Beam optics simulation for Delhi light source (phase-I)

Beam optics simulations have been performed for phase I of Delhi Light Source (DLS), which will primarily consist of a normal conducting 2.6 cell photocathode RF gun followed by a solenoid magnet and an undulator. The facility is designed to generate THz radiation in the range of ∼ 0.18 – 3.0 THz, using micro-bunched electron beams with time width of a few hundreds of femto-second and energies in the range of 4 to 8.2 MeV. The intensity of the THz radiation will be enhanced by producing more microbunches (up to 16) with their separation made equal to the wavelength of the radiation. A study is performed using the General Particle Tracer (GPT) code to simulate the beam optics. Various parameters, viz. accelerating phase, laser spot size, charge of the electron micro bunch, focussing fields of solenoid and quadrupole, separation between the micro-bunches in a micro-bunch train, etc. have been optimized to maximize the bunching factor of the macro-bunch when it is inside the undulator. Maximisation of the bunching factor is required to enhance the coherence and to maximise the intensity of the radiation. Beam matching through the undulator along Y-axis was also optimized in the simulations in order to make the electrons see similar undulator fields. The paper presents results of the beam optics simulations, starting from the photocathode installed inside the RF cavity up to the exit of the undulator. (author)