A proton polarimeter has been constructed at TRIUMF, with design specifications intended to measure the polarization of protons over an energy range of 100 MeV to 300 MeV. It was built as the principle detector in an experiment to determine three spin-transfer parameters of the fundamental π⃗d → p⃗p reaction. In this thesis, some theoretical and experimental design aspects of the spin-transfer measurement are discussed. The intent of this thesis is to describe an experiment¹ which measures the polarization of protons emitted from the πd→ p⃗p reaction, using an unpolarized target². The sole purpose of this experiment is to demonstrate that our polarimeter and general apparatus are capable of identifying the πd → pp events from a large background presence, and that the systematic errors associated with the polarization extraction have been identified. To this extent, the system is ready to produce the proton polarization required for the spin-transfer measurements. ¹This experiment is identical in all respects to the spin-transfer experiment, except that here, the target is unpolarized. ²The polarization of the protons is well know from the analyzing power, An₀, of the time reversed p⃗p → dπ reaction. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

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TRIUMF, Canada’s nuclear and particle physics research laboratory is currently in development of an Advanced Rare Isotope Facility (ARIEL) that will contain a newly designed electron target station. The target at this station is susceptible to destruction from instantaneous spot heating of the beam. To mitigate this, a raster system consisting of two AC electromagnets was proposed. The two magnets will work in tandem, vertical and horizontal, bending to produce raster patterns at 10 kHz. Since complex patterns consist of harmonics higher than the fundamental frequency, a design frequency of 100 kHz was chosen. AC current causes eddy currents which lead to the skin effect, causing high frequency current to concentrate on the outside of the conductor. To address this, a conductor diameter smaller than the skin depth at the given frequency must be chosen. This led to the choice of litz wire consisting of 400 insulated strands for the conductor. The radiation resistance insulation ethylene tetrafluoroethylene (ETFE) was chosen for these conductors and a 3D printed polyethylene sulfide (PPS) will be used for the coil bobbins. The effects of eddy currents were eliminated from the core material by choosing ferrite, an amorphous material consisting of iron-oxide crystals. Simulations were completed to ensure a homogenous magnetic field in the region of the beam, and the subsequent pole profile was determined. Lastly, a metalized ceramic beampipe is used to integrate with the existing beamline and allow for discharge of any static buildup on the inner surface of the beampipe due to the electron beam. / Graduate

Radioactive isotopes enable advanced medical treatments and the study of nuclear structure, nuclear astrophysics, and fundamental symmetries. TRIUMF, Canada’s Particle Accelerator Centre, generates radioactive isotope beams using the Isotope Separation On-Line method. At TRIUMF, the Forced Electron Beam Induced Arc Discharge (FEBIAD) ion source is used to ionize specific isotopes but often presents limited performance and lower efficiencies compared to other facilities. To investigate the source limitation, elucidate the ionization mechanism, and propose improved and highly efficient sources for upcoming facilities, a combined numerical and experimental campaign has been undertaken. The developed numerical ionization model is able to describe the source as an electron impact ion source that is governed by strong space charge effects. The spatially distributed ionization rate is higher at specific locations of the anode volume, and this has been confirmed experimentally. The validated numerical model has been further used to propose simulation-based optimizations. With the overall optimization, the ionization efficiency for the TRIUMF FEBIAD is expected to increase ten-fold. / Graduate

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The optical design of the TRIUMF Second Arm Spectrometer (SASP) has been completed and the engineering design started. The effects of the dipole shape and field clamps on the aperture fringe fields were studied. It was determined that a field clamp would be necessary to achieve the field specifications over the desired range of dipole excitations. A specification of the dipole pole edges and field clamps for the SASP is made. A Monte Carlo simulator for the SASP was written. During the design this was used to study the profiles of rays passing through the SASP. These profiles were used in determining the positioning of the dipole vacuum boxes and the SASP detector arrays. The simulator is intended to assess experimental arrangements of the SASP. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The TRIUMF view screen system encompases a set of devices which individually image, and produce measurements of, the transverse profile of an accelerated electron beam. A control system is an essential component of the overall diagnostic device. The system requirements were compiled from those produced by the TRIUMF laboratory and from those based on the needs of the individual diagnostic devices. Based on the requirements, a control system was designed and implemented with a combination of industrial electrical and mechanical hardware, and a variety of software components. One component of the image reconstruction algorithm was validated with experimental data; the accuracy and precision of beam profile measurements was evaluated through simulation studies. Although it was not possible to demonstrate the satisfaction of requirements relating to alignment, it was shown that all other requirements were satisfied. / Graduate / 0798 / 0752 / 0605

