Since the last IAEA-FEC in 2021, significant progress on the development of long pulse steady state scenario and its related key physics and technologies have been achieved, including the reproducible 403 s long-pulse steady-state H-mode plasma with pure radio frequency (RF) power heating. A thousand-second time scale (similar to 1056 s) fully non-inductive plasma with high injected energy up to 1.73 GJ has also been achieved. The EAST operational regime of high beta(P) has been significantly extended (H-98y2 > 1.3, beta(P) similar to 4.0, beta(N) similar to 2.4 and n(e)/n(GW) similar to 1.0) using RF and neutral beam injection (NBI). The full edge localized mode suppression using the n = 4 resonant magnetic perturbations has been achieved in ITER-like standard type-I ELMy H-mode plasmas with q(95) approximate to 3.1 on EAST, extrapolating favorably to the ITER baseline scenario. The sustained large ELM control and stable partial detachment have been achieved with Ne seeding. The underlying physics of plasma-beta effect for error field penetration, where toroidal effect dominates, is disclosed by comparing the results in cylindrical theory and MARS-Q simulation in EAST. Breakdown and plasma initiation at low toroidal electric fields (<0.3 V m(-1)) with EC pre-ionization is developed. A beneficial role on the lower hybrid wave injection to control the tungsten concentration in the NBI discharge is observed for the first time in EAST suggesting a potential way toward steady-state H-mode NBI operation.

Since the last IAEA Fusion Energy Conference in 2016, the EAST physics experiments have been developed further in support of high-performance steady-state operation for ITER and CFETR. First demonstration of a >100s time scale long-pulse steady-state scenario with a good plasma performance (H-98(y2) similar to 1.1) and a good control of impurity and heat exhaust with the upper tungsten divertor has been achieved on EAST using the pure radio frequency (RF) power heating and current drive. The EAST operational domain has been significantly extended towards a more ITER and CFETR related high beta steady-state regime (beta(p) similar to 2.5 and beta(N) similar to 1.9 of using RF and NB and beta(p) similar to 1.9 and beta(N) similar to 1.5 of using pure RF). A large bootstrap current fraction up to 47% has been achieved with with q(95) similar to 6.0-7.0. The interaction effect between the electron cyclotron resonant heating and two lower hybrid wave systems has been investigated systematically, and applied for the improvement of current drive efficiency and plasma confinement quality in the steady-state scenario development on EAST. Full edgelocalized mode (ELM) suppression using the n = 2 resonant magnetic perturbations has been achieved in ITER-like standard type-I ELMy H-mode plasmas with a range of the edge safety factor of q(95) approximate to 3.2-3.7 on EAST. Reduction of the peak heat flux on the divertor was demonstrated using the active radiation feedback control. An increase in the total heating power and improvement of the plasma confinement are expected using a OD model prediction for a higher bootstrap fraction. Towards a long-pulse, high bootstrap current fraction operation, a new lower ITER-like tungsten divertor with active water-cooling will be installed, together with further increase and improvement of heating and current drive capability.

The Radial X-ray Camera (RXC) is a diagnostic in Equatorial Port 12 (EQ#12) of International Thermonuclear Experimental: Reactor (ITER). Normally, the operating temperature of detector on RXC system shall be lower than 75 degrees C. But the detectors on some part of RXC system will have to face a high temperature of 250 degrees C during baking of ITER, as a result of which case detectors will be easily damaged. Due to the harsh environment, cooling for RXC system is necessary. In order to verify the effect of gas cooling, the related research and experiments are being carried out. This article focuses on the analysis of the architecture and heat transfer capacities of the cooling test platform. According to the analysis results, the solution of the cooling platform is introduced and a cooling test platform is established. Also, a Data Acquisition (DAQ) system is developed based on Experimental Physics and Industrial Control System (EPICS) framework. The experiment results based on the cooling test platform provide support for the cooling system design of RXC system.

Soft X-ray camera physical diagnosis is widely used in Tokamak.The upper temperature of Soft X -Ray detector is 75℃,while baking,the ambient temperature would reach 250℃which can easily break the de-tector.So the cooling system is indispensable.In this paper, the thermal load power of detectors is analyzed and a hybrid refrigeration test platform which combined water and helium is built innovatively based on calcula -tion results and cooling conditions.Experimental results show that the cooling platform runs stably,it not only meets the cooling demand of soft X -ray diagnosis,but also provides reference for other cooling system design of fusion diagnosis.

