Vacuum news

Another feature of the new high-vacuum gate valve, claimed to be unique, is the rotary shaft seal which is incorporated in all three models. Upon visual inspection it can thus be determined whether the valve is open or closed.

An optional aid is the use of a roughing port which permits mechanical pumping through the system during periods when the valve remains closed, i.e. during system pump-down. This feature allows the oil diffusion to continue operating without long delays for cooling and for starting up.

All valves are tested for at least 60,000 cycles. Internal rollers are used in the Cenco gate valve to eliminate friction and the use of large amounts of lubricants. All moving parts and the valve operator can be removed with the valve remaining vacuum-tight while in the line. This is a great advantage since the vital moving parts can be removed, cleaned or repaired or even exchanged for a different actuator, with a minimum of “down” time. Cenco Instrumenten hfij NV, The NetherIands Circle number 52 on Reader Enquiry Service card

Large port v&e testing Test-stand proven, Vacuum Research Company’s new large port valves are now available in 2-inch (39, 4-inch (5#), and 6-inch (S) sizes. These valves are made of permanent mould altiium castings in straight-through style, with Buna N or Viton seals. On the test stand, these valves were vacuum cycled over 50,000 times without failure.

Vacuum Research Company’s new port valve

Minimum seal maintenance guarantees 50,000 cycle operation and up to 100,000 cycles of operation. In normal, clean vacuum service this is the equivalent of 50+ years. Incorporating many new valve features these valves are said to assure customer satisfaction. Vacuum Research Company, California, USA Circle number 53 on Reader Enquiry Service card

New system for adding TGA capabiity to DTA instruments Existing differential thermal analysis (DTA) instruments can be up- graded to do thermogravimetry (TGA) more simply than ever before, under a new method announced by Cahn Instrument Company.

Cahn recording vacuum electrobalances are said to be widely used in commercial and custom TGA systems. Previous practice in adding TGA capability to DTA systems has been to provide a separate furnace for TGA, which might require a different programmer. This change would then propagate on through the system, making the TGA version substantially different from the original DTA, and correspondingly more expensive. The new system permits use of the original DTA furnace, and therefore all other parts of the original DTA. Costs other than the balance are eliminated.

Since the new method uses the original DTA system, installation is simplified drastically, to the point where the user can do it himself. Operation is also easier, and the data is more compatible with DTA data.

To develop this method, a survey was made of all 13 commercial DTA instruments produced throughout the world. Of these, two had unorthodox furnaces which did not lend themselves to TGA, and the remaining 11 could all use a sample hangdown tube of 30 mm diameter. A line of such sample tubes is now produced by Cahn, in both Pyrex and Vycor, and in both flow-through and closed-end versions. In addition, a technique has been developed by Cahn to use all kinds of differential temperature recorders with their recording balances.

The resulting TGA accessory for DTA instruments can weigh

samples from 2.5 g down to 50 pg, in vacuum, reactive atmospheres or room air, at temperatures up to 12OO”C, at less than one-half the price of previous systems. Cahn Instrumeat Company, Cai&omia, USA Circle number 54 on Reader Enquiry Service card

Vacuum micro-sublimator apparatus This new device from Rahl Scientific Instrument Corporation is a compact instrument with a long temperature gradient to pennit micro-sublimation of samples in a horizontal tube, while under vacuum.

Separations are useful not only for rapid identification, but a plastic liner permits retrieval of the isolated components for spot tests, further charomatographic procedures or other analytical pro- cedures where it is advantageous to have pre-puritication of the sample, etc. This process has sometimes been called “sublimato- graphy”.

