A method for shaft sealing for transmission of rotation in cryogenic-vacuum chamber

Classified abstracts 3479-3487 torr to 10-z torr. Experiments confirm that such gauge calibration can be carried out accurately without the large-scale equipment normally associated with a standards laboratory. The system is of the dynamic gas flow type in which, by the use of a combination of a silicon carbide porous plug and an orifice, both of known molecular conductance, a reduction of a reference pressure by a factor of about lo5 is achieved and where this ratio is known and is independent of the molecular mass of the gas. Such a dynamic system enables satisfactory conditions to be established with quite modest pump speeds. A McLeod gauge of a design to operate over the pressure range 10 torr to lo- * torr is used to measure the reference pressure P,~~ of the test gas, which gas is expanded by a measured volume ratio of approximately 100 times and then reduced in pressure a further lo5 times by the novel dynamic flow method described, so achieving a linal pressure of lo-’ plep Particular attention is paid to the treatment of experimental error in the discussion of this system. K J Close et al, Vacuum, 27 (9), 1977.511-517. 23. PLUMBING,

VACUUM

VALVES,

BAFFLES

AND TRAPS 23 high vacuum joints of metals and

3479. Very low temperature-proof insulators. (Germany) Three high vacuum joints are described which can be used in the temperature range 4.2 K to room temperature. The extreme gas tightness of these joints is not impaired by repeated and fast temperature changes. (Austria) Von F Schauer, Vakuum-Tech, 26 (6), 1977. 172-173 (in Germun). 23 3480. A small-size high-vacuum rotary motion feedthrough. (USSR) Construction of a simple, bellows-sealed eccentric small-size highvacuum rotary motion feedthrough is described. The feedthrough can be easily modified for transmission of translatory motion in vacuum. The described feedthroughs are reliably used in a working vacuum of 10mg torr with periodic bakeouts to 300°C. Yu A Benediktov and B A Zakalov, Prib Tekh Eksper, No 1, 1976, 159-160 (in Russiun). 23 3481. Hermetization of windows of barium and calcium fluorides. (USSR) The method of sealing of crystalline windows of barium and calcium fluorides to glass by enamels is described. The joints can be baked to 400 to 450°C without interruption of vacuum in sealed-off devices. L P Sbishatskaya, Prib Tekh Ekper, No 1, 1976,224-225 (in Russian). 23 3482. A method for shaft sealing for transmission of rotation in cryogenic-vacuum chamber. (USSR) A method for shaft sealing for transmission of rotary motion into the cryogenic-vacuum chamber is described which is based on utilization of an inner vessel with liquefied gas both as a liquid seal and as cooling agent. Construction of this rotary vacuum seal is described. M D Tyavlovskiy and M N Los, Zuvod Lob, 42 (3), 1976, 306307 (in Russion). 23 3483. High-vacuum flange joints with metallic gasket. (USSR) Construction and technical characteristics of high-vacuum flange joints for tubings ranging from 10 to 250 mm are described. The joint construction is similar to the conflat type, but the ridge has a trapezoidal shape. The described joints with copper gasket are vacuumtight with leakage less than 8 x lo-i2 m3 Pa/s in the temperature range 300 to 750 K. The life of one gasket is longer than 200 h at a temperature of 750 K. Radial surface grooves of depth less than 0.04 mm on gasket are permissible. A N Maleev et al, Prib Tekh Eksper, No 2, 1975,170-l 7 1 (in Russian).

III.

