A semicircular focussing spectrometer has been built to examine beta spectra in the energy range below 100 Kev. The detection of the beta particles is accomplished by means of Geiger counters filled with the saturated vapor of liquid heptane (C₇H₁₆) kept in a bath of melting ice. The windows of the counters are made from thin films of zapon about 5 to 8 micrograms/cm² in thickness. The sources are mounted on similar films approximately 10 micrograms/cm² and have an average total thickness of the order of 30 micrograms/cm² . The combination of thin source and thin windows enables measurements of spectra to be made down to an energy of 2 Kev. An examination of the beta spectrum of RaD (₈₂Pb²¹⁰) with the spectrometer has been carried out. It consists of L, M and N conversion lines of a 47 Kev. gamma ray, a peak at about 3 Kev assigned to conversion of a 7.7 Kev gamma in the M shell of the atom, and a primary beta spectrum. A Kurie plot of the primary beta spectrum yields an end point of 21.7 Kev. In addition there are two weak conversion lines at 18 and 21 Kev which are tentatively assigned to the L conversion of gamma rays of 34 and 37 Kev. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The stopping powers of hydrogen and deuterium have been compared, using a thin ionization chamber. The results were found to be consistent with the present-day theory on the method of energy loss. A method for the preparation of thin films of organic phosphors has been devised and the response of these films to alpha particles has been tested. All necessary apparatus for the study of angular correlation and distribution patterns for F¹⁹(pαγ)O¹⁶ and N¹⁵(pα)C¹² reactions has been constructed. The theoretical angular distribution patterns for the N¹⁵(pα)C¹² reaction have been calculated. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

PART 1 A new method has been used to suppress the undesirable Compton electrons ordinarily present in photoelectron spectra. As much as 90% of the Compton electron intensity was removed. This was accomplished by electronic cancellation of the individual Compton electrons. The method has been used with a thin lens type of spectrometer and has made possible the detection of new gamma rays at .391, .857 and 1.00 Mev. in Ra(B + C), at 1.01 Mev. in Ta¹⁸², and at .472 and .843 Mev. In Sb¹²⁴. No.new gamma rays were observed from Co⁶⁰. PART 2 A search for double beta decay in Sn¹²⁴ has been made using a coincidence technique particularly suited to double beta decay under the Majorana form of neutrino theory. Negative results were obtained and a lower limit of 0.3 - 0.7 x 10¹⁷ years has been set on the half-life of the process. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

A superconducting thin film tunnel junction (Sn-Sn0₂ -Sn) of total thickness 4000 Å, area 7 x 10ˉ⁴ cm² and normal (4.2 K) resistance 77 mΩ was prepared on a glass substrate. When cooled to 1.2 K the junction was biased at 0.3 mV where, the Josephson supercurrent having been suppressed with a magnetic field, the junction dynamic resistance had its maximum value of 9.3Ω . The junction was then bombarded with 5.1 MeV alpha particles and the resulting pulses induced in the tunneling current were observed to have amplitudes up to 19 times the preamplifier-dominated rms output noise level. For purposes of analysis, it was assumed that the induced current pulse had the form i(t) = i₀ exp(-t/Ƭ), t ≥ 0. With this form of the current pulse and the known transfer function of the transmission line-amplifier system, it was calculated that for all pulses T = (1.38±.33)xl0ˉ⁷ sec and that for the largest amplitude pulses, corresponding to an energy loss ΔE⍺ ≤2.75 MeV, i₀ lay in the range 20 ≤ i₀ ≤ 26 μA with a most probable value of 22 μA. With this value of i₀ and ΔE⍺ = 2.75 MeV, an upper limit of 8.2 x 10ˉ³ eV has been assigned to the value of w(Sn), the average energy expended by the alpha particle to excite a quasiparticle pair in superconducting tin at 1.2 K. A tentative theory of the superconducting tunnel junction charged particle detector is given and the cryogenic and electronic apparatus required for the measurements are described. Details related to thin film junction fabrication technology and interpretation of dc experimental results are discussed in four appendices. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The alpha-particle reduced widths for the ground state in Po²¹² are calculated on the basis of the nuclear shell model, employing the technique of Harada, but treating the nuclear surface in a more direct manner. It is contended that the calculations of previous authors, who have generally used a square-edge nucleus and a Coulomb barrier rounded-off by the nuclear potential of Igo, have, essentially, used the equivalent square-edge nucleus model of Vogt. Their J.W.K.B. estimate of the barrier penetrabilities is checked by an analytic calculation in Chapter 3 and is found to be reasonable. It is shown in Chapter 4 that, in the scattering of an alpha-particle from the ground state of Pb²⁰⁸, the diffuse nuclear edge considerably enhances the one-body reduced widths and, in a direct manner, that it similarly enhances the one-body differential elastic scattering cross-section. In this manner, it is demonstrated that the radius involved in the equivalent square-edge nucleus model must be considerably larger than that of the diffuse-edge nucleus to which it corresponds. This is shown directly in Chapter 5, where the validity of the equivalent square-edge nucleus model in heavy nuclei is examined. It is contended that this explains the large radii found in previous calculations. This is demonstrated directly by repeating the calculation of Harada with the diffuse nuclear edge being introduced in a direct manner. Although the effects of configuration mixing have not been directly examined, it has been concluded that shell model calculations can explain the major part of rates provided that the nuclear surface is manner. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

