F. Marteau

Tools for Multipoles Magnetic Metrology at SOLEIL

SOLEIL Synchrotron is a set of 3 electron accelerators (LINAC, booster and storage ring). The 354 m circumference storage ring is dedicated to synchrotron radiation for fundamental and applied physics research. The most sensitive components of the storage ring are quadrupoles therefore manufacturing requirements are very strict. To check magnetic properties of the magnets (harmonics, magnetic axis position, magnetic tilt angle), it was necessary to measure entities at a lower level than the specifications required by the beam dynamics. Moreover measurements were to be durable during approximately six months as there were 160 quadrupoles to characterize and few tens of sextupoles to check. In this paper, we describe how was thought and optimized the SOLEIL bench and the way taken to avoid effects of manufacturing errors of the bench

Development of cryogenic undulators with PrFeB magnets at SOLEIL

Short period high field undulators are of interest for X-ray brilliance enhancement in synchrotron radiation applications and for compact Free Electron Lasers. Cryogenic in-vacuum undulators [1] are one of the possible solutions. At SOLEIL, PrFeB magnets were directly chosen, even if still under development at that time. Indeed, they enable to avoid the spin transition reorientation phenomenon which occurs with NdFeB magnets [2] and the magnets can be cooled down directly at 77 K. The first selected grade CR53 from Hitachi presents a remanence of 1.35 T at 293 K and 1.57 T at 77 K, with a coercivity of 1355 kA/m at 293 K and 6000 kA/m at 77 K. A 2 m long cryogenic undulator of period 18 mm was first built in-house, with a specific Hall probe bench directly installed in the final vacuum chamber. This first cryogenic undulator has been in operation on the storage ring for 4 years [3]. A second U18 cryo-ready undulator using a slightly different magnet grade with a higher coercivity and modules with magnets ...

Control of laser plasma accelerated electrons for light sources

With gigaelectron-volts per centimetre energy gains and femtosecond electron beams, laser wakefield acceleration (LWFA) is a promising candidate for applications, such as ultrafast electron diffraction, multistaged colliders and radiation sources (betatron, compton, undulator, free electron laser). However, for some of these applications, the beam performance, for example, energy spread, divergence and shot-to-shot fluctuations, need a drastic improvement. Here, we show that, using a dedicated transport line, we can mitigate these initial weaknesses. We demonstrate that we can manipulate the beam longitudinal and transverse phase-space of the presently available LWFA beams. Indeed, we separately correct orbit mis-steerings and minimise dispersion thanks to specially designed variable strength quadrupoles, and select the useful energy range passing through a slit in a magnetic chicane. Therefore, this matched electron beam leads to the successful observation of undulator synchrotron radiation after an 8 m transport path. These results pave the way to applications demanding in terms of beam quality.Electron beam quality in accelerators is crucial for light source application. Here the authors demonstrate beam conditioning of laser plasma electrons thanks to a specific transport line enabling the control of divergence, energy, steering and dispersion and the application to observe undulator radiation.

Description of an Electromagnetic/Permanent Magnet Helical Undulator for Fast Polarization Switching

A new Electromagnetic/Permanent Magnets Helical Undulator (EMPHU), with a 65 mm magnetic period is under construction at SOLEIL for providing a rapid switching at 5 Hz of the photon polarization required to perform dichroism experiments. The vertical field is produced by coils fed by a fast switching power supply, with a maximum current of 350 A and a polarity switching time shorter than 100 ms. The coils consist of copper sheets shaped by water jet cutting. 25 layers of copper are stacked together. The current flows in 16 layers and nine of them are cooled with thermal drain to a water piping. The current-regulated power supply, in-house developed, should be able to operate in the 4 quadrant with a 50 ppm current resolution over the full scale. It is complemented by eight power supplies for the correction coils required to provide dynamics correction of the field integrals. The horizontal field is generated by NdFeB permanent magnets. The designed vertical and horizontal first harmonic field values in the helical configuration reach 0.24 T at the minimum 14.7 mm gap. The magnetic design, the magnetic measurements (DC and AC) and the correction schemes are described.

Electron Transport on COXINEL Beam Line

COXINEL experiment aims at demonstrating free electron laser (FEL) amplification with a laser plasma accelerator (LPA). For COXINEL, a dedicated 8 m transport line has been designed and prepared at SOLEIL. We present here LPA beam transport results around 180 MeV through this line. Different electron beam optics were applied.

Mechanical Engineering Solutions for COXINEL Project

COXINEL (COherent Xray source INferred from Electrons accelerated by Laser) is a European Research Council (ERC) advance grant aims at demonstrating Free Electron Laser amplification at 200 nm with 180 MeV electrons generated by laser plasma acceleration. A special electron beam transfer line with adequate diagnostics has been designed for this project. Strong-focusing variable-field permanent magnet quadrupoles, energy de-mixing chicane and a set of conventional quadrupoles condition the electron beam before its entrance to an In-Vacuum U20 undulator. This presentation describes some of the features incorporated into the design of the magnets, girders, vacuum vessels and diagnostic equipment for this experimental machine. Progress on the equipment preparation and installation is presented as well.

Experiment preparation towards a demonstration of laser plasma based free electron laser amplification

One direction towards compact Free Electron Laser is to replace the conventional linac by a laser plasma driven beam, provided proper electron beam manipulation to handle the large values of the energy spread and of the divergence. Applying seeding techniques enable also to reduce the required undulator length. The rapidly developing LWFA are already able to generate synchrotron radiation. With an electron divergence of typically 1 mrad and an energy spread of the order of 1 % (or few), an adequate beam manipulation through the transport to the undulator is needed for FEL amplification. Electron beam transfer follows different steps with strong focusing variable strength permanent magnet quadrupoles, an energy demixing chicane with conventional dipoles, a second set of quadrupoles for further dedicated focusing in the undulator. A test experiment for the demonstration of FEL amplification with a LWFA is under preparation and progress on the equipment preparation and expected performance are described.

W164: A WIGGLER DEDICATED TO THE PUMA BEAMLINE AND THE FEMTOSLICING PROJECT AT SOLEIL

An out-vacuum wiggler, W164, was designed, built and installed on the SOLEIL storage ring with the double objective to produce high energy photons for the PUMA beamline (10 keV to 70 keV) and to be used as a modulator for the FEMTOSLICING project [1]. The insertion device requires simultaneously reaching high critical energy of photons (above 10 keV) and low resonant energy (1.55 eV). The wiggler is composed of 20 periods of 164.4 mm made of NdFeB magnets and Vanadium Permendur poles. The maximum total field reaches 1.85 T at the minimum gap and 1.66 T at the FEMTOSLICING operation gap. The size of the poles, the carriage and the girders were optimized to minimize the deformation resulting from the magnetic forces (8 tons at minimum gap).