Thesis (MEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Superconducting QUantum Interference Devices (SQUIDs) are fairly recent types of magnetometers that use flux quantization combined with Josephson tunnelling to detect very faint (< 10¯15 T) magnetic fields. Recent scientific studies have shown that these highly sensitive magnetometers, located in an ultra-low-noise environment, are capable of observing Earth-ionosphere couplings, such as P waves emitted during earthquakes or magnetic storms in the upper atmosphere, S and T breathing modes of the Earth during quiet magnetic and seismic periods, signals in time correlating with sprites. Since SQUIDs are much more sensitive than conventional magnetometers, they are arguably the best tool for understanding space weather and natural hazards, whether they are produced from space or within the ionosphere by magnetic storms for instance, or natural disturbances, including magnetic disturbances produced by earthquakes or as a result of the dynamics of the earth's core. A study was conducted at SANSA Space Science in Hermanus, Western Cape, in 2012, to find the correlation between SQUID and Fluxgate data-sets, with the aim of validating the use of a SQUID as a reliable instrument for Space Weather observations. In that study, SQUID data obtained from the Low Noise Laboratory (LSBB) in France was compared to Fluxgate data-sets from the three closest magnetic observatories to LSBB, namely Chambon la For êt (France), Ebro (Spain) and Fürstenfeldbruck (Germany), all further than 500 km from LSBB. As a follow-up study, our aim is to correlate the SANSA Space Science SQUID data at Hermanus with Fluxgate magnetic data also recorded on-site (at Hermanus). There are notable di_erences between the previous study and the current study. In the previous study, the three-axis SQUID used comprised of three low-Tc devices operated in liquid helium (4.2 K) in an underground, low noise environment shielded from most human interferences. The SQUID magnetometer operated at Hermanus for the duration of this study is a high-Tc two-axis device (measuring the x and z components of the geomagnetic field). This SQUID magnetometer operates in liquid nitrogen (77 K), and is completely unshielded in the local geomagnetic field of about 26 uT. The environment is magnetically clean to observatory standards, but experiences more human interference than that at LSBB. The high-Tc SQUIDs also experience excessive 1/f noise at low frequencies which the low-Tc SQUIDs do not suffer from, but the big advantage of the current study is that the SQUIDs are located within 50 m from the observatory's fluxgate. We thus expect far better correlation between SQUID and fluxgate data than what was obtained in the previous study, which should improve the isolation of signals detected by the SQUID but not by the fluxgate. / AFRIKAANSE OPSOMMING: SQUIDs (supergeleidende kwantuminterferensietoestelle) is redelik onlangse tipes magnetometers wat vloedkwantisering saam met Josephson-tonneling gebruik om baie klein (< 10¯15 T) magnetiese velde waar te neem. Onlangse wetenskaplike studies het getoon dat hierdie hoogs sensitiewe magnetometers die vermoë het om Aarde-ionosfeerkoppeling waar te neem wanneer dit in 'n ultra-laeruisomgewing geplaas word. Sodanige koppeling sluit in: P-golwe wat deur aardbewings or magnetiese storms in die boonste atmosfeer veroorsaak word; S- en T-asemhalingsmodusse van die Aarde gedurende stil magnetiese en seismiese periodes; en seine in tyd wat korreleer met weerligeffekte in die boonste atmosfeer. Aangesien SQUIDs heelwat meer sensistief is as konvensionele magnetometers, is dit moontlik die beste gereedskap om ruimteweer en geassosieerde natuurlike gevare mee te analiseer; hetsy sulke toestande veroorsaak word vanaf die ruimte (deur die son) of binne die ionosfeer deur magnetiese storms of natuurlike steurings wat deur aardbewings of die dinamika van die Aardkern veroorsaak word. 'n Studie is in 2012 gedoen by SANSA Space Science in Hermanus in die Wes-Kaap om die korrelasie tussen SQUID- en vloedhekdatastelle te vind met die doel om SQUIDs as betroubare instrumente vir ruimteweerwaarneming te bevestig. In daardie studie is SQUID-data verkry vanaf die Laeruis Ondergrondse Laboratorium (LSBB) in Frankryk, en is dit vergelyk met vloedhekdatastelle vanaf die drie naaste magnetiese observatoriums aan LSBB, naamlik: Chambon la Forêt (Frankryk), Ebro (Spanje) en Fürstenfeldbruck (Duitsland). Al drie hierdie observatoriums is verder as 500 km vanaf LSBB. As 'n opvolgstudie is ons doelwit om SQUID- en vloedhekdata wat beide op die terrein van SANSA Space Science in Hermanus waargeneem word, te korreleer. Daar is merkbare verskille tussen hierdie en die vorige studies. In die vorige studie is 'n drie-as lae-Tc SQUID-magnetometer in vloeibare helium (4.2 K) in 'n laeruis ondergrondse laboratorium, afgeskerm teen menslike steurings, gebruik. Die SQUID-magnetometer wat vir die duur van die huidige studie by Hermanus gebruik is, is 'n hoë-Tc twee-as toestel (wat die x - en z -komponente van die geomagnetiese veld meet). Hierdie SQUID-magnetometer opereer in vloeibare stikstof teen 77 K, sonder enige afskerming in die geomagnetiese veld van ongeveer 26 uT. Die omgewing is magneties skoon volgens observatoriumstandaarde, maar ondervind meer menslik-veroorsaakde steurings as LSBB. Die hoë-Tc SQUIDs tel ook heelwat 1/f ruis op (wat lae-frekwensiemetings beïnvloed); iets wat nie 'n rol speel by die lae-Tc SQUIDs nie. Die groot voordeel van die huidige studie is dat die SQUIDs binne 50 meter vanaf die observatorium vloedhekke geleë is. Ons verwag dus heelwat beter korrelasie tussen SQUID- en vloedhekdata as wat met die vorige studie verkry is, wat dit makliker sal maak om die isolasie te verbeter van seine wat deur die SQUIDs waargeneem is, maar nie deur die vloedhekke nie.

