Phase displacement free-electron laser

A free-electron laser (FEL) comprising:

• a. a relativistic electron beam generator;
• b. an optical cavity adapted to store a co-propagating optical beam in which an axis of a relativistic electron beam generated at least in part by the relativistic electron beam generator is aligned along an optical axis of the optical cavity;
• c. an interaction region disposed in the optical cavity, the interaction region further comprising a magnetic field generator;
• d. a phase displacement device disposed about a predetermined portion of the interaction region, and
• e. an output coupler interposed in the optical cavity to induce a predetermined value of round-trip cavity losses;
• f. wherein
• i. cavity losses at saturation are limited to a predetermined value sufficient to allow uniform deceleration of electrons along the streamlines between the separatrices;
• and
• ii. round-trip cavity losses at saturation have a magnitude sufficient to prevent development of coupled electron-optical beam instability.

A method of operating a general phase-displacement FEL oscillator, for an FEL comprising a relativistic electron beam generator, an electron beam transport system, a magnetic field generator, a phase displacement device, an optical cavity, and an output coupler, the method comprising:

• a. setting a cavity outcoupling ratio to a first predetermined value;
• b. adjusting the phase displacement device to increase the resonant energy relative to the electron beam energy by a second predetermined value;
• c. creating the electron beam;
• d. accelerating the electron beam in the relativistic electron beam generator;
• e. directing the accelerated electron beam to the interaction region by the electron beam transport system;
• f. injecting the directed electron beam into the interaction region by the electron beam transport system;
• g. setting the electron beam energy to establish the energy of the electrons provided by the electron beam generator and electron beam transport system at a third predetermined value;
• h. establishing conditions for regenerative amplification, an initial extraction of energy from the electrons in the beam, and a build-up of optical power within the optical cavity by setting the electron beam current initially to a value sufficient to insure that the small signal laser gain exceeds the sum of the optical cavity reflective, dissipative, and outcoupling losses;
• i. leaving the electron beam on for a period of time sufficient for the optical power in the cavity to grow from the small signal to the saturated regime;
• j. configurably adjusting the large signal laser gain by changing the electron beam current provided by the electron beam generator to maintain the large signal gain at a fourth predetermined value
• k. whereby laser operation at high power, efficient conversion of electron beam energy to light, and uniform deceleration of all the electrons in the electron beam are achieved simultaneously.