This PDF file contains the front matter associated with SPIE Proceedings Volume 8850, including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.

The drive to ever higher intensities and the move to shorter focal length reflective optics for focussing in solid target interactions are increasingly important for studies into high intensity secondary source generation, QED and high field studies. To ensure reproducible optimum interaction conditions, presents a significant problem for accurate target positioning. Commercial optical systems exist to aid the imaging and positioning of targets. However, these are often expensive and difficult to situate within the limited space usually available inside the interaction chamber. At the Astra-Gemini system of the Central Laser Facility, the push for intensities above I = 10²¹ Wcm^-2 with f/2 and f/1 focussing optics means positioning targets within the Rayleigh range of < few microns. Here, we present details of two systems to be implemented on the Astra-Gemini system to cheaply and accurately position targets with ≈ micron accuracy. These involve:- (i) a multi-wavelength interferometer to enable sub-micron accuracy in the positioning of the front surface at the interaction point within the Rayleigh range and (ii) a small, low cost near field/far field microscope with illumination at 800nm (the same as the Gemini IR beam) for imaging the rear of the target and the focal plane with high resolution. The combination of these two systems significantly improves our accuracy in target positioning and also results in a decrease in the time required to align targets between shots.

The National Ignition Facility (NIF) utilizes several different pixelated sensor technologies for various measurement systems that include alignment cameras, laser energy sensors, and high-speed framing cameras. These systems remain in the facility where they are exposed to 14MeV neutrons during a NIF shot. The image quality of the sensors degrades as a function of radiation-induced damage. This article reports on a figure-of-merit technique that aids in the tracking of the performance of pixelated sensors when exposed to neutron radiation from NIF. The sensor dark current growth can be displayed over time in a 2D visual representation for tracking radiation induced damage. Predictions of increased noise as a function of neutron fluence for future NIF shots allow simulation of reduced performance for each of the individual camera applications. This predicted longevity allows for proper management of the camera systems.

Estimating the vulnerability is a key challenge for plasma diagnostics designed to operate in radiative background associated with megajoule class laser facilities. Since DT shots at OMEGA laser facility reproduce the perturbing source expected during the first 100 nanoseconds of a typical DT shot realized at National Ignition Facility (NIF) and Laser MegaJoule facility (LMJ), vulnerability of diagnostic elements such as optical relays or optical analyzers were experimentally studied and, if necessary, hardening approaches have been initiated to authorize their use at higher radiative constraints. Other facilities such as nuclear reactor or accelerator have been also used to estimate vulnerability issues as radiation induced emission of glasses or damage in multilayer coatings.

The Diagnostic Instrument Manipulators (DIMs) are two-staged, telescoping systems that allow the precise alignment and positioning of various x-ray, optical, nuclear, and other diagnostics in the National Ignition Facility (NIF) Target Chamber. Designed to be reconfigurable and exchangeable between NIF experiments, the second stage of the DIM is referred to as the Diagnostic Load Package (DLP), which is most often comprised of a cart, diagnostic, and detachable snout. As experiments continue to increase radiation levels, various upgrades have been made to the DIMs to improve reliability and operational efficiency. These upgrades reduce worker exposure and increase experimental shot rates. Specific to this paper, the design and operation of dedicated DLP handling and storage units (DHUs and DSUs) are discussed in addition to their transport equipment. Hardware and process improvements for reduced worker exposure during general DIM access are also featured. Finally, the DLP limit switches have been upgraded to magneticallyactuated proximity sensors for reliability, improved shot rate, and increased user flexibility.

Periodic sensitivity calibration of imaging plates (IP) is crucial for quantitative understanding of x-ray data obtained at the National Ignition Facility (NIF). To test the x-ray sensitivity of the IPs and the scanners, we developed an x-ray exposure station based on radioactive isotopes (55Fe, 109Cd, and 241Am). This apparatus provides a convenient setup for a periodical test of the IP’s and the scanners. On NIF implosion experiments with deuterium-tritium mixture fuel, the neutrons produced in the capsule hit the imaging plates and impose background signal. Therefore it is also important to know the neutron sensitivity of the IPs. The sensitivity for 14 MeV neutrons was measured on high neutron yield shots at the OMEGA laser facility. The measured sensitivities were compared with the results of Monte Carlo simulations.

