J. Chappell
A5039103440- Laser-Plasma Interactions and Diagnostics
- Particle Accelerators and Free-Electron Lasers
- Particle accelerators and beam dynamics
- Magnetic confinement fusion research
- Particle Detector Development and Performance
- Laser-Matter Interactions and Applications
- Particle physics theoretical and experimental studies
- Plasma Diagnostics and Applications
- Pulsed Power Technology Applications
- Laser-induced spectroscopy and plasma
- Atomic and Molecular Physics
- Photocathodes and Microchannel Plates
- Ionosphere and magnetosphere dynamics
- Plasma and Flow Control in Aerodynamics
- X-ray Spectroscopy and Fluorescence Analysis
- Solar and Space Plasma Dynamics
- Electrohydrodynamics and Fluid Dynamics
- Health Systems, Economic Evaluations, Quality of Life
- Astrophysics and Cosmic Phenomena
- High-Energy Particle Collisions Research
- Vacuum and Plasma Arcs
- Fusion materials and technologies
- Electron and X-Ray Spectroscopy Techniques
- Medical Imaging Techniques and Applications
- Gamma-ray bursts and supernovae
University College London
2018-2024
University of Oxford
2023-2024
Deutsches Elektronen-Synchrotron DESY
2022
University of Strathclyde
2022
Cockcroft Institute
2022
Universität Hamburg
2022
Campbell Collaboration
2020
Google (United States)
2019
High energy particle accelerators have been crucial in providing a deeper understanding of fundamental particles and the forces that govern their interactions. In order to increase or reduce size accelerator, new acceleration schemes need be developed. Plasma wakefield acceleration, which electrons plasma are excited, leading strong electric fields, is one such promising novel technique. Pioneering experiments shown an intense laser pulse electron bunch traversing plasma, drives fields 10s...
We give direct experimental evidence for the observation of full transverse self-modulation a long, relativistic proton bunch propagating through dense plasma. The exits plasma with periodic density modulation resulting from radial wakefield effects. show that is seeded by ionization front created using an intense laser pulse copropagating bunch. extends over length following seed point. By varying one order magnitude, we frequency scales expected dependence on density, i.e., it equal to...
The seeded self-modulation of a relativistic, charged particle bunch in plasma is shown to grow both along the and plasma, resulting transverse wakefield amplitudes that far exceed initial seed values.
Energy-efficient plasma-wakefield acceleration of particle bunches with low energy spread is a promising path to realizing compact free-electron lasers and colliders. High efficiency can be achieved simultaneously by strong beam loading plasma wakefields when accelerating carefully tailored current profiles [M. Tzoufras et al., Phys. Rev. Lett. 101, 145002 (2008)]. We experimentally demonstrate such optimal in nonlinear electron-driven accelerator. Bunches an initial 1 GeV were accelerated...
Abstract The interaction of intense particle bunches with plasma can give rise to wakes 1,2 capable sustaining gigavolt-per-metre electric fields 3,4 , which are orders magnitude higher than provided by state-of-the-art radio-frequency technology 5 . Plasma wakefields can, therefore, strongly accelerate charged particles and offer the opportunity reach energies smaller hence more widely available accelerator facilities. However, luminosity brilliance demands high-energy physics photon...
Plasma wakefield acceleration is a promising technology to reduce the size of particle accelerators. The use high energy protons drive wakefields in plasma has been demonstrated during Run 1 AWAKE programme at CERN. Protons 400 GeV drove that accelerated electrons 2 under 10 m plasma. collaboration now embarking on with main aims demonstrate stable accelerating gradients 0.5–1 GV/m, preserve emittance electron bunches and develop sources scalable 100s metres beyond. By end 2, scheme should...
A long, narrow, relativistic charged particle bunch propagating in plasma is subject to the self-modulation (SM) instability. We show that SM of a proton can be seeded by wakefields driven preceding electron bunch. timing reproducibility and control are at level small fraction modulation period. With this seeding method, we independently amplitude seed with charge growth rate Seeding leads larger than instability case.
We describe a simple scheme, truncated-channel injection, to inject electrons directly into the wakefield driven by high-intensity laser pulse guided in an all-optical plasma channel. use this approach generate dark-current-free 1.2 GeV, 4.5% relative energy spread electron bunches with 120 TW pulses 110 mm-long hydrodynamic optical-field-ionized Our experiments and particle-in-cell simulations show that high-quality were only obtained when drive was closely aligned channel axis, focused...
This document provides detailed information on the status of Advanced and Novel Accelerators techniques describes steps that need to be envisaged for their implementation in future accelerators, particular high energy physics applications. It complements overview prepared update European Strategy particle physics, a description field. The scientific priorities community are described each technique acceleration able achieve accelerating gradient GeV~range or above. ALEGRO working group...
