Bulletin of the American Physical Society
56th Annual Meeting of the APS Division of Plasma Physics
Volume 59, Number 15
Monday–Friday, October 27–31, 2014; New Orleans, Louisiana
Session NO7: Laser-driven X-ray Sources and Diagnostic Techniques |
Hide Abstracts |
Chair: Riccardo Tommasini, Lawrence Livermore National Laboratory Room: Galerie 6 |
Wednesday, October 29, 2014 9:30AM - 9:42AM |
NO7.00001: Laser-driven heat-front propagation in foam vs. gas F. P\'erez, J.D. Colvin, M.J. May, S.A. Gammon, K.B. Fournier A high-energy laser (several kJ, $10^{15}$~W/cm$^2$) can propagate inside an underdense plasma over millimeters, along its associated heat front. This creates a large volume of hot plasma (several keV) able to produce bright hard-x-ray sources when a high-Z dopant is included in the material. In the past years, we investigated the behavior of both gases and foams under these circumstances. Their design and predictability relies on the understanding of the heat front propagation. In the case of foams, several studies tried to assess the effect of their micro-structure in altering the laser interaction and the heat front propagation, but no experimental data has shown clear evidence. We present here the design and results of a recent experiment, using the OMEGA laser, where a Ge-doped silica foam was compared to a Ne/Kr gas of very similar characteristics, the only difference between these two materials being their micro-structure to allow for a straightforward determination of its influence. The design of future similar experiments will also be reported. J. Colvin presents theoretical and modeling aspects of this subject in a companion presentation. [Preview Abstract] |
Wednesday, October 29, 2014 9:42AM - 9:54AM |
NO7.00002: Does laser-driven heat front propagation depend on material microstructure? J.D. Colvin, F. P\'erez, K.B. Fournier, M.J. May, T.E. Felter, M. Bagge-Hansen, S. Kucheyev We showed earlier that the laser-driven heat front propagation velocity in low-density Ti-silica aerogel and TiO$_{2}$ foam targets was slower than that simulated with a 2D radiation-hydrodynamics code incorporating an atomic kinetics model in non-LTE and assuming initially homogeneous material (F. P\'{e}rez, et al., Physics of Plasmas 21, 023102, 2014). Some theoretical models suggest that the heat front is slowed over what it would be in a homogeneous medium by the microstructure of the foam. In more recent experiments with Cu-loaded carbon nanotube foam, however, we find the opposite behavior; that is, the simulations under-predict the measured heat-front velocity. We present details of the Cu foam experiments and comparisons with simulations, and then discuss implications for models of heat-front slowing in foams of a more-recent gas vs. foam comparison experiment. F. P\'{e}rez presents the design and results of this comparison experiment in a companion presentation. [Preview Abstract] |
Wednesday, October 29, 2014 9:54AM - 10:06AM |
NO7.00003: Simulation study of optimizing the 3-5 keV x-ray emission from pure Ar K-shell vs. Ag L-shell targets on the National Ignition Facility G.E. Kemp, J.D. Colvin, K.B. Fournier, M.V. Patel, H.A. Scott, M. Marinak, J.H. Fisher, J.F. Davis High-flux x-ray sources are desirable for testing the radiation hardness of materials used in various civilian, space and military applications. For this study, there is an interest to design a source with primarily mid-energy ($\sim 3\,keV$) but limited soft ($< 1\,keV$) x-ray contributions; we focus on optimizing the $3-5\,keV$ non-LTE emission from targets consisting of pure Ar (K-shell) or Ag (L-shell) at sub-critical densities ($\sim n_c/10$) to ensure supersonic, volumetric laser heating with minimal losses to kinetic energy and thermal x rays. However, K and L-shell sources are expected to optimize at different temperatures and densities and it is \emph{a priori} unclear under what target and laser conditions this will occur. Using \textsc{Hydra}, a multi-dimensional, arbitrary Lagrangian-Eulerian, radiation-hydrodynamics code, we performed a simulation study by varying initial target density and laser parameters for each material as it would perform on the National Ignition Facility (NIF). We employ a model, benchmarked against Kr data collected on the NIF, that uses flux-limited Lee-More thermal conductivity and implicit Monte-Carlo photonics with non-LTE, detailed configuration accounting opacities from \textsc{Cretin}. [Preview Abstract] |
