The apparatus comprises a first fluid line for conducting an intermittently flowing first fluid and a second fluid line for conducting an intermittently flowing second fluid, the two fluid lines being connected at a junction to a third fluid line, which forwards the two, particularly mixed, fluids. Extremely high levels of substitutional incorporation may be obtained, including crystalline silicon films that contain at least about 3\xd71020 atoms cm\u22123 of an electrically active dopant. min\u22121 according to: KRUEGKGmax\u2265\u0394\u2062\u2003\u2062TUEGKGmax100\xb7KGmax,wherein \u0394T=TKGmax\u2212TUEG, and KGmax=maximum crystal growth rate in \u03bcm min\u22121. Interference between the female connector F and the long male terminal fittings 12 does not need to be taken into consideration in determining the protruding length of the hood 10.