We use a relativistic ionization front to provide various initial transverse wakefield amplitudes for the self-modulation of long proton bunch in plasma. show experimentally that, with sufficient amplitude [$\ensuremath{\ge}(4.1\ifmmode\pm\else\textpm\fi{}0.4)\text{ }\text{ }\mathrm{MV}/\mathrm{m}$], phase modulation along is reproducible from event event, 3%--7% (of $2\ensuremath{\pi}$) rms variations all bunch. The not lower amplitudes. observe transition between these two regimes. Phase...
The FLASHForward experimental facility is a high-performance test-bed for precision plasma wakefield research, aiming to accelerate high-quality electron beams GeV-levels in few centimetres of ionized gas. created by ionizing gas cell either high-voltage discharge or high-intensity laser pulse. electrons be accelerated will injected internally from the background externally FLASH superconducting RF front end. In both cases, driven provided gun and linac modules operating with 10 Hz...
The AWAKE experiment had a very successful Run 1 (2016-8), demonstrating proton-driven plasma wakefield acceleration for the first time, through observation of modulation long proton bunch into micro-bunches and electrons up to 2 GeV in 10 m plasma. aims (2021-4) are have high-charge bunches accelerated high energy, about GeV, maintaining beam quality showing that process is scalable. scheme therefore promising method accelerate energy over short distances so develop useable technology...
A train of laser pulses guided by a 100-mm-long, all-optical plasma channel resonantly excites large amplitude wave. Pulse trains similar kind could be generated joule-scale thin-disk lasers, offering route to driving GeV-scale accelerators at kilohertz pulse repetition rates.
We study experimentally the longitudinal and transverse wakefields driven by a highly relativistic proton bunch during self-modulation in plasma. show that wakefields' growth amplitude increase with increasing seed as well charge using maximum radius of distribution measured on screen downstream from externally injecting electrons measuring their final energy. Measurements agree trends predicted theory numerical simulations validate our understanding development self-modulation. Experiments...
Abstract In 2017, AWAKE demonstrated the seeded self-modulation (SSM) of a 400 GeV proton beam from Super Proton Synchrotron at CERN. The angular distribution protons deflected due to SSM is quantitative measure process, which agrees with simulations by two-dimensional (axisymmetric) particle-in-cell code LCODE about 5%. agreement achieved in population scans two selected plasma densities and scan longitudinal density gradient. reached only case wide enough simulation box (several...
In this article, we briefly summarize the experiments performed during first Run of Advanced Wakefield Experiment, AWAKE, at CERN (European Organization for Nuclear Research). The final goal AWAKE 1 (2013 - 2018) was to demonstrate that \unit[10-20]{MeV} electrons can be accelerated GeV-energies in a plasma wakefield driven by highly-relativistic self-modulated proton bunch. We describe experiment, outline measurement concept and present results. Last, our plans future.
We study experimentally the effect of linear plasma density gradients on self-modulation a 400\,GeV proton bunch. Results show that positive/negative gradient in/decreases number micro-bunches and relative charge per micro-bunch observed after 10\,m plasma. The measured modulation frequency also in/decreases. With largest positive we observe two frequencies in power spectrum. are consistent with changes wakefields' phase velocity due to adding slow during growth predicted by theory.
This paper describes the utilization of beam-driven plasma wakefield acceleration to implement a high-quality cathode via density-downramp injection in short injector stage at FLASHForward facility DESY. Electron beams with charge up 105 pC and energy spread few percent were accelerated by tunable effective accelerating field 2.7 GV/m. The was operated drift-free very high efficiency. Sources jitter, emittance divergence resulting beam investigated modeled, as strategies for performance...
Radio-frequency particle accelerators are engines of discovery, powering high-energy physics and photon science, but also large expensive due to their limited accelerating fields. Plasma-wakefield (PWFAs) provide orders-of-magnitude stronger fields in the charge-density wave behind a bunch travelling plasma, promising greatly reduced size cost. However, PWFAs can easily degrade beam quality bunches they accelerate. Emittance, which determines how tightly beams be focused, is critical for...
Plasma wakefield dynamics over timescales up to 800 ps, approximately 100 plasma periods, are studied experimentally at the Advanced Wakefield Experiment (AWAKE). The development of longitudinal amplitude driven by a self-modulated proton bunch is measured using external injection witness electrons that sample fields. In simulation, resonant excitation causes electron trajectory crossing, resulting in potential outside boundary as transversely ejected. Trends consistent with presence this...
A model describing the evolution of average plasma temperature inside a discharge capillary device including Ohmic heating, heat loss to wall, and ionization recombination effects is developed. Key this approach an analytic quasistatic description radial variation which, under local thermal equilibrium conditions, allows behavior both electron density be specified directly from evolution. In way, standard set coupled partial differential equations for magnetohydrodynamic (MHD) simulations...