Bulletin of the American Physical Society
63rd Annual Meeting of the APS Division of Plasma Physics
Volume 66, Number 13
Monday–Friday, November 8–12, 2021; Pittsburgh, PA
Session BO04: Laser-Plasma Wakefield and Direct Laser AcceleratorsOn Demand
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Chair: Louise Willingale, University of Michigan Room: Rooms 304-305 |
Monday, November 8, 2021 9:30AM - 9:42AM |
BO04.00001: High Energy, Relativistic Intensity Laser Channeling and Direct Laser Acceleration of Electrons from an Underdense Plasma Hongmei Tang, Andrew McKelvey, Paul T Campbell, Brandon K Russell, Yong Ma, Alex V Arefiev, I-Lin Yeh, Kavin Tangtartharakul, Hui Chen, Felicie Albert, Jessica Shaw, Philip M Nilson, Louise Willingale The channeling of a high-intensity laser pulse through an underdense plasma and simultaneous direct laser acceleration of electrons to superponderomotive energies are dynamic and complex processes. For all laser-plasma interactions, the transfer of the laser energy to the electrons is the fundamental step and also has applications in producing secondary radiation like bright, directional X-ray beams. A wide variety of parameter scans were performed using the OMEGA EP facility to explore the effect of experimental conditions, i.e.\ laser pulse duration, focusing geometry, plasma density, on the channel evolution and relativistic electron acceleration. Proton deflectometry observed the channel evolution, instabilities and filament formation. Corresponding particle-in-cell simulations illustrate the laser modulation, channel electromagnetic fields development and electron movement in interaction with laser pulse, giving insight into the energy transfer mechanism. Using simulations, we study double pulse interactions to separate the channel and quasi-static field formation by a leading pulse, to enable a trailing laser pulse to be better guided in the preformed channel and therefore more effectively couple energy to the electrons. We would like to acknowledge the OSIRIS Consortium. |
Monday, November 8, 2021 9:42AM - 9:54AM |
BO04.00002: On the particle resonances and trapping of direct laser acceleration Feiyu Li, Prashant Singh, Sasi Palaniyappan, Chengkun Huang As one of the leading acceleration mechanisms in laser-driven underdense plasmas, direct laser acceleration (DLA) is capable of producing high-current electron beams in a plasma channel for several applications. However, the mechanism relies on highly nonlinear particle-laser resonances, rendering its modeling and control to be very challenging. Here, we report on novel physics of the particle resonances and, based on that, define a potential path toward more controlled DLA. Key findings are acquired by treating the electron propagation angle independently within a comprehensive model. This approach uncovers the complete particle resonances over broad propagation angles, the physical regimes under which paraxial/nonparaxial dynamics dominates, a unified picture for different harmonics, and crucially, the physical accessibility to these particle resonances. These new insights can have important implications where we address the basic issue of particle trapping as an example. We show how the uncovered trapping parameter space can lead to better acceleration control. More implications for the development of this basic type of acceleration are discussed. |
Monday, November 8, 2021 9:54AM - 10:06AM |
BO04.00003: Examination of the acceleration mechanisms for relativistic electron generation in an underdense, laser-driven plasma in the picosecond regime Kelly Swanson, Graeme G Scott, Chris D Armstrong, Elizabeth S Grace, Ghassan Zeraouli, Tammy Ma Energetic electrons accelerated through intense laser-plasma interactions are useful for driving secondary particle and radiation sources such as ions, x-rays, and neutrons. Depending on the laser and solid target plasma conditions, electrons can be accelerated by several mechanisms such as target normal sheath acceleration, hole boring, break-out afterburner, or direct laser acceleration, each resulting in electron spectra with its own defining characteristics. To study these mechanisms, we performed experiments on the Vulcan Target Area West (TAW) laser at the Rutherford Appleton Laboratory’s Central Laser Facility, exploring the dynamics of high-intensity laser pulses with picosecond pulse durations irradiating short plasma channels of varying density. This regime is of particular interest to experiments utilizing solid density targets where the laser pre-pulse creates a sub-critical plasma in which electrons can be accelerated to high energies in a short distance. To better understand the different acceleration mechanisms, we investigated key components of the laser-plasma interaction, including plasma density and channel length, and studied their impact on the energy gain and angular spread of accelerated electrons. |
