Abstract: A light sensor and its calibration method are provided. The light sensor includes a light source, a sensing sub-pixel, and a control circuit. The light source emits a sensing light beam. The sensing sub-pixel includes a diode, a quenching resistor, and a time-to-digital converter. The diode has a first terminal coupled to an operation voltage. The quenching resistor is coupled between a second terminal of the diode and a ground voltage. The time-to-digital converter is coupled to the second terminal of the diode. The control circuit is coupled to the sensing sub-pixel and calibrates a sensing sensitivity of the sensing sub-pixel according to at least one of a photon detection probability, an internal gain value, and a resistance value of the quenching resistor corresponding to the diode of the sensing sub-pixel, so that the sensing sub-pixel generates a single-photon avalanche diode sensing signal only when receiving the sensing light beam.

Abstract: An improved support apparatus is structured to support a dosimetry system within an interior region of a containment apparatus. The dosimetry system is supported in a region between an interior surface of the containment apparatus and an exterior surface of a reactor apparatus that is disposed within the interior of the containment apparatus. The support apparatus includes a retention apparatus having a plurality of brace elements that each have a receptacle formed therein. The receptacles are aligned with one another when installed within the interior of the containment apparatus. The support apparatus further includes a tube apparatus that includes a plurality of tube segments that are connectable together. The dosimetry system is situated within an elongated cavity formed in the tube apparatus. The tube apparatus is situated in the receptacles and thereby supports the dosimetry system on the containment apparatus.

Abstract: The present specification discloses methods for inspecting an object. The method includes scanning an object in a two-step process. In the primary scan, a truck or cargo container (container) is completely scanned with a fan beam radiation, the transmitted radiation is measured with an array of detectors, and the transmission information and optionally the fission signatures are analyzed to determine the presence of high-density, high-Z and fissionable materials. If the container alarms in one or more areas, the areas are subjected to a secondary scan. This is done by precisely repositioning the container to the location of the suspect areas, adjusting the scanning system to focus on the suspect areas, performing a stationary irradiation of the areas, and analyzing the measured feature signatures to clear or confirm the presence of SNM.

Abstract: In accordance with embodiments of the invention, at least the potential presence of Special Nuclear Material (“SNM”) is determined by the detection of prompt neutrons, prompt gamma rays, delayed neutrons, and/or delayed gamma rays from photofission, via time-of-flight (“TOF”) spectroscopic methods. Methods and systems are disclosed.

Abstract: Methods and systems for non-intrusively detecting the existence of fissile materials in a container via the measurement of energetic prompt neutrons are disclosed. The methods and systems use the unique nature of the prompt neutron energy spectrum from photo-fission arising from the emission of neutrons from almost fully accelerated fragments to unambiguously identify fissile material. The angular distribution of the prompt neutrons from photo-fission and the energy distribution correlated to neutron angle relative to the photon beam are used to distinguish odd-even from even-even nuclei undergoing photo-fission. The independence of the neutron yield curve (yield as a function of electron beam energy or photon energy) on neutron energy also is also used to distinguish photo-fission from other processes such as (?, n). Different beam geometries are used to detect localized samples of fissile material and also fissile materials dispersed as small fragments or thin sheets over broad regions.

Abstract: A method for detecting nuclear material in an object analysed by neutron interrogation with an associated particle tube, where the method includes steps of detection of coinciding pulses by detector pixels of at least one matrix of detector pixels, where a step of detection of coinciding pulses leads to the formation of an event which reflects a fission reaction which occurs in the nuclear material, where the method includes a search for adjoining pixels amongst the pixels which have detected coinciding pulses, a grouping of adjoining pixels into groups of adjoining pixels, a count of the pixels and/or groups of adjoining pixels which have detected coinciding pulses, and a validation of the occurrence of an event provided at least three pixels and/or groups of adjoining pixels are counted.

Abstract: Methods and systems for non-intrusively detecting the existence of fissile materials in a container via the measurement of energetic prompt neutrons are disclosed. The methods and systems use the unique nature of the prompt neutron energy spectrum from neutron-induced fission arising from the emission of neutrons from almost fully accelerated fragments to unambiguously identify fissile material. These signals from neutron-induced fission are unique and allow the detection of any material in the actinide region of the nuclear periodic table.

