Abstract: ESR microscope systems and methods for examining specimens using both continuous wave and pulsed modes in the 9 to 60 GHz range. The ESR microscope uses an image probe comprising gradient coils in addition to conventional modulation coils (in continuous wave mode) or magnetic field bias coils (in pulse mode), and a resonator constructed from high permittivity material. The systems and methods also involves the use of sample containers that permit the precise placement of samples in relation to the image probe. The microscope uses a microstrip or thin coaxial or dielectric antenna to obtain a high coupling coefficient to the specimen being imaged. The microscope systems provide resolution at the single micron level, and permit the observation of images comprising tens to hundreds of pixels for each of two or three dimensions in a few minutes. Novel stable radicals used as the imaging media are also described.

Abstract: The present invention features an active sensor for detecting a magnetic field. The sensor includes a pickup coil wound on a semi-flexible bobbin, which in turn is mounted on a suitable core assembly. Optionally, the core/coil assembly can then be mounted on a flexible substrate. Thin strips of either standard or amorphous crystalline high-permeability alloy are laminated to form the core. Once the coil has been assembled with the core laminations, output leads from the coil are connected to conductors of a miniature coaxial cable, the sheath of which is grounded to the core laminations. An operational amplifier is connected to the coil assembly. The operational amplifier has a positive feedback path to substantially cancel the combined dissipative loss of resistance and core eddy currents of the coil assembly. The operational amplifier also has a negative feedback path to set the maximum gain of the active sensor.

Abstract: The present invention features a magnetic field compensation system for suppressing alternating or time-varying magnetic fields in a large volume of space. A magnetic sensor detects within a predetermined range of frequencies and generates a signal. A coil or pair of Helmholtz drive coils is positioned into a volume containing the magnetic sensor. A preamplifier is connected to the magnetic sensor for amplifying the signal. A signal processor is connected to the preamplifier for receiving the signal and for providing phase correction and gain. The signal processor has both an averaging and an absolute peak detector for determining magnetic field average and peak excursions. A power amplifier is connected to the coil or pair of Helmholtz drive coils and to the signal processor for receiving and amplifying the processed signal and for applying it to the coil or pair of Helmholtz drive coils.

Abstract: An extremely fast high-voltage driver for nanosecond-level switching of gallium arsenide PIN semiconductor devices and other reactive loads utilizes two stages of voltage level translation to permit low voltage TTL logic control signals to control the application of high voltage switching pulses to a load. The circuit utilizes an input stage responsive to TTL level signals to drive a first voltage level translating stage which produces high voltage pulses complementary to the input pulses. The increased voltage pulses are supplied through an intermediate power gain stage to provide amplification of the pulse power level. The amplified pulse is supplied to an output stage for additional level conversion to thereby provide high voltage switching signals to a PIN switch or other reactive load.