Schematic of the backscatter calibration system. The pulsed laser is injected through the TIM, and the beam is deflected from the target chamber center onto the backscatter diagnostics.
(Left) Shot locations on the NBI plate from a calibration run. The insert shows a typical spot from the calibration laser. (Right) Sensitivity map for the long wavelength channel.
Variation of NBI sensitivity (in the short wavelength channel) with time since last NBI plate change. The sensitivity drops by over 90% over a few months. The lower sensitivity of beam 30 is due to the oblique viewing angle of the NBI cameras.
NBI data in the short wavelength channel, showing strong backscatter from stimulated Brillouin scattering. The sketch shows the alignment of the Hohlraum using one beam as on-axis probe beam. The energies measured by FABS and on the NBI plates are denoted in the image.
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