We report for the first time a methodology for the dosimetric characterization of the PHIL (Photo Injector at Laboratoire de l'accelerateur lineaire) electron accelerator beamline using a variety of new radiation-hard silicon carbide (SiC)-based detectors developed for Ultra-High Dose Rate (UHDR) applications, including single diodes (0.6-2.2 mm) and a 4 x 4 pixel array. The 7 MeV electrons were pulsed in bunches on ps scale in rates of 10 Hz. Although the maximum measured average dose rate (similar to 1.2 Gy/s) remains below the UHDR threshold for triggering the biological FLASH effect under UHDR (> 40 Gy/s), the instantaneous dose rates are on the order of 10(10) Gy/s. The SiC detectors exhibited linear response over the beam charge range of 2-36 pC per bunch enabling also beam profiling with these detectors. No saturation effects were observed in any of the SiC devices, whereas instantaneous dose rates far exceeded those used in FLASH studies due to the extremely short bunch duration (similar to 20 ps). These results constitute the highest instantaneous dose rate measured with SiC dosimeters reported to date, which validate their suitability as dosimeter for future accelerator developments with capacities beyond current UHDRs used in FLASH therapy. This work marks a substantial methodological advance for accelerators with extremely short picosecond electron bunches and RF-induced parasitic signals.

The present article reports on the generation of stable 50 pC low-divergence electron beams above 150 MeV from laser-driven wakefield acceleration using a continuous-flow gas target prototype tested at the 60 TW Salle Jaune facility at LOA. The gas target design is meant to be easily transported and integrated as an element of the beamline with a differential pumping system offering some 10−4 mbar pressure in the rest of the line. A dedicated gas injection system allows for the control of the gas mixture concentration and gas pressure in two different regions of the target within the frame of controlled ionisation injection schemes. The measured electron beam parameters show the importance of gas density profiles and longitudinal gas mixture confinement.

With the increase in laser power and finesse of optical cavities over the last decade, laboratory-size Compton sources are very promising. These sources produce X-rays through interactions between relativistic electrons and laser photons and, in term of brightness, fall between large synchrotron facilities and classical laboratory X-ray sources. The ThomX source is the French project in this field. This article first presents a state of the art of high-intensity Compton sources, then the ThomX source is briefly described, and the first results are detailed, in particular the production of the first X-rays, the acquisition of the first spectrum and the first image of the beam. Finally, the next objectives are discussed.

The ARES linac at DESY aims to generate and characterize ultrashort electron bunches (fs to sub-fs duration) with high momentum and arrival time stability for the purpose of applications related to accelerator R&D, e.g. development of advanced and compact diagnostics and accelerating structures, test of new accelerator components, medical applications studies, machine learning, etc. During its commissioning phase, the bunch duration characterization of the electron bunches generated at ARES has been performed with an RF-phasing technique relying on momentum spectra measurements, using only common accelerator elements (RF accelerating structures and magnetic spectrometers). The sensitivity of the method allowed highlighting different response times for Mo and Cs2Te cathodes. The measured electron bunch duration in a wide range of machine parameters shows excellent agreement overall with the simulation predictions, thus demonstrating a very good understanding of the ARES operation on the bunch duration aspect. The importance of a precise in-situ experimental determination of the phase velocity of the first travelling wave accelerating structure after the electron source, for which we propose a simple new beam-based method precise down to sub-permille variation respective to the speed of light in vacuum, is emphasized for this purpose. A minimum bunch duration of 20 fs rms, resolution-limited by the space charge forces, is reported. This is, to the best of our knowledge, around 4 times shorter than what has been previously experimentally demonstrated based on RF-phasing techniques with a single RF structure. The present study constitutes a strong basis for future time characterization down to the sub-fs level at ARES, using dedicated X-band transverse deflecting structures.

Powerful ERL for experiments (PERLE) is a novel energy recovery linac (ERL) test facility [1], designed to validate choices for a 50 GeV ERL foreseen in the design of the Large Hadron Electron Collider and the Future Circular Collider and to host dedicated nuclear and particle physics experiments. Its main goal is to demonstrate the high current, continuous wave, multipass operation with superconducting cavities at 802 MHz. With very high beam power (10 MW), PERLE offers an opportunity for controllable study of every beam dynamic effect of interest in the next generation of ERLs and becomes a "stepping stone" between the present state-of-the-art 1 MW ERLs and the future 100 MW scale applications.

The optimization and advanced study of a laser-plasma electron injector are presented based on a truncated ionization injection scheme for high quality beam production. The smilei code is used with laser envelope approximation and a low number of particles per cell to reach computation time performances enabling the production of a large number of accelerator configurations. The developed and tested workflow is a possible approach for the production of a large dataset for laser-plasma accelerator optimization. A selection of functions of merit used to grade generated electron beams is discussed. Among the significant number of configurations, two specific working points are presented in detail. All data generated are left open to the scientific community for further study and optimization.