This paper describes a method to calibrate image plate sensitivity for use in the low energy spectral range. Image plates, also known as photostimulable luminescence (PSL) detectors, have often proved to be a valuable tool as a detector for plasma physics studies. Their advantages of large dynamic range, high stopping power, and resistance to neutron damage sometimes outweigh the problems of limited resolution and the remote processing required. The neutron damage resistance is required when the X-ray source is producing a high neutron flux. The Static X-ray Imager (SXI) is a key diagnostic on the National Ignition Facility (NIF) target chamber at LLNL for use in determining the symmetry of the laser beams. The SXI is essential to proper interpretation of the data from the Dante diagnostic to determine the X-ray radiation temperature. It is comprised of two diagnostics located at the top and the bottom of the target chamber. The usual detector is a large array CCD camera. For shots giving high yields of neutrons, the camera would not only be blinded by the neutrons, it would be damaged. To get around this problem, an image plate (IP) is used as the detector. The NIF application covers the energy range from 700 to 5000 eV. The type of image plates typically used for plasma physics are the Fuji BAS-MS, BAS-SR, and BAS-TR models. All models consist of an X-ray sensitive material made of BaF(Br,I):Eu²⁺ embedded in a plastic binder. X-rays incident on the phosphor ionize the Eu ²⁺ producing Eu³⁺ and free electrons that are trapped in lattice defects (F-centers) produced by the absence of halogen ions in the BaF₂ crystal. An image plate readout scanner irradiates the IP with a red laser causing reduction of the Eu³⁺ and emission of a blue photon. The photon is collected using a photomultiplier and digitized to make an electronic image. Image plates are cleared of all F-centers by putting them under a bright light for about 10 minutes. They are then ready for producing a new X-ray image. The MS IP model has the higher sensitivity and the SR IP and TR IP models are designed for higher resolution. The MS and SR IPs have a thin Mylar coating that protects the sensitive layer. The TR model has no protective layer and is more sensitive at the lower X-ray energies but must be handled more carefully. The raw image data from the Fuji scanner can be converted to units of PSL that are proportional to the photon count. The equation relating PSL to the raw greyscale value is: PSL = (R/100)²(4000/S)exp₁₀{L(G/(2^B-1)-1/2)} where R is the resolution in μm S is the sensitivity setting L is the latitude B is the dynamic range (8 or 16 bits) G is the raw image greyscale value. The IP photon sensitivity is defined as the PSL output per photon input and is a function of the photon energy. Meadowcroft et al in 2008 published the sensitivity for the three types of image plates in the spectral range from 1 to 100 keV. Maddox et al measured the sensitivity for type MS and SR image plates from 8 to 80 keV using the NSTec High Energy X-ray (HEX) source, a fluorescer type X-ray source. The Meadowcroft and Maddox measurements used similar X-ray sources for the higher spectral and the same type of IP scanner, the FLA 7000. There is reasonable agreement between the Maddox and Meadowcroft sensitivity measurements of MS and SR type IP for the at spectral energies above 20 keV, but the Maddox sensitivities are much lower than those of Meadowcroft in the energy range below 20 keV. Recently Bonnet et al published a model for the photon sensitivity based upon the amount of energy deposited and Monte Carlo calculations to incorporate the specifics of the X-ray absorption and the readout process. The model was calibrated for sensitivity using radioactive sources. The model was compared to the previous publications cited. The Bonnet model tends to agree with the Meadocroft measurements at the low spectral energies. The present paper describes the measurement of IP sensitivity in the spectral range from 700 to 8000 eV. The sensitivity in this spectral range had not previously been measured and was needed for the NIF application. A calibration at the low energy range was done using a diode source and a band pass filter. X-ray beam is filtered and limited by the applied voltage to provide a spectral band that is about 1/10 of the average spectral energy. The X-ray flux is measured using a photodiode that is traceable to National Institute for Standards and Technology (NIST). The spectrum for each X-ray band is measured using a silicon drifted detector. The photodiode calibration method is described. Measurements were made on SR, TR, and specially coated TR image plates. The measurement results will be presented and the uncertainties in the measurement will be discussed. The results will be compared to other measurements and estimation methods.

