Search Results
You are looking at 1 - 7 of 7 items for
- Author or Editor: L. Wielopolski x
- Refine by Access: All Content x
Abstract
Recent interest in the use of automated or semi-automated energy dispersive X-ray fluorescence analysis has created the need for improved mathematical techniques and computer software for use with this type of analysis. The present paper reviews the efforts to date to develop the mathematical techniques necessary for implementing: (1) the library least-squares method for the determination of characteristic elemental X-ray intensities and (2) the use of the Monte Carlo method for extending the fundamental parameters approach to radioisotope and X-ray machine exciting sources for the determination of elemental amounts.
Abstract
A spectroscopy system measuring inelastic neutron scattering and thermal neutron capture induced gamma-rays is being developed for in-situ soil analysis. Because a pulsed fast D-T neutron source is utilized, fast neutron induced inelastic neutron scattering reactions are separated in time from thermal neutron capture events. Models utilizing the MCNPX code have been developed to study the time and energy variations of the neutrons in the soil matrix.
Abstract
We are developing a scanning spectroscopy system to measure prompt gammas-rays induced by inelastic neutron scattering and thermal neutron capture to non-invasively analyze soil in situ. Using a radiation source, a 14 MeV (d,t) neutron generator (NG), in a close proximity to the detection system without any precautions will flood and saturate the detectors with direct radiation. Therefore, we devized and partially optimized a shadow shielding sited between the source and the detection system; we discuss our experimental results and basic Monte Carlo calculations.
Abstract
The Monte Carlo code, MCNP5, includes a mesh and lattice tally option useful for large matrix calculations. Recently, a fast lattice tally (FLT) was developed for MCNPX. We used these two codes to model an in-situ soil analysis system based on inelastic neutron scattering. The tallies were utilized to calculate the reaction rates of fast neutrons with carbon via inelastic reactions. The results of these three tallies and their respective computational times are compared, and the advantages of these methodologies discussed.
Abstract
The Library Least Squares method was adapted for use on a standard personal computer. It was found to be considerably more sensitive than the window method in the accurate assessment of65Zn and40K simultaneously presented in human urine samples.
Abstract
High energy gamma-radiation (8 to 30 MeV) is gaining acceptance for radiation therapy of patients with deep cancers. This radiation is of sufficient energy to induce photonuclear activation of the elements in the human body. Our results of measurements of nitrogen and phosphorus in an anthropomorphic phantom, a cadaver, and a cancer patient with bremsstrahlung radiation from 15 MeV electrons demonstrate the feasibility of a method to monitor these two elements in the human body in vivo by measuring the radioactivity induced in these targets by photonuclear reactions.
Abstract
Neutron activation analysis (NAA) systems that use pulsed neutron generators (NGs) employ spectrum gating procedures to segregate nuclear processes by acquiring gamma-ray spectra separately when the generator is on (HIGH gate) and off (LOW gate). Often, the actual neutron burst lags the leading edge of the HIGH gate signal by a few μs. Thus, count rates vary not only between the on and off states of the NG, but within them as well. Recent advances in digital gamma-ray spectrometers that allowed the concurrent acquisition of data by sorting events into two separate spectra based on gate status suggested that a time-resolved analysis that further subdivided the neutron pulse cycle could obtain further information to separate gamma-rays produced by different nuclear reactions. In this paper we introduce a gating system for time-resolved NAA that is capable of concurrently acquiring as many as 16 spectra from up to 8 user-defined time intervals during each of the HIGH gate and LOW gate periods, each with all required timing and count rate information. We present the new gating system’s implementation, operation and some first experimental test results.
