cathode surface arc formed. With lower pressure, the influence of the surface structure is reduced and pushed back by Townsend-γ emission 相似文献
9.
Gas Phase Emitter Effect of Thulium within Ceramic Metal Halide Lamps in Dependence on Frequency 下载免费PDF全文
C. Ruhrmann M. Depta A. Bergner T. Höbing C. Denissen J. Suijker J. Mentel P. Awakowicz 《等离子体物理论文集》2014,54(2):215-224
The gas phase emitter effect within ceramic metal halide (CMH) lamps reduces the effective work function of the electrode material and, therewith, the electrode temperature. An investigation of the gas phase emitter effect of thulium (Tm) within CMH lamps seeded with Tm iodide (TmI3) is carried out. For this purpose, phase resolved images of the arc attachment and measurements of the electrode temperature, Tm atom and ion densities are performed in dependence on operating frequency by pyrometry and optical emission spectroscopy. Additionally, the influence of a sodium iodide (NaI) admixture is studied. The emitter effect is generated by means of a monolayer of Tm atoms on the electrode surface generated by a Tm ion current within the cathodic phase. It overlaps onto the anodic phase at higher frequencies of some hundreds of hertz. The reason is the finite life time of the monolayer, which is determined by the adsorption energy of Tm on the tungsten surface. Due to the low electric field strength in front of the anode and the mass inertia, the emitter ions and atoms remain in front of the anode. They retard the decay of the monolayer and with it the increase of the work function. Moreover, a comparison of a lamp seeded with TmI3 and sodium iodide (NaI) with a lamp seeded only with TmI3 illustrates a slight reduction of the electrode tip temperature caused by a higher Tm saturation vapour pressure and a higher Tm amount within the lamp filling. The influence of Na appears to be quite low. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
10.
J. Mentel 《Applied Physics A: Materials Science & Processing》1977,14(4):361-366
The root of an argon are was stabilized by strong cooling of the graphite cathode; both the composition and the temperature
of the plasma at the arc root were determined spectroscopically. The measurements of the absolute intensities of two CI and
two CII lines revealed that the plasma is composed almost entirely of atomic carbon. Immediately in front of the cathode a
temperature of 12000 K was measured and the degree to which the gas was ionized was found to be 30%. The velocity of the plasma
was 300 m/s.
This work is based upon material presented in the final report “Basic research programme for plasma technology, high-pressure
arcs in SF6” to the Federal Department of Research and Technology, Fed. Rep. Germany. 相似文献