Vacuum micro-sublimator apparatus

The sample, placed in a carrier at the sealed end of a glass tube, is inserted into the zone of maximum heat of a coil logarithmically wound around one of the quartz tubes; the other end of the glass tube is connected to any vacuum source. The electrical current for the heater is adjustable to allow a wide sublimation range. The visible deposition of the material on to the plastic liner from its vapour state permits qualitative analysis as well as quantitative evaluations in a few minutes, even while the sample is being pro- cessed. Applications include analytical, bio- and organic chemistry as well as forensic medicine. KahlScientifc Instrument Corporation, California, USA Circle number 55 on Reader Enquiry Service card

Interference objectives The availability of 8 and 16 mm interference objectives, each with a built in interferometer for the examination of surface by reflected lights, has been announced by W Watson & Company Limited. The objectives are said to produce bold interference fringes on a wide range of surfaces by monochromatic or white light. The orienta- tion and spacing of the interference fringes can be adjusted to suit any particular measurement without disturbing the specimen.

The objectives are said to be suitable for measuring thicknesses above 300 A of vacuum deposited dielectric tihns, the thickness of thin metal films, and many measurements in connection with semiconductors. W Watson & Sons Lindted, UK Circle number 56 on Reader Enquiry Service card

Portable electrometer A compact, inexpensive electrometer is now available from Nuclide Corporation. This portable unit, Model EA-7, is said to rapidly detect and measure ion currents in the 1O-6 to 10-l’ amp regions. The EA-7, which is supplied either battery or line operated, is parti- cularly useful in studies involving mass spectroscopy, the Franck- Hertz measurement of excitation potentials, the photoelectric effect, or any experiment in which the rapid determination of currents is needed.

Vacuum news

Nuclide portable electrometer, Model EA-7

An outstanding feature of the EA-7 electrometer is its fast rise- time. The output voltage, which is linear over its full range, rises to 90 per cent of its Gnal value 0.2 se-c after a step input current signal in the 10-r” amp range is applied. Also, the unit has a built-in range changer that permits switching between six separate ranges (1O--5, lO_“, 10-r, lO_*, 10-O, lO-‘O amp, full scale). The unit also has a built-in calibrate and zero switch. Nuclide Corporation, Massachusetts, USA Circle number 57 on Reader Enquiry Service card

Universal vacuum manifold A universal glass vacuum manifold offering researchers a compact high-vacuum work station, providing as many as six take-off points, each of which can be independently controlled from only one vacuum pump and capable of maintaining pressures in the range of WB torr, is now available from Aremco Products Incorporated.

The new Aremco MANO-VAC consists of an inlet port to the vacuum pumping source, a cold trap and six take-off points. All six stations can be used as high-vacuum take-off points . . . or four stations can be used in combination with a McLeod gauge and manometer.

Aremco universal glass vacuum manifold

staadnrdgaskets A new series of gaskets manufactured by Vacuum Research Company to save dollars in vacuum piping systems, both in assembly time and elimination of “0”-ring grooves, have been announced. The gaskets are a permanent mould altiium casting with Buna N seals bonded to them in sixes for 2, 3, 4, 6, 8 and lO-inch 150 lb flanges. The

A selection of new gaskets from the Vacuum Research Company

gaskets are held in place by two bolts in the flange through ears which are in the castings. The double seal allows the provision for a guard vacuum between the seals. An aluminhun ridge on the casting assures exact vacuum compression of the seals by preventing over- torquing of the mating flanges. Vacuum Research Company, Cal~ornia, USA Circle number 59 on Reader Enquiry Service card

Sexless flanges and gold-wire seals Mullard Limited have announced the availability of standard gold- wire “0”-rings, seals and flanges. These are designated the VMF series and are available in 18, 25, 38, 51, 75 and lOO-mm sires. The flanges are, of course, sexless and the gold wire “O”-ring is fused

Mullard standard gold-wire seals and flanges

The MANO-VAC universal glass vacuum manifold can be used for a variety of high-vacuum research work such as vacuum distil- lations, gas transfer experiments, and high-vacuum purification. Aremco Pro&& Incorporated, NY, USA CircIe number 58 on Reader Enquiry Service card

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into the stainless steel spider, which in addition to ensuring perfect location, is said to make for easy assembly. It also acts as a shim so that correct tightening of the flanges is ensured. Mulhzrd Limited, UK Circle number 60 on Reader Enquiry Service card