main amplification takes place in a series of glass amplifiers located at one end of the beamlines. Prior to "firing", the amplifiers are first optically pumped by a total of 7,680 Xenon flash lamps (the PAMs have their own smaller pumps as well). The lamps are powered by a capacitor bank which stores a total of 330 megajoules (MJ) of electrical energy. When the wavefront passes through them, the amplifiers release some of the light energy stored in them into the beam. This is not a particularly efficient process, and in order to improve the energy transfer the beams are sent though the main amplifier section four times, using an optical switch located in a mirrored cavity. In total these amplifiers boost the original 10 J provided by the PAMs to a nominal 4 MJ (1000 terawatts).