The Full Aperture Backscatter Station Measurement System on the National Ignition Facility

A Full Aperture Backscatter Station (FABS) target diagnostic has been activated on the first four beams of the National Ignition Facility (NIF). Backscattered light from the target propagates back down the beam path into the FABS diagnostic system. FABS measures both stimulated Brillouin scattering (SBS) and stimulated Raman scattering (SRS) with a suite of measurement instruments. Digital cameras and spectrometers record spectrally resolved energy for both P and S polarized light. Streaked spectrometers measure the spectral and temporal behavior of the backscattered light. Calorimeters and fast photodetectors measure the integrated energy and temporal behavior of the light, respectively. This paper provides an overview of the FABS measurements system and detailed descriptions of the diagnostic instruments and the optical path.