Abstract: Resolution of thin beds made by a natural gamma ray logging tool is improved using a relation between the width of the response and the bed thickness. The peak gamma ray of the bed is determined using another relation between the measured gamma ray response and the bed thickness.

Abstract: A tool for formation logging includes a support configured for movement in a borehole; a source mounted on the support, the source configured to emit neutrons and gamma rays; and at least one sensor mounted on the support and spaced apart from the source, wherein the at least one sensor is configured to detect at least one selected from the group consisting of gamma rays and neutrons. A method for formation logging in accordance with one embodiment of the invention includes emitting neutrons and gamma rays into a formation, using a source on a logging tool disposed in a borehole penetrating the formation; and detecting gamma-ray signals and neutron signals scattered by the formation, using at least one detector on the logging tool.

Abstract: Formation strontium concentrations are measured utilizing a borehole tool. A log may be provided as a function of depth or distance. The strontium measurements can be correlated chronostratigraphically to provide a depth to absolute time correlation. Measures of strontium made in the borehole can be correlated to information obtained via seismic exploration of the formation traversed by the borehole. Measures of strontium in multiple boreholes of a single formation can be correlated.

Abstract: In methods according to the invention, subsurface formations below the surface of the earth are detected by introducing a condensable material in vapor form into the subsurface formation, measuring radiation of the condensable material, increasing the concentration of the condensable material through condensation, measuring radiation of the condensable material of increased concentration, and comparing the radiation of the condensable material of increased concentration to the radiation of the condensable material in vapor form to identity the presence of the condensable material.

Abstract: A gamma ray logging system and a method of calibrating a detected gamma radiation spectrum. The gamma ray logging system includes a gamma ray detector for detecting gamma radiation, an analyzer for generating a detected gamma radiation spectrum from the detected gamma radiation, and a processor which is configured to perform a calibration of the detected gamma radiation spectrum. The method of calibrating the detected gamma radiation spectrum includes selecting at least two data points from the detected gamma radiation spectrum, determining a mathematical relationship from the selected data points, and using the mathematical relationship to generate a calibrated gamma radiation spectrum from the detected gamma radiation spectrum.

Abstract: A charged particle (e.g. photoelectron) spectrometer is operable in a first mode to produce an energy spectrum relating to the composition of a sample being analysed, and in a second mode to produce a charged particle image of the surface of the sample being analysed. A detector is used to detect charged particles produced in both modes of operation. A method of operation of the spectrometer includes the step of selecting which of said first and second modes to use and the detector being operated accordingly.

Abstract: A method for controlling voltage applied to a photomultiplier used in a scintillation counter radiation detector includes determining numbers of voltage pulses having each of a plurality of predetermined amplitudes generated by the photomultiplier in response to radiation events being imparted to a scintillation detector. The numbers of voltage pulses at each of the predetermined amplitudes is conducted to a trained artificial neural network. The artificial neural network generates a signal corresponding to an amount of adjustment to the voltage applied to the photomultiplier.

Abstract: Thermally tunable optical sensors are used in sampling tools for analysis of samples from a wellbore. The thermally tunable optical sensors generate a series passbands of wavelength emissions and detect attenuation in a signal thereof. The attenuation detected is processed and used to determine aspects of the samples. Analysis may be completed remotely (outside of the wellbore), within the wellbore (during drilling or otherwise), or as a part of another process such as fluid management, transport and refinement.

Abstract: Methods and apparatus for analyzing gas-oil-water compounds in oilfield and other applications are disclosed using terahertz radiation. A sample analyzer includes a sample chamber having a fluid communication port configured to receive the sample. The analyzer also includes a filter to filter samples and selectively remove oil, water or gas from reservoir mixture received by the sample chamber. A terahertz (THz) radiation detector is provided in electromagnetic communication with the sample. The terahertz detector provides a detected output signal indicative of the terahertz electromagnetic radiation detected from the sample. In some embodiments, the device also includes a terahertz source illuminating the sample, the terahertz detector detecting a portion of the terahertz source illumination as modified by the sample. The detected portion of the spectrum of terahertz radiation can be processed to analyze the composition of the sample.

