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Mitigation of Edge localized mode(ELM) has been achieved with different external actuators such as lower hybrid wave (LHW), mixture supersonic molecular beam injection(SMBI), and laser blow-off(LBO) impurity seeding on HL-2A. During these experiments, the pedestal turbulence enhancement is commonly observed, which is found closely related to ELM mitigation. The turbulence enhancement is caused by the externally driven the velocity shear rate without change of the turbulence correlation length, but correlated to its radial wavenumber spectral shift. A common plausible mechanism for the ELM mitigation with different external source input seems to be involved. A modified theoretical model based on the turbulence radial wavenumber spectral shift is used and successfully interprets the experimental observations. The simulation suggests that a critical growth rate of the most unstable mode, also identified by the experimental results, survives in the competition of the velocity shear rate, enhancing the turbulence intensity. An example of the LHW case is used and good agreements have been found between the experimental results and simulation results.

A hard X-ray pinhole camera system has been recently built at the HL-2A tokamak to measure the evolution of space-time distribution of fast electrons in the energy range of 20 to 200 keV. The camer...

A new broad-energy, high-resolution gamma ray spectrometer (GRS) with Compton suppression function has been developed recently in the HL-2A tokamak to obtain the gamma ray information in the energy range of 0.1–10 MeV. This is the first time to develop an anti-Compton GRS for a magnetic confinement fusion device. The anticoincidence detector consists of a large-volume high purity germanium (HPGe) crystal (Φ63 × 63 mm2) as the primary detector and eight trapezoidal bismuth germinate (BGO) scintillators (trapezoid crystal with 30 mm thickness) as the secondary detector. The anti-coincidence data processing is implemented by a digital-based data acquisition system with fast digitization and software signal processing technology. Using radioisotope gamma ray sources and Monte Carlo N-Particle code, the energy and efficiency of the spectrometer have been calibrated and quantitatively tested. The Compton continuum suppression factor reaches 4.2, and the energy resolution (Full Width at Half Maximum) of the 1.332 MeV full energy peak for 60Co is 2.1 keV. Measurements of gamma ray spectra with Compton suppression using the spectrometer have been successfully performed during HL-2A discharges with different conditions. The performance of the spectrometer and the first experimental results are presented in this paper.

(Ultra) high‐pressure (HP) rocks can be exhumed rapidly by subduction reversal or divergent plate motion. Recent studies show that subduction reversal can in particular occur in a divergent double subduction zone when the slab pull of one slab exceeds that of the other, shorter one, which then experiences a net upward pull. This recent hypothesis, first proposed for Triassic HP‐rocks exposed in the central Qiangtang mélange belt in central Tibet, can explain the exhumation of (ultra) HP rocks through upward slab movement. However, this model lacks the support of kinematic evidence. In this study, based on the recognition of multiple deformational phases, we analyze the kinematics of the HP‐bearing mélange in central Qiangtang. Based on new 40Ar‐39Ar geochronology data and those collected from the literature, we present a temporal framework for the new observations. We recognize a switch in sense of shear between the prograde (D1) and exhumation (D2‐3) paths. The change of shear sense reflects the reversal from downward to upward movement of the oceanic slab below. Early D2 represents the early exhumation stage that caused retrograde metamorphism from eclogite to blueschist facies. No magmatism occurred during this period. Continued exhumation from blueschist facies to greenschist facies resulted in D2‐D3 structures. Voluminous igneous activity occurred during this stage. We suggest that subduction reversal in a divergent double subduction zone can best explain the kinematic evolution and temporal framework above. This exhumation model may provide a new perspective on the exhumation mechanism for other HP rocks around the world., Key Points: Central Qiangtang HP‐bearing mélange formed by short‐lived southward subduction in a divergent double subduction setting. Progressive inversed shearing exhumed HP rocks. Subduction reversal in a divergent double subduction zone can exhume HP rocks through direct slab movement., China Geological Survey (CGS) http://dx.doi.org/10.13039/501100004613

A set of real-time tomographic systems for tokamak plasma hard X-ray (HXR) diagnosis was designed, which is dedicated to real-time investigation of X-ray energy and its density profile that are pro...

