Laser heater commissioning at an externally seeded free-electron laser

Spampinati, S.; Allaria, E.; Badano, Luigi P.; Bassanese, S.; Biedron, Sandra; Castronovo, D.; Craievich, P.; Danailov, M. B.; Demidovich, Alexander; Ninno, G. De; Mitri, S. Di; Diviacco, B.; Forno, Massimo Dal; Ferrari, Eugenio; Fawley, William M.; Fröhlich, Lars; Gaio, G.; Giannessi, L.; Penco, G.; Serpico, C.; Spezzani, C.; Trovò, M.; Veronese, M.; Milton, Stephen; Svandrlik, M.

doi:10.1103/physrevstab.17.120705

Cited by 55 publications

(39 citation statements)

References 24 publications

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“…The injector linac phase was optimised for minimal energy spread-as is done in the routine procedure of linac tuning-and good agreement was found between the simulated and experimentally measured bunch properties at the exit of the injector. From this injector simulation, the bunch was then tracked using the ELEGANT code [31] up to the entrance of BC1, including the effects of linac wakefields, the laser heater, which is a tool aimed to suppress the so-called microbunching instability that otherwise develops as the bunch propagates through the accelerator [32,33], CSR and space-charge models. From this point, three particle tracking codes have been used to compare the emittance measurement results with simulation: ELEGANT, CSRTRACK [34] and a modified version of GPT which utilises the CSR model outlined above in section 3.…”

Section: Simulation Setupmentioning

confidence: 99%

Beyond the limits of 1D coherent synchrotron radiation

et al. 2018

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An understanding of collective effects is of fundamental importance for the design and optimisation of the performance of modern accelerators. In particular, the design of an accelerator with strict requirements on the beam quality, such as a free electron laser (FEL), is highly dependent on a correspondence between simulation, theory and experiments in order to correctly account for the effect of coherent synchrotron radiation (CSR), and other collective effects. A traditional approach in accelerator simulation codes is to utilise an analytic one-dimensional approximation to the CSR force. We present an extension of the 1D CSR theory in order to correctly account for the CSR force at the entrance and exit of a bending magnet. A limited range of applicability to this solution-in particular, in bunches with a large transverse spot size or offset from the nominal axis-is recognised. More recently developed codes calculate the CSR effect in dispersive regions directly from the Liénard-Wiechert potentials, albeit with approximations to improve the computational time. A new module of the General Particle Tracer code was developed for simulating the effects of CSR, and benchmarked against other codes. We experimentally demonstrate departure from the commonly used 1D CSR theory for more extreme bunch length compression scenarios at the FERMI FEL facility. Better agreement is found between experimental data and the codes which account for the transverse extent of the bunch, particularly in more extreme compression scenarios.

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Section: Simulation Setupmentioning

confidence: 99%

Beyond the limits of 1D coherent synchrotron radiation

et al. 2018

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“…Finally each UV pulse has an independent shutter and the first or second bunch can be enabled or disabled independently. Similarly, the laser heater [36] pulse, that is directly generated from the PIL pulse, has been split in order to generate two pulses interacting with both electron bunches.…”

Section: Photoinjector Setupmentioning

confidence: 99%

Two-bunch operation with ns temporal separation at the FERMI FEL facility

et al. 2018

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In the last decade, a continuous effort has been dedicated to extending the capabilities of existing freeelectron lasers (FELs) operating in the x-ray and vacuum ultraviolet regimes. In this framework, the generation of two-color (or multi-color) temporally separated FEL pulses, has paved the way to new x-ray pump and probe experiments and several two-color two-pulse schemes have been implemented at the main facilities, but with a generally limited time-separation between the pulses, from 0 to few hundreds of fs. This limitation may be overcome by generating light with two independent electron bunches, temporally separated by integral multiples of the radio-frequency period. This solution was investigated at FERMI, measurements and characterization of this two-bunch mode of operation are presented, including trajectory control, impact of longitudinal and transverse wakefields, manipulation of the longitudinal phase space and finally a demonstration of suitability of the scheme to provide extreme ultraviolet light by using both bunches.

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“…A laser heater system [34,35] has been installed after the injector [36] at 100 MeV to suppress the microbunching instability driven by the coherent synchrotron radiation in the magnetic bunch compressor and by the longitudinal space charge forces along the linac. A fine-tuning of the laser heater energy per pulse, in the range 0.5-1.0 µJ, permits us to constrain σ δ after the compression and the linac transport to less than 10 −4 [37]. Considering the typical spectral range of FEL-1 operation, this means σ δ ≈ ρ/20 with a relevant improvement in the FEL output performance [38].…”

Section: Experimental Demonstration Of the Ok Sase On The Fel-1 Linementioning

confidence: 99%

Optical Klystron Enhancement to Self Ampliﬁed Spontaneous Emission at FERMI

et al. 2017

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Abstract:The optical klystron enhancement to a self-amplified spontaneous emission free electron laser has been studied in theory and in simulations and has been experimentally demonstrated on a single-pass high-gain free electron laser, the FERMI FEL-1, in 2014. The main concept consists of two undulators separated by a dispersive section that converts the energy modulation induced in the first undulator in density modulation, enhancing the coherent harmonic generation in the first part of the second undulator. This scheme could be replicated in a multi-stage: the bunching is enhanced after each dispersive section, consistently reducing the saturation length. We have applied the multi-stage optical klystron (OK) scheme on the FEL-2 line at FERMI, whose layout includes three dispersive sections. Optimizing the strength of the dispersions allowed a significant increase of the self-amplified spontaneous emission (SASE) intensity in comparison to a single-stage OK and extending to the soft-X rays the OK enhanced SASE previously demonstrated on FEL-1.

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Laser heater commissioning at an externally seeded free-electron laser

Cited by 55 publications

References 24 publications

Beyond the limits of 1D coherent synchrotron radiation

Beyond the limits of 1D coherent synchrotron radiation

Two-bunch operation with ns temporal separation at the FERMI FEL facility

Optical Klystron Enhancement to Self Ampliﬁed Spontaneous Emission at FERMI

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