John Adams Institute for Accelerator Science

Ultraintense laser pulses with a few-cycle rising edge are ideally suited to accelerating ions from ultrathin foils, and achieving such pulses in practice represents a formidable challenge. We show that such pulses can be obtained using sufficiently strong and well-controlled relativistic nonlinearities in spatially well-defined near-critical-density plasmas. The resulting ultraintense pulses with an extremely steep rising edge give rise to significantly enhanced carbon ion energies consistent with a transition to radiation pressure acceleration.

The Advanced Proton Driven Plasma Wakefield Acceleration Experiment (AWAKE) aims at studying plasma wakefield generation and electron acceleration driven by proton bunches. It is a proof-of-principle R&D experiment at CERN and the world׳s first proton driven plasma wakefield acceleration experiment. The AWAKE experiment will be installed in the former CNGS facility and uses the 400 GeV/c proton beam bunches from the SPS. The first experiments will focus on the self-modulation instability of the long (rms ~12 cm) proton bunch in the plasma. These experiments are planned for the end of 2016. Later, in 2017/2018, low energy (~15 MeV) electrons will be externally injected into the sample wakefields and be accelerated beyond 1 GeV. The main goals of the experiment will be summarized. A summary of the AWAKE design and construction status will be presented.

New acceleration technology is mandatory for the future elucidation of fundamental particles and their interactions. A promising approach is to exploit the properties of plasmas. Past research has focused on creating large-amplitude plasma waves by injecting an intense laser pulse or an electron bunch into the plasma. However, the maximum energy gain of electrons accelerated in a single plasma stage is limited by the energy of the driver. Proton bunches are the most promising drivers of wakefields to accelerate electrons to the TeV energy scale in a single stage. An experimental program at CERN - the AWAKE experiment - has been launched to study in detail the important physical processes and to demonstrate the power of proton-driven plasma wakefield acceleration. Here we review the physical principles and some experimental considerations for a future proton-driven plasma wakefield accelerator. © 2014 IOP Publishing Ltd.

OBJECTIVE: To reinvestigate ultra-high dose rate radiation (UHDRR) radiobiology and consider potential implications for hadrontherapy. METHODS: A literature search of cellular UHDRR exposures was performed. Standard oxygen diffusion equations were used to estimate the time taken to replace UHDRR-related oxygen depletion. Dose rates from conventional and novel methods of hadrontherapy accelerators were considered, including spot scanning beam delivery, which intensifies dose rate. RESULTS: The literature findings were that, for X-ray and electron dose rates of around 10(9) Gy s(-1), 5-10 Gy depletes cellular oxygen, significantly changing the radiosensitivity of cells already in low oxygen tension (around 3 mmHg or 0.4 kPa). The time taken to reverse the oxygen depletion of such cells is estimated to be over 20-30 s at distances of over 100 μm from a tumour blood vessel. In this time window, tumours have a higher hypoxic fraction (capable of reducing tumour control), so the next application of radiation within the same fraction should be at a time that exceeds these estimates in the case of scanned beams or with ultra-fast laser-generated particles. CONCLUSION: This study has potential implications for particle therapy, including laser-generated particles, where dose rate is greatly increased. Conventional accelerators probably do not achieve the critical UHDRR conditions. However, specific UHDRR oxygen depletion experiments using proton and ion beams are indicated.

Active plasma lensing is a compact technology for strong focusing of charged particle beams, which has gained considerable interest for use in novel accelerator schemes. While providing kT/m focusing gradients, active plasma lenses can have aberrations caused by a radially nonuniform plasma temperature profile, leading to degradation of the beam quality. We present the first direct measurement of this aberration, consistent with theory, and show that it can be fully suppressed by changing from a light gas species (helium) to a heavier gas species (argon). Based on this result, we demonstrate emittance preservation for an electron beam focused by an argon-filled active plasma lens.

Abstract Presented is a novel way to combine snapshot compressive imaging and lateral shearing interferometry in order to capture the spatio-spectral phase of an ultrashort laser pulse in a single shot. A deep unrolling algorithm is utilized for snapshot compressive imaging reconstruction due to its parameter efficiency and superior speed relative to other methods, potentially allowing for online reconstruction. The algorithm’s regularization term is represented using a neural network with 3D convolutional layers to exploit the spatio-spectral correlations that exist in laser wavefronts. Compressed sensing is not typically applied to modulated signals, but we demonstrate its success here. Furthermore, we train a neural network to predict the wavefronts from a lateral shearing interferogram in terms of Zernike polynomials, which again increases the speed of our technique without sacrificing fidelity. This method is supported with simulation-based results. While applied to the example of lateral shearing interferometry, the methods presented here are generally applicable to a wide range of signals, including Shack–Hartmann-type sensors. The results may be of interest beyond the context of laser wavefront characterization, including within quantitative phase imaging.

