Measurement of the magnetic field inside the holes of a drilled bulk high-T_csuperconductor

Abstract

Abstract.We use macroscopic holes drilled in a bulk YBCO superconductor to probe its magnetic properties in the volume of the sample. The sample is subjected to an AC magnetic flux with a density ranging from 30 mT to 130 mT and the flux in the superconductor is probed by miniature coils inserted in the holes. In a given hole, three different penetration regimes can be observed: (i) the shielded regime, where no magnetic flux threads the hole; (ii) the gradual penetration regime, where the waveform of the magnetic field has a clipped sine shape whose fundamental component scales with the applied field; and (iii) the flux concentration regime, where the waveform of the magnetic field is nearly a sine wave, with an amplitude exceeding that of the applied field by up to a factor of two. The distribution of the penetration regimes in the holes is compared with that of the magnetic flux density at the top and bottom surfaces of the sample, and is interpreted with the help of optical polarized light micrographs of these surfaces. We show that the measurement of the magnetic field inside the holes Measurement of the magnetic field inside the holes of a drilled bulk HTS 2 can be used as a local characterization of the bulk magnetic properties of the sample.

Pulsed-field magnetization of drilled bulk high-temperature superconductors: flux front propagation in the volume and on the surface

“…The magnetic flux was probed in a quarter of the sample, containing a total of 16 holes (these holes are represented in Flux front propagation in a drilled HTS during a pulsed-field magnetization grey on Figure 3). Note that earlier measurements with an AC magnetic field excitation (with a coil-probing method similar to that reported in our previous work [18]) showed that this particular quarter of the sample is representative of the full sample. Each holder contained two microcoils consisting each of 10 turns of 50 µm of isolated copper wire, yielding a coil height of 1 mm.…”

An investigation of electromagnetic anti-collision real-time measurement for drilling cluster wells

“…The two electromagnets are situated symmetrically around the center of magnetometer, and the distance between them is l. The axes of the two electromagnets are parallel, while the current in the coils run in opposite directions, creating magnetic moments in the two magnetic sources equal in magnitude and opposite in direction. Therefore, the total magnetic field's intensity as detected by triaxial magnetometer is 0 when there is no other outer magnetic field, ensuring that the electromagnetic collision avoidance system provides a relatively strong magnetizing field without affecting the measurement by triaxial magnetometer (Diao et al, 2011;Liu and Wang, 2011;Finlay et al, 2010;Macmillan et al, 2009;Lousberg et al, 2009). Assuming that the radius and turn of the coil are R and n 1 , respectively, and the magnetic moment of the coil is amplified by the iron core up to n 2 times the original value.…”

“…When no casing exists around the triaxial magnetometer, or the casing is too far away, the Earth field and the field of the casing induced by electromagnets are both too weak, resulting in a magnetic difference value that is not sufficient to determine whether casing exists (Macmillan et al, 2009;Lousberg et al, 2009;Yang et al, 2010). Assuming that the existence of casing can be determined when peakepeak value is larger than 1 nT, then the effective detection range of this collision avoidance method is approximately 8 m (see the peakepeak value where borehole distance is 8 m in Fig.…”

A Hybrid Magnet with a Logarithmic in Time Field Deviation

“…If the pulse duration τ i is shorter than τ, then the dynamics of vortex and field trap are significantly depend on effect of field penetration delay and local heating. Perhaps this explains the unusual distribution of the fields in the drilled tablet [11]. In our work characteristics of a hybrid magnet under a short pulse magnetization is examined.…”