Bulletin of the American Physical Society
64th Annual Meeting of the APS Division of Plasma Physics
Volume 67, Number 15
Monday–Friday, October 17–21, 2022; Spokane, Washington
Session BO04: ICF DiagnosticsLive Streamed
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Chair: Kevin Meaney, LANL Room: Ballroom 111 A |
Monday, October 17, 2022 9:30AM - 9:42AM Author not Attending |
BO04.00001: Sensitivity Study of DT Cryogenic Implosions to Laser-Drive Nonuniformities Based on Explosion Phase Measurements on OMEGA Joshua Baltazar, Christian Stoeckl, Riccardo Betti, Varchas Gopalaswamy, James P Knauer, Dhrumir P Patel, Wolfgang R Theobald, Ka Ming Woo, Sean P Regan Low (l ≤ 6) and mid ( 6 < l ≤ 10) mode asymmetries, seeded by laser-drive nonuniformities and amplified by hydrodynamic instabilities, are possible performance degradation mechanisms for laser-direct-drive implosions on OMEGA. The nonuniformity is diagnosed from the x-ray emission limb at the corona–fuel interface during the explosion phase. The perturbations seeded by laser drive nonuniformity are varied by changing the ratio of the initial beam radius (Rb) to the target radius (Rt). This work presents an Rb/Rt scan of DT cryogenic implosions on OMEGA using explosion phase x-ray measurements. The x-ray emission from the implosion is recorded using a filtered, 16-pinhole array imager and an x-ray framing camera. The x-ray images have a spatial resolution of 15 mm and 40 ps temporal integration. A modal analysis is applied to the spatial distribution of the x rays and the rms amplitude for a set of implosions is presented as a function of Rb/Rt along with the evolution of the low and mid modes. Forward modeling of the x-ray framing camera is carried out using a Monte Carlo simulation to optimize the experimental design and to determine the error in the measurements. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0003856. |
Monday, October 17, 2022 9:42AM - 9:54AM |
BO04.00002: Determining X-ray conversion efficiency of direct drive implosions using Cubic Spline Unfolds of the Dante diagnostic Daniel H Barnak, Radha P Bahukutumbi, Sean P Regan, Michael J Rosenberg Broadband x-ray emission from direct drive inertial confinement fusion (ICF) implosions can be used to infer the total x-ray flux that is converted from the drive lasers as a function of time. A spectrally integrated soft x-ray diode array known as Dante records the flux of x-rays in specific photon energy bands by using a combination of grazing incidence mirrors, K-edge filters, and x-ray diodes. The voltage of the diodes is convolved with the response functions of the diodes, mirrors, and filters and can be directly inverted by assuming a cubic spline shape to the x-ray flux curve where the knot points of the spline coincide with the K-edges of each filtered channel [Soft x-ray spectrum unfold of K-edge filtered x-ray diode arrays using cubic splines, Review of Scientific Instruments 91, 073102 (2020)]. The analysis is done with the publicly available code Fiducia (https://pypi.org/project/fiducia/). Fiducia gives the time-resolved x-ray flux for both symmetric direct drive implosions at the OMEGA laser facility, and polar direct drive implosions at the National Ignition Facility (NIF). The time evolution of important x-ray photon energy bands is discussed. |
Monday, October 17, 2022 9:54AM - 10:06AM Author not Attending |
BO04.00003: Diagnosing Polar-Direct-Drive Energy Coupling at the National Ignition Facility Luke Ceurvorst, Wolfgang R Theobald, Michael J Rosenberg, Radha Bahukutumbi, Christian Stoeckl, Riccardo Betti, Kenneth Anderson, John A Marozas, Valeri N Goncharov, Mike Campbell, Sean P Regan, Claudia M Shuldberg, Rain W Luo, Wendi Sweet, Loosineh Aghaian, David N Kaczala, Benjamin Bachmann, Tilo Doeppner, Matthias Hohenberger, Kevin Glize, Robbie H Scott, Diego Viala, Arnaud Colaitis A series of experiments was performed at the National Ignition Facility (NIF) to diagnose energy coupling in polar direct drive using 2.1 mm dia. solid sphere targets directly driven by 184 laser beams using ramp pulses and varying the peak intensities between shots from 4 ´ 1014 W/cm2 to 1.2 ´ 1015 W/cm2. The evolution of the target was monitored by illuminating a Cu backlighter foil with the remaining eight beams, producing Hea emission to probe the system. These x rays were captured with a gated x-ray imager (GXI) to yield radiographs, which were analyzed to infer 2-D density profiles of the converging shock as a function of time. The resulting shock and ablation-front trajectories and inferred density profiles were then compared to 2-D radiation-hydrodynamic simulations from the DRACO code1 using cross-beam energy transfer (CBET) and nonlocal heat-transport models. The results demonstrate slight deviations as the intensity varies and a more-pronounced disagreement in the ablation-front trajectory. An investigation into this discrepancy is ongoing with CBET, nonlocal heat transport, and electron and radiative preheat identified as potential causes. The results will enable the validation and development of a quantitative scaling between OMEGA and the NIF. |
