Noel R. Sewall

Full-aperture backscatter measurements on the National Ignition Facility

The National Ignition Facility’s full-aperture backscatter station (FABS) is described. The FABS uses five independent diagnostics on each of the four laser beams in the initial National Ignition Facility quad to measure the energy, power, spectrum, and near-field amplitude modulations of the stimulated Brillouin and stimulated Raman backscattered light. In initial tests CO2 and C5H12 gas-filled targets were used to create various laser–plasma interaction conditions which have shown the capability of producing ignition size laser plasmas with reflectivites on the order of 10%. Results are presented for tests in which 16 kJ on target produced between 0.3 and 2.5 kJ of backscattered light.

National Ignition Facility core x-ray streak camera

The National Ignition Facility (NIF) core x-ray streak camera will be used for laser performance verification experiments as well as a wide range of physics experiments in the areas of high-energy-density science, inertial confinement fusion, and basic science. The x-ray streak camera system is being designed to record time-dependent x-ray emission from NIF targets using an interchangeable family of snouts for measurements such as one-dimensional (1D) spatial imaging or spectroscopy. the NIF core x-ray streak camera will consist of an x-ray-sensitive photocathode that detects x rays with 1D spatial resolution coupled to an electron streak tube to detect a continuous time history of the x rays incident on the photocathode over selected time periods. A charge-coupled-device (CCD) readout will record the signal from the streak tube. The streak tube, CCD, and associated electronics will reside in an electromagnetic interference, and electromagnetic pulse protected, hermetically sealed, temperature-controlled ...

Full aperture backscatter station measurement system on the National Ignition Facility

A full aperture backscatter station (FABS) target diagnostic has been activated on the first four beams of the National Ignition Facility. FABS measures both stimulated Brillouin scattering and stimulated Raman scattering with a suite of measurement instruments. Digital cameras and spectrometers record spectrally resolved energy for both P and S polarized light. Streaked spectrometers measure the spectral and temporal behavior of the backscattered light. Calorimeters and fast photodetectors measure the integrated energy and temporal behavior of the light, respectively. This article provides an overview of the FABS measurement system and detailed descriptions of the diagnostic instruments and the optical path.

Optimizing data recording for the NIF core diagnostic x-ray streak camera

Quantitative measurements of the sensitivity, dynamic range, and image resolution of a Nova secondary ion mass-based x-ray streak camera have been made. Comparisons were made using film versus a 4k×4k optical charge-coupled device for data readout. These tests were performed with and without an optical image intensifier tube, and with a direct electron-sensitive microchannel plate. We present results from these tests and recommendations for the National Ignition Facility core x-ray streak camera.

Calibration of initial measurements from the full aperture backscatter system on the National Ignition Facility

The full aperture backscatter system provides a measure of the spectral power, and integrated energy scattered by stimulated Brillouin (348–354 nm) and Raman (400–800 nm) scattering into the final focusing lens of the first four beams of the NIF laser. The system was designed to provide measurements at the highest expected fluences with: (1) spectral and temporal resolution, (2) beam aperture averaging, and (3) near-field imaging. This is accomplished with a strongly attenuating diffusive fiber coupler and streaked spectrometer and separate calibrated time integrated spectrometers, and imaging cameras. A new technique determines the wavelength dependent sensitivity of the complete system with a calibrated Xe lamp. Data from the calibration system are combined with scattering data from targets to produce the calibrated power and energy measurements that show significant corrections due to the broad band calibrations.

Target area and diagnostic interface issues on the National Ignition Facility (invited)

The National Ignition Facility (NIF) is under construction at Lawrence Livermore National Laboratory for the DOE Stockpile Stewardship Program. It will be used for experiments for inertial confinement fusion ignition, high energy density science, and basic science. Many interface issues confront the experimentalist who wishes to design, fabricate, and install diagnostics, and to help this process, a set of standards and guideline documents is being prepared. Compliance with these will be part of a formal diagnostic design review process. In this article we provide a short description of each, with reference to more complete documentation. The complete documentation will also be available through the NIF Diagnostics web page. Target area interface issues are grouped into three categories. First are the layout and utility interface issues which include the safety analysis report, target area facility layout; target chamber port locations; diagnostic interferences and envelopes; utilities and cable tray dist...

