Quantum SASE FEL with a laser wiggler

Quantum effects in high-gain FELs are ruled by the quantum FEL parameter, ρ = pmcy/hkr, which is the ratio between the momentum spread at saturation and the one photon momentum recoil. It has been shown that when ∼ρ ≤ 1 the spectrum of the emitted radiation changes from the broad continuous and chaotic spectrum of the classical regime to a series of discrete and equally spaced very narrow lines, due to transitions between discrete momentum states. In this paper we show that the quantum regime can be achieved using Kilometers long magnetic wigglers or a laser wiggler. In this paper we state the scaling laws necessary to operate a Quantum SASE FEL in the Angstrom region with a laser wiggler. Specific example is given having in mind a high power Ti: Sa laser wiggler at λ= 0.8 μm, in construction at LNF-INFN Laboratories, for the SPARC/PLASMON-X project.