Monday, October 17, 2022 10:06AM - 10:18AM |
BO04.00004: Kr K-shell x-ray spectroscopy for hot implosion cores Enac Gallardo-Diaz, Roberto C Mancini, Jason Clapp, Patrick J Adrian, Tucker E Evans, Neel V Kabadi, Johan A Frenje Understanding the spatial structure of implosion cores is important for the development of well-characterized high-energy density science experimental platforms. To this end, we have employed Kr K-shell tracer spectroscopy to extract the temperature spatial distribution in exploding-pusher type implosions at OMEGA that produce core plasmas with electron temperatures of more than 2keV. Two slit imaging spectrometers equipped with Ge crystals were fielded to record spatially resolved Kr K-shell line emission in the photon energy range from 7keV to 20keV. The observations include n=2-1 transitions in Be-, Li- and He-like Kr ions as well as n=3-1 in He-like Kr and associated Li-like satellites. Significant differences are noted between core sizes based on continuum and on line emission. We discuss the interpretation and analysis of the data using detailed atomic and radiation physics models and several methods for the extraction of one-dimensional temperature gradients. |
Monday, October 17, 2022 10:18AM - 10:30AM |
BO04.00005: Commissioning a new neutron imaging system at the National Ignition Facility Mora Durocher, Noah W Birge, Christopher R Danly, Valerie Fatherley, David N Fittinghoff, Matthew Freeman, Verena Geppert-Kleinrath, Justin Jorgenson, Petr L Volegov, Carl H Wilde Neutron imaging systems (NIS) fielded at the National Ignition Facility (NIF) capture neutron images of inertial confinement fusion (ICF) implosions driven by the NIF 1.8 MJ laser. From these images, implosion shape information can be extracted to assess fusion fuel performance. The NIS began as a single line of sight (LoS), which captured gated and energy integrated neutron images. Today, the suite consists of three nearly orthogonal LoS's with neutron imaging capabilities. Additionally, two LoS's are also capable of capturing x-ray and gamma ray images which can be used to infer information about the distribution of higher Z material (Z>1) potentially limiting implosion performance. The NIS-3 gamma imaging capability was commissioned in 2020-2021. The NIS-1 gamma imaging capability was added recently as part of a substantial upgrade to the LoS, which included implementing a new aperture as well as new recording systems along this LoS. This talk will cover the commissioning of the NIS-1 upgrade and will show some preliminary 2D and 3D source reconstructions. |
Monday, October 17, 2022 10:30AM - 10:42AM |
BO04.00006: Spatially-Resolved Ion Temperature Measurement in ICF Christopher R Danly, Noah W Birge, Verena Geppert-Kleinrath, Brian M Haines, Steven T Ivancic, Justin Jorgenson, Joseph D Katz, Emily Mendoza, Andrew Sorce, Landon Tafoya, Petr L Volegov, Carl H Wilde Ion temperature is a fundamental plasma variable and key driver of ICF capsule performance. Further, studies have shown that cold fuel (DT ice) can be injected into the hotspot during implosion as a result of hydrodynamic effects such as fill tube jetting, and that this material can remain out of thermal equilibrium with the gas, leading to performance degradation. However existing ion temperature diagnostics provide only spatially integrated measurements, limiting understanding of these effects. We present design of, and results from, the first spatially-resolved ion temperature diagnostic developed for ICF. |
Monday, October 17, 2022 10:42AM - 10:54AM |
BO04.00007: Thin coded apertures for high-energy neutron and x-ray imaging Matthew P Selwood, David N Fittinghoff, Graeme G Scott, Chris Spindloe, Petr L Volegov, Jackson G Williams, Chris D Murphy The passive imaging of high-energy x-rays and neutrons is a useful diagnostic in laser-driven fusion as well as laboratory astrophysics experiments which aim to study small samples at high resolutions. Typical pinhole imaging systems require high attenuation for adequate image contrast. When high-resolution is also required, high aspect ratio pinholes are necessary and result in narrow fields of view and difficult to align diagnostics. |
Monday, October 17, 2022 10:54AM - 11:06AM |
