Filter-fluorescer diagnostic system for the National Ignition Facility

Abstract

An early filter-fluorescer diagnostic system is being fielded at the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory (LLNL) to measure the amount of hard x rays ͑20Ͻ h Ͻ 150 keV͒ generated in laser fusion experiments. From these measurements we hope to quantify the number of hot electrons produced in laser fusion experiments. The measurement of hot electron production is important for ignition experiments because these electrons can preheat the fuel capsule. Hot electrons can also be employed in experimentation by preheating hydrodynamic packages or by driving plasmas out of equilibrium. The experimental apparatus, data collection, analysis and calibration issues are discussed. Expected data signal levels are predicted and discussed.

Three-wavelength scheme to optimize hohlraum coupling on the National Ignition Facility

“…The electron distribution is calculated from the measurement of the Bremsstrahlung hard x-ray emitted through the hohlraum wall by energetics electrons with the FFLEX diagnostic [18][19][20]. The 10 FFLEX channels are absolutely calibrated, and their spectral responses include the detailed hohlraum composition (gold wall and aluminum case).…”

Hard X-ray and hot electron environment in vacuum hohlraums at NIF

“…The data presented in this paper were collected from two diagnostics during this NIF early light (NEL) experimental campaign namely; a gated flexible x-ray imager (FXI) [4] configured as a Hard X-ray Imager (HXRI) and a Filter Fluorescer Experiment (FFLEX) diagnostic [5]. The HXRI recorded time resolved hohlraum emission for > 9 keV photons through the thin walls of the hohlraums as well as the emission of > 6 keV photons from outside the hohlraums that passed through the Al filter.…”

Hard x-ray transmission curved crystal spectrometers (10–100 keV) for laser fusion experiments at the ShenGuang-III laser facility

“…The α-quartz crystals that we used were symmetrically cut into thin slices with the (11)(12)(13)(14)(15)(16)(17)(18)(19)(20) surface plane and the (10-11) edge plane. Since thinly sliced quartz is elastic at room temperature, it can be bent without additional heating.…”

“…Solid-state detectors of single-photon counting CCDs (3-30 keV) [11] , dispersive x-ray detectors of transmission curved crystal spectrometers (10-120 keV) [12] , and nondispersive x-ray detectors with filters, such as Ross pairs spectrometers (18-90 keV) [13,14] , filter stack spectrometers (12-700 keV) [15,16] and filter-fluorescer spectrometers (20-220 keV) [17,18] are the conventional approaches for hard x-ray spectra diagnostics. The dispersive x-ray detectors of transmission curved crystal spectrometers are superior, especially in the 10-120 keV range which is more applicable to laser fusion experiments, due to their high spectral resolution, broad energy coverage, and robustness in harsh environments.…”