{'fraction_non_alphanumeric': 0.04897959183673469, 'fraction_numerical': 0.055782312925170066, 'mean_word_length': 4.111111111111111, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Field dependence of the critical current density of MgB2/Cu wire for coil development

The critical current density (Jc) of monofilament Cu/MgB2 wire was measured between 4.2 and 30 K with a variable temperature insert (VTI) in a 20 T superconducting magnet using the DC pulse four-wire method with a 1 µV cm−1 criterion. The critical current density, Jc, was measured to be 0.83 × 104 A cm−2 at 3 T at 21 K and 0.66 × 104 A cm−2 at 8 T at 4.2 K for the MgB2 sample, which was annealed at 700 °C for 30 min with 5.8 °C min−1 heating rate under 4% H2–Ar gas flow. Scanning electron microscopy (SEM), electron dispersive spectroscopy (EDS) and x-ray diffraction (XRD) analysis were used to characterize the microstructure of the samples.