Abstract: An apparatus and method for logging information concerning the identity and/or condition of materials present within a wellbore is based on gamma ray spectroscopy. The apparatus includes a gamma ray source and at least one spectral gamma ray detector, with a controller capable of commanding or effecting digitization of the spectral data obtained by the detector. The data can be stored in a memory system and downloaded for analysis. The invention eliminates the problem of instrument “gain” and, because it generates spectral data, provides downhole qualitative and quantitative information beyond that of conventional non-spectral downhole imaging means and methods. Applications include, but are not limited to, reliably determining gravel pack integrity.

Abstract: The present invention provides an apparatus and method for high resolution spectroscopy (approximately 10 picometer wavelength resolution) using a tunable optical filter (TOF) for analyzing a formation fluid sample downhole and at the surface to determine formation fluid parameters. The analysis comprises determination of gas oil ratio, API gravity and various other fluid parameters which can be estimated after developing correlations to a training set of samples using a neural network or a chemometric equation.

Abstract: A gamma ray logging system and a method of calibrating a detected gamma radiation spectrum. The gamma ray logging system includes a gamma ray detector for detecting gamma radiation, an analyzer for generating a detected gamma radiation spectrum from the detected gamma radiation, and a processor which is configured to perform a calibration of the detected gamma radiation spectrum. The method of calibrating the detected gamma radiation spectrum includes selecting at least two data points from the detected gamma radiation spectrum, determining a mathematical relationship from the selected data points, and using the mathematical relationship to generate a calibrated gamma radiation spectrum from the detected gamma radiation spectrum.

Abstract: A method for determining concentrations of naturally occurring radioactive elements in earth formation by analysis of gamma ray energy spectra measured by at least one gamma ray detector while the borehole is being drilled. Gain of the gamma ray detector is controlled automatically through analysis of the spectra. The one or more gamma ray detectors are disposed at the periphery of the downhole instrumentation to maximize sensitivity. Elemental concentrations of naturally occurring radioactive elements such as potassium, uranium and thorium are measured either as a function of depth in the borehole, or as a function of aximuthal sectors around the borehole wall, or as a function of both depth and azimuthal sectors.

Abstract: A well logging instrument including a plurality of detectors having different precisions and accuracies, the more precise detectors generally having lower accuracies. The detectors are responsive to the interaction of radiation from a suitable source on the instrument with earth formations. Outputs from the plurality of detectors are smoothed and combined to provide processed measurements with improved accuracy and precision.

Abstract: There is provided an apparatus for monitoring a size of a particle, including (a) a laser beam source which radiates a laser beam to an area in which particles exist, (b) a photodetector which receives the laser beam having been scattered by the particles, and outputs image data including brightness of pixels, (c) an area detector which detects pixels corresponding to an area on which the scattered laser beam is incident, based on the image data, (d) a maximum brightness detector which detects a maximum brightness among brightness of the pixels detected by the area detector, and (e) a measurement unit which compares the maximum brightness to a predetermined threshold brightness to thereby measure a relative size of the particles.

Abstract: A method of monitoring the density of a subterranean fluid comprises the steps of: using a subterranean radiation detector to obtain measurements over a plurality of time intervals of the amount of natural background radiation traversing said fluid, and calculating the relative density of said fluid at each of said time intervals from said measurements.

Abstract: An apparatus and method for detecting the presence of at least two predetermined known materials in a test sample are disclosed. The apparatus includes a sample addition station for adding a sample to a test column in the apparatus, a reagent station, a washing station, a detection station for detecting signals on the snares of the test column due to the presence of the predetermined known materials in the sample, and conveying means for conveying the test column from the sample addition station to the reagent station, washing station, and detection station. The test sample is introduced into a test column which has at least two snares for capturing the predetermined known materials, and the snares are separate spatially one from another. Each snare has a capture material specific to the associated predetermined known material. The detection station has a plurality of detectors for detecting signals on the snares of the test column due to the presence of the predetermined known materials in the sample.