Abstract: Embodiments are directed to a digital data acquisition method that collects data regarding nuclear fission at high rates and performs real-time preprocessing of large volumes of data into directly useable forms for use in a system that performs non-destructive assaying of nuclear material and assemblies for mass and multiplication of special nuclear material (SNM). Pulses from a multi-detector array are fed in parallel to individual inputs that are tied to individual bits in a digital word. Data is collected by loading a word at the individual bit level in parallel, to reduce the latency associated with current shift-register systems. The word is read at regular intervals, all bits simultaneously, with no manipulation. The word is passed to a number of storage locations for subsequent processing, thereby removing the front-end problem of pulse pileup. The word is used simultaneously in several internal processing schemes that assemble the data in a number of more directly useable forms.

Abstract: A method for measuring high-energy radiation includes applying a voltage pulse to electrodes in an ion chamber filled with a gas capable of forming charged ions by the high-energy radiation; measuring an ion current signal related to ion currents induced by the voltage pulse; and determining a magnitude of the high-energy radiation based on the ion current signal.

Abstract: The present specification discloses a system for detecting nuclear material based on at least one source of probing radiation and the radiation signatures generated from interrogating an object under inspection. In addition, the present specification describes a threshold-activation detector capable of detecting prompt neutrons, via the activation, after the source's blinding radiation has stopped. The threshold-activation detector can be manufactured from liquid fluorocarbons that allow for the detection of beta radiation and gamma rays.

Abstract: A neutron detection system may include a volume of neutron moderating material, and a plurality of solid state neutron detection devices disposed within the volume of neutron moderating material, wherein some of the neutron detection devices suitable for transduction of primary reaction products resulting from a neutron interaction event, wherein some of the solid state neutron detection devices include two or more solid state neutron detection elements, and wherein the solid state neutron detection elements are configured for omnidirectional detection of impinging neutrons.

Abstract: A neutron detector system for discriminating fissile material from non-fissile material wherein a digital data acquisition unit collects data at high rate, and in real-time processes large volumes of data directly into information that a first responder can use to discriminate materials. The system comprises counting neutrons from the unknown source and detecting excess grouped neutrons to identify fission in the unknown source. The system includes a graphing component that displays the plot of the neutron distribution from the unknown source over a Poisson distribution and a plot of neutrons due to background or environmental sources. The system further includes a known neutron source placed in proximity to the unknown source to actively interrogate the unknown source in order to accentuate differences in neutron emission from the unknown source from Poisson distributions and/or environmental sources.

Abstract: Methods relating to photonuclear detection are disclosed. A method of operating a photonuclear detection system may include transmitting photons toward a container for a duration of a first time period. The method may further include waiting for a duration of a second time period substantially equal to a detector recovery time of a radiation detector proximate the container. Additionally, the method may include measuring for induced delayed signatures for a duration of a third time period.

Abstract: Dual modality detection devices and methods are provided for detecting nuclear material, the devices include a neutron detector including multiple neutron detection modules; and a gamma detector including multiple gamma detection modules, where the multiple neutron detection modules and the multiple gamma detection modules are integrated together in a single unit to detect simultaneously both gamma rays and neutrons.

Abstract: A method and system for detecting special nuclear materials are disclosed. Said method and system detect the special nuclear materials by making use of the photofission characteristic and thermal neutron induced fission characteristic thereof. In one preferred embodiment, the high density and/or high atomic number region in the object to be detected is also detected first as a suspicious region.

Abstract: A system for interrogating a package, container, vehicle, or similar examination article for the presence of nuclear material. The system typically includes a source of photo-fission energy configured to irradiate the examination article and trigger fission of a fissile or a fissionable material present in the examination article and generate a plurality of fission products, wherein at least one of the plurality of fission products produces a plurality of fission neutrons. A neutron-to-gamma-ray-converter material may be configured to capture up to all of the plurality of fission neutrons and upon capture to emit internal gamma radiation. A gamma radiation detector is typically configured to detect at least a portion of the internal gamma radiation.

Abstract: A first pulsed beam of charged particles from a particle accelerator is accelerated toward a first target that is configured to emit a fast neutron beam in response to being struck by an accelerated particle such that the fast neutron beam is directed toward a physical region. The last neutron beam includes a neutron having an energy sufficient to cause fission in a fissionable material. Data from a sensor configured to detect radiation of a fission product is accessed, and before accelerating a second pulsed beam of charged particles, whether the physical region includes a fissionable material based on the data from the sensor is determined.

Abstract: Methods and systems for non-intrusively detecting the existence of fissile materials in a container via the measurement of energetic prompt neutrons are disclosed. The methods and systems use the unique nature of the prompt neutron energy spectrum from neutron-induced fission arising from the emission of neutrons from almost fully accelerated fragments to unambiguously identify fissile material. These signals from neutron-induced fission are unique and allow the detection of any material in the actinide region of the nuclear periodic table.

