125 research outputs found
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Measurements of Separate Neutron and Gamma-Ray Coincidences with Liquid Scintillators and Digital PSD Technique
A new technique is presented for the measurement of neutron and/or gamma-ray coincidences. Separate neutron neutron, neutron gamma-ray, gamma-ray neutron, and gamma-ray gamma-ray coincidences are acquired with liquid scintillation detectors and a digital pulse shape discrimination (PSD) technique based on standard charge integration method. The measurement technique allows for the collection of fast coincidences in a time window of the order of a few tens of nanoseconds between the coincident particles. The PSD allows for the acquisition of the coincidences in all particle combinations. The measurements are compared to results obtained with the MCNP-PoliMi code, which simulates neutron and gamma-ray coincidences from from a source on an event-by-event basis. This comparison leads to good qualitative agreement
Purdue Conference on Active Nonproliferation
One major problem with nuclear security measurements involves source identification inthe presence of low signal-to-background ratio. This scenario iscommon to several applications, ranging from radiation identification atportal monitors to radiation source search with unmanned vehicles. In this context of identification of a large variety of sources, including natural and medical sources, sensitive sources of particular interest, but also potentially new/unknown sources for which no reference measurement is available, statistical methods are particularly appealing for their ability to capture the random nature of the measurements. Among them, Bayesian methods form a generic framework allowing for uncertainty quantification and propagation, which is of prime interest for detection (of known and unknown sources), classification, and quantification of smuggled nuclear and radiological materials. We demonstratethe use of Bayesian models for the identificationof mixed gamma sources, measured with organic scintillatorswithinshort acquisition times. We alsocompare the estimation performance using two different materials: liquid EJ-309 and stilbene crystal
Multiplicity counting using organic scintillators to distinguish neutron sources: An advanced teaching laboratory
In this advanced instructional laboratory, students explore complex detection
systems and nondestructive assay techniques used in the field of nuclear
physics. After setting up and calibrating a neutron detection system, students
carry out timing and energy deposition analyses of radiation signals. Through
the timing of prompt fission neutron signals, multiplicity counting is used to
carry out a special nuclear material (SNM) nondestructive assay. Our
experimental setup is comprised of eight trans-stilbene organic scintillation
detectors in a well-counter configuration, and measurements are taken on a
spontaneous fission source as well as two ({\alpha},n) sources. By comparing
each source's measured multiplicity distribution, the resulting measurements of
the ({\alpha},n) sources can be distinguished from that of the spontaneous
fission source. Such comparisons prevent the spoofing, i.e., intentional
imitation, of a fission source by an ({\alpha},n) neutron source. This
instructional laboratory is designed for nuclear engineering and physics
students interested in organic scintillators, neutron sources, and
nonproliferation radiation measurement techniques.Comment: 29 pages, 17 figures, pre-proof accepted to AJP, AJP number
AJP22-AR-01524R2 (DOI: 10.1119/5.0139531
Radiation Tolerance of Low-Cost Magnetometer for Space Applications
Knowing the three-dimensional magnetic field configuration and dynamics in space environments is key to understand the physical processes taking place. Plasma dynamics depend on the local orientation of the magnetic field, and key quantities such as pitch angle and dynamical processes such as waves and reconnection cannot be studied without in-situ measurements of the fields. For this reason, magnetometers are one of the most important instruments for space physics-focused missions. This is true both for spacecraft and also for landed missions, particularly on atmosphere-less bodies, where the space environment interacts directly with the surface. To enable the next generation of small spacecraft and landers, sensors need to be low-cost and withstand the harsh radiation environment present in space. Here we present the latest advances in the characterization of a commercial-off-the-shelf three-dimensional magnetometer,summarizing previous and newresults from radiation tests. The sensor shows tolerance up to a total ionization dose (TID) of 300 krad, levels well beyond those typical for a low-Earth orbit mission, and compliant with those expected during a landed mission on the Jovian moon Europa
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Monte Carlo Simulation for LINAC Standoff Interrogation of Nuclear Material