Monday, November 8, 2021 10:06AM - 10:18AM |
BO04.00004: Electron Radiography Based on Electron Beams from Self-Modulated Laser Wakefield Acceleration Jessica Shaw, Gerrit Bruhaug, Matthew Freeman, Frank Merrill, Verena Geppert-Kleinrath, Carl H Wilde, Hans Rinderknecht, Dustin H Froula We report on first experiments demonstrating electron radiography using the electron beam produced by self-modulated laser wakefield acceleration (SMLWFA) driven by the OMEGA EP laser. SMLWFA driven by picosecond-scale, kilojoule-class lasers enables electron beams that could be coupled to experiments driven by large-scale, high-energy drivers. The SMLWFA platform on OMEGA EP has demonstrated electron beams with electron energies exceeding 200 MeV, divergences as low as 32 mrad, charge exceeding 700 nC, and laser-to-electron conversion efficiencies up to 11%. These electron beams have been used to probe mid- to high-Z radiography test objects. Different styles of electron beams were produced to determine which are most conducive to electron radiography measurements. Preliminary findings suggest resolutions of 75 to 125 mm, depending on material depth. |
Monday, November 8, 2021 10:18AM - 10:30AM |
BO04.00005: 15 MeV quasimonoenergetic electrons at 1 kHz with circularly polarized few-cycle pulses Manh S Le, Fatholah Salehi, Lucas Railing, Miroslav Kolesik, Howard M Milchberg We compare the acceleration of quasi-monoenergetic electron bunches to 15 MeV using linearly (LP) and circularly polarized (CP) < 3 mJ, 5 fs pulses from a kHz laser system. Our previous laser wakefield acceleration (LWFA) experiments in the self-modulated regime, using 30-50 fs pulses, demonstrated that near-critical plasma densities reduced the needed power for relativistic self-focusing and enabled mJ-scale laser pulses to accelerate electrons to energies of a few MeV in a thermal spectrum [1, 2]. Our recent experiments, using few-cycle duration laser pulses driving wakefield bubbles at near-critical plasma densities, demonstrate acceleration of quasi-monoenergetic electron bunches to 15 MeV with low angular divergence of 7 mrad [3]. This result is obtained by mitigating the effect of carrier envelope phase (CEP) slip [4,5], due to the difference in group and phase velocity of the laser pulse in plasma, which can drive transverse oscillations of the bubble in the polarization plane and increase electron bunch divergence. We show that use of CP minimizes CEP-induced beam divergence compared to LP. [1]F. Salehi et al., Opt. Lett. 42, 215 (2017). [2]A. J. Goers et al. , Phys. Rev. Lett. 115, 194802 (2015). [3]F. Salehi et al., Phys. Rev. X 11, 021055 (2021) [4]E. N. Nerush and I. Yu. Kostyukov, Phys. Rev. Lett. 103, 035001 (2009). [5]J. Huijts et al., Phys. Plasmas 28, 043101 (2021) |
Monday, November 8, 2021 10:30AM - 10:42AM |
BO04.00006: GeV Electron Acceleration by Self-waveguiding Pulses Jaron E Shrock, Linus Feder, Bo Miao, Alexander Picksley, Simon Hooker, Shoujun Wang, Reed C Hollinger, Huanyu Song, Ryan Nedbailo, John Morrison, Jorge J Rocca, Howard M Milchberg We present the first demonstration of multi-GeV LWFA in a fully optically formed plasma waveguide. On the ALEPH laser at CSU, novel waveguiding techniques [1,2], were applied to PW-scale pulses over 20 cm, driving GeV electron acceleration. Employing the self-waveguiding method [2], a J0 Bessel beam is formed along an extended gas jet composed of a 0.5 cm Ar-doped H2 ionization injection region and 19.5 cm pure H2 guiding section (H2 density~1018 cm-3). This ‘index structuring’ J0 beam ionizes a plasma column which expands outwards, driving a shock in the neutral gas at the plasma boundary. A high intensity pulse (1019 W/cm2, 35 μm waist) is then injected into the prepared index profile. The leading edge of the pulse ionizes the neutral shock, generating an “on-the-fly” waveguiding structure for the rest of the pulse. Concurrently, the peak of the pulse drives a wakefield in the plasma along the axis. |
