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 PO08: Intense Radiation and Secondary Particle SourcesLive Streamed
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Chair: Peng Zhang, Michigan State University Room: 402 ABC |
Wednesday, October 19, 2022 2:00PM - 2:12PM |
PO08.00001: High Harmonic Generation from ultra-relativistic 400nm Laser Solid Interactions Hunter G Allison We present experimental results of high harmonic generation generated by high contrast, 400 nm short pulse laser beams with solid density targets and on-target intensities of up to1021 W/cm2. Harmonic spectra were measured as a function of targets which varied in composition and thickness. Particle-in-cell simulations were performed showing the relationship between target parameters and emitted x-ray and electron beams. |
Wednesday, October 19, 2022 2:12PM - 2:24PM |
PO08.00002: Coherent radiation from kinetic instabilities in radiation reaction dominated domain Pablo J Bilbao, Luis O Silva Coherent radiation emission can be prompted by the presence of unstable distributions under the appropriate plasma conditions. Unstable ring momentum distributions have been proposed as seeds for the electron cyclotron maser instability [1] and the Ion-channel laser [2] mechanisms. Expanding on recent work [2], we show that radiation reaction cooling can reshape the momentum distribution of relativistic beams into a ring distribution. This is due to the differential radiation cooling the beam particles experience in the presence of intense fields, in particular in ion channels [3]. Our analytical model is compared with Particle-in-cell simulations, using OSIRIS [4,5], and we determine the properties of the subsequent radiation emission. |
Wednesday, October 19, 2022 2:24PM - 2:36PM |
PO08.00003: High-Power, High-Energy Laser-Solid THz Generation with Foil and Wire Targets Gerrit Bruhaug, Hans Rinderknecht, Mingsheng Wei, Gilbert W Collins, J. Ryan Rygg, Yiwen E, Kareem Garriga, Xi-Cheng Zhang, Roger J Smith, Ales Necas, Kan Zhai Ultraintense (>1018 W/cm2) laser–plasma interactions have been found to be efficient (>0.1%) sources of THz radiation using a wide variety of solid targets. The most common THz generation target is a tens-of-mm-thick foil, but more recent work has shown tens-of-mm-radius wires to also be targets of interest for higher laser-THz conversion efficiency. Results from experiments using the joule-class Multi-Terawatt laser and kilojoule-class OMEGA EP laser to generate millijoule and greater THz sources are reported and compared to models of THz production from foil and wire targets. Future uses of these terawatt-class THz sources are discussed with an emphasis on extreme light–matter interactions. |
Wednesday, October 19, 2022 2:36PM - 2:48PM |
PO08.00004: 3-D CFDTD PIC Simulation of a Dielectric-loaded Rectangular Waveguide for THz Wave Generation Ming-Chieh Lin, David N Smithe The micro-fabrication of small planar or rectangular waveguide components for use at very high frequencies in millimeter and up to THz wave ranges has attracted a lot of attention in recent decades due to advanced semiconductor manufacturing technologies. A homogenous metallic waveguide is a fast wave structure while a slow wave structure (SWS) can be obtained with employing a corrugation or dielectric filling in the waveguide. For a dielectric loaded waveguide, the normal modes are not, in general, either pure transverse electric (TE) or transverse magnetic (TM) modes, but rather combinations of these modes, namely longitudinal section electric (LSE) and longitudinal section magnetic (LSM) modes having no E and H components normal to the interface, respectively. It had been proposed to use a dielectric-loaded rectangular waveguide as an accelerating structure. In this work, we propose to use the partially filled rectangular waveguide as a SWS for THz wave generation (reversed acceleration) since the same beam wave interaction can be employed. The field analysis of the SWS is conducted using a 3-D conformal finite-difference time-domain (CFDTD) method and the corresponding dispersion relations of TE, TM, LSE, and LSM modes are calculated. The beam wave interaction for THz generation is studied using the 3-D CFDTD particle-in-cell simulations. The detailed simulation model and calculation results will be presented. |
Wednesday, October 19, 2022 2:48PM - 3:00PM |
