EMP generators produce electromagnetic pulses, delivering massive amounts of energy for testing purposes. Engineers design EMP generators to store the maximum amount of energy possible via components like capacitators and release the energy in as short a period as possible, enhancing each pulse to a level that simulates the strength of a real world electromagnetic pulse.
EMP generators are used to conduct radiated immunity testing on devices, bombarding them with electromagnetic energy to test how susceptible to disruption by EMI (electromagnetic interference) the product will be in the field. Computers in particular are especially vulnerable to EMI due to the low volts necessary to disrupt circuit operation.