Z(eff) spatial profiles from Bremsstrahlung emission in the near infrared spectral region

Measurements of plasma radiation in the infrared (IR) BREM_IR range (lambda =978 nm, Delta lambda =38 nm), at 16 horizontal lines of sight intersecting the central vertical chord of the [Frascati Tokamak Upgrade (FTU) R=0.935 m, a=0.3 m, B=4-8 T], from z=-0.22 m below, to z =0.08 m above the equatori al plane, are performed using the detection system of the Thomson scatterin g apparatus [F. Orsitto et al., Appl. Opt. 34, 2712 (1995)] (TS). The measu red BREM_IR intensity is equal I(z)=[Z(eff)Gn(e)(2)/T-e(1/2)] where [] mean s line average. For determining the Z(eff), the Gaunt factor (G) is needed, and the Born-Elwert formula is used. The Z(eff) spatial profiles are deter mined using the plasma temperature (T-e) and density (n(e)) measured by the TS, DCN interferometer, and Abel inverted intensity profiles. Z(eff)(r) ve rsus time behavior in FTU discharges is presented for krypton injection exp eriments aimed to investigate the particle confinement behavior during stro ng injection of impurities. (C) 1999 American Institute of Physics. [S0034- 6748(99)74001-3].