22P134-P
Recent Development of the Plasma Diagnostics for JT-60SA
JT-60SAにおける計測開発の現状
Kiyoshi Itami, Kouji Shinohara, Takaki Hatae, Kensaku Kamiya, Masakatsu Fukumoto,Tomohide Nakano, Maiko Yoshida, Hiroshi Tojo, Hiroyuki Arakawa, Shigeharu Kokusen,
Takashi Hamano, Hisashi Saeki, Takaaki Suzuki, Nobuyuki Asakura, Akihiko Isayama,Naoyuki Oyama, Manabu Takechi, Go Matsunaga, Shinji Sakurai, Yusuke Shibama, Kei Masaki
伊丹潔、篠原孝司、波多江仰紀、神谷健作、福本正勝、仲野友英、吉田麻衣子、東條寛、荒川弘之、石仙茂晴、
濱野隆、佐伯寿、鈴木隆博、朝倉伸幸、諌山明彦、大山直幸、武智学、松永剛、櫻井真治、芝間祐介、正木圭Japan Atomic Energy Agency, Mukoyama 801-1 Naka 311-0193, Japan
日本原子力研究開発機構 〒311-0193 那珂市向山801-1
Recent design activities of the plasma diagnostic systems for JT-60SA are presented. Toward finalizationsof the cryostat design and arrangements of all the systems in the JT-60SA torus hall, design study of theport plug and arrangement of diagnostic around the cryostat port have progressed significantly. Divertor
Langmuir probes are manufactured in FY2011. In addition to the diagnostic systems which have been
already defined, advanced diagnostics are studied.

1. Introduction
Plasma diagnostic systems in JT-60SA[1] measureaccurate profiles of main plasma and divertor plasma
parameters and to provide real-time data to the plasma
control system in order to self-regulating high βN
plasmas in steady state [2]. The plasma diagnosticsystems in JT-60SA has been classified into three
categories, such as the diagnostic systems for“Machine Protection and Operation”, the diagnostic
systems for “Fundamental Parameter Measurement” andthe diagnostic systems for “Physics Understanding”. This
paper presents the recent progress of the design activityof the plasma diagnostic systems for JT-60SA.

spectroscopy) are enclosed in the P2 port plug. Vacuum
windows in the P2 port plug are placed behind thestabilizing plate and then the front-optics for Thomson
scattering system and CXRS system view the plasma
through an aperture of the stabilizing plate and RWM(resistive wall mode) coil. Arrangement of vacuum
windows in this port plug is designed in combination
with toroidal width of the aperture, so that necessary
field of view is possible through aperture of thestabilizing plate. Lower part of this horizontal port ductis used by current feeders for RWM coils and EFC (errorfield correction) coils.

2. Port Plug Design Activity
Toward finalizations of the cryostat design andarrangements of all the systems in the JT-60SA torus hall,design study of the port plug and arrangement of
diagnostic around the cryostat port have progressedsignificantly. Since port plug structure for optical
diagnostics in JT-60SA is long and large, the port plug
design must take into account of installation andmaintenance by machines in limited space around thecryostat port.
Use of the P2 horizontal port section is shown in
Fig. 1, as a typical case of the sharing space among theplasma diagnostics and in-vessel components. Please
note that tiles which cover the stabilizing plate andRWM coils are not drawn in this figure. Since distancefrom the plasma edge to the vacuum boundary of thecryostat port is ~ 3m, front-end components of optical
diagnostics are enclosed in port plugs. Collection opticsof Thomson scattering measurement and back groundlight optics of CXRS (charge exchange recombination

Fig. 1Cut-away and front view of the P2 horizontal port.
Design activity of shutters for vacuum windows is also
progressed, recently. Head of the P2 port plug is shownin Fig. 2. Diameter of the vacuum window is as large
as 40 cm and a shutter, which must withstand electro
magnetic forces due to the plasma disruptions and heat
flux from the plasmas, is designed to be driven
mechanically by wires.

Fig. 2 Design of shutter in the P2 horizontal port plugfor Thomson scattering measurement.

3. Divertor Langmuir Probes
Divertor Langmuir probes are very useful diagnostics
in order to identify diveror configurations and tocompare with equilibrium by the magnetic measurementin the initial phase of the JT-60SA experiment. Langmuirprobe tips are placed between target tiles and distributedin the divertor cassette, as shown in Fig 3. Four sets of
40 probes are installed at the different toroidal locations.

Fig. 3
Langmuir probes installed in the divertor target.
Arrow shows direction of the plasma flow.
Tips of the probe are roof like shape and made of CFC.
The surface area which collects the current from plasmas
is ~6 mm2. The connectors made of nickel are brazed at
the bottom of the collectors to which the MI cables areconnected. It is expected that these target probes
withstand the heat flux of 1 MW/m2 for 100 s or 10
MW/m2 for 5 s. Those probe tips will be manufactured inFY2011.
The divertor Langmuir probes is also used to measureplasma parameters in divertor region, such as, electron
density (ne), electron temperature (Te), floating potential(Vf) and ion saturation current (Isat). These plasma
parameters are essential to produce and to control thepartially detached divertor plasmas. Studies ofplasma-material interaction, such as erosion anddeposition of wall materials and retention and recyclingof fuel particles, also require this diagnostic system.

4. Optics for Visible/IR First wall TV system
The Visible/IR First wall TV system must provide awide-angle view in both visible and infrared range ofwavelength on both the main chamber and divertor area.

This diagnostic is essential for safe operation with realtime protection during the higher input power(NBI+ECRF) heating. The 3-Dimensinal effect of ELM
interaction on the JT-60SA main chamber is also
attractive for physics studies.
A new idea for the front end optics of the periscope isbeing proposed. In the new design, no aspheric mirror
are used as the conventional design, such as that used inJET. Two set of spherical mirrors (plus two flat mirrors),
instead of a aspheric mirror, makes it possible to reduce atolerance
formanufacture/installation.
Anotheradvantage is a blind spot in the field of view, inherent in
the conventional optical design, can be avoided. R&D ofthe periscope applying the new optical design is planned.

4. Advanced diagnostics
In addition to the diagnostic systems which have been
defined in WBS system, the several plasma diagnostic
systems which have advanced features are being studied.
A crystal spectrometer is under consideration for
installation at the P10 horizontal port, which is sharedwith the VUV spectrometer and the neutron profile
monitor as shown in Fig.4. The primary purpose of thisspectrometer is to measure the ion temperature at theplasma center in high density discharges such as
Scenario 2 (electron temperature 8 keV and electron
density 1x1020 m-3), instead of the CXRS system because
the neutral beam will not penetrate into the plasma core.
As a diagnostic gas, krypton is found to be a choicebecause a steady-state impurity transport analysis
indicated that full striped argon is dominant at the plasma
center, resulting in no line emission and that neon-likexenon exists at the plasma center in a limited electron
temperature range between 5 and 9 keV, resuling inlimitation of the ion temperature measurement. In order
to measure the Doppler broadening of Kr XXXV (1s2 1S0– 1s2p 1P1: l = 0.09455 nm), a Johann type crystal
spectrometer with a Rowland circle diameter of 3 m isunder consideration.

Fig. 4
Viewing chords of the VUV and crystal spectrometers
References[1] S. Ishida et al., Proc. of the 23rd Fusion Energy
Conf., 2010, OV/P-4.
[2] Y. Kamada et al., Journal of Plasma and Fusion
Research SERIES Vol. 9 (2010) 641.