A new hard X-ray (HXR) camera system has been planned to be developed for HL-2A tokamak (R0 = 1.65 m, a = 0.4 m, Bt = 2.8 T, and Ip = 0.5 MA), which is dedicated to the tomography of fast electron bremsstrahlung emission in the energy range 10 to 200 keV. The camera system includes two independent HXR cameras, which are both located in the same poloidal plane. Each camera is made up of 30 detection chords and views the whole poloidal cross section of the plasma. The spatial and temporal resolutions of the camera are 2 to 3 cm and 1 to 2 ms, respectively. HXR detection is performed using cadmium telluride (CdTe) semiconductors. Both simulation and experimental results suggest that an Al foil with a 0.3-mm thickness is the best candidate for filtering the low-energy X-ray photons. Powerful inversion techniques are employed to obtain the local HXR profiles as functions of time and photon energy. The HXR camera system planned for HL-2A tokamak is presented in detail.

Hot tensile tests of two dual phase steels with different aluminium contents were performed using a Gleeble 2000 thermal simulator. The effect of Al on hot ductility is discussed. The experiment results indicated that the filmy and meshy ferrite which generated along the austenite grain boundary during the transformation from austenite to ferrite were the main cause of the decrease in hot ductility. The start transformation temperature from austenite to ferrite occurred at a higher temperature with the addition of Al increased from 0⋅03 to 0⋅9%. As a result the ductility trough shifted to a higher temperature range 800–1020°C, compared to 710–920°C for the 0⋅03%Al steel.

In this paper we overview our recent work on ferroelectric and magnetoelectric coupling behaviors of multiferroic doped BiFeO3 (BFO) and piezoelectric-magnetostrictive composites. Using rapid liquid sintering method we prepare single-phase BFO ceramics of excellent ferroelectric property. The BFO thin films on Pt-coated silicon wafers by pulsed laser deposition show large remnant polarization but serious ferroelectric switching fatigue. A series of piezoelectric-magnetostrictive composite structures in bulk and thin film forms are prepared and giant magnetoelectric coupling effect of them is observed. The experimentally measured results are confirmed by numerical modeling based on piezoelectric and magnetostrictive constitution equations.

In this Letter, we use the nanoindentation technique and vary the testing temperature to above and below critical values to study the nanomechanical features of a strong Pb-free piezoelectric Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 (BZT-0.5BCT) thin film across its piezoelectric-optimal morphotropic phase boundary. The mechanisms responsible for the Young's modulus and hardness evolution are then discussed. An X-ray diffraction method that can detect the d(110) variation associated with the change in the inclination angle ψ of the (110) plane was developed to quantify the residual stress in the BZT-0.5BCT films.

Mortality data gathered through registration system were analyzed systematically to predict the trend of cancer mortality. A grey-system model was established to forecast the epidemic trend for cancer mortality of Beijing in 2001. In result, the mortality of cancer in Beijing will increase annually upto 2001. The composition of various malignant tumer will charge notably. Rapid increase will occure in lung cancer. Liver cancer and colon-rectal cancer will aslo increase. Cancers of esophagus and cervix uteri will steadly decline. Stomach cancer begin to decrease. These information on the change of cancer mortality will provide scientific reference for the study of cancer prevention and control in Beijing.

A fast electron bremsstrahlung (FEB) diagnostic technique based on cadmium telluride (CdTe) detector has been developed recently in the HL-2A tokamak for measurements of the temporal evolution of FEB emission in the energy range of 10-200 keV. With a perpendicular viewing into the plasma on the equatorial plane, the hard x-ray spectra with eight different energy channels are measured. The discrimination of the spectra is implemented by an accurate spectrometry. The system also makes use of fast digitization and software signal processing technology. An ambient environment of neutrons, gammas, and magnetic disturbance requires careful shielding. During electron cyclotron resonance heating, the generation of fast electrons and the oscillations of electron fishbone (e-fishbone) have been found. Using the FEB measurement system, it has been experimentally identified that the mode strongly correlates with the electron cyclotron resonance heating produced fast electrons with 30-70 keV.