We present an overview of the diagnostics screens stations - named SSTs - of the ThomX compact Compton source. ThomX is a compact light source based on Compton backscattering. It features a linac and a storage ring in which the electrons have an energy of 50 MeV. Each SST is composed of three screens, a YAG:Ce screen and an Optical Transition Radiation (OTR) screen for transverse measurements and a calibration target for magnification and resolution characterisation. The optical system is based on commercial lenses that have been reverse-engineered. An Arduino is used to control both the aperture and the focus remotely, while the magnification must be modified using an external motor. We report on the overall performance of the station as measured during the first steps of beam commissioning and on the optical system remote operations.

The stability and the quality of particle beams are of utmost importance for many emerging linac installations. The impact on beam properties damage of beam electromagnetic element misalignments and jitter/fluctuations in various accelerator sub-systems should be properly known, as usually such shot-to-shot fluctuations cannot be avoided. On top of that, knowing which parameters the machine is most sensitive to is of utmost to take precautionary measures to reduce the beam degradation and thus improve beam stability and quality. This simulation work focuses on a 50 MeV S-band linear accelerator based on RF photoinjector electron source. The sensitivity of the beam parameters towards several errors has been studied collectively as well as individually for each accelerator element. While the emittance at the end of the linac is dominated by the laminar behavior in the accelerating section, the main emittance degradation comes mainly from orbit errors located at the linac entrance.

A method for the optimisation and advanced studies of a laser-plasma electron injector is presented, based on a truncated ionisation injection scheme for high quality beam production. The SMILEI code is used with laser envelope approximation and a low number of particles per cell to reach computation time performances enabling the production of a large number of accelerator configurations. The developed and tested workflow is a possible approach for the production of large dataset for laser-plasma accelerator optimisation. A selection of functions of merit used to grade generated electron beams is discussed. Among the significant number of configurations, two specific working points are presented in details. All data generated are left open to the scientific community for further study and optimisation.

This article deals with the design of an impedance model (including geometric, resistive wall and coherent synchrotron radiation (CSR) wakefields) for ThomX, a 50 MeV electron storage ring designed to work in pulsed mode. The beam dynamics is very different from usual damped storage rings and is strongly dominated by collective effects. The geometric and resistive wall impedance model is obtained using simulation or analytical modelling of the individual elements and is checked using wire measurements on prototypes. The CSR is simulated in a rectangular vacuum chamber to take into account transient effects and resonances. From these models, two distinct regimes of beam dynamics stand out, driven respectively by the CSR and by the geometric impedance.

ThomX is a new generation compact Compton source. The machine is composed of a 50/70 MeV injector linac and a storage ring where an electron bunch collides with a laser pulse accumulated in a Fabry-Perot resonator. The compact source, built at Irene Joliot-Curie Laboratory (IJCLAB) in the Orsay campus of Paris-Saclay University, is designed to produce a total flux of 10¹³ ph/s and a brightness of 1011 ph / (s.mm2.mrad2) in 0.1% of bandwidth with a tunable energy ranging from 45 keV to 90 keV on the X-ray beam axis. The photo-injector is composed of a homemade 2.5 cell photocathode RF-gun, placed between two solenoids. An energy of 5 MeV is reached with a 80 MV/m electric field gradient. During the commissioning phase, a 4.8 m S-band LIL section will be used to achieve a 50 MeV corresponding to a 45 keV X-ray energy. The LIL accelerating section is a quasi-constant gradient traveling wave structure. The energy gain in the section is 45 MeV, corresponding to an average effective accelerating gradient of 10 MV/m for an input RF power of 9 MW. Here we present the electromagnetic and beam dynamics studies of the ThomX LINAC.

We report on an injection feedback scheme for the ThomX storage ring project. ThomX is a 50-MeV-electron accelerator prototype which will use Compton backscattering in a storage ring to generate a high flux of hard X-rays. Given the slow beam damping (in the ring), the injection must be performed with high accuracy to avoid large betatron oscillations. A homemade analytic code is used to compute the corrections that need to be applied before the beam injection to achieve a beam position accuracy of a few hundred micrometers in the first beam position monitors (BPMs). In order to do so the code needs the information provided by the ring's diagnostic devices. The iterative feedback system has been tested using MadX simulations. Our simulations show that a performance that matches the BPMs' accuracy can be achieved in less than 50 iterations in all cases. Details of this feedback algorithm, its efficiency and the simulations are discussed.

