Bulletin of the American Physical Society
50th Annual Meeting of the Division of Plasma Physics
Volume 53, Number 14
Monday–Friday, November 17–21, 2008; Dallas, Texas
Session UO3: Diagnostics and Target Fabrication |
Hide Abstracts |
Chair: Christina Back, General Atomics Room: Reunion A |
Thursday, November 20, 2008 2:00PM - 2:12PM |
UO3.00001: First Tests of a Bubble Chamber for Neutron Detection on OMEGA M.C. Ghilea, D.D. Meyerhofer, T.C. Sangster, D.J. Lonobile, R.A. Lerche, L. Disdier A high-spatial detector was developed and tested at LLE to provide additional line-of-sight options for neutron imaging at ICF facilities. The detector is based on a high-pressure, freon-115 bubble chamber with an expansion mechanism controlled by a linear motor. A CCD camera is used to photograph the neutron-induced bubbles in parallel, monochromatic light, while a Schlieren disk is used to enhance the contrast of the image. Imaging when bubble diameters are about 100 \textit{$\mu $}m in diameter potentially offers a several-fold increase in spatial resolution relative to the conventional pixilated scintillator arrays. Test neutron images have been acquired on OMEGA. Flat-field and edge images have been obtained to estimate the resolution of the instrument. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement DE-FC52-08NA28302. [Preview Abstract] |
Thursday, November 20, 2008 2:12PM - 2:24PM |
UO3.00002: Operating Neutron Diagnostics in a High-Intensity Laser Environment V.Yu. Glebov, C. Stoeckl, T.C. Sangster, M. Cruz, T. Duffy, S. Roberts The OMEGA Extended Performance (EP) Laser System was completed in April 2008 as a significant enhancement of the 60-beam, 30-kJ OMEGA Laser Facility at the University of Rochester's Laboratory for Laser Energetics. OMEGA EP is designed to deliver two high-energy petawatt laser beams into the OMEGA target chamber for backlighting and integrated fast-ignitor experiments. The high-intensity laser beams produce a large amount of hard x rays and an electromagnetic pulse (EMP) background that makes operating the neutron diagnostics very challenging. This talk will describe operating the OMEGA neutron diagnostics in a high-intensity laser environment, including neutron temporal diagnostics, neutron bang time detectors, and neutron time-of-flight diagnostics. Development of a new neutron diagnostic specially designed for a high-intensity laser environment will be also presented. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC52-08NA28302. [Preview Abstract] |
Thursday, November 20, 2008 2:24PM - 2:36PM |
UO3.00003: First measurements of the down-scattered and primary neutron spectrum using the Magnetic Recoil Spectrometer (MRS) at OMEGA Johan Frenje, D. Casey, C. Li, J. Rygg, F.H. Seguin, R. Petrasso, V. Glebov, T.C. Sangster, D. Meyerhofer, K. Fletcher A new type of neutron spectrometer, called a Magnetic Recoil Spectrometer (MRS), has been built and activated at OMEGA for measurements of the absolute neutron spectrum in the range 6 to 28 MeV, from which $\rho $R, T$_{i }$, and Y$_{n}$ can be determined. The entire spectrum is measured simultaneously, so the different types of information from the low-energy part (downscattered neutrons), the central part (primary neutrons), and the high-energy part (tertiary neutrons) are available for their critical diagnostic use. Results from the first measurements of the absolute spectrum of down-scattered and primary neutrons will be presented. Measuring $\rho $R at the National Ignition Facility (NIF) will be essential for assessing implosion performance during all stages of development, from surrogate implosions to cryogenic fizzles and to ignited implosions. To accomplish this, we are also developing an MRS for the NIF. As the optimal design of the NIF MRS depends on the resulting neutron data and the experience gained at OMEGA, an overview of the OMEGA MRS R{\&}D experience will also be presented. This work was supported in part by DOE, LLE and LLNL. [Preview Abstract] |
