The pulse shape and timing are common for all four beams within a single quad. Each quad may be independently configured for timing and pulse shape. NIF has the capability to produce a wide variety of precision pulse shapes. The flexibility of pulse shaping is limited between the two quads within a single bundle due to amplifier configuration and residual gain issues.
In order to request a pulse shape, the user enters the desired pulse shape and energy at the target through the shot setup. This request is then transformed to a Master Oscillator Room (MOR) pulse shape request through the LPOM setup calculations, which factor in pulse shape distortions caused by main laser gain saturation and frequency conversion. The requested MOR pulse shape is then created using an arbitrary waveform generator (AWG). The maximum pulse width for any quad is currently limited to 30 ns due to the current MOR pulse-shaping hardware and the regenerative amplifier round-trip time. Figure 4-11 shows some recent examples of the types of pulses that can be generated on NIF. In addition to shaped pulses, NIF also can generate 88-ps full width at half-maximum (FWHM) Gaussian pulses (called “impulses”) used for point x-ray sources.