The signal acquisition amplifier is an important part of the soft X camera diagnosis system,which is installed in the PXI chassis in the form of board card to improve integration.Due to the poor quality and noise of the power supplied by the PXI chassis,the acquisition of weak signal would be interfered.In order to improve the quality of the power supply and reduce noise,this article mainly focuses on the optimization of PXI power supply,the power impedance and decoupling capacitor are analyzed;the EMI power filter is designed;resonance between power supply layer and ground layer in PCB are analyzed.The experimental results show that the noise of power supply is reduced and the stability of power supply is improved.

The Radial X-ray camera (RXC) is a diagnostic for the ITER tokamak. During baking and operation of ITER, the detector environment temperature will be up to 240 degrees C, whereas the detectors must be kept below 70 degrees C. Therefore, cooling of the detectors mounted in the camera is critical and necessary. In order to verify the effect of gas cooling for RXC detectors, a relevant test has been designed. Since the outcome of this test will be the supply of the RXC cooling system, the ITER Instrument and Control strategy was selected. Therefore, a Data Acquisition (DAQ) system was developed based on the Experimental Physics and Industrial Control System (EPICS) framework, which implements functions for real-time data acquisition, temperature control, supervision, and archiving. Moreover, it is easy to configure control information according to user requirements. Also, some linear devices were used in the reconfiguration of EPICS. This technical note presents the entire architecture of the DAQ system and the details on the design of EPICS. The system has been implemented, and has provided reliable data for the experiment.

As one of the most important physical diagnosis of ITER,Radial X-Ray Camera (RXC) will face a 250℃ high temperature when ITER is baking.Therefore,it is very important for the cooling of the detectors in Radial X-Ray Camera as whose ceiling temperature is 75℃.In order to verify the effect of cooling,an EPICS based monitor and control system is developed for the management of cooling experiment process and results.The functions for data acquisition,storage,retrieval and device control are realized with the help of monitor and control system.The most creative work is that all the acquisition and control algorithms are achieved through EPICS.In this paper,the functional requirements,monitoring parameters,hardware and software design and test results of the monitor and control system are described in detail.Test results show that the monitor and control system is stable.It not only provides reliable support for the cooling experiment of RXC,but also gives references for the popularization of EPICS in monitoring system.

Background: The primary diagnostic role of radial X-ray camera (RXC) includes measuring low (m,n) magnetohydrodynamic modes, sawteeth and disruption precursors, H-mode, edge-localized modes, and L-H transition. Purpose: According to the soft X-ray weak signal detection requirements of international thermonuclear experimental reactor (ITER) tokamak, considering the harsh electro-magnetic environment and long distance transmission of signal, some appropriate electromagnetic protection measurements must be took in the design of soft X-ray diagnosis system in order to suppress circuit noise. Methods: In this thesis, a differential circuit structure has been designed to accomplish current-to-voltage conversion, and studying the electro-magnetic compatibility is the point. Results: Associated with experimental test and complied with three factors of electro-magnetic interference, the paper has discussed the application of shielding, grounding, filtering, and printed circuit board (PCB) layout methods in circuit, and completed the circuit requirements of system miniaturization, high parameters with quantity of 32 channels per PCB board, gain of 107 V·A-1, width of 120 kHz, and noise of 8 mV. Conclusion: The effectivedetection of weak current signal and steady performance are proved by test results. The effect of electromagnetic protective measurements adopted is reasonable and obvious.

The ITER radial X-ray camera (RXC), which is installed in the middle diagnostics shield module (DSM) of equatorial port plug 12, is an important piece of diagnostic equipment in the tokamak system. A cooling circle is vital for RXC detectors because it can protect them from being damaged during the DSM baking phase when the temperature reaches 240 ( +/- 10)degrees C. Helium is used as a cooling medium in this cooling circle owing to its low activation and good heat exchange with copper. To increase the gas resistance and expand the heat transfer area, a labyrinth structure is introduced into the internal structural design of a heat exchanger. In this paper, an analysis of the heat load of the RXC and its cooling circle is presented, along with the thermal simulation and test results. Thermal simulation results indicate that the cooling circle design can meet the requirements. A test platform is built to validate the cooling circle design. The experimental results are presented, and the problems encountered during the testing are analyzed. The test results indicate that the maximum temperature of the detector is lower than 65 degrees C with the cooling circle during the platform baking phase, which is lower than the detector operation temperature limit of 75 degrees C.

