Rotary pump evacuation

Exposure of the sample chamber to various ambients was controlled by use of a manometer system with evacuation obtained using a rotary pump. The lowest pressure obtainable using this system was 20 mtorr (base pressure of the rotary pump) with the highest pressure being 800 torr (maximum allowable on the manometer). 

Instead of rotary pumps, large water jet, steam ejector, or water ring pumps can be used. For batch evacuation, and the production of hydrocarbon-free fore vacuum for sputter-ion pumps, adsorption pumps (see Section 2.1.8.1) are suitable. If the use of oil-sealed rotary vane pumps cannot be avoided, basically two-stage rotary vane pumps should be used. The small amount of oil vapor that backstreams out of the Inlet ports of these pumps can be almost completely removed by a sorption trap (see Section 2.1.4) Inserted In the pumping line. 

Backing a rotary vane pump with a Cole pump (evacuating the oil box of the rotary vane pump) provides a combination which can achieve the high ultimate vacuum of a rotary vane pump combined with the vapour handling capability of a Cole pump. 

Fig. 9.4.8 Apparatus for the gas flow-cold trap method. One of the gas inlets is abbreviated in the figure. A cover in the figure is used to improve a collection yield. Without this, the particles produced just above a crucible are drifting in the chamber to deposit on the chamber wall. The end of the gas line is evacuated by a rotary pump so as to constantly flow the carrier gas. A solvent feeder is inserted on the gas line for the sublimation of organic liquid to deposit at the trapping apparatus cooled with liquid nitrogen. (From Ref. 10.)...

A three-stage differentially-pumped vacuum system, consisting of a molecular-beam stage between ion-sampling aperture and a skimmer, evacuated by a rotary pump, an ion optics region, and a mass analyser region, both evacuated by turbomolecular pumps. This design is most frequently used today. 

At this point, the flask is evacuated via the manifold (water aspirator) and a further quantity of acetic acid is distilled. Finally, the pressure is further reduced using a rotary pump to give a vacuum of ca. 1 mm Hg and a further quantity of acetic acid is removed, and heating is allowed to continue for about 30 min at this pressure. ... 

Pump and Purge. A key objective of cannula techniques is to achieve very low partial pressures of oxygen without the use of time consuming high vacuum techniques, and this is achieved by repeated pump and purge cycles. Even a heavily used rotary pump will give an ultimate vacuum of 1 x 10 2 mm Hg, and will rapidly reduce the pressure in a small reaction vessel to 1 m Hg. In a typical example a 224 mL reaction vessel contains approximately 2 mmol of O2, and evacuation to 1 mm Hg reduces the quantity of 02 to 2 x 10 3 mmol. If the vessel is refilled and the cycle repeated the quantity of O2 reduces to 2 x 10 mmol, and it is clear that relatively poor vacuums are sufficient to provide very low effective partial pressures of O2 after 2 or 3 pump/purge cycles. 

M(BH4) (M = Zr, Hf and Al ) with a significant vapor pressure at temperatures below which the product thermally decomposes, can be purified by considering the vapor pressure and temperature. The vapor pressures of Zr(BH4)4, Hf(BH4)4 and A1(BH4)3 are shown in Table 15.3. For example, pure Zr(BH4)4 was isolated from the products of reaction (15.6), i.e. mixture of Zr(BH4)4 and 4LiCl, because Zr(BH4)4 sublimed whereas 4LiCl remained in the container by evacuation using a rotary pump (under approximately... 

A typical ultrahigh vacuum system incorporating these features is shown in Fig. 72. The system is evacuated by a three stage mercury diffusion pump, backed up by a rotary pump. This is attached to the glass tubing through flexible stainless steel bellows. To minimize the... 

All the mechanical part of the balance, with the beam, set of weights, beam position sensor and compensation electromagnet, is enclosed in a thick-walled metallic chamber, which allows evacuation of the balance and beam cavity (of total volume of about 40 L) to a pressure of 4 x 10 bar with a mechanical rotary pump and to 4 x 10 bar with an additional diffusion pump. The evacuation can be performed either before starting the heating or during the course of the measurements. The gas distribution system allows the furnace space to be filled with various gases. Both static and dynamic atmospheres can be provided in the furnace, and two gases can be introduced in a preset ratio. 

The insulation space was evacuated with a 4-in. oil diffusion pump model NRC-0121 and reinforced with an NRC-6S rotary pump. Pumping speed was sufficient to permit full evacuation to less than 10 Hg within an 8-hr period with the assumption of a vacuum-tight system. 

Figure 2 shows the apparatus used for the plasma treatment of nylon 6. The pressure was adjusted to 5.3 Pa (0.04 torr) by evacuating using both a rotary pump and an oil diffusion pump with flowing oxygen gas. Other conditions were the same as for the apparatus above. The contact angle measurements confirmed that these two methods gave almost the same plasma treatment effect. 

Rotary pump for low vacuum Rotary pump for basic instruments s evacuation system Foreline trap Electromagnetic valve Electromagnetic valve Ionized gas molecule 0 Gas molecules which have absorbed electrons charged on specimen... 

Introduction of the Si specimens into a vacuum chamber should be done carefully. When the specimen is in the atmosphere, H Si(lll) and organic-modified Si are not positively contaminated within a short period. The largest chance of contamination is when the surface is in the stage of initial vacuum pumping. The residual gas in the vacuum generated by oil rotary pump is water and oil, and the latter causes severe hydrocarbon contamination. It is necessary to use an oil-free pump, such as liquid-nitrogen cooled sorption pump or helium cooled cryopump, for evacuation from atmospheric pressure. After quick, clean evacuation from the atmospheric pressure to Torr, the... 

---