The paper presents the calibration of Fuji BAS-TR image plate (IP) response to high energy carbon ions of different charge states by employing an intense laser-driven ion source, which allowed access to carbon energies up to 270 MeV. The calibration method consists of employing a Thomson parabola spectrometer to separate and spectrally resolve different ion species, and a slotted CR-39 solid state detector overlayed onto an image plate for an absolute calibration of the IP signal. An empirical response function was obtained which can be reasonably extrapolated to higher ion energies. The experimental data also show that the IP response is independent of ion charge states.

We show the excitation of a nonlinear ion-wake mode by plasma electron modes in the bubble regime driven by intense energy sources, using analytical theory and simulations. The ion wake is shown to be a driven nonlinear ion-acoustic wave in the form of a long-lived cylindrical ion soliton which limits the repetition rate of a plasma-based particle accelerator in the bubble regime. We present the application of this evacuated and radially outwards propagating ion-wake channel with an electron skin-depth scale radius for the ``crunch-in'' regime of hollow-channel plasma. It is shown that the time-asymmetric focusing force phases in the bubble couple to ion motion significantly differently than in the linear electron mode. The electron compression in the back of the bubble sucks in the ions whereas the space charge within the bubble cavity expels them, driving a cylindrical ion-soliton structure at the bubble radius. Once formed, the soliton is sustained and driven radially outwards by the thermal pressure of the wake energy in electrons. Particle-in-cell simulations are used to study the ion-wake soliton structure, its driven propagation and its use for positron acceleration in the crunch-in regime.

Abstract The control of light’s various degrees of freedom underpins modern physics and technology, from quantum optics to telecommunications. Ultraintense lasers represent the pinnacle of this control, concentrating light to extreme intensities at which electrons oscillate at relativistic velocities within a single optical cycle. These extraordinary conditions offer unique opportunities to probe the fundamental aspects of light–matter interactions and develop transformative applications. However, the precise characterization of intense, ultrashort lasers has lagged behind our ability to generate them, creating a bottleneck in advancing laser science and its applications. Here we present the first single-shot vector field measurement technique for intense, ultrashort laser pulses that provides an unprecedented insight into their complete spatiotemporal and polarization structure, including quantified uncertainties. Our method efficiently encodes the full vector field onto a two-dimensional detector by leveraging the inherent properties of these laser pulses, allowing for real-time characterization. We demonstrate its capabilities on systems ranging from high-repetition-rate oscillators to petawatt-class lasers, revealing subtle spatiotemporal couplings and polarization effects. This advancement bridges the gap between theory and experiment in laser physics, providing crucial data for simulations and accelerating the development of novel applications in high-field physics, laser–matter interactions, future energy solutions and beyond.

Experiments were performed on laser wakefield acceleration in the highly nonlinear regime. With laser powers P<250 TW and using an initial spot size larger than the matched spot size for guiding, we were able to accelerate electrons to energies E_{max}>2.5 GeV, in fields exceeding 500 GV m^{-1}, with more than 80 pC of charge at energies E>1 GeV. Three-dimensional particle-in-cell simulations show that using an oversized spot delays injection, avoiding beam loss as the wakefield undergoes length oscillation. This enables injected electrons to remain in the regions of highest accelerating fields and leads to a doubling of energy gain as compared to results from using half the focal length with the same laser.

An electro-optic laser beam deflector with a clear optical aperture of 8.6 mm has been designed, realized, and tested. The electro-optic material used to implement the device was a MgO:LiNbO3 crystal. The exceptionally large aperture makes the device suitable for applications where fast scanning of high power laser beams is needed. The measured deflection angle was 120 μrad/kV for a total length of electro-optic material of 90 mm. A mode quality analysis of the laser beam revealed that the M2 of the laser is affected by less than 4% during scan operation when maximum driving voltage is applied.

Highly collimated betatron radiation from a laser wakefield accelerator is a promising tool for spectroscopic measurements. Therefore, there is a requirement to create spectrometers suited to the unique properties of such a source. We demonstrate a spectrometer which achieves an energy resolution of <5 eV at 9 keV (E∕ΔE>1800) and is angularly resolving the x-ray emission allowing the reference and spectrum to be recorded at the same time. The single photon analysis is used to significantly reduce the background noise. Theoretical performance of various configurations of the spectrometer is calculated by a ray-tracing algorithm. The properties and performance of the spectrometer including the angular and spectral resolution are demonstrated experimentally on absorption above the K-edge of a Cu foil backlit by a laser-produced betatron radiation x-ray beam.

