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Oct 2012

Volume 83, Issue 10, Articles (10xxxx)

Issue Cover Spotlight Figure

Rev. Sci. Instrum. 83, 101301 (2012); http://dx.doi.org/10.1063/1.4750234 (26 pages)

N. L. Kugland, D. D. Ryutov, C. Plechaty, J. S. Ross, and H.-S. Park

Proton imaging is widely used to reveal electric and magnetic field structures in high energy density plasmas. Even for smooth parent structures, strongly deflected protons can form images with strange shapes or singular lines of very high intensity (i.e. caustics).

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back to top X-ray Detectors and Spectrometers—Jeffrey A. Koch, Session Chairman

Extreme ultraviolet spectroscopy and modeling of Cu on the SSPX Spheromak and laser plasma “Sparky”

M. E. Weller, A. S. Safronova, J. Clementson, V. L. Kantsyrev, U. I. Safronova, P. Beiersdorfer, E. E. Petkov, P. G. Wilcox, and G. C. Osborne

Rev. Sci. Instrum. 83, 10E101 (2012); http://dx.doi.org/10.1063/1.4727916 (3 pages)

Online Publication Date: 7 June 2012

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Impurities play a critical role in magnetic fusion research. In large quantities, impurities can cool and dilute plasma creating problems for achieving ignition and burn; however in smaller amounts the impurities could provide valuable information about several plasma parameters through the use of spectroscopy. Many impurity ions radiate within the extreme ultraviolet (EUV) range. Here, we report on spectra from the silver flat field spectrometer, which was implemented at the Sustained Spheromak Physics experiment (SSPX) to monitor ion impurity emissions. The chamber within the SSPX was made of Cu, which makes M-shell Cu a prominent impurity signature. The Spect3D spectral analysis code was utilized to identify spectral features in the range of 115–315 Å and to more fully understand the plasma conditions. A second set of experiments was carried out on the compact laser-plasma x-ray/EUV facility “Sparky” at UNR, with Cu flat targets used. The EUV spectra were recorded between 40–300 Å and compared with results from SSPX.
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52.25.Vy Impurities in plasmas
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
52.57.-z Laser inertial confinement

C-III flow measurements with a coherence imaging spectrometer

T. R. Weber, S. L. Allen, and J. Howard

Rev. Sci. Instrum. 83, 10E102 (2012); http://dx.doi.org/10.1063/1.4728311 (3 pages)

Online Publication Date: 14 June 2012

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This work describes a coherence imaging spectrometer capable of making spatially resolved CIII flow measurements in the DIII-D lower divertor. The spectrometer exploits a periscope view of the plasma to produce line-of-sight averaged velocity measurements of CIII. From these chord averaged flow measurements, a 2D poloidal cross section of the CIII flow is tomographically reconstructed. Details of the diagnostic setup, acquired data, and data analysis will be presented, along with prospects for future applications.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.55.Fa Tokamaks, spherical tokamaks
52.55.Rk Power exhaust; divertors

X-ray absorption spectroscopy of aluminum z-pinch plasma with tungsten backlighter planar wire array source

G. C. Osborne, V. L. Kantsyrev, A. S. Safronova, A. A. Esaulov, M. E. Weller, I. Shrestha, V. V. Shlyaptseva, and N. D. Ouart

Rev. Sci. Instrum. 83, 10E103 (2012); http://dx.doi.org/10.1063/1.4729499 (3 pages)

Online Publication Date: 18 June 2012

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Absorption features from K-shell aluminum z-pinch plasmas have recently been studied on Zebra, the 1.7 MA pulse power generator at the Nevada Terawatt Facility. In particular, tungsten plasma has been used as a semi-backlighter source in the generation of aluminum K-shell absorption spectra by placing a single Al wire at or near the end of a single planar W array. All spectroscopic experimental results were recorded using a time-integrated, spatially resolved convex potassium hydrogen phthalate (KAP) crystal spectrometer. Other diagnostics used to study these plasmas included x-ray detectors, optical imaging, laser shadowgraphy, and time-gated and time-integrated x-ray pinhole imagers. Through comparisons with previous publications, Al K-shell absorption lines are shown to be from much lower electron temperature (∼10–40 eV) plasmas than emission spectra (∼350–500 eV).
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52.70.La X-ray and γ-ray measurements
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.58.Lq Z-pinches, plasma focus, and other pinch devices
52.25.-b Plasma properties

