JOPSS - Search Results

In ITER, the conductor for the Central Solenoid (CS) uses Incoloy 908, which requires special environment control to prevent cracks caused by Stress Accelerated Grain Boundary Oxidation (SAGBO) during Nb3Sn heat treatment. Use of a stainless steel jacket can simplify the design and fabrication because the special caution is not required for SAGBO. JAERI has already developed high manganese, JK2, whose thermal contraction from 300K to 4 K is almost the same as that of Incoloy: thus no change in the mechanical design of the CS is necessary. However, during the heat treatment, phosphorus enhances embrittlement of JK2. Carbon reduction and boron addition was considered to be a possible solution to mitigate the phosphorus effect. Jackets of low carbon and boron added JK2(JK2LB) were produced and tensile properties, fracture toughness, and crack propagation rate were measured at 4K. Elongation and fracture toughness at 4K after the heat treatment are 33% and 91 MPam $^{0.5}$ for the final jacket, which satisfy the ITER targets. JK2LB can be applied to the ITER CS.

JAEA Reports

Operational experiences of the super conducting magnet for a gyrotron of the JT-60U ECH system

Igarashi, Koichi*; Seki, Masami; Shimono, Mitsugu; Terakado, Masayuki; Ishii, Kazuhiro*; Takahashi, Masami*

JAERI-Tech 2003-030, 40 Pages, 2003/03

JAERI-Tech-2003-030.pdf:5.83MB

The JT-60U electron cyclotron heating (ECH) system can heat plasmas locally and drive a plasma current with four 1 MW-5 sec gyrotrons. The super conducting magnets (SCM) are required for oscillation of the gyrotron at a working frequency of 110 GHz. The SCM provides a high magnetic field of 4.5T at the cavity inside the gyrotron. This SCM system is characterized by (1) operation without liquid Helium owing to a 4 K-refrigerator applied to the magnetic coils, (2) easy maintenance. Operational experiences about the SCM system through a long term experiment for a high power gyrotron are very valuable. According to those operational experiences, it is clarified the 4 K-refrigerator should be renewed in oder to keep low temperature of the SCM. It is also found that 200 hours or less are required for the super conducting condition (5K) after long stopping time of the refrigerator up to 150 hours. This is useful information for making a plan about ECH experiments.

Journal Articles

First measurement of the quadrupole moment in the 2 state of $^{84}$ Kr

Osa, Akihiko; Czosnyka, T.*; Utsuno, Yutaka; Mizusaki, Takahiro*; Toh, Yosuke; Oshima, Masumi; Koizumi, Mitsuo; Hatsukawa, Yuichi; Katakura, Junichi; Hayakawa, Takehito; et al.

Physics Letters B, 546(1-2), p.48 - 54, 2002/10

https://doi.org/10.1016/S0370-2693(02)02660-6

Times Cited Count：10 Percentile：50.64(Astronomy & Astrophysics)

A $^{84}$ Kr beam was Coulomb-excited on a $^{98}$ Mo target and a $^{nat}$ Ta target. Six reduced matrix elements for 5 low-lying states were derived from the analysis using the least-squares code GOSIA. The quadrupole moment of the 2 was newly obtained. The measured quadrupole moment and the values are consistent with large-scale shell-model calculations which give a systematic description of ,=,50 isotones.