oscillator chamber 11 3 is reused as an amplifier chamber 21 3 on the other hand the amplifier chamber 21 2 detached from the amplifier 20 has consumed its life time corresponding to the number of laser shots lo in the oscillator 10 and has additionally consumed its life time corresponding to the number of laser shots lo in the amplifier 20 that is to say it has consumed its life time corresponding to the number of laser shots 2lo la in total this means that the deterioration of this amplifier chamber 21 2 has reached the allowable deterioration limit for the amplifier chamber 21 and hence the amplifier chamber 21 2 is overhauled or discarded in this manner every time the number of laser shots is increased by lo the chambers 11 and 21 are detached from the oscillator 10 and the amplifier 20 and a new oscillator chamber 11 x is attached to the oscillator 10 and the oscillator chamber 11 x u2212 1 detached from the oscillator 10 is attached to the amplifier 20 this means that a chamber is used through a cycle in the sequence of the oscillator 10 the amplifier 20 and overhaul it should be understood that although fig2 shows the case in which 2lo la a case in which 3lo la is also possible in the case in which 3lo la the replacement may be performed for example by a method in.