Implementation of a multichannel soft x-ray diagnostic for electron temperature measurements in TJ-II high-density plasmas

D. Baião, F. Medina, M. Ochando, I. Pastor, C. Varandas, A. Molinero, and J. Chércoles

Rev. Sci. Instrum. 83, 10E104 (2012); http://dx.doi.org/10.1063/1.4729669 (3 pages)

Online Publication Date: 18 June 2012

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Based on the multi-foil technique, a multichannel soft x-ray diagnostic for electron temperature measurements has been recently implemented in the TJ-II stellarator. The diagnostic system is composed by four photodiodes arrays with beryllium filters of different thickness. An in-vacuum amplifier board is coupled to each array, aiming at preventing induced noise currents. The Thomson scattering and the vacuum ultraviolet survey diagnostics are used for assessing plasma profiles and composition, being the analysis carried out with the radiation code IONEQ. The electron temperature is determined through the different signal-pair ratios with temporal and spatial resolution. The design and preliminary results from the diagnostic are presented.
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52.70.La X-ray and γ-ray measurements
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.55.Jd Magnetic mirrors, gas dynamic traps
52.65.-y Plasma simulation

X-ray bang-time measurements at the National Ignition Facility using a diamond detector

M. A. Barrios, A. MacPhee, S. P. Regan, J. Kimbrough, S. R. Nagel, L. R. Benedetti, S. F. Khan, D. Bradley, P. Bell, D. Edgell, and G. W. Collins

Rev. Sci. Instrum. 83, 10E105 (2012); http://dx.doi.org/10.1063/1.4729667 (3 pages)

Online Publication Date: 22 June 2012

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A chemical vapor deposition polycrystalline photoconductive diamond detector was fielded at NIF to measure the time of peak x-ray emission, or x-ray bang time, of inertial confinement fusion implosions. Imaging the capsule with a pinhole provides contrast against Hohlraum emission, allowing clear identification of the capsule component in the raw scope trace. X-ray bang time was measured to within ±41–46 ps with the internal photoconductive diamond detector.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
42.79.Pw Imaging detectors and sensors
85.60.-q Optoelectronic devices

Ultra fast x-ray streak camera for ten inch manipulator based platforms

E. V. Marley, R. Shepherd, S. Fulkerson, L. James, J. Emig, and D. Norman

Rev. Sci. Instrum. 83, 10E106 (2012); http://dx.doi.org/10.1063/1.4729500 (3 pages)

Online Publication Date: 27 June 2012

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Ultra fast x-ray streak cameras are a staple for time resolved x-ray measurements. There is a need for a ten inch manipulator (TIM) based streak camera that can be fielded in a newer large scale laser facility. The Lawrence Livermore National Laboratory ultra fast streak camera's drive electronics have been upgraded and redesigned to fit inside a TIM tube. The camera also has a new user interface that allows for remote control and data acquisition. The system has been outfitted with a new sensor package that gives the user more operational awareness and control.
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07.85.-m X- and γ-ray instruments
42.79.Pw Imaging detectors and sensors

Streaked x-ray spectrometer having a discrete selection of Bragg geometries for Omega

M. Millecchia, S. P. Regan, R. E. Bahr, M. Romanofsky, and C. Sorce

Rev. Sci. Instrum. 83, 10E107 (2012); http://dx.doi.org/10.1063/1.4729501 (3 pages)

