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Conference 12579
Laser Acceleration of Electrons, Protons, and Ions VII
25 - 27 April 2023 | Stella (Tue)/Tycho (Wed-Thur)
View Session 
Monday Plenary Session
24 April 2023 • 16:15 - 18:00 CEST | Nadir
PC12577-500
Exploring plasma physics with multi-petawatt laser pulses
(Plenary Presentation)
24 April 2023 • 16:25 - 17:10 CEST | Nadir
Show Abstract +
State-of-the-art multi-Petawatt laser facilities coming online include the Zettawatt Equivalent Ultrashort pulse laser System (ZEUS), a user facility being commissioned at the University of Michigan. The 3-PW pulses will make ZEUS the highest power laser in the USA. This talk will describe the various experimental approaches that can be used to produce ultrashort particle beams and light-sources, as well as their application to study strong-field plasma physics and beyond. One area of interest is to create extremely strong magnetic fields within the hot plasma in the laboratory, so we can study the microphysics likely to be occurring around the most energetic objects in the universe.
PC12579-501
Laser plasma accelerators
(Plenary Presentation)
24 April 2023 • 17:15 - 18:00 CEST | Nadir
Show Abstract +
Laser Plasma Accelerators (LPA) rely on our ability to control finely the electrons motion with intense laser pulses. Such manipulation allows to produce giant electric fields with values in the TV/m exceeding by more than 3 orders of magnitude those used in current accelerator technology. Controlling the collective electrons motion permit to shape the longitudinal and radial components of these fields that can be optimized for delivering high quality electrons beam or energetic photons.
To illustrate the beauty of laser plasma accelerators I will explain the fundamental concepts we recently discovered, and I’ll show the maturity of our approach in delivering particle and radiation beams for societal applications including for radiotherapy with the ebeam4therapy EIC project.
Tuesday Plenary Session
25 April 2023 • 08:50 - 10:30 CEST | Nadir
PC12577-600
Fusion ignition at the National Ignition Facility (Conference Presentation)
(Plenary Presentation)
25 April 2023 • 08:55 - 09:40 CEST | Nadir
Show Abstract +
On December 5th, 2022, the National Ignition Facility in Livermore, California, USA performed the first experiment demonstrating controlled fusion ignition in the laboratory. With a 2.05MJ UV laser drive energy delivered to the target, a neutron yield of 3.15MJ was released by the fusion reactions in the capsule, providing a net target gain of ~1.5×. The results of this experiment will be discussed, along with the decades-long developments in optical materials, laser architectures, target fabrication, and target diagnostics enabling this recent accomplishment. We will discuss the next steps for NIF and provide an outlook on future applications and technologies, including the reinvigorated pursuit of Inertial Fusion Energy.
12571-601
AI and deep learning for microscopy
(Plenary Presentation)
25 April 2023 • 09:45 - 10:30 CEST | Nadir
Show Abstract +
Video microscopy has a long history of providing insights and breakthroughs for a broad range of disciplines, from physics to biology. Image analysis to extract quantitative information from video microscopy data has traditionally relied on algorithmic approaches, which are often difficult to implement, time consuming, and computationally expensive. Recently, alternative data-driven approaches using deep learning have greatly improved quantitative digital microscopy, potentially offering automatized, accurate, and fast image analysis. However, the combination of deep learning and video microscopy remains underutilized primarily due to the steep learning curve involved in developing custom deep-learning solutions.
To overcome this issue, we have introduced a software, currently at version DeepTrack 2.1, to design, train and validate deep-learning solutions for digital microscopy. We use it to exemplify how deep learning can be employed for a broad range of applications, from particle localization, tracking and characterization to cell counting and classification. Thanks to its user-friendly graphical interface, DeepTrack 2.1 can be easily customized for user-specific applications, and, thanks to its open-source object-oriented programming, it can be easily expanded to add features and functionalities, potentially introducing deep-learning-enhanced video microscopy to a far wider audience.
Break
Coffee Break 10:30 - 10:50
Session 1:
Relativistic Plasma Waves and Particle Beams I: Ultraintense X-ray & THz
25 April 2023 • 10:50 - 12:50 CEST | Stella
Session Chair:
Laszlo Veisz, Umeå Univ. (Sweden)
PC12579-1
Generation of intense THz pulses using laser-plasma interactions (Conference Presentation)
(Invited Paper)
25 April 2023 • 10:50 - 11:20 CEST | Stella
Show Abstract +
THz (terahertz) waves have a wide range of important applications in science and technology, but solid-state-based generation of intense THz waves is quite limited. One of methods for generation of intense THz pulses is using a fs laser and plasma. In fact, a strong THz pulse can be generated by focusing an intense fs laser pulse in gas. In our laboratory, we produced intense THz pulses using several methods with a single laser pulse or two laser pulses of different wavelengths. The generated THz pulse forms were diagnosed by THz-TDS (THz time-domain-spectroscopy) and/or a spectral-encoding-based single-shot method. Furthermore, we used the broadband THz pulses for plasma diagnostics. In this experiment, the THz pulses were sent through an inductively-coupled plasma and the transmitted THz wave pulses were analyzed for phase shift. In this way, we obtained the plasma density information successfully, which can be applied for a wide range of plasma density diagnostics. In this talk, those details for laser-plasma-based THz wave generation and applications will be presented.
PC12579-2
Coherent undulator radiation from pre-bunched attosecond bunches produced by a laser wakefield accelerator (Conference Presentation)
(Invited Paper)
25 April 2023 • 11:20 - 11:50 CEST | Stella
PC12579-3
25 April 2023 • 11:50 - 12:20 CEST | Stella
Show Abstract +
A laser electron accelerator using a laser-ablated metallic target has been developed for the applications of compact light sources at high-vacuum and/or high repetition rate. Unlike any plasma targets using gases, the total amount of molecules generated by ablating a ns or ps laser pulse on metal target is too small to change the vacuum level while the electron plasma density is reached the proper level required for laser acceleration through the optical ionization process by high-intensity Ti:Sapphire laser (here, called the main laser). The density enhancement as well as the electron injection in laser acceleration will be different for target elements (aluminum, copper, titanium, and so on).
