Extraction of Critical Current Density and Flux Creep Exponent in the Magnetic Superconductor Ru-1212 Using the ac Magnetic Susceptibility Measurements

The frequency-dependent critical current of a superconductor strip and Roebel cable has been studied using a 2D finite element simulation. It is shown that the critical current of the superconductor increases with frequency as f 1/n , where n is the exponent of the power law flux creep model. Transport ac loss in a superconductor strip decreases with frequency as f −2/n when the amplitude of the applied ac current is far less than its critical current. However, when the applied current is large and becomes comparable to the critical current, the transport ac loss decreases with frequency as 1/ f . The analytical results are substantiated with available experimental data and the results of a 2D finite element simulation.

Section: Current-voltage Behaviourmentioning

confidence: 99%

Frequency-dependent critical current and transport ac loss of superconductor strip and Roebel cable

Thakur¹,

Raj²,

Brandt³

et al. 2011

“…The variation of magnetic ac loss of superconductors is closely associated with its critical current, which is a function of the magnetic field [24], temperature [25][26][27][28][29] and frequency [5,14,30,31] of the applied ac magnetic field. The combined effect of these variables can be represented in the form called the 'separation of variables'…”

Section: Critical Currentmentioning

confidence: 99%

Frequency dependent magnetization of superconductor strip

Thakur¹,

Raj²,

Brandt³

et al. 2011

The frequency dependence of magnetic ac loss of thin superconductor strip subjected to an ac magnetic field perpendicular to the surface of the strip is investigated by incorporating a flux creep model into the critical state model of Brandt and Indenbom. It is found that the reduced ac loss exhibits a maximum value at a frequency f m , which is a rapidly varying function of the applied ac magnetic field. At low magnetic field, f m becomes zero, and ac loss decreases with frequency as a power law (∼ f −2/n ). Whereas at high magnetic field f m becomes infinite and ac loss increases with frequency, still following the power law (∼ f 1/n ). The analytical results are substantiated with experimental data and the results of a 2D finite element simulation.

“…As reported in [35][36][37][38][39], the critical current J c of the superconducting film is dependent on the frequency of the AC field, when the film is subjected to an AC applied field with/without a small DC transport current. In addition, such a frequency dependence of the critical current is given by several empirical relationships.…”

Section: Data Availability Statementmentioning

confidence: 68%

“…More specifically, the number of flux avalanches in the superconducting films at the same magnetic field increases first and then decreases with increasing frequency. In fact, the actual critical current J c is dependent on the frequency of the AC field, when the film is subjected to an AC applied field with/without a small DC transport current [35][36][37][38][39]. However, the rapidly rising DC magnetic field may play a major role in the applied field relative to the AC field in this work, because the amplitude of the AC magnetic field is quite small.…”

Section: Resultsmentioning

confidence: 85%

“…Besides the above DC cases, where the applied field increases linearly with a constant ramp rate, the electromagnetic responses (e.g. critical current, AC loss, and thermomagnetic instability) of superconductors exposed to the AC field have been widely investigated [35][36][37][38][39][40][41][42][43][44][45]. Motta et al experimentally observed the flux avalanches triggered by an AC field in a superconducting Nb film and revealed that the flux avalanches triggered at the increasing branch of the applied field can guide antiflux entry in the decreasing applied field [43,44].…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Sensitivity of the thermomagnetic instability in superconducting film to magnetic perturbation for electromagnetic interference detection

Jiang¹,

Xue²,

Zhou³

2022

The time-varying magnetic field with electromagnetic perturbation is regarded as an important parameter to the thermomagnetic stability of superconducting film devices. In this work, using the thermomagnetic model, we investigate the sensitivity of thermomagnetic instability in the superconducting film exposed to a linear ramp magnetic field, superposed by additional AC magnetic perturbation with tunable amplitude and oscillation frequency. Surprisingly, we find that the thermomagnetic instability is a non-monotonic function with the increasing oscillation frequency of magnetic perturbation, depending on the working temperature and oscillation amplitude. The unexpected non-monotonic sensitivity of thermomagnetic instability is revealed by the characteristic oscillation of electric field which can not be aggravated by the AC magnetic perturbation with very high frequency. The findings of this paper demonstrate that the magnetic perturbation of very low or high frequency is not the main factor that triggers the thermomagnetic instability of superconducting films. Furthermore, using the magnetic moment measurement, we propose a possible electromagnetic interference detection by the superconducting film based on such non-monotonic sensitivity of the thermomagnetic instability, which can be used to detect the tunable target electromagnetic interference with characteristic frequency in a complex electromagnetic environment.