Monday, November 8, 2021 10:42AM - 10:54AM |
BO04.00007: A hundred TW dual laser system for compact laser plasma accelerators, laser driven photon sources, and HED experiments at BELLA Center Robert E Jacob, Tobias M Ostermayr, Hai-En Tsai, Sahel Hakimi, Liona Fan-Chiang, Samuel Barber, Fumika Isono, Jeroen van Tilborg, Anthony J Gonsalves, Kei Nakamura, Csaba Toth, Carl B Schroeder, Cameron R Geddes, Eric Esarey We present the BELLA 100 TW two-beam laser system as a capable platform for the development of laser plasma accelerators, related light sources in the keV and MeV range, and collaborative experiments in the HED and nuclear nonproliferation application spaces. Both laser arms are independently tunable with compressible multipass-amplifier arrays (2.8 J and 0.7 J on target, down to 40 fs pulse duration, repetition rate up to 5 Hz) with the seed-beam split off just after the common CPA stretcher. Stable electron beams, Betatron x-rays (keV, broadband) and Thomson scattered photons (MeV, quasimonoenergetic) have been established. The facility is available to the scientific community through LaserNetUS; successful user experiments have been conducted, e.g., recording electron deflectometries and phase contrast images of hydrodynamic shocks with Betatron x-rays. The first high-resolution radiographs with the MeV photon source from Thomson scattering have been recorded, paving the way for further scientific developments and applications including nuclear nonproliferation. Ongoing upgrades include arm-independent temporal and spatial profile pulse control, pointing stability enhancements through fast active feedback, and single shot MeV spectrum characterization. This talk covers the experimental system, highlights recent experiments, and describes ongoing efforts to improve system performance. |
Monday, November 8, 2021 10:54AM - 11:06AM |
BO04.00008: BELLA Petawatt Second Beamline Commissioning and Experimental Plans Marlene Turner, Anthony J Gonsalves, Stepan S Bulanov, Carlo Benedetti, Davide Terzani, Jeroen van Tilborg, Kei Nakamura, Carl B Schroeder, Zachary Eisentraut, Cameron R Geddes, Nathan Ybarrolaza, Greg Mannino, Jonathan S Bradford, Haris Muratagic, Csaba Toth, Lieselotte Obst-Huebl, Tyler Sipla, Arturo Magana, Joe Riley, Paul M Centeno, Thorsten Stezelberger, James Vuong, Lucas Kistulentz, Gregory L'Heureux, Gregory Scharfstein, Eric Esarey The petawatt (PW) laser system of the BErkeley Lab Laser Accelerator (BELLA) has been successfully performing high intensity laser plasma interaction experiments since 2012, with emphasis on laser plasma wakefield acceleration (LPA). In 2021, the installation and commissioning of a second laser beam transport line (2BL) from the laser table to the target chamber has been completed. The PW laser pulses are split before compression, enabling two independently adjustable high intensity laser pulses in one target chamber with up to ~40J total energy. The completion of the BELLA PW 2BL enables the next generation of LPA experiments, such as high-efficiency staging, laser-driven waveguides for increased electron beam energy, and positron acceleration. We will give an overview of the 2BL capabilities and discuss the upcoming and potential experiments that are enabled by this new beamline. |
Monday, November 8, 2021 11:06AM - 11:18AM |
BO04.00009: Laser-plasma accelerator optimization through active stabilization of the 100-TW-class high-power laser delivery to focus Curtis Berger, Fumika Isono, Jeroen van Tilborg, Samuel Barber, Tobias M Ostermayr, Carl B Schroeder, Eric Esarey The control of position and pointing angle of high-power laser pulses at focus allows for stability and tunability of applications such as laser-plasma acceleration, and other high-intensity-laser and laser-plasma interactions. While recently we have published a non-perturbative high-power diagnostic based on a rear-surface wedged final steering optic [Isono et al. High Power Laser Sci. Eng. 9, e25 (2021)], we now present concepts and experimental progress on complimenting this diagnostic with active stabilization for both position and angle. The availability of a kHz non-amplified pulse train in conjunction with the amplified 1 Hz pulses will be discussed in the context of active feedback concepts. Improvements to laser-plasma acceleration enabled with these new control capabilities are investigated. |
