Yesterday, we proceeded to the change of the master laser. Even if it was performing well since a few weeks, many troubles were encountered with this unit since june 2010. The laser now installed is a brand new unit acquired in last March from Innolight. (details of performances of this new laser can be seen in VIR-0215A-11).
Some troubles were encountered with the height of the beam with respect with the old laser. This solved, we tuned the ML-SL injection by optimizing amplitude of pound drever signal on BS_SL_D1R while sending a modulation on SL rampAuto (6V peak to peak are obtained for 2A on ML pumping diode and nominal value for SL diodes pumping currents).

Master laser parameters are:
Diode temperature: 22,3°
Pumping current: 2,2 A
cavity temperature: 24°
DC output power (newport power meter): 980mW

This done, we had to quite completely re-do ampli and PMC alignment.
for nominal SL power we get 52,7W at ampli output
PMC transmission is 35,4W
we then obtained 15 W at IMC output (which means we got 1W optimization by retuning alignment of both ampli and PMC)