The AWAKE Collaboration has been formed in order to demonstrate proton-driven plasma wakefield acceleration for the first time. This acceleration technique could lead to future colliders of high energy but of a much reduced length when compared to proposed linear accelerators. The CERN SPS proton beam in the CNGS facility will be injected into a 10 m plasma cell where the long proton bunches will be modulated into significantly shorter micro-bunches. These micro-bunches will then initiate a strong wakefield in the plasma with peak fields above 1 GV/m that will be harnessed to accelerate a bunch of electrons from about 20 MeV to the GeV scale within a few meters. The experimental program is based on detailed numerical simulations of beam and plasma interactions. The main accelerator components, the experimental area and infrastructure required as well as the plasma cell and the diagnostic equipment are discussed in detail. First protons to the experiment are expected at the end of 2016 and this will be followed by an initial three-four years experimental program. The experiment will inform future larger-scale tests of proton-driven plasma wakefield acceleration and applications to high energy colliders.

Abstract We report on the evaluation of the performance of self-guiding over extended distances with <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>f</mml:mi> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:mn>20</mml:mn> </mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>f</mml:mi> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:mn>40</mml:mn> </mml:math> focussing geometries. Guiding over <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>39</mml:mn> <mml:mspace width="0.25em"/> <mml:mi>mm</mml:mi> </mml:math> or more than 100 Rayleigh ranges was observed with the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>f</mml:mi> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:mn>20</mml:mn> </mml:math> optic at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>n</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>e</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>1.5</mml:mn> <mml:mo>×</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow> <mml:mn>18</mml:mn> </mml:mrow> </mml:msup> <mml:mspace width="0.25em"/> <mml:msup> <mml:mrow> <mml:mi>cm</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>3</mml:mn> </mml:mrow> </mml:msup> </mml:math> . Analysis of guiding performance found that the extent of the exiting laser spatial mode closely followed the matched spot size predicted by 3D nonlinear theory. Self-guiding with an <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>f</mml:mi> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:mn>40</mml:mn> </mml:math> optic was also characterised, with guided modes observed for a plasma length of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>90</mml:mn> <mml:mspace width="0.25em"/> <mml:mi>mm</mml:mi> </mml:math> and a plasma density of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>n</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>e</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>9.5</mml:mn> <mml:mo>×</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow> <mml:mn>17</mml:mn> </mml:mrow> </mml:msup> <mml:mspace width="0.25em"/> <mml:msup> <mml:mrow> <mml:mi>cm</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>3</mml:mn> </mml:mrow> </mml:msup> </mml:math> . This corresponds to self-guided propagation over 53 Rayleigh ranges and is similar to distances obtained with discharge plasma channel guiding.

Abstract Low convergence ratio implosions (where wetted-foam layers are used to limit capsule convergence, achieving improved robustness to instability growth) and auxiliary heating (where electron beams are used to provide collisionless heating of a hotspot) are two promising techniques that are being explored for inertial fusion energy applications. In this paper, a new analytic study is presented to understand and predict the performance of these implosions. Firstly, conventional gain models are adapted to produce gain curves for fixed convergence ratios, which are shown to well-describe previously simulated results. Secondly, auxiliary heating is demonstrated to be well understood and interpreted through the burn-up fraction of the deuterium-tritium fuel, with the gradient of burn-up with respect to burn-averaged temperature shown to provide good qualitative predictions of the effectiveness of this technique for a given implosion. Simulations of auxiliary heating for a range of implosions are presented in support of this and demonstrate that this heating can have significant benefit for high gain implosions, being most effective when the burn-averaged temperature is between 5 and 20 keV.

Abstract Relativistic collisionless shock charged particle acceleration is considered as a possible origin of high-energy cosmic rays. However, it is hard to explore the nature of relativistic collisionless shock due to its low occurring frequency and remote detecting distance. Recently, there are some works attempt to solve this problem by generating relativistic collisionless shock in laboratory conditions. In laboratory, the scheme of generation of relativistic collisionless shock is that two electron–positron pair plasmas knock each other. However, in laboratory, the appropriate pair plasmas have been not generated. The 10 PW laser pulse maybe generates the pair plasmas that satisfy the formation condition of relativistic collisionless shock due to its ultrahigh intensity and energy. In this paper, we study the positron production by ultraintense laser high Z target interaction using numerical simulations, which consider quantum electrodynamics effect. The simulation results show that the forward positron beam up to 10 13 /kJ can be generated by 10 PW laser pulse interacting with lead target. The estimation of relativistic collisionless shock formation shows that the positron yield satisfies formation condition and the positron divergence needs to be controlled. Our results indicate that the generation of relativistic collisionless shock by 10 PW laser facilities in laboratory is possible.

