[en] A compact soft X-ray pulse height analyzer (PHA) to obtain spatial profile of electron temperature has been developed in the HT-7 superconducting tokamak. This diagnostic system was combined with recently introduced Silicon Drift Detector (SDD). SDD allow the measurement of X-rays at high-count rates and cooled only by a single-stage peltier element. The profiles of electron temperature with spatial resolution of 4.8 cm can be well derived in the pure ohmic heated and auxiliary heated discharge. The performance and first experimental results from the PHA system are presented

[en] Full text: EAST is a fully superconducting tokamak with a flexible poloidal field control system to accommodate both single null (SN) and double null (DN) divertor configurations, thus providing a unique platform to address power and particle exhaust issues for next-step fusion devices such as ITER and beyond. Significant progress has been made in EAST on both physics and engineering fronts toward steady state operations since the last IAEA Fusion Energy Conference. Long pulse diverted discharges well over 60 seconds have now been achieved in EAST by lower hybrid current drive with advanced wall conditioning, active divertor pumping using the newly installed internal toroidal cryopump, and real-time feedback control of plasma configurations using the iso-flux control technique developed by joint efforts from the DIII-D and EAST plasma control groups. The first systematic assessment of both SN and DN divertor performance has recently been made in EAST under Ohmic and L-mode operating conditions. Particle and heat fluxes at both inner and outer divertor target plates are lower for DN, as expected, but with stronger asymmetry favoring outer divertors. In addition, DN operation leads to an up-down asymmetry with greater power and particle fluxes to the divertors with their ∇B drift towards the X-point. Reversing toroidal field direction exhibits a strong influence on the observed divertor asymmetries. Contributions from various edge drifts are assessed using the SOLPS code with drifts and currents. To actively control power and particle fluxes at divertor target plates, localized divertor puffing of Ar has been carried out in EAST, leading to over 50% reduction of the peak heat flux at the outer divertor target plate without significantly affecting the core impurity content. Methane injection at various divertor locations (inner divertor, outer divertor and private region) has also been explored to quantitatively assess divertor screening for intrinsic carbon impurities. Further efforts will be dedicated to the active feedback control of gas puffing rates to maintain the divertor plasma in partial detachment conditions, which is essential for achieving higher power, long pulse operations during the next EAST experimental campaign starting in March, 2010. This presentation will highlight these advances. Comparisons will also be made with shorter pulse diverted tokamaks. (author)

[en] To operate divertor experiment, an in-vessel cryopump was installed on the EAST tokamak in 2008. It can limit gas impurity recycling from divertor region into core plasma area, and provide plasma density control with toroidally distributed high pumping speed. In this paper, the designing and manufacturing is basically described. Most parts are manufactured in ASIPP, except for some procedures such as laser cutting, plasma-spray coating, and pipe annealing. For this first in-vessel cryopump, liquid helium and nitrogen supplying system is upgraded. Functional tests for this cryopump show a good radiation shield and pumping capability. A campaign utilizing this device for divertor physics research has been successful.

[en] The construction of experimental advanced superconducting tokamak (EAST) was finished at the end of 2006 in Hefei, China. Its vacuum system, an important subsystem, has been commissioned in February 2006. The design and construction of this vacuum control system are described in this paper. The requirements for remote automation, distributed control and centralized management, high reliability and expansibility have been taken into account in the design. There are three levels of control in vacuum control system. The bottom level control is performed on the local instruments manually; the medium level control is based on Siemens S7-400 PLC; the top level control is conducted on IPCs with communication through profi_bus network. In addition remote handling and centralized monitoring could be realized by a remote control server. The control system could achieve pumping and fueling of the whole vacuum system. Besides that, it also includes the data acquisition of the pressure and temperature. The details are discussed on the monitoring of vacuum system states including cooling water, power and compressed air, etc., safeguards of plasma chamber and cryostat chamber and vacuum equipments, choosing of control modes corresponding to the plasma discharge and wall conditioning. At the end, the parts of EAST device protection system related to vacuum and gas injection system will also be introduced

[en] In-vessel components are important parts of EAST superconducting tokamak. It is include plasma facing components, passive plates, cryo-pumps, in-vessel coils, etc. The structure design, analyses and related R and D had been completed. Divertor is designed as up down symmetric to accommodate both double null and single null plasma operation. Passive plates can supply around 100ms time constant during plasma vertical movements. In-vessel coils are used for plasma vertical movements active control. Each cryo-pumps can supply around 45m³/s pumping speed for particle exhaust. Analyses shows when 1MA plasma current disrupt in 3ms EM loads caused by halo current will not bring unacceptable stress on divertor structure. Bolted divertor thermal structure can sustain 2MW/m² up to 60s operation if plasma facing surface temperature is limited to 1500 deg. C. Thermal testing and structure optimised testing have been made to demonstrate the analyses result. (author)