The ring-type permanent dipole magnet suggested has a periodic modulation of magnetic-field strength along the trajectory due to H-type iron yoke, indicating the possibility of improvement of beam stability and the angular acceptance of injection. We added the hill-valley ratio of ring-type iron pole gap to adjust the modulation strength of the azimuthally-varying magnetic field. The vertical focusing may increase as increasing the hill-valley ratio, at the expense of average field strength.
In this paper, the beam quality and stability depending on the metallic target structure and the magnetic field modulation due to ring-type iron pole structure are presented.
12579-36
High-brightness self-seeded hard x-ray free-electron laser at PAL-XFEL (Conference Presentation)
(Invited Paper)
25 April 2023 • 12:20 - 12:50 CEST | Stella
Show Abstract +
X-ray free electron lasers (XFELs) are capable of producing x-ray beams with intense peak brightness, full transverse coherence, and femtosecond-scale pulse duration through Self-Amplified Spontaneous Emission (SASE). However, the SASE FELs suffer from noisy spikes in time and spectrum due to radiation originating from electron beam shot noise. To overcome these limitations and realize bright, fully coherent FEL sources, self-seeding is a promising solution. In this study, we utilized the forward Bragg-diffraction (FBD) monochromator at PAL-XFEL to generate almost fully coherent hard X-ray self-seeded (HXRSS) free-electron laser (FEL) pulses with an unprecedented peak-brightness and a narrow spectrum. Our HXRSS FEL demonstrated outstanding performance across a photon energy range spanning from 3.5keV to 14.6keV. These findings provide valuable insights for the development of advanced X-ray sources and their applications.
In order to meet the demands of experimental applications such as resonant inelastic X-ray scattering, nuclear resonance scattering, and X-ray Raman spectroscopy, we have developed x-ray energy scanning method utilizing a double crystal monochromator (DCM). This approach offers improved spectral purity and a fully calibrated energy scale. In this study, we will present recent experimental findings on the characteristics of hard X-ray self-seeded FEL at PAL-XFEL. These results have important implications for the advancement of X-ray spectroscopy and related research fields.
Break
Lunch/Exhibition Break 12:50 - 14:00
Session 2:
Relativistic Plasma Waves and Particle Beams II: Emission of Energetic Particles
25 April 2023 • 14:00 - 15:30 CEST | Stella
Session Chair:
Hyyong Suk, Gwangju Institute of Science and Technology (Korea, Republic of)
12579-4
Relativistic electron acceleration from nanotips
(Invited Paper)
On demand | Presented live 25 April 2023
Show Abstract +
We report on the interaction of relativistic intensity (10^20 Wcm^-2) sub-two optical cycle (<5 fs) laser pulses with nanotips. Various properties of accelerated electrons (angular distribution, charge, and electron spectrum) are measured with different intensities and carrier envelope phase. Among others, waveform dependence of the electron propagation direction is observed. Furthermore, comparable or even higher electron energies beyond 10 MeV are detected with lower laser intensity, i.e., longer focusing, than with high intensity. The surprising results are reproduced using Particle-in-cell simulations. These indicate a nanophotonics electron emission from the nanotip followed by vacuum laser acceleration.
12579-5
Method of producing 100 keVs ion beams from a gas jet using two intense laser pulses
(Invited Paper)
On demand | Presented live 25 April 2023
Show Abstract +
Experiments have been undertaken using the VEGA-3 petawatt laser system at the Centro de Láseres Pulsados (CLPU) facility in Salamanca to investigate electron and ion acceleration in under-dense plasma. The respective longitudinal and transverse fields of the ‘bubble’ structure of a laser wakefield accelerator (LWFA) simultaneously accelerates electrons to GeV energies, and ions to 100s keV/u to MeV/u energies. The laser is configured to produce two ultra-intense laser pulses, each with a minimum pulse duration of 30 fs and a variable inter-pulse delay up to 300 fs. The double pulses can superpose or resonantly excite the LWFA bubble to increase the accelerating fields. By focusing the laser beam into a 2.74 mm diameter supersonic jet of He gas, using an F/10.4 parabola, an initial intensity of up to 10^(19)Wcm^(-2) can be realized at focus. This ionises the gas to produce plasma and the imposes a ponderomotive force that creates the LWFA accelerating structures. For backing pressures of 30 - 60 bar, corresponding to plasma densities of 1 - 4 x 10^(19) cm^(-3), the fields of the LWFA can exceed 200 MV/m, which is sufficient to accelerate electrons to GeV energies, and ions to 100s keV/u. This study focuses on ion acceleration in the transverse direction.
He^(+1) and He^(+2) ion spectra have been measured using a Thompson parabola spectrometer and a multi-channel plate detector. He ions with energies up to a few hundred keV/u are observed for both single pulses (5.0 J) and double pulses (5.0 J and 3.6 J, respectively), where the inter-pulse delay is varied between 0 fs and ±~300 fs.
The measured spectra are consistent with numerical simulations. Ions are observed to undergo electron exchange in the neutral surrounding gas, which produces different charge states ions and neutral atoms. The measured spectra are consistent with numerical simulations. Ions are also observed to undergo electron exchange in the neutral surrounding gas, which produces different charge states ions and neutral atoms.
PC12579-6
25 April 2023 • 15:00 - 15:30 CEST | Stella
Show Abstract +
Laser induced plasma acceleration of ion beams has been attracted long time due to its ultrahigh acceleration field, which leads to a compact accelerator in addition to the characteristics of the accelerated ion beams such as high intensity and short pulse duration. There have been enormous efforts to develop the technology along with understanding the underlying mechanisms. However, the ion beam has a characteristic broad or thermal-like energy distributions, which puts a limit in the application of the ion beams. A novel acceleration mechanism, RPA (Radiation Pressure Acceleration) has been considered to overcome such a limit but yet to be demonstrated.
