Bulletin of the American Physical Society
56th Annual Meeting of the APS Division of Plasma Physics
Volume 59, Number 15
Monday–Friday, October 27–31, 2014; New Orleans, Louisiana
Session BO5: Ion Acceleration, and Neutron Sources |
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Chair: Louise Willingale, University of Michigan Room: Galerie 2/3 |
Monday, October 27, 2014 9:30AM - 9:42AM |
BO5.00001: Towards Spectral Control of Laser-Driven Ion Beams Generated in the Relativistic Transparency Regime Juan C. Fernandez, D.C. Gautier, C. Hamilton, C. Huang, S. Palaniyappan Until recently, experiments on the LANL Trident laser in the relativistic transparency regime have demonstrated efficient, volumetric acceleration of the bulk target ions to high energies by the laser-plasma interaction, but with broad ion-energy distributions. That ion acceleration mechanism (Breakout Afterburner) is intrinsically capable of producing quasi-monoenergetic ion-energy distributions. However, there are processes responsible for energy spread, both during the laser-plasma interaction with present-day experimental conditions, as well as during the subsequent transport of the beam, driven by expansion of the co-moving hot-electron population. Strategies to counter such spread are discussed. Furthermore, our work to understand the recent observation of efficiently-generated, quasi-monoenergetic, $\approx $ 150 MeV Al-ion beams indicates that the dynamics immediately following the laser-plasma interaction can be quite important and beneficial. It has uncovered a new strategy, i.e., using plasma-electron dynamics to increase the ion energy and to decrease its spread. This presentation thus motivates and frames two companion talks on these laser-driven Al-ion beams by Palaniyappan et al. and Huang et al. in this conference. [Preview Abstract] |
Monday, October 27, 2014 9:42AM - 9:54AM |
BO5.00002: Magnetic electron trapping generates efficient quasi-monoenergetic ion beam from laser-driven plasmas Sasikumar Palaniyappan, Chengkun Huang, Donald Gautier, Christopher Hamilton, James Cobble, Christian Kreuzer, Rahul Shah, Juan Fernandez Advanced ion accelerators, based on laser-driven plasmas, are potentially revolutionary because not only they are compact and affordable, but they also deliver lower transverse emittance and higher current density relative to conventional accelerators. However, these advanced ion beams still suffer from lower efficiency, lower peak energy, and wider energy spread that makes them unsuitable for many applications. Several pioneering studies, for more than a decade, have improved those beam properties mostly one at a time, but not all of them together. Here we demonstrate a laser-driven ion beam with all those beam properties enhanced simultaneously: laser-driven quasi-monoenergetic aluminum 11$+$ ion beam with 4{\%} conversion efficiency (i.e., the ion beam contains 3J of energy), 165 MeV peak ion energy, and ion energy spread as low as 7{\%} obtained concurrently. The laser-plasma interaction is dominated by a relativistic plasma effect -- called ``relativistic transparency'' -- that enables efficient laser energy absorption by the plasma, followed by plasma channeling and self-generated plasma magnetic field. This combination leads to the improved conditions observed. [Preview Abstract] |
Monday, October 27, 2014 9:54AM - 10:06AM |
BO5.00003: Influence of the strong self-generated magnetic field on ion acceleration during laser-solid target interaction C.-K. Huang, S. Palaniyappan, J.C. Fernandez The interaction of a high intensity laser with a low areal density solid target (including ultra-thin foils and low density foams) is often accompanied by laser breakout and strong longitudinal electron current channel at the backside of the target. The electron current can generates azimuthal magnetic field exceeding hundreds of MegaGauss, which plays an important role in the dynamics of the electrons near the focal volume or those surrounding the current channel. We present fully kinetic, relativistic Particle-In-Cell simulations that reveal the detail dynamics that lead to enhancement to the ion beam as electrons are magnetically trapped and then released when the laser exits the target. Comparison will be made with recent relevant experiments at the LANL Trident facility. We will also discuss how such interaction can be used to produce high energy ions with smaller energy spread and high conversion efficiency that may be useful for a number of applications. [Preview Abstract] |
Monday, October 27, 2014 10:06AM - 10:18AM |