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The eastern branch of the late Proterozoic Damara Orogenic Belt of central Namibia hosts various copper, gold, manganese and uranium deposits, but in the vicinity of Steinhausen, approximately 145 km northeast of Windhoek, the Damara Belt becomes increasingly covered by recent Kalahari cover sediments resulting in little known geology and subsequent lack of discovered economic mineral deposits. Airborne magnetic and radiometric data over the Steinhausen Study Area was enhanced through image processing and filtering to accentuate characteristics of subsurface geology that, by comparing these characteristics to known geology, aided in the interpretive mapping of lithology, structure and targets for follow-up exploration. As a result, some important observations regarding the regional lithology can be drawn. An arenaceous stratigraphic unit that includes a coarse grained, glassy quartzite below the Kuiseb Formation equates to either the eastern Damaran equivalent of the Nosib Group subjected to high grade metamorphism or, alternatively, the upper part of the pre-Damaran sequence, immediately underlying the Damara. The Kuiseb Formation within the study area is uncharacteristically varied as compared to the same formation further west along the Damaran Orogen and can be subdivided into 5 separate units based on geophysical signature. Structural features evident within the study area include the prominent Kudu and Okahandja Lineaments and straddle an area of inferred uplifted stratigraphy of possibly pre-Damara age. The Ekuja Dome (Kibaran age and host to the Omitiomire copper deposit) is also clearly discernible on the airborne magnetic data and is cross-cut by an east-northeast structural zone. Direct targets for follow-up exploration include the Rodenbeck intrusion, anomalous magnetic bodies and numerous radiometric anomalies present within the study area. Identified dome-like features are considered prospective for Omitiomire-style deposits and the Okatjuru Layered Complex is considered a possible source of copper, chromite, magnetite, ilmenite, nickel and the platinum group elements.

Optical fiber magnetometers are extremely sensitive devices which are capable of competing with magnetometers implemented using other technologies. Demodulation of the signals detected using these magnetometers can be performed using either homodyne or heterodyne techniques. Higher sensitivities have been achieved using homodyne rather than heterodyne techniques, but with homodyne demodulation there exists the inherent problem of quadrature-point stabilization. Presented here is a review of existing quadrature-point stabilization methods and experimental results concerning the application of one of them which uses a piezoelectric transducer in the reference arm of an all-fiber Mach-Zehnder interferometer. / Master of Science

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No description available.

