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Thesis (MSc)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Nine 100x100x600 mm3 plastic scintillators, formerly built for the neutron time of ight measurements at iThemba LABS, were refurbished. The position resolution of these detectors was determined using muon cosmic rays and coincident measurement techniques. Average position resolution of 4.28 cm (FWHM) was found. In order to predict the time spectrum of the large-volume detector Monte Carlo simulations have been performed. These simulations aimed at anticipating the separation of statistical neutrons, prompt gamma rays and uncorrelated gamma rays from the fast neutrons emitted in the reaction of interest. One of the neutron detectors was tested using fast neutrons from the 232Th( ,xn) reaction at 42 MeV. Statistical neutrons from fusion evaporation reactions were produced in 152Sm(12C,xn) fusion evaporation reaction. Coincidences between neutrons and gamma rays were successfully identi ed. Prompt gamma rays and uncorrelated gamma rays were also identi ed. / AFRIKAANSE OPSOMMING: Nege 100x100x600 mm3 plastiese scintillators, wat aanvanklik gebou was vir neutron vlugtyds meetings by iThemba LABS, was hernu. Die posisie resolusie van die detektore was bepaal deurmiddel van muon kosmiese straling en koïnsidensie meet tegnieke. Posisie resolusie van 4.28 cm (FWHM) was verkry. Monte Carlo simulasies is gebruik om die posisie resolusie van'n groot volume detektor te voorspel. Hierdie simulasies is daarop gemik om onderskeid te maak tussen statistiese neutrone, gelyktydige gamma strale en ongekorreleerde gamma strale vanaf vinnige neutrone in die reaksie van belang uitgestraal word. Een neutron detektor was getoets deur gebruik te maak van vinnige neutrone wat uit die reaksie 232Th( ,xn) by 42 MeV ontstaan. Statistiese neutrone vanaf splitsings verdampingsreaksies, gelyktydige gamma strale en ongekorreleerde gamma strale was geidenti seer. Statistiese neutrone van samesmelting verdamping reaksies was geproduseer in die reaksie 152Sm(12C,xn). Toeval tussen neutrone en gamma strale was suksesvol geïdenti seer, gevra gamma strale en ongekorreleerd gamma strale was ook geïdenti seer.

<p>This thesis is based on a selection of six different experimental techniques used for studies in atomic and molecular physics. The techniques analysed in the thesis are compared to find similarities in strategies and ways to avoid sources of error.</p><p>Paper 1 deals with collision based spectroscopy with 60 keV Xe6+ ions on sodium and argon gas targets. Information on energy of Rydberg states in Xe5+ is unveiled by optical spectroscopy in the wavelength range from vacuum ultraviolet (VUV) to visible. In paper 2, the fast ion-beam laser spectroscopy (FIBLAS) is adapted for measuring hyperfine structure of barium isotopes in an isotopically pure ion-beam. This techniques involves changing the isotope during the measurement to minimize sources of error in measurement and enhance the signal from lesser abundant isotopes. The FIBLAS technique is used in paper 3 to study samarium ions. The ions are optically pumped and the recorded optical nutation is used to measure transition probabilities. This technique eludes the difficulties inherent in relative intensity measurements of all the radiative transitions from an excited state. In Paper 4, optical emission spectroscopy is used in the VUV region to study noble gas mixture discharges. The source of the emission bands near the resonance lines of krypton and xenon are found to be heteronuclear dimers. In paper 5, radiation from a pulsed argon plasma with admixture of nitrogen is studied with time resolved spectroscopy in the VUV and ultraviolet wavelength ranges to investigate the mechanism of energy transport. A metastable state of atomic argon is found to be an important source of energy to many radiative processes. In Paper 6, photoelectron spectroscopy (PES) on thiophene, on 3-bromothiophene and on 3,4-dibromothiophene using time-of-flight photoelectron-photoelectron coincidence technique and conventional PES to investigate the onset of double ionisation compared to the onset of single ionisation in molecules.</p>

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In some medical cases it is of interest to study a persons gait. This can be done in several different ways, both simple and advanced. A project has been done at the department Medicinsk Teknik - Forskning och Utveckling at the University Hospital of Umeå. In that project a system with optical triangulation sensors was created to easily measure a persons step width and step height. It was found that the sensors had limitations, in particular with sample frequency, and it was therfore of interest to test new sensors for this application. The goal with this project was to evaluate two sensors, VL53L0X and VL6180, and investigate if they can be used to measure step width and step hight. A system was built to communicate with and read data from the sensors. The sensors were then tested both in a laborative and real environment. With good reflection both VL6180 and VL53L0X show good precision in the range of interest. The sensors has the resolution of millimeters. VL6180 works better at really close distances but has a much shorter maximum range, about 18 cm, and lower maximum