BO5.00004: Energetic ion beams from ultra thin relativistic transparent targets George Hicks, H. Ahmed, N. Dover, J. Fernandez-Tobias, R. Heathcote, S. Kar, C. Kreuzer, D. MacLellan, I. Musgrave, H. Nakamura, M. Notley, W. Shaikh, M. Streeter, M. Borghesi, P. McKenna, D. Neely, J. Schreiber, M. Zepf, Z. Najmudin In high intensity laser solid interactions, going to ultra thin foils allows access to novel regimes of acceleration such as radiation pressure, hole boring and relativistic transparency. We present data from an experiment on the Vulcan Petawatt laser at the Central Laser Facility, UK. We used a 220J, 1ps laser pulse focussed to a 9.5 $\mu$m spot at 0$^\circ$ to accelerate ions from ultra-thin CH foils. The improved OPCPA front end of Vulcan PetaWatt allowed us to obtain energetic protons $>$ 50 MeV from CH foils down to 25nm thickness, without the use of a plasma mirror. Structures characteristic of the radiation pressure acceleration regime, such as a filamented central beam, and an outer ring structure, were produced. Further information about the interaction could be determined from backscattered spectra and transverse optical probing. The experimental observations are supported by 2D particle-in-cell simulations and an analytical model. [Preview Abstract] |
Monday, October 27, 2014 10:18AM - 10:30AM |
BO5.00005: Maximum attainable ion energy in the radiation pressure acceleration regime Stepan Bulanov, Eric Esarey, Carl Schroeder, Sergey Bulanov, Timur Esirkepov, Masaki Kando, Francesco Pegoraro, Wim Leemans Radiation Pressure Acceleration is a highly efficient mechanism of laser driven ion acceleration, with the laser energy almost totally transferrable to the ions in the relativistic regime. There is a fundamental limit on the maximum attainable ion energy, which is determined by the group velocity of the laser. In the case of a tightly focused laser pulses, which are utilized to get the highest intensity, another factor limiting the maximum ion energy comes into play, the transverse expansion of the target. It makes the target transparent for radiation, thus reducing the effectiveness of acceleration. Utilization of an external guiding structure for the accelerating laser pulse may provide a way of compensating for the group velocity and transverse expansion effects. [Preview Abstract] |
Monday, October 27, 2014 10:30AM - 10:42AM |
BO5.00006: Hole-boring radiation pressure proton acceleration at high intensity in near-critical density targets Jinqing Yu, N.P. Dover, Xiaolin Jin, Bin Li, A.E. Dangor, Z. Najmudin We will present high quality proton beams accelerated from hole-boring radiation pressure proton acceleration (HB-RPA) using three-dimension Particle-in-Cell simulation results. Scaling works on proton cut off energy with laser parameters such as laser intensity and laser pulse duration have been studied in detail by two-dimension Particle-in-Cell simulations. Optimal conditions for generating proton beam of narrow energy spread will be discussed. [Preview Abstract] |
Monday, October 27, 2014 10:42AM - 10:54AM |
BO5.00007: Proton Acceleration from Shock Compressed Gaseous Target Michael Helle, Daniel Gordon, Dmitri Kaganovich, Yu-hsin Chen, Anthony Zingale, Antonio Ting We will present experimental results of the acceleration of protons from a near critical density target produced by the collision of two strong shockwave fronts. The target is created by igniting optically driven, counter-propagating hydrodynamic shocks into the flow of a gas jet in vacuum. The colliding shockwaves produce a 50um thick hydrogen gas region with a peak density greater than quarter critical. Preliminary results show proton energies $\sim$ 2 MeV using the 10TW TFL laser system at NRL. 3D PIC simulations of this interaction yield comparable proton energies and show characteristics of Magnetic Vortex Acceleration. This mechanism takes advantage of an inductive accelerating field setup by the strong azimuthal magnetic field produced by electrons accelerating through the back of the target. Further experimental results examining various targets, laser parameters, and ion species will be discussed. [Preview Abstract] |
Monday, October 27, 2014 10:54AM - 11:06AM |
BO5.00008: Experimental Study for the Laser Driven Protons Acceleration with a Circularly Polarized Ultra-short and High-intense Laser Pulse Interaction with Ultra-thin Target Donghoon Kuk, Joel Blakeney, Samuel Feldman, Gilliss Dyer, Bjorn Hegelich, Todd Ditmire When a linearly polarized TW laser pulse interacts with a solid target, the hot electrons generated by the J x B heating lead to charge separation and accelerate ions to multi-MeV. However, this non --adiabatically heated hot electrons result thermal distribution of the accelerated ions. To suppress the thermal effects of the hot electrons, circularly polarized beam incident on an ultra-thin target has been suggested in which the oscillating component of the J x B force is removed. In this paper, we present the experimental study of the circularly polarized 10$^{19}$ W/cm$^{2}$ irradiance beam interaction with few tens of nanometer thickness of PMMA targets. We observe that the circularly polarized beam generates obviously decreased number of hot electrons compared with the linearly polarized beam and that results the different energy spectrum of the accelerated protons. [Preview Abstract] |
