The multi-channel Kirkpatrick-Baez microscope (KBM), currently in use at the National Ignition Facility (NIF), uses grazing incidence multilayer crystals to focus x-rays to form an image. This diagnostic produces four images with a ~11x magnification, with a designed energy response of 10.2 ±1.5 keV at <10 μm resolution over a 300 μm x 300 μm field of view. The KBM has been designed to image the imploded core of inertial confinement fusion (ICF) experiments, which have diameters ranging over 50-100 μm and broadband emission. The self-emission spectrum is broadband and peaked at ~10 keV.
We present a new calibration of the KBM using a molybdenum (W, Z = 42) x-ray microfocus source to measure the spectral response of the instrument over its field of view. Our results measure the variation and dependence on the coalignment of the four imaging channels, relating the region of best resolution and optimal spectral response.
The National Ignition Facility (NIF) at Lawrence Livermore National Laboratory (LLNL) uses the world’s largest and most energetic laser system to explore High-Energy-Density (HED) physics. Historically, experiments at the NIF could not radiograph an Inertial Confinement Fusion (ICF) experiment at late times due to self-emission from the capsule. The Crystal Backlighter Imager diagnostic (CBI) fielded on NIF in 2017 and has allowed radiography of ICF capsules at late times. This capability is due to the very narrow bandwidth of the imaging system, which eliminates much of the self-emission. X-rays from a backlighter source (driven by NIF beams) pass through the experiment, and the CBI uses a spherically curved crystal to reflect these x-rays at near-normal incidence (Bragg angle close to 90°) onto the detector, resulting in a very narrow bandwidth microscope.
The geometry of a near-normal-incidence microscope is challenging to implement at the NIF, since the crystal must be positioned and aligned to high precision on the opposite side of the target relative to the detector. The in-chamber alignment procedure cannot take significantly longer than a simple pinhole imager, since demand for NIF shots is high and a given experiment is allotted a strict time limit. Avoiding any collision between diagnostic hardware and the target is paramount and any instrument that is placed in close proximity to a target must be able to withstand the debris produced by a 2.0 MJ NIF shot.
CBI overcomes these challenges by mounting the detector and crystal on a single diagnostic instrument manipulator (DIM). The crystal is mounted on an arm that passes around the target, positioning the crystal on the opposite side of the target to the detector. This allows much of the crystal alignment to be done before the instrument is inserted into the NIF chamber, saving time. The arm that supports the crystal is mechanized so that, during insertion of the CBI, the risk of collision with the target is minimized. The CBI is designed as a robust platform that is capable of maintaining alignment tolerances of <200 microns relative to the target, as well as survive the harsh loading on the mechanical components during a NIF 2.0 MJ energy experiment. This paper discusses the engineering challenges of
the CBI system.
D. Thorn, A. MacPhee, J. Ayers, J. Galbraith, C. Hardy, N. Izumi, D. Bradley, L. Pickworth, B. Bachmann, B. Kozioziemski, O. Landen, D. Clark, M. Schneider, K. Hill, M. Bitter, S. Nagel, P. Bell, S. Person, H. Khater, C. Smith, J. Kilkenny
In inertial confinement fusion (ICF) experiments on the National Ignition Facility (NIF), measurements of average ion temperature using DT neutron time of flight broadening and of DD neutrons do not show the same apparent temperature. Some of this may be due to time and space dependent temperature profiles in the imploding capsule which are not taken into account in the analysis. As such, we are attempting to measure the electron temperature by recording the free-free electron-ion scattering-spectrum from the tail of the Maxwellian temperature distribution. This will be accomplished with the new NIF Continuum Spectrometer (ConSpec) which spans the x-ray range of 20 keV to 30
keV (where any opacity corrections from the remaining mass of the ablator shell are negligible) and will be sensitive to temperatures between ∼ 3 keV and 6 keV. The optical design of the ConSpec is designed to be adaptable to an x-ray streak camera to record time resolved free-free electron continuum spectra for direct measurement of the dT/dt evolution across the burn width of a DT plasma. The spectrometer is a conically bent Bragg crystal in a focusing geometry that allows for the dispersion plane to be perpendicular to the spectrometer axis. Additionally, to address the spatial temperature dependence, both time integrated and time resolved pinhole and penumbral imaging will be
provided along the same polar angle. The optical and mechanical design of the instrument is presented along with estimates for the dispersion, solid angle, photometric sensitivity, and performance.