PO08.00005: Coherent radiation from superluminal plasma wakefields Bernardo F Malaca, Miguel Pardal, Dillon Ramsey, John P Palastro, Jacob R Pierce, Kathleen Weichman, Warren B Mori, Ricardo A Fonseca, Igor A Andriyash, Jorge Vieira Light sources based on plasma accelerators rely on the oscillations of relativistic electron bunches in nonlinear plasma waves (e.g., betatron radiation). However, the plasma wakes themselves can also radiate if their amplitude is sufficiently high. This suggests a broader radiation concept based on emission from collective excitations. Collective excitations (often referred to as quasiparticles) are a broadly adopted concept in condensed matter physics. Here, we use it to describe any collective dynamics that exhibit wave-like properties, such as plasma wakefields. We show that the trajectory of the collective excitation defines the coherence properties of the radiation just as if it were a point-like charge. We demonstrate with theory and simulations, using the radiation diagnostic for OSIRIS (RaDiO), that a superluminal nonlinear wakefield generates an optical shock at the Cherenkov angle, just like a superluminal particle. We find that the radiated intensity scales with the number of electrons squared for frequencies of up to a few hundred times the plasma frequency, which shows that the emission is superradiant, making this a promising plasma-based source of temporally coherent radiation. |
Wednesday, October 19, 2022 3:00PM - 3:12PM Author not Attending |
PO08.00006: Fast neutron yield from relativistic irradiation of micron scale plumes generated via microfluidic surface wave acoustic nebulizer Nicholas J Peskosky, John Nees, Karl M Krushelnick Reduced mass targets consisting of gas-phase clusters, droplets and microjets have all been successfully employed as sources of energetic ion beams driven through intense laser plasma interactions. A high-brightness tabletop neutron source (107-9 n/sr/sec) is desirable for radiographic applications but would require scaling targets to multi-kHz operation with TW/kW drivers. Practical realization thus far has been limited by complex cryogenic systems and rigorous demands placed on vacuum throughput. Relativistic irradiation of atomized deuterated droplets in a pitcher-catcher configuration results in favorable D(d,n)3He fusion cross sections in the mixed regime between coulombic explosion and target normal sheath acceleration. Our experiments explore this transitional mass-limited target regime and present the first demonstration of an in-chamber aerosol plume generator based on standing wave surface acoustic wave nebulization (SW-SAWN) with solid-state LiNbO3 devices. Deuteron acceleration from 1-4 μm droplet plumes is explored with relativistic (>1018 W/cm2) Ti:Sa pulses at ½ kHz. Isotropic yield from D-D fusion is characterized via fast neutron time-of-flight. Pulse chirp and pure helium backfill are investigated as parameters enabling vacuum-free source operation at near atmospheric pressures. |
Wednesday, October 19, 2022 3:12PM - 3:24PM |
PO08.00007: Intense broadband terahertz pulses produced in relativistic laser-plasma interaction in the mid-IR Ela M Rockafellow, Stefan K Waczynski, Daniel Woodbury, Robert M Schwartz, Howard M Milchberg Broadband, ultrashort THz pulses are of increasing interest for applications. We present results from particle-in-cell simulations demonstrating that mid-infrared laser-driven near-critical density plasmas can have extremely high THz conversion efficiency. Specifically, a tightly focused 25 mJ, 80 fs λ=3.9μm pulse in a fully ionized hydrogen gas jet plasma gives up to 8% conversion efficiency, generating a ~2 mJ 1-30 THz pulse. These simulations show that the frequency conversion is mainly due to downshifting from co-propagation of the mid-IR pulse and its self-generated plasma wake bubble, with a smaller contribution from coherent transition radiation by laser wakefield-accelerated electrons exiting the gas jet. The maximum conversion efficiency is strongly correlated with a narrow range of peak plasma density and propagation length that avoid bubble collapse. |
Wednesday, October 19, 2022 3:24PM - 3:36PM |
PO08.00008: High-Energy Two-Color Terahertz Generation Tanner T Simpson, Jeremy Pigeon, Mervin Lim Pac Chong, Robert Boni, Dillon Ramsey, Kathleen Weichman, Dustin Froula, John P Palastro A laser pulse composed of a fundamental and properly phased second harmonic exhibits an asymmetric electric field that can drive a time-dependent current of photoionized electrons. The current produces a near-single-cycle burst of terahertz radiation. Experiments using ~1-TW ultrashort laser pulses observe optimal THz energies (~10-mJ) when the “two-color” pulse undergoes filamentary propagation in low-pressure gas1. Here we use simulations to investigate the optimal conditions for two-color THz generation driven by >100-TW ultrashort laser pulses. Simple scalings indicate that the number of photoionized electrons is independent of gas pressure. As a result, use of a low-pressure, small nonlinear refractive index, high-ionization-potential gas such as helium can mitigate multiple filamentation of the high-power pulse while strengthening the field experienced by electrons at the instant of ionization, thereby increasing the current and THz energy. A high-energy (~1-mJ), THz source driven by >100-TW pulses would enable access to a novel physics regime in which bound electron nonlinear optics and relativistic plasma physics coexist.
