Omega Dante soft x-ray power diagnostic component calibration at the National Synchrotron Light Source

Campbell, Kelly; Weber, F.; Dewald, E. L.; Glenzer, S. H.; Landen, O. L.; Turner, R. E.; Waide, P. A.

doi:10.1063/1.1789603

Cited by 75 publications

(28 citation statements)

References 3 publications

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“…Dante is a collection of absolutely calibrated vacuum x-ray diodes (XRD) filtered individually with edge filters and mirrors for different soft x-ray energy ranges up to 12 keV. The overall error in absolute flux measurement using Dante is estimated to be smaller than ±7 % and is attributed to the calibration of the x-ray diodes, mirrors and filters [15]. However, the relative error that is important for back to back comparison of the conversion efficiencies for the different materials is considerably smaller than the absolute error, 1-2% for radiation temperatures of 250 eV.…”

Section: Introductionmentioning

confidence: 99%

X-ray conversion efficiency of high-Z hohlraum wall materials for indirect drive ignition

et al. 2008

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We measure the conversion efficiency of 351 nm laser light to soft x-rays (0.1-5 keV) for Au, U and high Z mixtures "cocktails" used for hohlraum wall materials in indirect drive ICF. We use spherical targets in a direct drive geometry, flattop laser pulses and laser smoothing with phase plates to achieve constant and uniform laser intensities of 10 14 and 10 15 W/cm 2 over the target surface that are relevant for the future ignition experiments on NIF. The absolute time and spectrally-resolved radiation flux is measured with a multichannel soft x-ray power diagnostic. The conversion efficiency is then calculated by dividing the measured x-ray power by the incident laser power from which the measured laser backscattering losses is subtracted. After ~0.5 ns, the time resolved x-ray conversion efficiency reaches a slowly increasing plateau of 95% at 10 14 W/cm 2 laser intensity and of 80% at 10 15 W/cm 2 . The M-band flux (2-5 keV) is negligible at 10 14 W/cm 2 reaching ~1% of the total x-ray flux for all target materials. In contrast, the Mband flux is significant and depends on the target material at 10 15 W/cm 2 laser intensity, reaching values between 10% of the total flux for U and 27% for Au. Our LASNEX simulations show good agreement in conversion efficiency and radiated spectra with data when using XSN atomic physics model and a flux limiter of 0.15, but they underestimate the generated M-band flux. I IntroductionIn indirect drive inertial confinement fusion (ICF) experiments, intense laser or charged particle beams heat the interior of high-Z cylindrical cavities called hohlraums to efficiently generate soft x-rays. The role of the soft x-rays is to uniformly produce an ablation drive that compresses the DT filled capsule placed inside the hohlraum, driving it to ignition and burn [1]. Due to the relaxed requirements on laser-beam uniformity and reduced sensitivity to hydrodynamic instabilities the indirect drive scenario is the main approach for future ignition experiments at the National Ignition Facility (NIF) [2,3,4]. In such a hohlraum containing a capsule and heated by laser beams the power balance is given by [5,6]:η CE (P laser -P backscatter ) = P walls +P LEH + P capsule =σT R 4 [(1-α)A wall +A LEH +f capsule A capsule ] (1) where η CE is the laser conversion efficiency into soft x-rays (<2 keV), P laser is the incident laser power, P backscatter is the backscattered light by parametric laser-plasma instabilities, P capsule is the radiation absorbed by the capsule, P LEH is the radiation escaping through the hohlraum laser entrance holes (LEH) and P walls is the radiation loss in the hohlraum walls.Furthermore, σ is the Stefan-Boltzmann constant, T R is the hohlraum radiation temperature (≤300 eV), α is the x-ray albedo of the hohlraum wall [7], defined as the ratio between the re-emitted and incident soft x-ray flux at the hohlraum wall, A wall and A LEH are the areas of the hohlraum wall and LEH's, f capsule is the fraction of incident x-ray flux that is absorbed by the capsule and A ...