Abstract: A method and a system for detecting the presence of special nuclear materials in a suspect container. The system and its method include irradiating the suspect container with a beam of neutrons, so as to induce a thermal fission in a portion of the special nuclear materials, detecting the gamma rays that are emitted from the fission products formed by the thermal fission, to produce a detector signal, comparing the detector signal with a threshold value to form a comparison, and detecting the presence of the special nuclear materials using the comparison.

Abstract: A neutron detector utilizing a sol-gel absorber incorporating a fissionable material and an activation disk. Preferably utilizing Li-6 and B-10 as fissionable material and Ag-109 as activation disk material for increased sensitivity and better differentiation of thermal versus prompt neutrons and neutrons versus other radiation fragments.

Abstract: A method and a system for detecting the presence of special nuclear materials in a container. The system and its method include irradiating the container with an energetic beam, so as to induce a fission in the special nuclear materials, detecting the gamma rays that are emitted from the fission products formed by the fission, to produce a detector signal, comparing the detector signal with a threshold value to form a comparison, and detecting the presence of the special nuclear materials using the comparison.

Abstract: The subject apparatus provides a means to identify the presence of fissionable material or other nuclear material contained within an item to be tested. The system employs a portable accelerator to accelerate and direct protons to a fluorine-compound target. The interaction of the protons with the fluorine-compound target produces gamma rays which are directed at the item to be tested. If the item to be tested contains either a fissionable material or other nuclear material the interaction of the gamma rays with the material contained within the test item with result in the production of neutrons. A system of neutron detectors is positioned to intercept any neutrons generated by the test item. The results from the neutron detectors are analyzed to determine the presence of a fissionable material or other nuclear material.

Abstract: The subject apparatus provides a means to identify the presence of fissionable material or other nuclear material contained within an item to be tested. The system employs a portable accelerator to accelerate and direct protons to a fluorine-compound target. The interaction of the protons with the fluorine-compound target produces gamma rays which are directed at the item to be tested. If the item to be tested contains either a fissionable material or other nuclear material the interaction of the gamma rays with the material contained within the test item with result in the production of neutrons. A system of neutron detectors is positioned to intercept any neutrons generated by the test item. The results from the neutron detectors are analyzed to determine the presence of a fissionable material or other nuclear material.

Abstract: Disclosed is a method of monitoring the neutron sensitivity of a neutron detector. Voltage having a predetermined potential difference is applied between an anode and a cathode without irradiating the neutron detector with neutrons to permit an &agr;-ray to be emitted from the nuclear fission substance. The &agr;-ray ionizes the ionizing gas to form an &agr;-ray current (I&agr;) flowing between the anode and the cathode. The current (I&agr;) thus formed is monitored. Also, with the monitoring region in which the applied voltage and the &agr;-ray current (I&agr;) bear a substantially proportional relationship, obtained is an extrapolated zero-volt &agr;-ray current (I&agr;0) at 0V of the applied voltage between the anode and the cathode from the proportional relationship by an extrapolating method, and the extrapolated zero-volt &agr;-ray current (I&agr;0) is correlated with the neutron sensitivity.

Abstract: Disclosed is a method of monitoring the neutron sensitivity of a neutron detector. Voltage having a predetermined potential difference is applied between an anode and a cathode without irradiating the neutron detector with neutrons to permit an &agr;-ray to be emitted from the nuclear fission substance. The &agr;-ray ionizes the ionizing gas to form an &agr;-ray current (I&agr;) flowing between the anode and the cathode. The current (I&agr;) thus formed is monitored. Also, with the monitoring region in which the applied voltage and the &agr;-ray current (I&agr;) bear a substantially proportional relationship, obtained is an extrapolated zero-volt &agr;-ray current (I&agr;0) at 0V of the applied voltage between the anode and the cathode from the proportional relationship by an extrapolating method, and the extrapolated zero-volt &agr;-ray current (I&agr;0) is correlated with the neutron sensitivity.

Abstract: The invention relates a device for measuring the relative proportions of uranium and plutonium in a radioactive package (16), having: a source of photons (10) for irradiating the package, at least one delayed neutron detector (18) able to deliver counting signals for neutrons emitted by the package, means (22, 30) of acquiring counting signals, able to establish a decrease over time in the neutrons emitted, characteristic of the radioactive package, calculation means (32) for comparing the decay characteristic of the radioactive package with the respective characteristic decays of uranium and plutonium and for establishing relative proportions of uranium and plutonium in the package.

