FERMI@Elettra is a new 4-generation light source based on a single pass Free Electron Laser (FEL) providing high peak-power photon pulses. It consists of a 1.5-GeV normal-conducting linac working at 50 Hz repetition rate and two chains of undulators where the photon beams are produced with a seeded laser multistage mechanism. A number of control loops, some of them working on a shot-by-shot bas...

Using the recently proposed echo-enabled harmonic generation (EEHG) free-electron laser (FEL) scheme, it is shown that operating the Shanghai deep ultraviolet FEL (SDUV-FEL) with single-stage to higher harmonics is very promising, with higher frequency up-conversion efficiency, higher harmonic selectivity and lower power requirement of the seed laser. The considerations on a proof-of-principle ...

Simple formulas for optimization of VUV and X-ray SASE FELs are presented. The FEL gain length and the optimal beta-function are explicitly expressed in terms of the electron beam and undulator parameters. The FEL saturation length is estimated taking into account quantum diffusion in the undulator. Examples of the FEL optimization are given. Parameters of a SASE FEL, operating at the Compton w...

Electron beam microbunching in both the fundamental and second harmonic in a high-gain self-amplified spontaneous emission free-electron laser (SASE FEL) was experimentally characterized using coherent transition radiation. The microbunching factors for both modes (b(1) and b(2)) approach unity, an indication of FEL saturation. These measurements are compared to the predictions of FEL simulatio...

The effect of error feedback on the accuracy of output task types such as editing task, text reconstruction task, picture cued writing task, and dictogloss task, has not been clearly explored. Following arguments concerning that the combination of both corrective feedback and output makes it difficult to determine whether their effects were in combination or alone, the purpose of the present st...

This study examined the trainability of the proprioceptive sense and explored the relationship between proprioception and motor learning. With vision blocked, human learners had to perform goal-directed wrist movements relying solely on proprioceptive/haptic cues to reach several haptically specified targets. One group received additional somatosensory movement error feedback in form of vibro-t...

Reliable detection of error from electroencephalography (EEG) signals as feedback while performing a discrete target selection task across sessions and subjects has a huge scope in real-time rehabilitative application of Brain-computer Interfacing (BCI). Error Related Potentials (ErrP) are EEG signals which occur when the participant observes an erroneous feedback from the system. ErrP holds si...

The quantum operation mode in the X-ray Compton free-electron laser (FEL) is presented. This FEL mode emerges when the quantum emission exceeds the electron beam energy spread and FEL homogeneous linewidth, determined by the optical undulator length. Such a FEL becomes a two-level quantum oscillator with a completely inverted active medium. In the nonlinear interaction regime, inversion can be ...