1Y.-J. Yoo, D. Jang, and K.-Y. Kim, Opt. Express 27, 22,663 (2019).
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Wednesday, October 19, 2022 3:36PM - 3:48PM |
PO08.00009: Generating tunable frequency upshifts in mid-infrared laser pulses using relativistic ionization fronts Mitchell Sinclair, Yipeng Wu, Chaojie Zhang, Audrey Farrell, Zan Nie, Noa Nambu, Kenneth A Marsh, Navid Vafaei-Najafabadi, Irina Petrushina, Mikhail Polyanskiy, Igor Pogorelsky, Marcus Babzien, Mikhail Fedurin, Karl Kusche, Mark A Palmer, Chandrashekhar Joshi Tunable lasers are a well-developed field of study with a broad range of applications, including coherent IR spectroscopy, high-harmonic generation, and single cycle and attosecond pulse generation. We present theoretical, computational, and experimental progress towards a novel method of frequency upshifting that allows us to continuously tune a CO2 laser pulse from ωo to 2ωo - i.e. over a spectral region known as the molecular fingerprint region because many common molecules have vibrational-rotational transitions here. In our concept, a mid-infrared CO2 laser pulse is sent into a gas or partially ionized plasma while a counter-propagating higher-intensity Ti:Sapphire laser drives a time-dependent change in refractive index by creating a step-like relativistic ionization front which passes through the CO2 laser pulse. Simulations with the particle-in-cell (PIC) code OSIRIS show that the upshifted wavelength can be tuned in a broad range with high efficiency by changing the plasma density from a tenth to four times critical density of the CO2 light in a stationary plasma. We are currently conducting an experiment at the Accelerator Test Facility (ATF) at Brookhaven National Laboratory to demonstrate this new method. By using a 2-3 picosecond CO2 laser pulse with intensities ranging from 140-250 TW/cm2, we expect to measure single-shot tunable upshifts between 9.2 μm to 4.6 μm. We have designed a single-shot spectrometer for the transmitted radiation that is capable of characterizing the energy, frequency, and bandwidth of the upshifted pulse. This experimental work is being performed in collaboration with Stony Brook University and ATF. |
Wednesday, October 19, 2022 3:48PM - 4:00PM |
PO08.00010: A compact laser-plasma based setup for positron production and collection Davide Terzani, Carlo Benedetti, Stepan Bulanov, Carl B Schroeder, Eric H Esarey Development of compact, laser-plasma acceleration (LPA)-based sources for positrons is a key step in the R&D effort towards development of a TeV collider. The conventional production and collection schemes of positron beams cannot be easily transferred to an LPA setup. This is mainly due to the large distance required to transport particles from the production to the acceleration point and the inherently small transverse acceptance of the LPA. For such reasons, positron production schemes compatible with a plasma-based accelerator are still lacking. In this work, we present a compact, laser-based scheme for the production of positron beams. Positrons are produced via pair decay of the Bremsstrahlung radiation generated when a multi-GeV, laser-plasma accelerated electron beam interacts with a high-Z solid target. We explore the possibility of using the back of the target itself as a plasma mirror for an incoming laser, in order to generate a plasma wave able to trap and accelerate positrons as soon as they leave the target. A realistic phase-space distribution for the positrons is obtained by modeling the electron beam interaction with the solid target using the Monte Carlo code Geant4. We then study the trapping and acceleration efficiency of the subsequent laser-plasma accelerator. |
Wednesday, October 19, 2022 4:00PM - 4:12PM |
PO08.00011: Quantum pathways interference in photoemission from metals induced by two-color lasers with a dc bias Yang Zhou, Peng Zhang Coherent control of photoemission from metals by two-color lasers has drawn great interest for its flexibility in manipulating ultrafast electron dynamics. Here, we analyze the quantum pathways interference in two-color laser induced photoemission, using an exact analytical solution of the time-dependent Schrödinger equation [1,2]. The theory includes contributions from all possible quantum pathways and interferences among them. Effects of laser and dc bias fields on the weight of each pathway and the interference terms are studied. Increasing the intensity ratio of the second harmonic to fundamental lasers results in more contribution from multicolor pathway and the single-color pathway of absorption of 2ω-photons, and therefore stronger interference between them and increased visibility >95%. Increasing bias voltages shifts the dominant emission to processes with fewer photon absorption, which sequentially decreases the interference between the ω- and the 2ω-pathways, and between single-color and multicolor pathways. Our study provides insights into the underlying physics of coherent control of two-color photoemission. |
Wednesday, October 19, 2022 4:12PM - 4:24PM |
