Theoretical Analysis and Design Consideration of Advanced Linear Type Magnetic Flux Pump
As a current compensator, we already developed a linear type magnetic flux pump (LTMFP) that is comprised of DC coils, three phase armature coils, an LTS Nb foil and laminated linear slots. The LTMFP produced a homopolar traveling magnetic field with DC bias current and 3-phase armature current and then, a pumping current is generated in the closed superconducting loop. In this study, we have proposed an advanced LTMFP which can easily produce homopolar traveling magnetic field with the combination of a permanent magnet and the AC armature current. Since the permanent magnets have replaced DC coils in the system, its structure and operation are simplified. As well as, the heating loss of the advanced LTMFP is reduced due to the permanent magnet compared with the LTMFP. From this reason, we confirmed that the advanced LTMFP has more simplified and efficient operation compared with already developed magnetic flux pumps. This paper describes the structure and operating principle of the advanced LTMFP. As well as, the distributions of electromagnetic-thermal analysis of the LTS Nb foil were calculated based on the finite element method (FEM). Thus, in order to realize the homopolar traveling magnetic field, appropriately designing parameters of the combination of AC current and the permanent magnet were obtained.
A flux pumping method applied to the magnetization of YBCO superconducting coils: frequency, amplitude and waveform characteristics
This letter presents a flux pumping method and the results gained when it was used to magnetize a range of different YBCO coils. The pumping device consists of an iron magnetic circuit with eight copper coils which apply a traveling magnetic field to the superconductor. The copper poles are arranged vertically with an air gap length of 1 mm and the iron cores are made of laminated electric steel plates to minimize eddy-current losses. We have used this arrangement to investigate the best possible pumping result when parameters such as frequency, amplitude and waveform are varied. We have successfully pumped current into the superconducting coil up to a value of 90% of Ic and achieved a resultant magnetic field of 1.5 T.
Reid on Hypotheses and the Ether; A Reassessment
In recent years historians of science have come to see that Thomas Reid’s Essays on the Intellectual Powers of Man had a profound impact on the development of British methodological thought in the late-eighteenth and early-nineteenth centuries. Larry Laudan has argued that Reid was “the first major British philosopher to take Newton’s opinions on induction, causality, and hypotheses seriously”; and that Reid was thereby instrumental in changing the character of British methodological discourse in the Enlightenment.(1) Geoffrey Cantor has examined in detail the influence of Reid’s critique of ether theories and hypotheses in the Essays on leading protagonists in the nineteenth-century debates surrounding the wave theory of light,(2) and Richard Olson has traced the origins of the scientific style of British physics in the Victorian period to the writings of Reid and other Common Sense philosophers. (3) As well as delineating Reid’s influence, Laudan, Cantor, and Olson have attempted to identify the problems to which he addressed himself in articulating his methodology, and they have analysed with some care the internal structure of his methodological views. Thanks to the work of these historians, therefore, we have a fairly comprehensive picture of Reid’s methodology and its fortunes in the nineteenth century.