ITER is the first international experimental nuclear fusion device. In the project, the RAMI approach (reliability, availability, maintainability and inspectability) has been adopted for technical risk control to mitigate all the possible failure of components in preparation for operation and maintenance. RAMI analysis of the ITER Radial X-ray Camera diagnostic (RXC) system during preliminary design phase was required, which insures the system with a very high performance to measure the X-ray emission and research the MHD of plasma with high accuracy on the ITER machine. A functional breakdown was prepared in a bottom-up approach, resulting in in a bottom-up approach, resulting in the system being divided into 3 main functions, 6 intermediate functions and 28 basic functions which are described using the IDEFO method. Reliability block diagrams (RBDs) were prepared to calculate the reliability and availability of each function under assumption of operating conditions and failure data. Initial and expected scenarios were analyzed to define risk-mitigation actions. The initial availability of RXC system was 92.93%, while after optimization the expected availability was 95.23% over 11,520 h (approx. 16 months) which corresponds to ITER typical operation cycle. A Failure Modes, Effects and Criticality Analysis (FMECA) was performed to the system initial risk. Criticality charts highlight the risks of the different failure modes with regard to the probability of their occurrence and impact on operations. There are 28 risks for the initial state, including 8 major risks. No major risk remains after taking into account all the actions. It was assessed that the RAMI analysis results meet the project requirement during preliminary design phase and the result will be qualified further when the system design is more mature. (C) 2016 Elsevier B.V. All rights reserved.

On the EAST tokamak, during whole off-axis LHCD (low hybrid current drive) limiter discharge, inverted sawteeth oscillations on the SXR (soft X-ray camera) signals appear continuously, and no positive sawtooth is observed. It is thought that this phenomenon is caused by the curvature pinch, though it could partly be explained by the electron temperature profile observed on the PHA (soft X-ray pulse height analyzer) system. The off-axis LHCD and Ohmic heating generate a non-monotonic q profile. According to the curvature pinch effect, this q profile leads to a special electron density profile that has a valley ring. The non-monotonic q profile and the special electron density profile lead to this interesting phenomenon.

Runaway electrons produced during minor disruptions, which are confirmed by the hard x-ray system and the runaway energy spectrum system, are observed by a soft x-ray camera on the HT-7 Tokamak. In this observation, the soft x-ray system can also provide the size information and the position information of the runaway electron current directly from the signal information on the chord. This observation implies that the soft x-ray system can provide the control system with the physical information of the runaway electron current on future devices to avoid electrons hitting the first wall.

For the soft X-ray and extreme ultra-violet(XUV) diagnostic systems in the magnetic confinement fusion device(EAST Tokamak), ensuring the satisfactory signal-to-noise ratio of their physical signals requires appropriate electromagnetic protection for their weak signal processing circuits(systems). Hence, on the basis of experience and existing experimental results, we systematically studied the acquisition process of the physical signal, and focused on developing the protective measures. Through lab tests, we determined some optimum protective measures including shielding, grounding, and filtering, which were then applied to the soft X-ray and XUV diagnostic systems. The results show that, after appropriate measures are applied to the signal processing circuit and the entire systems, the gain and bandwidth of the systems are increased to 106 and 100 kHz, respectively, and their noise is reduced to about 10 mV. Therefore, the designed circuit scheme is feasible, and the adopted electromagnetic protective measures are effective.

Radial X-ray camera (RXC) is a diagnostic device planned to be installed in the ITER Equatorial Port #12. Beryllium window will be installed between the inner and Outer camera of RXC, which severs as the transmission photocathode substrate and also the vacuum isolation component. In this paper the design and manufacture process of two types of beryllium windows were introduced. Although 50 mu m thickness of beryllium foil is the best choice, the 80 mu m one with X-ray threshold of 1.34 key was selected for safety consideration. Using the intermediate layer (low purity of beryllium) between the beryllium foil and the stainless steel base flange is an effective strategy to limit the welding thermal deformation and thermal stress of the thin foil caused by bonding between different materials. By using ANSYS software, the feasibility of the aperture design was analyzed and validated. Metal sealing ring was applied in the mechanical clamped beryllium window for its good stability under high temperature and neutron radiation. Although both of the hollow metal sealing ring with 0.03 mm silver coating and the pure silver sealing ring can satisfy the sealing requirement, the later one was chosen to produce the final product. Two hours 240 C high temperature baking test, two hours 3.3 Hz vibration test and fatigue test were performed on the two types of beryllium windows. Based on the tests results, the two types of beryllium windows could stand the high temperature baking during the wall conditioning phase of ITER tokamak and the vibration during transportation without causing large leakage. Both of the two types of beryllium windows could bear impact load (0.1 MPa pressure difference) for many times without failure. (C) 2013 Elsevier B.V. All rights reserved.

