High Vacuum Pump Research Articles

Pumping Effect of a Gas Discharge High-Vacuum Pump

SIX years ago Foster et al., of the California Radiation Laboratory, constructed a high-vacuum pump with high pumping speed (3,000–7,000 litres/sec.) based on the principle of transport of ions during a discharge in a magnetic field1. The limiting pressure reached was less than 1 × 10−6 mm. mercury and the residual gases were free of hydrocarbon vapour. This pump at first caused much interest, but was soon forgotten in favour of more economic pumps based on the pumping effect of evaporated titanium2.

The axial flow compressor as a high vacuum pump: H. Hablanian. NRC Equipment Corporation, Newton Highlands, Mass., U.S.A.

The axial flow compressor as a high vacuum pump: H. Hablanian. NRC Equipment Corporation, Newton Highlands, Mass., U.S.A.

A new construction of a high-vacuum high-speed ion pump

A new construction of a high-vacuum high-speed ion pump

Lubrication of Rotary High Vacuum Pumps

The first part of this article dealing with Degrees of Vacuum, Pump Design, Use of Cold Traps, etc., appeared in our October issue.

Lubrication of Rotary High Vacuum Pumps

Rotary high‐vacuum pumps are oil‐lubricated. The lubricating oil acts as a seal against atmospheric pressure, and to enable it to do this the pump is normally submerged, or virtually submerged, in the oil. In the course of operation of the pump, the oil inevitably becomes contaminated with substances extracted from the system under evacuation. This complicates the questions involved in selection of the oil and has given rise to a number of remarkable devices to limit the accretion of contaminants.

High vacuum pumping unit

High vacuum pumping unit

High-vacuum molecular pump

High-vacuum molecular pump

Improvements i.o.r.t. a high vacuum pumping device

Improvements i.o.r.t. a high vacuum pumping device

Improvements i.o.r.t. high vacuum pumping devices

Improvements i.o.r.t. high vacuum pumping devices

Design and Operation of Evapor-ion Pumps

A new type of high vacuum pump has been developed which makes possible the elimination of organic vapors and high vapor pressure materials from vacuum systems, without using coolant traps or baffles. This pump utilizes the gettering action of continuously evaporated titanium in conjunction with ion pumping. Some pumping speeds achieved are: 7000–8000 liters/sec at 3×10−6 mm of Hg for hydrogen, 6500–7500 liters/sec at 1.5×10−6 mm for nitrogen and oxygen, approximately 9 liters/sec at 4×10−6 mm for argon, and approximately 4 liters/sec at 3×10−5 mm for helium. The lowest pressure obtainable is about 2×10−7 mm of Hg. Dependence of pumping speeds on the temperature of the gettering surface, the pressure and the rate of evaporation of titanium is given.

Apparatus for Measuring Relative Blood Viscosity

A method for measuring blood viscosity which can be applied to small quantities of blood containing no anticoagulant, and which can be repeated at several minute intervals is described. The method utilized an old principle of measuring time of flow of a fixed quantity of blood (0.1 ml) through a fixed capillary tube (hypodermic needle with a bore approximating 0.3 mm), using a fixed negative pressure of 100 mm of mercury. The needle and pipette which come into contact with the blood are maintained at a temperature of 37°C±0.5°C. The blood is drawn into a 2-ml siliconed syringe through a size 20 siliconed intravenous needle. The calibrated capillary tube is then inserted through the tip of the syringe and negative pressure applied. The time of flow is measured with a stop clock to 0.1 second. Duplicate measurements on the same sample of blood can be made in less than 30 seconds. A high vacuum pump is included with the apparatus to clean and dry the needles and calibrated pipette immediately after each measurement. The relative viscosity of the blood is then computed by dividing the time for flow of 0.1 ml of blood by the time for flow of water at the same temperatures.

High vacuum pump

High vacuum pump

Cold traps for vacuum systems

709,819. High vacuum diffusion pumps. NATIONAL RESEARCH DEVELOPMENT CORPORATION. June 17, 1952 [July 18, 1951], No. 17061/51. Class 71. A cold trap located in a pipe 10 between a high vacuum pump of the oil or mercury diffusion type and a vessel to be evacuated comprises metal baffles 7 so shaped as to provide a tortuous flow of gas and vapour and mounted on a metal rod 1 having one end 2 located outside the pipe 10 and cooled by being dipped in liquid air. The baffles 7 comprise semicircular copper sheets welded at their curved edges to sheet metal spacing and supporting rings 8 and at their straight edges to copper spacing rods 9. The rod 1 is hermetically sealed at a joint 3 where it enters the pipe 10

Some measurements on a high-vacuum high-speed ion pump

Some measurements on a high-vacuum high-speed ion pump

Some measurements on a high-vacuum high-speed ion pump

Some measurements on a high-vacuum high-speed ion pump

Cut Costs...Boost Efficiency...with Stokes High Vacuum Pumps

Cut Costs...Boost Efficiency...with Stokes High Vacuum Pumps

Methods of Obtaining High Vacuum by Ionization. Construction of an ``Electronic Pump''

Calculations on the possibility of obtaining high vacuum in an electrical discharge are given. It is shown that in a simple dc gas discharge practically no real pumping action is possible; in such a discharge only clean-up, i.e., electrical adsorption, may be observed. A real pumping action only results if it is possible to get within a tube, such a high ion current by special arrangements that the number of ionized gas molecules transported with this current in one direction is greater than the number of gas molecules that will diffuse back in the opposite direction. An electronic high vacuum pump of real pumping action has been built; it starts pumping at about 10−3 mm Hg and gives an ultimate pressure lower than 5×10−6 mm Hg.

