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LT terminals for resistive evaporation. A further 4 positions are blanked off. All these positions are capable of taking size ‘A’ leadthrough, including multi-leadthroughs and rotary drives. In addition 4 holes are provided size ‘B’, for low current or tight duty rotary drives. Access to the lead- throughs is obtained by removing the shroud surrounding the elevated baseplate. A filament holder is provided comprising a common earth bar and 4 separate filament clamp assemblies from the relevant LT leadthroughs. The ion clean-up rings are available as a simple bolt-on accessory, as arc a comprehensive range of additional jigs and fixiures.

Th’: LT sutmly in both units is distri- buted to the r&v&t evaporation source by a 4-position suitch on the front panel. A pressure switch fitted to the high vacuum side ensures isolation of the auxiliary ser- vices M hen the system is at atmosphere. Instruments are provided to read rough and fine side pressures. The unit is supplied equipped for evaporating from 4 positions using spirals, baskets or boat sources, sample selection of which is supplied. When it is required to evaporate carbon on to a substrate, ie microscope slides, this is ~tsually carried out by short duration carbon arc. To achieve a satisfactory arc a 30 V. 30 amp supply is used. A pulse circuit is fitted on the EC. I2,‘4/3 so that the carbon may be evaporated in bursts for close thickness control. Both carbon and metal or di- electric films may be deposited in quick succession if required. A water outlet is provided at the top rear of the coating unit console for connection to the EBU.2 Electron Gun if this is in use. Earthing studs are also provided on the unit for earthing the electrode collar to the console and the console to the electron power unit. Liquid nitrogen filling is achieved through a Filler cap located in the work surface.

Optional accessories available include: a carbon coating assembly; a six-source turret assembly: high voltage sputtering rectifier; electron beam evaporation unit: ion clean-up assembly: quartz crystal mass and rate monitor: rotary shaft drives: and a vacuum feedthrough col!ar. General Engineering Co (Radcliffe) Ltd. UK Circle tttrtt~hrr 45 077 Rradcr Ettytriry Serviw cut-(/

Edwards UHV pumping unit Edwards High Vacuum Limited have intro- ducedaneu ultrahighvacuumpumpingunit. based on a sputter-ion/sublimation pump combination, intended for use on organic- free coating units or other types of clean investigational process chamber. Ultimate pressures better than IO-” torr are reached when operating in a clean 14-inch diameter, stainless steel chamber. The pumping group is directly connected to the chamber by a wire-sealed flange. The four-electrode sputter-ion pump comprises diode assem- blies in vacuum brazed stainless steel, giving extreme cleanliness in the freshly prepared pump. Performance is given for a 14-inch chamber but equivalent 4-lobe

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electrode systems are available for any chamber size. An unusual feature of the built-in sublimation unit is that the subli- mation source deposits titanium on a re- movable internal substrate which may be cooled either by M’ater or liquid nitrogen. With liquid nitrogen cooling, as well as affording a cryopumping action on con- densible gases, the structure of the titanium film formed is favourably altered to give increased pumping activity.

The system is bakeable to 350 C fo7 complete degassing and bakeable magnets allo\\ operation of the pump during bake- out. Ovens for the pumping group and pro- cess chamber may be operated separatcty so that, for example, the chamber may be baked toahighertempcrature than the pump unit. A forced fan-cooling system allows rapid cooling after bake-out. Rough pump-

ing may be either by three EZ 500 sorb pumps or by a two stage rotary pump with foreline trap. The sorption pumps are a recent development using an activated alumina absorbent which provides excep- tional freedom from hydrocarbon con- tamination wjith the facility for regeneration of the charge remote from the system. Power supplies for the unit, together with the main controls and instrumentation arc housed in a control console. As an optional accessory, a liquid helium cooled cryopump (E 1000) may be fitted in the interior of the process chamber, pumping nitrogen at 1000 Iitresisec or uater vapour at 10.000 litres:‘scc. Edwards High Vacuum Ltd, UK Circle ttrtttthrr 46 017 Rcaclc~r~ Ettqttir,v Scr riw iWd

High vacuum systems Mason-Renshaw Industries. of California, USA, have introduced a line of complete systems for general high vacuum labora- tory applications. These systems are specifi- cally aimed at economy of price for high performance. The basic system consists of a two-stage I .25 cfm (35 litres/min) mechan- ical pumps, a I50 litre/sec oil diffusion pump using DC-305 oil, an anti-migration stainless steel liquid nitrogen cold trap and a complete high vacuum foreline- and roughing valving manifold with Flexoand stainless-steel tubing. The mechanical pump features a patented oil recirculation device yielding ultimate pressures better than 5 10 J torr without gas ballast. The diffusion pump fabrication is completely vacuum brazed eliminating all weld crevice prob- lems and flange distortions. An advanced fractionating system and easily demount- able one-piece heater result in low back- streaming rates and ultimate pressures of about 10~” torr. In the valving manifold, fabricated in one cast aluminium, heat treated body, the roughing and foreline valves are bellows-sealed with rollers on the gate and carriage mechanism. The arrange- ment of the Flexpand roughing and foreline hose allows operation of the system with or without a supplementary roughing pump. A wide variety of accessories are optionally available. Mason-Renshaw Industries, USA Circle nttrtther 47 on Reader Enquiry Service card

Pttrttpittg .sy.sfct~r of’ flrc Mtrson-Rcn.silu~~, unif sitol~~ittg Flespattd rotr~ghing and firclirtr hose