The electron and ion temperatures of the imploded core plasma are two of the most important metrics of inertial confinement fusion experiments. We have developed a technique for inferring electron temperatures from the contrast of x-ray images observed through a group of x-ray filters. Generally, the plasma electron temperature exhibits spatial and temporal variations, so time-averaged and time-resolved measurements are expected to yield somewhat different results. By analyzing the intensity of images observed with both a time-integrated detector (imaging plates) and a time-resolved detector (gated micro-channel plate), we found the electron temperature observed from x-ray images to be systematically higher than the ion temperature inferred from fusion neutron spectroscopy.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2012

Compact proton spectrometers for measurements of shock

The compact Wedge Range Filter (WRF) proton spectrometer was developed for OMEGA and transferred to the National Ignition Facility (NIF) as a National Ignition Campaign (NIC) diagnostic. The WRF measures the spectrum of protons from D-{sup 3}He reactions in tuning-campaign implosions containing D and {sup 3}He gas; in this work we report on the first proton spectroscopy measurement on the NIF using WRFs. The energy downshift of the 14.7-MeV proton is directly related to the total {rho}R through the plasma stopping power. Additionally, the shock proton yield is measured, which is a metric of the final merged shock strength.

42 ENGINEERING↗

DOE OSTI2011

Shock timing on the National Ignition Facility: First Experiments

An experimental campaign to tune the initial shock compression sequence of capsule implosions on the National Ignition Facility (NIF) was initiated in late 2010. The experiments use a NIF ignition-scale hohlraum and capsule that employs a reentrant cone to provide optical access to the shocks as they propagate in the liquid deuterium-filled capsule interior. The strength and timing of the shock sequence is diagnosed with velocity interferometry that provides target performance data used to set the pulse shape for ignition capsule implosions that follow. From the start, these measurements yielded significant new information on target performance, leading to improvements in the target design. We describe the results and interpretation of the initial tuning experiments.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2011

NIF CAPSULE PERFORMANCE MODELING

Abstract not provided

42 ENGINEERING↗

DOE OSTI2011

Amplification of light in a plasma by stimulated ion acoustic waves driven by multiple crossing pump beams

Experiments demonstrate the amplification of 351 nm laser light in a hot dense plasma similar to those in inertial confinement fusion ignition experiments. A seed beam interacts with one or two counter-propagating pump beams, each with an intensity of 1.2x10{sup 15} W/cm{sup 2} at 351 nm, crossing the seed at 24.8 deg. at the position where the flow is Mach 1, allowing resonant stimulation of ion acoustic waves. Results show that the energy and power transferred to the seed are increased with two pumps beyond the level that occurs with a single pump, demonstrating that, under conditions similar to ignition experiments where each beam has a low gain exponent, the total scatter produced by the multiple beams can be significantly larger than that of the individual beams. It is further demonstrated that the amplification is greatly reduced when the pump polarization is orthogonal to the seed, as expected from models of stimulated scatter.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