An intermediate image beta ray spectrometer has been constructed using the two magnets from two thin lens spectrometers, previously in use in this laboratory. A surface barrier type detector replaces the scintillator -photomultiplier arrangement used before, resulting in greatly reduced background noise. The performance of this spectrometer is considerably better than the two it replaces, having resolutions of 0.51 %, 0.7 %, 0.94 % and 2.2 % at transmissions of 0.49 %, 0.96 %, 1.26 % and 5.96 %. The normal energy range is from 25 Kev, to 1.5 Mev but it can be extended to 2.0 Mev with some loss of transmission. An examination of the beta spectrum of Eu¹⁵⁴ was carried out with this instrument. A Kurie plot of the continuum has been made and six primary beta groups found with end point energies of 1.866 Mev, 1.198 Mev , 0.976 Mev , 0.843 Mev , 0.579 Mev , and 0.274 Mev with relative abundances of 10.8 %. 0.67 %, 4.6 %, 17.0 %, 37.8 %, and 29.1 %. Both end-points and relative intensities are in excellent agreement with data from other workers. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The crystal structure of diferrocenyl ketone has been analyzed using Fe(Kα) X-radiation. The molecule is symmetrical about a 2-fold axis passing through the carbonyl bond. Coordinates of the iron atom were determined from two Patterson-Harker sections and coordinates of the remaining atoms were derived from subsequent three dimensional Fourier summations. Structure refinement was carried out using (block-diagonal) least squares with allowances for anisotropic temperature vibration. The R value derived from the final coordinates is 0.09. The cyclopentadienyl rings not bonded to the keto group are vibrating more than those which are; when this is taken into account the iron atom lies midway between the cyclopentadienyl rings which are planar and 3.30 Å apart. The carbon bond lengths in these rings are all the same length (1.45 Å) and the conformation of one ring with respect to the other is almost eclipsed. The intermolecular contacts are all of normal length. The molecular dimensions of anti-8-tricyclo [3,2,1,0²˒⁴] octyl p-bromobenzenesulphonate and anti-7-norborneny1 p-bromo-benzoate have been measured to assist in the interpretation of the solvolytic reactivity in norbornane derivatives. Data were collected (Cu(Kα) radiation) by counter methods in both cases; the structures were determined using the heavy atom-Patterson method and refinements were carried out using differential syntheses and (block-diagonal) least squares. The discrepancy factors derived from the final coordinates are 0.09 and 0.18 respectively. The norbornane and norbornene skeletons have symmetry m and the bond lengths are normal. The bond angles at the methylene bridge are 97° and 96° respectively, the other angles are all less than the tetrahedral angle. The angles between the planes formed by different parts of the skeleton are identical in both cases. Bond lengths and angles in the remainders of both molecules are of normal dimensions. The configuration of the cyclopropyl methylene group in anti-8- tricycle [3,2,1,0²˒⁴] octyl p-bromobenzenesulphonate is exo to the norbornane skeleton. The results indicate that there is insufficient variation in the methylene bridge bond angles to account for the difference in solvolytic reactivity. The crystal and molecular structure of ochotensine methiodide has been investigated in order to determine the chemical structure of the molecule. The data were recorded photographically using Cu(Kα) radiation and a Weissenberg equi-inclination camera; estimation of the intensities was carried out by visual methods and interfilm scales were derived from corresponding symmetry related structure amplitudes. 845 independent reflections were measured in this way. The position of the iodine atom was determined from a three dimensional Patterson function and the positions of the remaining atoms from three subsequent three-dimensional Fourier maps. Refinement of the temperature and atomic parameters was carried out by (block diagonal) least squares; the final R value was 0.11. The analysis has shown that the structure of ochotensine is similar to that postulated for ochotensimine and the position of the phenolic group on ring A has been determined. A difference synthesis was carried out to verify the positions of the atoms. The bond lengths and angles are normal but several short intermolecular contacts were observed. The planes of the two benzene rings are inclined at an angle of 94°. / Science, Faculty of / Chemistry, Department of / Graduate