<p> In nuclear astrophysics, there are still undiscovered areas involving unstable nuclei, like the nucleosynthesis in exploding stars. The unstable nuclei are extremely difficult to produce in the laboratory for study since they decay away quickly once they are formed. To make the unstable nuclei available in the laboratory, Canada has built one of the best facilities in the world for nuclear astrophysics studies with radioactive beams, called TRIUMF-ISAC. Its recent upgrade to ISAC-2 can produce even heavier radioactive beams with higher energy. To fully utilize the ISAC-2 facility, a high-segmented HPGe γ-ray detector-TIGRESS, has been developed to study exotic nuclei using the well-established technique of Coulomb Excitation.</p> <p> As an essential part of the TIGRESS facility, auxiliary detectors, such as silicon detectors, are used to improve the sensitivity of the experiments through Doppler correction. Two types of silicon detectors will be used. One is the CD-shaped double-sided silicon strip detector, which is the topic of this thesis. The other one is the silicon barrel detector. This thesis will discuss the computer simulations and experimental tests of the CD detector.</p> <p> Simulations were made using a simulation toolkit GEANT4, which was run under the Linux system. The goal was to test the hypothesis that measurements of the energies of heavy ions in Coulomb excitation may improve the Doppler correction by constraining the scattering location in a thick target. To test the performance of the simulated CD detector, simple simulations were performed for shooting calibration alpha particles from an 241Am source first directly onto the CD and second through a thin target onto the CD. The goal of additional simulations was to attempt to determine the corresponding scattering depth in a thick target by putting an energy cut on the spectrum of the scattered beam detected in the CD. These simulation results verify the possibility of such localization, though the resolution is not very good.</p> <p> Experimental tests for the CD detector are aimed to obtain the energy resolution for each strip element of the CD and to have at least 8 channels instrumented in our test lab before this detector is sent to TIGRESS facility. The test station including electronics and detector systems and all results from initial tests are described in detail in this thesis.</p> / Thesis / Master of Science (MSc)

Precision measurements of superallowed Fermi β-decay allow for stringent tests of the magnitude of isospin-symmetry-breaking effects in nuclei, the validity of the conserved vector current hypothesis, and the unitarity of the Cabibbo-Kobayashi-Maskawa (CKM) quark-mixing matrix. A high-precision measurement of the branching ratio for the superallowed β+ decay of 74Rb has been performed at the Isotope Separator and ACcelerator (ISAC) facility at TRIUMF. The 8π spectrometer, an array of 20 HPGe detectors, was used to detect γ-rays emitted following the Gamow-Teller and non-analogue Fermi β-decays of 74Rb. PACES, an array of 5 Si(Li) detectors, was used to detect emitted conversion electrons, while half of SCEPTAR, a close-packed array of 10 plastic scintillators, was used to detect emitted β particles. In this experiment, 23 excited states were identified in 74Kr which were populated following the β-decay of 74Rb. A total of 58 γ-rays were identified following the 8.241(4)x108 detected β-particles. An observed non-superallowed branching ratio of 0.396(7)% was determined from the intensity of the identified γ-rays, while the unobserved non-superallowed intensity was calculated to be 0.05(5)%, leading to a superallowed branching ratio of 99.55(5)%. The superallowed branching ratio is now the most precise experimental quantity in the determination of the superallowed ft-value of 74Rb. Combining the half-life and Q-value with the superallowed branching ratio measured in this work leads to a superallowed ft-value of 3082.6(66) s. Finally, comparisons between the superallowed ft-value, the world average Ft-value, and the non-analogue Fermi branching ratio are made to provide future guidance in the refinement of the theoretical models required to describe the crucial isospin-symmetry-breaking term in superallowed β-decay.