Showing papers by "Chalk River Laboratories published in 1974"

Bremsstrahlung radiators and beam filters for 25-MeV cancer therapy.

Abstract: Bremsstrahlung spectra and on‐axis depth‐dose distributions due to 25.5‐MeV electrons incident on seven different Ta and one Al radiator were studied, with and without beam‐hardening filters of Al and Pb. The photon spectra were measured with a gamma‐ray spectrometer consisting of a liquid deuterium target viewed by a time‐of‐flight detector of photoneutrons. A remote‐controlled, miniature ion chamber was used to measure depth‐dose profiles in a water phantom. The Ta radiators ranged in thickness from 0.012 radiation length up to 1.0 X 0. The thinner the radiator, the harder was the measured spectrum. The maximum forward yield was obtained for a thickness of about 0.3 X 0. The forward yield and spectral shape of the photon beam from 0.07 X 0 of Al as radiator were very similar to those from 0.06 X 0 of Ta. Beams produced in Ta radiators and filtered by 27.28 g/cm2 of Al gave a harder spectrum than those filtered by 15.06 g/cm2 of Pb. Total absorption cross sections of Al and Pb for photon energies between 4 and 24 MeV were obtained which agree with theoretical calculations, within measurement errors. The depths in water at which the dose fell to 0.5 of peak dose was greater when the Al filter was used than when the Pb filter was used. For end point energies greater than 10 MeV, beam‐hardening and field‐flattening filters should be made, if space permits, of low‐atomic‐number materials.

Cyclic Voltammetry and Chronocoulometry with trans‐ Rh ( en ) 2Cl2 + at Mercury Electrodes

Abstract: Cyclic voltammetric, coulometric, and chronocoulometric data associated with the reduction of at mercury electrodes are reported that confirm previous results indicating the occurrence of a two‐electron reduction to produce the hydrido complex, , which engages in a pH dependent equilibrium involving . The resulting presence of at the electrode surface has a number of interesting consequences which are described. Among these are the electrochemical production of metal‐metal bonded rhodium‐mercury adducts, apparent strong adsorption of on the electrode surface, and anomalous cyclic voltammograms with inverted peaks.

The Location of Displaced Manganese and Silver Atoms in Irradiated Aluminum Crystals by Backscattering

Abstract: By measuring the energy spectra of backscattered 1 MeV He+ ions from Al-0.09 at.% Mn and Al-0.08 at.% Ag crystals, it was found that substitutional Mn and Ag atoms were displaced from lattice sites by irradiation with 0.3–1.0 MeV He+ ions at 35°-70°K. From detailed channeling and annealing results, it was demonstrated that the Mn and Ag atoms were displaced by trapping irradiation-induced interstitial Al atoms, forming Al-Mn and Al-Ag atom pairs in the dumbbell configuration.

Measurement of low level environmental γ doses with TLDS and geiger counters

Abstract: Environmental monitoring using a complementary system of TLDs and Geiger counters is described. The inexpensive TLDs give integral dose data at many points in the surveillance area, while the Geiger counter instruments, though more expensive, allow measurement of smaller doses and show changes of dose rate with time at points of particular interest in the vicinity of nuclear facilities.