A Simple and Accurate Internal Standard Flame Photometer for the Determination of Sodium and Potassium in Biological Fluids

One of the authors (Leppänen) had previously developed a simple flame photometer with two photocells, based on the internal standard principle (V. Leppänen & O. Forsander, Flame-Photometric Determinations of Potassium and Sodium in Biological Fluids. — Scandinav. J. Clin. & Lab. Investigation 1951, 3, 33). Since, however, this apparatus was found to have some technical drawbacks in continuous use, two of the authors (Leppänen & Krusius) intended to use another simple type of flame photometer, with only one selenium photocell (flame photometer proposed by Riehni & Lange, Model 2, Dr. B. Lange, Berlin— Zehlendorf. See H. Riehm & B. Lange, Bestimmung von Kalium, Natrium, and Calcium im Flammenphotometer nach Riehm-Lange. — Ztschr. f. anal. Chem. 128, 1948). Experience with this photometer showed, however, that it was not suitable for clinical use. The authors, therefore, designed a new simple flame photometer in collaboration with a radiotechnical specialist (Mettinen). The new flame photometer is based on the internal standard principle and uses vacuum photocells (type Mullard 90 and CV 90). The apparatus operates by ordinary domestic coal gas, the light emission of which is rendered monochromatic by means of interference filters and measured by the photocells. The electric impulses are compensated against each other, and the difference between them is amplified by a special amplifier and measured by a sensitive galvanometer. A high vacuum pump acts as an air compressor and gives a satisfactory and steady pressure to the atomizer. There are special valves to regulate both air and fuel pressure. This relatively simple apparatus is suitable for the clinical determination of potassium and sodium in both plasma (sera) and erythrocytes, but it can also be used for the examination of other biological fluids. The accuracy of the apparatus is demonstrated by calibration curves for potassium and sodium standard solutions, by control determinations, and by analyses with known amounts.

An air-cooled high vacuum pump

An air-cooled high vacuum pump

Factors influencing the Interaction of insecticidal Mists and flying Insects

The considerations affecting the design of a spray testing chamber are discussed, and a description is given of equipment specially intended for use with mosquitos as the test insect. In essentials the apparatus consisted of a metal chamber surrounded by a “Masonite” cabinet with an air space in between. In this space air, at a constant temperature, was circulated around the outer face of the inner metal chamber and so controlled the temperature of the spray chamber. The cabinet was fitted with lights; wet and dry bulb thermometers to check the humidity, which was controlled by blowing in steam; a fan to circulate the air; a spray gun; four ports through which the insect exposure cages were introduced into the chamber; a shelf to carry these cages; and an exhaust and an intake port to allow the mist to be removed at the conclusion of the test. Finally, there was a door on one side allowing access to the interior. It will be noted that the insects were introduced into the spray chamber in cages and not allowed to fly freely. This greatly facilitated the collection of insects at the conclusion of the test. Under the routine testing conditions adopted the insects were not introduced until four minutes had elapsed after spraying. They were then exposed for ten minutes and afterwards transferred to clean recovery cages.The practice of caging the insects and placing them on a shelf opposite a window within the spray chamber permitted the insects to be closely observed and the rate of paralysis (knockdown) to be followed. In general, however, the rate of knockdown, when it occurs, was not so sensitive a method of comparing insecticidal efficiency as the twenty-four hour percentage kill.In practice the apparatus was found to give satisfactory results. It permitted accurate comparisons to be made between different strengths of a given insecticidal solution, but care had to be taken to ensure that the non-volatile content of the sprays being compared for toxicity was essentially similar. When this was not so, other things being equal, the spray which produced the less volatile mist (i.e., the larger particle size) gave the higher kill. When working on activators, which are usually non-volatile materials, it was therefore necessary to add an equivalent quantity of, say, high vacuum pump oil to the control spray before making the comparison. Examples of the application of the method of pyrethrum, DDT, and activated sprays are given.The set of standard conditions chosen for the routine testing procedure were sometimes rather arbitrarily fixed but usually with due reference to the requirements of the insects or to practical testing conditions. Since two of the conditions chosen, i.e., the use of caged insects and exposure after an interval of four minutes after spraying, were rather artificial from the point of view of practice and might conceivably have led to conclusions inapplicable to practical conditions, the effect of modifying certain of the standard procedures was investigated. The results of these experiments are fully described in the text. It was concluded that temperature influenced the level of kill recorded considerably, the kill being lower when the temperature of the spray chamber was dropped 10°C. Humidity seemed to have little or no effect within the range 40–80 per cent. R.H. Increasing the interval at which the insects were inserted after spraying from 0 to 10 minutes affected the level of kill without influencing the comparative efficiency of the insecticides examined. On the other hand caging the insects had a pronounced effect on the comparative efficiency of pyrethrin sprays with and without added non-volatile material. This was thought to be due to the delay in access of the spray droplets to the caged insects which permitted a sufficient interval for the differences in particle size to become established. With caged insects inserted before spraying, therefore, the biological efficiency of a pyrethrin spray without, added non-volatile material is much lower than when some such substance as high vacuum pump oil is added, whereas this difference is much smaller when the insects are exposed free in the cabinet (Table X).