Abstract: A neutron detector utilizing a sol-gel absorber incorporating a fissionable material and an activation disk. Preferably utilizing Li-6 and B-10 as fissionable material and Ag-109 as activation disk material for increased sensitivity and better differentiation of thermal versus prompt neutrons and neutrons versus other radiation fragments.

Abstract: This invention relates to a method and apparatus for improving the precision of at least one of neutron coincidence counting and neutron multiplicity counting. The method includes the steps of: (1) sampling the real and accidental coincident pulses at the incoming pulse rate; and (b) sampling the accidental coincidences at a clock rate, wherein the clock rate is much faster than the pulse rate. The clock rate is faster than the pulse rate by a factor of 5 to 10 (in the preferred embodiment, approximately 4 MHz).

Abstract: An improved method and apparatus for the detection of hydrogenated materials. Detection of concealed hydrogenated materials such as organic explosives, drugs, or biological tissue is accomplished by measuring the backscattering of neutrons from hydrogenous material in the targeted environment. The system comprises a neutron source that provides information as to the time at which the neutron is emitted, and a neutron sensor, which provides information as to the time at which the neutron is detected and may provide information as to the location at which the neutron is detected. The invention comprises a timing circuit that deactivates the neutron sensor during a time delay to reject signals from neutrons that have not scattered from hydrogen nuclei. The invention may further cease to detect neutrons after a window to reject signals from neutrons that have scattered off distant hydrogen nuclei, which may represent background noise.

Abstract: A multisensor vehicle-mounted mine detector having one or more sensors leading the vehicle for detecting objects in the ground while moving. A navigational system tracks the coordinates of the detected objects, performs data fusion, declares whether the object is a target worthy of interest and if so, stops the vehicle with a trailing thermal neutron activator sensor (TNA) over the coordinates of the object and interrogating the object with slow neutrons to confirm whether it contains sufficient nitrogen to indeed be a mine. The TNA confirmation is kept brief due to the use of a strong source coupled with means for analysing the resultant pulses and rejecting piled-up pulses. The difference between an integration of the entire pulse and a portion of the pulse is compared against a predetermined difference for a normal pulse wherein variations therebetween are indicative of a piled-up pulse which is then rejected.

Abstract: This neutron detector device includes a containment inside of which there is mounted a detector and which contains a neutral gas. The detector is formed by a fission type chamber comprising a cylindrical-shaped external electrode, coated with a lining of uranium in metal form, enriched as isotope 235, and a cylindrical-shaped internal electrode coaxial to the external electrode. The containment is of annular shape and arranges a cylindrical center space open at both ends to house a moderator to slow down the fast neutrons with great efficiency with respect to detection. The present invention provides an advantage of making it easy to replace the moderator. It is favorable to use cylindrical electrodes of large diameter thus increasing the sensitivity.

Abstract: The present invention is a detector assembly for a nuclear reactor which includes platinum detector segments (30-40) axially distributed end to end within a reactor assembly and vanadium detector segments (42-52) spatially congruent in the same assembly. The vanadium detectors calibrate the platinum detector signals to remove the flux contributions of fission products. A full length vanadium detector (62) and a full length platinum detector (90) can be substituted and used to determine the compensation for the platinum detector segments (30-40). The compensated platinum detector signals, wherein compensation consists of isolating that portion of the total platinum detector signal that is directly proportional to the current local heat deposition rate in the reactor fuel, can be used for reactor core protection purposes.

Abstract: Invention comprises an instrument in which momentum flux onto a biasable target plate is transferred via a suspended quartz tube onto a sensitive force transducer--a capacitance-type pressure gauge. The transducer is protected from thermal damage, arcing and sputtering, and materials used in the target and pendulum are electrically insulating, rigid even at elevated temperatures, and have low thermal conductivity. The instrument enables measurement of small forces (10.sup.-5 to 10.sup.3 N) accompanied by high heat fluxes which are transmitted by energetic particles with 10's of eV of kinetic energy in a intense magnetic field and pulsed plasma environment.

Abstract: A neutron detection device is housed in a metal enclosure containing a first detector with a high-sensitivity fission chamber, and a second detector having a low-sensitivity fission chamber and a boron-lined ionization chamber compensated for gamma radiation. The detection device is useful for extended range measurement of the neutron fluence rate outside the core of a nuclear reactor.

