RF electric field penetration and power deposition into nonequilibrium planar-type inductively coupled plasmas

The RF electric field penetration and the power deposition into planar-type inductively coupled plasmas in low-pressure discharges have been studied by means of a self-consistent model which consists of Maxwell equations combined with the kinetic equation of electrons. The Maxwell equations are solved based on the expansion of the Fourier-Bessel series for determining the RF electric field. Numerical results show the influence of a non-Maxwellian electron energy distribution on the RF electric field penetration and the power deposition for different coil currents. Moreover, the two-dimensional spatial profiles of RF electric field and power density are also shown for different numbers of RF coil turns.

Sawtooth Activity in Ohmically Heated Plasma on HT-7 Tokamak

Sawtooth activity on HT-7 tokamak has been investigated experimentally mainly by using soft x-ray diode array and magnetic probes. Their behaviors and occurrences are correlated closely to the discharge conditions: the electron density Ne, the electron temperature Te, the safety factor qa on plasma boundary and wall condition etc. When central line-averaged electron density Ne(0) is over 2.0×1013cm-3 , major sawtooth activity emerges with a period of up to 6.5 ms and a fluctuation amplitude of up to 2-30 % of SXR radiation signal. In some cases such as the safety factor between 4.2-4.7 and Zeff=3.0-6.0, a monster sawtooth activity often emerges without apparent deterioration of plasma confinement and without major disruption. During these events, abundant MHD phenomena are observed including partial sawtooth oscillations. In this paper, the observed sawtooth behaviors and their dependence on the and their dependence density Ne and wall condition in ohmically heated plasma are introduced, the results are discussed and presented.

Plasma MMP-2 and MMP-7 levels are elevated first month after surgery and may promote growth of residual metastases

BACKGROUND MMP-2 also known as gelatinase A and MMP-7(matrilysin)are members of the zinc-dependent family of MMPs(Matrix metalloproteinase).MMP-2 and MMP-7 are remodeling enzymes that digest extracellular matrix;MMP-2 is extensively expressed during development and is upregulated at sites of tissue damage,inflammation,and in stromal cells of metastatic tumors.MMP-7 is expressed in the epithelial cells and in a variety of cancers including colon tumors.Plasma MMP-2 and MMP-7 levels were assessed before and after minimally invasive colorectal resection for cancer pathology.AIM To determine plasma MMP-2 and MMP-7 levels before and after minimally invasive colorectal resection for cancer pathology.METHODS Patients enrolled in a plasma bank for whom plasma was available were eligible.Plasma obtained from preoperative(Preop)and postoperative blood samples was used.Only colorectal cancer(CRC)patients who underwent elective minimally invasive cancer resection with preop,post-operative day(POD)1,3 and at least 1 late postop sample(POD 7-34)were included.Late samples were bundled into 7 d blocks(POD 7-13,14-20,etc.)and treated as single time points.Plasma MMP-2 and MMP-7 levels were determined via enzyme-linked immunosorbent assay in duplicate.RESULTS Total 88 minimally invasive CRC resection CRC patients were studied(right colectomy,37%;sigmoid,24%;and LAR/AR 18%).Cancer stages were:1,31%;2,30%;3,34%;and 4,5%.Mean Preop MMP-2 plasma level(ng/mL)was 179.3±40.9(n=88).Elevated mean levels were noted on POD1(214.3±51.2,n=87,P<0.001),POD3(258.0±63.9,n=80,P<0.001),POD7-13(229.9±62.3,n=65,P<0.001),POD 14-20(234.9±47.5,n=25,P<0.001),POD 21-27(237.0±63.5,n=17,P<0.001,)and POD 28-34(255.4±59.7,n=15,P<0.001).Mean Preop MMP-7 level was 3.9±1.9(n=88).No significant differences were noted on POD 1 or 3,however,significantly elevated levels were noted on POD 7-13(5.7±2.5,n=65,P<0.001),POD 14-20(5.9±2.5,n=25,P<0.001),POD 21-27(6.1±3.6,n=17,P=0.002)and on POD 28-34(6.8±3.3,n=15 P<0.001,)vs preop levels.CONCLUSION MMP-2 levels are elevated for 5 wk and MMP-7 levels elevated for weeks 2-6.The etiology of these changes in unclear,trauma and wound healing likely play a role.These changes may promote residual tumor growth and metastasis.

Monster Sawtooth Activity in Ohmically Heated HT-7 Plasma

Experimental properties of monster sawtooth activities in ohmic HT-7 plasma are presented in this paper. The monster sawtooth activities belong to global fluctuations and are characterized with a series of large core collapses on SXR intensity traces with a long period, a large amplitude fluctuation and a large inversion radius. However, they emerge without apparent deterioration of plasma confinement and without major plasma disruption. During the events, long partial sawtooth collapses and abundant MHD phenomena are also observed.

Feedback Control of Plasma Current and Horizontal Position in HT-7

There is a strong magnetic coupling between poloidal field coils of superconducting tokamak HT-7, especially between ohinic heating and vertical field coils. These coils are connected to individual power supply. The control system for the plasma current and horizontal position control has been designed and showed satisfactory results with the feedback control of multivari- able feedforward-decoupling and var-parameter PID controller to simultaneously modulate power supplies. The design and analysls of the control system is presented.

A Study of Energy Conversion Efficiency Versus Plasma Density by Lower Hybrid Current Drive in HT-7 Tokamak

Ramp-up experiments by means of lower hybrid wave on HT-7 superconducting tokamak have been performed and analyzed. A ramp-up rate of over 300 kA/s is obtained and a conversion efficiency of over 1.0% has been achieved during the ramp-up phase. The study of the dependence of conversion efficiency on plasma density shows that the conversion efficiency is affected by the driven current, which is mainly dominated by the competition of impurity concentration with wave accessibility condition. In addition, the effect of current profile may play an important role in determining the conversion efficiency.

Effect of Shot Peening and Plasma Electrolytic Oxidation on the Intergranular Corrosion Behavior of 7A85 Aluminum Alloy

The effects of shot peening（SP） and plasma electrolytic oxidation（PEO） on the intergranular corrosion behavior of the novel high strength aluminum alloy 7A85（AA 7A85） were investigated by electrochemical polarization and electrochemical impedance tests.The intergranular corrosion mechanism of SP,PEO and PEO combined with sealingtreated AA 7A85 was studied by the metallographic analysis,residual stress testing,X-ray diffractometer analysis and scanning electron microscopy.The results show that AA 7A85-T7452 is very sensitive to intergranular corrosion.SP would significantly improve its intergranular corrosion resistance.This is attributed to the combination action of residual compressive stress and grain refinement.PEO would reduce the largest corrosion depth by 41.6%.Moreover,PEO without sealing did not eliminate the intergranular corrosion due to the existence of the micropores and microcracks in the oxide coating.However,PEO combined with the SiO2sol–gel sealing treatment could effectively protect the AA 7A85-T7452 from intergranular corrosion because of the good corrosion resistance and barrier function of the sealed coating.