Nicolas Delerue

Single shot transverse emittance measurement of multi-MeV electron beams using a long pepper-pot

Abstract We present a pepper-pot design in which we address the problem of penetration by high energy particle, deriving analytical expressions and performing GEANT4 simulations for the estimation of the error introduced by a long (thick) pepper-pot. We also show that a careful design allows to measure the emittance of electron beam of several hundreds MeV and beyond.

ATF extraction line laser-wire system

The ATF extraction line laser-wire (LW) aims to achieve a micron-scale laser spot size and to verify that micron- scale beam profile measurements can be performed at the International linear collider beam delivery system. Recent upgrades to the LW system are presented together with recent results including the first use of the LW as a beam diagnostic tool.

Beam Profile Measurements and Simulations of the Petra Laser-Wire

The Laser-wire will be an essential diagnostic tool at the International Linear Collider. It uses a finely focussed laser beam to measure the transverse profile of electron bunches by detecting the Compton-scattered photons (or degraded electrons) downstream of where the laser beam intersects the electron beam. Such a system has been installed at the PETRA storage ring at DESY, which uses a piezo-driven mirror to scan the laser-light across the electron beam. Latest results of experimental data taking are presented and compared to detailed simulations using the Geant4 based program BDSIM.

Single shot transverse emittance measurement from OTR screens in a drift transport section

Single shot transverse emittance measurement is essential to assess the beam quality and performance of new generation light sources such as linac based X-ray Free Electron Lasers (FELs) or laser plasma wakefield accelerators (LPWA). To this end, we have developed a single shot transverse emittance measurement using at least 3 screens inserted in the beam at the same time, measuring the beam size at different positions in a drift space in one single shot. In this paper, we firstly present the theoretical aspects to perform the measurement. We secondly show experimental results obtained at Diamond for a 3 GeV electron beam in the transfer line from the Booster to the Storage Ring, using this thin OTR screens method. Finally, we discuss the results showing the strength of the measurement in comparison with more standard and established emittance measurement, like the quadrupole scan method.

Ultrafast amplified fiber laser for laser-wire measurements in particle accelerators

We report on the generation of sub-500fs pulses of 3.5μJ energy at 6.49 MHz repetition rate and 1037 nm based on the amplification of an Ytterbium femtosecond oscillator, frequency locked to an external source in a double stage fiber chirped pulse amplification system. The system is operated in a burst mode where bunches of pulses of 900μs duration are amplified at 5Hz repetition rate. Such a system is dedicated to the measurement the spatial distribution of electron beam in future large scale ultra-high brightness particle collider.

Proposal of the Next Incarnation of Accelerator Test Facility at KEK for the International Linear Collider

To reach design luminosity, the International Linear Collider (ILC) must be able to create and reliably maintain nanometer size beams. The ATF damping ring is the unique facility where ILC emittances are possible. In this paper we present and evaluate the proposal to create a final focus facility at the ATF which, using compact final focus optics and an ILC-like bunch train, would be capable of achieving 37 nm beam size. Such a facility would enable the development of beam diagnostics and tuning methods, as well as the training of young accelerator physicists.

Beam offset due to beam-beam interactions at a warm linear collider

At a warm linear collider the short time interval at which bunches will pass near each other in the interaction region may lead to significant alteration of the bunches positions. In this paper we quantify the intensity of this effect and show that it can be addressed by a fast intra-pulse feedback system.

Simulations of the Acceleration of Externally Injected Electrons in a Plasma Excited in the Linear Regime

We have investigated numerically the coupling between a 10 \si{MeV} electron bunch of high charge (§I{> 100}{pc}) with a laser generated accelerating plasma wave. Our results show that a high efficiency coupling can be achieved using a §I{50}{TW}, §I{100}{μ \meter} wide laser beam, yielding accelerating field above §I{1}{ GV/m}. We propose an experiment where these predictions could be tested.

Comparison of the Smith-purcell Radiation Yield for Different Models

Smith-Purcell radiation is used in several applications including the measurement of the longitudinal profile of electron bunches. A correct reconstruction of such profile requires a good understanding of the underlying model. We have compared the leading models of Smith-Purcell radiation and shown that they are in agreement within the experimental errors.

Study of Short Bunches at the Free Electron Laser CLIO

CLIO is a Free Electron Laser based on a thermionic electron gun. In its normal operating mode it delivers electron 8 pulses but studies are ongoing to shorten the pulses to about 1 ps. We report on simulations showing how the pulse can be shortened and the expected signal yield from several bunch length diagnostics (Coherent Transition Radiation, Coherent Smith Purcell Radiation).