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Impurities degrade tokamak plasma confinement by causing energy loss, diluting fuel concentration, and even terminating discharge in some extreme cases. Previously, the suppression effects of impurity accumulation due to on-axis electron cyclotron resonance heating (ECRH) have been studied on Experimental and Advanced Superconducting Tokamak (EAST) using extreme ultraviolet (EUV) spectroscopy. However, it is difficult to quantify changes in the tungsten (W) impurity profile since W-line emission in the EUV range cannot be easily resolved. X-ray crystal spectroscopy (XCS) is widely used to measure the ion temperature and rotation velocity of plasmas by using line emission in the soft X-ray range. In addition, the XCS can also be used to study the behavior of impurities. An in situ absolute intensity calibration of tangential XCS was conducted by analyzing calculations and measurements of bremsstrahlung radiation. After obtaining the calibration coefficient, the W44+-ion-density profiles were evaluated using Abel inversion operations and the spectral line of W XLV (W44+, 3.9095 Å). Thus, a direct observation of the W44+-impurity concentration suppressed by ECRH was accomplished. Such W44+-density profiles can be used in the future to analyze W transport in combination with impurity transport codes.

Carbon doped silicon oxide SiO(C, H) low k thin films (k∼2.9) deposited by the plasma enhanced chemical vapor deposition technique from trimethylsilane (3MS) and oxygen (O2) have been studied. Two types of chemical vapor deposition process recipes, namely CVD1 and CVD2 were applied for film deposition. CVD1 is an initial recipe that resulted in films with a uniform deposition rate irrespective of film thickness and a low dielectric constant of about 2.9. However, it suffers from extraordinarily high post particle counts. CVD2 is a modified recipe adopted to address this issue. The main difference between the two recipes is that a pump down step immediately before the film deposition has been omitted in recipe CVD2, and this has successfully reduced the particle counts to a satisfactory level. However when using recipe CVD2, the deposition rate is nonuniform and the dielectric constant is slightly above 3.0, attributed to the residual oxygen in the process step prior to film deposition. In this study we in...

The CO2 laser, is for the first time, used as a light source to generate acoustic waves (P, R, and S waves) in an Al sample. The relationship between the acoustic wave amplitude and the incident laser energy is investigated. The spectra of the resonance P and S waves in the Al sample for the frequency range between 1 and 10 MHz are presented. The value of the amplitude ratio between the generated P and S waves is 2.0–3.0.

High‐power CO2 laser radiation has been used to study the optical breakdown plasma on various solid targets (NaCl, KBr, ZnSe, and Ge). The breakdown threshold for irreversible changes of the optical characteristics was determined as well as the evaporation threshold of Na atoms from NaCl samples by CO2 laser irradiation; the latter value was about 2.8×107 W/cm2. The time profiles of the ejected Na atoms and the propagation of the atoms in front of the sample was measured with the laser fluorescence method.