| Abstract: | Sheath potential coefficient α is a key parameter,which is used to estimate plasma potential(Vp)for edge plasma physics study.Recently,a series of experiments has been carried out under hydrogen plasmas in the J-TEXT tokamak with swept probe,which is employed for current-voltage(Ⅰ-Ⅴ)characteristic measurement.Electron temperature is evaluated from Ⅰ-Ⅴ curve by three-parameter fitting method,and the electron energy probability function shows that electron distribution is Maxwellian both outside and inside of last closed flux surface(LCFS).Plasma potential is obtained by crossing point between Ⅰ-Ⅴ exponential fitting curve and electron saturation current extrapolating line,which is in good agreement with first derivative probe technique.The α coefficient profile in the vicinity of the LCFS is obtained,which is in the range of 2.1-3,and decreases from outside to inside of LCFS. |
