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A new Si‐SiO2 bonding process has been developed to achieve a uniform spacing between two silicon wafers of 2 and 3 in. diam. Spacings between 0.1 and 3.9 μm have been obtained so far. Hydrostatic pressure is used to force the two wafers into intimate contact at points where bonding is desired. The bonding is performed at a temperature of ∼1150 °C. The uniformity of bonding and spacing between the wafers is checked by a Fabry–Perot interferometer technique at room temperature and by measurements of superfluid density of He II at low temperature. These results are compared with ellipsometer and stylus measurements of the oxide thickness which is designed to govern the wafers’ spacing. We find that these different techniques yield consistent results.

We present the results of various measurements we have made to characterize Nuclepore filters. These include nitrogen and helium adsorption isotherms, heat capacity and SEM studies of pore size distribution and pore density.

We discuss the construction and performance of two indium superconducting thermal switches. We find that a satisfactory performance can be obtained with rather impure indium stock. Comparison with earlier data indicates our work to be the only one where the thermal conductivity of both the normal and superconducting state have been measured below 1.3 K.

We have constructed a multishielded Dewar which we have tested at nitrogen and helium temperatures. The Dewar is of extremely simple design, requires no special insulating materials, and attains excellent performance. With an arrangement of 20 shields we have obtained evaporation rates of 5.6 and 3.0 liquid cm3 per hour for liquid helium and nitrogen, respectively. We report measurements of temperature distributions and evaporation rate as a function of the number of shields.