Arizona State University, Tempe, USA
UCLA, Los Angeles, USA
SLAC, Menlo Park, California, USA
We report on experiments in nanopatterning electron beams from a photoinjector as a first step toward a compact XFEL (CXFEL). The nanopatterning is produced by Bragg diffraction of relativistic electron beams through a patterned Si crystal consisting of alternating thick and thin strips to produce nanometer-scale electron density modulations. Multi-slice simulations show that the target can be oriented for a two-beam condition where nearly 80% of the elastically scattered electron beam is diffracted into the 220 Bragg peak. An experiment at the two-beam condition measurement has been carried out at the SLAC UED facility showing this effect with 2.26 MeV electrons. We successfully proved a large portion of the main beam is diffracted into 220 spot by tuning the orientation of the sample. Future plans at UCLA are to observe the nanopatterned beam, and to investigate various grating periods, crystal thicknesses, and sample orientations to maximize the contrast in the pattern and explore tuning the period of the modulation. The SLAC measurement results will be presented along with design of the UCLA experiments.
BNL, Upton, Long Island, New York, USA
SBU, Stony Brook, New York, USA
In this paper, we present results of our studies in amplification of density modulation induced by co-propagating ions in the FEL section of a Coherent Electron Cooling system, as well its interaction with hadrons. We present a set of requirements for electron beam parameters to satisfy for necessary amplification of the density modulation, while preventing loss of the phase information and saturation.
DESY, Hamburg, Germany
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
XFEL. EU, Schenefeld, Germany
DESY, Hamburg, Germany
LANL, Los Alamos, New Mexico, USA
PSI, Villigen PSI, Switzerland
EPFL, Lausanne, Switzerland
University of Erlangen-Nuremberg, Erlangen, Germany
Friedrich-Alexander Universität Erlangen-Nuernberg, University Erlangen-Nuernberg LFTE, Erlangen, Germany
The Accelerator on a Chip International Program (ACHIP) is an international collaboration, funded by the Gordon and Betty Moore Foundation, whose goal is to demonstrate that a laser-driven accelerator on a chip can be integrated to fully build an accelerator based on dielectric structures. PSI will provide access to the high brightness electron beam of SwissFEL to test structures, approaches and methods towards achieving the final goal of the project. In this contribution, we will describe the two interaction chambers installed on SwissFEL to perform the proof-of-principle experiments. In particular, we will present the positioning system for the samples, the magnets needed to focus the beam to sub-micrometer dimensions and the diagnostics to measure beam properties at the interaction point.
PAL, Pohang, Republic of Korea
ANL, Argonne, Illinois, USA
Preparations to upgrade the single EEX beamline at the Argonne Wakefield Accelerator (AWA) facility to a double EEX beamline are underway. The single EEX beamline recently demonstrated exchange-based longitudinal bunch shaping (LBS) which has numerous applications including high-energy physics linear colliders, x-ray FELs, and intense radiation sources. The exchange-based method can generate arbitrary LBS in the ideal case but has limitations in the real case. The double EEX beamline was proposed as a means to overcome the limitations of single EEX due to transverse jitter and large horizontal emittance. In this paper, we present the current status of beamline design and installation and simulation results for the planned experiments: collinear wakefield acceleration with tailored beams and tunable bunch compression without the double-horn feature.
IHEP, Beijing, People's Republic of China
USTC/NSRL, Hefei, Anhui, People's Republic of China
SLAC, Menlo Park, California, USA
Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA
University of Texas at Arlington, Arlington, USA
POSTECH, Pohang, Kyungbuk, Republic of Korea
Short-wavelength high-gain free-electron lasers (FELs) are now well established as a source of ultra-fast, ultra-brightness, longitudinally partial coherent light. Since coherence is one of the fundamental properties of light source, so continual effort is devoted to high-gain free-electron laser coherence measurements. In this work, we propose a possible approach, employing a phase shifter to induce electron beam delay to measure the temporal coherence length. Simple analysis, numerical simulation and preliminary experimental results are presented. This approach can be robust and independent of frequency.