Vacuum

30. EVAPORATION

applications AND DEPOSITION

IN VACUO

30 34&4. Structure and properties of vacuumdeposition thin films: a new basic relationship. (USA) We show that a wide range of vacuum-deposited materials exhibits sharply optimized properties and, in some cases, unusual crystal structures when the temperatures at which the materials are con-

densed (the substrate temperatures) are in a narrow range near 0.33 of their respective normal boiling points. This generalization applies to essentially all the really sharp optima we can find (for nonmetals) in the recent literature. The materials include organ& (our own data on anthracene, phthalocyanine and pyrene) and inorganics (Se, ZnO, SnTe and most of the sulphides, selenides and tellurides of lead, cadmium and zinc). Both polycrystalline and epitaxial films are involved. The properties optimized include charge-carrier mobility, smoothness, epitaxial order, electrophotographic performance and photo-emf. We propose a possible explanation for these effects which gives good numerical agreement with experiment; our main postulate is that the optimum properties occur when the rate of reevaporation from well-defined, but disordered, regions of the growing films (probably glassy areas) is just sufficient to exceed the deposition rate. (Canada) P S Vincett et al, J Appl Phys, 48 (9), 1977,3800-3806. 30 3485. Structural and magnetic disorder effects on electron transport properties of Cu-Ni films. The resistivity and thermoelectric power of Cu,Ni, -= films containing 0, 15, 20 and 25 at. % of Cu have been studied in the temperature range 300-675 K. The effect of postdeposition annealing on the microstructure and the transport properties of the alloy films deposited at 100 and 300 K have been studied in detail. The contributions to the resistivity of the alloy tilms of different compositions due to the structural, thermal, alloying and magnetic disorder present in the films have been established. The thermoelectric power has been separated into two terms, one corresponding to the structural disorder and the other to the rest of the disorder effects. The presence of structural disorder has been shown to enhance the spin-disorderinduced effects on electron transport properties. The observed concentration and temperature dependence of the transport properties and their anomalous behaviour at the Curie temperature can be understood in terms of the thermal and structure-induced spindisorder scattering in the alloy films. (India) A P Thakoor and K L Chopra, J Appl Phys, 48 (9), 1977, 3850-3857. 30 3486. Structural and transport properties of CdS Elms grown on Si substrates. (USA) Epitaxial films of CdS have been grown on thermally cleaned singlecrystal Si substrates. The films were grown by electron-beam evaporation of CdS powder in a UHV system. X-ray Laue and transmission electron diffraction techniques have been used to examine the structure of the films. It has been found that epitaxial growth occurred on (111) substrates at a deposition temperature of approximately 340°C. Polycrystalline films were obtained at temperatures below 300°C on (111) substrates. Films grown on (100) substrates were polycrystalline over the range of deposition temperatures lOO-390°C. The electron transport properties of these films have been studied. The Hall mobility measurements of films grown on (111) substrates gave a value of 320 cm2 (V s)-’ for the epitaxial films, decreasing to approximately 100 cm2 (V s)-’ for polycrystalline films grown at 200°C. For films grown on substrates the Hall mobility ranged from 60 cm* (V s)- ’ at 200°C to approximately 90 cm* (V s)- ’ at 340°C. The electrical resistivity of the epitaxial films was 20 ficm and that of the polycrystalline films ranged from 10 to 300 Qcm. Photoconductivity measurements of these films showed a relatively high trap density extending to greater than 1 eV above the valence band edge. A peak in the response at 800 nm is thought to be due to that of the Cd vacancies. (GB) F M Livingstone et al, J Appl Phys, 48 (9), 1977,3807-3812. 30 3487. The adsorption and early stages of condensation of Ag and Au on W single-crystal surfaces. (USA) Silver and gold were evaporated up to several monolayers in thickness onto W {llO} and {lOO} single-crystal surfaces in the temperature range between 300 and 1300°K. The mode of growth and the structure of the layers were studied by Auger electron spectroscopy (AES) and low-energy electron diffraction (LEED). The results are compared with thermal desorption spectroscopy (IDS) data and work-function change (a$) measurements. They show certain similarities but also some striking differences between the two systems Ag/W and Au/W, and a strong crystallographic anisotropy of adsorption and condensation. E Bauer et al, J Appl Phys, 48 (9), 1977,3773-3787. 155