Thesis (MScEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: This work discusses the design of a 3-axis Geomagnetometer SQUID System (GSS), in which HTS SQUIDs are used unshielded. The initial GSS installed at SANSA was fully operable, however the LN2 evaporation rate and SQUID orientation required improving. Magnetic shields were also developed in case the SQUIDs would not operate unshielded and to test the system noise with geomagnetic variations removed. To enable removing the double layer shield from the probes while the SQUIDs remain submerged in LN2, the shield was designed to disassemble. The shields proved to be effective, however due to icing the shields could not be removed without removing the SQUIDs from the LN2. / AFRIKAANSE OPSOMMING: Hierdie werk bespreek die ontwerp van 'n 3-as Geomagnetometer SQUID Sisteem (GSS), waarin HTS SQUIDs sonder magnetiese skilde aangedryf word. Die aanvanklike GSS geïnstalleer by SANSA was ten volle binnewerking, maar die LN2 verdamping en SQUID oriëntasie benodig verbetering. Magnetiese skilde was ook ontwikkel vir die geval dat die SQUIDs nie sonder skilde wou werk nie en om die ruis te toets na geomagnetiese variasies verwyder is. Die dubbele laag skild was ontwerp om uitmekaar gehaal te word terwyl die SQUIDs binne die LN2 bly. Die skild was doeltreffend, maar ys het verhoed dat die skild verwyder kon word vanaf die LN2 sonder om die SQUIDs ook te verwyder.

Made available in DSpace on 2014-10-09T12:45:30Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:56:26Z (GMT). No. of bitstreams: 1 07175.pdf: 4800774 bytes, checksum: 7591ed2b66c61d81600006d10b99afb7 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Made available in DSpace on 2014-10-09T12:45:30Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:56:26Z (GMT). No. of bitstreams: 1 07175.pdf: 4800774 bytes, checksum: 7591ed2b66c61d81600006d10b99afb7 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Assessing the quality of fruit has become vitally important for farmers and growers. With retailers placing ever stricter requirements on fresh produce, growers have to spend a greater amount of time and effort sorting and grading their harvest. Increasingly, vendors are placing requirements not only on external factors like colour, and firmness, but on internal quality factors such as sugar content and acidity, because, although consumers buy fruit based on their external appearances, the taste of the fruit is what determines whether the consumer will buy again. Different techniques exist that probe the internal quality of fruit non-destructively. The technique most widely used today is Near Infrared Spectroscopy. This technique is powerful, but has certain limitations such as poor reliability and the need for constant recalibration. This thesis suggests an alternative method for evaluating internal fruit quality based on low-field nuclear magnetic resonance detected by superconducting quantum interference devices. It introduces the theory of SQUIDs and NMR, and evaluates the use of SQUID detected NMR spectroscopy as a method for determining the internal quality of fruit. The fabrication techniques and processes are explained in detail and a design for a SQUID detected NMR spectrometer is given. Relevant simulations and simulation results are also given. No working SQUID could be fabricated and, as such, no working NMR spectrometer was demonstrated. This thesis serves as a reference work for future research. / AFRIKAANSE OPSOMMING: Bepaling van die gehalte van vrugte het vir boere uiters belangrik geword. Met kleinhandelaars wat al strenger vereistes plaas op vars produkte moet boere meer tyd en inspanning bestee met die sortering en gradering van hul oes. Handelaars plaas nie net vereistes op eksterne kwaliteitsfaktore soos kleur en fermheid nie, maar begin al hoe strenger vereistes plaas op interne kwaliteitsfaktore soos suikerinhoud en suurgehalte, want, hoewel verbruikers vrugte koop op grond van hul eksterne kwaliteitsfaktore, is dit die smaak van die vrug wat bepaal of die verbruiker weer die vrug sal koop. Verskillende tegnieke bestaan wat die interne kwaliteit van vrugte op ’n nie-destruktiewe manier kan bepaal. Die mees algemene tegniek is Naby Infrarooi Spektroskopie. Hierdie tegniek is kragtig maar het sekere beperkings soos swak betroubaarheid en die noodsaaklikheid van konstante herkalibrasie. Hierdie tesis stel ’n alternatiewe metode vir die evaluering van interne vrugkwaliteit gebaseer op lae-veld kernmagnetiese resonans waargeneem deur supergeleidende kwantum inmenging toestelle voor. Dit stel die teorie van SKWITs en KMR bekend, en evalueer die gebruik van SKWIT-bespeurde KMR spektroskopie as ’n metode vir die bepaling van die interne kwaliteit van vrugte. Die fabrikasie tegnieke en prosesse word in detail verduidelik en ’n ontwerp vir ’n SWKIT opgevangde KMR spektrometer word gegee. Toepaslike simulasies en simulasie resultate word ook gegee. Geen werkende SKWIT kon vervaardig word nie en as gevolg daarvan kon geen werkende KMR spektrometer gedemonstreer word nie. Hierdie tesis dien as ’n naslaan werk vir toekomstige navorsing.