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Section: Introductionmentioning

confidence: 99%

X-ray conversion efficiency of high-Z hohlraum wall materials for indirect drive ignition

et al. 2008

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“…At the Omega Laser Facility, 1 these measurements are performed with Lawrence Livermore National Laboratory's ͑LLNL͒ soft x-ray spectrometer Dante 2 and photoconductive detectors ͑PCDs͒, 3,4 and the French Atomic Energy Commission's ͑CEA͒ DMX. 5 In its initial Omega configuration, 6 Dante offered 11 x-ray filter edge defined, low energy channels ͑Ͻ2 keV͒ with an additional detector covering a higher energy bandpass ͑2-5 keV͒ used primarily to correct for the high energy component present in the response of the soft channels. With current experiments being performed to investigate higher radiation temperatures relevant for ignition Hohlraums 7 on the National Ignition Facility ͑NIF͒, 8 the capability to quantitatively diagnose timedependent x-ray fluxes at higher energies, including the Au M and L bands, is required.…”

Section: Introductionmentioning

confidence: 99%

“…In the past, components were calibrated using two beamlines, UC3 and X8A, at BNL's National Synchrotron Light Source providing energy coverage up to 6 keV. 6 Incorporating a third higher energy beamline, X15A, provides additional coverage from 5 to 20 keV allowing the Dante spectral envelope to be expanded.…”

Section: Introductionmentioning

confidence: 99%

Soft x-ray power diagnostic improvements at the Omega Laser Facility

Sorce

Schein

Weber

et al. 2006

Review of Scientific Instruments

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Soft x-ray power diagnostics are essential for evaluating high temperature laser plasma experiments. The Dante soft x-ray spectrometer, a core diagnostic for radiation flux and temperature measurements of Hohlraums, installed on the Omega Laser Facility at the Laboratory for Laser Energetics has recently undergone a series of upgrades. Work performed at Brookhaven National Laboratory for the development of the National Ignition Facility (NIF) Dante spectrometer enables the Omega Dante to offer a total of 18 absolutely calibrated channels in the energy range from 50eVto20keV. This feature provides Dante with the capability to measure higher, NIF relevant, radiation temperatures with increased accuracy including a differentiation of higher energy radiation such as the Au M and L bands. Diagnostic monitoring using experimental data from directly driven Au spherical shots is discussed.

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“…One of the most common methods of measuring the radiation flux emitted by the hohlraum along a unique line of sight is with a multichannel x-ray diode ͑XRD͒ array. 2 In most cases, these flux measurements adequately constrain the amount of energy within the hohlraum; however, diagnosis of energy that escapes diagnostic holes and apertures can be difficult.…”

Section: Introductionmentioning

confidence: 99%

Blast wave energy diagnostic

Tierney

Idzorek

et al. 2008

Review of Scientific Instruments

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The distance radiation waves that supersonically propagate in optically thick, diffusive media are energy sensitive. A blast wave can form in a material when the initially diffusive, supersonic radiation wave becomes transonic. Under specific conditions, the blast wave is visible with radiography as a density perturbation. [Peterson et al., Phys. Plasmas 13, 056901 (2006)] showed that the time-integrated drive energy can be measured using blast wave positions with uncertainties less than 10% at the Z Facility. In some cases, direct measurements of energy loss through diagnostic holes are not possible with bolometric and x-ray radiometric diagnostics. Thus, radiography of high compression blast waves can serve as a complementary technique that provides time-integrated energy loss through apertures. In this paper, we use blast waves to characterize the energy emerging through a 2.4 mm aperture and show experimental results in comparison to simulations.

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Omega Dante soft x-ray power diagnostic component calibration at the National Synchrotron Light Source

Cited by 75 publications

References 3 publications

X-ray conversion efficiency of high-Z hohlraum wall materials for indirect drive ignition

X-ray conversion efficiency of high-Z hohlraum wall materials for indirect drive ignition

Soft x-ray power diagnostic improvements at the Omega Laser Facility

Blast wave energy diagnostic

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