Publications of Michel Houbart
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See detailTrapped magnetic field distribution above two magnetized bulk superconductors close to each other
Houbart, Michel ULiege; Fagnard, Jean-François ULiege; Dennis, Anthony et al

in Superconductor Science and Technology (2020), 33

Bulk large-grain superconductors can be used as high-field permanent magnets. Although the properties of such individual trapped field magnets are well documented, much less is known concerning their ... [more ▼]

Bulk large-grain superconductors can be used as high-field permanent magnets. Although the properties of such individual trapped field magnets are well documented, much less is known concerning their behaviour when two are brought together. In this work, the interaction between two cylindrical bulk YBa2Cu3O7 (YBCO) superconductors is described. Two sets of experiments were carried out. The first involved the simultaneous magnetization of two bulk superconductors placed a short distance apart. Here, the applied magnetic field was aligned parallel to the c-axis of one bulk, while the other was oriented with its c-axis offset . For a centre-to-centre distance equal to twice the sample height, the presence of the second sample is found not to alter the current distribution inside the first. Consequently, the contribution of both samples simply sums, thus increasing the magnetic flux density between them. In the second set of experiments, the translational approach of the superconductors with parallel c-axes was investigated. The following configurations were considered: (i) face to face approach (with anti-parallel trapped field orientation) and (ii) sideways approach (with parallel trapped field orientation). An irreversible decrease of the trapped field was measured on separation . Repeated approach cycles showed that the irreversible loss of trapped field is largest for the first approach. [less ▲]

Detailed reference viewed: 34 (10 ULiège)
See detailTrapped field of two close bulk superconductors with misaligned c-axes
Houbart, Michel ULiege; Fagnard, Jean-François ULiege; Dennis, Anthony et al

Poster (2019, September 03)

The simultaneous magnetisation of two cylindrical bulk YBCO superconductors (diameter 15.7 mm, height 8.8 mm) closely spaced is investigated experimentally. The applied magnetic field is parallel to the c ... [more ▼]

The simultaneous magnetisation of two cylindrical bulk YBCO superconductors (diameter 15.7 mm, height 8.8 mm) closely spaced is investigated experimentally. The applied magnetic field is parallel to the c-axis of one of them, while the other has its c-axis directed at different angles with the first. Results are compared to the trapped field above an isolated sample. Experiments are carried out at 65 K and 77 K both in field cooled under 2.5 T and in zero field cooled under 7 T. Experimental trapped field data are compared to analytical calculations assuming fully magnetized superconductors. For a centre-to-centre distance equal to twice the sample height, the presence of the second sample is found not to alter the current distribution inside the first. Consequently, the contribution of both samples adds up, thus increasing the magnetic flux density between them. [less ▲]

Detailed reference viewed: 26 (3 ULiège)
See detailTrapped field evolution of two approaching bulk superconductors with parallel c-axes
Houbart, Michel ULiege; Fagnard, Jean-François ULiege; Namburi, Devendra Kumar et al

Poster (2019, August 29)

Although the properties of individual trapped field magnets are well documented, there is little scientific information concerning their trapped field behaviour when several of them are brought in close ... [more ▼]

Although the properties of individual trapped field magnets are well documented, there is little scientific information concerning their trapped field behaviour when several of them are brought in close vicinity. In this context, the translational approach of two cylindrical bulk YBCO superconductors (diameter 15.7 mm, height 8.8 mm) with parallel c-axes is experimentally investigated. The evolution of the trapped field at the surface of a fixed superconducting sample is measured while a second sample is approached. The following configurations are considered: (i) face to face (with anti-parallel trapped field orientation) approach and (ii) sideways (with parallel trapped field orientation) approach. The studied distance between the samples ranges from 120 mm, where the samples are observed to have no influence on each other, to contact (0 mm). The experiments are carried out at 77K and the samples are magnetised independently in field cooled under 1.2 T. The motion actuation is performed using a computer-controlled miniature linear actuator which is capable of overcoming the repulsive force arising between the trapped field magnets. Experimental trapped field data are compared to analytical calculations assuming fully magnetized superconductors. The trapped field of the fixed superconducting sample is measured to be altered by the second one when the separating distance is smaller than their diameters. If the distance is smaller than this limit, an irreversible diminution of the trapped field is measured when the samples are separated again. Repeated approach cycles showed that the irreversible loss of trapped field is more important for the first approach. [less ▲]

Detailed reference viewed: 26 (5 ULiège)