The Static X-Ray Imager (SXI) is a National Ignition Facility (NIF) diagnostic that uses a CCDcamera to record timeintegrated X-ray images of target features such as the laser entrance hole of hohlraums. SXI has two dedicated positioners on the NIF target chamber for viewing thetarget from above and below, and the X-ray energies of interest are 870 eV for the “soft” channel and 3 – 5 keV for the “hard” channels. The original cameras utilize a large formatbackilluminated 2048 x 2048 CCD sensor with 24 micron pixels. Since the original sensor isno longer available, an effort was recently undertaken to build replacement cameras withsuitable new sensors. Three of the new cameras use a commercially available front-illuminatedCCD of similar size to the original, which has adequate sensitivity for the hard X-ray channelsbut not for the soft. For sensitivity below 1 keV, Lawrence Livermore National Laboratory (LLNL) had additional CCDs back-thinned andconverted to back-illumination for use in the other two new cameras. In this paper we describethe characteristics of the new cameras and present performance data (quantum efficiency, flat field, and dynamic range) for the front- and back-illuminated cameras, with comparisons to the originalcameras.

Charge-injection devices (CIDs) are solid-state 2D imaging sensors similar to CCDs, but their distinct architecture makes CIDs more resistant to ionizing radiation. CID cameras have been used extensively for X-ray imaging at the OMEGA Laser Facility with neutron fluences at the sensor approaching 10⁹ n/cm² (DT, 14 MeV). A CID Camera X-ray Imager (CCXI) system has been designed and implemented at NIF that can be used as a rad-hard electronic-readout alternative for time-integrated X-ray imaging. This paper describes the design and implementation of the system, calibration of the sensor for X-rays in the 3 - 14 keV energy range, and preliminary data acquired on NIF shots over a range of neutron yields. The upper limit of neutron fluence at which CCXI can acquire useable images is ~ 10⁸ n/cm² and there are noise problems that need further improvement, but the sensor has proven to be very robust in surviving high yield shots (~ 10¹⁴ DT neutrons) with minimal damage.

The National Ignition Facility requires a radiation-hardened, megapixel CMOS imaging sensor-based camera to be a direct physical and operational replacement for the CCD cameras currently used in x-ray streak cameras and gated imaging detectors. Camera electronics were selected to operate up to 10 krad(Si). The camera incorporates a fast dump of the sensor followed by exposure and image readout. This allows the dumping of charge due to the prompt radiation background and then readout of the longer persistence phosphor image from the x-ray diagnostics. Internal timing delays and optical performance were measured for a radiation-tolerant camera, based on the 2k by 2k CMV4000 sensor from CMOSIS Inc.

X-ray imaging diagnostics instruments will operate in a harsh ionizing radiation background environment during ignition experiments at the National Ignition Facility (NIF). This background consists of mostly neutrons and gamma rays produced by inelastic scattering of neutrons. An imaging system, M-ARIANE (Mirror-assisted Active Readout In A Neutron Environment), based on an x-ray framing camera with film, has been designed to operate in such a harsh neutron-induced background environment. Multilayer x-ray mirrors and a shielding enclosure are the key components of this imaging system which is designed to operate at ignition neutron yields of ~1e18 on NIF. Modeling of the neutronand gamma-induced backgrounds along with the signal and noise of the x-ray imaging system is presented that display the effectiveness of this design.

