Conceptual Design of a Table-top Terahertz Free-electron Laser

Conceptual Design of a Table-top Terahertz Free-electron Laser

We have designed a table-top terahertz (THz) free electron laser (FEL). The main issue of the FEL design is to decrease radiation losses at the FEL resonator except outcoupling ratio. Also reducing the number of undulator periods and total undulator length is important to increase FEL conversion efficiency and to reduce its size. The FEL consists of a magnetron-based microtron having an energy of ∼5 MeV, a strong electromagnetic helical undulator having the period of ∼25 mm, and a cylindrical waveguide-mode optical resonator. The total diameter of the microtron is approximately 60 cm and the macropulse current is more than 50 mA. The condition for low-loss and high-gain oscillator of the table-top FEL has been studied by using a 2-D FEL code. Injection scheme of the electron beam to the undulator was optimized by calculating beam trajectories with a 3-D PIC code. The average THz power is calculated to be 1 W with the tunable wavelength range from 200 μm to 500 μm. The size of the system is expected to be 1 × 2 m<SUP>2</SUP>. The FEL is expected to be used for the real-time imaging of security inspection.

We have designed a table-top terahertz (THz) free electron laser (FEL). The main issue of the FEL design is to decrease radiation losses at the FEL resonator except outcoupling ratio. Also reducing the number of undulator periods and total undulator length is important to increase FEL conversion efficiency and to reduce its size. The FEL consists of a magnetron-based microtron having an energy of ∼5 MeV, a strong electromagnetic helical undulator having the period of ∼25 mm, and a cylindrical waveguide-mode optical resonator. The total diameter of the microtron is approximately 60 cm and the macropulse current is more than 50 mA. The condition for low-loss and high-gain oscillator of the table-top FEL has been studied by using a 2-D FEL code. Injection scheme of the electron beam to the undulator was optimized by calculating beam trajectories with a 3-D PIC code. The average THz power is calculated to be 1 W with the tunable wavelength range from 200 μm to 500 μm. The size of the system is expected to be 1 × 2 m<SUP>2</SUP>. The FEL is expected to be used for the real-time imaging of security inspection.