Lawrence Livermore National Laboratory



For NIF to reach the goal of ignition, it needs to produce highly shaped pulses that are precisely controlled. NIF's precision diagnostic system (PDS) examines all the properties of a NIF beam to verify performance. It has the same final optics configuration as installed in the NIF target chamber but with the hardware for only one beam in order to measure beam characteristics.

These false color images of NIF 2ω (green, left) and 3ω (blue, right) laser beams obtained in the precision diagnostic system show excellent beam uniformity that exceeds requirements. NIF laser beams have also demonstrated outstanding energy balance from beam to beam.

The PDS contains an extensive suite of diagnostics for characterizing the selected beamline. Mirrors can be positioned to redirect the beam to the PDS prior to its entry into the target bay. The incoming beam of one-omega (1ω) infrared light, with a wavelength of 1,053 nanometers (nm), is converted to 351-nm ultraviolet light (3ω) and brought to focus in the middle of the PDS prime focus vessel. Downstream, a 1-meter aperture telescope housed in the vacuum environment of the target diagnostic chamber is used to image the 3ω focal plane onto several diagnostics.

The PDS is used extensively to test the frequency conversion performance of the NIF final optics assembly (FOA). Accurate measurements of the FOA input and output beam energies, made with as many as six calorimeters, are essential to ensuring proper conversion.

Operation of the PDS is controlled by NIF's integrated computer control system. The PDS operator manages all PDS diagnostics remotely from the control room using a graphical user interface, which contains a layout of PDS with each diagnostic represented by individual icons. Clicking on an icon brings up the control panels associated with that diagnostic.

During shot time, initial setup, status checking, shot capture, and postshot data archiving, the diagnostics are coordinated automatically. Immediately after the shot, data analysis from PDS diagnostics is performed automatically and presented in a shot report. This rapid analysis contributes to NIF's capability to operate with short intervals between shots.