The authors considers a layered target, which composed of a metal layer and a plastic layer, utilizing a bulk electrostatic field diffused into the target from the rear surface of target. Using a 150 TW Ti:Sapphire laser at CoReLS, interesting carbon ions and protons showing non-Maxwellian energy spectra were generated from a copper foil coated with a polymer at the rear side and maximum energy was enhanced by a factor 1.7 compared with a single copper foil. A bulk electrostatic field formed at the metal-polymer interface and multi-species interactions are consider to cause such an energy distribution and enhancement.
Break
Coffee Break 15:30 - 16:00
Session 3:
Relativistic Plasma Waves and Particle Beams III: Plasma Optics
25 April 2023 • 16:00 - 17:30 CEST | Stella
Session Chair:
Bernhard Ersfeld, Univ. of Strathclyde (United Kingdom)
PC12579-7
The role of transient plasma photonic structures in Raman amplification experiments (Conference Presentation)
(Invited Paper)
25 April 2023 • 16:00 - 16:30 CEST | Stella
Show Abstract +
High power lasers have become large because of they are based on low damage-threshold optical media. A more robust and compact medium for amplifying and manipulating intense laser pulses is plasma. Here we demonstrate that a few-millijoule, ultrashort seed pulses interacting with 3.5-J counter-propagating pump pulse in plasma can back-scattering nearly 100 mJ pump energy with high intrinsic efficiency, even when detuned away from the Raman resonance frequency. Scattering occurs off a plasma Bragg grating that is formed by ballistically evolving ions. Electrons bunched by the ponderomotive force of the beat-wave produce space-charge fields that impart phase correlated momenta to ions. Ions and electrons evolve into a volume Bragg grating that backscatters the pump pulse in the direction of the seed pulse. This, ultra-compact, two-step, inertial bunching mechanism can be used to manipulate and compress intense laser pulses. We also observe evidence of stimulated Compton (kinetic) and Raman backscattering. Experiments have been undertaken at the Central Laser Facility, Rutherford Appleton Laboratory using the Gemini laser.
PC12579-8
Analytic modelling of transient plasma photonic structures (Conference Presentation)
(Invited Paper)
25 April 2023 • 16:30 - 17:00 CEST | Stella
Show Abstract +
Density gratings in plasma created using intersecting intense laser pulses can serve as transient photonic structures with interesting optical properties. We present analytical modelling of the formation of such structures and their dispersive properties, in particular birefringence.
PC12579-9
Plasma-based pulse compression for next generation ultraintense lasers (Conference Presentation)
(Invited Paper)
25 April 2023 • 17:00 - 17:30 CEST | Stella
Show Abstract +
Laser pulses with a few petawatt peak power is available from chirped-pulse-amplification, where the compression gratings of meter scale is vulnerable to the damage. For the exawatt or zettawatt lasers, as the diameter of gratings increased to hundreds of meters is challenging, a fundamentally different approach is required. One promising method can be found in plasma physics; as the plasma is damage-free and at the same time, strongly dispersive to electromagnetic waves. By properly designing the plasma structure, the powerful laser pulses can be compressed in a similar way to solid-based grating mirrors. Various methods exploiting the plasma have been investigated: Raman backward amplification, Brillouin amplification, and transient plasma gratings. Here I introduce a totally different idea to obtain high compression ratio with small energy loss. In the new method, a smooth gradient, high density (near-critical) plasma is used. Photons in a long negatively chirped incident pulse are reflected at different position inside the plasma, depending on their frequencies. The path difference of photons leads to concentration of the photons in a narrow region. From one-dimensional simulations, hundreds of times compression was obtained for the intensity orders of magnitude larger than the intensity sustainable by solid state of materials.
Poster Session
25 April 2023 • 17:45 - 19:15 CEST | Meridian Hall
Conference attendees are invited to attend the Optics + Optoelectronics Symposium Poster Session on Tuesday afternoon. Enjoy light refreshments, ask questions, and network with colleagues in your field. Authors of poster papers will be present to answer questions concerning their papers. Attendees are required to wear their conference registration badges to the poster session.
Poster authors, visit Poster Presentation Guidelines for set-up instructions.
Poster authors, visit Poster Presentation Guidelines for set-up instructions.
PC12579-37
25 April 2023 • 17:45 - 19:15 CEST | Meridian Hall
PC12579-38
25 April 2023 • 17:45 - 19:15 CEST | Meridian Hall
Show Abstract +
We are investigating the improvement of the precision of the means of measurement to determine if it is possible to have sufficient sensitivity to the detection of the effects of elementary particles which would be characteristic of dark matter. A particle has been proposed and is called axion. There would be an interaction between the axions and the photons using the Primakoff effect under strong magnetic field. Radio frequencies from 460 to 810 MHz would be assumed to be suitable for the mass of the axion, if it exists. It is then interesting to focus on the piezoaxionic effect. If the frequency of the axions could match the natural frequency of a normal mode bulk acoustic of a piezoelectric crystal, one would expect the piezoaxionic effect to occur. One could then rely on the piezoelectric effect to observe the variations on the resonant frequency which can be read out electrically using the best piezoelectric materials. Through this example of development and applications in detection, we propose to decrypt this subject and to show how multidisciplinary skills are necessary to hope that small fluctuations can be detectable.
12579-39
On demand | Presented live 25 April 2023
Show Abstract +
We present our recent development of a compact liquid target setup and a proof-of-principle demonstration of ion acceleration and X-ray emission at 1 kHz repetition rate.
The target system is based on a high-pressure chromatography pump, which introduces a continuous flow of liquid into the vacuum chamber through a capillary, forming a microjet. After passing the interaction point in vacuum, the liquid is collected by a specially designed catcher system, equipped with a temperature control to prevent freezing and drain water out of the chamber for recycling. In combination with a liquid nitrogen cold trap, it allows to perform experiments at high vacuum. Supplied with deionized water, the developed target is debris-free and demonstrates precise dimensional and positional tolerance.