Wednesday, October 29, 2014 10:06AM - 10:18AM |
NO7.00004: Development and Characterization of a 16.3 keV X-Ray Source at the National Ignition Facility K.B. Fournier, M.A. Barrios, M.B. Schneider, S. Khan, H. Chen, F. Coppari, R. Rygg, M. Hohenberger, F. Albert, J. Moody, J. Ralph, G.E. Kemp, S.P. Regan X-ray sources at the National Ignition Facility are needed for radiography of in-flight capsules in inertial confinement fusion experiments and for diffraction studies of materials at high pressures. In the former case, we want to optimize signal to noise and signal over background ratios for the radiograph, in the latter case, we want to minimize high-energy emission from the backlighter that creates background on the diffraction data. Four interleaved shots at NIF were taken in one day, with laser irradiances on a Zr backlighter target ranging from 5 to 14 x 10$^{15}$ W/cm$^2$. Two shots were for source optimization as a function of laser irradiance. X-ray fluxes were measured with the time-resolved NIF X-ray Spectrometer (NXS) and the DANTE array of calibrated, filtered diodes. Two shots were optimized to make backscatter measurements with the FABS and NBI optical power systems. The backscatter levels are investigated to look for correlation with hot electron populations inferred from high-energy x rays measured with the FFLEX broadband spectrometer. Results from all shots are presented and compared with models. Work performed under the auspices of the U.S. DOE by LLNL under Contract No. DE-AC52-07NA27344. [Preview Abstract] |
Wednesday, October 29, 2014 10:18AM - 10:30AM |
NO7.00005: Diagnosing Te of NIF plasmas using the isoelectronic ratios of microdot tracer elements M.A. Barrios, S.P. Regan, K.B. Fournier, M.B. Schneider, D.A. Liedahl, G.E. Kemp, J.D. Moody, G.V. Brown, H. Chen, O. Landen, D. Bradley, O. Jones, R. Epstein Experiments planned on NIF will diagnose the electron temperature (T$_{\mathrm{e}})$ of the hohlraum in the vicinity of the laser entrance hole (LEH) using x-ray spectroscopy. A microdot consisting of Ti and Cr will be coated on the surface of a CH implosion capsule and centered on the symmetry axis of the hohlraum. As the microdot is ablated it is ionized by the hohlraum plasma and flows into the LEH region. The experimental plan to use the isoelectronic line ratio technique [R.S. Majoribanks, \textit{et al}. Phys. Rev. A 46(4), 1992.] to diagnose T$_{\mathrm{e}}$ of the hohlraum plasma near the LEH will be presented. Exploratory experiments at NIF tested the T$_{\mathrm{e}}$ sensitivity of the technique by recording time resolved K-shell emission of direct-drive spherical targets coated with a CrNiZn alloy. Application of the isoelectronic technique to the coronal plasma of these targets will be presented. This work was performed under the auspices of the U.S. Department of Energy by LLNL under Contract DE-AC52-07NA27344. [Preview Abstract] |
Wednesday, October 29, 2014 10:30AM - 10:42AM |
NO7.00006: Development of backlit thin shells and foam balls on the NIF for diagnosing shape swings during the foot pulse Gareth Hall, Peter Amendt, Otto Landen, Andrea Kritcher, David Bradley, Richard Town The performance of indirect-drive ICF capsules is extremely sensitive to low-mode P2 and P4 asymmetries during the foot of the pulse, the trough in particular.\footnote{A. L. Kritcher et al, Phys. Plasmas 21, 042708-1 (2014)} These asymmetries can cause non-radial velocity and density distortions that cannot be corrected later in the implosion, significantly degrading fusion yield. X-ray radiography of thin-shell capsules\footnote{R. K. Kirkwood et al, Phys. Plasmas 16, 012702 (2009)} and foam balls\footnote{P. Amendt et al, Phys. Rev. Lett. 77, 3815 (1996)} has been demonstrated as a means of diagnosing foot asymmetries on the OMEGA and NOVA lasers. The design and implementation of these techniques for upcoming experiments on the NIF will be discussed. In these experiments, the target will be driven using only a picket and trough pulse, and x-ray radiography used to measure asymmetries that develop during implosion. (IM: LLNL-ABS-657009) [Preview Abstract] |
