The isobaric and isochoric models of inertial confinement fusion (ICF) are compared in hot spot concept. Heating and cooling mechanisms of fuel are theoretically investigated. Some corrections are suggested to improve the Bremsstrahlung emission calculation at ultra-relativistic regime and super high temperature plasma situation. An admissible region of values is determined which satisfy hot spot spark-ignition condition to start a self-sustaining fusion burn. An optimized point of this region is specified to achieve a maximum fuel gain. The density and radius of this optimum point are determined applying a hydrodynamic model. The results show that a fuel gain maximum will be achieved with the required minimum laser energy supply through the optimization process.