Monday, October 27, 2014 11:06AM - 11:18AM |
BO5.00009: Proton energy enhancement in multiple-beam solid foil interaction Marco Swantusch, Juergen Boeker, Rajendra Prasad, Mirela Cerchez, Marie Schroer, Stephanie Brauckmann, Sven Spickermann, Thomas Wowra, Toma Toncian, Oswald Willi Laser driven ion acceleration from solid foils has been a spectacular field of research for more than a decade. The target normal sheath acceleration has been addressed as main mechanism. Recent research has been focused on increasing the proton energy by using multiple laser beams. Understanding the dynamics of multiple beams interaction is relevant for several multi beams high power laser facilties. The multi-MeV ion acceleration in an electrostatic sheath field is investigated by applying two ultrashort laser pulses onto thin foil targets. We resolve for the first time the fs-dynamics of the acceleration mechanism in the ultrashort pulse regime by varying the delay between two laser pulses. The experiments were carried out at the ARCTURUS laser system in D\"{u}sseldorf. Two ultrashort (30 fs) laser pulses were focused onto a 5 $\mu$m thick titanium target to intensities of 10$^{20}$W/cm$^{2}$. The enhancement of the proton energy was significant for the time delay of around 200 fs, between the two pulses. The maximum proton cutoff energy was obtained for the zero time delay. Consequently, this implies that the addition of multiple beams for energy enhancement is most effective while the beams are synchronized. The Particle-In-Cell simulations are in good agreement with our experimental results. [Preview Abstract] |
Monday, October 27, 2014 11:18AM - 11:30AM |
BO5.00010: Increased efficiency of ion acceleration by using femtosecond laser pulses at higher harmonic frequency Jan Psikal, Ondrej Klimo, Stefan Weber, Daniele Margarone, Jiri Limpouch When ultrashort intense laser pulse at higher harmonic frequency irradiates a thin solid foil, the target may become relativistically transparent for significantly lower laser pulse intensity compared to irradiation at fundamental laser frequency. The relativistically induced transparency results in an enhanced heating of hot electrons as well as increased maximum energies and numbers of accelerated ions. Our particle-in-cell simulations indicate the increase of maximum proton energy and of the number of high-energy protons by a factor of 2 after the interaction of an ultrashort laser pulse of maximum intensity $7 \times 10^{21}~\rm{W/cm^2}$ with a fully ionized plastic foil of realistic density and of optimal thickness about $200~\rm{nm}$ when switching from the fundamental frequency to the third harmonics. [Preview Abstract] |
Monday, October 27, 2014 11:30AM - 11:42AM |
BO5.00011: Generation of high-energy monoenergetic heavy ion beams by radiation pressure acceleration of ultra-intense laser pulses B. Qiao, D. Wu, C. McGuffey, F.N. Beg Generation of high-energy monoenergetic heavy ion beams by radiation pressure acceleration (RPA) of intense laser pulses is investigated for the first time. Different from previously studied RPA of protons or light ions, the dynamic ionization of high-Z atoms can self-organize and stabilize the heavy ion acceleration. A self-organized, stable RPA scheme specifically for heavy ion beams is proposed, where the laser peak intensity is required to match with the large ionization energy gap when the successive ionization passing the noble gas configurations [such as removing an electron from the helium-like charge state (Z-2)$^{+}$ to (Z-1)$^{+}$]. Two-dimensional PIC simulations show that a monoenergetic Al$^{13+}$ beam with peak energy 1.0GeV and energy spread only 5{\%} can be obtained at intensity 7 $\times$ 0$^{20}$W/cm$^{2}$ through the proposed scheme. Heavier monoenergetic Fe$^{26+}$ beam at peak energy 17GeV can be obtained by increasing the intensity to 10$^{22}$W/cm$^{2}$. Heavy ion acceleration with the designed laser conditions of Extreme Light Infrastructure (ELI) is also systemically investigated, where both ionization and radiation-radiation effects need to be taken into account. [Preview Abstract] |
Monday, October 27, 2014 11:42AM - 11:54AM |