sample frequency, under 43 Hz. VL53L0X was tested up to 70 cm and 50 Hz. To be able to measure step width from the ankle, a very high sample frequency is needed to get the right amount of data when the legs pass eachother. If the sensors can be used in that way has not been confirmed. When placed higher on the persons leg, VL6180 can be used to measure step width and VL53L0X can be used to measure both step width and step height. / Inom sjukvården kan det i vissa fall vara intressant att studera en persons gång. Detta kan göras mer eller mindre avancerat och av olika anledningar som för diagnostik eller uppföljning efter ingrepp. Det har tidigare skapats ett mätsystem för mätning av gångparametrar på avdelningen Medicinsk teknik - Forskning och Utveckling vid Norrlands Universitetssjukhus. I det arbetet testades optiska sensorer som använder en triangulerande metodik. Den existerande tekniken hade dock begränsningar i sitt mätutförande vilket ledde till ett behov av att ersätta dessa med en ny typ av sensor. Målet med det här arbetet var därför att utvärdera två andra sensorer, VL6180 och VL53L0X, och undersöka om de kan användas för mätning av stegbredd och steghöjd. Ett mätsystem skapades i för att kommunicera med och samla in data från sensorerna. Därefter utfördes tester, främst laborativa tester med även ett test med den ena sensorn i reell miljö på testperson. Båda sensorerna visar på bra precision och linjäritet på de intressanta avstånden och ger resultat med en upplösning på hela millimetrar. VL6180 opererar bättre på väldigt nära håll men har en begränsning i att det maximala mätavståndet ligger kring 18 cm och den maximala samplingsfrekvensen under 43 Hz. Den frekvensen går att programmera men är instabil. För att kunna placera sensorerna nere vid vristen vid breddmätning krävs en mycket hög samplingsfrekvens för att få in tillräckligt med mätdata. VL53L0X kan komma upp i en en samplingsfrekvens på 50 Hz men det på bekostnad av sämre precision än vid lägre frekvenser. Huruvida VL6180 och/eller VL53L0X kan placeras vid vristen har inte bekräftats. VL53L0X testades med testperson och fungerade då för höjdmätning och breddmätning vid vaden. VL6180 bedöms kunna användas som sensor för mätning av stegbredd och VL53L0X för mätning av stegbredd och steghöjd.

Les accélérateurs d’ions lourds sont un outil incontournable pour la recherche en physique nucléaire. Ils sont également utilisés pour diverses applications. Il est nécessaire de caractériser la production des neutrons secondaires dans les accélérateurs afin de garantir un fonctionnement sûr en toutes circonstances. Cependant, les données expérimentales sont très rares voire inexistantes. Pour certaines données, on note des divergences entre différentes publications. Des désaccords sont aussi observés entre les mesures et les calculs. Toutes ces raisons justifient le programme Thick Target Neutron Yields (TTNY) dont l’objectif est de mesurer des spectres doublement différentiels (énergie, angle) des neutrons générés par l’interaction des ions lourds (12≤Afaisceau≤208 et 4,6 MeV/nucléon≤Efaisceau≤95 MeV/nucléon) sur cibles épaisses (natC, natCu et natNb). Deux techniques de mesure ont été utilisées : Activation et Temps de vol. Cela permet d’avoir une meilleure confiance dans les mesures, d’étudier les limites expérimentales et de consolider les conclusions que l’on peut en tirer. Les mesures sont comparées à des simulations effectuées dans ce travail avec les codes Monte-Carlo les plus utilisés en calcul nucléaires : PHITS (japonais), FLUKA (européen (CERN/INFN)) et MCNP (américain). Ces comparaisons ont permis d’évaluer la qualité des codes dans les énergies étudiées et pour les masses des noyaux explorées. Elles ont permis aussi de conclure sur les incertitudes systématiques et les éventuelles évolutions à apporter aux modèles physiques de ces codes. / Heavy-ion accelerators are an essential tool for nuclear physics research. They are also adopted in several applications. It is necessary to characterize the secondary neutrons production in order to guarantee a safe operation in every circumstance in accelerators. However, experimental data are very rare or even non-existent. For some data, we notice disagreements between different publications. Disagreements are also observed between measurements data and simulations. For all these reasons, we established the program Thick Target Neutron Yields (TTNY). This program aims to measure the double differential neutron spectra (energy, angle) generated by the interactions of heavy-ions (12≤Abeam≤208 and 4.6 MeV/nucleon≤Ebeam≤95 MeV/nucleon) on thick targets (natC, natCu and natNb). Two measurements methods were adopted: Activation and Time of Flight. This choice allows having a better confidence on the measurements, studying experimental limits and consolidating the conclusions that could be drawn from the experimental results. The measurements are compared to the simulations performed with some Monte-Carlo widely used in nuclear simulation: PHITS (Japanese), FLUKA (European (CERN/INFN)) and MCNP (American). These comparisons allowed evaluating the modeling quality of heavy-ion reactions for the energies and masses explored in this work. We also conclude on the systematic uncertainties and on the potential improvements to be introduced to physics models of these codes.