For plasma production we used a commercial laser capable of producing ultrashort pulses (~45 fs FWHM) of ~6 mJ at 1 kHz repetition rate. With a high-quality OAP the intensity on target reached 1017 W/cm2. The accelerated ion beam was characterized in terms of energy distribution and shot-to-shot stability by time-of-flight solid-state diamond and SiC detectors, demonstrating the cut-off energy up to 170 keV. The X-ray spectrum of the interaction was acquired by a silicon-drift detector in the range from 2 to 40 keV.
PC12579-40
On demand | Presented live 25 April 2023
12579-41
On demand | Presented live 25 April 2023
Show Abstract +
Laser wakefield acceleration is a remarkably efficient method for relativistic electron acceleration that ensures high electric field gradients generated by plasma waves. In this approach, an ultra-short, high-intensity laser pulse propagates through a plasma medium. It has already proven its potential by reaching gradients up to hundreds of GV/m. To further stabilize and control the process of acceleration, a separate source of electrons is widely considered. In order to address this problem, we have performed 3D particle-in-cell simulations using the Smilei code. Several plasma density profiles with different vacuum-plasma transition region and their effect on the external injection were analysed.
Wednesday Plenary Session
26 April 2023 • 08:50 - 10:30 CEST | Nadir
PC12570-700
Nonlinear integrated quantum optics with AlGaAs
(Plenary Presentation)
26 April 2023 • 08:55 - 09:40 CEST | Nadir
Show Abstract +
Photonic quantum technologies are a promising platform for a large variety of applications ranging from secure long-distance communications to the simulation of complex phenomena. Among the material platforms under study, semiconductors offer a wide range of functionalities opening several opportunities for the development of integrated quantum photonic circuits. AlGaAs is particularly attractive to monolithically integrate active and passive components since it combines high second order nonlinearity, electro-optic effect and direct bandgap. In this talk, I will present the work of our team on the generation of quantum states of light in the telecom range with nonlinear AlGaAs chips working at room temperature. The talk will review recent developments on monolithic and hybrid integrated devices, describe the versatility of these systems for the generation and manipulation of quantum frequency states and show their potential for the implementation of flexible entanglement-distribution networks for secure communications.
PC12575-701
Photonic crystal fibres: three decades of novel science
(Plenary Presentation)
26 April 2023 • 09:45 - 10:30 CEST | Nadir
Show Abstract +
Photonic crystal fibres (PCFs)—thin strands of glass with an intricate array of hollow channels running along their length—offer both hollow and solid glass cores, and allow unprecedented control over dispersion and birefringence, ushering in a new era of linear and nonlinear fibre optics, for example: chiral PCF is circularly and topologically birefringent, supporting optical vortices and in some cases strong circular dichroism; through pressure-adjustable dispersion, gas-filled hollow-core PCF provides an elegant means of compressing pulses to single-cycle durations, as well as underpinning a range of unique sources of tunable deep and vacuum ultraviolet light; microparticles optically trapped inside hollow core PCF van be used to sense physical quantities with high spatial resolution; and strong optomechanical effects in solid-core PCF permit stable timing-modulated high harmonic mode-locking at few-GHz repetition rates.
Break
Coffee Break 10:30 - 10:50
Session 4:
Laser Electron Acceleration I
26 April 2023 • 10:50 - 12:40 CEST | Tycho
Session Chair:
Stepan S. Bulanov, Lawrence Berkeley National Lab. (United States)
PC12579-10
Temporal coherence and superradiance in plasma wakefield based light sources (Conference Presentation)
(Invited Paper)
26 April 2023 • 10:50 - 11:20 CEST | Tycho
Show Abstract +
Coherent light sources, such as free electron lasers, provide bright beams for biology, chemistry, physics and advanced technological applications. As their brightness increases, these sources are also becoming progressively larger, with the longest being several km long (e.g. LCLS). Can we invert this tendency, and bring these sources back to thousands of university, hospital, and industry labs? Plasmas accelerator sources are certainly an attractive solution to this question, but only if their brightness increases several orders of magnitude. Drivers with a higher energy and power will increase the photon yield, but such a dramatic improvement depends on the onset of temporal coherence and superradiance.
We intuitively expect superradiance emission when many light emitting particles fit within a radiation wavelength. When this condition is met, all particles radiate coherently as a single giant particle. Instead, here we show that superradiance can occur even when particles are arbitrarily far from each other [J. Vieira et al. Nat. Physics 17, 99 (2021)]. Moreover, by re-analysing the basics of superradiant emission, we explore previously unrecognised configurations leading to superradiance in plasma accelerator based light sources.
We explore these concepts in theory and through particle-in-cell simulations complemented by the Radiation Diagnostic for Osiris (RaDiO) [M. Pardal et al, Comp. Phys. Communs. 285, 108634 (2023)].
PC12579-11
26 April 2023 • 11:20 - 11:40 CEST | Tycho
Show Abstract +
Since they have been proposed, laser-plasma accelerators have interested the scientific community for their ability to generate electric fields exceeding the ones of Linacs and RF cavities. Several efforts have been made in order to produce monochromatic electron beams and to increase their maximum energy, often at the expense of the charge. However, some applications like femtosecond chemistry, radio-biology and industrial radiography do not need monochromatic beams, but rather highly charged ones (i.e., > 1 nC). For some of these applications it is also necessary to reduce the amount of high energy electrons (i.e., > 10 MeV), in order to avoid the activation of materials. Such beams can be produced using high Z gases like Nitrogen and Argon, exploiting the ionization injection of several plasma period.
Here we numerically and experimentally investigate this little-known regime, employing different laser energies, f-numbers and plasma densities. This allowed us to find the conditions to produce electron beams with charges up to tens of nC and exceeding 100 mrad in divergence. We will also show and explain the dependencies of these beams (e.g., their charges and energy spectra) as functions of the aforementioned laser and plasma parameters.