A technique is described for improving wood fibre web strength by copolymerization of a hydrocarbon drying oil (CTLA Polymer) within hand-sheets made from pure and admixed forms of high yield chemical (sulfite and sulfate) and groundwood fibres. Oil polymerization can be initiated successfully by prolonged thermal treatment at 145°C, as well as by the novel method of low dosage gamma-ray irradiation. The treatment strengthens inter-fibre bonding. Evidence for copolymerization was sought through assessment of tensile and related strength data on variously treated standard handsheets. Effectiveness of the polymerization on pulp types investigated as initiated by heat and low dosage irradiation is strongly related to surface colloidal and basic physical and mechanical properties of the fibres. Maximum strength parameters were obtained with oil saturated sulfite and groundwood handsheets following polymerization by thermal treatment. Copolymerization efficiency by irradiation, on the other hand, is estimated as 73% for sulfite, 65% for groundwood and 50% for kraft handsheets. Effectiveness of oil polymerization by irradiation was found to be proportional to dosages up to 10⁵rad. As anticipated, limit of strength improvement was not set entirely by intrinsic fibre strength, but was also influenced by surface colloidal properties of the fibres. Blends made from chemical-groundwood fibre mixtures behaved more or less proportional to individual pulp strengths and extent of blending. Copolymerized sulfite-groundwood blends at equal proportions approximated the tensile strength of similar kraft papers suggesting better economy with kraft fibres when papers of limited strength are produced. All other strength parameters (elastic modulus, tensile strain and tensile energy absorption) followed similar trends, or if different were of aid in explaining certain phenomena characteristic to treated fibre webs. The presence of graft copolymer could not be conclusively proven, since both the copolymer and oil homopolymer are insoluble in the usual organic solvents. A dual character of the oil polymer was demonstrated with glass filterpaper and highly purified commercial cellulose fibres. Effectiveness of oil polymerization in highly lignified mechanical pulps was greatly depressed by mild sodium chlorite treatment, although the strength and bonding capacity of such fibres increased considerably. This was taken as direct evidence for the possibility of a lignin-CTLA Polymer copolymer system. Site of chemical reaction has not been described, although means for assessment of such information are suggested. The study proves the usefulness of gamma irradiation as energy source for the copolyerization of drying oils in handsheets as replacement for the prolonged thermal treatment hitherto used by the hardboard industry. Added advantages of irradiation processed copolymerized papers are less discoloration, especially with high lignin content pulps, and lower elastic modulus, a factor clearly objectionable for some paper uses. / Forestry, Faculty of / Graduate

The first part of this thesis describes measurements made with medical radium sources to determine the ratio of the exposure in a large (essentially infinite) water "phantom" to the exposure at the same point in air, i.e., to determine the fractional transmission in an "infinite" water phantom. The fractional transmission was measured as a function of the distance between the radium sources and the measuring instrument. The radium used was sealed in platinum containers which absorbed the primary alpha and beta rays from the radium so that the exposures were due to gamma rays only. All measurements were made with small air-filled ionization chambers with plexiglass walls. Ionization currents were measured with these chambers in water and in air. The corrections which were required to determine the ratio of exposure in water to exposure in air from these measurements and the preliminary experiments necessary to determine the required corrections are described in the thesis. The fractional transmission through water is shown graphically as a function of the distance between source and point of measurement. Also, the relationship is described by an empirical equation. The curve drawn fits the experimental points obtained under a variety of conditions of measurement within the experimental error of 1/2 to 1%. The second part of the thesis describes measurements of ionization currents made with an experimental set-up in which the ionization chamber was at a fixed distance vertically below the radium and the whole assembly was moved relative to the surface of a water phantom. From measurements made with the radium above the surface, in the surface and below the surface of the water, it was possible (a) to obtain data which could be compared with the results of Part I and (b) to obtain correction factors which could be applied to the results of Part I to correct for reduced scatter when the radium was in the surface, rather than well immersed in water. The results of the present experiment are compared with those of previous workers. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

A low temperature x-ray powder diffraction attachment for use on the vertical goniometer of a diffractometer is described. We have found that diffraction patterns obtained with the attachment mounted on the goniometer are of comparable quality to those obtained on the goniometer itself. Using this attachment, the lattice parameter discontinuities associated with a charge density wave phase transition in 1T-TaS₂ near T=200K are measured with an accuracy greater than that of any previous results. Electrochemically prepared samples of Li xTiS₂ near x=0.16 are studied at room temperature and below. Clear evidence for the formation of a stage two superlattice at low temperatures was not obtained. / Science, Faculty of / Physics and Astronomy, Department of / Graduate