Chan Pui Kwan. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references (leaves 98-104). / Abstracts in English and Chinese. / TABLE OF CONTENTS --- p.i / LIST OF FIGURES --- p.iv / LIST OF TABLES --- p.vii / ABBREVIATIONS --- p.viii / Chapter Chapter one --- Research Background / Chapter 1.1 --- Carbohydrates --- p.2 / Chapter 1.2 --- Impact of molecular weight of polysaccharides --- p.5 / Chapter 1.3 --- Molecular Weight Determination of polysaccharides --- p.6 / Chapter 1.3.1 --- Laser Scattering --- p.6 / Chapter 1.3.2 --- Gel Permeation Chromatography --- p.7 / Chapter 1.3.3 --- Mass spectrometry --- p.9 / Chapter 1.4 --- Matrix assisted laser desorption/ ionization (MALDI) --- p.10 / Chapter 1.4.1 --- Laser desorption --- p.10 / Chapter 1.4.2 --- Matrix-assisted laser desorption / ionization (MALDI) --- p.11 / Chapter 1.5 --- MALDI-TOFMS analysis of polymers --- p.14 / Chapter 1.6 --- Outline of the present work --- p.16 / Chapter Chapter two --- Experimental and Instrumentation / Chapter 2.1 --- Matrix-assisted laser desorption/ ionization Time of flight Mass Spectrometry (MALDI-TOFMS) --- p.18 / Chapter 2.2 --- Delayed extraction --- p.20 / Chapter 2.3 --- Time of flight mass spectrometry (TOFMS) --- p.20 / Chapter 2.3.1 --- Linear time-of-flight mass spectrometry --- p.20 / Chapter 2.3.2 --- Reflectron --- p.21 / Chapter 2.4 --- Instrumentation --- p.23 / Chapter 2.4.1 --- Laser system --- p.24 / Chapter 2.4.2 --- Ion source --- p.26 / Chapter 2.4.3 --- Ion deflection --- p.26 / Chapter 2.4.4 --- Detection --- p.27 / Chapter 2.4.5 --- Reflector --- p.27 / Chapter 2.4.6 --- Data acquisition --- p.29 / Chapter 2.5 --- Experimental --- p.29 / Chapter 2.5.1 --- Sample preparation --- p.29 / Chapter 2.5.2 --- Calibration --- p.33 / Chapter 2.6 --- Data analysis --- p.33 / Chapter Chapter three --- Use of ammonium fluoride as co-matrix / Chapter 3.1 --- Introduction --- p.35 / Chapter 3.2 --- Results and discussion --- p.37 / Chapter 3.2.1 --- Effect of co-matrix --- p.45 / Chapter 3.2.2 --- Effect of sample preparation --- p.49 / Chapter 3.2.3 --- Analysis of dispersed dextran --- p.52 / Chapter 3.3 --- Conclusion --- p.55 / Chapter Chapter four --- Effect of sample preparation / Chapter 4.1 --- Introduction --- p.57 / Chapter 4.2 --- Experimental --- p.57 / Chapter 4.2.1 --- Sample preparation --- p.57 / Chapter 4.3 --- Results and discussion --- p.59 / Chapter 4.4 --- Conclusion --- p.71 / Chapter Chapter five --- Development of liquid matrix systems / Chapter 5.1 --- Introduction --- p.73 / Chapter 5.2 --- Experimental --- p.75 / Chapter 5.2.1 --- Sample preparation --- p.75 / Chapter 5.3 --- Results and discussion --- p.76 / Chapter 5.3.1 --- Formulation of matrix solutions --- p.76 / Chapter 5.3.2 --- Use of liquid matrix system --- p.87 / Chapter 5.3.3 --- Analysis of dispersed dextran --- p.90 / Chapter 5.4 --- Conclusion --- p.93 / Chapter Chapter six --- Conclusion / Chapter 6.1 --- Conclusion --- p.95 / References --- p.98 / Appendix / Appendix 1 Chemical structure of matrices / Appendix 2 Chemical structure of solubilizing agents / Appendix 3 Chemical structure of liquid supports / Appendix 4 Chemical structure of additives

Ce travail présente l'étude de faisabilité des mesures de transmission avec des échantillons MINERVE à l'installation de temps de vol GELINA. L'idée principale était de définir des procédures pour analyser les résultats des mesures de transmission réalisées avec des échantillons cylindriques ne répondant pas à la géométrie de transmission idéale. La capacité d'extraire des résultats fiables a été démontrée sur l'exemple des échantillons MINERVE enrichis en argent. De plus, des mesures de transmission et de capture avec des disques standards d'argent naturel ont été effectuées pour améliorer les paramètres de résonance pour 107Ag et 109Ag. Les principales étapes de ce travail sont la réduction des données brutes (taux de comptage) pour