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Chamber pressure

About: Chamber pressure is a research topic. Over the lifetime, 2988 publications have been published within this topic receiving 30725 citations.


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Journal ArticleDOI
TL;DR: In this article, various methods for moving charged particles in RF processing plasmas are investigated, such as varying RF power, varying chamber pressure, attraction and repulsion by an electrostatic probe, and movement with magnetic fields.
Abstract: Methods for moving charged particles in RF processing plasmas are investigated. These methods include varying RF power, varying chamber pressure, attraction and repulsion by an electrostatic probe, and movement with magnetic fields. Varying RF power changes the depth of the potential wells where particles are trapped. The RF power affects shape and location of the traps and the bulk plasma potential. Increasing the chamber pressure moves the sheath edge closer to the wafer being processed. Since particle traps are found at the plasma sheath edge increasing the chamber pressure will move the particle traps (and any trapped particles) closer to the wafer being processed. The Langmuir probe can repel particles when under negative bias and attract them when positively biased. This probe can also distort the sheath edge when the tip resides within the sheath. Applying a magnetic field can change the characteristics of the particle traps and produce a force on the charged dust particles. >

16 citations

Journal ArticleDOI
Ralph Harris1
TL;DR: In this article, an expression for the melt phase mass transport rate coefficient is developed from Machlin's model, which is used to examine rate control in previous small scale studies and in the present and previous pilot scale studies.
Abstract: Experiments were carried out on 35 kg melts of doped cathode copper and anode copper in a 3 m3, 150 kW vacuum induction furnace. Rates of removal of bismuth, arsenic, and antimony were measured over temperature and pressure ranges of 1450 to 1610 K and 3 to 30 pascals, respectively. Bismuth removal was found to be rapid: 1 to 18 x 10-5 m/s. Arsenic and antimony removal were quite slow: 0.2 to 3 x 10-5 and 0.1 x 10-5 m/s, respectively, and evaporation controlled rates of refining. It is shown that, at typical concentrations of these elements in copper, monatomic evaporation is the predominant evaporation mechanism. An expression for the melt phase mass transport rate coefficient is developed from Machlin’s model. In this expression, melt diffusion is a function of melt temperature, and melt surface velocity is a function of the square root of melt surface area to volume ratio and the square of melt temperature, i.e.: it = 1.11 x 10-7[(A/V)/]1/4Tr1/2 exp(-2515/T). This coefficient is used to examine rate control in previous small scale studies and in the present and previous pilot scale studies. The gas phase mass transport coefficient is found to be proportional to the overpressure ratio defined as: total initial melt vapor pressure/chamber pressure, and is also found to be dependent on the geometry of the gas space immediately above the melt.

16 citations

Proceedings ArticleDOI
30 Jul 2012
TL;DR: In this paper, film cooling as a thermal protection for the walls of liquid rocket engines is studied numerically for hydrogen and methane thrust chamber tests, and the results show that the present approach gives good results in terms of heat flux characterization, in particular when dealing with test cases of high chamber pressure.
Abstract: Film cooling as a thermal protection for the walls of liquid rocket engines is studied numerically for hydrogen and methane thrust chamber tests. The aim is to verify the capability of the Reynolds Average Navier-Stokes model to capture the basic characteristics of film-cooled thrust chambers, considering a simplified approach, named pseudo-injector approach, which does not model propellant injection and combustion. This assumption allows a great saving in computational time, in particular when considering 3D simulations. The present study takes its origin from the European Community In-Space Propulsion 1 (ISP-1) program where, among various projects, an experimental campaign has been designed to study the film cooling technique in an oxygen/methane thrust chamber and to provide a database for computational fluid dynamics validation. The results show that the present approach gives good results in terms of heat flux characterization, in particular when dealing with test cases of high chamber pressure.

16 citations

Journal ArticleDOI
TL;DR: In this paper, the effect of permanent magnets on thruster performance (specific impulse and thrust efficiency) and plasma-accelerating mechanism were examined through measurements of thrust, chamber pressure, current densities, and plasma properties in the exhaust plume.
Abstract: A steady-state 10-kW -range magnetoplasmadynamic (MPD) thruster with permanent magnets has been made. The effect of the permanent magnets on thruster performance (specific impulse and thrust efficiency) and plasma-accelerating mechanism were examined through measurements of thrust, chamber pressure, current densities, and plasma properties in the exhaust plume. Nomenclature At = cross-sectional area of nozzle throat Cf = thrust coefficient g = gravitational constant Id = discharge current /sp = specific impulse J = current per unit axial length m = propellant mass flow rate N = plasma number density Pa = ambient pressure Pc = arc chamber pressure T = thrust Ta = aerodynamic force Te = electron temperature Tm = electromagnetic force related to applied magnetic field Ts = self-magnetic force Vd = discharge voltage Vs = space potential Z = distance from throat center 77 = thrust efficiency

16 citations

Journal ArticleDOI
TL;DR: In this article, an experimental investigation was conducted to study the dual-bell transition behavior inside a high-altitude test facility under different back pressure environments, and it was observed that the transition was delayed by an increase in the width of inflection region with decrease in Reynolds number.
Abstract: An experimental investigation was conducted to study the dual-bell transition behavior inside a high-altitude test facility under different back pressure environments. The high-altitude chamber was evacuated using an ejector nozzle and the dual-bell nozzle driving pressure, P 0N, was varied from 30 to 5.3 bar in subsequent test campaigns. As P0N was decreased, the dual-bell transition was observed to get delayed, and the transition nozzle pressure ratio increased by as much as 20% for the lowest driving pressure tested. Similar results were also observed for the dual bell retransition nozzle pressure ratio. For very low values of P0N (of 3.5 bar), transition did not occur at all. The delay in the dual-bell transition process to higher nozzle pressure ratio is primarily attributed to the increase in the width of inflection region with decrease in Reynolds number, which seems to control the dual-bell transition behavior. During these tests, it was also observed that the visible intensity of condensation shock decreased gradually with decreasing P0N and finally, for P0N � 17:4 bar, no condensation shock was observed. The decrease in gas density/reduced mass flow is also accompanied by a significant decrease in the amplitude of wall pressure fluctuations in the region of separation due to decrease in shock strength.

16 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202322
202257
202167
202086
201991
201882