In the present paper, it is reported that a large production of runaway electrons has been observed during the flattop phase of electron cyclotron resonance heating (ECRH) discharges and in the presence of supersonic molecular beam injection (SMBI) in the HuanLiuqi-2A (commonly referred to as HL-2A) [Q. W. Yang, Nucl. Fusion 47, S635 (2007)] tokamak. For the set of discharges carried out in the present experiment, the ranges of ECRH power and plasma electron density are 0.8–1.0 MW and (3.0–4.0)×1019 m−3, respectively. A large number of superthermal electrons are produced through the avalanche effect [A. Lazaros, Phys. Plasmas 8, 1263 (2001)] during ECRH. The loop voltage increase due to SMBI gives rise to a decline in the critical runaway energy, which leads to that many superthermal electrons could be converted into runaway region. Therefore, this phenomenon may come from the synergetic effects of ECRH and SMBI. That is, the superthermal electrons created by ECRH are accelerated into runaway regime via t...

A new soft x-ray pulse height analysis (PHA) array including nine independent subsystems, on basis of a nonconventional software multichannel analysis system and a silicon drift detector (SDD) linear array consisting of nine high performance SDD detectors, has been developed in the HL-2A tokamak. The use of SDD has greatly improved the measurement accuracy and the spatiotemporal resolutions of the soft x-ray PHA system. Since the ratio of peak to background counts obtained from the SDD PHA system is very high, p/bor = 3000, the soft x-ray spectra measured by the SDD PHA system can approximatively be regarded as electron velocity distribution. The electron velocity distribution can be well derived in the pure ohmic and auxiliary heating discharges. The performance of the new soft x-ray PHA array and the first experimental results with some discussions are presented.

(001)-oriented BiFeO3 and SrRuO3 films were deposited on SrTiO3 and DyScO3 substrates to study oxygen-vacancy density as a function of cooling oxygen pressure. During cooling of as-grown samples at ≤0.01 Torr oxygen pressure, SrRuO3 films decompose, BiFeO3 films can accommodate a significant fraction of oxygen vacancies, SrTiO3 substrates acts as a sink for vacancies, and DyScO3 substrates remaining largely unaffected by oxygen vacancies. These phenomena can be explained according to the electronegativity of the different B-site atoms, because changes in B-site ion valence play a key role in maintaining charge equilibrium during oxygen vacancy production in many ABO3-type oxides.

Single-phase Bi0.875Sm0.125FeO3 ceramics were prepared, and their crystal structure and multiferroic properties were studied. The triclinic structure with P1 space group was confirmed in the ceramics by refining the x-ray diffraction data. Large piezoelectric d33 coefficient of 29pC∕N, together with high remnant polarization of 15.09μC∕cm2, was measured at room temperature, suggesting the existence of long-range ferroelectric order on a macroscopic scale. The observed small remnant magnetization of 0.071emu∕g at room temperature as a result of the collapse of the space-modulated spin structure indicated the presence of long-range canted antiferromagnetic order on a macroscopic scale. The coexistence of the long-range ferroelectric and canted antiferromagnetic orders allowed the magnetoelectric effect below the antiferromagnetic Neel temperature of 265°C near which magnetoelectric coupling was obvious.

La-doped BiFeO3 thin films with Fe2+ ions have been prepared on Pt/TiO2/SiO2/Si substrates by pulsed laser deposition in order to enhance the ferroelectric and magnetic properties. The targets for the film deposition were synthesized using a rapid liquid phase sintering technique to ensure the low leakage. The dielectric properties at room temperature and above were investigated. It was observed that the La doping greatly enhances the ferroelectric polarization at room temperature by modifying the film structure from rhombohedral to monoclinic. The saturation magnetization was enhanced about two times due to the Fe2+ ions in the thin films. (C) 2006 American Institute of Physics.