produire des spectres de transmission et de rendement de capture, puis l'analyse des spectres avec le code d'analyse de forme des résonances REFIT. / This work presents the feasibility study of transmission measurements with the MINERVE samples at time-of-flight facility GELINA. The main idea was to define procedures to analyse results of transmission measurements using cylindrical samples which do not fulfil the ideal transmission geometry. Capability of extracting reliable results was demonstrated on the example of MINERVE samples enriched in silver. In addition, transmission and capture measurements with standard discs of natural silver were performed to improve the resonance parameters for 107Ag and 109Ag. The main steps in this work are the data reduction of measured count rate spectra to produce final transmission and capture yield spectra and the spectra analysis with the resonance shape analysis code REFIT.

The use of short columns, higher carrier gas velocity and fast temperature programs in Comprehensive Two-Dimensional Gas Chromatography coupled to Time-of- Flight Mass Spectrometry (GC x GC/TOFMS) technique is expected to increase the speed of analysis up to several orders of magnitude when compared to conventional gas chromatography (GC) or gas chromatography/mass spectrometry (GC/MS). A systematic evaluation of the GC x GC/TOFMS configuration for high-speed applications has received little attention in the literature. The feasibility of High Speed Comprehensive Two-Dimensional Gas Chromatography coupled to Mass Spectrometry (High speed GC x GC/MS) for complex mixtures has been investigated in this thesis. A particular focus was placed on comparing conventional scanning quadrupole mass spectrometry (qMS) with a newly available non-scanning time-of-flight instruments (TOFMS). Experiments were carried out using GC/qMS, GC x GC/qMS, GC/TOFMS and GC x GC/TOFMS both in normal (slow) and fast temperature rates coupled with high frequency modulation in GC x GC. Initially a complex mixture consists of 24 semivolatile compounds was used as the analyte for the above purpose. In the initial experiments parameters like acquisition rate and duty cycle for qMS were determined to evaluate the effectiveness of the instrument for fast analysis. The practical duty cycle value obtained for the qMS was only about 18 % for single ion and one compound at a dwell time of 10 ms in SIM mode. In both high-speed GC/qMS and high-speed GC x GC/qMS techniques only about 40 % of the components in the complex mixture were found to be well separated. The acquisition rate of scanning instruments like qMS is incompatible for fast eluting peaks in high speed GC. TOFMS that has an acquisition rate of several hundred spectra per second offer the potential to define the fast GC peaks accurately. The high quality spectra from TOFMS also enable deconvolution of coeluting peaks in the complex mixtures. The advantage of the automated spectral deconvolution is demonstrated for the identification of the coeluting peaks in the complex mixtures. Coelution of peaks is also observed with highspeed GC/TOFMS technique. The high-speed GC x GC/TOFMS was also tested with two different analyte system ??? A pesticide mixture and platformate (an aromatic mixture) to evaluate the suitability for high-speed analysis of complex mixtures. A poor resolution was observed for the pesticide mixture in the two-dimensional plane and it appeared, as there was nearly no orthogonal separation in the second dimension. The platformate mixture displayed a better two-dimensional separation. Chromatographic peak resolution is not really a primary requirement for locating and identifying the coeluting compounds in high-speed GC x GC/TOFMS technique. However, it was observed that the high-speed GC x GC/TOFMS too faced problem to unscramble the mass spectra of those compounds with similar structure and sharing the same unique masses.