Thursday, November 20, 2008 2:36PM - 2:48PM |
UO3.00004: Partially-space-integrated spectra from spectrally-resolved core image data Taisuke Nagayama, R.C. Mancini, R. Florido, R. Tommasini, J.A. Koch, J. Delettrez, S. Regan, V. Smalyuk Partially-space-integrated spectra (PSIS) can be extracted from spectrally-resolved core image data recorded in implosion experiments using a gated multi-monochromatic x-ray imager (MMI). To this end, a portion of the core image is selected and spatially-integrated across the array of core images recorded by MMI. The result is a time-resolved spectrum spatially-integrated only over the selected portion of the core image, i.e. a spatially-resolved spectrum. A set of PSIS covering different regions of the core image can thus be used to study the spatial profiles of temperature and density in the core. We illustrate the application of this technique to direct-drive implosions at OMEGA that employed deuterium-filled plastic shells with a tracer amount of argon for spectroscopic diagnostics. [Preview Abstract] |
Thursday, November 20, 2008 2:48PM - 3:00PM |
UO3.00005: Developments and fabrication of laser targets used to prepare inertial confinement fusion (ICF) experiments on CEA Laser ``M\'{e}gajoule'' (LMJ) facility Sophie Bednarczyk, Fr\'ed\'eric Durut, Beno\^It Reneaume, Marc Th\'eobald, Alexis Casner, V\'eronique Tassin, Marie-Christine Monteil, Didier Galmich A micro materials and technologies research program has started in France since 10 years to develop a very complex cryogenic target to reach the combustion of a deuterium tritium mixture, by indirect drive on the CEA Laser ``M\'{e}gajoule'' (LMJ) facility. This mixture is contained by an amorphous hydrogenated carbon (a-C:H or CHx) doped with germanium capsule placed in the center of a hohlraum. This research program involves CEA scientists, engineers and technicians united to realize specific targets for carrying out laser plasma experiments on the CEA LIL ``Ligne d'Int\'{e}gration Laser'' or OMEGA-UPGRADE facilities. To achieve the production of such specific targets different technologies are successively used (coating, precision machining, laser machining, characterizations, assembling, etc{\ldots}). This article presents an illustration of these microtechnology realizations through particular complex laser targets for hydrodynamic, or parametric instabilities studies and for symmetry experimental effects studies on fusion burn. [Preview Abstract] |
Thursday, November 20, 2008 3:00PM - 3:12PM |
UO3.00006: Laser ``M\'{e}gajoule'' cryogenic target program: from target fabrication to conformation of the deuterium-tritium ice layer R\'emy Collier, Fr\'ed\'eric Durut, Beno\^It Reneaume, C\'edric Chicane, Marc Th\'eobald, Olivier Breton, Michel Martin, Emmanuel Fleury, Olivier Vincent-Viry, Franck Bachelet, Laurent Jeannot, Isabelle Geoffray, Ronan Botrel, Christophe Dauteuil, Cyril Hermerel, Alexandre Choux, Sophie Bednarczyk, Olivier Legaie For the French inertial confinement fusion (ICF) experiments, cryogenic target assemblies (CTAs) for the LMJ program are manufactured and filled at CEA Valduc (Dijon) in the cryogenic targets filling station (IRCC). They will be moved at about 20 K into a transport cryostat for cryogenic targets and will be driven from CEA/Valduc to CEA/CESTA (Bordeaux). Cryogenic targets will then be transferred by several cryogenic grippers on the cryogenic target positioner before shots. The CTA has to meet severe specifications and involves a lot of challenging tasks for its manufacture. To fill CTAs by permeation with deuterium-tritium (DT), the IRCC need to meet strict thermal, mechanical and dimensional specifications. To obtain a good combustion yield, a very homogenous DT ice layer and very smooth roughness at 1.5 K below the DT triple point are also required. This paper deals with the up to date main issues in the different fields of the LMJ cryogenic target program. [Preview Abstract] |
