The National Ignition Facility (NIF) is a 192 laser beam facility designed to support the Inertial Confinement Fusion program based on laser-target interactions. The Optical Thomson Scattering (OTS) diagnostic has the potential to transform the community’s understanding of NIF hohlraum physics by providing first principle, local, time-resolved measurements of under-dense plasma conditions. A deep-UV probe beam is needed to overcome the large background of self-Thomson scattering produced by the 351nm (3ω) NIF drive beams. A two-phase approach to OTS on NIF will mitigate the risk presented by background levels. In Phase I, the diagnostic will assess background levels around a potential deep-UV probe wavelength considered for 5ω Thomson scattering measurements to be conducted in Phase II. The Phase I design of the diagnostic includes an unobscured collection telescope, dual crossed Czerny-Turner spectrometers, and the shared use of one streak camera located inside of an airbox. The Phase II design will include a 5ω probe laser. We will describe the engineering design and concept of operations of the Phase I NIF OTS diagnostic, with a focus on optomechanical disciplines.
X-ray streak cameras are used at the National Ignition Facility for time-resolved measurements of inertial
confinement fusion metrics such as capsule implosion velocity, self-emission burn width, and x-ray bang time (time
of brightest x-ray emission). Recently a design effort was undertaken to improve the performance and operation of
the streak camera photocathode and related assemblies. The performance improvements include a new optical
design for the input of UV timing fiducial pulses that increases collection efficiency of electrons off the
photocathode, repeatability and precision of the photocathode pack assembly, and increase the input field of view
for upcoming experiments. The operational improvements will provide the ability to replace photocathode packs
between experiments in the field without removing the diagnostic from the Diagnostic Instrument Manipulator
(DIM). The new design and preliminary results are presented.
A neutron hardened x-ray streak camera has been used to report x-ray burn duration and time of peak emission from
imploding ICF capsules at the National Ignition Facility with <30 ps. Recent characterization of the instrument using
a NIST traceable High Energy X-ray reference source (HEX, National Security Technologies) will enable absolute
capsule self-emission x-ray yield measurements (J/sr/keV). This manuscript describes the characterization procedure
used and preliminary results of the x-ray sensitivity using three different thicknesses of the CsI photocathode.