Abstract: A method of determining GOR comprising subjecting a fluid to spectroscopic analysis at a first wavelength sensitive to gas and a second wavelength sensitive to oil, determining a response matrix for the contribution of gas at the first and second wavelengths and the contribution of oil at the first and second wavelengths, determining a signal response vector and the two wavelengths, calculating a mass fraction vector from the response matrix and the signal response vector and using the mass fraction vector to determine GOR.

Abstract: A circuit for reading out a signal from an infrared detector includes a current-mode background-signal subtracting circuit having a current memory which can be enabled to sample and store a dark level signal from the infrared detector during a calibration phase. The signal stored by the current memory is subtracted from a signal received from the infrared detector during an imaging phase. The circuit also includes a buffered direct injection input circuit and a differential voltage readout section. By performing most of the background signal estimation and subtraction in a current mode, a low gain can be provided by the buffered direct injection input circuit to keep the gain of the background signal relatively small, while a higher gain is provided by the differential voltage readout circuit. An array of such readout circuits can be used in an imager having an array of infrared detectors. The readout circuits can provide a high effective handling capacity.

Abstract: A well assembly for extracting production fluids from at least one production zone of at least one well includes a production pipe for transporting fluid downstream to a surface, a packer for defining the production zone, and a fiber optic sensor package disposed substantially adjacent to a downstream side of the packer. The fiber optic sensor package measures parameters of the production fluid and communicates these parameters to the surface to determine composition of the production fluid entering the production pipe through each production zone. The production pipe has a zone opening for allowing the production fluid to enter the production pipe and a control valve for controlling the amount of production fluid flowing downstream from each production zone. The production pipe control valve is adjusted to optimize fluid production from the particular production zone of the well based on fluid parameters measured by the fiber optic sensor package.

Abstract: A closed-loop stabilization system and method for a radiation detector system including a scintillator and a light sensing device for detecting the scintillation light produced in the scintillator through interaction with impinging radiation. A spectrally stable gamma ray measurement for downhole and other non-isothermal gamma ray measurement applications is obtained by use of a light source for emitting photons, preferably ultra-violet photons, into the scintillator that are not detectable by the light sensing device. The light source causes the scintillator to fluoresce at a wavelength detectable by the light sensing device, and the change in measured fluorescence is used to adjust system gain to account for variations in scintillator output attributable to environmental conditions. In this manner, the stabilization system adjusts the system gain to maintain consistency among radiation measurements over a wide temperature range.

Abstract: A method for calibrating a logging tool that is exposed to an external energy spectrum, comprising the steps of: (a) providing a stabilization source that emits a stabilization signal having a known energy; (b) providing a receiver that receives a total spectrum that comprises the sum of the external energy spectrum and the received stabilization signal; (c) discerning the stabilization signal in the total spectrum by the steps of: calculating the centroid of the area under the total spectrum; adjusting the gain of the tool on the basis of the calculated centroid; dividing a portion of the spectrum that includes the known energy level of the stabilization peak into a number of windows of equal width, with an equal number of windows on either side of the stabilization peak energy; using the count rates in each of the windows to calculate a value D.sub.n that is proportional to the n.sup.

Abstract: A well logging instrument and method that remove vibration induced noise from the output of a detector including a scintillation crystal. The invention is based on a realization that pulses induced by vibration during MWD operations are characteristically periodic, whereas pulses generated down hole by gamma rays occur at random intervals and are characteristically non-periodic. The instrument and method involve positioning a scintillation crystal package in the high vibration environment for interaction with incident radiation, using a light sensing device to convert photons received from the scintillation crystal package into an electrical signal which over time is composed of radiation induced events that are non-periodic and vibration induced events that are periodic, distinguishing the periodic events using a time history of the electrical signal, and removing the periodic events from the electrical signal to provide a corrected electrical signal from which vibration induced components have been removed.

