Simulation and measurement of electromagnetic undulator prototype for production of THz radiation

Abstract

This research focused on magnetic field simulation and measurement of an electromagnetic undulator prototype for generation of terahertz (THz) radiation from electron beam with energy of about 10 MeV at the PBP-CMU Electron Linac Laboratory of the Plasma and Beam Physics Research Facility. This undulator prototype has 6.5 periods with a period length of 64 mm. Its magnetic field was measured by using a Hall probe with a measuring system, which its position movement can be precisely controlled with automatic computer interface. The magnetic field of end-poles was compensated by adjusting the end-pole currents. It was found that at the main-pole current of 0.76 A, the optimal end-pole currents at the entrance and exit o f the undulator were 0.27 A and 0.19 A, respectively. At these currents the undulator has the transverse good field region of 19 mm. For magnetic field simulation, the computer program RADIA was used to model the undulator prototype for the ideal design. This was done for comparing the magnetic fields from the simulation and the measurement. The magnetic field of the two cases were not the same because the constructed prototype has different gaps for different lo ngitudinal positions. However, they could give the radiation in the THz regime, which were 97.6 μm for the simulation and 96.7 ± 0.1 μm for the measurement.