B. Bachmann, H. Abu-Shawareb, N. Alexander, J. Ayers, C. Bailey, P. Bell, L. Benedetti, D. Bradley, G. Collins, L. Divol, T. Döppner, S. Felker, J. Field, A. Forsman, J. Galbraith, C. Hardy, T. Hilsabeck, N. Izumi, C. Jarrot, J. Kilkenny, S. Kramer, O. Landen, T. Ma, A. MacPhee, N. Masters, S. Nagel, A. Pak, P. Patel, L. Pickworth, J. Ralph, C. Reed, J. Rygg, D. Thorn
X-ray penumbral imaging has been successfully fielded on a variety of inertial confinement fusion (ICF) capsule
implosion experiments on the National Ignition Facility (NIF). We have demonstrated sub-5 μm resolution imaging of
stagnated plasma cores (hot spots) at x-ray energies from 6 to 30 keV. These measurements are crucial for improving
our understanding of the hot deuterium-tritium fuel assembly, which can be affected by various mechanisms, including
complex 3-D perturbations caused by the support tent, fill tube or capsule surface roughness. Here we present the
progress on several approaches to improve x-ray penumbral imaging experiments on the NIF. We will discuss
experimental setups that include penumbral imaging from multiple lines-of-sight, target mounted penumbral apertures
and variably filtered penumbral images. Such setups will improve the signal-to-noise ratio and the spatial imaging
resolution, with the goal of enabling spatially resolved measurements of the hot spot electron temperature and material
mix in ICF implosions.
V. Fatherley, S. Batha, C. Danly, L. Goodwin, H. Herrmann, H. Jorgenson, J. Martinez, F. Merrill, J. Oertel, D. Schmidt, P. Volegov, C. Wilde, D. Fittinghoff, M. Ayers, D. Barker, G. Grim, R. Hibbard, N. Shingleton, M. Vitalich
A new neutron imager, known as Neutron Imaging System North Pole, has been fielded to image the neutrons produced in the burn region of imploding fusion capsules at the National Ignition Facility. The resolution and alignment requirements and parameters that drive the design of this system are similar to the pre-existing equatorial system, there are significant changes. This work describes the parameters and limitations driving the design of this system, discusses the metrology and alignment, and shows some data from the instrument.
The Lawrence Livermore National Laboratory (LLNL) has been developing a novel X-ray imager for the National Ignition Facility (NIF) utilizing Kirkpatrick-Baez (KB) mirror geometry. A fully assembled mirror pack contains four KB optic pairs featuring cylindrical mirrors with custom-designed multilayer coatings. Multiple interchangeable mirror packs have been commissioned for various experimental campaigns, with high spatial resolution (< 5 μm) at the center of the field of view and 12× magnification.
Tight tolerances on the grazing angles of the X-ray mirrors require precision alignment and assembly of each component via a coordinate measuring machine, and a comprehensive off-line calibration of the four KB channels at X-ray wavelengths. The main goals of the calibration campaign are to measure the performance of the multilayer, validate the assembly procedure by measuring the as-built spatial resolution and determine the best object to mirror pack distance (drive depth) of the microscope for fielding at NIF. We report on the results of this effort on the first fully assembled NIF KB X-ray imager.