BO5.00012: Laser Acceleration of Protons Using Multi-Ion Plasma Gaseous Targets and Its Medical Implications Xi Shao, Tung-Chang Liu, Chuan-Sheng Liu, Bengt Eliasson, Wendell Hill, Jyhpyng Wang, Shih-Hung Chen We present an acceleration scheme by applying a combination of laser radiation pressure and shielded Coulomb repulsion in laser acceleration of protons in multi-species gaseous targets. By using a circularly polarized CO$_{2}$ laser pulse with a wavelength of 10 $\mu$m, the critical density is significantly reduced, and a high-pressure gaseous target can be used to achieve an overdense plasma. This gives us a larger degree of freedom in selecting the foil compounds or mixtures, as well as their density and thickness profiles. An 80 MeV quasi-monoenergetic proton beam can be generated using a half-sine shaped laser beam with peak power 70 TW and pulse duration of 150 wave periods. We compared the effects of modifying the thickness and density of the gaseous targets and showed that the compression of the gaseous target affects significantly in the quasi-monoenergetic property of the proton beams. To assess the feasibility of laser-proton cancer therapy with such a proton accelerator, simulations are carried out to model the interaction of protons with water and determine the depth and lateral dose distribution for particle beams produced from PIC simulation. Comparison between the dosage maps of the proton beams produced with different foil densities and thicknesses is also presented. [Preview Abstract] |
Monday, October 27, 2014 11:54AM - 12:06PM |
BO5.00013: An Ultra-Short Pulsed Neutron Source Ishay Pomerantz, Eddie Mccary, Alexander R. Meadows, Alexey Arefiev, Aaron C. Bernstein, Clay Chester, Jose Cortez, Michael E. Donovan, Gilliss Dyer, Erhard W. Gaul, David Hamilton, Donghoon Kuk, Arantxa Lestrade, Chunhua Wang, Todd Ditmire, Manuel B. Hegelich We report on a novel compact laser-driven neutron source with unprecedented short pulse duration (\textless 50 ps) and high flux (\textgreater 10$^{18}$ neutrons/cm$^{2}$/s), an order of magnitude higher than any existing source. In our experiments, high-energy electron jets are generated from thin (\textless 1 $\mu$m) plastic targets irradiated by a petawatt laser. These intense electron beams are employed to generate neutrons from a metal converter. Our method opens venues for enhancing neutron radiography contrast, conducting time-resolved neutron-damage studies at their characteristic evolution time-scales and for creating astrophysical conditions of heavy element synthesis in the laboratory. [Preview Abstract] |
Monday, October 27, 2014 12:06PM - 12:18PM |
BO5.00014: Characterization of short-pulse laser driven neutron source Katerina Falk, Daniel Jung, Nevzat Guler, Oliver Deppert, Matthew Devlin, J.C. Fernandez, D.C. Gautier, M. Geissel, R.C. Haight, B.M. Hegelich, Daniela Henzlova, K.D. Ianakiev, Metodi Iliev, R.P. Johnson, F.E. Merrill, G. Schaumann, K. Schoenberg, T. Shimada, T.N. Taddeucci, J.L. Tybo, F. Wagner, S.A. Wender, G.A. Wurden, Andrea Favalli, Markus Roth We present a full spectral characterization of a novel laser driven neutron source, which employed the Break Out Afterburner ion acceleration mechanism. Neutrons were produced by nuclear reactions of the ions deposited on Be or Cu converters. We observed neutrons at energies up to 150 MeV. The neutron spectra were measured by five neutron time-of-flight detectors at various positions and distances from the source. The nTOF detectors observed that emission of neutrons is a superposition of an isotropic component peaking at 3.5-5 MeV resulting from nuclear reactions in the converter and a directional component at 25-70 MeV, which was a product of break-up reaction of the forward moving deuterons. Energy shifts due to geometrical effects in BOA were also observed. [Preview Abstract] |
Monday, October 27, 2014 12:18PM - 12:30PM |
BO5.00015: Selective Deuteron Acceleration and Neutron Production on the Vulcan PW Laser A.G. Krygier, J.T. Morrison, R.R. Freeman, H. Ahmed, J.A. Green, A. Alejo, S. Kar, L. Vassura Fast neutron sources are important for a variety of applications including radiography and the detection of sensitive materials. Here we report on the results of an experiment using the Vulcan PW laser at Rutherford Appleton Laboratory to produce a nearly pure deuterium ion beam via Target Normal Sheath Acceleration. The typical contaminants are suppressed by freezing a $\mu m$'s thick layer of heavy water vapor ($D_{2}O$) onto a cryogenic target during the shot sequence. Neutrons were generated by colliding the accelerated deuterons were into secondary targets made of deuterated plastic in the pitcher-catcher arrangement. Absolute yields for deuterium ions and neutrons are reported. [Preview Abstract] |
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