PHYSICS DIVISION, PROGRESS REPORT, JANUARY 1, 1961 TO MARCH 31, 1961

Technical Report · Tue Oct 31 00:00:00 EST 1961

OSTI ID:4018570

Nuclear Physics Research. Investigations into various properties of nuclear excited states are continuing. Of special interest is a state in Ne/sup 20/ at 5 Mev which was believed to be involved in the thermonuclear reactions producing neon from helium in the stars. The lifetime measured was anomalously long and led to new measurements of the spin and parity. The spin and parity found show that this level cannot be excited in the thermonuclear reactions proposed and have led to revisions in the current ideas about the creation of elements in the universe. Crystal Dynamics of Sodium Iodide. The longitudinal optical vibrations make up the highest frequency branch of elastic waves in a crystal. In these longitudinal waves the ions of opposite charge are moving in opposite phase. Recently the frequency wave-number dispersion relation for this branch in sodium iodide was carefully studied with a constant "Q" spectrometer at the NRU reactor. A specially pure Nal crystal with very small mosaic spread was used. The results confirm a general relation between frequencies and elastic constants, but are in disagreement with predictions of the current "shell model" used for ionic crystals. An analysis of the results may give detailed information on the distortion of the large negative ions induced by the fast coherent motions of the light positive ions. Developments in Theory. Theoretical studies were carried out on a number of problems in connection with power reactor fuel cladding, which include the expansion of UO/sub 2/ pellets subjected to a radial temperature variation, the diffusion of oxygen in zirconium metal, and the diffusion of hydrogen in Zircaloy. The (n, alpha ) cross section of O/sup 16/ at energies of 4 to 10 Mev was estimated for use in reactor calculations. The Datatron continues to perform satisfactorily with useful operation being about 450 hours per month. Developments in Electronics. The 900-channel coincidence kicksorter was installed in the Tandem Van de Graaff building and pre liminary trials were satisfactory. The encoder used in the 900- channel analyzer was further developed and the improved version will replace the vacuum-tube type now used in the Chahk River 100-channel kicksorter. In addition to increased reliability the temperature stability, differential linearity, and stability against count-rate were all improved. The use of high resolution semiconductor detectors for alpha spectrometry has emphasized the need for extreme stability in pulse height analyzers. To this end work was begun on the stabilization of spectrum position by a control system feeding information related to drift back to the system again. The first results indicate that a considerable improvement in resolution can be obtained. The work on particle detection in scintillating materials by pulse shape discrimination was continued. With a combination of pulse shape and pulse height analysis the following result is obtained: when 99.5% of the gamma-ray pulses from RdTh above 400 kev are rejected by pulse shape discrimination 65% of the 2.5 Mev neutrons detected by the counter from the D(d,n) reaction and 75% of the 14-Mev neutrons from the T(d,n) reaction are counted. (auth)

• Research Organization: Atomic Energy of Canada Ltd., Chalk River Project, Chalk River, Ont.
• NSA Number: NSA-15-025296
• OSTI ID: 4018570
• Report Number(s): PR-P-49; AECL-1266
• Resource Relation: Other Information: Orig. Receipt Date: 31-DEC-61
• Country of Publication: Canada
• Language: English

Related Subjects

PHYSICS
ALPHA PARTICLES
CROSS SECTIONS
CRYSTALS
DATATRON
DIFFUSION
ELASTICITY
ELECTRIC CHARGES
ENERGY
ENERGY RANGE
EQUATIONS
EXPANSION
FREQUENCY
FUELS
HYDROGEN
IONS
METALS
MEV RANGE
MOLECULES
MOTION
NEUTRON BEAMS
NRU
NUCLEAR REACTIONS
NUMERICALS
OSCILLATIONS
OXYGEN
OXYGEN 16
PELLETS
POWER
REACTORS
SODIUM IODIDES
SPECTRA
SPECTROMETERS
TEMPERATURE
URANIUM DIOXIDE
USES
VARIATIONS
ZIRCALOY
ZIRCONIUM