Abstract: A system for detecting and imaging gamma radiation emitted by a contaminated area includes a plurality of collimators spaced a distance apart from each other. The collimators have a plurality of holes therethrough and the holes of one collimator are aligned with the holes in another collimator for forming a plurality of hole alignments which permit gamma rays to pass through the collimators. A scintillator and operatively connected avalanche photodiode are provided with each aligned hole of the collimators for determining the position of the gamma ray which passes through the collimators. A video camera records a visual image of the contaminated area and a monitor displays the video image along with location and size information provided by the avalanche photodiodes.

Abstract: A flexible, pressurized insert for insertion within the hot (evaporator) side of an inclined heat pipe that forms a part of a heat pipe heat exchanger. This insert is employed in order to prevent such heat pipe from rupturing in the event the working fluid contained therein freezes. This insert is constructed of a thin-walled flexible material that is capable of being deformed (i.e. compressed) thereby absorbing the expansion pressures exerted by the working fluid should the working fluid freeze or be exposed to freezing temperatures. By such absorption, the outer heat pipe itself will not be over-pressurized which might otherwise lead to its rupture. Upon the thawing of the working fluid, the pressurized insert (which is at a pressure greater than that of the working fluid in its non-frozen state) will once again regain its shape.

Abstract: An apparatus and method for pacing the application of a manual weld along the weld line generates beeps or light flashes at a rate which can be correlated by the welder with markings along the weld line. As each beep or flash is perceived, the welder should reach the next marking. Spacing between the markings determines the desired rate at which the weld is being applied. Alternatively, sequentially lightable areas are distributed along the weld line and sequentially lit a desired rate. The welder chases the sequence along the weld line to achieve the optimum rate of welding.

Abstract: A method for achieving thermal compensation of a microbend sensor used in a fiber optic system and exposed to a thermal environment comprises providing a length of optical fiber and a light source at the optical fiber for passing light through the fiber. A detector is provided at the optical fiber for detecting the light passed through the fiber. A section of the fiber is split for establishing an active leg and a reference leg. An active microbend sensor is provided on the active leg in a thermal environment for producing an active signal; and a reference microbend sensor is provided on the reference leg in the thermal environment near the active sensor for producing a reference signal. The active signal and the reference signal are then detected and a compensation for the active sensor is determined based on the active signal and the reference signal.

Abstract: A differential pressure transducer cell comprises a housing and a pair of spaced diaphragms connected at one end to one portion of the housing and connected at an opposite end to a second portion of the housing. The diaphragms have an outer surface and an inner surface; and the outer surface of each diaphragm is exposed to a pressure. A beam is connected between the diaphragms at the inner surface of the diaphragms. Sensors are also provided on the beam.

Abstract: Scintillating optical fiber is used in a probe for detecting radiation. The scintillating optical fiber is fused to an extension fiber leading to optoelectronics such as p-intrinsic n-photodiodes or avalanche photodiodes. The fibers are housed in a durable probe body for penetration into the ground. When radiation is present, dopants in the scintillating fiber emit visible light through the extension fiber to the optoelectronics. Amplifiers are provided for monitoring the light intensity transmitted along the fibers and for triggering an alarm circuit signaling the presence of radiation at the probe.

Abstract: A single optical fiber is used for measuring angular or rotational position in a rotary sensor. The optical fiber is used in connection with known analog intensity opto-electronics. The optical fiber is used in connection with a microbending device housed within the sensor. An input shaft of the sensor experiencing rotational motion causing the microbending device to subject the optical fiber to microbending. Microbending can be caused by a crankpin, pins located on the shaft within the housing, a transverse hole located through the shaft, or other loading arrangement. A micrometer lead screw can be used within the housing to convert the rotational motion into linear motion. The converted linear displacement is used to compress the optical fiber. Where the input shaft experiences many rotations or multiple turns the linear displacement can be applied to a spring element for carrying a load or force to a compression device.

