T. Lefèvre
A5020057046- Particle Accelerators and Free-Electron Lasers
- Particle Detector Development and Performance
- Particle accelerators and beam dynamics
- Advanced X-ray Imaging Techniques
- Gyrotron and Vacuum Electronics Research
- Laser-Plasma Interactions and Diagnostics
- Superconducting Materials and Applications
- Radiation Detection and Scintillator Technologies
- Magnetic confinement fusion research
- Medical Imaging Techniques and Applications
- Particle physics theoretical and experimental studies
- Crystallography and Radiation Phenomena
- X-ray Spectroscopy and Fluorescence Analysis
- Advancements in Photolithography Techniques
- Photocathodes and Microchannel Plates
- Advanced Optical Sensing Technologies
- Atomic and Molecular Physics
- Nuclear Physics and Applications
- Atomic and Subatomic Physics Research
- Radiation Therapy and Dosimetry
- Laser Design and Applications
- Plasma Diagnostics and Applications
- Electron and X-Ray Spectroscopy Techniques
- Optical Systems and Laser Technology
- Distributed and Parallel Computing Systems
European Organization for Nuclear Research
2015-2024
University of Liverpool
2022
Laboratoire de Physique des 2 Infinis Irène Joliot-Curie
2022
Institut National de Physique Nucléaire et de Physique des Particules
2022
Centre National de la Recherche Scientifique
2011-2022
Université Paris-Saclay
2022
Cockcroft Institute
2022
Campbell Collaboration
2020-2022
Google (United States)
2019
Diamond Light Source
2018
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.
We show in experiments that a long, underdense, relativistic proton bunch propagating plasma undergoes the oblique instability, which we observe as filamentation. determine threshold value for ratio between transverse size and skin depth instability to occur. At threshold, outcome of experiment alternates filamentation self-modulation (evidenced by longitudinal modulation into microbunches). Time-resolved images density distribution reveal grows an observable level late along bunch,...
AWAKE is a proton-driven plasma wakefield acceleration experiment. % We show that the experimental setup briefly described here ready for systematic study of seeded self-modulation 400\,GeV proton bunch in 10\,m-long rubidium with density adjustable from 1 to 10$\times10^{14}$\,cm$^{-3}$. short laser pulse used ionization vapor propagates all way along column, suggesting full vapor. occurs bunch, at time and follows affects bunch.
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...
Experimental results show that hosing of a long particle bunch in plasma can be induced by wakefields driven short, misaligned preceding bunch. Hosing develops the plane misalignment, self-modulation perpendicular plane, at frequencies close to electron frequency, and are reproducible. Development depends on misalignment direction, its growth extent proton charge. Results have main characteristics theoretical model, relevant other plasma-based accelerators represent first characterization...
This paper presents the design and experimental commissioning of a noninvasive electron bunch length monitor based on detection coherent Cherenkov diffraction radiation (ChDR). The measurement technique effectively eliminates influence bunch-by-bunch charge fluctuations, as each detector measures signal from same while mitigating impact position jitter measurements, providing potential real-time diagnostic tool with significant operational advantages. sensitivity measurements to both...
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 report on the observation of incoherent Cherenkov radiation emitted by a 5.3 GeV positron beam circulating in Cornell electron-positron storage ring as passes close vicinity surface fused silica radiator (i.e., at distance larger than 0.8 mm). The shape was designed order to send photons towards detector, consisting compact optical system equipped with an intensified camera. allows both measurements 2D images and angular distribution including polarization study. corresponding light...
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...
In recent years, there has been an increasing demand for noninvasive beam size monitoring on particle accelerators. Ideally, these monitors should be cost effective and require little or no maintenance. These also suitable both linear circular machines. Here, the experimental setup is described in detail, results from a diffraction radiation monitor are presented. This tested Cornell Electron Storage Ring using 1 mA ($1.6\ifmmode\times\else\texttimes\fi{}{10}^{10}$ particles per bunch)...
We present the observation and detailed investigation of coherent Cherenkov diffraction radiation (CChDR) in terms spectral-angular characteristics. Electromagnetic simulations have been performed to optimize design a prismatic dielectric radiator performance detection system with aim providing longitudinal beam diagnostics. Successful experimental validations organized on CLEAR CLARA facilities based at CERN Daresbury laboratory respectively. With ps sub-ps long electron bunches, emitted...