Abstract: A system and method for evaluating a geological formation is described which compares actual wireline log measurements from a number of wireline logging tools to predicted tool response logs. The system and method uses a forward model of each tool response, given a formation description, to predict a set of wireline logs. Comparing the predicted logs with the actual measured logs yields a mismatch error. The system and method iteratively adjusts the formation description to minimize the mismatch error to obtain a "best" formation description. In one form, the formation description includes petrophysical properties (porosity, density, saturation) and geometry properties (dip, bedding, invasion). In a more complicated form, the formation description also includes a model of petrophysical mixing laws and formation material content. In the special case of a horizontally layered formation and linear tool response models, there exists a computationally efficient version of the system and method.

Abstract: A method for providing gain stabilization to a nuclear spectroscopy tool by use of gross features of largely invariant spectra. A particle or gamma ray energy spectrum of an earth formation and wellbore are measured. A ratio of the number of particles or gamma rays measured in a first energy window to the number of particles or gamma rays measured in a second energy window is calculated. The gain of the nuclear spectroscopy tool is adjusted as a function of the calculated ratio. The first energy window is selected to span substantially an entire range of measured energies for the spectrum and the second energy window is selected to span an upper range of the measured energies for the spectrum.

Abstract: A standoff compensation system is disclosed for use in an LWD system implementing gamma density and/or neutron porosity measurements. An acoustic transducer is provided to measure the standoff distance between the logging tool and the borehole wall. The present invention includes a downhole processor for determining a weighting factor for the density and/or porosity measurements based upon the measured standoff distance. The weighting factor can either be calculated by the downhole processor according to a predetermined weighting function, or can be retrieved from a pre-calculated look-up table in ROM. The processor then multiplies the weighting factor by the count data from the sensor to determine a weighted count value. The weighted count values are accumulated during an averaging period and normalized, so that a single normalized count value can be generated and either stored in downhole memory, used immediately, or transmitted by telemetry to the surface.

Abstract: A method and apparatus for providing temperature compensation in gamma radiation detectors used in measurement-while-drilling applications in oil and gas exploration. During the initial calibration of a gamma radiation detector, a source of radiation in the form of Americium 241 provides gamma radiation narrowly centered at 60 KeV. The variation in the output signal of the detector as a function of temperature is then determined by placing the detector in close proximity to the radiation source while monitoring the variation in the magnitude of the output pulses as a function of temperature. The detector includes a temperature compensation circuit that generates a threshold voltage whose magnitude corresponds to the desired threshold energy of gamma radiation. The temperature compensation circuit uses a temperature sensor to vary the magnitude of the threshold voltage as a function of the operating temperature of the detector.

Abstract: A method and apparatus for verifying operation and achieving gain stabilization in a helium-3 proportional counter radiation detector utilized in nuclear logging operations. The detector includes a beta-minus particle source selected to provide a predetermined number of radiation counts for a specified time period to verify detector operation. The beta-minus source is further utilized to achieve detector gain stabilization by defining two energy windows on either side of the characteristic beta-minus energy peak. The difference in counts for the two energy windows is used to define an error signal which is applied to negative feedback loop in the detector electronics. The beta-minus source is preferably selected such that the type of source and activity is exempt from Nuclear Regulatory Commission licensing and safety requirements.

Abstract: A system for measuring fast neutron induced gamma ray energy spectra in cased wellbores. The system includes an electronic source of monoenergetic 14 MeV fast neutrons, a high density bismuth germanate scintillation detector, a downhole pulse height analyzer and a highly accurate gain stabilizer circuit. The gain stabilization utilizes the iron (Fe) edge in the catpure gamma ray spectrum to establish system gain since iron is always present in the tool case and the wellbore casing.