Abstract: A sensor comprises an optical sensor fiber which has a microbend module engaged thereto. When the module is subjected to external influences such as pressure, displacement or the like, it places microbends in the sensor fiber which changes a light transmission characteristic of the fiber. Light passing through the sensor fiber is detected, and changes in the light are measured to find the influence on the modulator. A scintillating or florescent source fiber connected to one end of the sensor fiber is exposed to radiant energy. This produces light which is channeled to the sensor fiber as the light source for the sensor fiber.

Abstract: A fiber optic loop temperature sensor employs a fiber optic loop (90) having a predetermined fixed radius where a light source (96) supplies light to the signal optical fiber (92) with the loop and a second reference optical fiber (100) receives light from the light source (96) for providing a reference light intensity. The light intensities from both optical fibers are measured and the temperature is determined from differences therein. Advantageously, the fiber optic loop temperature sensor is employed in a temperature compensated, self-referenced fiber optic microbend pressure transducer to compensate for thermal offset of the microbend sensor output. In the preferred embodiment, time division multiplexing provides at least two bi-cell photodetectors (82) with output and source signals for generating a log ratio output for determining the sensed parameter independent of cable and connector offsets and light source fluctuations in addition to compensation for thermal offset.

Abstract: A temperature compensated, self-referenced fiber optic microbend pressure transducer employs a fiber optic loop (90) to compensate for thermal offset of the microbend sensor output. In the preferred embThis invention was made with Government support under Contract No. NAS3-25796 awarded by the National Aeronautics and Space Administration. The Government has certain rights in this invention.

Abstract: A method for manufacturing a sensor with an attached leadwire (10) fastened to an adaptor block (18) which is attached to a gage shim (24). The sensor is deposited on an insulated layer (28) placed on the gage shim (24) in electrical contact with the electrical leads (16) of the leadwire (10). One or more passivation layers (36) are applied over the upper surface of the entire sensor to provide a complete seal.

Abstract: A microbend strain gauge comprises a pair of plates having facing offset corrugations which clamp a signal optical fiber therebetween. The optical fiber is coated and a light signal is supplied to one end of the fiber which is read at an opposite end of the fiber by an optical sensor. Modulations in the light are primarily due to a difference in pressure being applied to the fiber by the plates. A second optical fiber, is subjected to the same thermal condition and its light signal compared to the light signal through the signal optical fiber to offset any temperature error introduced into the signal by changes in temperature. Aluminum, polyimide or gold coating increases temperature resistance for the fibers.

Abstract: A fiber optic microbend sensor with a braided arrangement of multiple optical fibers (or fibers and fillers) 16 such that the length dependent microbending losses result from the interaction of the fibers 10 themselves (or the fibers and fillers) without the need for additional external structures such as corrugated plates 12, 14. A plurality of fibers with at least one of the fibers being an optical fiber 10 are braided together into an interwoven strand 16 to produce the fiber optic microbend sensor. The spatial bend frequency of the braid 16 corresponds to the optimum microbend frequency for the fiber 10.

Abstract: A tubular apparatus is assembled of inner and outer tubes which are connected at spaced locations along their length. After heat treatment and other processing steps, either the inner or outer tube is heated to reduce its yield strength and then stretched beyond its yield point but not beyond the yield point of the other tubular. The heat source is removed so that the stretched state is maintained. The tubular apparatus is thus prestressed with the inner tube under compressive prestressing when the inner tube has been heated and stretched, and the inner tube under tensile prestressing when the outer tube has been heated and stretched.

Abstract: An instrumentation installation tool (30) for weldably attaching strain gages (20) or other instrumentation to the interior of a steam generator tube (42). The exterior surface of the section (32) is formed with four longitudinal grooves (32A, 36B, 36C and 38). A welding slot (44) is situated in one of the grooves (38). A ramp (46), oriented within the section (32) is in close proximity to the slot (44). Additionally, an elongated multitipped electrode (80) is slidably and coaxially disposed within the section (32).