The Kirkpatrick Baez Optic (KBO) diagnostic designed for the National Ignition Facility (NIF) requires very
precise alignment between four pairs of mirrors that make up four x-ray imaging channels. Furthermore, the
overlapping image axis of the four pairs must be aligned to within a 50 μm radius of the NIF target center. In
order to achieve this the diagnostic utilizes a telescoping snout that when extended, locates the mirrors at the
end of a Diagnostic Load Package (DLP), cantilevered more than three meters out from its bolted connection
points. Discussed in this paper are the structural challenges and the mechanical design solutions that were
implemented to achieve the ±50 μm pointing accuracy. During an Inertial Confinement Fusion (ICF) experiment,
the KBO diagnostic will be 117 mm away from the extremely high impulse, target implosion shock wave, which
requires a unique approach to protecting the sensitive optics which will also be discussed.
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.
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.
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.
V. Smalyuk, J. Ayers, P. Bell, L. R. Benedetti, D. Bradley, C. Cerjan, J. Emig, B. Felker, S. Glenn, C. Hagmann, J. Holder, N. Izumi, J. Kilkenny, J. Koch, O. Landen, J. Moody, K. Piston, N. Simanovskaia, C. Walton
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.
Sabrina Nagel, T. Hilsabeck, M. Ayers, B. Felker, K. Piston, T. Chung, P. Bell, D. Bradley, G. Collins, J. Kilkenny, J. Hares, A. K. L. Dymoke-Bradshaw
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.
DIXI (dilation x-ray imager) will be used to characterize ICF (inertial confinement fusion) implosions on the NIF. DIXI utilizes pulse-dilation technology1 to achieve x-ray imaging with temporal gate times below 10 ps. Time resolved x-ray measurements were conducted using the COMET laser facility at the Lawrence Livermore National Laboratory. Here we focus on some of the challenges faced by the large aperture photo cathode of the instrument and report on how to maintain a at photo cathode as well as how the required spatial resolution of the instrument is achieved.
Jay Ayers, Brian Felker, Vladimir Smalyuk, Nobuhiko Izumi, Ken Piston, Joe Holder, Gary Power, Fred Allen, Natalia Simanovska, Perry Bell, Dave Bradley, Zachary Lamb
Gated X-Ray imagers have been used on many ICF experiments around the world for time resolved
imaging of the target implosions. ARIANE (Active Readout In A Neutron Environment) has been
developed for use in the National Ignition Facility and has been deployed in multiple phases.
Phase 1 (complete) known as ARIANE Ultra Light (Alignment proof of concept), Phase 2a known as
ARIANE Light (complete) (X-ray gated detector with electronic recording), Phase 2b (complete)
(X-ray gated detector with film recording) and Phase 3 known as ARIANE Heavy which is currently
under development. The ARIANE diagnostic is comprised of the following subsystems: pinhole
imaging system, filtering, detector head, detector head electronics, control electronics, CCD, and film
recording systems. The phased approach allows incremental increases in tolerance to neutron yield.
Phase 2a and 2b have been fielded successfully and captured gated implosion images on CCD and
film at neutron yields up to 7 x 1014. As the yields in the NIF increase Phase 3 will be a longer term
solution incorporating an indirect optical path, hardened advanced detectors and significant (tons) of
shielding. Design and Initial commissioning data for Phase 1-2b are presented here.
N. Izumi, J. Emig, J. Moody, C. Middleton, J. Holder, K. Piston, V. Smalyuk, C. Hagmann, J. Ayers, J. Celeste, C. Cerjan, B. Felker, C. Sorce, K. Krauter, S. Glenn, J.-L. Bourgade, J. Kilkenny, D. Bradley, P. Bell
Phosphors are key components of x-ray framing cameras. On implosion experiments at the National Ignition Facility, the
x-ray framing cameras must operate in a harsh neutron induced ionizing radiation. One promising approach of neutron
induced background reduction is separation of the neutron background with using difference of x-ray and neutron time-of-
flight. To complete x-ray imaging before arrival of the neutron induced radiation to the detector, it is crucial to find a
phosphor which has high efficiency and fast decay time. We tested various phosphor materials to optimize design of
framing cameras for implosion experiments.
