Neutron irradiation of Nb<inf>3</inf>Sn and NbTi multifilamentary composites
Облучение нейтронами многофиламентных композитов Nb3Sn и NbTi
1975-03-01
SCID: 54.1/hpwa8tfe
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Nb3Sn multifilamentary compositesNbTi multifilamentary compositescritical current (Ic) degradationcritical temperature (Tc) reductionneutron irradiation
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Abstract (AI)
NbTi and Nb <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> Sn multifilamentary composites have been irradiated with fast-neutrons at 60 ± 5°C to fluences of 1.2×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">20</sup> n/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> (E > 1 MeV). The NbTi samples show only a moderate reduction of I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</inf> as a function of neutron fluence in an applied field of 40 kG. Reductions in I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</inf> were observed for fluences greater than 3 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">17</sup> n/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and saturate at 18% for fluences greater than 3-4 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">19</sup> n/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The Nb <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> Sn composites showed large neutron radiation induced changes in T <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</inf> , I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</inf> and H <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c2</inf> . Reductions in T <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</inf> were observed for fluences greater than 7 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">17</sup> n/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . No measurable changes in I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</inf> (40 kG) were observed below 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">18</sup> n/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . Between 2 and 3×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">18</sup> n/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , however, there is an apparent threshold where a very rapid reduction in I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</inf> (40 kG) is initiated. At the threshold the decrease in T <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</inf> is 13%. Between the threshold and 1.1 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">19</sup> n/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> (40 kG) has been reduced to 4% of the unirradiated value. These changes in superconducting properties in NbTi and Nb <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> Sn are analyzed in terms of the radiation induced defects. The impact of the response to irradiation of both materials on their applications in fusion reactor magnets is discussed.
Key Findings
1
Between that threshold and 1.1×10^19 n/cm^2 Nb3Sn Ic (40 kG) is reduced to 4% of the unirradiated value.
2
Between ~2–3×10^18 n/cm^2 a threshold in Nb3Sn produces a rapid Ic (40 kG) reduction; at threshold Tc decreases by 13%.
3
For NbTi, Ic reductions begin for fluences >3×10^17 n/cm^2 and saturate at an 18% decrease for fluences >3–4×10^19 n/cm^2.
4
Nb3Sn composites exhibit large radiation-induced reductions in Tc, Ic, and Hc2 after neutron irradiation.
5
Nb3Sn shows Tc reductions for fluences >7×10^17 n/cm^2, with no measurable Ic (40 kG) changes below 1×10^18 n/cm^2.
6
NbTi multifilamentary composites irradiated to 1.2×10^20 n/cm^2 (E>1 MeV) show only a moderate reduction of Ic in 40 kG applied field.
7
The observed changes in superconducting properties for both materials are analyzed and attributed to radiation-induced defects, with implications for fusion reactor magnet applications.
Research Object
NbTi and Nb3Sn multifilamentary composite superconductors irradiated with fast neutrons
Research Subject
Radiation-induced changes in superconducting properties (Tc, Ic, Hc2) and their fluence-dependent degradation/threshold behavior linked to radiation-induced defects
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1975-03-01
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