Online Publication Date: 2 July 2012

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The streaked x-ray spectrometer (SXS) is used with streak cameras [D. H. Kalantar, P. M. Bell, R. L. Costa, B. A. Hammel, O. L. Landen, T. J. Orzechowski, J. D. Hares, and A. K. L. Dymoke-Bradshaw, in 22nd International Congress on High-Speed Photography and Photonics, edited by D. L. Paisley and A. M. Frank (SPIE, Bellingham, WA, 1997), Vol. 2869, p. 680] positioned with a ten-inch manipulator on OMEGA [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)]10.1016/S0030-4018(96)00325-2 and OMEGA EP [L. J. Waxer et al., Presented at CLEO/QELS 2008, San Jose, CA, 4–9 May 2008 (Paper JThB1)] for time-resolved, x-ray spectroscopy of laser-produced plasmas in the 1.4- to 20-keV photon-energy range. These experiments require measuring a portion of this photon-energy range to monitor a particular emission or absorption feature of interest. The SXS relies on a pinned mechanical reference system to create a discrete set of Bragg reflection geometries for a variety of crystals. A wide selection of spectral windows is achieved accurately and efficiently using this technique. It replaces the previous spectrometer designs that had a continuous Bragg angle adjustment and required a tedious alignment calibration procedure. The number of spectral windows needed for the SXS was determined by studying the spectral ranges selected by OMEGA users over the last decade. These selections are easily configured in the SXS using one of the 25 discrete Bragg reflection geometries and one of the six types of Bragg crystals, including two curved crystals.
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07.85.Nc X-ray and γ-ray spectrometers
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
52.70.La X-ray and γ-ray measurements
06.20.fb Standards and calibration
84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)

Imaging x-ray Thomson scattering spectrometer design and demonstration (invited)

E. J. Gamboa, C. M. Huntington, M. R. Trantham, P. A. Keiter, R. P. Drake, D. S. Montgomery, J. F. Benage, and S. A. Letzring

Rev. Sci. Instrum. 83, 10E108 (2012); http://dx.doi.org/10.1063/1.4731755 (5 pages) | Cited 1 time

Online Publication Date: 3 July 2012

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In many laboratory astrophysics experiments, intense laser irradiation creates novel material conditions with large, one-dimensional gradients in the temperature, density, and ionization state. X-ray Thomson scattering is a powerful technique for measuring these plasma parameters. However, the scattered signal has previously been measured with little or no spatial resolution, which limits the ability to diagnose inhomogeneous plasmas. We report on the development of a new imaging x-ray Thomson spectrometer (IXTS) for the Omega laser facility. The diffraction of x-rays from a toroidally curved crystal creates high-resolution images that are spatially resolved along a one-dimensional profile while spectrally dispersing the radiation. This focusing geometry allows for high brightness while localizing noise sources and improving the linearity of the dispersion. Preliminary results are presented from a scattering experiment that used the IXTS to measure the temperature profile of a shocked carbon foam.
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52.70.La X-ray and γ-ray measurements
07.85.Nc X-ray and γ-ray spectrometers

Compact “diode-based” multi-energy soft x-ray diagnostic for NSTX

K. Tritz, D. J. Clayton, D. Stutman, and M. Finkenthal

Rev. Sci. Instrum. 83, 10E109 (2012); http://dx.doi.org/10.1063/1.4731741 (3 pages) | Cited 2 times

Online Publication Date: 6 July 2012

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A novel and compact, diode-based, multi-energy soft x-ray (ME-SXR) diagnostic has been developed for the National Spherical Tokamak Experiment. The new edge ME-SXR system tested on NSTX consists of a set of vertically stacked diode arrays, each viewing the plasma tangentially through independent pinholes and filters providing an overlapping view of the plasma midplane which allows simultaneous SXR measurements with coarse sub-sampling of the x-ray spectrum. Using computed x-ray spectral emission data, combinations of filters can provide fast (>10 kHz) measurements of changes in the electron temperature and density profiles providing a method to “fill-in” the gaps of the multi-point Thomson scattering system.
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52.55.Fa Tokamaks, spherical tokamaks
52.59.Px Hard X-ray sources
52.70.-m Plasma diagnostic techniques and instrumentation
84.30.Vn Filters

≃10 eV ionization shift in Ir Kα2 from a near-coincident Lu K-edge

N. R. Pereira, B. V. Weber, D. Phipps, J. W. Schumer, J. F. Seely, J. J. Carroll, J. R. VanHoy, K. Słabkowska, and M. Polasik

Rev. Sci. Instrum. 83, 10E110 (2012); http://dx.doi.org/10.1063/1.4731739 (3 pages) | Cited 1 time