PC12579-12
26 April 2023 • 11:40 - 12:00 CEST | Tycho
Show Abstract +
Electrons can be accelerated to multi-GeV energies by the mechanism called Direct laser acceleration. The acceleration is secured by the resonance between betatron oscillations in the plasma channel and doppler-shifted oscillations in the laser field. We propose the scaling of electron energy that can be achieved by the mechanism as a function of laser intensity and plasma density. The scaling is in good agreement with quasi-3D particle-in-cell simulations. Also, the role of a laser spotsize in the acceleration is demonstrated which allows us to estimate the optimal laser focusing which maximizes electron energy.
12579-13
On demand | Presented live 26 April 2023
Show Abstract +
Electron acceleration by laser pulses with high repetition rate can be used for technical applications. To reach conditions for the wake-field laser acceleration, it was demonstrated recently in experiments that it is beneficial to use near single cycle laser drive pulses with sub-4 fs duration, with narrow waists. To explore possible electron density ramp-up injection as an alternative to ramp-down and ionization injections, we performed numerical simulations of electron bunches generation in the ramp-up region. The PIC code Epoch2D and input parameters near to experiments were used. We assumed thin plasma slabs with super Gaussian density profiles of order 4-80, FWHM about 30 µm. We found that density ramp-up injected bunches can have charges several times higher than those obtained by ionization injection. There can be created a group of up to ten bunches in a sequence of bubbles, with not too mutually different maximum energy and charges. At oblique incidence of drive pulses on steep ramp up profiles, we find significant enhancement of the first bunch charge. For large slant angles -45 or 45 degrees, the bunch charge enhancement is about twenty times. We conclude that the ramp-up injection can be a useful alternative injection on steep enough density profiles.
PC12579-14
26 April 2023 • 12:20 - 12:40 CEST | Tycho
Show Abstract +
Laser wakefield acceleration (LWFA) using laser-ablated metallic plasma targets has been developed for high-vacuum and high-repetition rate operations. Unlike the supersonic gas jet targets or capillary gas discharge target, the ionization effect of metallic ions due to high intensity fs laser increases the ionization diffraction and ionization injection, resulting in larger energy spread with higher charge.
We proposed a structured metal target using two different metals to improve the beam quality. By adding a thin Ti or Cu wire in aluminum target and changing the focal position of fs laser pulse with respect to the position of the thin-layered zone, the injection timing of electrons depleted from ions of thin wire can be adjusted to improve the beam quality. We present and discuss the simulation results depending on the thickness and the position of the thin layer.
*This work was supported by the National Research Foundation of Korea(NRF) grant founded by the Korea government(MSIT). (NRF Grant No. : NRF-2021R1A2C2094300, and RS-2022-0014317)
Break
Lunch/Exhibition Break 12:40 - 13:50
Session 5:
Laser Ion Acceleration I
26 April 2023 • 13:50 - 15:40 CEST | Tycho
Session Chair:
Carlo Maria Lazzarini, ELI Beamlines (Czech Republic)
PC12579-15
Surpassing TNSA performance in laser proton acceleration in the relativistic transparency regime (Conference Presentation)
(Invited Paper)
26 April 2023 • 13:50 - 14:20 CEST | Tycho
PC12579-16
26 April 2023 • 14:20 - 14:40 CEST | Tycho
Show Abstract +
We report on a commissioning experiment exploring laser-driven proton acceleration using the 350 TW Ti:Sapphire beamline at the Scottish Centre for the Application of Plasma-based Accelerators (SCAPA). This includes parametric scans of laser pulse energy, focal spot size and pulse duration, and their influence on the beam of accelerated protons. This study was performed at a repetition rate of 0.1 Hz. We discuss recent developments, including the use of tape targets, online proton and ion diagnostics and data capture that enabled this first proton acceleration experiment to take place at SCAPA. We also report the development of a new pixelated proton beam footprint monitor and spectrometer, and review the next steps in the development of this programme of research at SCAPA.
PC12579-17
26 April 2023 • 14:40 - 15:00 CEST | Tycho
Show Abstract +
Laser-driven ion acceleration has received significant attention over the past two decades as a compact source of ultra-short, high-flux bunches of energetic (tens-of-MeV) ions with wide-ranging potential applications, such as medical oncology, industrial processing and ultrafast imaging. This acceleration is possible due to the high magnitude electric fields, of the order of MV μm−1, produced in plasma irradiated by relativistically intense laser light. Here we investigate laser-driven proton acceleration from ultrathin foil targets that undergo relativistic self-induced transparency (RSIT) and correlate the maximum proton energy and laser-to-proton energy conversion efficiency with the onset time of transparency. This is investigated using 2D and 3D particle-in-cell simulations to explore an intensity range from 1020-1023 Wcm-2, for both linear and circular laser polarisation. This includes evaluating the impact of the temporal contrast of the laser pulse and the influence of the high-field effect of radiation reaction at the highest intensities. Over the full-range of parameters explored, the onset time of RSIT relative to the temporal peak of the laser pulse interacting with the target is found to be a key defining factor in both the maximum proton energies and conversion efficiency.
PC12579-18
26 April 2023 • 15:00 - 15:20 CEST | Tycho
Show Abstract +
High power laser-driven ion acceleration produces bright beams of energetic ions that have the potential to be applied in a wide range of sectors. The routine generation of optimized and stable ion beam properties is a key challenge for the exploitation of these novel sources. We demonstrate the optimization of laser-driven proton acceleration in particle-in-cell simulations controlled by a Bayesian algorithm. Optimal laser and plasma conditions are identified four times faster for two input parameters, and approximately one thousand times faster for four input parameters, when compared to systematic and linear parametric variation. In addition, a non-trivial optimal condition for the front surface density scale length is discovered, which would have been difficult to identify by single variable scans. This approach enables rapid identification of optimal laser and target parameters in simulations, for use in guiding experiments, which has the potential to significantly accelerate the development and application of laser-plasma-based ion sources.