Monday, November 8, 2021 11:18AM - 11:30AM |
BO04.00010: Staging of laser-based plasma accelerators using tape-based plasma mirrors Joshua Stackhouse, Anthony J Gonsalves, Marlene Turner, Lieselotte Obst-Huebl, Kei Nakamura, Matthew Sahim, Carl B Schroeder, Jeroen van Tilborg, Cameron R Geddes, Eric Esarey Laser-based plasma accelerators (LPAs) provide the ability to achieve acceleration gradients for electrons and positrons orders of magnitude greater than conventional accelerators. Previous LPA experiments with this setup have demonstrated electron beams accelerated up to 8 GeV. However, the maximum electron energy that can be reached in a single stage is limited by the energy of the drive laser pulse. In order to produce higher energy electron beams with lasers of reasonable size, multiple acceleration stages must be coupled together. In order to maximize acceleration gradient, the laser energy must be coupled into each acceleration stage in as short a distance as possible. This means maximizing the laser fluence on the coupling optic, and due to the damage threshold of conventional optics, a plasma mirror is required. Initial low electron-capture-efficiency staging experiments at the 100MeV-level were performed using a replenishing tape-based plasma mirror. In this talk we will present analysis on the suitability of this technology for driving high efficiency multi-GeV stages. Tape flatness was measured and improved, and a pointing feedback system implemented to allow for efficient laser coupling into LPA stages. This will enable the demonstration of staging with multi-GeV electron acceleration in two acceleration stages, and lay the foundation for higher energy LPAs. |
Monday, November 8, 2021 11:30AM - 11:42AM |
BO04.00011: Phase-space reconstruction of the electron beam via modulated angular spectrum of the electron beam in a laser wakefield accelerator Yong Ma, Matthew J. V Streeter, Felicie Albert, Nicholas Bourgeois, Silvia Cipiccia, Jason M Cole, Stephen J Dann, Elias Gerstmayr, Isabel Gonzalez, Andrew Higginbotham, Amina E Hussein, Dino Jaroszynski, Katerina Falk, Brendan Kettle, Karl M Krushelnick, Nuno Lemos, Nelson Lopes, Caroline Lumsden, Olle Lundh, Stuart P.D. Mangles, Zulfikar Najmudin, Pattathil Rajeev, Mohammed Shahzad, Michal Smid, Rome Spesyvtsev, Daniel R Symes, G. Vieux, Jonathan Wood, Alexander G Thomas Laser wakefield accelerator (LWFA) is promising for many applications such as future TeV e+-e- colliders and advanced radiation sources. These applications require high beam quality in terms of energy spread, emittance, beam charge, shot-to-shot stability, dark current, etc. To achieve high beam qualities, one has to precisely control the beam dynamics in LWFA, which in turn can only be done with the detailed diagnostic of the beam dynamics. This is difficult owing to the highly nonlinear acceleration process and the sub-μm, sub-fs spatial-temporal diagnostic requirements. We report on a phasespace diagnostic and reconstruction of the electron beam dynamics via the experimental observation of fishbone-like periodic modulated angular spectra of the electron beams. This is a result of the direct interaction between an electron beam and the laser driver in a laser wakefield accelerator. An analytical model describes the betatron oscillations and the constant longitudinal acceleration to explain the experimental observation. The analytical model, assisted by a machine learning algorithm, can fully reconstruct the electron beam's transverse and longitudinal momentum distribution, the bunch shape, the pulse duration and the energy chirp. More importantly, it reveals the slice energy spread of the electron beam. The experimental observation and the theoretical model are confirmed by Particle-in-Cell simulations. |
Monday, November 8, 2021 11:42AM - 11:54AM |
BO04.00012: Laser steepening controls polarization-dependent electron self-injection in laser plasma accelerators Jihoon Kim, Vladimir Khudik, Gennady Shvets An intense laser pulse propagating inside plasma can form a shock-like steepened front. After the onset of pulse steepening, bubble formed by the laser pulse undergoes expansion and transverse undulation [1]. Bubble undulation is periodic in time and is controlled by laser polarization and Carrier-Envelope-Phase (CEP) [2]. Expansion and undulation can modify electron trapping from background plasma: expansion can help trap electrons, but undulation can both enhance or suppress trapping. Their interplay gives rise to a complex trapping process periodic in space and time controlled by laser pulse CEP and polarization. By changing laser polarization from linear to circular, structure of the injected electron beam can be changed from a fs-scale modulated beam or a flat current profile. Furthermore, the high charge few nC injected electrons leads to efficient energy conversion from the laser pulse to injected electrons. This injection mechanism is amenable to several existing TW-scale few-cycle to multi-cycle laser pulses. |