Online Publication Date: 9 July 2012

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Close to an x-ray filter's K-edge the transmission depends strongly on the photon energy. For a few atom pairs, the K-edge of one is only a few tens of eV higher than a K-line energy of another, so that a small change in the line's energy becomes a measurable change in intensity behind such a matching filter. Lutetium's K-edge is ≃27 eV above iridium's Kα2 line, ≃63.287 keV for cold Ir. A Lu filter reduces this line's intensity by ≃10 % when it is emitted by a plasma, indicating an ionization shift ΔE ≃ 10±1 eV.
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52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.70.La X-ray and γ-ray measurements

Rest-wavelength fiducials for the ITER core imaging x-ray spectrometer

P. Beiersdorfer, G. V. Brown, A. T. Graf, M. Bitter, K. W. Hill, R. L. Kelley, C. A. Kilbourne, M. A. Leutenegger, and F. S. Porter

Rev. Sci. Instrum. 83, 10E111 (2012); http://dx.doi.org/10.1063/1.4733318 (3 pages) | Cited 1 time

Online Publication Date: 12 July 2012

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Absolute wavelength references are needed to derive the plasma velocities from the Doppler shift of a given line emitted by a moving plasma. We show that such reference standards exist for the strongest x-ray line in neonlike W64+, which has become the line of choice for the ITER (Latin “the way”) core imaging x-ray spectrometer. Close-by standards are the Hf Lβ3 line and the Ir Lα2 line, which bracket the W64+ line by ±30 eV; other standards are given by the Ir Lα1 and Lα2 lines and the Hf Lβ1 and Lβ2 lines, which bracket the W64+ line by ±40 and ±160 eV, respectively. The reference standards can be produced by an x-ray tube built into the ITER spectrometer. We present spectra of the reference lines obtained with an x-ray microcalorimeter and compare them to spectra of the W64+ line obtained both with an x-ray microcalorimeter and a crystal spectrometer.
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07.85.Nc X-ray and γ-ray spectrometers
29.30.Kv X- and γ-ray spectroscopy
07.85.-m X- and γ-ray instruments
07.20.Fw Calorimeters

Transmission crystal x-ray spectrometer covering the 6 keV–18 keV energy range with E/ΔE = 1800 instrumental resolving power

John Seely, Uri Feldman, Charles Brown, Nino Pereira, Lawrence Hudson, Jack Glover, and Eric Silver

Rev. Sci. Instrum. 83, 10E112 (2012); http://dx.doi.org/10.1063/1.4732184 (3 pages) | Cited 1 time

Online Publication Date: 13 July 2012

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A high-resolution x-ray spectrometer utilizing a thin quartz transmission crystal and covering the 6 keV–18 keV energy range has been developed and tested. The spectrometer consists of a cylindrically bent crystal in a vacuum housing. The crystal position and the range of Bragg angles that are incident on the crystal can be adjusted to record an ≈4 keV wide spectrum in the 6 keV–18 keV range. The spectrometer is of the Cauchois type and has a compact linear geometry that is convenient for deployment at laser-produced plasma, EBIT, and other x-ray sources. Test spectra of the W L and Mo K lines from laboratory sources have linewidths as small as 11 eV, approaching the natural widths, and instrumental resolving power as high as 1800. Techniques for enhancing the energy resolution are experimentally demonstrated.
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07.85.Nc X-ray and γ-ray spectrometers
29.30.Kv X- and γ-ray spectroscopy

Measuring electron-positron annihilation radiation from laser plasma interactions

Hui Chen, R. Tommasini, J. Seely, C. I. Szabo, U. Feldman, N. Pereira, G. Gregori, K. Falk, J. Mithen, and C. D. Murphy

Rev. Sci. Instrum. 83, 10E113 (2012); http://dx.doi.org/10.1063/1.4734038 (3 pages)