For plasma-wakefield accelerators to fulfill their potential for cost effectiveness, it is essential that their energy-transfer efficiency be maximized. A key aspect of this efficiency is the near-complete transfer of energy, or depletion, from the driver electrons to the plasma wake. Achieving full depletion is limited by the process of re-acceleration, which occurs when the driver electrons decelerate to nonrelativistic energies, slipping backward into the accelerating phase of the wakefield and being subsequently re-accelerated. Such re-acceleration is unambiguously observed here for the first time. At this re-acceleration limit, we measure a beam driver depositing <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mo>(</a:mo><a:mn>57</a:mn><a:mo> </a:mo><a:mo>±</a:mo><a:mo> </a:mo><a:mn>3</a:mn><a:mo>)</a:mo><a:mo>%</a:mo></a:math> of its energy into a 195-mm-long plasma. This suggests that the energy-transfer efficiency of plasma accelerators could approach that of conventional accelerators. Published by the American Physical Society 2024

Methods and techniques used to capture and analyze beam profiles produced from the interaction of intense, ultrashort laser pulses and ultrathin foil targets using stacks of Radiochromic Film (RCF) and Columbia Resin #39 (CR-39) are presented. The identification of structure in the beam is particularly important in this regime, as it may be indicative of the dominance of specific acceleration mechanisms. Additionally, RCF can be used to deconvolve proton spectra with coarse energy resolution while mantaining angular information across the whole beam.

We report on the measurement of filamented transport of laser-generated fast electron beams in near-critical density plasma. A relativistic intensity long-wave-infrared laser irradiated a hydrodynamically shaped helium gas flow at an electron density n_{e}≃10^{25} m^{-3}, generating a large flux of fast electrons that propagated beyond the critical surface. The beam-to-background electron density ratio was sufficiently high to drive growth of Weibel-like filamentation, which was measured by optical probing to extend up to 800 μm with radii ∼10 μm. Particle-in-cell simulations reproduce the main features of the filamentation generation, suggesting that collisionless processes are dominant in these interactions. Expansion of the filaments after formation infers a fast electron heated plasma temperature ∼400 eV in the overcritical density plasma.

Recent advances in high-energy and high-peak-power laser systems have opened up new possibilities for fundamental physics research. In this work, the potential of twisted light for the generation of gravitational waves in the high frequency regime is explored for the first time. Focusing on Bessel beams, novel analytic expressions and numerical computations for the generated metric perturbations and associated powers are presented. The gravitational peak intensity is shown to reach <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mrow><a:mn>1.44</a:mn><a:mo>×</a:mo><a:msup><a:mrow><a:mn>10</a:mn></a:mrow><a:mrow><a:mo>−</a:mo><a:mn>5</a:mn></a:mrow></a:msup><a:mtext> </a:mtext><a:mtext> </a:mtext><a:msup><a:mrow><a:mi mathvariant="normal">W</a:mi><a:mtext> </a:mtext><a:mi mathvariant="normal">m</a:mi></a:mrow><a:mrow><a:mo>−</a:mo><a:mn>2</a:mn></a:mrow></a:msup></a:mrow></a:math> close to the source, and <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:mrow><e:mn>1.01</e:mn><e:mo>×</e:mo><e:msup><e:mrow><e:mn>10</e:mn></e:mrow><e:mrow><e:mo>−</e:mo><e:mn>19</e:mn></e:mrow></e:msup><e:mtext> </e:mtext><e:mtext> </e:mtext><e:msup><e:mrow><e:mi mathvariant="normal">W</e:mi><e:mtext> </e:mtext><e:mi mathvariant="normal">m</e:mi></e:mrow><e:mrow><e:mo>−</e:mo><e:mn>2</e:mn></e:mrow></e:msup></e:mrow></e:math> ten meters away. Compelling evidence is provided that the properties of the generated gravitational waves, such as frequency, polarization states, and direction of emission, are controllable by the laser pulse parameters and optical arrangements. Published by the American Physical Society 2024