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Vacuum Gauges and Gas Analyzers
Published in Marsbed H. Hablanian, High-Vacuum Technology, 2017
Figure 12.17 shows a bell-jar vacuum system with a typical arrangement of pumps, valve, and gauges. The expected deviation between gauges 1 and 2 should be near a factor of 2 because of some conductance limitations along the flow path between the chamber and the underside of the valve. However, under transient conditions, during evacuation, the upper gauge may read 10 or 100 times higher pressure after the valve is opened. This is because the gauge has been exposed to atmosphere and has excessive quantities of gas on its surfaces, subsurface pores, and oxide layers. A period of time (few minutes to a few hours, depending on the pressure level) and degassing of the gauge are required before the expected factor of 2 or 3 ratio between the two gauges is established.
Overview of Nanometer CMOS Technology
Published in Frank Schwierz, Hei Wong, Juin J Liou, Nanometer CMOS, 2010
Frank Schwierz, Hei Wong, Juin J Liou
Metal films for contacts and interconnects are usually deposited using vacuum evaporation or sputtering techniques. For vacuum evaporation, the wafer is placed in a vacuum bell-jar. The metal to be deposited is put in a tungsten or molybdenum boat, and the metal is vaporized by either heating the boat or electron bombardment. The metal atoms are then emitted from its surface and condensed on wafer surface. Because of the poor coverage, this technique is no longer used in the submicron era. The metal films are now often deposited using the sputtering technique, where an inert gas (argon) is blown into the bell-jar, and the chamber is kept under a pressure of 10−2 Torr. Unlike the vacuum evaporation, the metal to be deposited acts as the cathode in the sputtering system. A high voltage source (several kV) is applied to ionize the containing gas. Positive ions are then accelerated and bombard the surface of the cathode, thereby causing the ejection of metal atoms. The ejected atoms travel in all directions and coat the surface of the wafer uniformly.
Thin Films: An Overview
Published in Rajesh Singh Tomar, Anurag Jyoti, Shuchi Kaushik, Nanobiotechnology, 2020
With the deposition over, the filament and heater currents were switched off. Valve V3 was closed, and the fine vacuum Penning gauge was switched off. After 10 minutes, the air admittance valve V4 was opened to leak air into the vacuum chamber, making the bell jar free to be removed, and the electrodes deposited film to be taken out. The coating unit was closed down by first turning off the diffusion pump heater with the rotary pump still running and the backing valve open. After 15 minutes, when the boiler of the diffusion pump was cooled, the backing valve was closed, and the rotary pump was switched off. Finally, water circulation in the diffusion pump was stopped [31–40].
Total Hemispherical Emissivity of Potential Structural Materials for Very High Temperature Reactor Systems: Alloy 617
Published in Nuclear Technology, 2019
Kyle L. Walton, Raymond K. Maynard, Tushar K. Ghosh, Robert V. Tompson, Dabir S. Viswanath, Sudarshan K. Loyalka
where =surface area of test section =emissivity of test section =surface area of bell jar interior =emissivity of bell jar interior.
Colorimetric determination of mercury vapor using smartphone camera-based imaging
Published in Instrumentation Science & Technology, 2018
Alan Rodelle M. Salcedo, Fortunato B. Sevilla
Gas mixtures with different concentrations of Hg0 were prepared using the “bell jar” method.[20,23] A small volume (ca. 1 mL) of elemental Hg was placed in a glass vial sealed with a silicone septum. A saturated mass concentration of Hg0 was developed in the air inside the vial after 24 hr. At a working temperature of 26 to 27°C, the mass concentration of saturated mercury in air inside the vial is approximately 21–24 mg/m3.[23] Different volumes of this Hg0-saturated air were withdrawn using a syringe to obtain specific concentrations of Hg0.
Microwave reduction of Black Thor chromite ore
Published in Canadian Metallurgical Quarterly, 2018
The chromite ore was mixed with predetermined amounts of activated charcoal. Based on a fixed carbon content in the activated charcoal of 86.3%, as given in the proximate analysis in Table 2, the amount of charcoal added is represented as a carbon addition. Samples for the bulk of the experiments were prepared with a 15% carbon addition (control amount) and were mixed in 2 kg plastic containers by roll mixing until the sample was homogeneous throughout. For the other tests with different charcoal additions, the samples were mechanically mixed. The mixed samples were dehydrated in a drying oven for 24 h prior to testing. For microwave testing, 30 g of the mixed powder was poured into a quartz crucible. The cylindrical crucible had an inner diameter of 25 mm with 3 mm thick walls. Quartz was selected due to its high melting point, lack of reactivity with the sample, and microwave transparency. The crucible, containing the sample, was then be placed on a heat resistant and microwave transparent platform base comprised of SALI™ (20% SiO2, 80% Al2O3). For tests done in air, the loaded crucible and platform were placed in the microwave applicator. For the tests done in argon, the crucible and platform were placed in a glass bell jar with a Teflon base as shown in Figure 2. In order to ensure that the samples in air and argon were at the same relative height, and thus position in the applicator, the tests done in air had a taller SALI™ base to compensate for the Teflon base used in argon testing. The Teflon base featured a gas inlet attached to a polypropylene connector, which was then attached to an argon gas line. A gas outlet valve was also present on the glass bell jar.