Online Publication Date: 17 July 2012

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We investigated various diagnostic techniques to measure the 511 keV annihilation radiations. These include step-wedge filters, transmission crystal spectroscopy, single-hit CCD detectors, and streaked scintillating detection. While none of the diagnostics recorded conclusive results, the step-wedge filter that is sensitive to the energy range between 100 keV and 700 keV shows a signal around 500 keV that is clearly departing from a pure Bremsstrahlung spectrum and that we ascribe to annihilation radiation.
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52.38.Kd Laser-plasma acceleration of electrons and ions
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
Author Select

Spectral analysis of x-ray emission created by intense laser irradiation of copper materials

C. M. Huntington, C. C. Kuranz, G. Malamud, R. P. Drake, H.-S. Park, and B. R. Maddox

Rev. Sci. Instrum. 83, 10E114 (2012); http://dx.doi.org/10.1063/1.4732181 (3 pages)

Online Publication Date: 18 July 2012

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We have measured the x-ray emission, primarily from Kα,Kβ, and Heα lines, of elemental copper foil and “foam” targets irradiated with a mid-1016 W/cm2 laser pulse. The copper foam at 0.1 times solid density is observed to produce 50% greater Heα line emission than copper foil, and the measured signal is well-fit by a sum of three synthetic spectra generated by the atomic physics code FLYCHK. Additionally, spectra from both targets reveal characteristic inner shell Kα transitions from hot electron interaction with the bulk copper. However, only the larger-volume foam target produced significant Kβ radiation, confirming a lower bulk temperature in the higher volume sample.
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61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
82.70.Rr Aerosols and foams
32.30.Rj X-ray spectra

Imaging of high-energy x-ray emission from cryogenic thermonuclear fuel implosions on the NIF

T. Ma, N. Izumi, R. Tommasini, D. K. Bradley, P. Bell, C. J. Cerjan, S. Dixit, T. Döppner, O. Jones, J. L. Kline, G. Kyrala, O. L. Landen, S. LePape, A. J. Mackinnon, H.-S. Park, et al.

Rev. Sci. Instrum. 83, 10E115 (2012); http://dx.doi.org/10.1063/1.4733313 (3 pages) | Cited 2 times

Online Publication Date: 18 July 2012

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Accurately assessing and optimizing the implosion performance of inertial confinement fusion capsules is a crucial step to achieving ignition on the NIF. We have applied differential filtering (matched Ross filter pairs) to provide broadband time-integrated absolute x-ray self-emission images of the imploded core of cryogenic layered implosions. This diagnostic measures the temperature- and density-sensitive bremsstrahlung emission and provides estimates of hot spot mass, mix mass, and pressure.
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28.52.Cx Fueling, heating and ignition
52.58.-c Other confinement methods

Dilation x-ray imager a new/faster gated x-ray imager for the NIF

S. R. Nagel, T. J. Hilsabeck, P. M. Bell, D. K. Bradley, M. J. Ayers, M. A. Barrios, B. Felker, R. F. Smith, G. W. Collins, O. S. Jones, J. D. Kilkenny, T. Chung, K. Piston, K. S. Raman, B. Sammuli, et al.

Rev. Sci. Instrum. 83, 10E116 (2012); http://dx.doi.org/10.1063/1.4732849 (3 pages)

Online Publication Date: 19 July 2012

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As the yield on implosion shots increases it is expected that the peak x-ray emission reduces to a duration with a FWHM as short as 20 ps for ∼7 × 1018 neutron yield. However, the temporal resolution of currently used gated x-ray imagers on the NIF is 40–100 ps. We discuss the benefits of the higher temporal resolution for the NIF and present performance measurements for dilation x-ray imager, which utilizes pulse-dilation technology [T. J. Hilsabeck et al., Rev. Sci. Instrum. 81, 10E317 (2010)10.1063/1.3479111] to achieve x-ray imaging with temporal gate times below 10 ps. The measurements were conducted using the COMET laser, which is part of the Jupiter Laser Facility at the Lawrence Livermore National Laboratory.
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07.85.-m X- and γ-ray instruments
42.79.Pw Imaging detectors and sensors
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing

Source geometric considerations for OMEGA Dante measurements

M. J. May, J. R. Patterson, C. Sorce, K. Widmann, K. B. Fournier, and F. Perez

Rev. Sci. Instrum. 83, 10E117 (2012); http://dx.doi.org/10.1063/1.4734041 (3 pages)