Monday, November 8, 2021 11:54AM - 12:06PM |
BO04.00013: A multi-sheath model for highly nonlinear plasma wakefields Thamine Dalichaouch, Xinlu Xu, Adam R Tableman, Fei Li, Frank S Tsung, Warren B Mori High gradient, high efficiency acceleration and high quality beam generation are important goals of plasma-based acceleration (PBA). To understand these processes, an accurate description of nonlinear wakefields is required. These wakefields can be excited by intense particle beams or lasers pushing plasma electrons radially outward and forward, creating an ion bubble surrounded by a sheath of electrons characterized by the source term S=−(ρ−Jz/c)/enp. Previously, the sheath source term was described as positive-definite, resulting in a positive-definite wake potential. In reality, the wake potential is negative at the rear of the bubble, which is important for accurate self-injection and beam loading models. To account for this, we present an improved multi-sheath model in which the plasma source term, S, can be negative in regions outside the ion bubble [1]. Using this model, a new expression for the wake potential and a modified differential equation for the bubble radius are obtained. Numerical results obtained from these equations are compared to PIC simulations for unloaded and loaded wakes. The new model is shown to provide accurate predictions of trailing bunch current profiles that flatten plasma wakefields. It is also used to design a trailing bunch for a desired longitudinally varying wakefield. Beam loading results for laser wakefields are also presented. |
Monday, November 8, 2021 12:06PM - 12:18PM |
BO04.00014: Laser Wakefield Acceleration from Nebular-Shaped Plasmas Itamar Cohen, Talia Meir, Yonatan Gershuni, Michal Elkind, Assaf Levanon, Ishay Pomerantz Intense lasers made available for the first-time high-energy electron sources at university scale laboratories. For the past two decades, the community focused on optimizing the accelerated beam quality in terms of higher energy, sharper energy spectrum, and improved repeatability. |
Monday, November 8, 2021 12:18PM - 12:30PM |
BO04.00015: Source size analysis of x-rays driven by laser wakefield acceleration Isabella M Pagano, Paul M King, Andrea Hannasch, Thanh Ha, Alejandro Franco, Hai-En Tsai, Tobias M Ostermayr, Robert E Jacob, Sahel Hakimi, Anthony J Gonsalves, Jeroen van Tilborg, Carl B Schroeder, Eric Esarey, Cameron R Geddes, Mario Balcazar, Yong Ma, Alec G.R. Thomas, Carolyn C Kuranz, Hernan J Quevedo, Michael M Spinks, Constantin Aniculaesei, Nuno Lemos, B M Hegelich, Michael C Downer, Felicie Albert We developed an analytical tool based on the Fresnel Diffraction formalism, to determine the X-ray source size of Laser Wakefield (LWFA) generated X-rays, in several regimes (Self Modulated, Nano-particle enhanced, Blowout LWFA) and at multiple facilities (Berkeley Lab Laser Accelerator, Texas Petawatt, and Jupiter Laser Facility). This analysis will help us understand the properties of these X-ray sources for use in radiography in High Energy Density (HED) science applications. For our analysis, a razor blade was imaged using the respective X-ray sources, and from the diffraction pattern cast onto the detector, we can fit a model diffraction pattern to determine the x-ray source size. This work primarily focuses on Betatron X-rays, and Inverse Compton Scattering and Bremsstrahlung X-ray sources were also examined. Due to the different pulse durations and laser parameters available at different facilities, it is important to examine various regimes of LWFA when designing an X-ray diagnostic to be used for radiography of HED phenomena. We will show the distinction between X-ray source sizes generated by different LWFA regimes, and at different laser facilities. |
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