Editing Marx generator (section)

==Optimization==
[[Image:coaxial Marx generator.png|thumb|upright=1.25|To deliver 5 ns rise time pulses, the Marx generator is often built into a [[coaxial]] [[wave guide]]. The [[spark gap]]s are placed as close as possible together for maximum UV light exchange for minimum jitter. DC HV comes from underneath, pulsed HV leaves at the top into the coaxial line. The double line of spheres in the middle are the spark gaps, all other spheres are to avoid [[corona discharge]]. Blue=[[water capacitor]]. Grey=solid metal. Black= thin wire. The outer conductor also functions as a vessel, so that the gas and the pressure can be optimized.]]

Proper performance depends upon [[capacitor]] selection and the timing of the discharge. Switching times can be improved by doping of the [[electrode]]s with [[radioactive]] [[isotopes]] [[caesium]] 137 or [[nickel]] 63, and by orienting the spark gaps so that [[ultraviolet]] light from a firing spark gap switch illuminates the remaining open spark gaps.<ref>E. Kuffel, W. S. Zaengl, J. Kuffel ''High voltage engineering: fundamentals'', Newnes, 2000 {{ISBN|0-7506-3634-3}}, pages 63, 70</ref> Insulation of the high voltages produced is often accomplished by immersing the Marx generator in [[transformer oil]] or a high pressure [[dielectric gas]] such as [[SF6|sulfur hexafluoride]] (SF<sub>6</sub>).

Note that the less resistance there is between the capacitor and the charging power supply, the faster it will charge. Thus, in this design, those closer to the power supply will charge quicker than those farther away. If the generator is allowed to charge long enough, all capacitors will attain the same voltage.

In the ideal case, the closing of the switch closest to the charging power supply applies a voltage 2''V'' to the second switch. This switch will then close, applying a voltage 3''V'' to the third switch. This switch will then close, resulting in a cascade down the generator that produces ''nV'' at the generator output (again, only in the ideal case).

The first switch may be allowed to spontaneously break down (sometimes called a ''self break'') during charging if the absolute timing of the output pulse is unimportant. However, it is usually intentionally triggered once all the capacitors in the Marx bank have reached full charge, either by reducing the gap distance, by pulsing an additional trigger electrode (such as a [[Trigatron]]), by ionising the air in the gap using a pulsed [[laser]], or by reducing the air pressure within the gap.

The charging resistors, Rc, need to be properly sized for both charging and discharging. They are sometimes replaced with [[inductor]]s for improved efficiency and faster charging. In many generators the resistors are made from plastic or glass tubing filled with dilute [[copper sulfate]] solution. These [[liquid resistor]]s overcome many of the problems experienced by more-conventional solid resistive materials, which have a tendency to lower their resistance over time under high voltage conditions.