Abstract: A new and improved gain stabilization system for radioactivity well logging apparatus of the type having a scintillation crystal and optically coupled photomultiplier in a sonde to detect radiation in the borehole and formation elements in response to neutron bombardment. The gain stabilization system includes a light emitting diode driven by a pulser and furnishing scintillations to the photomultiplier, resulting in a stabilization pulse which is furnished to electronic circuitry at the surface for stabilization purposes.

Abstract: A well logging system and method in which a transmitter in a borehole has at least two radiation detectors sensing either the same condition or two different conditions relating to the earth's formation traversed by the borehole and providing pulse signals having reference pulses and data pulses corresponding in number and peak amplitude to the sensed condition. Each pulse signal is sampled at different times by a sampling circuit which provides pulses of opposite polarity whose amplitudes correspond to the amplitudes of the first pulses occurring during sampling periods. The pulses from the sampling circuit are conducted to surface electronics by a single conductive path such as the inner conductor and the shield of an armored coaxial cable. The surface electronics include a pulse separation circuit which separates the pulses polarity. Processing circuits process the separated pulses to provide records of at least two spectra.

Abstract: A conventional type radiation detector in cooperation with a photomultiplier tube provides data pulses of one polarity, corresponding in peak amplitude and number to detected radiation in a borehole traversing an earth formation. Each data pulse is effectively converted to two pulses of different polarities, with one pulse starting when the other is completed and transmitted over a common well logging cable. The creation of a second pulse of an opposite polarity cancels out the low frequency component of the pulse so that they arrive at the surface as a pulse of a single polarity having a very short tail and a fast rise time. This permits more pulses to be transmitted within a given time period than heretofore existed. Surface electronics process the transmitted pulses to provide a record of the sensed condition in the borehole.

Abstract: A well logging system and method in which a transmitter in a borehole has at least two radiation detectors sensing either the same condition or two different conditions relating to the earth's formation traversed by the borehole and providing data pulses corresponding in number and peak amplitude to the sensed condition. The transmitter also includes a reference pulse source and circuitry for combining the reference pulses with each set of data pulses to provide combined pulse signals. Each combined pulse signal is sampled at difference times by a sampling circuit which provides pulses of opposite polarity whose amplitudes correspond to the maximum amplitude pulses occurring during sampling periods. The pulses from the sampling means are conducted to surface electronics by a single conductive path such as the inner conductor and the shield of an armored coaxial cable. The surface electronics includes a pulse separation circuit which separates the pulses by polarity.