Abstract: A multistage process for the separation and purification of a desired crystalline material by repeated dissolution and recrystallization, wherein crystals and solvent move countercurrent to one another through the stages. A fluid temperature gradient is maintained within each recrystallization unit to make use of convection to facilitate or accelerate concurrent dissolution and recrystallization within a single vessel. Solid recrystallized material is moved from one unit to the next unit. An automated apparatus and a manually operated apparatus for carrying out the process are also described.

Abstract: A multistage process for the separation and purification of a desired crystalline material by repeated dissolution and recrystallization, wherein crystals and solvent move countercurrent to one another through the stages. A fluid temperature gradient is maintained within each recrystallization unit to make use of convection to facilitate or accelerate concurrent dissolution and recrystallization within a single vessel. Solid recrystallized material is moved from one unit to the next unit. An automated apparatus and a manually operated apparatus for carrying out the process are also described.

Abstract: A skin equivalent structure is formed from an aluminized polyester window and a scintillator. The scintillator is chosen to scintillate at a wavelength different from that of most Cerenkov light. The scintillator light travels through a light pipe and one or more filters to a photomultiplier tube. Beta particles reaching the scintillator provide light that results in an electrical output from the tube that corresponds to the skin beta dose rate. The filters are chosen to remove the Cerenkov light. In addition, the light pipe may also be chosen to attenuate the Cerenkov light.

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: An ion chamber type instrument for measuring radioactivity includes a high gain operational amplifier having a feedback network of range determining resistors connected between the amplifier output and input. Electronic switches in series with at least some of the range determining resistors function as range selector switches for the measuring instrument. Each switch includes two series-connected transistors and a third transistor, the interconnection point between the two series-connected transistors being connected to the electrical neutral point of a measuring circuit via the third transistor. Each switch, when in an "off" or non-conducting condition, provides a high effective resistance of, for example, 1.times.10.sup.15 ohms so as to minimize errors caused by leakage current fed back into the input of the high gain operational amplifier.

Abstract: A well logging detector includes an elongated scintillation crystal having one end biased against and optically coupled to a transparent window portion of the detector housing. The biasing force on the crystal is provided by a compression spring located at and bearing against the other end of the crystal. The biasing force applied to the crystal by the spring is weak enough to allow the crystal to move away from and optically decouple from the window portion in response to shock forces on the detector. Subsequent to such shock induced decoupling, the biasing spring moves the crystal against the window portion to re-establish optical coupling therebetween. Such a biasing structure precludes excessive axial loading of the crystal by shock forces tending to move the crystal against the window as opposed to away from it. Such a shock resistant detector is especially well suited to measurement-while-drilling (MWD) applications.

Abstract: A plastic scintillator element that is tissue equivalent is optically coupled to a photomultiplier tube that provides a pulse signal which contains information relating to radiation energy fluence, and having an undesirable "dark current" component. A direct current blocking element in the form of a capacitor isolates the input of an operational amplifier from the "dark current" component so that the output signal of the amplifier indicates the average current of the photomultiplier signal attributed only to detected, low level, environmental radiation in the range of 0-200 .mu.rem/h.

Abstract: A high-temperature well logging instrument of the scintillation detector type includes a plastic scintillation element susceptible to softening and deformation at high operating temperatures. To maintain the shape of the scintillation element at such high temperatures, a metal retaining cup holds the scintillation element in its original shape. The retaining cup with the scintillation element inside is capped at its open end by a silicon rubber pad that is transparent to photons generated by the scintillation element in response to detected radiation. A biasing spring holds the end face of a photomultiplier tube against the silicon rubber pad so as to sandwich the pad between the photomultiplier tube and the open end of the metal retaining cup. Such a configuration maintains excellent optical coupling between the scintillation element and photomultiplier tube during high-temperature well logging.

Abstract: A scintillation detector is provided which has a scintillation member comprised of a substance which converts energy received in the form of an ionizing particle to light. The scintillation member, such as a thallium-activated alkali halide crystal, is sealed in a housing containing an atmosphere which is substantially non-reactive to the scintillation member at temperatures ranging from about 100.degree. C. to about 250.degree. C. Examples of suitable atmospheres include the noble gases including helium, neon argon, krypton, xenon and radon; nitrogen; carbon dioxide, a vacuum, and other atmospheres, such as mixtures of these or air which has been substantially depleted of oxygen. Processes for the manufacture of the detector are taught where the scintillation member is encapsulated in a non-reactive atmosphere such as ones listed above. Alternatively, the reactive atmosphere can be washed from the housing or the sealed housing can be evacuated and refilled with a non-reactive atmosphere.

