Pion Transparency in 500 MeV C(pi,pi') Reactions?

The question whether there is a pion transparency in 500 MeV $C(\pi, \pi^{'})$ scatterings is studied using a semiclassical, hadronic transport model. The double differential cross sections of this reaction measured at LAMPF can be largely accounted for, if one uses energy-dependent, anisotropic angular distributions which are fitted to pion-nucleon scattering data for the decay of $\Delta(1232)$ and $N^*(1440)$ resonances. The remaining discrepancy between the data and the calculation sets a limit on effects of more exotic processes.Comment: Latex file, 11 pages, 3 figures availabe upon request. Phys. Lett. B in pres

Pion-nucleus elastic scattering on 12C, 40Ca, 90Zr, and 208Pb at 400 and 500 MeV

Pion-nucleus elastic scattering at energies above the Delta(1232) resonance is studied using both pi+ and pi- beams on 12C, 40Ca, 90Zr, and 208Pb. The present data provide an opportunity to study the interaction of pions with nuclei at energies where second-order corrections to impulse approximation calculations should be small. The results are compared with other data sets at similar energies, and with four different first-order impulse approximation calculations. Significant disagreement exists between the calculations and the data from this experiment

An innovative method for extracting isotopic information from low-resolution gamma spectra

A method is described for the extraction of isotopic information from attenuated gamma ray spectra using the gross-count material basis set (GC-MBS) model. This method solves for the isotopic composition of an unknown mixture of isotopes attenuated through an absorber of unknown material. For binary isotopic combinations the problem is nonlinear in only one variable and is easily solved using standard line optimization techniques. Results are presented for NaI spectrum analyses of various binary combinations of enriched uranium, depleted uranium, low burnup Pu, {sup 137}Cs, and {sup 133}Ba attenuated through a suite of absorbers ranging in Z from polyethylene through lead. The GC-MBS method results are compared to those computed using ordinary response function fitting and with a simple net peak area method. The GC-MBS method was found to be significantly more accurate than the other methods over the range of absorbers and isotopic blends studied

A demonstration of the gross count tomographic gamma scanner (GC-TGS) method for the nondestructive assay of transuranic waste

The authors examined the accuracy and sensitivity levels for three variations on the TGS method: the original TGS method using a high-purity germanium (HPGe) detector to measure net areas of full-energy gamma-ray peaks; a modified HPGe-detector method that uses net areas for the transmission analysis and the gross count TGS (GC-TGS) method for the emission analysis; and a NaI-detector method that uses the GC-TGS method exclusively. They found that while the accuracies of the methods were comparable, the GC-TGS method boosted the sensitivity per detector by a factor of approximately two for the HPGe GC variation and four for the NaI method. The implications for improved TGS scanner design are discussed

New, room-temperature gamma-ray detector for improved assay of plutonium

Gamma-ray spectroscopy for portable and unattended assay of nuclear materials requires rugged, reliable, room-temperature detectors that are stable in variable environments and detect gamma rays with good efficiency and energy resolution. For portable assays especially, compact detectors address needs for large numbers of measurements performed in rapid succession with heavy shielding and collimation by a user who must carry the spectroscopy equipment. Most measurements are made with compact NaI detectors. The assay of variable-burnup plutonium and other plutonium materials of variable isotopic composition challenges low-resolution gamma-ray spectroscopy in numerous safeguards applications including holdup measurements, safeguards inspections, monitoring, and safeguards close-out in decontamination and decommissioning. A new, commercial-prototype coplanar-grid CdZnTe detector has been evaluated using the assay of variable-burnup plutonium as a metric indicator to show the substantial benefit of its improved performance compared to results of the same measurements performed with the compact NaI detector. Detector performance, spectrum-quality, and assay results as well as gamma-ray spectra of reference sources are compared for the coplanar-grid CdZnTe and compact NaI detectors to illustrate the advantages of the new room-temperature gamma-ray detector. Isotope identification with the coplanar-grid CdZnTe detector is demonstrated. Preliminary calculations (Monte Carlo coupled to simulations of radiation transport and charge collection) of the spectral response of the detector to plutonium indicate promise for the use of the coplanar-grid CdZnTe detector for further improvements in the accuracy of assays and for analysis of gamma-ray isotopic distributions

A systems framework for defining nonproliferation program technology requirements

This is the final report for a one year Laboratory Directed Research and Development project at the Los Alamos National Laboratory. This systems analysis study provided a framework for evaluating the technology developments needed to support an emerging nonproliferation regime that provides for global fissile materials control. The project produced an integrated program plan describing areas for technology advancement and the supporting Los Alamos strengths. The research objectives and goals of this project are to identify current or future nonproliferation needs where LANL has a strong technical infrastructure. The first step in this process is to identify technical nonproliferation needs based on the global environment

pi+ + d --> p + p reaction between 18 and 44 MeV

A study of the reaction pi+ + d --> p + p has been performed in the energy range of 18 - 44 MeV. Total cross sections and differential cross sections at six angles have been measured at 15 energies with an energy increment of 1 - 2 MeV. This is the most systematic data set in this energy range. No structure in the energy dependence of the cross section has been observed within the accuracy of this experiment.Comment: 20 pages, 7 Postscript figure

Mesonic cloud contribution to the nucleon and delta masses

Pion-nucleon elastic scattering in the dominant $P_{33}$ channel is examined in the model in which the interaction is of the form $\pi + N\leftrightarrow N, \Delta(1232)$. New expressions are found for the elastic pion-nucleon scattering amplitude which differ from existing formula both in the kinematics and in the treatment of the renormalization of the nucleon mass and coupling constant. Fitting the model to the phase shifts in the $P_{33}$ channel does not uniquely fix the parameters of the model. The cutoff for the pion-nucleon form factor is found to lie in the range $\beta = 750\pm350$ MeV/c. The masses of the nucleon and the $\Delta$ which would arise if there were no coupling to mesons are found to be $m_{_N}^{(0)}= 1200\pm 200$ MeV and $m_\Delta^{(0)} = 1500\pm 200$ MeV. The difference in these bare masses, a quantity which would be accounted for by a residual gluon interaction, is found to be $\delta m^{(0)}=350\pm 100$ MeV.Comment: 26 pages, 9 figures, significant rewrit

Report on the GC-MBS method for correcting NaI spectra for transmission loss in hand-held instruments

The goals of this project were (1) to develop a capability to study the scattered components in the NaI spectra of attenuated sources and (2) to evaluate the effectiveness of the gross count material basis set (GC-MBS) method in quantifying transmission losses from the shapes of measured NaI spectra. These goals are related, as the GC-MBS method involves a linear log-spectrum decomposition into MBS component spectra, and scattered gamma rays represent a significant nonlinear interference. Eventually, the authors hope to understand the effect of the scattered components on the MBS decomposition and to develop ways to correct for inaccuracies. As of this writing the authors have not reached that long-term objective, so the two halves of this project are treated here as separate topics, with a separate section for each. They have substantially achieved both of the project goals and are collecting additional data for two publications at the upcoming IEEE conference in Albuquerque, NM--one paper about their work on scattering and another on the GC-MBS method. This project report will contain preliminary portions of those two papers