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Journal Articles

Optimization of heat treatment of Japanese Nb$$_3$$Sn conductors for toroidal field coils in ITER

Nabara, Yoshihiro; Hemmi, Tsutomu; Kajitani, Hideki; Ozeki, Hidemasa; Suwa, Tomone; Iguchi, Masahide; Nunoya, Yoshihiko; Isono, Takaaki; Matsui, Kunihiro; Koizumi, Norikiyo; et al.

IEEE Transactions on Applied Superconductivity, 24(3), p.6000605_1 - 6000605_5, 2014/06

 Times Cited Count:7 Percentile:39.64(Engineering, Electrical & Electronic)

no abstracts in English

Journal Articles

Examination of Nb$$_{3}$$Sn conductors for ITER central solenoids

Nabara, Yoshihiro; Hemmi, Tsutomu; Kajitani, Hideki; Ozeki, Hidemasa; Iguchi, Masahide; Nunoya, Yoshihiko; Isono, Takaaki; Takahashi, Yoshikazu; Matsui, Kunihiro; Koizumi, Norikiyo; et al.

IEEE Transactions on Applied Superconductivity, 23(3), p.4801604_1 - 4801604_4, 2013/06

 Times Cited Count:10 Percentile:48.09(Engineering, Electrical & Electronic)

no abstracts in English

Journal Articles

Test results of ITER conductors in the SULTAN facility

Bruzzone, P.*; Stepanov, B.*; Wesche, R.*; Mitchell, N.*; Devred, A.*; Nunoya, Yoshihiko; Tronza, V.*; Kim, K.*; Boutboul, T.*; Martovetsky, N.*; et al.

Proceedings of 24th IAEA Fusion Energy Conference (FEC 2012) (CD-ROM), 8 Pages, 2013/03

Starting March 2007, over 60 ITER cable-in-conduit conductors (CICC) have been tested in the SULTAN test facility, Switzerland. For the NbTi CICC, the results confirm the prediction from the strand data, which are made taking the peak field over the conductor cross section as operating field. All the NbTi samples passed the supplier qualification phase. For the Nb$$_{3}$$Sn CICC, the performance prediction is not straightforward because of the irreversible degradation caused by filament damage occurring during cyclic loading. At the first run of the test campaign, the performance of all the Nb$$_{3}$$Sn samples largely meets the target for all the tested samples. Contrary to the NbTi CICC case, the n-index of the transition is substantially lower than in the strands, providing evidence of irreversible degradation. The performance loss upon load cycles and thermal cycles has a broad range among the various conductor samples.

Journal Articles

Test results and investigation of Tcs degradation in Japanese ITER CS conductor samples

Hemmi, Tsutomu; Nunoya, Yoshihiko; Nabara, Yoshihiro; Yoshikawa, Masatoshi*; Matsui, Kunihiro; Kajitani, Hideki; Hamada, Kazuya; Isono, Takaaki; Takahashi, Yoshikazu; Koizumi, Norikiyo; et al.

IEEE Transactions on Applied Superconductivity, 22(3), p.4803305_1 - 4803305_5, 2012/06

 Times Cited Count:44 Percentile:85.91(Engineering, Electrical & Electronic)

To characterize the performance of the CS conductor, a CS conductor sample was tested in the SULTAN facility at CRPP. As a result of the cyclic test up to 1000 cycles, measured Tcs was in good agreement with the expected Tcs, which is calculated by the characteristics of the Nb$$_{3}$$Sn strands and the designed strain. However, continuous degradation of Tcs was observed after 1000 cycles. The degradation of Tcs was around 0.6 K from 1000 cycles to 6000 cycles. On the other hand, the degradation of Tcs by cyclic operation is nearly 0.1 K from 1000 cycles to 10,000 cycles in the CS Insert test at JAEA in 2000. To investigate the causes for the degradation of Tcs, the following items are performed; (1) strain measurement by neutron diffraction, (2) strain measurement by sample cuttings, (3) strand position observation, (4) visual inspection on strands, (5) filament breakage observation, (6) modeling and calculation of the degradation. Detailed results will be presented and discussed.

Journal Articles

Examination of Japanese mass-produced Nb$$_3$$Sn conductors for ITER toroidal field coils

Nabara, Yoshihiro; Nunoya, Yoshihiko; Isono, Takaaki; Hamada, Kazuya; Takahashi, Yoshikazu; Matsui, Kunihiro; Hemmi, Tsutomu; Kawano, Katsumi; Koizumi, Norikiyo; Ebisawa, Noboru; et al.

