These pulses are used to switch the MOSFET on, which supplies an amplified pulse of gate current to SCR through the pulse transformer. The Doide D2 is used to prevent negative gate current due to the transformer magnetizing current when the MOSFET turns off. The diode D1 is used to provide path for the transformer magnetizing current so that the energy in the magnetic core gets dissapated in R2. Paralleled C1 produces the waveform shaping.
I am not certain what specification of components used. How can I know?