X-ray framing cameras based on proximity-focused micro-channel plates (MCP) have been playing an important role as diagnostics of inertial confinement fusion experiments [1]. Most of the current x-ray framing cameras consist of a single MCP, a phosphor, and a recording device (e.g. CCD or photographic films). This configuration is successful for imaging x-rays with energies below 20 keV, but detective quantum efficiency (DQE) above 20 keV is severely reduced due to the large gain differential between the top and the bottom of the plate for these volumetrically absorbed photons [2]. Recently developed diagnostic techniques at LLNL require recording backlit images of extremely dense imploded plasmas using hard x-rays, and demand the detector to be sensitive to photons with energies higher than 40 keV [3]. To increase the sensitivity in the high-energy region, we propose to use a combination of two MCPs. The first MCP is operated in low gain and works as a thick photocathode, and the second MCP works as a high gain electron multiplier [4,5]. We assembled a proof-of-principle test module by using this dual MCP configuration and demonstrated 4.5% DQE at 60 keV x-rays.
Ben Hatch, Nathan Palmer, Shannon Ayers, Don Browning, Brian Felker, Joe Holder, Doug Homoelle, Shahab Khan, Joe Kimbrough, Andrew MacPhee, Robert Petre, Brad Perfect, Alan Throop, J. Wong
X-ray streak cameras are used at the National Ignition Facility for time-resolved measurements of inertial
confinement fusion metrics such as capsule implosion velocity, self-emission burn width, and x-ray bang time (time
of brightest x-ray emission). Recently a design effort was undertaken to improve the performance and operation of
the streak camera photocathode and related assemblies. The performance improvements include a new optical
design for the input of UV timing fiducial pulses that increases collection efficiency of electrons off the
photocathode, repeatability and precision of the photocathode pack assembly, and increase the input field of view
for upcoming experiments. The operational improvements will provide the ability to replace photocathode packs
between experiments in the field without removing the diagnostic from the Diagnostic Instrument Manipulator
(DIM). The new design and preliminary results are presented.
As neutron yields increase at the National Ignition Facility (NIF) the need for neutron ‘hardened’ diagnostics has also
increased. Gated Imagers located within the target chamber are exposed to neutrons which degrade image quality and
damage electronics. In an effort to maintain the signal to noise ratio (S/N) on our images and mitigate neutron induced
damage, we have implemented numerous upgrades to our X-ray framing cameras. The NIF Gated X-ray Detector
(GXD), design has evolved into the Hardened Gated X-ray Detector, HGXD. These improvements are presented with
image data taken on high yield NIF shots showing enhanced image quality. Additional upgrades were added to remotely
locate sensitive electronics and ease operational use.
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.
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.
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.
From a point of a signal-to-background ratio, phosphors are a key component of micro channel plate (MCP) based x-ray
framing cameras. In an MCP based framing camera, x-ray signal is converted to electrons, gated, amplified, and
converted back to optical signal on the phosphor. To operate x-ray framing cameras in a harsh neutron induced radiation
background of the National Ignition Facility, cathodeluminescence efficiency of the phosphor is very important. To
avoid MCP damage due to high voltage breakdown, we have been operating phosphors below 3kV (acceleration field <
6 kV/mm). The signal-to-background ratio the camera can be significantly improved by increasing the phosphor
potential to 10kV. We measured conversion efficiencies of standard phosphors at electron energies of 0.5 ~10 keV and
assessed achievable performance of them with using a numerical model.
S. Khan, P. Bell, D. Bradley, S. Burns, J. Celeste, L. Dauffy, M. Eckart, M. Gerhard, C. Hagmann, D. Headley, J. Holder, N. Izumi, M. Jones, J. Kellogg, H. Khater, J. Kimbrough, A. Macphee, Y. Opachich, N. Palmer, R. Petre, J. Porter, R. Shelton, T. Thomas, J. Worden
We present a new diagnostic for the National Ignition Facility (NIF) [1,2]. The Streaked Polar Instrumentation for Diagnosing Energetic Radiation (SPIDER) is an x-ray streak camera for use on almost-igniting targets, up to ~1017 neutrons per shot. It measures the x-ray burn history for ignition campaigns with the following requirements: X-Ray Energy 8-30keV, Temporal Resolution 10ps, Absolute Timing Resolution 30ps, Neutron Yield: 1014 to 1017. The features of the design are a heavily shielded instrument enclosure outside the target chamber, remote location of the neutron and EMP sensitive components, a precise laser pulse comb fiducial timing system and fast streaking electronics. SPIDER has been characterized for sweep linearity, dynamic range, temporal and spatial resolution. Preliminary DT implosion data shows the functionality of the instrument and provides an illustration of the method of burn history extraction.
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.
X-ray imaging is integral to the measurement of the properties of hot plasmas. To this end, a suite of gated x-ray imagers
have been developed for use in a wide range of experiments at the National Ignition Facility (NIF). These instruments
are sensitive to x-rays over the range of 0.7-90keV and can acquire images at 20ps intervals for source intensities
ranging over several orders of magnitude. We review the design, technology, and construction of these instruments and
present recent results obtained from NIF experiments in which gated x-ray imagers have played a key role.
The radiation environment associated with Inertial Confinement Fusion (ICF) experiments presents unique challenges
for x-ray imaging. We report on the performance of gated imagers that have been optimized for this harsh environment
and describe diagnostics to be deployed in the near future that will provide x-ray images of imploding ICF capsules in
the presence of backgrounds associated with neutron yields above 1016. Such images will provide crucial data that will
enable even higher neutron yields and successful ignition.
The gain spectrum in a gated multichannel intensifier output depends on the gain and spatial averaging. The spectrum
affects the minimum signal that can be detected as well as the signal to noise in the detected images. We will present
data on the gain-spectrum for the GXD detector, a gated x-ray detector to be used at the National Ignition Facility. The
data was recorded on a cooled CCD detector, with an x-ray gating time of approximately 75 ps, selected from a range of
0.2 and 1 ns electrical pulse width determined by pulse forming modules were also used. The detector was characterized
at the TRIDENT laser facility, using a 2.4 ns long x-ray at 4.75 keV. The x-rays were generated by the interaction of the
focused Trident laser beam with a Titanium target.
Due to the planar construction of present x-ray streak tubes significant off-center defocusing is observed in both static and dynamic images taken with one-dimensional resolution slits. Based on the streak tube geometry curved photocathodes with radii of curvature ranging from 3.5 to 18 inches have been fabricated. We report initial off-center focusing performance data on the evaluation of these "improved" photocathodes in an X-ray streak camera and an update on the theoretical simulations to predict the optimum cathode curvature.
Several solid state quantum computer schemes are based on the manipulation of electron and nuclear spins of single donor atoms in a solid matrix. The fabrication of qubit arrays requires the placement of individual atoms with nanometer precision and high efficiency. In this article we describe first results from low dose, low energy implantations and our development of a low energy (<10 keV), single ion implantation scheme for 31Pq+ ions. When 31Pq+ ions impinge on a wafer surface, their potential energy (9.3 keV for P15+) is released, and about 20 secondary electrons are emitted. The emission of multiple secondary electrons allows detection of each ion impact with 100% efficiency. The beam spot on target is controlled by beam focusing and collimation. Exactly one ion is implanted into a selected area avoiding a Poissonian distribution of implanted ions.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.