Abstract: The present invention is directed to a nuclide separation precipitator system in which noble gas nuclear fission products are introduced into a gas reservoir and generate charged daughter nuclides in the gas reservoir. A collector collects three detectable charged daughter nuclides. A detector detects the energy distributions of beta-rays and gamma-rays emitted from the daughter nuclides collected in the collector and outputs signals indicative of the detected beta-rays and gamma-rays. Three pulse height discriminators discriminate the signals output from the detector into three respective energy levels of a low energy range, a middle energy range, and a high energy range. A first order simultaneous equation of three unknowns obtained by utilizing a fact that counting ratios of the three energy ranges vary for each daughter nuclide is then solved.

Abstract: An excore neutron flux power level detector assembly includes a neutron flux detector subassembly and a moderator subassembly having the form of a dual-wall canister of annular cross-section for receiving the detector subassembly in coaxial and telescoping relationship therein and having moderator material, preferably high density polyethylene, in the annular space between the dual-walls thereof for converting epithermal neutrons in leakage flux from a nuclear reactor to thermal neutrons having a power level detectable by the flux detector subassembly. Insulating spacer elements affixed concentrically about and axially displaced along the surface of the cylindrical housing of the detector provide lateral, structural support and spacing therebetween and electrical insulation of the detector subassembly from the moderator subassembly.

Abstract: Fission chamber with a wide measuring range and apparatus for measuring the neutron flux density using said fission chamber. The chamber comprises an enclosure (2) filled with a gaseous medium and, in the latter, electrodes (8,10) adjacent the periphery of the enclosure, whereof at least one is covered with a fissile material having a large surface density or mass, as well as other electrodes (10,12) adjacent the center of the enclosure, whereof, at least one is covered with a fissile material having a smaller surface density, chosen so as to optimize (a) the ratio of the electric currents respectively due to the neutrons and to spurious gamma radiation detected by the other electrodes and (b) the linearity of the signal supplied by the latter for a given flux density range.

Abstract: A high-efficiency apparatus for detecting fast neutrons includes an assembly of disks of solid state charged particle detector material, or other appropriate charged particle detecting devices, disposed between adjacent thick (on the order of 1 mm) disks of fissionable material. The fissionable material must be an isotope that has a sharp increase in the neutron-induced fission cross section at a neutron energy of about 100 keV or greater, i.e., a fast neutron. An array of such assemblies housed in a thermal neutron shielding structure provides a threshold detector for fast neutrons resulting from neutron-induced fission of the fissionable material.

Abstract: An improved thermal neutron flux detector and measuring apparatus of the neutron induced transmutation type. The disclosed apparatus employs a plastic film electret and a fissionable material such as uranium-235 for generating energetic ion fission fragments-fragments which alter the electric potential of the electret in a measurable manner. Electret characteristics and fissionable material member fabrication are also disclosed along with uses of the instrument for dosimetry and other purposes.

Abstract: A nuclear excitation laser type intra-reactor neutron flux measuring system of this invention is comprised of a laser oscillator filled with a nuclear exciting gas such as .sup.3 He, KrF or XeF, mounted on the tip of a control rod. The nuclear exciting gas is made into a plasma by the neutrons or the fragments of fissioned nuclei when the tip is positioned in the reactor core by raising the control rod. Since the nuclear exciting gas made into a plasma itself generates a laser beam or amplifies a laser beam projected from the outside, the behavior of neutrons can be monitored in detail after guiding this light response to the light processing system located outside, distinguishing the energies of neutrons from the spectrum and calculating the density and the flux of the neutron in each energy. Furthermore, the detecting sensitivity can be enhanced by forming the responsive membrane made of U.sub.3 O.sub.8 and so on, on the laser oscillator.

Abstract: It comprises an enclosure, a neutron emitting source (29) for bombarding said fissile material, means (28, 30) for introducing source (29) into the enclosure and for removing said source from the enclosure, neutron radiation detection means (9), moderator means (2, 4, 6) for thermalizing a fission radiation emitted by said fissile material interposed between the neutron radiation detection means (9) and the fissile material. It also has gamma radiation detection means (6, 14), which comprises a scintillator (6) and at least one photomultiplier (14) associated with said scintillator (6) and the scintillator material also constituting the moderator for thermalizing the fast neutrons directly emitted by the source (29), as well as the neutrons from the spontaneous fissions of the .alpha., n reaction and the neutrons from the fissions induced in the fissile material, the neutron radiation detectors (9) being embedded in the scintillator material (6) constituting the moderator.

