ARC-EN-CIEL proposes a panoply of light sources with tuneable, adjustable polarisation, coherent femtosecond light pulses covering from UV to soft X ray for the scientific community Based on low emittance photo-injector, the electron beam is accelerated in a superconducting linear accelerator operating at high repetition rate up to 1 GeV, and feeds undulators for seeded FEL sources. FEL sources are based High Gain Harmonic Generation radiation and their Non Linear Harmonics seeded with High order Harmonics generated in Gas. A recent demonstration on SCSS prototype accelerator in Japan performed jointly validated experimentally this concept. LEL1 at 1 GeV covers the 200-1.5 nm range, with adjustable polarisation and pulse of 20-50 fs. LEL2 covers the 10-0.5 nm range in planar polarisation. Additional Energy Recovery Loops at 1 GeV and 2 GeV where undulators emit conventional synchrotron radiation above 10 keV from short period in vacuum undulators and Soft-X ray using an variable polarisation undulator. On the 1 GeV loop will be installed LEL3, an FEL oscillator in the 40-8 nm range, with high average power. A beam from the 2 GeV loop can be further accelerated to 3 GeV, for feeding LEL4, seeded with High Harmonics in Gas, for providing coherent radiation in the 2-0.2 nm range. In addition, THz radiation from the magnets of the compression chicanes will be provided.
Phase 1
Phase 1 uses a 1 kHz high charge, short bunch electrons beam reaching an energy of 220 MeV with 3 cryomodules and a first bunch compressor delivered by a modified Zeuthen RF gun illuminated by a Ti:Sa laser. LEL1 is based on a FEL seeded with HHG with an APPLE-II type undulator as a radiator for adjustable polarisation radiation down to 30 nm.
Phase 1' reaches 800 MeV with an additional bunch compressor and five cryomodules and fits in the tunnel of the ALS (Accelerateur Linéaire de Saclay) allowing LEL1 radiation to be extended to shorter wavelengths for users applications.
Phase 2
Phase 2 comports two additional cryomodules on the Linac leading to 1 GeV, the FEL source “LEL2” will be installed, allowing stronger radiation to be achieved in the 1 nm range.
Phase 3
Phase 3 comports the installation of an additional high average current gun (AES/JLab type), two ERL loops at 1 and 2 GeV will be added. On the 1 GeV loop is planned LEL3 and FEL oscillator taking advantage of the mirror development for lithography, and an APPLE-II for subpicosecond radiation synchrotron radiation. On the 2 GeV loop, 6 in vacuum U20 (period of 20 mm) will be installed for hard X ray spontaneous emission. When the 2 GeV beams is not energy recovered but once again accelerated up to 3 GeV, it is sent to “LEL4”, an FEL seeded with HHG and using cryogenic undulators. THz radiation is also produced in the bending magnets of the compression chicanes and of the arcs.
