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FIZIKA A 10 (2001) 4 , 155-168
 
CRITICAL CURRENTS AND VORTEX PINNING IN 235U DOPED Ag/Bi2223
TAPES IRRADIATED WITH THERMAL NEUTRONS
EMIL BABIĘa, IVICA KUEVIĘa, DAMIEN
MARINAROb and SHI XUE DOUb
aDepartment of Physics, Faculty of Science, University of
Zagreb, 10000 Zagreb, Croatia
bCentre for Superconducting and Electronic Materials,
University of Wollongong, Wollongong, NSW 2522, Australia
Dedicated to Professor Kseno Ilakovac on the occasion of his 70th
birthday
Received 4 April 2001; revised manuscript received 20 September 2001
Accepted 24 September 2001 Online 6 April 2002
Systematic analysis of the transport critical current densities Jc at 77 K
for 235U-oxide (UO2·2H2O) doped Ag-sheathed
(Bi,Pb)2Sr2Ca2Cu3Ox tapes (Bi2223)
irradiated with thermal neutrons is presented. Within the explored range of U-oxide
concentrations (c £ 2 wt%) and neutron fluences (f £ 6·1019 n/m2),
the pinning of vortices in irradiated tapes increases approximately linearly with fission
track density (proportional to cf), as evidenced by
progressively weaker magnetic field dependence of Jc on increasing cf. Accordingly, the crossover field B*
at which the pinning force density Fp reaches its maximum value Fpmax
= JcB* and the irreversibility field Birr(Fp® 0) increase approximately linearly with cf.
Therefore, Jc-B and Fp-B
variations for all tapes with vortex pinning dominated by fission tracks show universal
scaling behaviour with the scaling parameter B*
(proportional to cf). Taking into account the adverse effects
of c and f on Jc of our tapes, we estimate a maximum
B* and Birr that can be reached in 235U-oxide
doped Bi2223 tapes at 77 K.
PACS numbers: 74.60.Ge,74.60.Jg,74.62.Dh,74.72.Hs
UDC 538.945 <\p>
Keywords: Ag-sheathed Bi2223, 235U-oxide doping, U-oxide concentrations £ 2 wt%, thermal neutron irradiation, fluences (f
£ 6·1019 n/m2), critical current
densities at 77 K, pinning of vortices, crossover field, irreversibility field, universal
scaling behaviour
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