BO04.00008: A Synthetic Diagnostic for the Knock-on Deuteron Imager Peter V Heuer, Hans Rinderknecht, Varchas Gopalaswamy, P. B Radha, Sean P Regan, Jonathan R Davies, Justin H Kunimune, Patrick J Adrian, Johan A Frenje, Maria Gatu-Johnson, Fredrick H Seguin, Aidan C Crilly The knock-on deuteron imager (KoDI) is a diagnostic designed to characterize the 3-D morphology of assembled fuel at the stagnation phase of direct-drive inertial confinement fusion implosions at the Omega Laser Facility. These measurements can diagnose 3-D asymmetries in the imploded fuel at stagnation, which degrade implosion performance. KoDI uses an array of penumbral apertures to image deuterons from the assembled fuel that are scattered by primary fusion neutrons. The source deuteron profile (and the associated fuel morphology) are then reconstructed from the penumbral images using an iterative maximum likelihood algorithm. The details of this algorithm determine the resolution and ultimately the validity of the reconstructions. In this talk we present a synthetic diagnostic that has been developed for KoDI and applied to validate this reconstruction algorithm. Studies of the algorithm stopping criteria and the effective resolution of the reconstruction may be applicable to other types of coded aperture imaging, e.g., neutron imaging. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0003856 and Department of Energy under Award Number DE-SC0020431. |
Monday, October 17, 2022 11:06AM - 11:18AM |
BO04.00009: Neutron Time-of-Flight based Reaction-in-Flight Fusion Measurements at the National Ignition Facility (NIF) Justin Jeet, Edward P Hartouni, Alastair S Moore, Mark J Eckart, Shaun M Kerr, Dave Schlossberg, Anna Hayes, Aidan C Crilly, Eddie F Mariscal At Inertial Confinement Fusion (ICF) facilities, such as the National Ignition Facility (NIF), the deuterium-tritium (D-T) reaction is a top candidate for demonstrating ignition. The primary products of the reaction include neutrons and alpha particles. The reaction-in-flight (RIF) neutron spectrum results from up-scattered deuterons and tritons that gain energy through elastic scattering with the fusion products (n, a) and then undergo fusion reactions. Stopping power losses in the fuel affect the RIF spectrum and therefore make it sensitive to the conditions of the hot-spot and fuel shell. RIF spectra are sensitive to key properties of the fuel such as the mix fraction, quantum degeneracy of the cold fuel, the fuel adiabat, as well as the alpha stopping range. The NIF hosts a suite of neutron time-of-flight (nToF) detectors at five different line-of-sight locations. These spectrometers can span over six orders of magnitude in dynamic range to measure both the primary D-T fusion and RIF spectra. This work will discuss recent progress towards nToF based RIF measurements as well as its implications in providing a better understanding of implosion performance at the NIF. |
Monday, October 17, 2022 11:18AM - 11:30AM Author not Attending |
BO04.00010: Hot spot velocity measurements using the deuterium-deuterium peak at the National Ignition Facility Shaun M Kerr, Edward P Hartouni, David J Schlossberg, Alastair S Moore, Justin Jeet, Mark J Eckart, Aidan C Crilly The center-of-mass velocity of the fusing plasma in an Inertial Confinement Fusion (ICF) implosion can be determined from shifts in the first moment of the fusion neutron peak, measured by neutron time-of-flight (nToF) diagnostics. This “hot spot” velocity is correlated with ICF performance [1] and can provide insight into other aspects of implosion physics. At the National Ignition Facility Cherenkov-based detectors provide unprecedented precision in hot spot velocities derived from the deuterium-tritium (D-T) neutron peak, thereby uncovering unique features of burning plasma implosions. Here we present hot spot velocities determined from the deuterium-deuterium (D-D) neutron peak using scintillator measurements. The reduced velocity of D-D neutrons compared to D-T neutrons relaxes the diagnostic timing requirements and allows precision measurements to be made with scintillator-based nToFs. In addition to providing a consistency check of the D-T results, this data gives additional understanding of burning plasma ICF implosions. |
Monday, October 17, 2022 11:30AM - 11:42AM |
BO04.00011: 3D reconstruction techniques for imaging of knock-on deuterons from cryo DT inertial confinement fusion implosions Justin H Kunimune, Hans Rinderknecht, Peter V Heuer, Patrick J Adrian, Sean P Regan, Maria Gatu Johnson, Fredrick H Seguin, Johan A Frenje, Radha P Bahukutumbi, James P Knauer, Benjamin Bachmann, Daniel T Casey, Verena Geppert-Kleinrath Knock-on deuteron imaging is a method for probing the 3D morphology of a cryogenic DT inertial confinement fusion (ICF) implosion. It uses deuterons elastically scattered by fusion neutrons from the fuel layer of the implosion. High-energy deuterons are produced by forward-scattering, and thus provide an image of the neutron-emitting hot spot of the implosion. Low-energy deuterons are produced by side-scattering and energy-slowing