Bulletin of the American Physical Society
58th Annual Meeting of the APS Division of Plasma Physics
Volume 61, Number 18
Monday–Friday, October 31–November 4 2016; San Jose, California
Session YO5: Short Pulse Laser Interactions and Electron Transport |
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Chair: Christine Krauland, General Atomics Room: 230 B |
Friday, November 4, 2016 9:30AM - 9:42AM |
YO5.00001: Generation of heavy ion beams using high-intensity short pulse lasers. George Petrov, Chris McGuffey, Alec Thomas, Karl Krushelnick, Farhat Beg A theoretical study of ion acceleration from high-Z material irradiated by intense sub-picosecond lasers is presented. The underlying physics of beam formation and acceleration is similar for light and heavy ions, however, nuances of the acceleration process make the heavy ions more challenging. At least four technical hurdles have been identified: low charge-to-mass ratio, limited number of ions amenable to acceleration, delayed acceleration and poor energy coupling due to high reflectivity of the plasma. Using two dimensional particle-in-cell (PIC) simulations, we observed transitions from Radiation Pressure Acceleration (RPA) to the Breakout Afterburner regime (BoA) and to Target Normal Sheath Acceleration (TNSA) akin to light ions. The numerical simulations predict gold ions beams with high directionality (\textless 10 degrees half-angle), high fluxes (\textgreater 10$^{\mathrm{11}}$ ions/sr) and energy (\textgreater 10 MeV/nucleon) from laser systems delivering \textgreater 20 J of energy on target [1]. [1] G. M. Petrov, C. McGuffey, A. G. R. Thomas, K. Krushelnick, and F. N. Beg, Phys. Plasmas 23, 063108 (2016). [Preview Abstract] |
Friday, November 4, 2016 9:42AM - 9:54AM |
YO5.00002: Electron Temperature Measurement of Buried Layer Targets Using Time Resolved K-shell Spectroscopy Edward Marley, M. E. Foord, R. Shepherd, P. Beiersdorfer, G. Brown, H. Chen, J. Emig, M. Schneider, K. Widmann, H. Scott, R. London, M. Martin, B. Wilson, C. Iglesias, C. Mauche, H. Whitley, J. Nilsen, D. Hoarty, S. James, C.R.D. Brown, M. Hill, P. Allan, L. Hobbs Short pulse laser-heated buried layer experiments have been performed with the goal of creating plasmas with mass densities $\geq$ 1 g/cm$^{3}$ and electron temperatures $\geq$ 500 eV. The buried layer geometry has the advantage of rapid energy deposition before significant hydrodynamic expansion occurs. For brief periods ($<$ 40 ps) this provides a low gradient, high density platform for studying emission characteristics under extreme plasma conditions. A study of plasma conditions achievable using the Orion laser facility has been performed. Time resolved K-shell spectroscopy was used to determine the temperature evolution of buried layer aluminum foil targets. The measured evolution is compared to a 2-D PIC simulation done using LSP, which shows late time heating from the non-thermal electron population. [Preview Abstract] |
Friday, November 4, 2016 9:54AM - 10:06AM |
YO5.00003: Investigation of Super-Ponderomotive Electron Generation Using the Texas Petawatt Laser J. Peebles, S. Zhang, C. McGuffey, M. S. Wei, D. Mariscal, H. S. McLean, H. Chen, E. McCary, C. Wagner, M. Spinks, B. M. Hegelich, E. Gaul, G. Dyer, M. Martinez, M. Donovan, T. Ditmire, S. Krasheninnikov, F. Beg Relativistic laser plasma interactions (LPI) in conjunction with an underdense pre-plasma have been shown to generate extremely high energy "super-ponderomotive" electrons. We conducted an experiment at the Texas Petawatt Laser Facility with recent pre-pulse cleaning upgrades in order to better understand the conditions required to generate such high energy electrons. We created the pre-plasma by introducing a controlled injected pre-pulse via a secondary beam prior to the main high intensity ($I > 10^{20} W/cm^2 $) beam's arrival. The pulse length of the main beam was varied from 150 - 600 fs. The experimental data demonstrated that super-ponderomotive electrons require a pulse of at least 450 fs to be generated. Such interactions generated electrons with energies greatly exceeded 150 MeV, which also corresponded to an unexpected drop in lower energy electron count. We present these experimental findings along with subsequent 1 and 2D PIC simulations examining the results. [Preview Abstract] |