Gated X-Ray imagers have been used on many ICF experiments around the world for time resolved imaging of the target implosions. DIXI (Dilation X-ray Imager) is a new fixed base diagnostic that has been developed for use in the National Ignition Facility. The DIXI diagnostic utilizes pulse-dilation technology [1,2,3,4] and uses a high magnification pinhole imaging system to project images onto the instrument. DIXI is located outside the NIF target chamber approximately 6.5m from target chamber center (TCC). The pinholes are located 10cm from TCC and are aligned to the DIXI optical axis using a diagnostic instrument manipulator (DIM) on an adjacent port. By use of an extensive lead and poly shielded drawer enclosure DIXI is capable of collecting data at DT neutron yields up to Yn~ 10¹⁶ on CCD readout and up to Yn~ 10¹⁷ on film. Compared to existing pinhole x-ray framing cameras DIXI also provides a significant improvement in temporal resolution, <10ps, and the ability to capture a higher density of images due to the fact the pinhole array does not require collimators. The successful deployment of DIXI on the NIF required careful attention to the following subsystems, pinhole imaging, debris shielding, filtering and image plate (FIP), EMI protection, large format CsI photocathode design, detector head, detector head electronics, control electronics, CCD, film recording and neutron shielding. Here we discuss the initial design, improvements implemented after rigorous testing, infrastructure and commissioning of DIXI on the NIF.

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.

At the Lawrence Livermore National Laboratory (LLNL) we are designing, developing and testing multiple Kirkpatrick-Baez (KB) optics to be added to the suite of x-ray diagnostic instruments for the National Ignition Facility (NIF). Each optic consists of four KB channels made of spherically super-polished x-ray substrates. These substrates are multilayer-coated to allow steep grazing angle geometry and wavelength filtering. These optics are customized for different experiments and will provide NIF with an alternative x-ray imaging technique to pinholes, improving both resolution and photon throughput. With this manuscript we describe KB optic requirements, specifications, optical and multilayer designs.

In laser-driven inertial confinement fusion, hot electrons can preheat the fuel and prevent compression of the capsule to ignition conditions. Measuring the hot-electron population in these high-intensity, laser-driven experiments is key to understanding the laser–plasma interaction and the resulting target evolution. This can be inferred from the bremsstrahlung generated by the interaction of the hot electrons with the target. At the National Ignition Facility (NIF), the filter-fluorescer x-ray diagnostic (FFLEX), a multichannel, hard x-ray spectrometer operating in the 20- to 500-keV range, was recently upgraded to provide time-resolved measurements of the bremsstrahlung spectrum. Characterization data is presented for the upgraded setup, as well as recent results from ignition-scale experiments.

The National Ignition Facility (NIF) utilizes over 6 optical streak camera systems that collect data from 350 to 1053 nm band during a full system laser shot. The camera systems are configured to collect single or multiple intensity profile signals, spectrally resolved data, spatially resolved interferometry data, and spatially resolved intensity data. The output data format represents the temporal resolution of the recorded event as a two dimensional image. For all these configurations, the time record ranges from 3ns to 100 ns. The precision of the recorded data requires several calibration techniques that provide an overall 2D space-time warp correction that is applied to the raw streak data. The article shall review the typical applications of the optical streak cameras on NIF, the performance of the calibration applied to shot data while in operation and the overall performance and reliability of the camera systems over the several years of operation.

We present performance data for Mach-Zehnder optical modulators fielded on the National Ignition Facility (NIF) as a potential signal path upgrade for the South Pole Bang Time diagnostic. A single channel demonstration system has been deployed utilizing two modulators operating in a 90° In phase and Quadrature (I/Q) configuration. X-ray target emission signals are split and fed into two recording systems: a reference CRT based oscilloscope, Greenfield FTD10000, and the dual Mach-Zehnder system. Results of X-ray implosion time (bang time) determination from these two recording systems are compared and presented.

DIXI utilizes pulse-dilation technology to achieve x-ray imaging with temporal gate times below 10 ps. The longitudinal magnetic eld used to guide the electrons during the dilation process results in a warped image, similar to an optical distortion from a lens. Since the front end, where x-rays are converted into electrons at the beginning of the magnetic eld, determines the temporal resolution these distortions in uence the temporal width of the images at the back end, where it is captured. Here we discuss the measurements and methods used to reverse the magnetic warp e ect in the DIXI data. The x-ray measurements were conducted using the COMET laser facility at the Lawrence Livermore National Laboratory.

