EAST Data processing of divertor probes on EAST Jun Wang, Jiafeng Chang, Guosheng Xu, Wei Zhang, Tingfeng Ming, Siye Ding Institute of Plasma Physics, Chinese Academy of Sciences P.O.Box 1126, Hefei, Anhui ( ASIPP JSPS-CAS Core University Program Seminar on Production and Control of High Performance Plasmas with Advanced Plasma Heating and Diagnostic systems, November, 2008, Lijiang, Yunnan, China

Outline (1) Introduction (2) Experimental results from TLTPS (3) Improved divertor probe experiments (4) Summary EAST ASIPP

Main Parameters of the EAST NominalUpgrade B o 3.5 T 4.0 T I P 1 MA 1.5 MA R o 1.7 m1.9 m a0.4 m0.45 m R/a K x δ x Heating and Driving: ICRH3 MW6 MW LHCD3.5 MW8 MW ECRH0.5 MW1.5 MW NBI8 MW Pulse length 1000 s Configuration Double-null divertor Single-null divertor EAST ASIPP

The EAST machine assembly (Jan. 2006) EAST ASIPP The first hydrogen plasma discharge (Sep. 26, 2006) The first divertor hydrogen plasma discharge (Jan. 22, 2007) The first divertor deuterium plasma discharge for isoflux control and a full graphite wall (Aug. 2, 2008)

Outline (1) Introduction (2) Experimental results from TLTPS (3) Improved divertor probe experiments (4) Summary EAST ASIPP

TLTPS Design goals ： Measure electron temperature, electron density, particle flux, and heat flux spatiotemporal distribution in the divertor region. Feature: Consisted of 60 fixed divertor probes, configurable as 20 triple probes. Poloidal resolution 2 cm at the divertor target plates. Time resolution 200  s. Continue operation 1000 s on the 7 MW/m 2 heat load during discharge. EAST ASIPP Tilting Langmuir triple probes (TLTPS)

Structure of divertor probeLayout of Langmuir probe array TLTPS EAST ASIPP Some experiments of probe characteristics measured at distinct angle in DITE showed that the ion saturation current no longer saturated at small angleθ, where θ is the angle between the magnetic field and the probe surface. In consideration of at small angle, each surface of the triple probes on EAST was designed tilting, the Langmuir probe installed in the divertor plate is approximately 9º between tilting section of the probe and its divertor target plate.

TLTPS EAST ASIPP Probes installed in the divertor target plate The triple probes are built into the divertor target plates and the tips are spaced toroidally to ensure plasma uniformity, The typical spacing between groups of triple probes is 2cm poloidally. the advantage of the triple probes method is high temporal resolution since positively biased potential, floating potential and ion saturation current can be measured simultaneously.

Experimental results from TLTPS EAST ASIPP Hydrogen plasmas were initially obtained in September 2006, making it the first of the EAST tokamak to come into operation, then divertor configuration plasmas for hydrogen was achieved successfully during 2nd experimental campaign in January 2007, the first divertor discharge on EAST was pulse No. 3478(the evolution of the ion saturation current density).

EAST ASIPP Evolution of the measured main plasma and divertor plasma parameters : (a) plasma current, (b) line-average density, (c)-(k) ion saturation current of inboard divertor probes from probe 1 to 9. Typical ohmic hydrogen plasma for sheath-limited regime with near double null divertor configuration, shot No. 3758, has been analyzed. Plasma current is approximately 200kA, toroidal magnetic field is 2T, and pulse duration is about 3.5s including discharge plateau time 2.2s. Shot 3758 shape divertor configuration at 1.8s after limiter configuration, the inner strike point sweeps from probe 1 at 2.5s to probe 7 at 3.3s by the fitting codes of IPPEQ (ASIPP). 3758# Experimental results from TLTPS

EAST ASIPP Evolution of the measured plasma current and electron density: (a) plasma current, (b)-(j) measured electron density from probe 1 to 9. Evolution of the measured plasma current and electron temperature: (a) plasma current, (b)-(j) measured electron temperature from probe 1 to 9. Experimental results from TLTPS

EAST ASIPP Evolution of the measured plasma current and power flux: (a) plasma current, (b)-(j) measured power flux from probe 1 to 9. Evolution of the measured plasma current and particle flux: (a) plasma current, (b)-(j) measured particle flux from probe 1 to 9. Experimental results from TLTPS

Outline (1) Introduction (2) Experimental results from TLTPS (3) Improved divertor probe experiments (4) Summary EAST ASIPP

Design goals ： Measure electron temperature, electron density, particle flux, and heat flux spatiotemporal distribution in the divertor region. Feature: Consisted of 222 fixed divertor probes, configurable as 74 triple probes. Poloidal resolution 2 cm for inboard target plate and poloidally 1 cm for outboard target plate of both upper and lower divertor. EAST ASIPP Domed triple probes Domed divertor probes

Structure of divertor probeLayout of Langmuir probe array EAST ASIPP Domed divertor probes

EAST ASIPP Typical ohmic deuterium plasma with near-double null divertor configuration, shot no. 8868, has been analyzed in detail. The plasma current is approximately 0.3 MA, the toroidal magnetic field is 2 T and the pulse duration is 3.9 s including a discharge plateau time 2.8 s. In shot no. 8868, RZIP control and programmed shaping control is used for up to 2.0 s, and then partial isoflux control at 2.0 s to full isoflux control at 2.7 s is put into operation. The inner strike point for upper divertor sweeps from probe UI15 at 2.6 s to probe UI11 at 2.8 s, then from probe UI11 to UI15 at 3.0s; the outer strike point for upper divertor sweeps from probe UO18 at 2.5 s to probe UO11 at 2.7 s, then from probe UO11 to UO18 at 2.9s. 8868# Isoflux control and a full graphite wall

EAST ASIPP Evolution of the measured main plasma and upper divertor plasma parameters, where the following are plotted from top to bottom: (a) plasma current, (b) line- average density, (c)-(g) ion saturation current density of inboard divertor probes from probe UI11 to UI15. Evolution of the measured main plasma and upper divertor plasma parameters, where the following are plotted from top to bottom: (a) plasma current, (b) line- average density, (c)-(j) ion saturation current density of outboard divertor probes from probe UO11 to UO18. Isoflux control and a full graphite wall

EAST ASIPP Evolution of the measured ohmic power, line- average density and edge plasma parameters of inner target plates in the upper divertor at strike points: (a) ohmic power, (b) line-average density, (c) electron temperature, (d) electron density, (e) particle flux and (f) power flux. Evolution of the measured ohmic power, line- average density and edge plasma parameters of outer target plates in the upper divertor at strike points: (a) ohmic power, (b) line-average density, (c) electron temperature, (d) electron density, (e) particle flux and (f) power flux. Isoflux control and a full graphite wall

Summary (1) Divertor plasma discharges have also been achieved in the EAST tokamak in January of 2007 ; (2) The TLTPS have been successfully used for measuring divertor hydrogen plasma parameters at the target plates for a full stainless steel wall; (3) The domed divertor probes have been successfully used for determining deuterium plasma parameters at the target plates for isoflux control and a water-cooling graphite wall; (4) Towards long-pulse high power plasmas, with high power heating (3.5MW LH+IC), and new diagnostics will be available in the next experimental campaign. EAST ASIPP

EAST ASIPP Thanks for your attention!