Diffusion pumps metal pump

The metal is widely used in laboratory work for making thermometers, barometers, diffusion pumps, and many other instruments. It is used in making mercury-vapor lamps and advertising... 

After leaving our samples in contact with C02 for about 16 hr, we found that the bands below 1950 cm-1 had increased in intensity, while the band at 2030 cm-1 had remained essentially constant. Obviously, some of the CO had migrated to other parts of the surface, while, in addition, some of the oxygen may have migrated, or even diffused into the bulk of the metal, whereupon some further chemisorption has taken place on the Bs sites, which have thus become vacated. When the C02 is frozen out by cooling part of the cell to the temperature of liquid nitrogen, no changes in the spectra are observed. Evacuation of the cell with a diffusion pump for a... 

With metal gaskets and moderate bakeout, turbo pumps can reach pressure below 10-9 torr without traps. They can be started at a pressure up to 1 torr. The time required to reach full pumping speed ( lmin) is much shorter than for diffusion pumps. Also these pumps must be backed by a primary pump. 

A cold cap baffle is constructed so that it can be mounted immediately above the high vacuum nozzle. The cold cap baffle is made of metal of high thermal conductivity in good thermal contact with the cooled pump wall, so that in practice it is maintained at the cooling-water temperature or, vi/ith aircooled diffusion pumps, at ambient temperature. In larger types of pumps, the cold cap baffle is water cooled and permanently attached to the pump body. The effective pumping speed of a diffusion pump is reduced by about 10 % on installation of the cold cap baffle, buf the oil backsfreaming is reduced by about 90 to 95 %. 

Substances are present in the vacuum vessel which have a higher vapor pressure than the driving medium being used among these are, for example, mercury, which is particularly hazardous because the mercury vapors will form amalgams with the nonferrous metals in the oil diffusion pump and thus make it impossible to achieve perfect vacuums. 

Fig. 4. Schematic vacuum system for metal atom reactions. X represents the stopcock or Teflon-in-glass valve. Satisfactory components (for a general discussion of vacuum line design see References 1 and 4) forepump, 25 L/min free air capacity diffusion pump, 2 L/sec main trap is removable and measures about 300 mm deep main manifold has a diameter of about 25 mm, stopcock or valve in manifold should be at least 10 mm substrate container is removable container with 1-2 mm Teflon-in-glass needle valve connected to bottom of container. Connection between this needle valve and the reactor may be 1/8 in. od. Teflon tubing is used. Alternatively, the substrate may be added as shown in Fig. 3.

Fig. 6.4. Cross-section of a metal diffusion pump. The upper stage in this pump has a wide annular opening (A) which provides a good ultimate vacuum. The lower stage has a small annular opening (A ) so the pump will operate against a high fore pressure. (B) High-vacuum connection to the low-temperature trap and vacuum line. (C) Connection to rotary oil-sealed pump. This pump is cooled by means of water tubes (D). Air-cooled versions have fins in place of these tubes and a fan is installed to blow air over these fins. (E) Electrically heated oil reservoir.

A special cleaning procedure was developed which virtually eliminated the characteristic decomposition of dilute metal-ammonia solutions. The optical cell was evacuated with a diffusion pump for several hours, about 50 ml. of anhydrous ammonia condensed onto the walls of the apparatus, and this wash ammonia was forced into a waste flask containing sodium and cooled with dry-ice. The optical cell was rinsed a total of four times. Approximately 500 ml. of anhydrous ammonia was condensed into the cell, about 5 mg. of potassium was introduced into the cell with the winch assembly (Figure 3a), and the solution was allowed to remain in the cell for at least 48 hours. The metal-ammonia solution was then forced from the cell into the waste flask the cell was rinsed four times with anhydrous ammonia and evacuated before introducing ND8. 

An alloy of ZrV19Fe01 was manufactured from metal ingots of Zr, V and Fe in an Ar-arc melting furnace, and the alloy was crushed and screened between 12 to 32 mesh in an Ar globe box, because the alloy is flammable in air. The alloy particles of 5.012 kg were packed in a dual cylindrical vessel made of SUS-316. After evacuated by a diffusion pump at temperature of 600°C, the alloy bed is cooled or heated to a specified temperature of T0 by the outside electric furnace. After sufficient time, electricity input to furnace was stopped. At the same time, hydrogen was supplied under a constant flow rate dented by W. Temperature was measured in several positions in the bed, and it was found that the temperature was almost uniform in the bed. 

The reaction was studied in a laboratory assembled high-vacuum system (see Figures 9.8 and 9.9), consisting of two vacuum circuits, one for the evacuation of the evaporation chamber and the other for the evacuation of the gas introduction system [119,122,123], Figure 9.8 shows the fore pump, diffusion pumps, cold traps, ionization manometer, and the metal evaporation chamber [119]. The evaporation was carried out al / = 10 6 Torr, with the help of a thread helicoidal filament made of a wolfram (W) wire of 0.5mm diameter and 10cm length [119]. The whole vacuum system was coupled with a mass spectrometer, Hitachi RMU-6D, in order to follow the reaction kinetics [119,122,123] (see Figure 9.9). The procedures followed in order to study the reaction were as follows ... 

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