Threshold for creation of ionization pinning centers in YBCO by heavy ions

Weinstein, R.; Sawh, Ravi‐Persad; Liu, J.; Parks, D.; Ren, Yanru; Obot, V.; Foster, C.C.

doi:10.1016/s0921-4534(01)00360-4

Cited by 16 publications

(12 citation statements)

References 9 publications

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“…Present day TFMs, e.g., 2 cm in diameter and 1 cm long, containing randomly located PCs made up of chemical deposits, will retain fields of typically about 0.3-0.5 T at 77 K, and up to ∼1 T at 65 K. Doping the HTS with uranium followed by neutron irradiation to cause fission produces a 'poor man's' ion beam, and a relatively low-cost TFM which can retain 2.1 T at 77 K [9,10,15], and about 5.0 T at 65 K. Further increases of trapped field can be expected in the future, when the best radiation PCs can be emulated by chemical means. It is not unreasonable to expect future trapped fields of up to 10 T at 77 K.…”

Section: Introductionmentioning

confidence: 99%

“…Considering temperatures below those achievable in liquid nitrogen, trapped field of 10 T was achieved at 42 K in YBa 2 Cu 3 O 7−δ (YBCO) [15].…”

Section: Introductionmentioning

confidence: 99%

“…Even this small loss of field can be avoided. It has been found [15] that a decrease of a few degrees in temperature after activating a TFM decreases creep to (practically) zero.…”

Section: Introductionmentioning

confidence: 99%

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Measurements of flux pumping activation of trapped field magnets

Weinstein

Parks

Sawh

et al. 2010

Supercond. Sci. Technol.

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Large grains of high temperature superconducting (HTS) material can be utilized as trapped field magnets (TFMs). Persistent currents are set up in the HTS when it is cooled in a magnetic field, or exposed to a magnetic field after cooling. TFMs have been improved over the past two decades by the efforts of a large number of worldwide research groups. However, applications using TFMs have lagged, in part due to the problem of high fields needed for activation. We describe herein experiments designed to observe the behaviour of TFM activation using repeated applications of low fields (called 'pumping'). Significant partial activation is obtained using a non-uniform pumping field (e.g., a small permanent magnet) which is higher in the centre of the HTS than at the periphery. Cooling in zero field followed by pumping with such a field results in trapping the full applied field, in comparison to half of the applied field being trapped by cooling in zero field followed by application of a uniform field. We find that for partial activation by cooling in a field and subsequent activation by pumping, the resulting fields are additive. We also conclude that for activation by fluxoid pumping, creep assists the process.

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Section: Introductionmentioning

confidence: 99%

“…Considering temperatures below those achievable in liquid nitrogen, trapped field of 10 T was achieved at 42 K in YBa 2 Cu 3 O 7−δ (YBCO) [15].…”

Section: Introductionmentioning

confidence: 99%

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Measurements of flux pumping activation of trapped field magnets

Weinstein

Parks

Sawh

et al. 2010

Supercond. Sci. Technol.

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“…Much progress has been made in the last few years to improve flux pinning in bulk melt-textured YBCO by chemical doping [1] and by irradiation methods [2,3]. Different kinds of radiation-induced extended defect structures can be produced.…”

Section: Introductionmentioning

confidence: 99%

Strongly enhanced irreversibility fields and Bose-glass behaviour in bulk YBCO with discontinuous columnar irradiation defects

Fuchs¹,

Nenkov²,

Krabbes³

et al. 2007

Supercond. Sci. Technol.

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Flux pinning properties and irreversibility fields Birr(T) of melt-textured YBCO with discontinuous or multiple-in-line-damage (MILD) columnar defects produced by irradiation with high-energy U238 ions were studied at a constant matching field of Bϕ = 10 T and for several energy losses between Se = 1.67 and 2.4 keV Å−1. With increasing Se and increasing length of the MILD pins, the critical current density jc(H,T) strongly increases and Birr(T) for fields along the c axis progressively shifts upwards reaching 9 T at 77 K. For Se = 2.4 keV Å−1, a pronounced kink is observed in Birr(T) at 8 T which is a strong indication of Bose-glass behaviour. The jc(H) dependence of this sample shows a peak at a low applied field Bp. This peak effect is explained by the entanglement of vortices. It is argued that for MILD pins single vortices interact simultaneously with many short columnar defects in neighbouring ion trails resulting in an automatic splay in the vortex orientation. The observed decrease of Bp with increasing temperature is estimated taking the increasing thermal fluctuations into account.

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“…In fact, pinning centers created via electronic collisions yield in HTSs the largest -several factors larger than the sustained by pinning centers formed via nuclear collision [14]. These amorphous defects, which introduce disorder at the length scale of the superconducting coherence length [6]- [11], [15], also effect .…”

Section: Introductionmentioning

confidence: 99%

Universal Dependence of the Critical Temperature in HTS on the Fractional Volume of Nanosize Defects

Gandini

Weinstein

Sawh

et al. 2007

IEEE Trans. Appl. Supercond.

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We report on the effect of randomly-distributed amorphous defects, at the length scale of the superconducting coherence length, on in YBCO. These damages were created by ions irradiation with a wide range of energy and fluence. Typically, in previous experiments, was found to vary with ion fluence, species, energy, and ionization charge, and also on the chemical composition and density of the HTS. Neither a phenomenological nor a theoretical relationship between and these ion properties is however known of. We now show that the decrease in is a universal function of the fractional defect volume embedded in the HTS. We also re-analysed several experiments by others, and find that the same universality applies. This finding provides, for the first time, a means to calculate the effect on of disorder as created by randomly-distributed amorphous nanosize defects.

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Threshold for creation of ionization pinning centers in YBCO by heavy ions

Cited by 16 publications

References 9 publications

Measurements of flux pumping activation of trapped field magnets

Measurements of flux pumping activation of trapped field magnets

Strongly enhanced irreversibility fields and Bose-glass behaviour in bulk YBCO with discontinuous columnar irradiation defects

Universal Dependence of the Critical Temperature in HTS on the Fractional Volume of Nanosize Defects

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