Abstract: The present invention provides a method of stabilizing the gain of spectroscopy equipment using the actual measured spectrum of the formation of interest and thereby eliminating the need to use external radioactive calibration sources. The gain is measured and adjusted using spectral fitting techniques. In these techniques, an energy spectrum of the radiation from an earth formation is measured. The measured spectrum is compared to a standard spectrum or composite spectrum. As a result of the comparisons, deviations between corresponding features of the two spectra are determined. Gain correction signals are calculated based on the determined deviations. The gain of the spectroscopy equipment is adjusted based on these calculated correction signals.

Abstract: This disclosure sets out a method for applying a temperature correction to calculations that employ measurements made with scintillation detectors. Temperature measurements are made at or near the scintillation detectors and utilized in corrections employing measurements made with the scintillation detectors to obtain quantities that are relatively independent of temperature.

Abstract: Logging method and tool string for identifying and determining the concentrations of subsurface formation elements next to a borehole, by (i) using a broad energy spectra neutron source (such as a chemical source, like AmBe), and (ii) detecting and counting the delayed gamma rays resulting from the activation by the neutrons of atoms of least one element of interest (e.g. aluminum). Two gamma ray detectors may also be disposed on either side of the broad energy spectra neutron source, for detecting and counting the prompt gamma rays resulting from the capture of neutrons by atoms of elements, such as Si, Ca, Fe, S, H, or Cl, Gd, Ti, or K.The broad energy spectra neutron source is used for both the "activation" and the "capture" measurements. The tool string may also include a natural gamma ray tool for the determination of uranium, thorium and potassium, and for measuring the background to be subtracted from the gross Al activation measurement.

Abstract: An optical card recording and reproducing device including an optical head for emitting a light beam spot to the optical card having a plurality of parallel data tracks to which data is recorded; a transfer system for transferring the optical card and/or the optical head; and a track number confirmation means for confirming the track number recorded in the address data area in the data track of the optical card. The optical card recording and reproducing device also includes a transfer stopping means for stopping the optical head when an incorrect track number is deleted. The system minimizes the relative transfer distance between the optical card and the optical head, and at the same time, the total relative transfer distance of the optical card and/or the optical head when confirming the track number more than twice. Thus, the total time required for track number confirmation can be greatly shortened.

Abstract: A scintillation detector providing a photomultiplier tube mounting system capable of withstanding substantial vibration and the like without damage to the photomultiplier tube. The mounting system provides a resonant frequency substantially above the frequency of the vibration normally encountered to prevent amplification of the vibration. The photomultiplier tube is mounted within a support tube with a thin layer of elastomeric material. The support tube is in turn mounted in a light-tight tube by spaced elastomeric rings having a relatively high spring rate. The support tube is provided with openings which render the support tube radially resilient so that thermal expansion of the elastomeric material between the support tube and the photomultiplier tube does not result in high compressive loads on such tube. Further, the elastomeric material can elastically flow into the openings in the support tube to relieve compressive stresses which would otherwise occur.

Abstract: A pulse height analyzer for spectrocopy thermal multigate decay well logging systems is disclosed and has an input section comprising a peak time determining circuit locating a peak occurrence. The peak is determined relative to a threshold voltage determining circuit. On peak detection, a timing signal is formed for a control circuit. This operates a sample and hold switch at the output of an amplifier for the input. This switch inputs to an A/D converter driving a buffer. Various handshake signals cooperate with a telemetry system to transfer the peak time A/D valve for pulse height measurement.

Abstract: This disclosure is directed to a detector system for use in measuring while drilling (MWD) equipment. It comprises preferably duplicate chambers positioned to one another and mounted in a MWD system where they are subject to the same shock and vibration. The shock and vibration impinge on the two chambers, and cause two output signals to be formed. The two output signals are applied to a differential amplifier so that the microphonic portion of the signal is cancelled. This then leads to a differential output signal which carries in it the signals representing nuclear events detected by the similar or duplicate detector means. Alternately, a single chamber can be used if it is provided with two anode wires and they are connected to the differential amplifier for signal cancellation.