SLAC, Menlo Park, California, USA
PAL, Pohang, Kyungbuk, Republic of Korea
University of Texas at Arlington, Arlington, USA
High-brightness XFEL is demanding for many users, in particular for certain types of imaging applications. Seeded FELs including self-seeding XFELs were successfully demonstrated. Alternative approaches by enhancing slippage between the x-ray pulse and the electron bunch were also demonstrated. This class of Slippage-enhanced SASE (SeSASE) schemes can be unique for FEL spectral range between 1.5 keV to 4 keV where neither grating-based soft x-ray self-seeding nor crystal-based hard x-ray self-seeding can easily access. SeSASE can provide high-brightness XFEL for high repetition rate machines not suffering from heat load on the crystal monochromator. We report start-to-end simulation results for LCLS-II project and PAL-XFEL project with study on tolerance. Performance comparison between SaSASE FEL and self-seeding FEL in the overlapping frequency range is also presented.
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
Cockcroft Institute, Warrington, Cheshire, United Kingdom
University of Glasgow, Glasgow, Scotland, United Kingdom
SOLEIL, Gif-sur-Yvette, France
PhLAM/CERCLA, Villeneuve d'Ascq Cedex, France
LOA, Palaiseau, France
UNAM, Cuernavaca, Morelos, Mexico
Devi Ahilya University, Indore, India
A 14 mm - 10 period NbTi superconducting undulator for the next generation of Free Electron Laser has been stud- ied. The optimum electromagnetic pre-design was carried out using RADIA, an extension module of the commercial software Mathematica. For this pre-design, a variable gap was considered. Additionally, a thermo-mechanical study of one eighth of the superconducting undulator was conducted. This study utilized a thermal and mechanical contact model between the pancake coils and the carbon steel core. This coupled model allowed estimating the minimum pre-loading of the coil. This pre-loading ensures that the coil would remain stuck to its pole during cooling. Numerical results are presented for both studies.
* M. Gehlot et al., Nucl. Inst. and Meth. in Phys. Res., Sec. A, Vol. 846, p. 13-17, 2017.
** B.J.A. Shepherd et al., Proceedings of IPAC2014, WEPRI095, 2014.
*** J. Grimmer, R. Kmak, PAC 2005.
Uppsala University, Uppsala, Sweden
Uppsala University, Department of Engineering Sciences, Uppsala, Sweden
UEF, Joensuu, Finland
Dielectric laser acceleration (DLA) is the technique utilizing strong electric fields in lasers to accelerate electrons in the proximity of nanoscaled dielectric gratings. The concept was recently demonstrated in experimental studies. Here we describe the experimental DLA investigation setup design including laser system and scanning electron microscope (SEM). We also present the grating manufacturing methods as well investigations into vacuum breakdowns occurring at RF accelerating structures.
Waseda University, Tokyo, Japan
Center for Optical Research and Education, Utsunomiya University, Utsunomiya, Japan
RISE, Tokyo, Japan
Waseda University, Waseda Institute for Advanced Study, Tokyo, Japan
KEK, Ibaraki, Japan
Laser-Compton Scattering X-ray (LCS-X) sources have been expected as compact and powerful sources, beyond X-ray tubes. They will enable laboratories and companies, opening new X-ray science. It is well known that luminosity depends on the collision angle of a laser and electron beam. Head-on collision is ideal in the point of maximizing the luminosity, though it is difficult to create such a system especially with an optical enhancement cavity for a laser. In collider experiments, however, crab crossing is a promising way to increase the luminosity. We are planning to apply crab crossing to LCS to achieve a higher luminosity leading to a more intense X-ray source. Electron beams will be tilted to half of the collision angle using an RF-deflector. Although crab crossing in Laser-Compton scattering has been already proposed, it has not been demonstrated yet anywhere.* The goal of this study is to experimentally prove the luminosity increase by adopting crab crossing. In this conference, we will report about our compact accelerator system at Waseda University, laser system favorable for crab crossing LCS, and expected results of crab crossing LCS.
* V. Alessandro, et al., "Luminosity optimization schemes in Compton experiments based on Fabry-Perot optical resonators." Physical Review Special Topics-Accelerators and Beams 14.3 (2011): 031001.