[en] EAST is a full superconducting tokamak, The main parameters have been described in many other papers. It has been complete assembly and vacuum test started from end of January. Although all of the TF coils and most of the PF coils have been tested their superconducting performance in testing facility the device will still be cool down to test all cryogenic system, TF coils and PF coils without vacuum vessel ports. All the ports, divertor and other in vessel components will be installed after cool down test. EAST divertor is up down symmetric to supply possibility operate both single null and double null plasma configuration. The geometry of the divertor is based on simulations using the B2-EIRENE Monte Carlo code. The reference configuration for the EAST divertor is an inner vertical target, an outer vertical target with an open private flux region and a dome below the X-point. The vertical target is inclined so as to intercept the magnetic field lines of the separatrix at an acute angle, giving deep inboard and outboard channels in which expect to establish a partially detached plasma regime. In this regime, while the plasma remains attached in the outer region of the SOL, the plasma is detached from the PFCs in the region near the separatrix causing the power profile to broaden and power to be radiated to other surfaces. Together with the lower end of each vertical target and dome forms a -V- cross-section that confines neutral hydrogenic particles in the divertor channels aids partial plasma detachment and particle exhaust. The plasma facing material for EAST divertor is a doped graphite developed in China. CuCrZr heat sink with cooling channels are bolted to stainless steel supports. Graphite tiles are bolted to heat sink with graphite foil improve thermal contact. In-vessel cryo-pumps are both install behind dome and outer vertical target for particles exhaust. EM loads bring by eddy current and halo current have been considered in divertor structure design and analyses. Different input plasma heating power has been considered in thermal analyse. (author)

[en] EAST is a non-circular advanced steady-state experimental device and the first entirely superconducting tokamak in the world. Vacuum system is one of the most important sub-systems of EAST device. Wall conditionings, such as baking, discharge cleaning and boronization, also play a very important role for the plasma operation. Due to Ion Cyclotron Resonance Frequency (ICRF) wall conditioning technique could be carried out in the presence of a high toroidal magnetic field, it is routinely used for wall cleanings on EAST. After the 2nd campaign in 2007, the plasma facing walls was modified to full carbon walls and vacuum system was upgraded to meet the requirement of particles exhaust. This paper will introduce the new statues of vacuum system, such as pumping, fueling and wall conditionings on EAST. Then the vacuum operation and wall conditioning in the 2008 campaign is introduced.

[en] The modelling studies of SOL-divertor plasmas in EAST tokamak with high heating and driving power have been carried out for the design of W/Cu divertor. The edge plasma code package SOLPS5.0(B2.5-Eirene) and Monte Carlo impurity transport code DIVIMP are used for the modelling. The plasma density at the core-SOL interface N_edge or the separatrix density n_sep is varied extensively in order to survey the operation of the divertor, the profiles of the plasma parameters and heat fluxes at the target plates of divertor have been obtained. For n_sep = 0.937 x 10¹⁹ 1/m³, the heating and driving power P_in = 14 MW on the device produces the peak heat flux at the outer target plate Q_t = 15.3 MW/m² with the SN configuration and the traditional divertor (no gas or radiation target). The radiative divertor modelling with Ne puffing and the transport modelling of W impurity from the target plates of divertor are also performed.

[en] The first systematic assessment of divertor performance was made in the EAST superconducting tokamak for both single null (SN) and double-null (DN) divertor configurations under Ohmic and L-mode plasma conditions. Particle and heat fluxes are higher at outboard divertor targets than those at inboard divertor targets for both SN and DN. However, the DN divertor configuration exhibits a much stronger in-out asymmetry favoring outer divertors. DN operation also leads to an up-down asymmetry with higher particle fluxes to the divertors with their ∇B drift toward the X-point. Reversing toroidal field direction shows a strong influence on the divertor asymmetries. The plasma exhibits a large amplitude broadband turbulence in the outer divertors for both SN and DN, which is significantly reduced in the inner divertors, especially for DN. This coincides with a broad divertor SOL profile on the outboard side. Initial comparisons are also made with SOLPS-B2/EIRENE modeling.

[en] The EAST tokamak was built to carry out long pulse plasma discharges up to 1000 s. To facilitate this, an active divertor pumping (ADP) system was installed under the lower outer (LO) divertor target plate (DTP) for plasma density control and impurity exhaust. The ADP system was used in the first EAST divertor physics campaign, and achieved very promising results on neutral gas particle exhaust and recycling control. The system can improve divertor screening for neutrals and reduce the ratio H/(H + D), and appears to be effective at controlling the main chamber hydrogenic recycling. The influence of ADP on lower inner (LI) and LO DTP is observed. Furthermore, we attempt to find an optimized strike point to mitigate DTP heat load during ADP operation. This article reports on these interesting results, in particular, for the lower single null (LSN) plasma configuration.