Online Publication Date: 25 July 2012

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The Dante is a 15 channel filtered diode array which is installed on the OMEGA laser facility at the Laboratory for Laser Energetics, University of Rochester. The system yields the spectrally and temporally resolved radiation flux from 50 eV to 10 keV from various targets (i.e., Hohlraum, gas pipes, etc.). The absolute flux is determined from the radiometric calibration of the x-ray diodes, filters, and mirrors and an unfold algorithm applied to the recorded voltages from each channel. The unfold algorithm assumes an emitting source that is spatially uniform and has a constant area as a function of photon energy. The emitting x-ray source is usually considered to be the laser entrance hole (LEH) of a given diameter for Hohlraum type targets or the effective wall area of high conversion efficiency K-shell type targets. This assumption can be problematic for several reasons. High intensity regions or “hot spots” in the x-ray are observed where the drive laser beams strike the target. The “hot spots” create non-uniform emission seen by the Dante. Additionally, thinned walled (50 μm) low-Z targets (C22H10N2O5) have an energy dependent source size since the target's walls will be fully opaque for low energies (E < 2–3 keV) yet fully transmissive at higher energies. Determining accurate yields can be challenging for these types of targets. Discussion and some analysis will be presented.
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07.85.-m X- and γ-ray instruments
42.62.-b Laser applications
42.79.Bh Lenses, prisms and mirrors

Methods for characterizing x-ray detectors for use at the National Ignition Facility

S. F. Khan, L. R. Benedetti, D. R. Hargrove, S. M. Glenn, N. Simanovskaia, J. P. Holder, M. A. Barrios, D. Hahn, S. R. Nagel, P. M. Bell, and D. K. Bradley

Rev. Sci. Instrum. 83, 10E118 (2012); http://dx.doi.org/10.1063/1.4733315 (3 pages) | Cited 3 times

Online Publication Date: 26 July 2012

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Gated and streaked x-ray detectors generally require corrections in order to counteract instrumental effects in the data. The method of correcting for gain variations in gated cameras fielded at National Ignition Facility (NIF) is described. Four techniques for characterizing the gated x-ray detectors are described. The current principal method of characterizing x-ray instruments is the production of controlled x-ray emission by laser-generated plasmas as a dedicated shot at the NIF. A recently commissioned pulsed x-ray source has the potential to replace the other characterization systems. This x-ray source features a pulsed power source consisting of a Marx generator, capacitor bank that is charged in series and discharged in parallel, producing up to 300 kV. The pulsed x-ray source initially suffered from a large jitter (∼60 ns), but the recent addition of a pulsed laser to trigger the spark gap has reduced the jitter to ∼5 ns. Initial results show that this tool is a promising alternative to the other flat fielding techniques.
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29.40.-n Radiation detectors
07.85.Fv X- and γ-ray sources, mirrors, gratings, and detectors
52.75.-d Plasma devices
52.80.Mg Arcs; sparks; lightning; atmospheric electricity
07.85.-m X- and γ-ray instruments

South pole bang-time diagnostic on the National Ignition Facility (invited)

D. H. Edgell, D. K. Bradley, E. J. Bond, S. Burns, D. A Callahan, J. Celeste, M. J. Eckart, V. Yu. Glebov, D. S. Hey, G. Lacaille, J. D. Kilkenny, J. Kimbrough, A. J. Mackinnon, J. Magoon, J. Parker, et al.

Rev. Sci. Instrum. 83, 10E119 (2012); http://dx.doi.org/10.1063/1.4731756 (6 pages) | Cited 3 times

Online Publication Date: 30 July 2012

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The south pole bang-time diagnostic views National Ignition Facility (NIF) implosions through the lower Hohlraum laser entrance hole to measure the time of peak x-ray emission (peak compression) in indirect-drive implosions. Five chemical-vapor-deposition diamond photoconductive detectors with different filtrations and sensitivities record the time-varying x rays emitted by the target. Wavelength selecting highly oriented pyrolytic graphite crystal mirror monochromators increase the x-ray signal-to-background ratio by filtering for 11-keV emission. Diagnostic timing and the in situ temporal instrument response function are determined from laser impulse shots on the NIF. After signal deconvolution and background removal, the bang time is determined to 45-ps accuracy. The x-ray “yield” (mJ/sr/keV at 11 keV) is determined from the time integral of the corrected peak signal.
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52.70.La X-ray and γ-ray measurements
07.85.Fv X- and γ-ray sources, mirrors, gratings, and detectors
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)