Thursday, November 20, 2008 3:12PM - 3:24PM |
UO3.00007: Quantitative Dopant/Impurity Analysis for ICF Targets Haibo Huang, Abbas Nikroo, Richard Stephens, Samual Eddinger, Hongwei Xu, K.C. Chen, Kari Moreno We developed a number of new or improved metrology techniques to measure the spatial distributions of multiple elements in ICF ablator capsules to tight NIF specifications (0.5$\pm $0.1 at{\%} Cu, 0.25$\pm $0.10 at{\%} Ar, 0.4$\pm $0.4 at{\%} O). The elements are either the graded dopants for shock timing, such as Cu in Be, or process-induced impurities, such as Ar and O. Their low concentration, high spatial variation and simultaneous presence make the measurement very difficult. We solved this metrology challenge by combining several techniques: Cu and Ar profiles can be nondestructively measured by operating Contact Radiography (CR) in a differential mode. The result, as well as the O profile, can be checked destructively by a quantitative Energy Dispersive Spectroscopy (EDS) method. Non-spatially resolved methods, such as absorption edge spectroscopy (and to a lesser accuracy, x-ray fluorescence) can calibrate the Ar and Cu measurement in EDS and CR. In addition, oxygen pick-up during mandrel removal can be validated by before-and-after CR and by density change. Use of all these methods gives multiple checks on the reported profiles. [Preview Abstract] |
Thursday, November 20, 2008 3:24PM - 3:36PM |
UO3.00008: Creating a Precision Optical Depth Uniformity Tool for Inertial Confinement Fusion Targets Samual Eddinger, Haibo Huang, Richard Stephens, Abbas Nikroo, Steve Haan NIF specifications require optical depth variation measurement accuracy to 10-4 in less than one day. We constructed a system by use of a precision rotation encoded air bearing, high speed PMT tubes, optimized optics, microfocus x-ray sources and fast scintillators to meet this specification. Through interleaving data, we eliminated long term drift, allowing us to have no other error sources but shot noise. As a result, the measurement time to get to the required statistics is the limiting factor. Our recent work integrated a microfocus x-ray source with minimal anode to window distance to maximize the counts in the PMT, and increase the system resolution. [Preview Abstract] |
Thursday, November 20, 2008 3:36PM - 3:48PM |
UO3.00009: Hard x-ray backlighters for high resolution Compton radiography of Inertial Confinement Fusion targets R. Tommasini, A. MacPhee, D. Hey, T. Ma, C. Chen, N. Izumi, A. MacKinnon, S.P. Hatchett, J.A. Koch, P. Springer, O.L. Landen Radiographs of the final stages of imploding DT fuel in inertial confinement fusion experiments will be extremely valuable for checking the convergence, areal density and areal density uniformity of the fuel. For x-rays with energies between 30 and 200 keV, the main opacity will be due to Compton scattering. Here we present the demonstration of 75-200 keV point backlighter sources generated by gold targets irradiated by picosecond laser pulses. In experiments performed at the Titan laser facility at Lawrence Livermore National Laboratory, we measured the source size and the Bremsstrahlung spectrum, as a function of laser intensity and pulse length, from by 5e17-5e18 W/cm$^{2}$ using 2-40 ps pulses. We achieved 1D and 2D source sizes of 10 $\mu $m, and conversion efficiencies exceeding 1e-3 J/J into x-ray photons with energies in the 100-200 keV spectral range. These sources meet the requirements for radiographing the fuel in inertial confinement fusion implosions at both OMEGA and the National Ignition Facility (NIF) whose experimental designs will also be discussed. [Preview Abstract] |
Thursday, November 20, 2008 3:48PM - 4:00PM |
