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Nishitani, Takeo; Ishikawa, Masao; Kondoh, Takashi; Kusama, Yoshinori; Asai, Keisuke*; Sasao, Mamiko*
AIP Conference Proceedings 988, p.267 - 274, 2008/04
no abstracts in English
Sugie, Tatsuo; Ogawa, Hiroaki; Kasai, Satoshi*; Kusama, Yoshinori
AIP Conference Proceedings 988, p.218 - 221, 2008/04
The detailed design of the Impurity Influx Monitor (divertor) has been carried out to provide the measurement capability in the harsh environment. The potential damaging effects for the first mirrors mounted close to the plasma are the formations of coatings of impurities and the deposition of the dust. Mitigating measures to minimize the degradation of their performance by these effects, such as changes in the reflectivity, are adopted: for example, the plasma is viewed through a small aperture, and baffle plates are inserted in front of the first mirrors. However, it will not be possible to prevent the degradation completely. It is important to know the change of the sensitivity of the optical systems. It is not feasible to install a light source in the vacuum chamber of ITER during operations and so an alternative method is needed. The in-situ calibration system using a micro retro-reflector array has been developed as a possible method.
Koide, Yoshihiko
AIP Conference Proceedings 988, p.413 - 419, 2008/03
An economically attractive DEMO requires a steady-state plasma with high bootstrap-current fraction fBS and high normalized beta. Development in diagnostic application to control of such advanced tokamak plasma is in progress worldwide, which will be discussed in this talk. For example, plasmas with a fraction of DEMO-relevant fBS of 70% have been sustained for 8s in JT-60 by real-time control of toroidal plasma flow based on the current profile measurement by which moderate relaxation of pressure gradient is induced, resulting into avoidance of collapse triggered at integer q
surfaces. In this experiment, change in the q value as a response to the pressure-gradient control was found to become big in the high fBS regime. Issues on (1) application of the present-day control methods to DEMO with self-heating, and (2) limitation of port space for the advanced control to keep a sufficient tritium-breeding ratio are also addressed.
Ishikawa, Masao; Itoga, Toshio*; Okuji, Toshio*; Nakohostin, M.*; Shinohara, Koji; Baba, Mamoru*; Nishitani, Takeo
AIP Conference Proceedings 988, p.295 - 298, 2008/03
A line-integrated neutron emission profile is routinely measured using Stilbene neutron detector in JT-60U tokamak. Although the SND has many advantages as a neutron detector, the maximum count rate is limited up to 10
cps due to the analog pulse shape discrimination (PSD) circuit. To overcome this issue, a digital signal processing (DSP) system using a flash ADC has been developed In this system anode signals from photomultiplier of the SND are directory stored and digitized. Then, the PSD between neutrons and 
rays is performed using software. The DSP system has been installed in the vertical neutron collimator system inJT-60U and applied to deuterium experiments. It is confirmed that the PSD is sufficiently performed and collimated neutron flux is successfully measured with count rate up to 10
cps without the effect of pileup of detected pulses.
