Abstract: A laser amplifier head including plates of a laser active medium which are placed inside a housing which has an inlet port and an outlet port. A cooler includes a cooling circuit connected to the housing and suited to the circulation of a cooling liquid, a cooling duct, inside the housing, in contact with the active medium, in which the cooling liquid flows, allowing an exchange of heat between the latter and the plates, and a regulator able to regulate a temperature of the cooling liquid such that a thermo-optical coefficient dn dT of the cooling liquid satisfies the following condition: ? "\[LeftBracketingBar]" d ? n d ? T ? "\[RightBracketingBar]" < 6 ? ? 0 ? ? T * ? ? H ? ( I ) where ?T represents the difference in temperature between the cooling liquid and the plates of the active medium, ??H represents the sum of the hydraulic diameters of the cooling duct and ?0 represents the wavelength of the beam in a vacuum.

Abstract: The disclosure relates to a free-electron laser system and a method for generating a packet of relativistic electrons capable of propagating in a first propagation direction (Oz), and a device for generating an undulator beam capable of interacting with the packet of relativistic electrons. In the system, the undulator beam results from combining, at an interaction area through which the propagation direction (Oz) of the packet passes, at least two laser beams propagating in different directions and each of which has at least one non-zero component in a plane orthogonal to the propagation direction (Oz) of the packet. The disclosure also relates to a method for generating a free-electron laser beam involving trapping and guiding a packet of relativistic electrons injected into an interaction area and implementing such a free-electron laser system.

Abstract: The disclosure relates to a free-electron laser system and a method for generating a packet of relativistic electrons capable of propagating in a first propagation direction (Oz), and a device for generating an undulator beam capable of interacting with the packet of relativistic electrons. In the system, the undulator beam results from combining, at an interaction area through which the propagation direction (Oz) of the packet passes, at least two laser beams propagating in different directions and each of which has at least one non-zero component in a plane orthogonal to the propagation direction (Oz) of the packet. The disclosure also relates to a method for generating a free-electron laser beam involving trapping and guiding a packet of relativistic electrons injected into an interaction area and implementing such a free-electron laser system.