Waseda University, Waseda Institute for Advanced Study, Tokyo, Japan
Waseda University, Tokyo, Japan
AIST, Tsukuba, Ibaraki, Japan
KEK, Ibaraki, Japan
We have been studying a coherent Cherenkov radiation by using tilted electron bunches. Bunch tilting can enhance the radiation power about 10 times due to the wavefront matching of radiations. Recently, we investigated that this technique can produce high peak power THz pulses with sufficient pulse energy. Resulting pulse energy was more than 30 nJ/pulse and peak power was about 10 kW. Introducing the oscillator cavity with two concave mirrors, it would be possible to achieve lasing using tilted electron bunches. In the calculation, 1 uJ/micro-pulse and 100 uJ/macro-pulse broadband THz pulses are expected to be achieved, which are powerful THz sources compared with the existing THz FELs. In this conference, we will report the experimental results of coherent Cherenkov radiation, calculated results toward lasing and future prospectives.
FRA01
SLAC, Menlo Park, California, USA
University of Connecticut, Storrs, Connecticut, USA
UCLA, Los Angeles, USA
The novel fresh-slice XFEL scheme grants control on the temporal slice of the electron bunch lasing in each undulator section. The technique relies on a time-dependent electron bunch trajectory impressed by the transverse wakefield of a corrugated structure and subsequent orbit manipulation in the undulator section. Fully saturated double pulses are produced in two different undulator sections. The wavelength of each pulse is controlled by the undulator magnetic strength and the delay between the pulses can be scanned from a few femtosecond advance of the pulse generated on the bunch head in the second section to a picosecond delay provided by the magnetic chicane. Three-color saturated pulses are demonstrated by using three undulator sections and the polarization of the pulse generated in the last section can be controlled by the variable polarization Delta undulator. In this work we also show the early results for the first multi-stage amplification scheme, producing ultra-short single-pulses with a 100-GW power level in the soft X-rays. The multi-stage amplification is also demonstrated to improve the performance in power and pulse duration control for the two-color FEL scheme.
FRA02
PSI, Villigen PSI, Switzerland
EPFL, Lausanne, Switzerland
FRA03
RadiaBeam, Santa Monica, California, USA
UCLA, Los Angeles, California, USA
Fermilab, Batavia, Illinois, USA
RadiaSoft LLC, Boulder, Colorado, USA
ANL, Argonne, Illinois, USA
Free Electron Lasers have achieved prominence as the X-ray light source technology for research applications, but their industrial potential remains largely unexplored, even though FELs could reach wavelength coverage and powers unattainable by active media sources. In response to this challenge, we developed the TESSA (tapering-enhanced stimulated superradiant amplifier) FEL scheme, which enables as much as 50% single-pass beam-to-light energy-conversion efficiency. With strongly tapered helical undulator and stimulated rapid deceleration, TESSA offers an order-of-magnitude improvement over all existing high-efficiency FEL paradigms and beyond the limit of many conventional lasers. The proof-of-concept was recently demonstrated by UCLA in a pilot experiment at 10-μm wavelength, where 35% deceleration efficiency has been achieved in a 50-cm wiggler. The next steps discussed herein, include: the ongoing development of the TESSA high gain amplifier at UV wavelength; a planned transition to SCRF linac driven TESSA oscillator to reach high average powers; and eventually a development of the EUV TESSA oscillator for industrial applications in the semiconductor industry.
FRA04
SINAP, Shanghai, People's Republic of China
SLAC, Menlo Park, California, USA
FRA05
DESY, Hamburg, Germany
The Horizon 2020 Project EuPRAXIA (European Plasma Research Accelerator with eXcellence In Applications) aims at producing a design report of a highly compact and cost-effective European facility with a 5 GeV electron beam using plasma as the acceleration medium. The accelerator facility will be based on a laser and/or a beam-driven plasma acceleration approach and will have user areas for FEL user experiments as well as high-energy physics (HEP) detector tests. Other applications such as a compact X-ray source for medical imaging will also be included. EuPRAXIA started in November 2015 and will deliver the design report in October 2019. The contribution will introduce the work up to date, the underlying physics of compact plasma accelerators, and its 16 European partner laboratories and further 22 international associated partners.