Abstract: Nuclear spectroscopy method and apparatus for the stabilization of an energy spectrum, made from a signal, emitted by a radiation detector, and containing nuclear events, represented by pulses, whose amplitude is a measure of the energy of the particles, such as gamma rays, collected by the detector, the spectrum including at least a first reference energy peak coming from an ancillary nuclear source, wherein the method comprises: detecting the radiation under analysis by two detectors between which is placed the ancillary source; establishing at least one coincident spectrum corresponding to pairs of events simultaneously detected in both detectors and originating from the ancillary source; and stabilizing the coincident spectrum by using one energy peak of said spectrum as said first reference energy peak.

Abstract: The cutting horizon for mining machines, such as coal ploughs and roll loaders, in particular the position of the coal-rock interlayer, can be determined with the aid of light signals of selected wavelengths at reflection layers, at least one sensor head guiding iding dragging along the floor and having at least one optical waveguide bundle constructed as measured-value pickup and guided in a passage sealed with a crystal window being arranged on the mining machine and a transmitted and receving station being arranged on the machine body. For clear identification of the carbon-rock interlayer the passage (6) receiving the optical waveguide bundles (5,5') extends in the exit of the sensor head (3) at an angle of 30.degree. and the lower surface (13) of the crystal window (7) extends parallel to the floor (2).

Abstract: A cryosonde for a logging tool wherein the refrigerant chamber for cooling the germanium crystal detector has an easily replaceable rupture means which will fail before the chamber, itself, will rupture.

Abstract: In a preferred embodiment of the new and improved well tool that is described herein, a set of alternate outer tool housings are respectively arranged for carrying a common inner assembly having one or more temperature-sensitive devices. The new and improved set of alternative housings includes a first tubular housing having a solid wall of a steel of sufficient strength and thickness to withstand a predetermined pressure and a second tubular housing having inner and outer tubular members coaxially arranged to provide a hollow wall having substantially equal external and internal diameters as the first housing and which is formed of a steel of sufficiently greater strength than the steel in the first housing so that the second housing will have a design pressure rating about equal to the predetermined pressure.

Abstract: A generalized computer-based system and method for acquisition of nuclear well logging data, including downhole generation of energy and time spectral information. A downhole instrument traverses a borehole introducing high energy neutrons into the formation at prescribed depths. Resultant gamma rays are detected and converted into pulses which are amplified and conditioned.A downhole multi-parameter analyzer stores pulse height and arrival time for each detected gamma ray whereby time and energy spectra are formed. Spectra include, alone or in combination, time spectra of the neutron source, inelastic and capture energy spectra. From the source time spectra, peaks are detected and capture and inelastic gates referenced thereto. Also thermal neutron decay between source bursts is derived. From the energy spectra peaks including hydrogen or iron are detected and used for calibration and automatic gain control of the gamma ray detector.

Abstract: A method and apparatus for improving the operation of a gamma camera which employs a planar scintillation crystal having a circumferential edge in the form of a mechanism and related method for cooling the crystal by thermally coupling the circumferential edge of the crystal to a heat sink and a mechanism and related method for applying pressure to the circumferential edge of the crystal sufficient to maintain the crystal in compression when cooled and thereby avoid cracking of the crystal due to temperature differentiation across the surface of the crystal.

Abstract: A method of measuring earth formation characteristics using a pulsed neutron source computes the characteristics by using a cumulative count curve. A pulsed neutron source and detector are pulled upwardly through a borehole. The pulsed neutron source repetitively irradiates the earth formations with pulses of fast neutrons from the neutron source, creating thermal neutrons due to collisions in the formations. Detectors in the downhole instrument detect gamma rays emanating from the irradiated formations as a result of the capture of thermal neutrons. The gamma rays are cumulatively counted in a plurality of separate time bins between each of neutron pulses. The cumulative counts define points on a cumulative count versus time curve which has a mathematical expression. Count data is transmitted to a surface panel, which uses iterative least squares fit techniques to calculate the formation lifetime decay constant.