Abstract: A Geiger-Mueller tube-based radiation measurement device includes circuitry for the correction of the dead time losses associated with the Geiger-Mueller tube. As the event count rate rises, the transfer function (e.g., the closed loop voltage gain) of an operational amplifier responding to an event count rate signal is modified to compensate for dead time losses experienced at high count rates. Preferably, an analog switch controlled by the event count rate signal automatically sets the voltage gain of the operational amplifier at a level corresponding to the desired amount of dead time compensation required to provide an accurate measurement of actual events. The dead time correction circuitry disclosed herein finds practical application in the use of well-known analog rate meter circuits of the charge pump type.

Abstract: A solution of a hydrophobic substituted, amino triphenyl methane leucocyanide dye in a clear, highly polar solvent free of hydroxyl groups with enough acid added to make the solution slightly acidic which is sensitive to small dosages of ionizing radiation and responds by permanently changing color. Up to one-half of the solution by weight can be replaced by a second solution of an aromatic solvent and an organic fluor. Another modification of the invention is a solution of a leucocyanide dye in a clear polar solvent which has an aromatic group, an organic fluor, and enough acid to make the solution slightly acidic.

Abstract: An encapsulated scintillation detector is disclosed in which a detector crystal or the like is encapsulated in a hermetically sealed housing having a light-transmitting window at one end. In some instances, the window is mounted in a window assembly by a compression seal established by the differential coefficient of expansion and contraction during the cooling of the assembly. In other instances, the window is chemically bonded to the ring with or without a compression seal. The window is mounted within a ring, which is in turn welded to the end of a tubular body portion of the housing along thin weld flanges to reduce the amount of weld heat which must be applied. A thermal barrier is provided to resist the flow of welding heat from the weld to the seal between the ring and the window. Such thermal barrier includes a zone of relatively thin section located between the weld zone and the seal through which weld heat must flow.

Abstract: A circular glass window in the form of a shallow, truncated cone having parallel faces is nested within and equidistantly spaced from a metal retaining ring defining at its inner periphery a shallow, tapered, smooth-wall bore having a sloped sidewall to which the correspondingly sloped edge of the glass window is bonded by a thin layer of epoxy adhesive composition constituting an annular hermetic seal of constant predetermined thickness for optimum strength. The retaining ring, with the glass window mounted therein, is welded to the end of a tubelike metal housing containing a cylindrical scintillation crystal coaxially mounted therein, the larger diameter base end or inner face of the truncated, cone-shaped window being optically coupled to and adjacent one end of the crystal. The crystal is biased toward the inner face of the window to apply an evenly distributed compression force to the annular epoxy-formed seal to aid in maintaining its hermetic integrity under adverse temperature conditions.

Abstract: A unique scintillation detector unit is disclosed which employs a special light transfer and reflector means that encases and protects the scintillator crystal against high g forces. The light transfer means commprises a flexible silicone rubber optical material bonded between the crystal and the optical window and having an axial thickness sufficient to allow the scintillator to move axially inside the container under high g forces without destroying the bonds. The reflector means comprises a soft elastic silicone rubber sleeve having a multiplicity of closely arranged tapered protrusions radiating toward and engaging the periphery of the scintillator crystal to cushion shocks effectively and having a reflective material, such as aluminum oxide powder, in the spaces between the protrusions. The reflector means provides improved shock absorption because of the uniform support and cushioning action of the protrusions and also provides the detector with high efficiency.

Abstract: A scintillation counter consists of a scintillation detector, usually a crystal scintillator optically coupled to a photomultiplier tube which converts photons to electrical pulses. The photomultiplier pulses are measured to provide information on impinging radiation. In inorganic crystal scintillation detectors to achieve maximum density, optical transparency and uniform activation, it has been necessary heretofore to prepare the scintillator as a single crystal. Crystal pieces fail to give a single composite response. Means are provided herein for obtaining such a response with crystal pieces, such means comprising the combination of crystal pieces and liquid or solid organic scintillator matrices having a cyclic molecular structure favorable to fluorescence.