7.3 Standard Facility Diagnostics

NIF DLI has a standard set of laser diagnostics built into the system. As noted, NIF DLI operations are integrated into NIF operations. The laser beams transport, conversion from 1ω to 2ω wavelength, and beam alignment are integrated into the CV2 vacuum chamber. Each beam passes from the CV2 vacuum chamber into the test area through a vacuum window. A small percentage of the incident laser light is reflected from each of the two vacuum windows and directed to two laser diagnostics systems mounted in the CV2 vacuum chamber as shown in Figure 12. These diagnostics measure the energy of each beam at the wavelength impinging on the sample plane to within 1% rms precision and 3% rms absolute. The system also measures the power impinging upon the target plane with at least 2.5 GHz bandwidth and 7-bit dynamic range. Finally, the system measures the beam uniformity with near field impinging upon the target plane with at least 250 um resolution and 11-bit dynamic range. Note that the vacuum windows have spatially non-uniform reflectivity profiles that impact the uniformity of the images recorded by the two near field cameras. The known reflectivity profiles can be deconvolved from the measured near-field images to recover accurate laser fluence profiles for each beam. The DLI laser scientist and DLI experimental lead will work with users to provide reflectivity-corrected images, so they have an accurate representation of the on-target laser fluence for their shot(s). Note that deconvolved near-field images have demonstrated r.ms. values that satisfy the uniformity requirement described in Section 5.1.

Standard laser diagnostics are contained within DLI laser transport volume using reflected light from the two vacuum windows.
Figure 12. Standard laser diagnostics are contained within DLI laser transport volume using reflected light from the two vacuum windows.

Provisions are provided for two cameras that can view the target interaction plane. Figure 13 shows a view of the target vessel with the location of the two target viewing camera ports. The target viewing camera can be placed in either of the two ports on the sides of the target vessel and the data can be collected locally or through the NIF shot archive system.

Test Area showing location for two target viewing camera ports and the spare flanges that can be used for custom feedthrough plates.
Figure 13. Test Area showing location for two target viewing camera ports and the spare flanges that can be used for custom feedthrough plates.

One camera will be part of the standard NIF system diagnostics. Users will need to provide an additional camera and data acquisition if they need two on a shot. Details of the camera mount are shown in Figure 14. The camera sits inside a semi-cylindrical enclosure that is 60 mm in the wide horizontal dimension, 50 mm in the narrow horizontal dimension, and 106 mm tall. The enclosure attaches to the base with 4 M8X1.25X30 bolts. A user custom enclosure would need to have the same bottom interface for the bolts and top interface for the cabling. It would also need to include a camera mount. The NIF supplied target viewing camera is a BASLER ACA2040-25GM and has the specification outlined in Table 1 below.

Details of target viewing camera with in- situ debris shield and turning mirror assembly.
Figure 14. Details of target viewing camera with in- situ debris shield and turning mirror assembly.
Target Viewing System Camera Specifications