Friday, November 4, 2016 10:06AM - 10:18AM |
YO5.00004: Plasma Wave Seed for Raman Amplifiers Kenan Qu, Ido Barth, Nathaniel Fisch It is proposed to replace traditionally used laser seed in backward Raman amplifiers with initial plasma wave seed. We show, analytically and numerically, that similarly to laser seeds plasma seeds result in Raman amplified pulse in both the linear and nonlinear regimes. The plasma seed is prepared in advance with a certain wavevector and envelope at one edge of the plasma. This methodology is attractive because it avoids issues in preparing and synchronizing frequency shifted laser seed. [Preview Abstract] |
Friday, November 4, 2016 10:18AM - 10:30AM |
YO5.00005: Study of fast electron transport and ionization in isochorically heated solid foil Hiroshi Sawada, Yasuhiko Sentoku, Rishi Pandit, Toshinori Yabuuchi, Ulf Zastrau, Eckhart Foerster, Farhat Beg, Harry McLean, Hui Chen, J-B Park, Prav Patel, Anthony Link, Yuan Ping Interaction of a high-power, short-pulse laser with a solid target generates a significant number of relativistic MeV electrons, subsequently heating the target isochorically in the transport process. Fast electron driven ionization of a solid titanium foil was studied by measuring Ti K-alpha x-rays and performing 2-D particle-in-cell simulations. The experiment was performed using the 50 TW Leopard short-pulse laser at UNR's Nevada Terawatt Facility. The 15 J, 0.35 ps laser was tightly focused on to a various sized, 2-$\mu $m thick Ti foil within a 8 $\mu $m spot to achieve the peak intensity of \textasciitilde 2\texttimes 10$^{\mathrm{19}}$ W/cm$^{\mathrm{2}}$. The transport of the fast electrons produced 4.51 keV Ti K-alpha x-rays. The yields and 2-D monochromatic images were recorded with a Bragg crystal spectrometer and a spherically bent crystal imager. The ionization degree of the heated foil was determined to be \textasciitilde 15 from the ionized K-alpha lines and the missing emission in the images. 2-D PIC simulations using a PICLS code with a radiation transport module were performed to calculate the K-alpha profiles and spectra. Details of the experiment and comparison will be presented. [Preview Abstract] |
Friday, November 4, 2016 10:30AM - 10:42AM |
YO5.00006: Phase contrast imaging of high-intensity laser hole boring of solid-density wires at LCLS-MEC W Schumaker, S Brown, C Curry, M Gauthier, E Gamboa, S Goede, L. Fletcher, J. Kim, M MacDonald, R Mishra, C Roedel, S Glenzer, F Fiuza, E Granados, B Nagler, Z Zhou, A MacKinnon, L Obst, K Ziel, A Pak, G Williams, M Fajardo High-intensity, relativistic ($a_0 > 1$) laser plasma interactions on solid surfaces produce a rich mix of dynamics on the laser timescale (Weibel instabilities, surface effects, sheath formation, etc.) and hydrodynamic timescale (hole-boring, shocks, etc.). Probing these interactions optically is difficult due to critical density layer obscuring the surface of the target, whereas probing with hard X-rays from K-alpha sources does not sufficiently resolve these interactions temporally as they are typically many $ps$ in duration. Presented here are the first experimental measurements of laser hole-boring on a carbon wire surfaces performed at the LCLS-MEC facility. With laser intensities of up to $10^{19} W/cm^2$, we observe the dissociation of micron-sized wires over $100 ps$ timescale with peak hole boring velocities up to $0.001c$ using phase-contrast imaging. [Preview Abstract] |
Friday, November 4, 2016 10:42AM - 10:54AM |
