Kritične struje i zapinjanje magnetskih vrtloga u Ag/Bi2223 vrpcama dopiranim s 235U i ozračenim termičkim neutronima

Systematic analysis of the transport critical current densities Jc at 77 K for 235Uoxide (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 (φ ≤ 6 · 1019 n/m2), the pinning of vortices in irradiated tapes increases approximately linearly with fission track density (proportional to cφ), as evidenced by progressively weaker magnetic field dependence of Jc on increasing cφ. Accordingly, the crossover field B∗ at which the pinning force density Fp reaches its maximum value Fp max = JcB∗ and the irreversibility field Birr(Fp → 0) increase approximately linearly with cφ. 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 cφ). Taking into account the adverse effects of c and φ 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.Predstavljamo sustavnu analizu transportnih gustoća kritične struje Jc na 77 K sa 235U-oksidom (UO2 · 2H2O) dopiranih, srebrom obloženih (Bi,Pb)2Sr2Ca2Cu3Ox vrpci ozračenih termičkim neutronima. U istraživanom području koncentracija U-oksida (c ≤ 2 tež.%) i toka neutrona (φ ≤ 6 · 1019 n/m2), zapinjanje magnetskih vrtloga u vrpcama raste približno linearno s gustoćom fisijskih tragova (razmjernoj sa cφ), što se ogleda u sve slabijoj ovisnosti Jc o magnetskom polju pri porastu cφ. U skladu s time, prijelazno polje B∗ na kojem gustoća sile zapinjanja Fp postiže najveću vrijednost Fp max = JcB∗ i ireverzibilno polje Birr(Fp → 0) rastu približno linearno s cφ. Zbog toga, Jc − B i Fp − B ovisnosti za sve vrpce u kojima je zapinjanje vrtloga pretežito zbog fisijskih tragova pokazuju univerzalno skaliranje s parametrom skaliranja B∗ (razmjerno cφ). Uzimajući u obzir negativni utjecaj c i φ na Jc naših vrpci, procijenili smo najveća polja B∗ i Birr koja se mogu postići u srebrom obloženim (Bi,Pb)2Sr2Ca2Cu3Ox vrpcama dopiranim s 235U-oksidom na 77 K

Critical currents and vortex pinning in 235U doped Ag/Bi2223 tapes

Systematic analysis of the transport critical current densities J_c at 77 K for ^235U-oxide (UO_2·2H_2O) doped Ag-sheathed (Bi,Pb)_2Sr_2Ca_2Cu_3O_x tapes (Bi2223) irradiated with thermal neutrons is presented. Within the explored range of U-oxide concentrations (c £ 2 wt%) and neutron fluences (ϕ £ 6·10_19 n/m^2), the pinning of vortices in irradiated tapes increases approximately linearly with fission track density (proportional to cϕ), as evidenced by progressively weaker magnetic field dependence of Jc on increasing cf. Accordingly, the crossover field B* at which the pinning force density F_p reaches its maximum value F_pmax = J_cB* and the irreversibility field B_irr(F_p → 0) increase approximately linearly with cϕ. Therefore, J_c-B and F_p-B variations for all tapes with vortex pinning dominated by fission tracks show universal scaling behaviour with the scaling parameter B* (proportional to cϕ). Taking into account the adverse effects of c and f on Jc of our tapes, we estimate a maximum B* and B_irr that can be reached in ^235U-oxide doped Bi2223 tapes at 77 K

Kritične struje i zapinjanje magnetskih vrtloga u Ag/Bi2223 vrpcama dopiranim s 235U i ozračenim termičkim neutronima

Systematic analysis of the transport critical current densities Jc at 77 K for 235Uoxide (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 (φ ≤ 6 · 1019 n/m2), the pinning of vortices in irradiated tapes increases approximately linearly with fission track density (proportional to cφ), as evidenced by progressively weaker magnetic field dependence of Jc on increasing cφ. Accordingly, the crossover field B∗ at which the pinning force density Fp reaches its maximum value Fp max = JcB∗ and the irreversibility field Birr(Fp → 0) increase approximately linearly with cφ. 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 cφ). Taking into account the adverse effects of c and φ 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.Predstavljamo sustavnu analizu transportnih gustoća kritične struje Jc na 77 K sa 235U-oksidom (UO2 · 2H2O) dopiranih, srebrom obloženih (Bi,Pb)2Sr2Ca2Cu3Ox vrpci ozračenih termičkim neutronima. U istraživanom području koncentracija U-oksida (c ≤ 2 tež.%) i toka neutrona (φ ≤ 6 · 1019 n/m2), zapinjanje magnetskih vrtloga u vrpcama raste približno linearno s gustoćom fisijskih tragova (razmjernoj sa cφ), što se ogleda u sve slabijoj ovisnosti Jc o magnetskom polju pri porastu cφ. U skladu s time, prijelazno polje B∗ na kojem gustoća sile zapinjanja Fp postiže najveću vrijednost Fp max = JcB∗ i ireverzibilno polje Birr(Fp → 0) rastu približno linearno s cφ. Zbog toga, Jc − B i Fp − B ovisnosti za sve vrpce u kojima je zapinjanje vrtloga pretežito zbog fisijskih tragova pokazuju univerzalno skaliranje s parametrom skaliranja B∗ (razmjerno cφ). Uzimajući u obzir negativni utjecaj c i φ na Jc naših vrpci, procijenili smo najveća polja B∗ i Birr koja se mogu postići u srebrom obloženim (Bi,Pb)2Sr2Ca2Cu3Ox vrpcama dopiranim s 235U-oksidom na 77 K

Critical currents and vortex pinning in 235U doped Ag/Bi2223 tapes

Systematic analysis of the transport critical current densities J_c at 77 K for ^235U-oxide (UO_2·2H_2O) doped Ag-sheathed (Bi,Pb)_2Sr_2Ca_2Cu_3O_x tapes (Bi2223) irradiated with thermal neutrons is presented. Within the explored range of U-oxide concentrations (c £ 2 wt%) and neutron fluences (ϕ £ 6·10_19 n/m^2), the pinning of vortices in irradiated tapes increases approximately linearly with fission track density (proportional to cϕ), as evidenced by progressively weaker magnetic field dependence of Jc on increasing cf. Accordingly, the crossover field B* at which the pinning force density F_p reaches its maximum value F_pmax = J_cB* and the irreversibility field B_irr(F_p → 0) increase approximately linearly with cϕ. Therefore, J_c-B and F_p-B variations for all tapes with vortex pinning dominated by fission tracks show universal scaling behaviour with the scaling parameter B* (proportional to cϕ). Taking into account the adverse effects of c and f on Jc of our tapes, we estimate a maximum B* and B_irr that can be reached in ^235U-oxide doped Bi2223 tapes at 77 K