A minimally invasive transverse beam profile monitor based on supersonic gas curtain technology and beam-induced fluorescence has been developed demonstrated. The concept presented can be used to measure both the of proton in Large Hadron Collider (LHC) concentricity electron beams LHC hollow lens. In this Letter, performance such a for low energy is discussed, which paves way its wider implementation.
The proposed Compact Linear Collider (CLIC) is a multi-TeV electron-positron collider for particle physics based on an innovative two-beam acceleration concept. A high-intensity drive beam powers the main of high-frequency (30 GHz) linac with gradient 150 MV/m, by means transfer structure sections. aim CLIC Test Facility (CTF3) to make exhaustive tests parameters and prove technical feasibility. One points particular interest demonstration bunch train compression combination in Delay Loop...
The plasma rotation in the axial magnetic field of linear machine Mistral [A. Escarguel, Eur. Phys. J. D 56, 209 (2010)] is well described by assumption that electrons injected from source exit radially central column and are subject to Lorentz force. Electrons ions rotate together ambipolarity. solution momentum equations foresees correctly observed radial dependence ionic velocity measured laser induced fluorescence. resolution these also good agreement with frequency on applied background...
The CERN Linear Electron Accelerator for Research (CLEAR) has now finished its second year of operation, providing a testbed new accelerator technologies and versatile radiation source. Hosting varied experimental program, this beamline provides flexible test facility users both internal external to CERN, as well being an excellent physics training ground. energy can be between 60 220 MeV, bunch length 1 4 ps, charge in the range 10 pC 2 nC, number bunches 200, at repetition rate 0.8 Hz....
Optical transition radiation (OTR) has become a commonly used method for 2D beam imaging measurements. In the Accelerator Test Facility 2 (ATF2) at KEK, sizes smaller than OTR point spread function have been measured. Simulations of system performed using ZEMAX software to study effects optical errors such as aberrations, diffraction, and misalignments components. This paper presents comparison simulations with experimental data obtained ATF2. It shows how quantification control impacts on...
We present recent achievements in the application of optical diffraction radiation (ODR) to measurement transverse beam size a 1.3 GeV micrometer-size electron performed with an instrument installed extended extraction line KEK Accelerator Test Facility. ODR is technique for and emittance highly relativistic particle beams. has advantage being noninvasive relatively inexpensive candidate operation linear accelerators, where no simple alternatives (e.g., synchrotron radiation) are available....
We exploit the coherent emission of Cherenkov diffraction radiation (ChDR) by a relativistic electron beam to sense its position even in presence other particle beams. ChDR is produced alumina inserts embedded vacuum chamber walls and recorded narrow band centered at 30 GHz. This nontrivial solution has been implemented for plasma wakefield accelerators, where be sensed can copropagate with another high-energy proton that generates wakefield. In addition, variance most existing detectors,...
Pronounced electron-beam bunching and high-power emission at 3 GHz have been observed in the 35-GHz free-electron-laser (FEL) experiment CEA/CESTA. It corresponds to low-frequency resonance of FEL which appears addition high-frequency when a waveguide is used. The dependence on length (in wiggler) time pulse) shows that spontaneously generated mode comes dominate injected long distances late times.
The longitudinal density monitor (LDM) is primarily intended for the measurement of particle population in nominally empty rf buckets. These so-called satellite or ghost bunches can cause problems machine protection as well influencing luminosity calibration LHC. high dynamic range system allows with little 0.01% main bunch at same time characterization bunches. LDM a single-photon counting using visible synchrotron light. photon detector silicon avalanche photodiode operated Geiger mode,...
We report on the radiation studies performed at CLEAR facility of CERN in sub-THz range, exploiting picosecond ultrarelativistic electron bunches for production coherent radiation. The radiation, produced by different mechanisms (in particular transition radiation), has been fully characterized using techniques and detectors. main aim that to setup a new beam-based source mm-waves external users, individuating performances limitations. Moreover used longitudinal diagnostics, providing...
The CEA/CESTA free-electron laser amplifier has been operated in the self-amplified spontaneous emission mode. This waveguide two resonant frequencies for given beam energy and wiggler field, at approximately 3 35 GHz, respectively, our operating conditions. Highly reproducible microwave power levels of 40 MW pronounced electron bunching are seen lower frequency. Streak camera photographs time dependence mechanism frequency presented. is accompanied by a significant loss electrons from beam.