Absolute determination of charge-coupled device quantum detection efficiency using Si K-edge x-ray absorption fine structure

J. Dunn and A. B. Steel

Rev. Sci. Instrum. 83, 10E120 (2012); http://dx.doi.org/10.1063/1.4738659 (3 pages)

Online Publication Date: 31 July 2012

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We report a method to determine the quantum detection efficiency and the absorbing layers on a front-illuminated charge-coupled device (CCD). The CCD under study, as part of a crystal spectrometer, measures intense continuum x-ray emission from a picosecond laser-produced plasma and spectrally resolves the Si K-edge x-ray absorption fine structure due to the electrode structure of the device. The CCD response across the Si K-edge shows a large discontinuity as well as a number of oscillations that are identified individually and uniquely from Si, SiO2, and Si3N4 layers. From the spectral analysis of the structure and K-edge discontinuity, the active layer thickness and the different absorbing layers thickness can be determined precisely. A precise CCD detection model from 0.2 to 10 keV can be deduced from this highly sensitive technique.
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85.30.Tv Field effect devices
61.05.cj X-ray absorption spectroscopy: EXAFS, NEXAFS, XANES, etc.
78.70.Dm X-ray absorption spectra

Measurement of electron temperature of imploded capsules at the National Ignition Facility

N. Izumi, T. Ma, M. Barrios, L. R. Benedetti, D. Callahan, C. Cerjan, J. Edwards, S. Glenn, S. Glenzer, J. Kilkenny, J. Kline, G. Kyrala, O. L. Landen, S. Regan, P. Springer, et al.

Rev. Sci. Instrum. 83, 10E121 (2012); http://dx.doi.org/10.1063/1.4738660 (3 pages)

Online Publication Date: 31 July 2012

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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.
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52.70.La X-ray and γ-ray measurements
28.52.Lf Components and instrumentation
52.25.-b Plasma properties
52.50.Lp Plasma production and heating by shock waves and compression
52.57.-z Laser inertial confinement

Integrated x-ray reflectivity measurements of elliptically curved pentaerythritol crystals

M. J. Haugh, S. P. Regan, K. D. Jacoby, P. W. Ross, J. Magoon, M. A. Barrios, J. A. Emig, M. J. Shoup, III, and K. B. Fournier

Rev. Sci. Instrum. 83, 10E122 (2012); http://dx.doi.org/10.1063/1.4738748 (3 pages)

Online Publication Date: 31 July 2012

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The elliptically curved pentaerythritol (PET) crystals used in the Supersnout 2 x-ray spectrometer on the National Ignition Facility at Lawrence Livermore National Laboratory have been calibrated photometrically in the range of 5.5–16 keV. The elliptical geometry provides broad spectral coverage and minimizes the degradation of spectral resolution due to the finite source size. The reflectivity curve of the crystals was measured using a x-ray line source. The integrated reflectivity (RI) and width of its curve (ΔΘ) were the measurements of major interest. The former gives the spectrometer throughput, and the latter gives the spectrometer resolving power. Both parameters are found to vary considerably with the radius of curvature of the crystal and with spectral energy. The results are attributed to an enhanced mosaic effect due to the increase in curvature. There are also contributions from the crystal cleaving and gluing processes.
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07.85.Nc X-ray and γ-ray spectrometers

X-ray streak camera cathode development and timing accuracy of the 4ω ultraviolet fiducial system at the National Ignition Facility

Y. P. Opachich, N. Palmer, D. Homoelle, B. Hatch, P. Bell, D. Bradley, D. Kalantar, D. Browning, J. Zuegel, and O. Landen

Rev. Sci. Instrum. 83, 10E123 (2012); http://dx.doi.org/10.1063/1.4732855 (3 pages) | Cited 4 times

