LAUSR

The Delhi Light Source (DLS), is a compact THz facility based on the principle of pre-bunched FEL, which is at the commissioning stage at Inter University Accelerator Centre (IUAC), New Delhi. The facility will produce relativistic electron beam in the energy range 4 to 8 MeV to generate THz radiation in the range 0.18–3.0 THz. To study the effect of the undulator U48 on this low energy range of the electron beam, a 3D field map of U48 was generated with the help of measured magnetic field data. Beam tracking simulations were performed with the generated field map at the minimum gap of U48. Simulations showed that the quadrupole component of the transverse field roll-off, which is the dominant component within the width of the vacuum chamber can introduce a substantial growth of the beam size in the wiggling plane and result in severe beam loss while propagating through the vacuum chamber inside the undulator. To compensate the dynamic quadrupolar field, an extended quadrupole field correction coil was implemented in the simulation by superimposing its field on the magnetic field of U48. Such a correction scheme showed a remarkable improvement to contain the beam transverse growth.