Particle Tagging Research Articles

Tagged Particles in Monte Carlo Calculations of Radiation Transfer Using the Prizma Computer Program

The additional possibilities due to the introduction into the PRIZMA program, intended for performing Monte Carlo calculations of linear radiation transfer problems, of a particle tagging technique are studied. In calculations, it is often necessary to estimate the contribution of particles which were in some particular situation. The tagged-particle method was developed to obtain such results. A particle is tagged with a marker and the results are recorded as a function of whether or not the particle is tagged. To solve multivariant problems, arising in the calculation of the effects due to small perturbations, a special method was developed for simulating trajectories using tagged particles. This method makes it possible to obtain in a single calculation correlated results for all variants of the problem. The possibilities of the tagged-particle method and the special method of simulation are illustrated for numerical examples.

Bioturbation and particle transport in Carolina slope sediments: A radiochemical approach

In situ tracer experiments investigated short-term sediment mixing processes at two Carolina continental margin sites (water depth = 850 m) characterized by different organic C fluxes, 234 Th mixing coefficients (D b ) and benthic assemblages. Phytoplankton, slope sediment, and sand-sized glass beads tagged with 210 Pb, 113 Sn, and 228 Th, respectively, were placed via submersible at the sediment-water interface at both field sites (Site I off Cape Fear, and Site III off Cape Hatteras). Experimental plots were sampled at 0, 1.5 days, and 90 days after tracer emplacement to examine short-term, vertical transport. Both sites are initially dominated by nonlocal mixing. Transport to the bottom of the surface mixed layer at both sites occurs more rapidly than 234 Th-based D b values predict; after 1.5 days, tagged particles were observed 5 cm below the sediment-water interface at Site I and 12 cm below at Site III. Impulse tracer profiles after 90 days at Site III exhibit primarily diffusive distributions, most likely due to a large number of random, nonlocal mixing events. The D b values determined from 90-day particle tagging experiments are comparable to those obtained from naturally occurring 234 Th profiles (∼100-day time scales) from nearby locations. The agreement between impulse tracer mixing coefficients and steady-state natural tracer mixing coefficients suggests that the diffusive analogue for bioturbation on monthly time scales is a realistic and useful approach. Tracer profiles from both sites exhibit some degree of particle selective mixing, but the preferential transport of the more labile carbon containing particles only occurred 30% of the time. Consequently, variations in the extent to which age-dependent mixing occurs in marine sediments may depend on factors such as faunal assemblage and organic carbon flux.

Passive and Active Tagging of Glass-Fiber Polymeric Composites for In-Process and In-Field Non-Destructive Evaluation

Conventional non-destructive evaluation (NDE) methods are not very effective in monitoring the material conditions of advanced composite and adhesive joints. A technology that has been proposed to enhance the inspectability of advanced composites is the particle tagging technique. Two theoretical models were recently proposed to characterize the dynamic behavior of ferromagnetic and magnetostrictive tagging particles. These theoretical models concerning the development of an active tagging technique with embedded ferromagnetic and magnetostrictive particles and magnetic excitation are now experimentally verified. The experimental results of the active particle tagging shows a variation in the dynamic response of the specimens when defects and/or damage are present. The sensory signature from a tagged polymer is extracted as a result of the interaction between the embedded particles and their host matrix. A study of various types of composites and tagging particles for passive and active tagging was performed. Experimental validation of concepts for tagging of structural materials for on-site inspection prior to installation have also been explored. The on-site particle tagging inspection has been verified on laboratory specimens obtained from industry and was shown to be very efficient.

Measurement of hydrogen transport in deuterium discharges using the dynamic response of the effective mass

Particle tagging in a tokamak provides an attractive method for studying transport mechanisms. The injection of test particles at the plasma edge and the subsequent measurement of the evolution of their concentration at the centre can be used to quantify the underlying transport mechanisms. This has been carried out on the TCA tokamak by injecting hydrogen into a deuterium discharge and simultaneously measuring the temporal evolution of the central effective mass and the edge ionization rate.

A gray code hodoscope and fast buffer for beam particle tagging

We have developed a scintillation counter hodoscope to measure the vertical position of a high energy charged particle with associated identity information. It may be used to tag beam tracks seen in detectors with poorer time resolution, such as bubble or spark chambers. The hodoscope consists of six overlapping planes of plastic scintillator strips 1 16 in. thick, 3 in. wide, and varying height and vertical spacing. The vertical resolution is 3 32 in. over a 6 in. height. Each plane is connected to a single photomultiplier tube. The output from the six tubes forms the Gray code + of the vertical position of a track passing perpendicularly through the planes. This and three bits of tagging information form a nine bit word associated with each track. Up to 16 such words are stored in an ECL buffer capable of accepting a new track every 20 ns. The buffer is interfaced to a DGC Supernova computer through CAMAC. The construction and performance of the device are discussed.