PO08.00012: A high-intensity laser-driven positron source Stepan Bulanov, Carlo Benedetti, Davide Terzani, Carl B Schroeder, Eric H Esarey It is widely accepted that the next lepton collider beyond a Higgs factory would require center-of-mass energy of the order of up to 15 TeV. Since, given reasonable space and cost restrictions, conventional accelerator technology reaches its limits near this energy, high-gradient advanced acceleration concepts are attractive. Advanced and novel accelerators (ANAs) are leading candidates due to their ability to produce acceleration gradients on the order of 1–100 GV/m, leading to compact acceleration structures. However, intermediate facilities are required to test the technology and demonstrate key subsystems. A 20-100 GeV center-of-mass energy ANA-based lepton collider can be a possible candidate for an intermediate facility. There is a number of questions that need to be addressed in the course of designing such a facility. One of the most important is the positron beam generation, capture, and acceleration. Here we present a scheme based on an electron beam interaction with a high intensity laser pulse, where a succession of multiphoton Compton and Breit-Wheeler processes leads to the positron beam generation. |
Wednesday, October 19, 2022 4:24PM - 4:36PM |
PO08.00013: Detecting Nonlinear Breit-Wheeler Pairs at CALA Felipe Cezar Salgado, Katinka v. Grafenstein, Daniel Seipt, Stefan Karsch, Matt Zepf One of the most intriguing physics processes that remain untested is the single-step electron-positron pair production via quantum-vacuum fluctuations described by the nonlinear Breit-Wheeler process. The virtual pairs from the vacuum fluctuations can be turned into real particles by applying electric fields above the Schwinger limit of 1.3 x 1018 V/m. Despite the advent of high-intensity lasers, the critical limit is still far beyond the technologically achievable, however, such fields can be reached in the rest frame of the created pairs after the collision of high-energy γ-ray photons with the highly intense laser beam. |
Wednesday, October 19, 2022 4:36PM - 4:48PM |
PO08.00014: A robust scheme to obtain high charge (∼100 nC) relativisitic (> GeV) electron beams with PW lasers through DLA Robert Babjak, Marija Vranic, Louise Willingale, Alex V Arefiev Direct laser acceleration (DLA) has a potential to provide high-charge electron bunches exceeding energies predicted by the ponderomotive scaling. In recent years, ∼100 MeV electrons have been observed in experiments from DLA. Our calculations and particle-in-cell simulations show the path how to increase the energy and the injected charge for near-future laser technology. Maximum energy the electrons can gain depends on the laser intensity, plasma density and the width of the ion channel. For the case of luminal laser pulse propagation in plasma (e.g. low density) the theoretical analysis predicts that the maximum allowed electron energy increases with the plasma density. However, high plasma densities lead to strong dephasing and consequent decrease of the achieved electron energy. We propose how to achieve multi-GeV electrons using near-critical targets and future generation of laser pulses using relativistic laser intensities. Under such conditions, enabled by multipetawatt laser facilities, electrons could reach energies up to several GeV with hundreds of nC of charge. The high charge content within a few micrometer volume will be especially important if these beams are going to be used for QED cascade seeding or to generate gamma-rays in laser-electron collisions. |
Wednesday, October 19, 2022 4:48PM - 5:00PM |
PO08.00015: High Energy Back-lighting Coupled with an Offset and Shielded Collecting Optic Shahab Khan, Patrick L Poole, David A Martinez, Daniel H Kalantar, Andrew G MacPhee, Scott Wilks, Andreas J Kemp At the National Ignition Facility (NIF), we aim to radiograph rapidly changing, complex, and dense objects for several research goals. This requires a small high-energy and bright x-ray source. The Advanced Radiographic Capability (ARC) at the NIF and the Omega Extended Performance (EP) laser at the Laboratory for Laser Energetics (LLE) provide short pulse, high energy laser beams capable of irradiating backlighter foils, blocks, or wires to produce intense, high-energy x-ray (> 100keV) pulses. To enhance the coupling of the laser energy to the backlighter, a collecting optic shaped as a parabolic cone or a parabolic u-pipe has been employed. In most of these configurations, the optic is in direct contact with the backlighting material which results in the optic becoming an extended x-ray emitting source. In imaging applications where the resolution is a vital consideration and the detector responds to the x-rays emitted by the optic, an alternate setup is required that mitigates the signal from the optic. Here, we will detail a new configuration where the compound parabolic concentrator (CPC) optic is offset from a Tungsten wire backlighter and a Tantalum shield blocks the signal emanating from the CPC. Using the results from a series of experiments at Omega EP, we narrow the parameters necessary for a 20µm resolution x-ray source enhanced with a collecting optic. |
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