This paper is a survey of methods of high-impulse current and voltage measurement. Typically, such measurement techniques must now include capabilities for measuring high-energy impulses having peak powers as high as many megawatts, currents as high as many mega-amperes, or voltages as high as several megavolts, with rise times as short as a fraction of a microsecond (even as short as the subnanosecond range for moderately high-energy impulses). These capabilities had to be attained in recent years to meet the needs of various areas of scientific research employing such high-energy impulses. This represents a significant extension in the state of the art of such measurement techniques beyond their more traditional role in development and testing of high-voltage bulk power system equipment. The three most commonly used methods of high-impulse current measurement are the magnetic probe, current transformer, and "pure" resistive shunt methods. These methods are treated in considerable detail. High-voltage capacitive dividers, resistive dividers, and reflection-type attenuators are covered as the principal methods of high-impulse voltage measurement, with some added discussion of the means of insulating such devices. A brief description is given of schemes involving use of laser light sources to measure high-impulse currents and voltages by means of magnetooptic and electrooptic effects. Diagnosis of the complete properties of high-power pulses is also discussed. The emphasis throughout the paper is on a review directed toward practical measurement considerations and techniques.

High-Impulse Current and Voltage Measurement

Amorphisation of silico single crystals during different mass 80 keV ions bombardment (B+, C+, Ne+, Ar, Sb+) has been studied by means of three independent techniques, (a) IR absorption at I,8 μ wavelength (divacancy absorption), (b) IR reflection near a fundamental absorption edge, and (c) electron microscopy and fast electron diffraction. Irradiation was carried out at room temperature. From the analysis of data obtained it can be concluded that two types of disordered regions arise during ion bombardment, (a) amorphous regions (A.R.) and (b) disordered, but still processing crystalline structure regions; which we call the crystalline disordered regions (CDR). In CDR the defect concentration is so high that divacancies do not appear. The defect concentration in CDR gradually increases with the increasing of irradiation dose. When; the defect concentration achieves some critical value CDR transforms sharply to an amorphous state. Such amorphisation mechanism prevails for light ions. For heavy ions (Sb+) amorphisation arises mainly from a one-step AR formation. The proposed model of amorphisation gives the qualitative explanation of dose dependence of refractive index for different ions.

On Silicon Amorphisation During Different Mass Ions Implantation

Apparatus and method for modulating the phase or the amplitude of a monochromatic light beam, the apparatus including in one embodiment a Mach-Zehnder interferometer that consists of two beam splitters or beam combiners, a fully reflective mirror and an electro-optical crystal for modulation of one of two beam components. The electro-optical crystal serves as an optical resonator for the portion of the light beam admitted into the crystal material, using total internal reflection of the light beam from two or more of the crystal surfaces. The crystal has a high finesse so that a relatively small change in voltage applied across the crystal produces a large (≈180°) change in the external phase shift associated with the modulated component of the light beam. The modulated and unmodulated light beam components may be recombined for purposes of communication of information, using the mutual extinction of the two beam components when the optical phase shift between the two beam components is approximately 180°. Transverse or longitudinal electro-optical materials can be used for the crystal, and the driving voltages required are less than 50 volts in some configurations. Communications at frequency up to and beyond 1 GHz. are possible.

Resonant phase modulator

Viewing the central nervous system exclusively in electrical field terms, the cortex may be considered a lens. The “minimum ray characteristic” in Herzian wave theory indicates that the absolute unit of information measurement can be undefinable. Thus, whereas in the auditory system, where signal frequency is readily detectable, a clearly definable “bit” of information is objectively available, in the visual system, where edge detection is not carried by wavelength, the absolute unit can only be defined physiologically. The modulation of transmitted information in the cortex could be carried out by delay methods of conduction. For this to be true, frequency in the central nervous system must be coded in the time domain and represented by transcortical “arrival patterns.” It is shown that only during positive dc activity in the cortex is input registered. If a “perceived object” is defined exclusively in terms of degrees of freedom, then “object constancy” reduces itself as a problem to the question how degrees of freedom may remain invariant under transformations of amplitude and phase. The “carrier” for cortical information is suggested to be an indigenous cortical rhythm triggered by thalamic input. Interferometry thus occurs between the sensory input and this indigenous activity.

The cerebral cortex as a diffractive medium

In 1932, the American physicist OSTERBERG [5.1] used light reflected by a vibrating surface for interferometric analysis of the vibrations of piezoelectric crystals. He showed that the time-averaged distribution of brightness over the surface being studied observed at the interferometer output is described by a function of the kind 

$$I = {I_0}\left[ {1 + {J_0}\left( {\frac{{4\pi A}}{\lambda }} \right)} \right],$$

where J0is a zero-order Bessel function, A is the amplitude of the vibrations, and λis the length of the light wave.

Donald F. Nelson

Papers

The Modulation of Laser Light