Beryllium (Be) window is a key component of the ITER radial X-ray camera (RXC). The Be window presented in this paper has a mechanical clamping structure, the thickness of the Be foil is 80 μm, and the X-ray threshold of the 80 μm Be foil is 1.24 keV. A honeycomb support is designed and applied to strengthen the Be foil to prevent it from breakage when it is exposed to 1 atm perssure. Based on analysis results, the hole diameter of the support is chosen as 4 mm. A metal seal is used to isolate the vacuum on two sides of the Be window, the hollow metal sealing ring ensures the He leakage rate of the Be window being lower than 6×10−10 Pa·m3·s−1. Baking (240°C, 2 h) and vibration(3.3 Hz, 2 h) tests are carried out and the feasibility of the Be window's sealant in these situations is tested. The Be window has good stability that can save maintenance cost as well as enhancing the safety of the RXC.

Pressure gradient driven m = 1 internal kink mode destabilization that follows an L-H transition is observed in the operational region of the EAST tokamak, which manifests in periodic oscillations in soft x-ray (SXR) and Mirnov coil signals. Using tomography with the high resolution soft x-ray detection array, we find that the rotation direction of the 1/1 kink mode is in the ion diamagnetic drift direction in poloidal cross-section. A large displacement of the hot core is attributable to the shift of the 1/1 internal kink mode. In contrast to stationary oscillations with fixed frequency, various frequency chirping behavior is observed with this 1/1 kink mode. Furthermore, we also occasionally observe that a 2/1 neoclassical tearing mode (NTM) is triggered by a 1/1 internal kink mode via mode coupling in a high-performance plasma. The spatial structure of a 2/2 mode, which is the harmonic mode of the 1/1 kink mode, is also presented in this paper. Large amounts of medium-Z impurities accumulate in the central plasma region where the 1/1 kink mode instability bursts. Finally, we also find that the frequency beating associated with a 1/1 kink mode is a consequence of plasma rotation. Based on all of these observations, we propose that the plasma pressure gradient, the driving force in kink modes, is plausibly the product of an intense concentration of impurities, which are related to plasma rotation.

In this paper, the singular value decomposition (SVD) method as a filter is applied before the tomographic inversion of soft-X-ray emission. Series of 'filtered' signals including specific chronos and topos are obtained. (Here, chronos and topos are the decomposed spatial vectors and the decomposed temporal vectors, respectively). Given specific magnetic flux function with coupling m = 1 and m = 2 modes, the line-integrated soft-X-ray signals at all chords have been obtained. Then m = 1 and m = 2 modes have been identified by tomography of simulated 'filtered' signals extracted by the SVD method. Finaly, using the experimental line-integrated soft-X-ray signals, m = 2 competent mode of complex magnetohydrodynamics(MHD) activities during internal soft disruption is observed. This result demonstrates that m = 2 mode plays an important role in internal disruption (Here, m is the poloidal mode number).

The rapid collapse of a sawtooth oscillation which is characterized by the absence of any discernible precursor oscillation in the HT-7 tokamak has been observed in detail on a fast time scale. The contour plot of the raw data of soft-x-ray signals shows that sawtooth crash simultaneously on both the high field side and the low field side with symmetry. Only spatial structure of sawtooth exists in the whole sawtooth period. A larger heat outflow and profile of emission intensities flatten during sawtooth crash by means of soft x-ray tomography. The plausible interpretation is the stochastization of magnetic field lines lead to a transition from semicollisional to collisionless reconnection regimes during non-linear pre-crash phase in which the growth rate is rapidly increased and no any discernible precursor oscillation.

International thermonuclear experimental reactor (ITER) soft x-ray (SXR) diagnostic camera is an indispensible component used to measure signal intensity of SXR, which can reflect the internal properties of plasma. In this paper, the preliminary structural design and working principle of SXR camera is demonstrated, to investigate its seismic performance, modal analysis has been performed to obtain natural frequencies, effective mass and mode of vibration in first ten modes by means of ANSYS software. Then according to two parallel seismic analysis methods used in ITER, the calculations have been performed and the corresponding results have been illustrated respectively, the stress intensity and displacement are all within the allowable margin, which indicates that the design is reasonable and feasible. It will also provide beneficial reference for subsequent work.

In this paper,the singular value decomposition(SVD) method as a filter is applied before the tomographic inversion of soft-X-ray emission.Series of ’filtered’ signals including specific chronos and topos are obtained.(Here,chronos and topos are the decomposed spatial vectors and the decomposed temporal vectors,respectively).Given specific magnetic flux function with coupling m = 1 and m = 2 modes,the line-integrated soft-X-ray signals at all chords have been obtained.Then m = 1 and m = 2 modes have been identified by tomography of simulated ’filtered’ signals extracted by the SVD method.Finaly,using the experimental line-integrated soft-X-ray signals,m = 2 competent mode of complex magnetohydrodynamics(MHD) activities during internal soft disruption is observed.This result demonstrates that m = 2 mode plays an important role in internal disruption(Here,m is the poloidal mode number).