J.L. Chen

Upgrades of imaging x-ray crystal spectrometers for high-resolution and high-temperature plasma diagnostics on EAST

Upgrade of the imaging X-ray crystal spectrometers continues in order to fulfill the high-performance diagnostics requirements on EAST. For the tangential spectrometer, a new large pixelated two-dimensional detector was deployed on tokamaks for time-resolved X-ray imaging. This vacuum-compatible detector has an area of 83.8 × 325.3 mm(2), a framing rate over 150 Hz, and water-cooling capability for long-pulse discharges. To effectively extend the temperature limit, a double-crystal assembly was designed to replace the previous single crystals for He-like argon line measurement. The tangential spectrometer employed two crystal slices attached to a common substrate and part of He- and H-like Ar spectra could be recorded on the same detector when crystals were chosen to have similar Bragg angles. This setup cannot only extend the measurable Te up to 10 keV in the core region, but also extend the spatial coverage since He-like argon ions will be present in the outer plasma region. Similarly, crystal slices for He-like iron and argon spectra were adopted on the poloidal spectrometer. Wavelength calibration for absolute rotation velocity measurement will be studied using cadmium characteristic L-shell X-ray lines excited by plasma radiation. A Cd foil is placed before the crystal and can be inserted and retracted for in situ wavelength calibration. The Geant4 code was used to estimate X-ray fluorescence yield and optimize the thickness of the foil.

Manufacturing of 50 kA superconducting transformer for ITER correction coil conductor test

To meet the specifications of International Thermonuclear Experimental Reactor correction coil (CC) conductor, a 50 kA superconducting transformer has been designed and manufactured to provide the short sample of the CC conductor the current. The transformer consists of two concentric layer-wound superconducting solenoids with the primary inside the secondary coil. In order to test the transformer, the two legs of the secondary coil were directly connected by superconducting cables. A 500 W/4.5 K refrigerator was used to provide the supercritical helium. The maximum current of 56.3 kA in the secondary coil loop was obtained.

Measurement of helium-like and hydrogen-like argon spectra using double-crystal X-ray spectrometers on EAST

A two-crystal assembly was deployed on the tangential X-ray crystal spectrometer to measure both helium-like and hydrogen-like spectra on EAST. High-quality helium-like and hydrogen-like spectra were observed simultaneously for the first time on one detector for a wide range of plasma parameters. Profiles of line-integrated core ion temperatures inferred from two spectra were consistent. Since tungsten was adopted as the upper divertor material, one tungsten line (W XLIV at 4.017 Å) on the short-wavelength side of the Lyman-α line (Lα1) was identified for typical USN discharges, which was diffracted by a He-like crystal (2d = 4.913 Å). Another possible Fe XXV line (1.85 Å) was observed to be located on the long-wavelength side of resonance line (w), which was diffracted from a H-like crystal (2d = 4.5622 Å) on the second order. Be-like argon lines were also observable that fill the detector space between the He-like and H-like spectra.

Manufacture and Measurement of a Fifty Kilo-Ampere Superconducting Transformer for the ASIPP Conductor Test Facility

To meet the performance test of the International Thermonuclear Experimental Reactor correction coil conductors, a 50-kA superconducting transformer has been manufactured, which allows rating of test samples under different operating conditions at the Institute of Plasma Physics of the Chinese Academy of Sciences (ASIPP). This transformer system is made up of two concentric layer-wound superconducting solenoids with the primary inside the secondary. The 50-kA secondary winding consists of 4-turn rectangular cable-in-conduit conductor type. This paper describes the design and manufacture techniques of the 50-kA transformer, including a secondary conductor. The secondary terminal design and manufacture are also discussed. Finally, the first test results of the 50-kA transformer are presented.

Design and Manufacture of the AC Superconducting Magnet for the Conductor Test Facility at ASIPP

To meet the ac loss measurement of the International Thermonuclear Experimental Reactor correction-coil conductors, an ac superconducting magnet has been designed and manufactured at the Institute of Plasma Physics, Chinese Academy of Sciences (ASIPP), which can run at a frequency of 5 Hz and an amplitude field of 0.2 T. This ac magnet is made up of two layers of coils with NbTi superconducting strands and has good thermal conductive capacity. This paper describes the structural design and thermal analysis of the ac magnet with two different NbTi strands. The structural design of the compensation coil for the quench detection system is also discussed. Finally, the manufacture technique of the ac magnet is also presented.

Plasma facing conponents of EAST

EAST plasma facing components (PFCs) have the function of protecting the vacuum vessel, heating systems and diagnostic components from the plasma particles and heat loads, and also additional to this particles and heat loads handling. They are installed in the vacuum vessel together with in-vessel coils, cryopump and diagnostic components. The design, fabrication and assembly have been finished. The PFCs are designed up-down symmetry to accommodate with both double null and single null plasma configuration. All PFCs use graphite tile for plasma facing surfaces affixed to copper alloy heat sink. A special deep hole drilling technology was developed to drill cooling channels directly on heat sink for high efficient heat removal. All Heat sink are installed onto the base alignment rails through stainless steel supports. As the benchmark of assembly for PFCs, the base rails are installed and measured precise based on a new alignment method integrating the optical instruments and a mechanical template. And so is a mechanical check template for checking the surface of first wall. As indicated, all the first wall components were fabricated and assembled successfully and meet the design requirement for the plasma operation.

Upgrade of X-ray crystal spectrometer for high temperature measurement using neon-like xenon lines on EAST

A two-crystal X-ray spectrometer system has been implemented in the EAST tokamak to simultaneously diagnose high- and low-temperature plasmas using He- and H-like argon spectra. But for future fusion devices like ITER and Chinese Fusion Engineering Test Reactor (CFETR), argon ions become fully stripped in the core and the intensity of the H-like lines will be significantly at high temperatures (Te > 5 keV). With increasing auxiliary heating power on EAST, the core plasma temperature could also reach 5 keV and higher. In such conditions, the use of a xenon puff becomes an appropriate choice for both ion-temperature and flow-velocity measurements. A new two-crystal system using a quartz 110 crystal (2d = 4.913 Å) to view He-like argon lines and a quartz 011 crystal (2d = 6.686 Å) to view Ne-like xenon spectra has been deployed on a poloidal X-ray crystal spectrometer. While the He-like argon spectra will be used to measure the plasma temperature in the edge plasma region, the Ne-like xenon spectra will be used for measurement in the hot core. The new crystal arrangement allows a wide temperature measurement ranging from 0.5 to 10 keV or even higher, being the first tests for burning plasmas like ITER and CFETR. The preliminary result of lab-tests, Ne-like xenon lines measurement will be presented.