Abstract: A system for determining depth profiles of concentrations of hazardous elements in soils comprises a neutron source for generating neutrons of a first energy level and irradiating a volume of soil with the neutrons. Nuclear reactions are effected within the soil and gamma radiation is emitted from the soil. The system also includes an array of gamma detectors for detecting gamma radiation emitted from the soil; source electronics for controlling the width of regularly repeated pulses of neutrons generated by the neutron source; detector electronics associated with the gamma detectors for amplifying and digitalizing signals generated by the gamma detectors and storing data representing the digitalized signals; spectral analysis software for analyzing the data and determining the concentrations of selected target elements in the soil; and an acquisition interface module (AIM).

Abstract: The concentrations of residual heavy metal contaminants in the particulate material in a slurry produced in a particulate material washing process are monitored on-line and can be used to control the washing process. In alternative embodiments of the invention, x-rays, thermal neutrons or laser beams are directed at the slurry as it flows through a flow cell to induce emission of secondary x-rays, gamma rays or light, respectively, characteristic of the heavy metal contaminants and constituents representative of the solids contents of the slurry. These characteristic energies are measured and used to determine the concentration in ppm of the residual heavy metal contaminants in the particulate material within the slurry.

Abstract: Processes for producing stable, radiation hard, highly conductive polymers by a combination of chemical doping and ion irradiation and microelectronics are described. The highly conductive polymers formed by these processes may contain regions of different kinds of conductivity on the same polymer. Resist coatings and masks are used in conjunction with chemical doping and ion irradiation to create specific predetermined n and p conductivity patterns and insulation areas on polymeric films of selected thicknesses for electronic circuitry applications. The resulting circuitry, besides having a conductivity approaching that of metal, is extremely light in weight, flexible, and conductively stable. Several different configurations of microelectronic junction devices fabricated from single type or multiple type conductivity polymer films used either alone or with a polymer of opposite conductivity and a suitable metal or metals are disclosed.

Abstract: The concentrations of residual heavy metal contaminants in the particulate material in a slurry produced in a particulate material washing process are monitored on-line and can be used to control the washing process. In alternative embodiments of the invention, x-rays, thermal neutrons or laser beams are directed at the slurry as it flows through a flow cell to induce emission of secondary x-rays, gamma rays or light, respectively, characteristic of the heavy metal contaminants and constituents representative of the solids contents of the slurry. These characteristic energies are measured and used to determine the concentration in ppm of the residual heavy metal contaminants in the particulate material within the slurry.

Abstract: High resolution scintillation counters comprise a flat-faced photomultiplier tube 10 optically coupled to a long scintillator rod 30 having reduced internal light reflectance 45 and a medium 55 between the photomultiplier tube and the scintillator, said medium having both an index of refraction less than that of the scintillator and the capacity to attenuate light traveling from the scintillator to the photomultiplier on the basis of the light's point of origin within the scintillator. In preferred embodiments, the medium comprises air. The scintillation counters disclosed are useful in the detection of electromagnetic radiation, especially gamma rays.

Abstract: Disclosed is a method and apparatus for measuring the burnup of nuclear fuel. A curve giving the calculated relationship between the fast neutron emission rate and the burnup of fuel is prepared. The fast neutron counting rate from a sample of nuclear fuel of known burnup is measured and the proportionality ratio between that measurement and the fast neutron emission given by the curve for the same burnup is determined. The fast neutron counting rate of nuclear fuel of unknown burnup is then measured and multiplied by the proportionality ratio to determine the fast neutron emission rate, from which the unknown burnup is then determined by means of the curve.

Abstract: A neutron dosimeter and a method for neutron dosimetry involving a two-layer structure, one layer being a fissile material, and the other being a material which changes its conductivity in accordance with a density of implanted ions. Neutrons striking the fissile material result in the production of energetic ions, a determinable number of which implant themselves in the second layer and so alter its conductivity. Measurements of the conductivity of the second layer provide information from which neutron dose may be inferred.

Abstract: A method and apparatus for measuring a neutron flux in which the neutrons induce fission reactions in the layer of fissile material, the fission reactions in turn inducing light pulses in a scintillator material. A photomultiplier tube detects the light pulses and emits an electrical pulse in response. The electrical pulses are summed, checked for coincidence, stored, and otherwise manipulated in order to detect and measure neutron flux. In one advantageous embodiment of the invention, several different fissile materials or coated and uncoated fissile materials are used in order to obtain a spectral distribution of the incident neutron flux. At another embodiment, opposed detectors are used in order to discriminate between actual neutron-induced fission events and background events.

Abstract: A method of lithographically forming a pattern on a surface is disclosed. The surface on which the pattern is to be formed is first coated with a resist layer. A mask preferably consisting of a beryllium of foil and a pattern gold layer affixed thereto is then positioned in overlying relationship to the resist layer. The thickness of the beryllium foil is selected such that it is transparent to high energy particles of a preselected energy while the combination of the pattern gold areas and the beryllium foil is impervious to these particles. A flood beam of high energy particles is directed such that it impinges on the beryllium foil thereby exposing the resist in areas not protected by the combination of the beryllium foil and the gold. The resist layer is processed to produce a patterned layer.

Abstract: A method for eliminating the latch-up effect in integrated circuits having parasitic pnpn structures has been described comprising the step of irradiating the circuit with high energy particulate ions to provide low lifetime regions in the circuit to lower parasitic transistor gain.The invention overcomes the problem of latch-up effect in integrated circuits where parasitic pnpn structures act as thyristors or silicon-controlled rectifiers which provide a low impedance path across the pnpn structure when the thyristor or silicon-controlled rectifier is turned on such as by transient ionizing radiation or by transient circuit voltages which forward bias the external junctions of the pnpn structure.