Wednesday, October 29, 2014 10:42AM - 10:54AM |
NO7.00007: Experiments on OMEGA EP to study the material dependence of the two-plasmon decay instability J.R. Fein, P.A. Keiter, D.H. Froula, D.H. Edgell, P.X. Belancourt, J.P. Holloway, R.P. Drake For long-scale-length plasmas, two-plasmon decay (TPD) is a major LPI responsible for generating hot electrons ($>$10 keV). Hot electrons can present unintended effects, such as preheating the target and producing hard x-ray background that can interfere with diagnostics. Understanding hot electron production in laser-produced plasmas is important to control and mitigate these effects. TPD growth is limited by plasma collisionality hydrodynamics, which depend on plasma material Z. It has been predicted and demonstrated by preliminary experiments that hot electron production can be mitigated through varying these parameters, by increasing plasma Z [1,2]. We have performed experiments on OMEGA EP to thoroughly study the Z-dependence of the TPD instability, through varying the material with which the lasers interact. Hard x-ray diagnostics were used to measure hot electron production and optical diagnostics were used to measure the plasma density profile for each material. Preliminary results will be presented, showing how hot electron production and electron density scale lengths scale with Z.\\[4pt] [1] D. T. Michel, \textit{Physical Review Letters}, 109(15), 155007 (2012).\\[0pt] [2] S. X. Hu, et al. \textit{Physics of Plasmas}, 20(3), 032704 (2013). [Preview Abstract] |
Wednesday, October 29, 2014 10:54AM - 11:06AM |
NO7.00008: Testing Talbot--Lau X-Ray Moir\'{e} Fringe Deflectometry with a Laser Backlighter D. Stutman, M.P. Valdivia, M. Finkenthal, S.P. Regan, C. Stoeckl, B. Stoeckl Moir\'{e} fringe deflectometry is a simple and robust density diagnostic method, based on light refraction caused by electron density gradients. The Talbot-Lau (TL) grating interferometer could make it possible to apply this method for density diagnostics in high-energy-density plasmas using hard x rays from conventional backlighters. When compared to conventional radiography, the TL interferometer offers more sensitivity to refraction and is therefore less dependent on modeling. We adapted the TL interferometer to the high-energy-density-physics requirements by extending its operation to high magnification, 8 to 17 keV x-ray energy, and single-shot phase retrieval. The next step of development is to test its operation close to a high power laser backlighter. We designed an experiment on the Multi-Terawatt laser aimed at studying grating survival as a function of distance from the backlighter as well as demonstrating Moir\'{e} fringe production with 8-keV x rays. The possibility of directly using a microperiodic backlighter instead of a ``source'' grating is also discussed. [Preview Abstract] |
Wednesday, October 29, 2014 11:06AM - 11:18AM |
NO7.00009: Measurements of the betatron spectrum around the Kedge of thin foils Keegan Behm, Tony Zhao, Jonathon Woods, Jason Cole, Anatoly Maksimchuk, Victor Yanovsky, Alexander Thomas, Karl Krushelnick, Stuart Mangles Presented here are single shot and integrated Xray spectroscopy measurements of the betatron radiation spectrum produced from a laser wakefield accelerator (LWFA) using both single photon counting and different crystals. We measure critical energy and total flux of the betatron spectrum for various parameters in addition to absorption of the spectrum around the Kedge of different thin metal foils with high spectral resolution using curved and flat HOPG and Mica crystals. [Preview Abstract] |
Wednesday, October 29, 2014 11:18AM - 11:30AM |