PC12579-19
26 April 2023 • 15:20 - 15:40 CEST | Tycho
Show Abstract +
Ion acceleration by compact laser-plasma sources promises a variety of applications, but reaching the required beam quality parameters demands a high level of understanding and control over the laser-plasma interaction process. Several advanced acceleration schemes, including the Relativistically Induced Transparency (RIT) regime, have been proposed and investigated in search of a stable acceleration regime for proton energies beyond 100 MeV.
Central component in the RIT scheme is the absorption of the electromagnetic laser field by the target and the generated plasma respectively. In joint studies, we experimentally explore these interactions at the onset of transparency at the two laser systems DRACO PW (HZDR) and J-KAREN (KPSI). With our transmission diagnostics, we characterize this onset with respect to the laser temporal profile in order to learn about the sensitivity of laser input parameters to increase the process’s robustness. Using ultra-short, high and low-contrast laser pulses on thin solid density foil targets, we observe high performance proton beams in an expanded foil case. The results of spectral, spatial, and energy analysis of the effects on the transmission and its correlation with the acceleration performance indicate changes in the plasma interaction itself.
Break
Coffee Break 15:40 - 16:00
Session 6:
Laser Electron Acceleration II
26 April 2023 • 16:00 - 17:50 CEST | Tycho
Session Chair:
Gabriele M. Grittani, ELI Beamlines (Czech Republic)
PC12579-20
26 April 2023 • 16:00 - 16:30 CEST | Tycho
Show Abstract +
The extremely high electric fields sustainable by a plasma make the Laser Wakefield Acceleration (LWFA) the most compact technique to generate very highly relativistic electron beams in the GeV regime. The limited repetition rate and low efficiency of this technology has, to date, prevented to unleash its full potential as a unique source for basic research, biomedical applications and high flux sources of secondary radiations as hard X-rays and gamma-rays. In very recent years different works show a new research direction on electron acceleration at 1 kHz repetition rate.
In this talk I will show the laser-driven acceleration of unprecedented, collimated (2 mrad) and quasi-monoenergetic (ΔE/E = 25%) electron beams with energy up to 50 MeV at 1 kHz repetition rate. The laser driver is the in-house developed L1-Allegra multi-cycle (15 fs) 1 kHz OPCPA system, operating at 26 mJ (1.7 TW).
Said innovative results have been achieved in the new Laser Wakefield ALFA platform for user experiments developed at ELI-Beamlines.
The scalability of the driver laser technology and the electron beams reported in this work pave the way towards developing high brilliance X-ray sources for medical imaging, innovative devices for brain cancer treatment and represent a step forward to the realization of a kHz GeV electron beamline.
PC12579-21
26 April 2023 • 16:30 - 16:50 CEST | Tycho
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In hybrid LWFA-driven PWFA (LPWFA) electron beams from a laser wakefield acceleration (LWFA) stage are utilized to drive a plasma wave in a subsequent plasma wakefield acceleration (PWFA) stage for acceleration of witness electron bunches to high energies. Here we present results of an optical induced injection in this hybrid plasma acceleration configuration, where experimental evidence indicates the successful implementation of Trojan Horse injection also known as plasma photocathode. The generated witness beams show improved beam quality, such as lower energy spread compared to the drive electron beam.
PC12579-22
26 April 2023 • 16:50 - 17:10 CEST | Tycho
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High peak current electron beams from laser wakefield accelerators (LWFAs) can excite a high amplitude plasma wave in a subsequent plasma wakefield acceleration (PWFA) stage. The intrinsic short duration of these driver beams enables a new operational regime of PWFAs at plasma densities above 10^18 cm^-3, where femtosecond optical probing can be successfully applied. Here we present experimental results of optical probing of such beam driven wakefields, for different target conditions as well as a dependence on the driver beam properties. The experimental results are supported by 3D particle-in-cell simulations performed with PIConGPU.
12579-23
On demand | Presented live 26 April 2023
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The dynamics of electron injection from a tilted shock front under a laser condition of a0 > 3 and tight focusing (FWHM < 10 microns) laser condition has been studied by numerical simulations. Compared to a regular shock-front injection, the result shows that the injection starts outside the first bubble with a narrow energy spread of < 13 MeV. The charge injected from one side of the bubble significantly increases thanks to the symmetry breaking by the tilted shock front. Their trajectories are more coherent than the un-tilted injection. High brightness and polarized X-rays are expected to be produced by electron beams undergoing betatron oscillation within the wakefield.
PC12579-24
26 April 2023 • 17:30 - 17:50 CEST | Tycho
Session 7:
Laser Ion Acceleration II
27 April 2023 • 09:10 - 10:30 CEST | Tycho
Session Chair:
Stepan S. Bulanov, Lawrence Berkeley National Lab. (United States)
PC12579-25
27 April 2023 • 09:10 - 09:30 CEST | Tycho
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The newly commissioned short focal length, high intensity beamline, named iP2, at the BELLA Center enables frontier experiments in high energy density science. This 1 Hz system provides a focused beam profile of <3 micron in FWHM, resulting in an on-target peak intensity greater than 5e21 W/cm^2, and a pointing fluctuation on the order of 1 micron. A temporal contrast ratio of <1e-14 on the nanosecond timescale is expected with the addition of an on-demand double plasma mirror setup in the near future. This beamline is well suited for studies requiring ultra-high intensity and substantial control over the temporal contrast, such as investigation of novel regimes of advanced ion acceleration and their applications. The recent results from iP2 commissioning experiments will be presented as well as the outlook for in vivo radiobiological studies at ultra-high dose rates. In preparation for an experimental campaign to investigate the magnetic vortex acceleration regime, a series of 3D simulations using the WarpX code were performed to optimize the target design and guide the development of diagnostics. We studied the acceleration performance with different laser temporal contrast conditions at normal and oblique laser incidence angles. The simulation results will be presented along with an overview of the planned experimental setup at iP2.