We present evidence of an artifact in gated x-ray framing cameras that can severely impact image quality. This artifact presents as a spatially-varying, high-intensity background and is correlated with experiments that produce a high flux of x-rays during the time before the framing camera is triggered. Dedicated experiments using a short pulse UV laser that arrives before, during, and after the triggering of the framing camera confirm that these artifacts can be produced by light that arrives in advance of the voltage pulse that triggers the camera. This is consistent with these artifacts being the result of photoelectrons produced uniformly at the active area of the camera by early incident light and then selectively trapped by the electromagnetic (EM) fields of the camera. Simulations confirm that the EM field above the active surface can act to confine electrons produced before the camera is triggered. We further present a method to suppress these artifacts by installing a conducting electrode in front of the active area of the framing camera. This device suppresses artifacts by attracting any electrons liberated by x-rays that arrive before the camera is triggered.

Strip velocity measurements of gated X-ray imagers are presented using an ultra-short pulse laser. Obtaining time- resolved X-ray images of inertial confinement fusion shots presents a difficult challenge. One diagnostic developed to address this challenge is the gated X-ray imagers. The gated X-ray detectors (GXDs) developed by Lawrence Livermore National Laboratory and Los Alamos National Laboratory use a microchannel plate (MCP) coated with a gold strip line, which serves as a photocathode. GXDs are used with an array of pinholes, which image onto various parts of the GXD image plane. As the pulse sweeps over the strip lines, it creates a time history of the event with consecutive images. In order to accurately interpret the timing of the images obtained using the GXDs, it is necessary to measure the propagation of the pulse over the strip line. The strip velocity was measured using a short pulse laser with a pulse duration of approximately 1-2 ps. The 200nm light from the laser is used to illuminate the GXD MCP. The laser pulse is split and a retroreflective mirror is used to delay one of the legs. By adjusting the distance to the mirror, one leg is temporally delayed compared to the reference leg. The retroreflective setup is calibrated using a streak camera with a 1 ns full sweep. Resolution of 0.5 mm is accomplished to achieve a temporal resolution of ~5 ps on the GXD strip line.

This paper describes the design considerations for Target Diffraction In-Situ (TARDIS), an x-ray diffraction diagnostic at the National Ignition Facility. A crystal sample is ramp-compressed to peak pressures between 10 and 30 Mbar and, during a pressure hold period, is probed with quasi-monochromatic x-rays emanating from a backlighter source foil. The crystal spectrography diffraction lines are recorded onto image plates. The crystal sample, filter, and image plates are packaged into one assembly, allowing for accurate and repeatable target to image plate registration. Unconverted laser light impinges upon the device, generating debris, the effects of which have been mitigated. Dimpled blast shields, high strength steel alloy, and high-z tungsten are used to shield and protect the image plates. A tapered opening was designed to provide adequate thickness of shielding materials without blocking the drive beams or x-ray source from reaching the crystal target. The high strength steel unit serves as a mount for the crystal target and x-ray source foil. A tungsten body contains the imaging components. Inside this sub-assembly, there are three image plates: a 160 degree field of view curved plate directly opposite the target opening and two flat plates for the top and bottom. A polycarbonate frame, coated with the appropriate filter material and embedded with registration features for image plate location, is inserted into the diagnostic body. The target assembly is metrologized and then the diagnostic assembly is attached.

We will describe the installation and wavelength calibration of a multiple monochromatic imager [MMI]1 to be used on mix experiments at National Ignition Facility [NIF]2. The imager works between 8 and 13 keV, has a spatial resolution of 16 micrometers and generates many images each with an energy bandwidth of ~80 eV. The images are recorded either on image plates or on gated x-ray detectors. We will describe: how we aligned the instrument on the bench using visible light, how we checked the alignment and determined the energy range using a k-alpha x-ray source, and how we installed and aligned the instrument to the NIF target chamber.