NO7.00010: Demonstration of x-ray fluorescence imaging to diagnose high-energy-density plasmas M.J. MacDonald, P.A. Keiter, D.S. Montgomery, M.M. Biener, J.R. Fein, K.B. Fournier, E.J. Gamboa, S.R. Klein, C.C. Kuranz, H.J. LeFevre, M.J.-E. Manuel, J. Streit, W.C. Wan, R.P. Drake X-ray diagnostic techniques are widely used to diagnose high-energy-density experiments. Radiography is used to create 2D images of plasma density using the relative transmission of the source x-rays, but the path-integrated nature of this process limits its usefulness when diagnosing large-volume or geometrically-complex targets. A technique capable of measuring local conditions is required to characterize plasmas in these geometries. Here we describe an x-ray fluorescence imaging (XRFI) diagnostic that uses a collimated probe beam to sample a small portion of the system [1]. The x-ray fluorescence induced in the probed region was used to calculate material density, shock velocity, and temperature simultaneously using an imaging x-ray spectrometer. Data from recent experiments performed at the Trident laser facility at Los Alamos National Lab will be presented. *This work is funded by the NNSA-DS and SC-OFES Joint Program in HED Laboratory Plasmas, grant number DE-NA0001840 and supported by the NSF GRFP Grant No. 2013155705. \\[4pt] [1] L.J. Suter et al. Rev. Sci. Inst. 70, 663 (1999), N.E. Lanier et al. Rev. Sci. Inst. 74, 2169 (2003). [Preview Abstract] |
Wednesday, October 29, 2014 11:30AM - 11:42AM |
NO7.00011: Experimental Generation of Backward-Propagating MeV Electrons in Ultra-Intense Laser Interactions Scott Feister, John T. Morrison, Vladimir M. Ovchinnikov, Kyle D. Frische, John A. Nees, Chris Orban, Enam A. Chowdhury, W. Melvyn Roquemore Electron beams with peak energies exceeding 1 MeV have been produced with kHz repetition by the interaction of normally-incident, intensely-focused ($10^{18} W/cm^2$), 30 fs duration laser pulses with water-jet targets. A high-charge electron beam has been produced in the direction opposite laser propagation. Through interaction with aluminum in the parabolic focusing optic, this backward-going beam creates a $\sim$ 1 rem/hr secondary X-ray source with $>$ 800 keV peak spectral power density. A standing wave acceleration mechanism, originally identified for its relevance to forward-going electrons, acts to inject electrons into the reflected light where additional acceleration occurs. Experimental X-ray yield is drastically reduced when laser pre-pulse at nanosecond level is suppressed, which is corroborated by simulations showing similar reduction in accelerated electron energies and quantity in the absence of pre-plasma scale length. [Preview Abstract] |
Wednesday, October 29, 2014 11:42AM - 11:54AM |
NO7.00012: Compact tunable Compton x-ray source from laser wakefield accelerator and plasma mirror Hai-En Tsai, Xiaoming Wang, Joseph Shaw, Zhengyan Li, Rafal Zgadzaj, Alex Arefiev, Mike Downer Compton backscatter (CBS) x-rays have been generated from laser wakefield accelerator (LWFA) electron beams by retro-reflecting the LWFA drive pulse with a plasma mirror (PM) [1] and by backscattering a secondary pulse split from the driver pulse [2]. However, tunable quasi-monoenergetic CBS x-rays have been produced only by the latter method, which requires challenging alignment. Here we demonstrate quasi-monoenergetic ($\sim$ 50{\%} FWHM), bright (5 x 10$^{6}$ photon per shot) CBS x-rays with central energy tunability from 75 KeV to 200 KeV by combining a PM with a tunable LWFA. 30 TW, 30-fs (FWHM), laser pulses from the UT$^{3}$ laser system were focused (f/12) to spot diameter 11 micron, intensity $\sim$ 6x10$^{18}$ W/cm$^{2}$ (a$=$1.5) at a 1-mm long Helium gas jet, yielding quasi-monoenergetic relativistic electrons. A thin plastic film near the gas jet exit efficiently retro-reflected the LWFA driving pulse into oncoming electrons to produce CBS x-rays without detecting bremsstrahlung background. By changing gas jet backing pressure, electron energy was tuned from 60 to 90 MeV, thereby tuning the CBS x-ray energy, which was determined by measuring transmission through a metal filter pack. The x-ray beam profiles recorded on an image plate had 5-10-mrad divergence. \\[4pt] [1] K. Ta Phuoc \textit{et al}., \textit{Nature Photonics} \textbf{6}, 308 (2012).\\[0pt] [2] N.D. Power et al., \textit{Nature Photonics }\textbf{8}, 28--31(2014). [Preview Abstract] |