YO5.00007: High Repetition-Rate Neutron Generation by Several-mJ, 35 fs pulses interacting with Free-Flowing D$_{\mathrm{2}}$O. Jungmoo Hah, George Petrov, John Nees, Zhaohan He, Mark Hammig, Karl Krushelnick, Alexander Thomas Recent advance in ultra-high power laser technology allows a development of laser-based neutron sources. Here we demonstrate heavy-water based neutron source. Using several-mJ energy pulses from a high-repetition rate ( \textonehalf kHz), ultrashort (35 fs) pulsed laser interacting with a $\sim $ 10 $\mu $m diameter stream of free-flowing heavy water (D$_{\mathrm{2}}$O), we get a 2.45 MeV neutron flux of 10$^{\mathrm{5}}$/s. In the intentionally generated pre-plasma, laser pulse energy is efficiently absorbed, and energetic deuterons are generated. As a convertor, the bulk heavy water stream target and the large volume of low density D$_{\mathrm{2}}$O vapor near the target are collided with accelerated deuterons, generating neutron through d(d,n)$^{\mathrm{3}}$He reactions. As laser pulse energy increased from 6mJ to 12mJ, the neutron flux increased. From the 2D particle-in-cell simulation, comparable neutron fluxes are shown at the similar laser characteristics to the experiment. Also, simulation shows forward and backward moving deuterons, which are main distributing ions impinging upon D$_{\mathrm{2}}$O stream and vapor, respectively. [Preview Abstract] |
Friday, November 4, 2016 10:54AM - 11:06AM |
YO5.00008: Simulations On Pair Creation In Collision Of $\gamma$-Beams Produced With High Intensity Lasers Oliver Jansen, Xavier Ribeyre, Emmanuel d'Humieres, Mathieu Lobet, Sophie Jequier, Vladimir Tikhonchuk Direct production of electron-positron pairs in two photon collisions, the Breit-Wheeler process, is one of the most basic processes in the universe. However, this process has never been directly observed in the laboratory due to the lack of high intensity $\gamma$ sources. For a feasibility study and for the optimisation of experimental set-ups we developed a high-performance tree-code. Different possible set-ups with MeV photon sources were discussed and compared using collision detection for huge number of particles in a quantum-electrodynamic regime. [Preview Abstract] |
Friday, November 4, 2016 11:06AM - 11:18AM |
YO5.00009: Study of laser-generated debris free x-ray sources produced in a high-density linear Ar, Kr, Xe, Kr/Ar and Xe/Kr/Ar mixtures gas jets by 2$\omega $, sub-ps LLNL Titan laser. V.L. Kantsyrev, K.A. Schultz, V.V. Shlyaptseva, A.S. Safronova, M.C. Cooper, I.K. Shrestha, E.E. Petkov, A. Stafford, J.J. Moschella, M.T. Schmidt-Petersen, C.J. Butcher, G.E. Kemp, S.D. Andrews, K.B. Fournier The study of laser-generated debris-free x-ray sources in an underdense plasma produced in a high-density linear gas-puff jet was carried out at the LLNL Titan laser (2$\omega $, 45 J, sub-ps) with an intensity in the 10 um focal spot of 7 x 10$^{\mathrm{19}}$ W/cm$^{\mathrm{2}}$. A linear nozzle with a fast valve was used for the generation of a clusters/gas jet. X-ray diagnostics for the spectral region of 0.7 - 9 keV include: two spectrometers and pinhole cameras, and 3 groups of fast filtered detectors. Electron beams were measured with the EPPS magnetic spectrometer (\textgreater 1 MeV) and Faraday cups (\textgreater 72 keV). Spectralon/spectrometer devices were also used to measure absorption of laser radiation in the jets. New results were obtained on: anisotropic generation of x-rays (laser to x-ray conversion coefficient was \textgreater ~1{\%}) and characteristics of laser-generated electron beams; evolution of x-ray generation with the location of the laser focus in a cluster-gas jet, and observations of a strong x-ray flash in some focusing regimes. Non-LTE kinetic modeling was used to estimate plasma parameters. UNR work supported by the DTRA Basic Research Award {\#} HDTRA1-13-1-0033. Work at LLNL was performed under the auspices of the U.S. DOE by LLNL under Contract DE-AC52-07NA27344. [Preview Abstract] |