V. Smalyuk, J. Ayers, P. Bell, J.-L. Bourgade, D. Bradley, J. Celeste, C. Cerjan, S. Darbon, J. Emig, B. Felker, C. Hagmann, J. Holder, N. Izumi, J. Kilkenny, J. Moody, K. Piston, A. Rousseau, C. Sorce, R. Tommasini
X-ray imaging instruments will operate in a harsh ionizing radiation background environment on implosion experiments
at the National Ignition Facility. These backgrounds consist of mostly neutrons and gamma rays produced by inelastic
scattering of neutrons. Imaging systems based on x-ray framing cameras with film and CCD's have been designed to
operate in such harsh neutron-induced background environments. Some imaging components were placed inside a
shielded enclosure that reduced exposures to neutrons and gamma rays. Modeling of the signal and noise of the x-ray
imaging system is presented.
C. Hagmann, J. Ayers, P. Bell, J.-L. Bourgade, D. Bradley, J. Celeste, C. Cerjan, S. Darbon, J. Emig, B. Felker, S. Glenn, J. Holder, N. Izumi, J. Kilkenny, J. Moody, K. Piston, A. Rousseau, V. Smalyuk, C. Sorce
The large fluence of 14-MeV neutrons produced in high-yield inertial confinement fusion (ICF) experiments creates a
variety of backgrounds in x-ray imagers viewing the implosion. Secondary charged particles produce background light
by Cherenkov emission, phosphor screen excitation and possibly scintillation in the optical components of the imager. In
addition, radiation induced optical absorption may lead to attenuation of the signal. Noise is also produced directly in the
image recorder itself (CCD or film) via energy deposition by electrons and heavy charged particles such as protons and
alphas. We will present results from CCD background measurements and compare them to Monte Carlo calculations. In
addition we show measurements of luminescence and long-term darkening for some of the glasses employed in imagers.
This manuscript discusses the development of reflective optics for the x-ray offset mirror systems of the Linac Coherent Light Source (LCLS), a 0.15-1.5 nm free-electron laser (FEL) at the Stanford Linear Accelerator Center (SLAC). The unique properties (such as the high peak brightness) of the LCLS FEL beam translate to strict limits in terms of materials choice, thus leading to an x-ray mirror design consisting of a reflective coating deposited on a silicon substrate.
Furthermore, the physics requirements for these mirrors result in stringent surface figure and finish specifications that challenge the state-of-the-art in x-ray substrate manufacturing, thin film deposition, and metrology capabilities. Recent experimental results on the development, optimization, and characterization of the LCLS soft x-ray mirrors are presented in this manuscript, including: precision surface metrology on the silicon substrates, and the development of boron carbide reflective coatings with reduced stress and thickness variation < 0.14 nm rms across the 175-mm clear aperture area of the LCLS soft x-ray mirrors.
Mark Lowry, Corey Bennett, Stephen Vernon, Tiziana Bond, Rebecca Welty, Elaine Behymer, Holly Petersen, Adam Krey, Richard Stewart, Nobuhiko Kobayashi, Victor Sperry, Phillip Stephan, Cathy Reinhardt, Sean Simpson, Paul Stratton, Richard Bionta, Mark McKernan, Elden Ables, Linda Ott, Steven Bond, Jay Ayers, Otto Landen, Perry Bell
We present a new x-ray detection technique based on optical measurement of the effects of x-ray absorption and electron
hole pair creation in a direct band-gap semiconductor. The electron-hole pairs create a frequency dependent shift in optical refractive index and absorption. This is sensed by simultaneously directing an optical carrier beam through the same volume of semiconducting medium that has experienced an xray induced modulation in the electron-hole
population. If the operating wavelength of the optical carrier beam is chosen to be close to the semiconductor band-edge, the optical carrier will be modulated significantly in phase and amplitude.
This approach should be simultaneously capable of very high sensitivity and excellent temporal response, even in the difficult high-energy xray regime. At xray photon energies near 10 keV and higher, we believe that sub-picosecond temporal responses are possible with near single xray photon sensitivity. The approach also allows for the convenient and EMI robust transport of high-bandwidth information via fiber optics. Furthermore, the technology can be scaled to imaging applications. The basic physics of the detector, implementation considerations, and preliminary experimental data are presented and discussed.
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