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Two experiment campaigns were conducted on HL-2A tokamak in 2003 and in 2004 after the first plasma was obtained at the end of 2002. Progresses in many aspects have been made, especially in the divertor discharge and feedback control of plasma configuration. Up to now, the following operation parameters have been achieved: Ip = 320 kA, Bt = 2.2 T and discharge duration T d = 1580 ms. With the feedback control of plasma current and horizontal position, an excellent repeatability of discharge has been achieved. The tokamak has been operated at both limitor configuration and single null (SN) divertor configuration. The HL-2A SN divertor configuration is simulated with the MHD equilibrium code SWEQU. The divertor experiment results were compared with the simulation results obtained with B2. When the divertor configuration is formed, the impurity radiation in main plasma decreases remarkably. The plasma performances are improved significantly after siliconization.

Understanding of the anomalous transport 1 attributed to short-scale length microturbulence through 2 collective scattering diagnostics is key to the development of 3 nuclear fusion energy. Signals in the subterahertz (THz) range 4 (0.1-0.8 THz) with adequate power are required to map wider 5 wavenumber regions. The progress of a joint international effort 6 devoted to the design and realization of novel backward-wave 7 oscillators at 0.346 THz and above with output power in the 1 W 8 range is reported herein. The novel sources possess desirable 9 characteristics to replace the bulky, high maintenance, optically 10 pumped far-infrared lasers so far utilized in this plasma 11 collective scattering diagnostic. The formidable fabrication 12 challenges are described. The future availability of the THz 13 source here reported will have a significant impact in the field of 14 THz applications both for scientific and industrial applications, 15 to provide the output power at THz so far not available. AQ:1 AQ:2 AQ:3 16 Index Terms-Backward-wave oscillator (BWO), double-17 corrugated waveguide (DCW), double-staggered grating (DSG), 18 plasma diagnostic, terahertz (THz).19

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DIII-D physics research addresses critical challenges for the operation of ITER and the next generation of fusion energy devices. This is done through a focus on innovations to provide solutions for high performance long pulse operation, coupled with fundamental plasma physics understanding and model validation, to drive scenario development by integrating high performance core and boundary plasmas. Substantial increases in off-axis current drive efficiency from an innovative top launch system for EC power, and in pressure broadening for Alfven eigenmode control from a co-/counter-I p steerable off-axis neutral beam, all improve the prospects for optimization of future long pulse/steady state high performance tokamak operation. Fundamental studies into the modes that drive the evolution of the pedestal pressure profile and electron vs ion heat flux validate predictive models of pedestal recovery after ELMs. Understanding the physics mechanisms of ELM control and density pumpout by 3D magnetic perturbation fields leads to confident predictions for ITER and future devices. Validated modeling of high-Z shattered pellet injection for disruption mitigation, runaway electron dissipation, and techniques for disruption prediction and avoidance including machine learning, give confidence in handling disruptivity for future devices. For the non-nuclear phase of ITER, two actuators are identified to lower the L–H threshold power in hydrogen plasmas. With this physics understanding and suite of capabilities, a high poloidal beta optimized-core scenario with an internal transport barrier that projects nearly to Q = 10 in ITER at ∼8 MA was coupled to a detached divertor, and a near super H-mode optimized-pedestal scenario with co-I p beam injection was coupled to a radiative divertor. The hybrid core scenario was achieved directly, without the need for anomalous current diffusion, using off-axis current drive actuators. Also, a controller to assess proximity to stability limits and regulate β N in the ITER baseline scenario, based on plasma response to probing 3D fields, was demonstrated. Finally, innovative tokamak operation using a negative triangularity shape showed many attractive features for future pilot plant operation.

A type of low-pass filter devices for soft x rays is investigated by using a microchannel plate (MCP) of small channels with square cross section. The measured transmission spectra on the Beijing Synchrotron Radiation Facility showed that the MCP has excellent bandpass effects below 1.5 keV by grazing incidence and internal multireflections. Combined with filters, the MCP energy bandwidth can be narrowed to 100 eV. In contrast to bandpass made of planar mirrors, the MCP has a much smaller size and better bandpass effects, and can be easily extended to high energy ranges. For low-resolution spectrometer applications of soft x rays, this method allows the monochromator to be replaced by a simple MCP filter and therefore significantly reduces alignment complexity in experiments.

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