At least one method, apparatus and system for providing an extreme ultraviolet beam for processing semiconductor wafers are disclosed. A level of the EUV beam is monitored. A determination is made as to whether the level of the EUV beam is below a predetermined level. In response to determining that the level of the EUV beam is below the predetermined level, a determination is made as to whether the output of at least one of the first or second laser devices has decreased from an initial level. The output of the at least one of the first or second laser devices is increased in response to determining that the output of at least one of the first or second laser devices has decreased from an initial level.