IEEE Transactions on Applied Superconductivity, 22(3), p.4804804_1 - 4804804_4, 2012/06

 Times Cited Count:17 Percentile:65.56(Engineering, Electrical & Electronic)

no abstracts in English

Journal Articles

Event structure and double helicity asymmetry in jet production from polarized $$p + p$$ collisions at $$sqrt{s}$$ = 200 GeV

Adare, A.*; Afanasiev, S.*; Aidala, C.*; Ajitanand, N. N.*; Akiba, Y.*; Al-Bataineh, H.*; Alexander, J.*; Aoki, K.*; Aphecetche, L.*; Armendariz, R.*; et al.

Physical Review D, 84(1), p.012006_1 - 012006_18, 2011/07

 Times Cited Count:28 Percentile:72.42(Astronomy & Astrophysics)

We report on the event structure and double helicity asymmetry ($$A_{LL}$$) of jet production in longitudinally polarized $$p + p$$ collisions at $$sqrt{s}$$ = 200 GeV. Photons and charged particles were measured by the PHENIX experiment. Event structure was compared with the results from PYTHIA event generator. The production rate of reconstructed jets is satisfactorily reproduced with the next-to-leading-order perturbative QCD calculation. We measured $$A_{LL}$$ = -0.0014 $$pm$$ 0.0037 at the lowest $$P_T$$ bin and -0.0181 $$pm$$ 0.0282 at the highest $$P_T$$ bin. The measured $$A_{LL}$$ is compared with the predictions that assume various $$Delta G(x)$$ distributions.

Journal Articles

Identified charged hadron production in $$p + p$$ collisions at $$sqrt{s}$$ = 200 and 62.4 GeV

Adare, A.*; Afanasiev, S.*; Aidala, C.*; Ajitanand, N. N.*; Akiba, Yasuyuki*; Al-Bataineh, H.*; Alexander, J.*; Aoki, Kazuya*; Aphecetche, L.*; Armendariz, R.*; et al.

Physical Review C, 83(6), p.064903_1 - 064903_29, 2011/06

 Times Cited Count:176 Percentile:99.41(Physics, Nuclear)

Transverse momentum distributions and yields for $$pi^{pm}, K^{pm}, p$$, and $$bar{p}$$ in $$p + p$$ collisions at $$sqrt{s}$$ = 200 and 62.4 GeV at midrapidity are measured by the PHENIX experiment at the RHIC. We present the inverse slope parameter, mean transverse momentum, and yield per unit rapidity at each energy, and compare them to other measurements at different $$sqrt{s}$$ collisions. We also present the scaling properties such as $$m_T$$ and $$x_T$$ scaling and discuss the mechanism of the particle production in $$p + p$$ collisions. The measured spectra are compared to next-to-leading order perturbative QCD calculations.

Journal Articles

Azimuthal correlations of electrons from heavy-flavor decay with hadrons in $$p+p$$ and Au+Au collisions at $$sqrt{s_{NN}}$$ = 200 GeV

Adare, A.*; Afanasiev, S.*; Aidala, C.*; Ajitanand, N. N.*; Akiba, Yasuyuki*; Al-Bataineh, H.*; Alexander, J.*; Aoki, Kazuya*; Aphecetche, L.*; Aramaki, Y.*; et al.

Physical Review C, 83(4), p.044912_1 - 044912_16, 2011/04

 Times Cited Count:7 Percentile:49.81(Physics, Nuclear)

Measurements of electrons from the decay of open-heavy-flavor mesons have shown that the yields are suppressed in Au+Au collisions compared to expectations from binary-scaled $$p+p$$ collisions. Here we extend these studies to two particle correlations where one particle is an electron from the decay of a heavy flavor meson and the other is a charged hadron from either the decay of the heavy meson or from jet fragmentation. These measurements provide more detailed information about the interaction between heavy quarks and the quark-gluon matter. We find the away-side-jet shape and yield to be modified in Au+Au collisions compared to $$p+p$$ collisions.

Journal Articles

Measurement of neutral mesons in $$p$$ + $$p$$ collisions at $$sqrt{s}$$ = 200 GeV and scaling properties of hadron production

Adare, A.*; Afanasiev, S.*; Aidala, C.*; Ajitanand, N. N.*; Akiba, Y.*; Al-Bataineh, H.*; Alexander, J.*; Aoki, K.*; Aphecetche, L.*; Armendariz, R.*; et al.

