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optical
coating
Control of the evaporating power applied in the A 700 Q is effected by measuring the change in reflection of the deposited layer, differentiating with respect to time and using this signal to control the source evaporation power. By this means the deposition rate can be held constant in spite of mains fluctuations or loading variations of the evaporator boat or crucible. Applications of the Lambdamatic 1000, as the system is known, will occur in depositing anti-reflection films, optical interference filters, dielectric layers, absorption-free mirrors, and beam splitters. Leybold-Heraeus Ltd Circle number 30 on Reader Enquiry Service card
advance
in vacuum
to Ltd
developments
Leybold-Heraeus Ltd. have announced a new automatic multi-layer coating system for optics, opto-electronics and related sciences. Comprising an A 700 Cl vacuum coating plant with a Lambdamatic control unit, it is said to give reproducible single or multi-layer films of X/4 thickness, or multiples. For layers of different refractive indices or densities it is accepted that optical thickness errors of up to 40% may occur, but with automatic multi-coating in the Lambdamatic the total error can be brought almost to zero, thanks to the constant optical supervision and correction of the process and its predefined cut-off point. Leybold claim that their optical (photometer) method of measuring the parameters of the deposited film is more accurate and effective than the quartz oscillator method, which measures deposited mass, as this does not take into account refractive index nor density variations.
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compressor pump. To enable fast cycling of the furance the ion/ titanium pump system can be held at vacuum isolated from the work chamber by a stainless steel bodied gate valve, during loading. The furance is fully programmable with facilities to allow run up to temperature at a pre-set heating rate and held at temperature for a set period. A multi-point recorder was included to indicate temperature pressure together with full vacuum and furnace control instrumentation. A controlled cooling rate is available as an option. A battery operated warning system was built into the system to provide complete protection against service failure. Warning lights indicate each possible area of malfunction keeping any down time to the minimum. Vacuum Generators Ltd Circle number 31 on Reader Enquiry Service card
VIG 30 ionization
gauge head
Vacuum Generators Ltd. announce the VIG 30 ionization gauge head for pressure measurement on vacuum systems. The VIG 30 gauge is a versatile design of Bayard-Alpert head, and is a glass/metal construction ; it is suitable for glassing direct to a system, or can be supplied welded direct to a ‘FC’ stule UHV flange.
A
furnace
Designed and manufactured by Vacuum Generators this specialized pumped Vacuum Furnace achieved a remarkable specification whilst undergoing acceptance trials at their Hastings Factory. The design vacuum pressure was specified to be better than 10-s torr at 1200°C in a hot zone 280 mm dia x 450 high but during trial tests, loaded with a 1 kg molybdenum specimen, it achieved 5 x 1 O-8 torr after 8 h at 12OO’C. Temperature uniformity was better than 1 ‘C over the specimen with two thermocouples set at 45 mm-140 mm from the hearth plate. This advanced specification is claimed to have been made possible by the choice of clean pumping equipment. A 400 I.s-1 triode getter ion pump was employed in tandem with a titanium sublimation pump hosed in a separate 304 mm vessel which provided a pumping speed of 2,800 I.s-r at the furnace chamber. Fore-pumping of the furnace was achieved by using a twin molecular sieve sorption pumped system together with a dry vane