Abstract: A logging device is disclosed for utilization in the detection of low energy photons. The logging device includes a sonde suitable for insertion into a wellbore. An insulating storage vessel is disposed within the sonde and serves to insulate a photon detection device and its associated electronic circuitry. The insulating storage vessel is constructed utilizing an inner and outer cylindrical shell. Each shell is constructed utilizing a low thermal conductive metallic material such as stainless steel or titanium and each shell includes at least a portion constructed utilizing a low density material having a high photon transmission property wherein low energy photons may be detected by the photon detection device within the insulating storage vessel. In a preferred embodiment of the present invention, an aperture is provided in the sonde which includes a plug of low density, low atomic number material wherein low energy photons may penetrate the sonde.

Abstract: A generalized computer-based system and method for acquisition of nuclear well logging data. A feature of the present invention is the ability to provide time distribution spectra over the entire interval between source firings, such spectra including the gamma radiation produced from both the inelastic scattering and capture of neutrons from said neutron source. The spectra so generated may be analyzed and processed to derive parameters indicative of formation and borehole conditions, for example, a parameter sensitive to borehole geometry and a parameter sensitive to porosity. Certain parameters may be compared as an indication of the presence of gas in a fluid filled formation. Still further, a quantitative measure of the repeatability of the macroscopic thermal neutron absorption capture cross-section may be derived and used to control the weight of the capture cross-section filter.

Abstract: A generalized computer-based system and method for acquisition of nuclear well logging data. A feature of the present invention is the ability to provide time distribution spectra over the entire interval between source firings, such spectra including the gamma radiation produced from both the inelastic scattering and capture of neutrons from said neutron source. The spectra so generated may be analyzed and processed to derive parameters indicative of formation and borehole conditions, for example, a parameter sensitive to borehole geometry and a parameter sensitive to porosity. Certain parameters may be compared as an indication of the presence of gas in a fluid filled formation. Still further, a quantitative measure of the repeatability of the macroscopic thermal neutron absorption capture cross-section may be derived and used to control the weight of the capture cross-section filter.

Abstract: A gamma ray detector for borehole logging includes a bismuth germanate crystal having a sensitivity to gamma rays and giving off light energy proportional to the energy of detected gamma rays. The bismuth germanate crystal is mounted in a housing which allows the operating temperature of the crystal to be maintained under increasing borehole temperature with depth.

Abstract: For use in a nuclear well logging tool, detector pulse simulator circuits in the preferred and illustrated embodiments are set forth. The simulator circuit is adapted to be placed in a sonde for connection with a well logging tool to provide simulated detector pulses. It is selectively switched on to the output a calibrated pulse sequence function through a number of different levels. It incorporates a circuit means forming pulses limited in amplitude by an envelope yielding pulses of differing amplitude in progression. The circuit is stepped repetitively through its range of operation, for example, from a minimum voltage peak to some specified maximum and then recycles.

Abstract: A temperature stabilization system for a radiation detector in a well logging tool includes a temperature sensor which senses the temperature and provides a corresponding signal. Apparatus located within the logging tool and containing the radiation detector provides a controllable temperature environment for the radiation detector. A heat exchanger transfers heat from the apparatus in accordance with the temperature signal so as to stabilize the temperature in the apparatus for the radiation detector. A heat disposing device is arranged with the heat exchanger to dispose of the transferred heat.

Abstract: A device for providing both thermal protection and radiation shielding for components within a well logging instrument. A thermally insulative flash contains a mass of eutectic material which undergoes a change of state at a temperature which will provide an acceptable thermal environment for such components for extended time periods. The eutectic material has a density facilitating its use as a radiation shield and is distributed around the component so as to selectively impede the impinging of the component by radiation.