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 monitoring the neutron flux in the core of a nuclear reactor by means of a neutron detector which is composed of two electrodes between which a d.c. bias voltage is applied and which has a greater neutron sensitivity when the d.c. bias voltage is applied with one polarity than with the opposite polarity, which involves operating the nuclear reactor at a power level in the vicinity of zero, and applying a d.c. bias level with the one polarity between the detector electrodes and measuring the neutron-induced current flowing through the detector electrodes.To permit reversal of the bias voltage polarity, a safety interlock is provided to permit this to occur only if the bias voltage has been brought below a selected level.

Abstract: A method for producing ultralow-mass fissionable deposits for nuclear reactor dosimetry is described, including the steps of holding a radioactive parent until the radioactive parent reaches secular equilibrium with a daughter isotope, chemically separating the daughter from the parent, electroplating the daughter on a suitable substrate, and holding the electroplated daughter until the daughter decays to the fissionable deposit.

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 solid state thermal neutron detector. The improved detector for particularly high temperature applications of thermal neutron flux determination, employs a differential thermocouple unit having the hot junction positioned within a cylindrical pellet or compact of uranium dioxide (UO.sub.2) partially enriched in uranium-235. The cold junction is positioned within a cylindrical pellet or compact of depleted uranium dioxide, this second pellet having the identical mass as the first. The uranium-containing pellets are spaced apart by a cylindrical pellet of a high temperature insulator, such as MgO or aluminum oxide (Al.sub.2 O.sub.3). Similar insulator pellets are positioned outwardly from the uranium-containing pellets to prevent heat loss. The entire assembly is enclosed in a cylindrical sheath of a material resistant to the environment of the detector, with this sheath being radially swaged upon the pellets to achieve intimate thermal contact between the pellets and the differential thermocouple.

Abstract: A method is described for detecting and correcting for isotope burn-in during-long term neutron dosimetry exposure. In one embodiment, duplicate pairs of solid state track recorder fissionable deposits are used, including a first, fissionable deposit of lower mass to quantify the number of fissions occuring during the exposure, and a second deposit of higher mass to quantify the number of atoms of for instance .sup.239 Pu by alpha counting. In a second embodiment, only one solid state track recorder fissionable deposit is used and the resulting higher track densities are counted with a scanning electron microscope. This method is also applicable to other burn-in interferences, e.g., .sup.233 U in .sup.232 Th or .sup.238 Pu in .sup.237 Np.

Abstract: A method is described for correcting for effect of isotope burn-in in fission neutron dosimeters. Two quantities are measured in order to quantify the "burn-in" contribution, namely P.sub.Z',A', the amount of (Z', A') isotope that is burned-in, and F.sub.Z', A', the fissions per unit volume produced in the (Z', A') isotope. To measure P.sub.Z', A', two solid state track recorder fission deposits are prepared from the very same material that comprises the fission neutron dosimeter, and the mass and mass density are measured. One of these deposits is exposed along with the fission neutron dosimeter, whereas the second deposit is subsequently used for observation of background. P.sub.Z', A' is then determined by conducting a second irradiation, wherein both the irradiated and unirradiated fission deposits are used in solid state track recorder dosimeters for observation of the absolute number of fissions per unit volume. The difference between the latter determines P.sub.

Abstract: A high fluence neutron dosimetry method is described, including the steps of: exposing a dosimeter containing an alpha-emitting target isotope to neutron irradiation to form an alpha-emitting product isotope; determining the alpha decay rates of the target nucleus and the product nucleus; and using known alpha decay constants for the target nucleus and the product nucleus and the determined alpha decay rates of the target nucleus and the product nucleus to determine the neutron capture rate of the product nucleus.

Abstract: A dosimeter which incorporates new methods for determining neutron dose. Less than one millirad of dose due to neutrons of all energies down to approximately 10.sup.3 eV can be measured, and the response can be adjusted by design of the dosimeter. The dosimeter utilizes the sputtering of material from a target due to the action of the neutrons and measuring of the amount of sputtered material to determine the dose. The sputtered material may be, for example, a noble gas or an inert solid. Various radiator materials can be included to interact with the neutrons so that the resulting charged particles control the sputtering process and hereby increase the sensitivity of the dosimeter. The target material can be, for example, noble-gas-impregnated polycrystalline or amorphous metals. The sputtered material is analyzed using resonance ionization spectroscopy, sputter-initiated resonance ionization spectroscopy or other methods to determine its quantity and hence the neutron dose.