Delivery of high charge electron bunches into the main loop of an ERL (energy recovery linac) while preserving the emittance is challenging. This is because at the typical injection momentum, space charge forces still have a significant effect on the beam dynamics. In this work we consider the design of the merger for PERLE, an ERL test facility to be based at IJCLab in France. Previous simulations have shown that the baseline DC gun based injector can achieve the required emittance at the booster linac exit. The quality of the 500 pC bunches must then be preserved with space charge through the merger at total beam energy of 7 MeV keeping the emittance below 6 mm⋅mrad. The beam dynamics in the merger were simulated using the code OPAL and optimised using a genetic algorithm. Three possible merger schemes were investigated. The goal of the optimisation was to minimise the emittance growth while also achieving the required Twiss parameters to match onto the spreader at the main linac exit. A three dipole solution is then examined in more detail. PERLE AND THE PERLE INJECTOR PERLE is a proposed 500 MeV 3 turn ERL which is foreseen to be hosted at IJCLab in Orsay [1]. The injector for PERLE must be capable of delivering 500 pC bunches, with a RMS bunch length of 3 mm, an emittance of less than 6 mm⋅mrad, at a repetition rate of 40.1 MHz to give an average current of 20 mA. Table 1 shows the requirements on the beam at the exit of the main linac after the first pass. To achieve this low emittance with high average current a DC gun based injector will be used. This injector will consist of a 350 kV photocathode electron gun, a pair of solenoids for transverse beam size control and emittance compensation, a 801.58 MHz buncher cavity, a booster linac consisting of four single cell 801.58 MHz SRF cavities and a merger to transport the beam into the main ERL loop. The Twiss matching to the optics of the main ERL loop is also done in the merger. The layout of the injector with a possible merger example can be seen in Fig. 1. After the injection line is the main linac which consists of four five cell 801.58 MHz SRF cavities. ∗ Work at JLAB was supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contracts DE-AC05-06OR23177 and DE-SC0012704. † B.R.Hounsell@Liverpool.ac.uk Table 1: PERLE Merger Specification

The Large Hadron electron Collider (LHeC) is designed to move the field of deep inelastic scattering (DIS) to the energy and intensity frontier of particle physics. Exploiting energy recovery technology, it collides a novel, intense electron beam with a proton or ion beam from the High Luminosity--Large Hadron Collider (HL-LHC). The accelerator and interaction region are designed for concurrent electron-proton and proton-proton operation. This report represents an update of the Conceptual Design Report (CDR) of the LHeC, published in 2012. It comprises new results on parton structure of the proton and heavier nuclei, QCD dynamics, electroweak and top-quark physics. It is shown how the LHeC will open a new chapter of nuclear particle physics in extending the accessible kinematic range in lepton-nucleus scattering by several orders of magnitude. Due to enhanced luminosity, large energy and the cleanliness of the hadronic final states, the LHeC has a strong Higgs physics programme and its own discovery potential for new physics. Building on the 2012 CDR, the report represents a detailed updated design of the energy recovery electron linac (ERL) including new lattice, magnet, superconducting radio frequency technology and further components. Challenges of energy recovery are described and the lower energy, high current, 3-turn ERL facility, PERLE at Orsay, is presented which uses the LHeC characteristics serving as a development facility for the design and operation of the LHeC. An updated detector design is presented corresponding to the acceptance, resolution and calibration goals which arise from the Higgs and parton density function physics programmes. The paper also presents novel results on the Future Circular Collider in electron-hadron mode, FCC-eh, which utilises the same ERL technology to further extend the reach of DIS to even higher centre-of-mass energies.

We report on studies of the loss maps for particles travelling from the end of the ThomX's linac along the transfer line to the end of the ring first turn in preparation of the machine commissioning. ThomX is a 50-MeV-electron accelerator prototype which will use Compton backscattering to generate a high flux of hard X-rays. The accelerator tracking code MadX is used to simulate electrons' propagation and compute losses. These maps may be projected at any localisation along the bunch path or plotted along the bunch path. This information is particularly relevant at the locations of the monitoring devices (screens, position monitors,...) where loss predictions will be compared with measurements.

ThomX is a new generation Compact Compton Source. It is currently commissioned by and at the IJCLab (Laboratoire de physique des 2 infinis - Irène Joliot-Curie (UMR9012)) at Orsay. The first beam is expected at the begining of 2021. The aim of ThomX is to demonstrate the characteristics of an intense and Compact (lab-size) X-ray source based on Compton Scattering. The performances are mostly driven by the laser optical system which is above the state of the art of stored laser power. Proof of principle of various X-ray techniques will be performed thanks to the versatile ThomX beamline. Firstly, this article presents the machine description. Secondly, the issues and limits of the laser system are discussed. Then, the ThomX beamline is described and the machine status conclude the ThomX presentation. Finally, the expected performances for the next years and the possible experiments that can be made with this new machine are detailed.