Friday, November 4, 2016 11:18AM - 11:30AM |
YO5.00010: Increased x-ray conversion efficiency from ultra high contrast, relativistic laser pulse irradiation of large aspect ratio, vertically aligned nanowires R.C. Hollinger, C. Bargsten, V.N. Shlyaptsev, V. Kaymak, A. Pukhov, M.G. Capeluto, Y. Wang, S. Wang, A. Rockwood, A. Curtis, J.J. Rocca Recent experiments at Colorado State University have shown that the effective trapping of clean, Joule-level fs laser pulses of relativistic intensity in arrays of high aspect ratio aligned nanowire creates multi-kev, near solid density, large scale (\textgreater 4um deep) plasmas. The drastically decreased radiative life time and increased hydrodynamic cooling time from these plasmas increases the x-ray conversion efficiency. We measured a record conversion efficiency of \textasciitilde 10{\%} into hv\textgreater 1KeV photons (2pi steradians), and of 0.3{\%} for hv\textgreater 6KeV. The experiments used Au and Ni nanowires of 55nm, 80nm and 100nm in diameter with 12{\%} of solid density irradiated by high contrast (\textgreater 10$^{\mathrm{12}})$ pulses of 60fs FWHM duration from a frequency doubled Ti:Sa laser at intensities of I$=$5x10$^{\mathrm{19}}$Wcm$^{\mathrm{-2.\thinspace }}$We also present preliminary results on x-ray emission from Rhodium nanowires in the 19-22KeV range and demonstrate the potential of this picosecond X-ray source in flash radiography. [Preview Abstract] |
Friday, November 4, 2016 11:30AM - 11:42AM |
YO5.00011: Characterization of \textgreater 100 T magnetic fields associated with relativistic Weibel instability in laser-produced plasmas. Rohini Mishra, Charles Ruyer, Sebastian Goede, Christian Roedel, Maxence Gauthier, Karl Zeil, Ulrich Schramm, Siegfried Glenzer, Frederico Fiuza Weibel-type instabilities can occur in weakly magnetized and anisotropic plasmas of relevance to a wide range of astrophysical and laboratory scenarios. It leads to the conversion of a significant fraction of the kinetic energy of the plasma into magnetic energy. We will present a detailed numerical study, using 2D and 3D PIC simulations of the Weibel instability in relativistic laser-solid interactions. In this case, the instability develops due to the counter-streaming of laser-heated electrons and the background return current. We show that the growth rate of the instability is maximized near the critical density region on the rear side of the expanded plasma, producing up to 400 MG magnetic fields for Hydrogen plasmas. We have found that this strong field can be directly probed by energetic protons accelerated in rear side of the plasma by Target Normal Sheath Acceleration (TNSA). This allows the experimental characterization of the instability from the analysis of the spatial modulation of the detected protons. Our numerical results are compared with recent laser experiments with Hydrogen jets and show good agreement with the proton modulations observed experimentally. [Preview Abstract] |
Friday, November 4, 2016 11:42AM - 11:54AM |
YO5.00012: Intra-pulse transition between ion acceleration mechanisms in intense laser-foil interactions Hersimerjit Padda, Martin King, Ross Gray, Haydn Powell, Bruno Gonzalez-Izquierdo, Luca Stockhausen, Robbie Wilson, David Carroll, Rachel Dance, David MacLellan, Xiaohui Yuan, Nick Butler, Remi Capdessus, Marco Borghesi, David Neely, Paul McKenna Laser-driven sheath acceleration of ions has been widely studied and the recent move to ultra thin foil interactions enables promising new acceleration mechanisms. However, the acceleration dynamics in this regime are complex and over the course of the laser-foil interaction multiple ion acceleration mechanisms can occur, resulting in the dominant mechanism changing throughout the interaction. Measuring the spatial intensity distribution of the accelerated proton beam we investigate the transition from radiation pressure acceleration to transparency-driven processes. Using PIC simulations, the radiation pressure drives an increased expansion of the target ions, which results in a radial deflection of low MeV protons to form an annular distribution. By varying the thickness of the target, the opening angle of the ring is shown to be correlated to the point in time that transparency occurs and is maximised at the peak of the laser intensity profile. Measurements of the ring size as a function of target thickness are found to be in good agreement with the simulation results. [Preview Abstract] |
