A dual-channel, fiber-optic-coupled direct reader attachment for a spectrometer is described which uses bundles of 200-μm diameter quartz optical fibers as spectrometer exit slits and as a means of isolating the photomultiplier tubes from the region of the radiation source. The bandpass of the fiber exit slits is reduced by the coating of the fiber ends with an opaque Al film, leaving a 75-μm-wide clear region. The ends of the fibers are located in the focal plane of the spectrometer, with a fixed bundle positioned to correspond to the wavelength readout of the spectrometer and the other bundle adjustable on the focal plane to provide a simultaneous background correction at an adjacent wavelength. A dual-channel time-gated integrator based on an Evans 4130 integrator board is used with the fiber-optic-coupled photoelectric detector to obtain background-corrected, time-gated radiation measurements on transient, nonrepetitive radiation sources. Preparation techniques and optical properties of the quartz optical fiber bundles are discussed. Amplifier and timing circuits for the gated integrator are presented. Electrical and analytical performance data for the system are presented with the use of the high-intensity radiation pulse from an electrically vaporized thin-film plasma source.
J. M. Swan and R. D. Sacks, "A Dual-Channel, Fiber-Optic-Coupled Direct Reader with Gated Integration for Transient Radiation Measurements," Appl. Spectrosc. 39, 704-710 (1985)