Chalk River Laboratories

About: Chalk River Laboratories is a based out in . It is known for research contribution in the topics: Neutron diffraction & Neutron scattering. The organization has 2297 authors who have published 2700 publications receiving 73287 citations.

Calibration of the Harwell series II Bi-implanted RBS standards

Abstract: The Bi content of several Series II Rutherford backscattering (RBS) standards (Bi-implanted silicon) has been calibrated by comparison with an earlier Series I standard and also by an independent measurement of the absolute RBS yield. Both methods agree within ± 1% on a given sample. Independent measurements at each of CRNL and CBNM Geel indicate Bi implant uniformity better than 1% across each target and good agreement (± 1%) in the absolute Bi content of exchanged samples. Most of the Bi assays agree within the combined counting statistics (± 1%) with Geel's previous Series II calibration value of (4.75 ± 0.07) × 1015 cm−2; however,two targets were found to contain ∼ 4% more Bi. Harwell's implantation records show that the two higher dose samples were both cut from the same implanted wafer and that poor vacuum conditions during implantation may have been responsible for this excess dose. Since the implantation history of each wafer has been well documented, there should be no difficulty in establishing which calibration value is appropriate for an individual standard.

Major congenital malformations from irradiations of sperm and eggs

Abstract: Major malformations of the embryos of trout are substantially more frequent following exposure of the sperm or eggs to ionizing radiation. The response per unit dose falls off at high doses but at 200 rads, the lowest dose used, there is a yield of approx. 300 malformations per 10 6 embryos per rad, for irradiations of either kind of gamete. Assuming that the response varies linearly with dose at still lower levels, approx. 26 rads would be required to double the rate observed in the controls. Reasons for believing that the major malformations may be associated predominantly with gross chromosomal changes, such as those due to non-disjunction, are discussed. The advantages of this organism for studies of the dose-response relationships down to low doses, the current lack of such informations, and its possible bearing on both a theoretical problem and the practical task of assessing radiation risks in man, are noted.

Hybrid coded aperture and Compton imaging using an active mask

Abstract: The trimodal imager (TMI) images gamma-ray sources from a mobile platform using both coded aperture (CA) and Compton imaging (CI) modalities. In this paper we will discuss development and performance of image reconstruction algorithms for the TMI. In order to develop algorithms in parallel with detector hardware we are using a GEANT4 [J. Allison, K. Amako, J. Apostolakis, H. Araujo, P.A. Dubois, M. Asai, G. Barrand, R. Capra, S. Chauvie, R. Chytracek, G. Cirrone, G. Cooperman, G. Cosmo, G. Cuttone, G. Daquino, et al., IEEE Trans. Nucl. Sci. NS-53 (1) (2006) 270] based simulation package to produce realistic data sets for code development. The simulation code incorporates detailed detector modeling, contributions from natural background radiation, and validation of simulation results against measured data. Maximum likelihood algorithms for both imaging methods are discussed, as well as a hybrid imaging algorithm wherein CA and CI information is fused to generate a higher fidelity reconstruction.