Online Publication Date: 2 August 2012

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The convergent ablator experiments at the National Ignition Facility (NIF) are designed to measure the peak velocity and remaining ablator mass of an indirectly driven imploding capsule. Such a measurement can be performed using an x-ray source to backlight the capsule and an x-ray streak camera to record the capsule as it implodes. The ultimate goal of this experiment is to achieve an accuracy of 2% in the velocity measurement, which translates to a ±2 ps temporal accuracy over any 300 ps interval for the streak camera. In order to achieve this, a 4ω (263 nm) temporal fiducial system has been implemented for the x-ray streak camera at NIF. Aluminum, titanium, gold, and silver photocathode materials have been tested. Aluminum showed the highest relative quantum efficiency, with five times more peak signal counts per fiducial pulse when compared to Gold. The fiducial pulse data were analyzed to determine the centroiding statistical accuracy for incident laser pulse energies of 1 and 10 nJ, showing an accuracy of ±1.6 ps and ±0.7 ps, respectively.
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07.85.-m X- and γ-ray instruments
29.40.-n Radiation detectors
85.60.Ha Photomultipliers; phototubes and photocathodes

Neutron field parameter measurements on the JET tokamak by means of super-heated fluid detectors

M. Gherendi, V. L. Zoita, T. Craciunescu, M. Gatu Johnson, A. Pantea, I. Baltog, T. Edlington, C. Hellesen, V. Kiptily, S. Conroy, A. Murari, S. Popovichev, and JET EFDA Contributors

Rev. Sci. Instrum. 83, 10E124 (2012); http://dx.doi.org/10.1063/1.4739410 (3 pages)

Online Publication Date: 2 August 2012

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The neutron field parameters (fluence and energy distribution) at a specific location outside the JET Torus Hall have been measured by means of super-heated fluid detectors (or “bubble detectors”) in combination with an independent, time-of-flight, technique. The bubble detector assemblies were placed at the end of a vertical line of sight at about 16 m from the tokamak mid plane. Spatial distributions of the neutron fluence along the radial and toroidal directions have been obtained using two-dimensional arrays of bubble detectors. Using a set of three bubble detector spectrometers the neutron energy distribution was determined over a broad energy range, from about 10 keV to above 10 MeV, with an energy resolution of about 30% at 2.5 MeV. The very broad energy response allowed for the identification of energy features far from the main fusion component (around 2.45 MeV for deuterium discharges).
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52.55.Fa Tokamaks, spherical tokamaks
52.70.Nc Particle measurements
28.52.Lf Components and instrumentation
29.30.Hs Neutron spectroscopy

Application of spatially resolved high resolution crystal spectrometry to inertial confinement fusion plasmas

K. W. Hill, M. Bitter, L. Delgado-Aparacio, N. A. Pablant, P. Beiersdorfer, M. Schneider, K. Widmann, M. Sanchez del Rio, and L. Zhang

Rev. Sci. Instrum. 83, 10E125 (2012); http://dx.doi.org/10.1063/1.4738651 (3 pages)

Online Publication Date: 3 August 2012

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High resolution (λ/Δλ ∼ 10 000) 1D imaging x-ray spectroscopy using a spherically bent crystal and a 2D hybrid pixel array detector is used world wide for Doppler measurements of ion-temperature and plasma flow-velocity profiles in magnetic confinement fusion plasmas. Meter sized plasmas are diagnosed with cm spatial resolution and 10 ms time resolution. This concept can also be used as a diagnostic of small sources, such as inertial confinement fusion plasmas and targets on x-ray light source beam lines, with spatial resolution of micrometers, as demonstrated by laboratory experiments using a 250-μm 55Fe source, and by ray-tracing calculations. Throughput calculations agree with measurements, and predict detector counts in the range 10−8–10−6 times source x-rays, depending on crystal reflectivity and spectrometer geometry. Results of the lab demonstrations, application of the technique to the National Ignition Facility (NIF), and predictions of performance on NIF will be presented.
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52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.27.Lw Dusty or complex plasmas; plasma crystals
52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
52.70.La X-ray and γ-ray measurements
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