A magnetically shielded room has been constructed. It has three composite walls of permalloy and aluminum plates. The most crucial point for the characteristics of the shielded room is the connections of these plates. Residual DC magnetic field inside the room is below 1×10-7 T, and the value can be decreased down to 7×10-9 T within the space of one meter cube at the center of the shielded room by using three pairs of cancellation coils placed perpendicularly with each other pair close to the outside surface of the shielded room. Shielding factor for 50 Hz AC magnetic field is larger than 80 dB, and increases with increasing frequency up to a value larger than 135 dB at 18 MHz.
The correct theory of the capillary viscometer for gases is not yet established, as the customary theory assumes that the increase of volume and the decrease of density of the flowing gas due to the decrease of pressure are negligible, in spite of the decrease of the pressure itself not being negligible. In this paper, at first a differential equation to express Hagen-Poiseuille's law for gases is obtained on the basis that the mass flow rate of gas in the capillary tube, in a steady state, is a function of the distance from the axis of the capillary tube. Then some approximate solutions of the differential equation are obtained which represent approximately the measuring principle of the capillary viscometer for gases.
Analysis of the double injection current-voltage (J-V) characteristics with negative resistance in diodes having a single deep impurity level are made, taking the quantity of space-charge accurately into account. The sample concerned is divided into two regions, one in the low injection level and the other in the high injection level, as in the regional approximation method developed by Lampert and Shilling. The equations of the J-V characteristics are derived, considering space-charge formed by both minority and majority carrier injections. In order to evaluate the theory developed in the present analysis, Ni doped Si diodes were fabricated, and their J-V characteristics at various temperatures were measured. It was found that the theory is in good agreement with the experimental results.
Preparation, sensitization and developing procedures to fabricate holographic gratings with groove spacing between 2.7μm and 0.19μm on a thin PMMA film are described. Polymethyl methacrylate (PMMA) sensitized by 4_??_7% anthracence at the KrF laser wavelength (249nm) was used as the photoresist. A sensitivity about one hundred times larger as compared with pure PMMA was realized. This sensitization made it possible to obtain the grating by a single exposure of the short KrF laser pulse (12ns). As a recording equipment, a new interferometer was designed. Using this optical system, we were able to change the grating pitch over a wide range without readjustment of the optical axis.
Turn-on processes of pin negative resistance diodes are experimentally studied. A simple analytical simulation for the current-voltage characteristics is also given by using the regional approximation method. The experiments were carried out by using a planar-type Si pin diode doped with Au. It was found that a low resistivity region begins to spread into the i-region from the p-region before the sample voltage reaches the threshold voltage Vth and that the i-region is divided into two regions, i.e., negative and positive resistance regions when the negative resistance appears. These results are in good agreement with the results of the simulation.