title: The motional Stark effect polarimeter in the HL-2A tokamak.
abstract: A 7-channel motional Stark effect polarimeter based on four polarizers and a spectrometer has been developed in the HL-2A tokamak, which is the first time successful utilizing this kind of polarimeter on a tokamak. The accuracy of the angle can reach ±0.25° in the calibration experiments. Pilot experiments of measuring the magnetic pitch angle have been successfully carried out in the weak motional Stark effect plasma discharge with toroidal magnetic field of ~1.3 T and beam energy of ~25 keV/amu. The pitch angles of magnetic field are obtained for 7 spatial points covering 24 cm along major radius with time resolution of 40 ms; the profiles of safety factor are obtained by combining with the Equilibrium and Reconstruction Fitting Code. The core value of safety factor (q) is less than 1 during the sawtooth oscillation and the position of q = 1 surface is well consistent with the results measured by soft X-ray array.
authors.affiliation: Southwestern Institute of Physics, Chengdu, Sichuan 610041, China.
authors.forename: D L
authors.initials: DL
authors.lastname: Yu
authors.affiliation: Southwestern Institute of Physics, Chengdu, Sichuan 610041, China.
authors.forename: Y L
authors.initials: YL
authors.lastname: Wei
authors.affiliation: Southwestern Institute of Physics, Chengdu, Sichuan 610041, China.
authors.forename: F
authors.initials: F
authors.lastname: Xia
authors.affiliation: Southwestern Institute of Physics, Chengdu, Sichuan 610041, China.
authors.forename: J Y
authors.initials: JY
authors.lastname: Cao
authors.affiliation: Southwestern Institute of Physics, Chengdu, Sichuan 610041, China.
authors.forename: C Y
authors.initials: CY
authors.lastname: Chen
authors.affiliation: Southwestern Institute of Physics, Chengdu, Sichuan 610041, China.
authors.forename: L
authors.initials: L
authors.lastname: Liu
authors.affiliation: Southwestern Institute of Physics, Chengdu, Sichuan 610041, China.
authors.forename: W J
authors.initials: WJ
authors.lastname: Chen
authors.affiliation: Southwestern Institute of Physics, Chengdu, Sichuan 610041, China.
authors.forename: X Q
authors.initials: XQ
authors.lastname: Ji
authors.affiliation: Southwestern Institute of Physics, Chengdu, Sichuan 610041, China.
authors.forename: Y
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Southwestern Institute of Physics, Chengdu, Sichuan 610041, China.
authors.forename: L W
authors.initials: LW
authors.lastname: Yan
authors.affiliation: Southwestern Institute of Physics, Chengdu, Sichuan 610041, China.
authors.forename: Q W
authors.initials: QW
authors.lastname: Yang
authors.affiliation: Southwestern Institute of Physics, Chengdu, Sichuan 610041, China.
authors.forename: X R
authors.initials: XR
authors.lastname: Duan