down in the fuel, and thus provide information about the dense fuel surrounding the hot spot. As knock-on deuteron images are collected on multiple lines of sight, 3D reconstruction algorithms are required to combine them to form a complete picture of the implosion morphology. Traditional tomographic techniques are not applicable because of the nonlinear relationship between the temperature and density profiles in the implosion and the energy-resolved deuteron image on a given line of sight. Novel iterative reconstruction algorithms that properly account for this relationship have been developed and applied to knock-on deuteron images from warm CD shell implosions at OMEGA. Insights into the 3D shapes of the implosions are presented and discussed. |
Monday, October 17, 2022 11:42AM - 11:54AM |
BO04.00012: Fusion burn width measurements and trends in high performing inertial confinement fusion experiments Hermann Geppert-Kleinrath, Kevin D Meaney, Yongho Kim, Jorge A Carrera, Eddie F Mariscal In Inertial Confinement Fusion (ICF) deuterium-tritium (DT) fusion reaction rates are an important measurement providing crucial performance parameters for implosion experiments (shots) such as fusion bang time and fusion burn width. With increasing performance at the National Ignition Facility (NIF) fusion burn width is getting shorter and dropping below 100 ps. Gas Cherenkov Detector (GCD) performs energy-thresholded measurements of the DT fusion reaction rate. However, state-of-the-art photomultiplier tubes (PMT) limits the temporal resolution to ~100 ps, making shot-to-shot performance hard to differentiate at narrow burn width. The Pulse Dilation – PMT (PD-PMT) makes measurements at a temporal resolution of 10 ps possible. Unfortunately, x-ray or neutron-induced gamma backgrounds corrupted the burn width measurements performed and clean data could not be produced. Recent improvements overcome this issue and high temporal resolution DT fusion burn rates are possible on high yield shots at NIF. First results - including a record yield shot at NIF – and performance trends are presented. The shapes of the DT gamma reaction history can be compared with simulation results for the first time. |
Monday, October 17, 2022 11:54AM - 12:06PM |
BO04.00013: Time-resolved measurement of the x-ray continuum spectra of an inertial confinement fusion implosion Stanislav Stoupin, Andrew G MacPhee, David J Schlossberg, Neil Ose, Michael J MacDonald, Dean Rusby, Marilyn B Schneider We report a time-resolved measurement of the x-ray continuum spectra of an indirect-drive inertial confinement fusion implosion using a tritium-deuterium-hydrogen mix as the fuel. The spectra in the energy range of 23-28 keV were measured using a new version of a conical graphite crystal spectrometer [1,2] coupled with a specialized x-ray streak camera [3,4]. The time history of the logarithmic slope of the spectra representing the electron temperature of the hot spot was extracted using forward fitting of the time-energy binned streak camera signal to the expected Maxwellian spectral shape. The measurement uncertainties were obtained using a recently developed Monte-Carlo technique [5]. The time-resolved (30 ps time bins) electron temperature was found to vary within the duration of the hot-spot x-ray emission (~120 ps FWHM), rising from ~ 3keV up to 5.2 keV at peak emission and then slightly decreasing to ~4.5 keV. While the obtained ~12% r.m.s. uncertainties on the electron temperature prevent more detailed interpretation of the temperature’s time-history, this can be substantially improved (down to ~4% r.m.s) by reducing x-ray attenuation in the spectrometer. On a follow up implosion this would lead to more optimized x-ray detection by the streak camera. |
Monday, October 17, 2022 12:06PM - 12:18PM |
BO04.00014: First measurement of the 10B(α,n)13N reaction in an ICF implosion at NIF: Initial steps toward the development of a radiochemistry mix diagnostic Diego Lonardoni During the deceleration phase of an ICF implosion, instabilities growth can lead to mixing between the ablator material and the thermonuclear fuel. Mixing is undesirable, as it reduces the performance of the capsule. One method to diagnose mixing is to study the x-ray emission from the burning fuel. However, double shell and pushered single shell designs for the National Ignition Facility (NIF) render this technique ineffective because they involve a high-Z shell surrounding the fuel that is opaque to x-rays. A possible alternative mix diagnostic involves measuring the interaction of alpha particles, produced in the D+T→α+n reaction, with the ablator material. The Radiochemical Analysis of Gaseous Samples (RAGS) facility at NIF allows for quantitative measurements of α-induced reactions. |
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