UO3.00010: Development of a durable KrF laser for Inertial Fusion Energy Frank Hegeler, Moshe Friedman, Matthew Wolford, Matthew Myers, John Sethian, John Giuliani, Patrick Burns, Reginald Jaynes, Dennis Sadowski, Kevin Schoonover, Said Abdel-Khalik The krypton fluoride (KrF) laser facility, Electra, is a repetitively pulsed, electron beam pumped laser system at the Naval Research Laboratory, which is focused on the physics and requirements of a durable driver for Inertial Fusion Energy (IFE). The main laser amplifier has achieved repetitive operation of 1 to 5 Hz, continuous runs of 20,000 shots at 2.5 Hz as an oscillator, and a laser output of 300 to 700 J depending on the electron diode configuration. This presentation will provide an overview of the Electra Laser Facility and discuss recent and future modifications that should significantly improve the robustness of the laser. These include: (i) scalloped hibachi that will lower the mechanical stress of the diode vacuum/laser gas interface foil; (ii) testing of an all solid state pulsed power system; (iii) improvement of the 500 kV, 110 kA, 100 ns cathodes; and (iv) forced convective jet cooling of the foil that does not degrade the laser focal profile. Based on Electra advances with the above key components a wall plug efficiency of 6 to 7{\%} is projected for IFE systems. [Preview Abstract] |
Thursday, November 20, 2008 4:00PM - 4:12PM |
UO3.00011: Electra: Repetitively Pulsed Angularly Multiplexed KrF Laser System Performance Matthew Wolford, Matthew Myers, John Giuliani, John Sethian, Patrick Burns, Frank Hegeler, Reginald Jaynes As in a full size fusion power plant beam line, Electra is a multistage laser amplifier system. The multistage amplifier system consists of a commercial discharge laser and two doubled sided electron beam pumped amplifiers. Angular multiplexing is used in the optical layout to provide pulse length control and to maximize laser extraction from the amplifiers. Two angularly multiplexed beams have extracted 30 J of KrF laser light with an aperture 8 x 10 cm$^{2}$, which is sufficient to extract over 500 J from the main amplifier and models agree. The main amplifier of Electra in oscillator mode has demonstrated single shot and rep-rate laser energies exceeding 700 J with 100 ns pulsewidth at 248 nm with an aperture 29 x 29 cm$^{2}$. Continuous operation of the KrF electron beam pumped oscillator has lasted for more than 2.5 hours without failure at 1 Hz and 2.5 Hz. The measured intensity and pulse energy for durations greater than thousand shots are consistent at measurable rep-rates of 1 Hz, 2.5 Hz and 5 Hz. [Preview Abstract] |
Thursday, November 20, 2008 4:12PM - 4:24PM |
UO3.00012: ABSTRACT WITHDRAWN |
Thursday, November 20, 2008 4:24PM - 4:36PM |
UO3.00013: A Controlled Filament Non-Local Discharge (CFND) Plasma Z-Pinch Hugo Leon, George Miley, Linchun Wu A new type of pinch, the Controlled Filament Non-local Discharge (CFND) [1], is described. The CFND employs a unique cathode design with a ``spiked'' surface and built-in ballast resistors to stabilize the electron filaments generated during pulsed operation. As in the wire cage Z-pinch, the magnetic fields in the CFND consist of an overall poloidal field around the entire discharge and individual fields around each filament. This configuration is, then, analogous to a wire cage Z-pinch without physical wires. Thus, it exhibits enhanced stability during a pulse like the wire cage version. However, now the filaments are formed in the plasma discharge without requiring metallic wires, allowing simple rapid pulsing. Gradual erosion of the fielectrode spikes can limit the electrode lifetime, but methods to reduce this are being investigated. Data will be presented for hydrogen discharges along with a discussion of potential applications for radiation generation and fusion. [1] G. H. Miley, ``CFND for Pulsed Electric Discharge Lasers and Plasma Chemistry Reactors'' AIAA Plasmadynamics and Lasers Conference, Seattle WA, June 2008. [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