Friday, November 4, 2016 11:54AM - 12:06PM |
YO5.00013: Giant magnetic fields and relativistic electron transport in dense, hot plasmas created on solid targets Ravindra Kumar Gattamraju, Moniruzzaman Shaikh, Amit Lad, Deep Sarkar, Kamalesh Jana, Indranuj Dey Intense,femtosecond laser pulses generate relativistic electron pulses,important for many applications\cite{Drakebook}. In this paper, we present a femtosecond time-resolved and micrometer space resolved giant magnetic fields generated by 10$^{19}$ W cm$^{-2}$, 800 nm, 30 fs, high intensity contrast laser pulses in using pump-probe Cotton Mouton polarimetry\cite{ChatterjeeRSI2014}. The space and time resolved maps of the magnetic fields at the front and rear of targets reveal turbulence in the magnetic fields \cite{MondalPNAS2012}. We also present data from shadowgraphy and Cherenkov emission along with model calculations to build up a picture of the transport process.\newline $[1]$ Drake R. P. \textit{High-Energy-Density Physics} (Springer-Verlag, Berlin Heidelberg, 2006).\newline [2] Chatterjee G. \textit{et al.} \textit{Rev. Sci. Instr.} \textbf{85,}, 013505 (2014).\newline [3]Mondal S. \textit{et al.} . \textit{Proc. Natl. Acad. Sci. USA} \textbf{109,} 8011 (2012). [Preview Abstract] |
Friday, November 4, 2016 12:06PM - 12:18PM |
YO5.00014: Laser absorption and electron propagation in rippled plasma targets Chandrasekhar Shukla, Amita Das, Kartik Patel Efficient absorption of laser energy and the collimated propagation of relativistic electron beams (generated by the laser target interaction) in plasma are two issues which are of significant importance for applications such as fast ignition scheme of inertial confinement fusion (ICF). It is shown with the help of 2-D Particle- In- Cell simulations that introducing density ripples transverse to the laser propagation direction enhances the efficiency of laser power absorption. Furthermore, the density ripples are also instrumental in suppressing the Weibel instability of the propagating electron beam (which is responsible for the divergence of the beam). A physical understanding of the two effects is also provided. [Preview Abstract] |
Friday, November 4, 2016 12:18PM - 12:30PM |
YO5.00015: Preliminary investigations on 3D PIC simulation of DPHC structure using NEPTUNE3D code. Hailong Zhao, Ye Dong, Haijing Zhou, Wenkang Zou, Qiang Wang Cubic region (34cm×34cm×18cm) including the double post-hole convolute (DPHC) structure was chosen to perform a series of fully 3D PIC simulations using NEPTUNE3D codes, massive data (\textasciitilde 200GB) could be acquired and solved in less than 5 hours. Cold-chamber tests were performed during which only cathode electron emission was considered without temperature rise or ion emission, current loss efficiency was estimated by comparisons between output magnetic field profiles with or without electron emission. PIC simulation results showed three stages of current transforming process with election emission in DPHC structure, the maximum (\textasciitilde 20{\%}) current loss was 437kA at 15ns, while only 0.46{\%}\textasciitilde 0.48{\%} was lost when driving current reached its peak. DPHC structure proved valuable functions during energy transform process in PTS facility, and NEPTUNE3D provided tools to explore this sophisticated physics. [Preview Abstract] |
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