Slit mask integral field units for the Southern African Large Telescope

Two fiber integral field units (IFU) are being built in the SAAO fiber-lab for the Robert Stobie Spectrograph's visible arm and the future red arm. The 200 (400) micron fibre IFU has 309 x 0.9 (178 x 1.8) arcsec diameter spatial elements covering an elongated hexagonal footprint of 414 (924) arcsec^2. Each IFU sits in its own slit-mask cassette and is referred to as a slit-mask IFU (SMI). These are inserted in the same fashion as the existing long-slit cassettes at the SALT focal plane. Prismatic fold mirrors direct the focal plane into the fiber IFU and then back into the RSS collimator after the fibres are routed 180 deg within the cassette and formatted into a pseudo-slit. In this paper we describe the design, fabrication, assembly and characterization of Slit Mask IFU.