Near-infrared camera for the Clementine mission

The Clementine mission provided the first ever complete, systematic surface mapping of the moon from the ultra-violet to the near-infrared regions. More than 1.7 million images of the moon, earth, and space were returned from this mission. The near-infrared (NIR) multi- spectral camera, one of two workhorse lunar mapping cameras (the other being the UV/visible camera), provided approximately 200 m spatial resolution at 400 km periselene, and a 39 km across-track swath. This 1.9 kg infrared camera using a 256 X 256 InSb FPA viewed reflected solar illumination from the lunar surface and lunar horizon in the 1 to 3 micrometers wavelength region, extending lunar imagery and mineralogy studies into the near infrared. A description of this lightweight, low power NIR camera along with a summary of lessons learned is presented. Design goals and preliminary on-orbit performance estimates are addressed in terms of meeting the missions primary objective for flight qualifying the sensors for future Department of Defense flights.

Clementine longwave infrared camera

The Clementine mission provided the first ever complete, systematic surface mapping of the moon from the ultra-violet to the near-infrared regions. More than 1.7 million images of the moon, earth, and space were returned from this mission. The long-wave-infrared (LWIR) camera supplemented the UV/visible and near-infrared mapping cameras providing limited strip coverage of the moon, giving insight to the thermal properties of the soils. This camera provided approximately 100 m spatial resolution at 400 km periselene, and a 7 km across- track swath. This 2.1 kg camera using a 128 X 128 mercury-cadmium-telluride (MCT) FPA viewed thermal emission of the lunar surface and lunar horizon in the 8.0 to 9.5 micrometers wavelength region. A description of this lightweight, low power LWIR camera along with a summary of lessons learned is presented. Design goals and preliminary on-orbit performance estimates are addressed in terms of meeting the missions primary objective for flight qualifying the sensors for future Department of Defense flights.

Near to backscattered light imaging diagnostic on the National Ignition Facility

The National Ignition Facility (NIF) is being built at Lawrence Livermore National Laboratory for the U.S. Department of Energy Stockpile Stewardship Program. It will perform experiments for inertial confinement fusion ignition, high energy density science, and basic science. A target diagnostic is being developed for the NIF that will image nearly all the light scattered near the laser axis, (i.e., just outside the laser focusing lens). The diagnostic is called the near backscatter imager (NBI) and is presently required to measure stimulated Brillouin (SBS) and stimulated Raman (SRS) scattering so that the backscatter fraction will be determined with a goal of 30% uncertainty, and SBS and SRS temporal response with ∼200 ps resolution. The NBI will also provide an option to measure temporally resolved spectrum with 50 ps and ∼1 nm resolution. The diagnostic will obtain SBS and SRS scatter plate images with a retro-viewing optical digital camera placed inside the target chamber. Time integrated optical diodes and fast optical diodes will be placed at several locations on the scatter plate to obtain the power and total energy data, as well as a calibration for the scatter plate image at several points. Fibers will be placed near the diodes to provide the option to make spectral measurement. A calibration system using a low power laser, in situ, to illuminate a series of points on the plate while recording the plate image with an external camera system is also being considered.The National Ignition Facility (NIF) is being built at Lawrence Livermore National Laboratory for the U.S. Department of Energy Stockpile Stewardship Program. It will perform experiments for inertial confinement fusion ignition, high energy density science, and basic science. A target diagnostic is being developed for the NIF that will image nearly all the light scattered near the laser axis, (i.e., just outside the laser focusing lens). The diagnostic is called the near backscatter imager (NBI) and is presently required to measure stimulated Brillouin (SBS) and stimulated Raman (SRS) scattering so that the backscatter fraction will be determined with a goal of 30% uncertainty, and SBS and SRS temporal response with ∼200 ps resolution. The NBI will also provide an option to measure temporally resolved spectrum with 50 ps and ∼1 nm resolution. The diagnostic will obtain SBS and SRS scatter plate images with a retro-viewing optical digital camera placed inside the target chamber. Time integrated optical dio...

Ricor K506B Cryocooler Performance during the Clementine Mission and Ground Testing: A Status Report

Two Ricor K506B Stirling cycle cryocoolcrs with H-10 control electronics were used on the Clementine spacecraft, one cooling a 256 × 256 InSb infrared detector for the near-infrared (NIR) camera and the other cooling a 128 × 128 HgCdTe focal plane array on the longwave infrared (LWIR) camera. This is the first use of these Ricor Stirling cryocoolers in a space environment. This mission has demonstrated the use of these Clementine lightweight imaging sensors in the demanding environment of space, and and has space-qualified this Ricor cryocooler. Moreover, nearly the entire 38 million square kilometers of the Moon’s surface was mapped in 11 spectral bands, six in the near-infrared, during the 71 days of lunar mapping. The more than 1.6 million digital images collected are providing mineral typing scientific data to the international civilian scientific community.