The development of new techniques for the interrogation of shielded nuclear materials relies on the use of Monte Carlo codes to accurately simulate the entire system, including the interrogation source, the fissile target and the detection environment. The objective of this modeling effort is to develop analysis tools and methods-based on a relevant scenario-which may be applied to the design of future systems for active interrogation at a standoff. For the specific scenario considered here, the analysis will focus on providing the information needed to determine the type and optimum position of the detectors. This report describes the results of simulations for a detection system employing gamma rays to interrogate fissile and nonfissile targets. The simulations were performed using specialized versions of the codes MCNPX and MCNP-PoliMi. Both prompt neutron and gamma ray and delayed neutron fluxes have been mapped in three dimensions. The time dependence of the prompt neutrons in the system has also been characterized For this particular scenario, the flux maps generated with the Monte Carlo model indicate that the detectors should be placed approximately 50 cm behind the exit of the accelerator, 40 cm away from the vehicle, and 150 cm above the ground. This position minimizes the number of neutrons coming from the accelerator structure and also receives the maximum flux of prompt neutrons coming from the source. The lead shielding around the accelerator minimizes the gamma-ray background from the accelerator in this area. The number of delayed neutrons emitted from the target is approximately seven orders of magnitude less than the prompt neutrons emitted from the system. Therefore, in order to possibly detect the delayed neutrons, the detectors should be active only after all prompt neutrons have scattered out of the system. Preliminary results have shown this time to be greater than 5 ?s after the accelerator pulse. This type of system is illustrative of a host of real-world scenarios of interest to nonproliferation and homeland security. Due to the multistep procedure of the MCNPX/MCNP-PoliMi code system, the analysis of somewhat modular - meaning that changing details such as the detector type, position, or surroundings does not require a re-calculation of the source-target interactions. This feature allows for efficient parametric analysis of numerous system parameters without recomputing the constant source-target behavior. Such efficient analysis mechanisms could prove invaluable in the design and future deployment of an active interrogation detection system
Proteinuria and albuminuria at point of care
Proteinuria is a key diagnostic and pathophysiological aspect of kidney dysfunction, influencing the progression of kidney and systemic diseases. Both general practitioners and specialists should be able to discriminate the relevance of proteinuria, starting from a urine sample, and eventually referring selected patients to a nephrologist for further diagnostic workup and treatment, because most kidney diseases are not symptomatic until renal function is lost or severely compromised. As the interpretation of proteinuria is dependent on the method used to detect it, the aim of this article was to review laboratory and point-of-care diagnostic methods for proteinuria in different settings, such as the prevention and follow-up of common chronic diseases (i.e., hypertension, diabetes, chronic kidney disease). Urine dipsticks remain the most widely used method for detecting proteinuria, although different types of proteinuria, extreme pH values and urine concentration may affect their results. Albumin to creatinine ratio and protein to creatinine ratio performed on a spot urine sample are reliable tests that can effectively replace 24-hour urine collection analysis in clinical practice
Expansion of Ventral Foregut is linked to changes in the Enhancer Landscape for Organ Specific Differentiation
MeV-Energy X Rays from Inverse Compton Scattering with Laser-Wakefield Accelerated Electrons
We report the generation of MeV x rays using an undulator and accelerator that are both driven by the same 100-terawatt laser system. The laser pulse driving the accelerator and the scattering laser pulse are independently optimized to generate a high energy electron beam (\u3e200 MeV) and maximize the output x-ray brightness. The total x-ray photon number was measured to be ∼1×107, the source size was 5 μm, and the beam divergence angle was ∼10 mrad. The x-ray photon energy, peaked at 1 MeV (reaching up to 4 MeV), exceeds the thresholds of fundamental nuclear processes (e.g., pair production and photodisintegration)
Submillimeter-resolution radiography of shielded structures with laser-accelerated electron beams
We investigate the use of energetic electron beams for high-resolution radiography of flaws embedded in thick solid objects. A bright, monoenergetic electron beam (with energy \u3e100 MeV) was generated by the process of laser-wakefield acceleration through the interaction of 50-TW, 30-fs laser pulses with a supersonic helium jet. The high energy, low divergence, and small source size of these beams make them ideal for high-resolution radiographic studies of cracks or voids embedded in dense materials that are placed at a large distance from the source. We report radiographic imaging of steel with submillimeter resolution
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