Abstract: A method of reducing the reverse recovery charge of thyristors without substantially increasing forward voltage drop by first determining the depth of the anode PN junction from a major surface adjoining a cathode emitter region. The depth of maximum defect generation in thyristor on irradiation through the major surface with a given radiation source radiating particles with molecular weight greater than one, preferably proton or alpha particles, and adjusting the energy level at the major surface of the thyristor from the radiation source to provide the depth of maximum defect generation adjacent the anode PN junction and preferably in the anode base region within 20 micrometers of the anode PN junction or in the anode emitter region within 15 micrometers of the anode PN junction.

Abstract: A method for making a pnpn semiconductor reverse conducting thyristor comprises the steps of forming n-type semiconductor layers on both sides of a p-type semiconductor substrate for forming an n-type emitter layer and an n-type anode-base layer. A p-type semiconductor impurity region is formed in the n-type anode-base layer for forming a p-type anode layer. A p.sup.+ -type semiconductor layer is ion implanted in the p-type substrate adjacent to the n-type cathode emitter layer by irradiating it with boron atoms.

Abstract: Irradiated regions are formed in materials such as semiconductor bodies by nuclear radiation where the irradiated regions are of a desired thickness, dosage and dosage gradient, a desired distance from a selected surface of the material. A nuclear radiation beam from a given radiation source radiating particles with molecular weight of at least one (1) is provided that can penetrate the material through a selected surface to a depth greater than the maximum depth of the irradiated region from the selected surface. A beam modifier is formed of a given material and non-uniform shape to modify the energy of the radiation beam on transmission therethrough to form a transmitted radiation beam capable of forming an irradiated region of a desired thickness and dosage gradient in the material a given distance from the selected surface on irradiation of the material through the selected surface with the transmitted radiation beam.

Abstract: The switching time of certain semiconductor devices is decreased while maintaining other electrical characteristics of the devices by irradiating them with a neutron radiation source of greater than 1.0 Mev. to a dosage between 1.times.10.sup.11 and 1.times.10.sup.15 neutrons per square centimeter. The irradiation is preferably to a dosage between 1.times.10.sup.1 and 1.times.10.sup.14 neutrons per square centimeter and preferably has substantial energy greater than 14 Mev. The devices are also annealed during and/or subsequent to the irradiation at a temperature higher than the highest specified temperature and preferably at least 50.degree. C. higher than the highest specified temperature.

Abstract: The turn-off time of a reverse blocking diode thyristor is decreased without significantly effecting other electrical characteristics by irradiating with a radiation source to a dosage corresponding to between about 4 .times. 10.sup.13 and about 2 .times. 10.sup.14 electrons/cm.sup.2 and preferably to between about 6 .times. 10.sup.13 and about 2 .times. 10.sup.14 electrons/cm.sup.2 with 2 MeV electron radiation source. Preferably the radiation source is electron radiation with an energy greater than 1 MeV.

Abstract: The recovery charge of power diodes and thyristors is tailored and matched by irradiation through a major surface of the semiconductor body with a given radiation source, preferably of electron radiation, to a dosage corresponding to between about 1 .times. 10.sup.12 and 8 .times. 10.sup.12 electrons per centimeter square with 2 MeV electron radiation. Preferably, the recovery charge of each device of a group of a type of diode or thyristor is first measured, and the group divided into subgroups according to the measured recovery charge of each device. The devices of at least one subgroup is then irradiated with said given radiation source to dosages corresponding to between about 1 .times. 10.sup.12 and 8 .times. 10.sup.12 electrons per centimeter square with 2 MeV electron radiation, and the recovery charge of each irradiated device is again measured to determine the incremental change of recovery charge as a function of irradiation dosage.

Abstract: A method of reducing the switching time of certain semiconductor devices and particularly gain-operated semiconductor devices. The depth of maximum defect generation in a given type of semiconductor devices having a block PN junction is determined on irradiation with a given radiation source emitting particles with molecular weight of at least one (1), preferably protons or alpha particles; and the energy level of the radiation source adjusted to provide the depth of maximum defect generation adjacent a blocking PN junction of the type of semiconductor device. At least one semiconductor device of said given type of semiconductor device is positioned with a major surface thereof to be exposed to the adjusted radiation source, and thereafter irradiated with the adjusted radiation source to a given dosage level to reduce the switching time of the semiconductor device.

Abstract: The concentration of uranium in a moving stream is determined by agglomerating background microbubbles out of the 6 to 10 micron size range, counting microbubbles in the stream which are about 6 to about 10 microns in size, exposing the stream to a radiation source to cause uranium fission fragments to produce microbubbles, countng microbubbles which are about 6 to about 10 microns in size, and subtracting one count from the other and multiplying by a calibration constant. The subtraction can be performed on an earlier first count so that both counts are made on the same volume. The radiation exposure can be automatically increased when the difference between the first and second counts is low.

Abstract: Diodes of a particular type are fine tuned with irradiation to optimize the reverse recovery time while minimizing forward voltage drop and providing more uniform electrical characteristics. The initial and desired minority carrier lifetimes in the anode region of the type are determined as a function of forward voltage drop and reverse recovery time, and the minority carrier radiation damage factor is determined for a desired type of diode and radiation source. The radiation dosage to achieve the desired carrier lifetime with the radiation source is thereafter determined from the function 1/.tau. = 1/.tau..sub.o + K.phi., where .tau. is the desired minority carrier lifetime, .tau..sub.o is the initial minority carrier lifetime, K is the determined minority carrier radiation damage factor and .phi. is the radiation dosage. A major surface and preferably the major surface adjoining the anode region of the diodes is then irradiated with the radiation source to the determined radiation dosage.