Wednesday, October 29, 2014 11:54AM - 12:06PM |
NO7.00013: Ultra-Bright X/$\gamma $ Rays from Laser-Wire Target Interaction Tong-Pu Yu, Yan Yin, Fu-Qiu Shao, Alexander Pukhov With the rapid development of laser facilities around the word, table-top X/$\gamma $ rays source based on laser plasma interaction becomes more and more important since its potential applications in medicine, science, and engineering. By using three-dimensional particle-in-cell simulations with radiation reaction effect incorporated, we study the dynamics of intense laser wire target interaction. When a circularly polarized laser pulse at an intensity of 10$^{21}$W/cm$^2$ irradiates a solid wire target with a transverse radius of 1.0 micrometers and a longitudinal length of 7 micrometers, electrons dragged out from the skin-length oscillate in the circularly polarized laser field transversely and are accelerated by the ponderomotive force in the forward direction. The electrons beyond the skin-length in the target reflux and move in the opposite direction to the laser propagation, providing a large amount of electrons for transverse oscillation. Finally, ultra-bright femtosecond-class synchrotron-like X/$\gamma $ rays with a cut-off photon energy of about 10MeV are emitted in a very small cone angle, which may diverse applications in future. [Preview Abstract] |
Wednesday, October 29, 2014 12:06PM - 12:18PM |
NO7.00014: Experimental results from NIF radiography shots on HDC ablator capsules with and without Tungsten dopant Shahab Khan, Niko Izumi, Pravesh Patel, Andrew MacPhee, Tammy Ma, Charlie Cerjan, Richard Town, David Bradley The electron temperature (T$_{\mathrm{e}})$ of the hot spot within the core of imploded inertial confinement fusion capsules is an effective indicator of implosion performance. A temporally resolved measurement of T$_{\mathrm{e}}$ helps elucidate the mechanisms for hot spot heating and cooling such as alpha-heating and mix. Additionally, comparison with simulations will aid in tuning models to effectively predict implosion performance. The Streaked Polar Instrumentation for Diagnosing Energetic Radiation (SPIDER) is an x-ray streak camera designed to record the x-ray burn history during the stagnation phase. SPIDER accurately reports bang time and burn duration of implosions on the National Ignition Facility (NIF). The addition of several filters of specific materials and thicknesses spread across the spatial axis of the streak camera imager allows for a least square fit of the signal through these filters to a bremsstrahlung hot spot model. The fitted parameters of the model are the T$_{\mathrm{e}}$, opacity, and X-ray yield which is valuable for ablator mix estimates. The details of this calculation and results from several shots on NIF are presented. [Preview Abstract] |
Wednesday, October 29, 2014 12:18PM - 12:30PM |
NO7.00015: Analysis of X-ray Spectra of High-Z Elements obtained on Nike with high spectral and spatial resolution Yefim Aglitskiy, J.L. Weaver, M. Karasik, V. Serlin, S.P. Obenschain, Yu. Ralchenko The spectra of multi-charged ions of Hf, Ta, W, Pt, Au and Bi have been studied on Nike krypton-fluoride laser facility with the help of two kinds of X-ray spectrometers. First, survey instrument covering a spectral range from 0.5 to 19.5 angstroms which allows simultaneous observation of both M- and N- spectra of above mentioned elements with high spectral resolution. Second, an imaging spectrometer with interchangeable spherically bent Quartz crystals that added higher efficiency, higher spectral resolution and high spatial resolution to the qualities of the former one. Multiple spectral lines with X-ray energies as high as 4 keV that belong to the isoelectronic sequences of Fe, Co, Ni, Cu and Zn were identified with the help of NOMAD package developed by Dr. Yu. Ralchenko and colleagues. In our continuous effort to support DOE-NNSA's inertial fusion program, this campaign covered a wide range of plasma conditions that result in production of relatively energetic X-rays. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700