Vacuum news

coils housed in the lower end together with the focus coils not under vacuum. This eliminates coil leaking or outgassing prob- lems and makes cleaning much simpler. The gun casing is fabricated in a ferritic steel to provide a magnetic screen for the beam. Ten turn indicating potentiometers are fitted to X, Y and focus controls as standard while a digital timer giving a range from one to 99 seconds in 0.1 second increments is an optional extra.

Another accessory available with the Mark II is an X-Y table manupulator. Both its axes are powered by variable speed DC motors, running with low friction linear bearings. The longer axis is the welding axis, with a 3] in. stroke, at a variable speed between 10 in. per minute and 100 in. per minute. The 4 in. x 3 ~ in. work table has a datum ledge at the rear, parallel to this axis. The shorter axis (3 in.) is for indexing to the beam, the motor being geared for a slower speed range to give sensitivity of control when positioning. Wentgate Engineers Ltd, Circle number 34 on Reader Enquiry Service card

Satellite planetary deposition fixture A new fixture from Electrotech Associates is claimed to be the first ever to use three simultaneous rotations of the workholder to achieve unequalled performance in step coverage and deposition, in semiconductor substrate coating. In addition to the rota- tion and spin of the workholder planets around the evaporation source, each indi- vidual substrate slice rotates around its own centre; ensuring perfect uniformity of deposition---even over steps at random orientations. Typical deposition uniformi- ties are substantially better than 1 per cent between points on a substrate or between different slices in the same load. The satel- lite planet (see photo) has nine 2 in. slice holders, held in a single row between the rim of the planet and a central boss, and separated by a free running spider. Using the same principle as is used to rotate the planet, each slice holder is rotated by fric- tion acting at its points of contact with the planet rim and boss. Versions for 18 and 24 in. bell jars are available with respective capacities of 27 and 45 2 in. slices. 1½ in. slices can be specified as an alternative. Electroteeh Associates Circle number 35 on Reader Enquiry Service card

maintenance costs. The furnaces are fully automatic, with fast heat-up and cool-down. The new furnace systems include light- weight, high strength fixtures and a com- plete selection of work handling equipment. Other items in the range include general research furnaces, with temperature capaci- ties to 3,000°C, and furnaces with gas, water, and oil quenching facilities. Edwards High Vacuum Int Circle number 36 on Reader Enquiry Service card

control to dr 1 °C. These solid-state, digital setpoint controllers provide two modes of operation with adjustable band and reset. A deviation indicator is included. Models 4045 and 4046 are rated for inductive loads and current limit capability is included with the Model 4046. Varian Associates Circle number 37 on Reader Enquiry Service card

Varian Model 4044 current proportioning controllers

Current proportioning controllers available from Varian Vacuum Division A new line of current proportioning con- trollers specifically designed for use with high temperature furnaces is available from Varian Associates' Vacuum Division. The 4040 Series is compatible with Marshall Furnaces, and features current propor- tioning action for applications requiring

Industrial vacuum ovens Barlow-Whitney Ltd, of Bletchley, Bucks, have recently introduced a new range of Horizontal Vacuum Drying and Processing Ovens under reference E-VACO-HOC. These are for operating temperatures to 200°C and are particularly suitable for powder drying and similar applications when it is essential to remove all moisture

Vacuum furnaces A new comprehensive range of vacuum furnaces is now available in Britain and Europe through a manufacturing agree- ment between Edwards High Vacuum (Plant) and the Abar Corporat ion of the USA. The furnaces, which are now made in England by Edwards, are available in a variety of types and sizes for industrial heat treatment, brazing, and sintering applica- tions. Their special features include effi- cient hot zones of simple, rugged design ensuring minimum downtime and low Drying and processing oven Series E-Vaco-Hoc

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