Do get Energy Crystals you will need to fight Elnoyles, which can be found within Esthar (I believe you win 5 from every Elnoyle (?). You can talk to this man on the walkway who will start to have a fit and then an Elnoyle will attack you. (Repeat this as much as desired). Then you can take your newly aquired Energy Crystals and refine them into Pulse Ammo.