This work was supported by the U.S. Department of Energy (DOE) Office of Science, Offices of Fusion Energy Sciences (FES) and High Energy Physics, LaserNetUS, and used resources at NERSC under Contract No. DE- AC02–05CH11231 via the award FES-ERCAP0021193 as well as an ALCC award at OLCF (No. DE-AC05– 00OR22725). S. Hakimi was supported by the U.S. DOE FES Postdoctoral Research Program administered by the Oak Ridge Institute for Science and Education (ORISE) for the DOE. ORISE is managed by Oak Ridge Associated Universities (ORAU) under Contract No. DE-SC0014664. All opinions expressed in this paper are those of the authors and do not necessarily reflect the policies and views of DOE, ORAU, or ORISE. WarpX was supported by the Exascale Computing Project (No.17- SC-20-SC), a collaborative effort of two U.S. DOE organizations (Office of Science and the National Nuclear Security Administration).
PC12579-26
27 April 2023 • 09:30 - 09:50 CEST | Tycho
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Intense femtosecond laser – ultrathin foil driven proton beams have unique properties of small source size and low-transverse emittance which make them well suited for static or dynamic radiography with unprecedented temporal and spatial resolution. Recently, laser accelerated deuterons with few hundreds keV energy have been suggested to generate fusion neutrons via D-D and D-T reaction for transmutation of spent nuclear fuel. The development of high yield, low ion energy sources requires extending the calibration of ion diagnostics to and below 100 keV. Here we present a spatial characterization sub-MeV proton beam, along with the calibration of a Thomson ion spectrometer assembly, driven by 12 fs laser pulses with 10^19W/cm2 intensity on target.
PC12579-27
27 April 2023 • 09:50 - 10:10 CEST | Tycho
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The development of laser plasma accelerators has been centred around the optimisation of particle yield resulting from the interaction of high energy, single-shot lasers with very low average power. Here we aim at the already existing, high average power lasers with kHz repetition rate but low pulse energy. In our experiment, the SEA laser of ELI-ALPS provided ultrahigh contrast laser pulses of 12fs pulse duration and 20mJ energy on the 200 nm thick dPE foils. A rotating wheel target system allowed the laser interaction run at 1 Hz repetition rate in bursts of 75 shots. The accelerated deuterons, measured by Thomson spectrometers for each shot, hit a 0.1mm thick, 20 mm diameter deuterated-polyethylene disk. Neutrons were then generated via d+d fusion reaction with a mean energy of 2.45MeV. The neutron events were detected by four plastic scintillators at various angles around the chamber. From the ToF distributions we have concluded that an average of >3000 neutrons were generated in a shot, with a slight anisotropy to the forward direction. The upcoming development of kHz repetition-rate primary-target systems would boost the yield of neutrons in a second, that may exceed which can be achieved with PW class lasers..
PC12579-28
27 April 2023 • 10:10 - 10:30 CEST | Tycho
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With the advent of laser technology, it has become possible to accelerate laser-driven protons up to the energies of tens of MeV, covering a large range of possible multidisciplinary applications (e.g. material science, medicine). One of the most common and reliable diagnostics for the dose and energy characterization of such particles is stacks of Radiochromic Films (RCF). Nevertheless, such detectors demand time-consuming post-irradiation processing and hence can provide the necessary information only “offline” after the laser shot. In recent years, however, it has become possible to reach a high repetition rate (>1 Hz) of laser operation, putting new challenges for diagnostics. In order to substitute such passive detectors as RCF stack while replicating their working principle in the “online” mode, scintillator materials have been investigated and tested. In this work, we present a compact and cost-effective device, capable of high-energy proton characterization in real time (currently in the range of 20-35 MeV). The detector can provide information about the energy of the proton beam and the Bragg curve distribution, based on analytical estimation and Monte Carlo simulations. The developed scintillator stack was compared with a standard RCF stack during the proof-of-principle test at a conventional accelerator under the same experimental conditions, showing a good signal agreement. Further tests at the laser facilities (e.g. at ELIMAIA (ELI Mulridiscriplinary Applications of laser-Ion Acceleration) user beamline at ELI Beamlines facility) are planned in the nearest future.
Break
Coffee Break 10:30 - 11:00
Session 8:
Laser Ion Acceleration III
27 April 2023 • 11:00 - 12:10 CEST | Tycho
Session Chair:
Sahel Hakimi, Lawrence Berkeley National Lab. (United States)
PC12579-29
Enhanced ion acceleration from transparency-driven foils demonstrated at two ultraintense laser facilities (Conference Presentation)
(Invited Paper)
27 April 2023 • 11:00 - 11:30 CEST | Tycho
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The ultrahigh laser intensities enabled by high power lasers facilitate the generation of high energy ions using accelerating gradients many million times that of conventional accelerators. The maturation of these sources relies on breakthroughs in the generated beam parameters and improved reproducibility and repetition rate. We used two independent state-of-the-art femtosecond laser systems capable of repetitive operation to accelerate protons and carbons to high energies (>50 MeV and 30 MeV/nucleon respectively) in the relativistically induced transparency (RIT) regime. We demonstrate that acceleration is optimised for different laser prepulse levels by varying the initial target thickness, relaxing laser requirements for energetic ion generation. We elucidated the acceleration dynamics with cutting-edge 3D simulation, showing a) the role of the laser prepulse in pre-expanding the target, and b) radiation pressure assisted electron expulsion from the target during relativistically induced transparency, generating a strong space charge field which rapidly accelerates ions. Our demonstration of a robust acceleration mechanism that does not require complicated targetry nor a single-shot prepulse suppressing plasma mirror is an important step forward for developing high repetition rate applications of laser driven ion sources.
PC12579-30
27 April 2023 • 11:30 - 11:50 CEST | Tycho
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A heavy water target system for high repetition rate multi-TW lasers as deuteron source will be presented. This self-regenerated ultrathin liquid leaf surface composed from two liquid jets collided from nozzles of 11 um. At the current state of the development, a stable leaf with a length of 1.5 mm is maintained in 10E-4 mbar vacuum. The thickness of the liquid sheet is <200 nm, measured from the modulation of the spectrally resolved interference arising from white light reflection on the front and the back surfaces of the liquid sheet.
