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PERFORMANCE ANALYSIS of LOW TEMPERATURE SUPERCONDUCTING FLUX PUMP Researched at SRON Groningen, the Netherlands

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PERFORMANCE ANALYSIS of LOW TEMPERATURE SUPERCONDUCTING FLUX PUMP Researched at SRON Groningen, the Netherlands Bachelors Thesis in Applied Physics PERFORMANCE ANALYSIS OF LOW TEMPERATURE SUPERCONDUCTING FLUX PUMP Researched at SRON Groningen, the Netherlands July, 2017 James Robert Lyon, S2709821 [email protected] / (+31)619671537 Faculty of Science and Engineering University of Groningen Supervised by dr. ir. G. de Lange (SRON) prof. dr. ir. C.H. van der Wal (RUG) prof. dr. T. Banerjee (RUG) 1 [This page intentionally left blank] 2 Abstract A flux pump system uses a small alternating current to build up a large current inside a superconducting load coil. An experimental prototype has been built for the purpose of analysing its performance, including its stability, reliability and limiting, for possible satellite application at SRON. The flux pump circuit is a developing project previously worked upon by two other Bachelor students. The operation of the full wave transformer rectifier flux pump is described and analysed. The experimental set-up was rebuilt, measurement methods were developed and sensors were calibrated. The optimal primary wave for this device was experimentally determined to have a frequency of 0.1667 Hz and amplitude of 250 mA from which an exponential increase was observed and a maximum output of approximately 7 A was achieved. However, it proved to be an unreliable system as repeated experiments provided inconsistent results due to suspected short circuiting of inductors. Moreover, the power and efficiency of the system is analysed and is in good agreement with theoretical predications. The flux pump has a maximum efficiency of 80% at a normalised current of 0.2. 3 Contents Abstract ................................................................................................................................................................................. 3 Acknowledgments ................................................................................................................................................................ 6 Layout of this Report ............................................................................................................................................................ 8 1 Introduction ....................................................................................................................................................................... 9 1.1 Background Information ............................................................................................................................................ 9 1.2 Research Aims .......................................................................................................................................................... 10 Aim 1: Improve the sensing element for measuring the load coil current ................................................................. 10 Aim 2: Determine the optimal primary wave for charging ........................................................................................ 10 Aim 3: Measuring the load coil current until saturation ............................................................................................ 10 Aim 4: Perform a power and efficiency analysis on the flux pump circuit ................................................................ 10 1.3 About SRON ............................................................................................................................................................ 11 1.4 Why SRON are interested in flux pump system ....................................................................................................... 11 1.5 About the SPICA/ SAFARI Mission ........................................................................................................................ 11 2 Theoretical Background ................................................................................................................................................... 13 2.1 General Physics Concepts ........................................................................................................................................ 13 2.1.1 Superconductivity ............................................................................................................................................. 13 2.1.2 Mutual Inductance of a Coil Wrapped Around a Solenoid ............................................................................... 13 2.1.3 Superconducting Magnets ................................................................................................................................. 14 2.1.4 Magnetic Quenching ......................................................................................................................................... 15 2.2 Flux Pump ................................................................................................................................................................ 15 2.2.1 The full wave rectifier-flux pump ..................................................................................................................... 15 2.2.2 A Different Perspective Using Circuit Analysis ............................................................................................... 18 2.2.3 The Rise and Fall of Power ............................................................................................................................... 19 2.2.4 The Difference Between Inductive and Resistive Operation ............................................................................ 20 3 Experimental Set-up ........................................................................................................................................................ 21 3.1 General Description .................................................................................................................................................. 21 3.1.1 Disclaimer ......................................................................................................................................................... 21 3.2 Inside the Cryostat Chamber .................................................................................................................................... 22 3.2.1 Flux Pump Circuit V3.0 .................................................................................................................................... 22 3.2.2 Flux Pump Circuit V4.0 .................................................................................................................................... 24 3.2.3 The Cryostat ...................................................................................................................................................... 25 3.2.4 The Cryostat Wiring.......................................................................................................................................... 26 3.2 Outside the Cryostat ................................................................................................................................................. 27 3.3 Digital Interface - LabVIEW ................................................................................................................................... 29 4 3.3.1 Generating the Primary Signal .......................................................................................................................... 30 3.3.2 Controlling the Heaters ..................................................................................................................................... 30 3.3.3 Inductive Communication Wave ....................................................................................................................... 31 4 Results and Discussion .................................................................................................................................................... 32 4.1 Testing V3.0 of the Flux Pump ................................................................................................................................ 32 4.1.1 Pumping V3.0 ................................................................................................................................................. 32 4.1.2 Persistent Current Test ...................................................................................................................................... 33 4.2 Calibration ................................................................................................................................................................ 34 4.2.1 The Sensors Dependency on Temperature ........................................................................................................ 36 4.3 Testing the for the Optimal Wave ............................................................................................................................ 38 4.3.1 Finding the Optimal Frequency ........................................................................................................................ 38 4.3.2 Finding the Optimal 퐼푃 ..................................................................................................................................... 39 4.4 Characterizing the Flux Pump System ..................................................................................................................... 41 4.4.1 Fitting a Theoretical Model ............................................................................................................................... 43 4.4.2 Fitting the Experimental
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