Physical Review D, 83(5), p.052004_1 - 052004_26, 2011/03

 Times Cited Count:169 Percentile:98.47(Astronomy & Astrophysics)

The PHENIX experiment at RHIC has measured the invariant differential cross section for production of $$K^0_s$$, $$omega$$, $$eta'$$ and $$phi$$ mesons in $$p + p$$ collisions at $$sqrt{s}$$ = 200 GeV. The spectral shapes of all hadron transverse momentum distributions are well described by a Tsallis distribution functional form with only two parameters, $$n$$ and $$T$$, determining the high $$p_T$$ and characterizing the low $$p_T$$ regions for the spectra, respectively. The integrated invariant cross sections calculated from the fitted distributions are found to be consistent with existing measurements and with statistical model predictions.

Journal Articles

Test results of the third Japanese SULTAN sample

Matsui, Kunihiro; Isono, Takaaki; Nunoya, Yoshihiko; Hemmi, Tsutomu; Okui, Yoshio*; Oshikiri, Masayuki; Koizumi, Norikiyo; Takahashi, Yoshikazu; Okuno, Kiyoshi; Stepanov, B.*; et al.

IEEE Transactions on Applied Superconductivity, 19(3), p.1470 - 1473, 2009/06

 Times Cited Count:20 Percentile:67.75(Engineering, Electrical & Electronic)

Conductor procurement for ITER Toroidal Field (TF) coils in Japan has just stated in the spring of 2008 under agreement with ITER organization. Before the activity, each Nb$$_{3}$$Sn conductor must be tested at SULTAN facility in Switzerland for qualification of the conductor. The TF conductor is cable-in-conduit type with about 40 mm outer diameter and is composed of 900 Nb$$_{3}$$Sn strands, 522 Cu strands, a central spiral and a 316LN tube. Required performance of the conductor is Tcs of 5.7 K at 68 kA and 11.3 T, which is operating condition of TF coils. Japan has four Nb$$_{3}$$Sn strand suppliers for ITER and two of them were already tested as Japanese 1st and 2nd SULTAN samples. This paper shows test results of 3rd Japanese SULTAN sample using Nb$$_{3}$$Sn strands fabricated by resting two suppliers.

Journal Articles

Performance of Japanese Nb$$_{3}$$Sn conductors for ITER toroidal field coils

Takahashi, Yoshikazu; Isono, Takaaki; Koizumi, Norikiyo; Nunoya, Yoshihiko; Matsui, Kunihiro; Nabara, Yoshihiro; Hemmi, Tsutomu; Oshikiri, Masayuki; Uno, Yasuhiro*; Okuno, Kiyoshi; et al.

IEEE Transactions on Applied Superconductivity, 18(2), p.471 - 474, 2008/06

 Times Cited Count:16 Percentile:62.82(Engineering, Electrical & Electronic)

The ITER TF coil system consists of 18 D-shape coils. The operating current and the maximum field are 68 kA and 11.8 T, respectively. A Nb$$_{3}$$Sn cable-in-conduit conductor with a central channel is used, with a unit length of about 380 m. A cable consists of 900 Nb$$_{3}$$Sn strands and 522 Cu strands with a diameter of 0.82 mm. Superconducting performance of full-size conductors manufactured was measured at the operating condition of the TF coils with the maximum field. The strands made by bronze and internal-Sn methods were used for the sample conductors with a void fraction of 29% and 33%, respectively. The measured current sharing temperatures Tcs are 6.5-6.7K for the bronze route method and 5.7-5.9K for the internal-Sn method. The Tcs of the conductor with small void fraction is relatively higher with 0.1-0.2K than that with large void fraction. It is confirmed that Tcs of both strands is higher than the design value (5.7K). It is shown from the results that the strain on the conductor, estimated by the strand data, is about -0.7%. This value seems to be reasonable.

Journal Articles

Role of trapped and solvated electrons in Ps formation

Stepanov, S. V.*; Byakov, V. M.*; He, C.*; Hirade, Tetsuya; Mikhin, K. V.*

Acta Physica Polonica A, 107(4), p.642 - 650, 2005/00

Role of trapped and solvated electrons in Ps formation is discussed. Combination of thermalized positron with such electrons is energetically possible and may contribute to Ps formation. Contrary to the positron reaction with a quasi-free electron, this process is not limited to picosecond times, but proceeds on a timescale of nanoseconds. In this case conventional exponential deconvolution of row lifetime positron annihilation spectra becomes questionable. Rigorous treatment of the data needs nonexponential deconvolution, based on an adequate physical input. Such an approach is suggested here. Its reduced form is used for interpretation of the Ps formation data in polyethylene, EMMA and PMMA in dark and in light vs. time of the measurement and temperature. Parameters characterized accumulation of trapped electrons and their recombination with counter ions and positrons are obtained.

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