PC12579-31
27 April 2023 • 11:50 - 12:10 CEST | Tycho
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We report on the commissioning of the ELIMAIA beamline laser-plasma Ion Accelerator carried out at relativistic intensities (~1021 W/cm2) with the high repetition-rate, high peak-power L3-HAPLS (>10J in 30 fs) laser available at the ELI Beamlines user facility.
Targets of different composition and thickness were used to optimize the performance of the Ion Accelerator. In the best conditions, we were able to reach proton cutoff energies around 30 MeV and fluxes above 1011/sr.
Moreover, we have demonstrated an excellent reliability and shot-to-shot stability (1-2% in energy) of the Ion Accelerator up to a repetition rate of 0.5 Hz for several hundreds of consecutive shots, along with on-shot target positioning and data acquisition and analysis systems. These results demonstrate the robustness of the developed technology available for users at the ELIMAIA beamline, thus paving the way towards its future use for fundamental and applied research, including biomedical ones.
Break
Lunch Break 12:10 - 13:30
Session 9:
Laser Ion Acceleration IV
27 April 2023 • 13:30 - 15:00 CEST | Tycho
Session Chair:
Jörg Schreiber, Ludwig-Maximilians-Univ. München (Germany)
PC12579-32
Perspectives for application of sub 10-MeV laser-driven proton beams: PIXE and medical radioisotopes production (Conference Presentation)
(Invited Paper)
27 April 2023 • 13:30 - 14:00 CEST | Tycho
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The advance in laser-driven accelerators is progressively allowing to consider these sources for many different applications. Indeed, relatively compact laser systems can deliver few joules on target reaching intensities of 1019 Wcm-2. Such lasers are present in many facilities and are nowadays available as standard products for purchase. The capability of exploiting these sources would thus be beneficial also in terms of larger availability for users willing to leverage proton irradiation.
In this regime, the Target Normal Sheath acceleration (TNSA) is routinely triggered and provides few MeV of protons in short bunches, delivering high dose per shot. Nevertheless, the accelerated proton beam is typically characterized by a divergence of 15° half-angle. Thus, for its effective employment, it is necessary to implement a magnetic transport line to transfer the protons from the TNSA source to the irradiation site. This issue has been faced by many groups and a cost-effective, compact magnetic beamline (hereinafter MBL) has been proposed in a previous work to sensibly enhance the proton flux on secondary targets for protons energy up to 10 MeV.
Geant4 simulations were carried out to assess the feasibility of using an upgraded version of the mentioned MBL to employ laser-driven accelerator as proton source for in-air irradiation of secondary targets. The great versatility of this approach allows to explore multiple irradiation schemes that can be involved in different applications such as Ion Beam Analysis (in particular here we refer to PIXE and XRF) and radioisotope production for PET scan. The outcomes of the simulations were used for the preparation of two dedicated experimental campaigns on the two thematics. Here we present the obtained results and compare them with simulation.
The main achievements are then discussed taking as reference the performance of the currently adopted methodologies, reporting on the main advantages and limits of laser-driven sources with respect to conventional one.
PC12579-33
27 April 2023 • 14:00 - 14:20 CEST | Tycho
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We report on the time-resolved observation of transient laser-induced breakdown (LIB) during the leading edge of high-intensity petawatt-class laser pulses with peak intensities up to 6x10^21 W/cm^2 in interaction with dielectric cryogenic hydrogen jet targets. The results show that LIB occurs much earlier than what is typically expected following the concept of barrier suppression ionization and that the laser pulse duration dependence of LIB and laser-induced damage threshold (LIDT) is very relevant to high-intensity laser-solid interactions. We demonstrate an effective approach to determine the onset of LIB, i.e. the starting point of target pre-expansion, by comparing a laser contrast measurement with a characterization study of the target specific LIB thresholds.
PC12579-34
27 April 2023 • 14:20 - 14:40 CEST | Tycho
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We report on experimental observation on periodic modulation in the energy spectrum of laser accelerated proton beams. Interestingly, theoretical model and two dimensional particle-in-cell simulations, in good agreement with the experimental finding, indicated that such modulation is associated with periodic modulated electron density induced by transverse instability. These results, may have implications for further understanding for the accelerating mechanisms as well as optimization strategies for laser driven ion acceleration.
12579-35
On demand | Presented live 27 April 2023
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Pulsed laser ablation of a solid target immersed in liquid is an excellent technique for the synthesis of nanoparticles in colloidal form. The properties of the nanoparticles can be effectively tailored by varying the laser parameters, liquid properties, ablation conditions, etc. This flexibility is imperative in various important applications like plasmon based sensing, optoelectronics, targeted drug delivery, etc. which require precise control over the size, structure and stoichiometry of the nanoparticles. In the synthesis of nanoparticles by this technique, the transient dynamical processes like the cavitation bubble and shock waves play a crucial role in determining the properties of the synthesized nanoparticles. Hence, for further development in this area, it is important to understand these processes.
With this in view, in the present work, the temporal evolution of the cavitation bubble is used to analytically estimate the extreme conditions of pressure and temperature. For this, pulsed laser ablation of a silver target immersed in distilled water is carried out and the cavitation bubble dynamics is studied by employing the shadowgraphic imaging technique. The second harmonic of a Q-switched Nd:YAG laser operated in single shot mode is used for ablation. For recording the temporal evolution of the cavitation bubbles, a He:Ne laser beam is used as a probe beam. This probe beam is aligned perpendicular to the direction of the pump Nd:YAG beam near the ablated region and finally made to fall on a gated charge coupled device (CCD) camera. The details of the experiments and the results obtained will be elaborately presented in the conference.
Conference Chair
Ulsan National Institute of Science and Technology (Korea, Republic of)
Program Committee
National Institutes for Quantum and Radiological Science and Technology (Japan)
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