(Discharge Produced Plasma) In DPP, electrical energy is used to ionize a gas (or mixture of gases), heating it to produce a high density plasma. Depending on the gas(es) used, their partial pressures, the amount and frequency of the power input, light in the EUV range (i.e., 13.5 nm) can be produced. This process is highly efficient since electrical energy is directly converted into plasma energy.